From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; IPE's interpretation of the what the user trusts is accomplished through its policy. IPE's design is to not provide support for a single trust provider, but to support multiple providers to enable the end-user to choose the best one to seek their needs. This requires the policy to be rather flexible and modular so that trust/integrity providers, like fs-verity or dm-verity, can plug into the policy with minimal code changes. Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Refactor policy parser to make code cleaner via introducing clearly defined passes, with specific goal states. * Split up patch 03/12 into two parts: 1. parser [02/16] (this patch) 2. userspace interface [04/16] --- include/asm-generic/vmlinux.lds.h | 16 + security/ipe/Makefile | 6 + security/ipe/ipe.c | 63 ++ security/ipe/ipe.h | 4 + security/ipe/ipe_parser.h | 59 ++ security/ipe/modules.c | 109 +++ security/ipe/modules.h | 17 + security/ipe/modules/ipe_module.h | 33 + security/ipe/parsers.c | 139 ++++ security/ipe/parsers/Makefile | 12 + security/ipe/parsers/default.c | 106 +++ security/ipe/parsers/policy_header.c | 126 ++++ security/ipe/policy.c | 946 +++++++++++++++++++++++++++ security/ipe/policy.h | 97 +++ 14 files changed, 1733 insertions(+) create mode 100644 security/ipe/ipe_parser.h create mode 100644 security/ipe/modules.c create mode 100644 security/ipe/modules.h create mode 100644 security/ipe/modules/ipe_module.h create mode 100644 security/ipe/parsers.c create mode 100644 security/ipe/parsers/Makefile create mode 100644 security/ipe/parsers/default.c create mode 100644 security/ipe/parsers/policy_header.c create mode 100644 security/ipe/policy.c create mode 100644 security/ipe/policy.h diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index f2984af2b85b..91abbacbaf8d 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -278,6 +278,20 @@ #define EARLY_LSM_TABLE() #endif +#ifdef CONFIG_SECURITY_IPE +#define IPE_PARSER_TABLE() . = ALIGN(8); \ + __start_ipe_parsers = .; \ + KEEP(*(.ipe_parsers)) \ + __end_ipe_parsers = .; +#define IPE_MODULE_TABLE() . = ALIGN(8); \ + __start_ipe_modules = .; \ + KEEP(*(.ipe_modules)) \ + __end_ipe_modules = .; +#else +#define IPE_PARSER_TABLE() +#define IPE_MODULE_TABLE() +#endif + #define ___OF_TABLE(cfg, name) _OF_TABLE_##cfg(name) #define __OF_TABLE(cfg, name) ___OF_TABLE(cfg, name) #define OF_TABLE(cfg, name) __OF_TABLE(IS_ENABLED(cfg), name) @@ -436,6 +450,8 @@ KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \ __stop___tracepoints_ptrs = .; \ *(__tracepoints_strings)/* Tracepoints: strings */ \ + IPE_PARSER_TABLE() \ + IPE_MODULE_TABLE() \ } \ \ .rodata1 : AT(ADDR(.rodata1) - LOAD_OFFSET) { \ diff --git a/security/ipe/Makefile b/security/ipe/Makefile index ba3df729e252..9a97efd8a190 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -5,7 +5,13 @@ # Makefile for building the IPE module as part of the kernel tree. # +ccflags-y := -I$(srctree)/security/ipe/modules + obj-$(CONFIG_SECURITY_IPE) += \ ctx.o \ hooks.o \ ipe.o \ + modules.o \ + parsers/ \ + parsers.o \ + policy.o \ diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c index d600346702e5..b58b372327a1 100644 --- a/security/ipe/ipe.c +++ b/security/ipe/ipe.c @@ -6,6 +6,9 @@ #include "ipe.h" #include "ctx.h" #include "hooks.h" +#include "ipe_parser.h" +#include "modules/ipe_module.h" +#include "modules.h" #include <linux/fs.h> #include <linux/sched.h> @@ -24,6 +27,58 @@ static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(task_free, ipe_task_free), }; +/** + * load_parsers: Load all the parsers compiled into IPE. This needs + * to be called prior to the boot policy being loaded. + * + * Return: + * 0 - OK + * !0 - Error + */ +static int load_parsers(void) +{ + int rc = 0; + struct ipe_parser *parser; + + for (parser = __start_ipe_parsers; parser < __end_ipe_parsers; ++parser) { + rc = ipe_register_parser(parser); + if (rc) { + pr_err("failed to initialize '%s'", parser->first_token); + return rc; + } + + pr_info("initialized parser module '%s'", parser->first_token); + } + + return 0; +} + +/** + * load_modules: Load all the modules compiled into IPE. This needs + * to be called prior to the boot policy being loaded. + * + * Return: + * 0 - OK + * !0 - Error + */ +static int load_modules(void) +{ + int rc = 0; + struct ipe_module *m; + + for (m = __start_ipe_modules; m < __end_ipe_modules; ++m) { + rc = ipe_register_module(m); + if (rc) { + pr_err("failed to initialize '%s'", m->name); + return rc; + } + + pr_info("initialized module '%s'", m->name); + } + + return 0; +} + /** * ipe_init: Entry point of IPE. * @@ -41,6 +96,14 @@ static int __init ipe_init(void) { int rc = 0; + rc = load_parsers(); + if (rc) + return rc; + + rc = load_modules(); + if (rc) + return rc; + rc = ipe_init_ctx(); if (rc) return rc; diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h index 09c492b8fd03..ad16d2bebfec 100644 --- a/security/ipe/ipe.h +++ b/security/ipe/ipe.h @@ -9,11 +9,15 @@ #define pr_fmt(fmt) "IPE " fmt "\n" #include "ctx.h" +#include "ipe_parser.h" +#include "modules/ipe_module.h" #include <linux/types.h> #include <linux/sched.h> #include <linux/lsm_hooks.h> extern struct lsm_blob_sizes ipe_blobs; +extern struct ipe_parser __start_ipe_parsers[], __end_ipe_parsers[]; +extern struct ipe_module __start_ipe_modules[], __end_ipe_modules[]; #endif /* IPE_H */ diff --git a/security/ipe/ipe_parser.h b/security/ipe/ipe_parser.h new file mode 100644 index 000000000000..f7c5c11bde44 --- /dev/null +++ b/security/ipe/ipe_parser.h @@ -0,0 +1,59 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#ifndef IPE_PARSER_H +#define IPE_PARSER_H + +#include "policy.h" + +#include <linux/list.h> +#include <linux/types.h> + +/* + * Struct used to define internal parsers that effect the policy, + * but do not belong as policy modules, as they are not used to make + * decisions in the event loop, and only effect the internal workings + * of IPE. + * + * These structures are used in pass2, and policy deallocation. + */ +struct ipe_parser { + u8 version; + const char *first_token; + + int (*parse)(const struct ipe_policy_line *line, + struct ipe_parsed_policy *pol); + int (*free)(struct ipe_parsed_policy *pol); + int (*validate)(const struct ipe_parsed_policy *pol); +}; + +int ipe_parse_op(const struct ipe_policy_token *tok, + enum ipe_operation *op); + +int ipe_parse_action(const struct ipe_policy_token *tok, + enum ipe_action *action); + +/* + * Optional struct to make structured parsers easier. + */ +struct ipe_token_parser { + const char *key; + int (*parse_token)(const struct ipe_policy_token *t, + struct ipe_parsed_policy *p); +}; + +const struct ipe_parser *ipe_lookup_parser(const char *first_token); + +int ipe_for_each_parser(int (*view)(const struct ipe_parser *parser, + void *ctx), + void *ctx); + +int ipe_register_parser(struct ipe_parser *p); + +#define IPE_PARSER(parser) \ + static struct ipe_parser __ipe_parser_##parser \ + __used __section(".ipe_parsers") \ + __aligned(sizeof(unsigned long)) + +#endif /* IPE_PARSER_MODULE_H */ diff --git a/security/ipe/modules.c b/security/ipe/modules.c new file mode 100644 index 000000000000..fb100c14cce5 --- /dev/null +++ b/security/ipe/modules.c @@ -0,0 +1,109 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "modules.h" + +#include <linux/slab.h> +#include <linux/types.h> +#include <linux/rbtree.h> + +static struct rb_root module_root = RB_ROOT; + +struct module_container { + struct rb_node node; + const struct ipe_module *mod; +}; + +/** + * cmp_node: Comparator for a node in the module lookup tree. + * @n: First node to compare + * @nn: Second node to compare + * + * Return: + * <0 - @n's key is lexigraphically before @nn. + * 0 - n's key is identical to @nn + * >0 - n's key is legxigraphically after @nn + */ +static int cmp_node(struct rb_node *n, const struct rb_node *nn) +{ + const struct module_container *c1; + const struct module_container *c2; + + c1 = container_of(n, struct module_container, node); + c2 = container_of(nn, struct module_container, node); + + return strcmp(c1->mod->name, c2->mod->name); +} + +/** + * cmp_key: Comparator to find a module in the tree by key. + * @key: Supplies a pointer to a null-terminated string key + * @n: Node to compare @key against + * + * Return: + * <0 - Desired node is to the left of @n + * 0 - @n is the desired node + * >0 - Desired node is to the right of @n + */ +static int cmp_key(const void *key, const struct rb_node *n) +{ + struct module_container *mod; + + mod = container_of(n, struct module_container, node); + + return strcmp((const char *)key, mod->mod->name); +} + +/** + * ipe_lookup_module: Attempt to find a ipe_pmodule structure by @key. + * @key: The key to look for in the tree. + * + * Return: + * !NULL - OK + * NULL - No property exists under @key + */ +const struct ipe_module *ipe_lookup_module(const char *key) +{ + struct rb_node *n; + + n = rb_find(key, &module_root, cmp_key); + if (!n) + return NULL; + + return container_of(n, struct module_container, node)->mod; +} + +/** + * ipe_register_module: Register a policy module to be used in IPE's policy. + * @m: Module to register. + * + * This function allows parsers (policy constructs that represent integrations + * with other subsystems, to be leveraged in rules) to be leveraged in IPE policy. + * This must be called prior to any policies being loaded. + * + * Return: + * 0 - OK + * !0 - Error + */ +int ipe_register_module(struct ipe_module *m) +{ + struct rb_node *n = NULL; + struct module_container *c = NULL; + + c = kzalloc(sizeof(*c), GFP_KERNEL); + if (!c) + return -ENOMEM; + + c->mod = m; + + n = rb_find_add(&c->node, &module_root, cmp_node); + if (n) { + kfree(c); + return -EEXIST; + } + + return 0; +} diff --git a/security/ipe/modules.h b/security/ipe/modules.h new file mode 100644 index 000000000000..7b897bdd870b --- /dev/null +++ b/security/ipe/modules.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#ifndef IPE_MODULES_H +#define IPE_MODULES_H + +#include "ipe.h" +#include "ipe_module.h" + +#include <linux/types.h> +#include <linux/rbtree.h> + +const struct ipe_module *ipe_lookup_module(const char *key); +int ipe_register_module(struct ipe_module *m); + +#endif /* IPE_MODULES_H */ diff --git a/security/ipe/modules/ipe_module.h b/security/ipe/modules/ipe_module.h new file mode 100644 index 000000000000..397a54cbc4db --- /dev/null +++ b/security/ipe/modules/ipe_module.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#ifndef IPE_MODULE_H +#define IPE_MODULE_H + +#include <linux/types.h> + +/** + * ipe_module: definition of an extensible module for IPE properties. + * These structures are used to implement 'key=value' pairs + * in IPE policy, which will be evaluated on every IPE policy + * evaluation. + * + * Integrity mechanisms should be define as a module, and modules + * should manage their own dependencies via KConfig. @name is both + * the key half of the key=value pair in the policy, and the unique + * identifier for the module. + */ +struct ipe_module { + const char *const name; /* required */ + u16 version; /* required */ + int (*parse)(const char *valstr, void **value); /* required */ + int (*free)(void **value); /* optional */ +}; + +#define IPE_MODULE(parser) \ + static struct ipe_module __ipe_module_##parser \ + __used __section(".ipe_modules") \ + __aligned(sizeof(unsigned long)) + +#endif /* IPE_MODULE_H */ diff --git a/security/ipe/parsers.c b/security/ipe/parsers.c new file mode 100644 index 000000000000..80dc4704ae40 --- /dev/null +++ b/security/ipe/parsers.c @@ -0,0 +1,139 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "policy.h" +#include "ipe_parser.h" + +#include <linux/slab.h> +#include <linux/types.h> +#include <linux/rbtree.h> + +static struct rb_root ipe_parser_root = RB_ROOT; + +struct parser_container { + struct rb_node node; + const struct ipe_parser *parser; +}; + +/** + * cmp_key: Comparator for the nodes within the parser tree by key + * @key: Supplies a the key to evaluate nodes against + * @n: Supplies a pointer to the node to compare. + * + * Return: + * <0 - @key is to the left of @n + * 0 - @key identifies @n + * >0 - @key is to the right of @n + */ +static int cmp_key(const void *key, const struct rb_node *n) +{ + const struct parser_container *node; + + node = container_of(n, struct parser_container, node); + + return strcmp((const char *)key, node->parser->first_token); +} + +/** + * cmp_node: Comparator for the nodes within the parser tree + * @n: Supplies a pointer to the node to compare + * @nn: Supplies a pointer to the another node to compare. + * + * Return: + * <0 - @n is lexigraphically before @nn + * 0 - @n is identical @nn + * >0 - @n is lexigraphically after @nn + */ +static int cmp_node(struct rb_node *n, const struct rb_node *nn) +{ + const struct parser_container *c1; + const struct parser_container *c2; + + c1 = container_of(n, struct parser_container, node); + c2 = container_of(nn, struct parser_container, node); + + return strcmp(c1->parser->first_token, c2->parser->first_token); +} + +/** + * ipe_lookup_parser: Attempt to find a ipe_property structure by @first_token. + * @first_token: The key to look for in the tree. + * + * Return: + * !NULL - OK + * NULL - No property exists under @key + */ +const struct ipe_parser *ipe_lookup_parser(const char *first_token) +{ + struct rb_node *n; + + n = rb_find(first_token, &ipe_parser_root, cmp_key); + if (!n) + return NULL; + + return container_of(n, struct parser_container, node)->parser; +} + +/** + * ipe_for_each_parser: Iterate over all currently-registered parsers + * calling @fn on the values, and providing @view @ctx. + * @view: The function to call for each property. This is given the property + * structure as the first argument, and @ctx as the second. + * @ctx: caller-specified context that is passed to the function. Can be NULL. + * + * Return: + * 0 - OK + * !0 - Proper errno as returned by @view. + */ +int ipe_for_each_parser(int (*view)(const struct ipe_parser *parser, + void *ctx), + void *ctx) +{ + int rc = 0; + struct rb_node *node; + struct parser_container *val; + + for (node = rb_first(&ipe_parser_root); node; node = rb_next(node)) { + val = container_of(node, struct parser_container, node); + + rc = view(val->parser, ctx); + if (rc) + return rc; + } + + return rc; +} + +/** + * ipe_register_parser: Register a parser to be used in IPE's policy. + * @p: Parser to register. + * + * This function allows parsers (policy constructs that effect IPE's + * internal functionality) to be leveraged in IPE policy. This must + * be called prior to any policies being loaded. + * + * Return: + * 0 - OK + * !0 - Error + */ +int ipe_register_parser(struct ipe_parser *p) +{ + struct rb_node *n = NULL; + struct parser_container *c = NULL; + + c = kzalloc(sizeof(*c), GFP_KERNEL); + if (!c) + return -ENOMEM; + + c->parser = p; + + n = rb_find_add(&c->node, &ipe_parser_root, cmp_node); + if (n) { + kfree(c); + return -EEXIST; + } + + return 0; +} diff --git a/security/ipe/parsers/Makefile b/security/ipe/parsers/Makefile new file mode 100644 index 000000000000..1a19a094724f --- /dev/null +++ b/security/ipe/parsers/Makefile @@ -0,0 +1,12 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (C) Microsoft Corporation. All rights reserved. +# +# Makefile for building the IPE module as part of the kernel tree. +# + +ccflags-y := -I$(srctree)/security/ipe + +obj-$(CONFIG_SECURITY_IPE) += \ + default.o \ + policy_header.o \ diff --git a/security/ipe/parsers/default.c b/security/ipe/parsers/default.c new file mode 100644 index 000000000000..30181d2cc4ed --- /dev/null +++ b/security/ipe/parsers/default.c @@ -0,0 +1,106 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include <linux/slab.h> +#include <linux/list.h> +#include <linux/errno.h> +#include <linux/string.h> + +#include "ipe_parser.h" + +static int set_op_default(enum ipe_operation op, enum ipe_action act, + struct ipe_parsed_policy *pol) +{ + size_t i, remap_len; + const enum ipe_operation *remap; + + if (!ipe_is_op_alias(op, &remap, &remap_len)) { + if (pol->rules[op].default_action != ipe_action_max) + return -EBADMSG; + + pol->rules[op].default_action = act; + return 0; + } + + for (i = 0; i < remap_len; ++i) { + if (pol->rules[remap[i]].default_action != ipe_action_max) + return -EBADMSG; + + pol->rules[remap[i]].default_action = act; + } + + return 0; +} + +static int parse_default(const struct ipe_policy_line *line, + struct ipe_parsed_policy *pol) +{ + int rc = 0; + size_t idx = 0; + struct ipe_policy_token *tok = NULL; + enum ipe_operation op = ipe_operation_max; + enum ipe_action act = ipe_action_max; + + list_for_each_entry(tok, &line->tokens, next) { + switch (idx) { + case 0: + if (strcmp("DEFAULT", tok->key) || tok->value) + return -EBADMSG; + break; + case 1: + /* schema 1 - operation, followed by action */ + rc = ipe_parse_op(tok, &op); + if (!rc) { + ++idx; + continue; + } + + if (pol->global_default != ipe_action_max) + return -EBADMSG; + + /* schema 2 - action */ + rc = ipe_parse_action(tok, &pol->global_default); + if (!rc) + return rc; + + return -EBADMSG; + case 2: + rc = ipe_parse_action(tok, &act); + if (rc) + return rc; + + return set_op_default(op, act, pol); + default: + return -EBADMSG; + } + ++idx; + } + + /* met no schema */ + return -EBADMSG; +} + +static int validate_defaults(const struct ipe_parsed_policy *p) +{ + size_t i = 0; + + if (p->global_default != ipe_action_max) + return 0; + + for (i = 0; i < ARRAY_SIZE(p->rules); ++i) { + if (p->rules[i].default_action == ipe_action_max) + return -EBADMSG; + } + + return 0; +} + +IPE_PARSER(default_decl) = { + .first_token = "DEFAULT", + .version = 1, + .parse = parse_default, + .free = NULL, + .validate = validate_defaults, +}; diff --git a/security/ipe/parsers/policy_header.c b/security/ipe/parsers/policy_header.c new file mode 100644 index 000000000000..4d3c1a42c915 --- /dev/null +++ b/security/ipe/parsers/policy_header.c @@ -0,0 +1,126 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "ipe_parser.h" + +#include <linux/slab.h> +#include <linux/list.h> +#include <linux/errno.h> +#include <linux/string.h> + +#include "ipe_parser.h" + +static int parse_name(const struct ipe_policy_token *t, + struct ipe_parsed_policy *p) +{ + if (p->name) + return -EBADMSG; + + p->name = kstrdup_const(t->value, GFP_KERNEL); + if (!p->name) + return -ENOMEM; + + return 0; +} + +static int parse_ver(const struct ipe_policy_token *t, + struct ipe_parsed_policy *p) +{ + int rc = 0; + char *dup = NULL; + char *dup2 = NULL; + char *token = NULL; + size_t sep_count = 0; + u16 *const cv[] = { &p->version.major, &p->version.minor, &p->version.rev }; + + dup = kstrdup(t->value, GFP_KERNEL); + if (!dup) { + rc = -ENOMEM; + goto err; + } + + dup2 = dup; + + while ((token = strsep(&dup, ".\n")) != NULL) { + /* prevent overflow */ + if (sep_count >= ARRAY_SIZE(cv)) { + rc = -EBADMSG; + goto err; + } + + rc = kstrtou16(token, 10, cv[sep_count]); + if (rc) + goto err; + + ++sep_count; + } + + /* prevent underflow */ + if (sep_count != ARRAY_SIZE(cv)) + rc = -EBADMSG; + +err: + kfree(dup2); + return rc; +} + +static const struct ipe_token_parser parsers[] = { + { .key = "policy_name", .parse_token = parse_name }, + { .key = "policy_version", .parse_token = parse_ver }, +}; + +static int parse_policy_hdr(const struct ipe_policy_line *line, + struct ipe_parsed_policy *pol) +{ + int rc = 0; + size_t idx = 0; + struct ipe_policy_token *tok = NULL; + const struct ipe_token_parser *p = NULL; + + list_for_each_entry(tok, &line->tokens, next) { + if (!tok->value || idx >= sizeof(parsers)) { + rc = -EBADMSG; + goto err; + } + + p = &parsers[idx]; + + if (strcmp(p->key, tok->key)) { + rc = -EBADMSG; + goto err; + } + + rc = p->parse_token(tok, pol); + if (rc) + goto err; + + ++idx; + } + + return 0; + +err: + return rc; +} + +static int free_policy_hdr(struct ipe_parsed_policy *pol) +{ + kfree(pol->name); + return 0; +} + +static int validate_policy_hdr(const struct ipe_parsed_policy *p) +{ + return !p->name ? -EBADMSG : 0; +} + +IPE_PARSER(policy_header) = { + .first_token = "policy_name", + .version = 1, + .parse = parse_policy_hdr, + .free = free_policy_hdr, + .validate = validate_policy_hdr, +}; diff --git a/security/ipe/policy.c b/security/ipe/policy.c new file mode 100644 index 000000000000..9dd60dd34477 --- /dev/null +++ b/security/ipe/policy.c @@ -0,0 +1,946 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "policy.h" +#include "ipe_parser.h" +#include "modules.h" + +#include <linux/slab.h> +#include <linux/list.h> +#include <linux/ctype.h> +#include <linux/types.h> +#include <linux/parser.h> +#include <linux/verification.h> + +#define START_COMMENT '#' +#define KEYVAL_DELIMIT '=' + +static inline bool is_quote(char ch) +{ + return ch == '\'' || ch == '\"'; +} + +/** + * is_key_char: Determine whether @ch is an acceptable character for a + * key type + * @ch: Supplies the character to evaluate. + * + * Return: + * true - Character is acceptable. + * false - Character is not acceptable. + */ +static inline bool is_key_char(char ch) +{ + return isalnum(ch) || ch == '_'; +} + +/** + * is_val_char: Determine whether @ch is an acceptable character for a + * value type + * @ch: Supplies the character to evaluate. + * + * Return: + * true - Character is acceptable. + * false - Character is not acceptable. + */ +static inline bool is_val_char(char ch) +{ + return isgraph(ch) || ch == ' ' || ch == '\t'; +} + +/** + * free_parser: Callback to invoke, freeing data allocated by parsers. + * @parser: parser to free data. + * @ctx: ctx object passed to ipe_for_each_parser. + * + * This function is intended to be used with ipe_for_each_parser only. + * + * Return: + * 0 - Always + */ +static int free_parser(const struct ipe_parser *parser, void *ctx) +{ + struct ipe_parsed_policy *pol = ctx; + + if (parser->free) + parser->free(pol); + + return 0; +} + +/** + * free_rule: free an ipe_rule. + * @r: Supplies the rule to free. + * + * This function is safe to call if @r is NULL or ERR_PTR. + */ +static void free_rule(struct ipe_rule *r) +{ + struct ipe_policy_mod *p, *t; + + if (IS_ERR_OR_NULL(r)) + return; + + list_for_each_entry_safe(p, t, &r->modules, next) { + if (p->mod->free) + p->mod->free(p->mod_value); + + kfree(p); + } + + kfree(r); +} + +static void free_parsed_policy(struct ipe_parsed_policy *p) +{ + size_t i = 0; + struct ipe_rule *pp, *t; + + if (IS_ERR_OR_NULL(p)) + return; + + for (i = 0; i < ARRAY_SIZE(p->rules); ++i) + list_for_each_entry_safe(pp, t, &p->rules[i].rules, next) + free_rule(pp); + + (void)ipe_for_each_parser(free_parser, p); + kfree(p); +} + +/** + * free_parsed_line: free a single parsed line of tokens. + * @line: Supplies the line to free. + * + * This function is safe to call if @line is NULL or ERR_PTR. + */ +static void free_parsed_line(struct ipe_policy_line *line) +{ + struct ipe_policy_token *p, *t; + + if (IS_ERR_OR_NULL(line)) + return; + + list_for_each_entry_safe(p, t, &line->tokens, next) + kfree(p); +} + +/** + * free_parsed_text: free a 2D list representing a tokenized policy. + * @parsed: Supplies the policy to free. + * + * This function is safe to call if @parsed is NULL or ERR_PTR. + */ +static void free_parsed_text(struct list_head *parsed) +{ + struct ipe_policy_line *p, *t; + + if (IS_ERR_OR_NULL(parsed)) + return; + + list_for_each_entry_safe(p, t, parsed, next) + free_parsed_line(p); +} + +/** + * trim_quotes: Edit @str to remove a single instance of a trailing and + * leading quotes. + * @str: Supplies the string to edit. + * + * If the string is not quoted, @str will be returned. This function is + * safe to call if @str is NULL. + * + * Return: + * !0 - OK + * ERR_PTR(-EBADMSG) - Quote mismatch. + */ +static char *trim_quotes(char *str) +{ + char s; + size_t len; + + if (!str) + return str; + + s = *str; + + if (is_quote(s)) { + len = strlen(str) - 1; + + if (str[len] != s) + return ERR_PTR(-EBADMSG); + + str[len] = '\0'; + ++str; + } + + return str; +} + +/** + * parse_token: Parse a string into a proper token representation. + * @token: Supplies the token string to parse. + * + * @token will be edited destructively. Pass a copy if you wish to retain + * the state of the original. + * + * This function will emit an error to pr_err when a parsing error occurs. + * + * Return: + * !0 - OK + * ERR_PTR(-EBADMSG) - An invalid character was encountered while parsing. + * ERR_PTR(-ENOMEM) - No Memory + */ +static struct ipe_policy_token *parse_token(char *token) +{ + size_t i, len = 0; + char *key = token; + char *value = NULL; + struct ipe_policy_token *local = NULL; + + len = strlen(token); + + for (i = 0; (i < len) && token[i] != KEYVAL_DELIMIT; ++i) + if (!is_key_char(token[i])) + return ERR_PTR(-EBADMSG); + + token[i] = '\0'; + ++i; + + /* there is a value */ + if (i < len) { + value = trim_quotes(&token[i]); + if (IS_ERR(value)) + return ERR_PTR(-EBADMSG); + + len = strlen(value); + + for (i = 0; i < len; ++i) + if (!is_val_char(value[i])) + return ERR_PTR(-EBADMSG); + } + + local = kzalloc(sizeof(*local), GFP_KERNEL); + if (!local) + return ERR_PTR(-ENOMEM); + + INIT_LIST_HEAD(&local->next); + local->key = key; + local->value = value; + + return local; +} + +/** + * append_token: Parse and append a token into an ipe_policy_line structure. + * @p: Supplies the ipe_policy_line structure to append to. + * @token: Supplies the token to parse and append to. + * + * @token will be edited during the parsing destructively. Pass a copy if you + * wish to retain the original. + * + * Return: + * 0 - OK + * -EBADMSG - Parsing error of @token + */ +static int append_token(struct ipe_policy_line *p, char *token) +{ + struct ipe_policy_token *t = NULL; + + t = parse_token(token); + if (IS_ERR(t)) + return PTR_ERR(t); + + list_add_tail(&t->next, &p->tokens); + + return 0; +} + +/** + * alloc_line: Allocate an ipe_policy_line structure. + * + * Return: + * !0 - OK + * -EBADMSG - Parsing error of @token + */ +static struct ipe_policy_line *alloc_line(void) +{ + struct ipe_policy_line *l = NULL; + + l = kzalloc(sizeof(*l), GFP_KERNEL); + if (!l) + return ERR_PTR(-ENOMEM); + + INIT_LIST_HEAD(&l->next); + INIT_LIST_HEAD(&l->tokens); + + return l; +} + +/** + * insert_token: Append a token to @line. + * @token: Supplies the token to append to @line. + * @line: Supplies a pointer to the ipe_policy_line structure to append to. + * + * If @line is NULL, it will be allocated on behalf of the caller. + * + * Return: + * 0 - OK + * -ENOMEM - No Memory + * -EBADMSG - Parsing error of @token + */ +static int insert_token(char *token, struct ipe_policy_line **line) +{ + int rc = 0; + struct ipe_policy_line *local = *line; + + if (!local) { + local = alloc_line(); + if (IS_ERR(local)) + return PTR_ERR(local); + + *line = local; + } + + rc = append_token(local, token); + if (rc) + return rc; + + return 0; +} + +/** + * ipe_tokenize_line: Parse a line of text into a list of token structures. + * @line: Supplies the line to parse. + * + * The final result can be NULL, which represents no tokens were parsed. + * + * Return: + * !0 - OK + * NULL - OK, no tokens were parsed. + * ERR_PTR(-EBADMSG) - Invalid policy syntax + * ERR_PTR(-ENOMEM) - No Memory + */ +static struct ipe_policy_line *tokenize_line(char *line) +{ + int rc = 0; + size_t i = 0; + size_t len = 0; + char *tok = NULL; + char quote = '\0'; + struct ipe_policy_line *p = NULL; + + /* nullterm guaranteed by strsep */ + len = strlen(line); + + for (i = 0; i < len; ++i) { + if (quote == '\0' && is_quote(line[i])) { + quote = line[i]; + continue; + } + + if (quote != '\0' && line[i] == quote) { + quote = '\0'; + continue; + } + + if (quote == '\0' && line[i] == START_COMMENT) { + tok = NULL; + break; + } + + if (isgraph(line[i]) && !tok) + tok = &line[i]; + + if (quote == '\0' && isspace(line[i])) { + line[i] = '\0'; + + if (!tok) + continue; + + rc = insert_token(tok, &p); + if (rc) + goto err; + + tok = NULL; + } + } + + if (quote != '\0') { + rc = -EBADMSG; + goto err; + } + + if (tok) { + rc = insert_token(tok, &p); + if (rc) + goto err; + } + + return p; + +err: + free_parsed_line(p); + return ERR_PTR(rc); +} + +/** + * parse_pass1: parse @policy into a 2D list, representing tokens on each line. + * @policy: Supplies the policy to parse. Must be nullterminated, and is + * edited. + * + * In pass1 of the parser, the policy is tokenized. Minor structure checks + * are done (mismatching quotes, invalid characters). + * + * Caller must maintain the lifetime of @policy while the return value is + * alive. + * + * Return: + * !0 - OK + * ERR_PTR(-ENOMEM) - Out of Memory + * ERR_PTR(-EBADMSG) - Parsing Error + */ +static int parse_pass1(char *policy, struct list_head *tokens) +{ + int rc = 0; + char *p = NULL; + + while ((p = strsep(&policy, "\n\0")) != NULL) { + struct ipe_policy_line *t = NULL; + + t = tokenize_line(p); + if (IS_ERR(t)) { + rc = PTR_ERR(t); + goto err_free_parsed; + } + + if (!t) + continue; + + list_add_tail(&t->next, tokens); + } + + return 0; + +err_free_parsed: + free_parsed_text(tokens); + return rc; +} + +/** + * parse_pass2: Take the 2D list of tokens generated from pass1, and transform + * it into a partial ipe_policy. + * @parsed: Supplies the list of tokens generated from pass1. + * @p: Policy to manipulate with parsed tokens. + * + * This function is where various declarations and references are parsed into + * policy. All declarations and references required to parse rules should be + * done here as a parser, and then in pass3 these can be utilized. + * + * Return: + * !0 - OK + * -EBADMSG - Syntax Parsing Errors + * -ENOENT - No handler for a token. + * -ENOMEM - Out of memory + */ +static int parse_pass2(struct list_head *parsed, struct ipe_parsed_policy *pol) +{ + int rc = 0; + const struct ipe_parser *p = NULL; + struct ipe_policy_line *line = NULL; + const struct ipe_policy_token *token = NULL; + + list_for_each_entry(line, parsed, next) { + token = list_first_entry(&line->tokens, struct ipe_policy_token, next); + p = ipe_lookup_parser(token->key); + if (!p) + continue; + + rc = p->parse(line, pol); + if (rc) + return rc; + + line->consumed = true; + } + + return rc; +} + +/** + * ipe_parse_op: parse a token to an operation value. + * @tok: Token to parse + * @op: Operation Parsed. + * + * Return: + * 0 - OK + * -EINVAL - Invalid key or value. + */ +int ipe_parse_op(const struct ipe_policy_token *tok, + enum ipe_operation *op) +{ + substring_t match[MAX_OPT_ARGS] = { 0 }; + const match_table_t ops = { + { ipe_op_alias_max, NULL }, + }; + + if (strcmp(tok->key, "op") || !tok->value) + return -EINVAL; + + *op = match_token((char *)tok->value, ops, match); + if ((*op) == (int)ipe_op_alias_max) + return -ENOENT; + + return 0; +} + +/** + * ipe_parse_action: parse a token to an operation value. + * @tok: Token to parse + * @action: action parsed. + * + * Return: + * 0 - OK + * -EINVAL - Invalid key or value. + */ +int ipe_parse_action(const struct ipe_policy_token *tok, + enum ipe_action *action) +{ + substring_t match[MAX_OPT_ARGS] = { 0 }; + const match_table_t actions = { + { ipe_action_allow, "ALLOW" }, + { ipe_action_deny, "DENY" }, + { ipe_action_max, NULL }, + }; + + if (strcmp(tok->key, "action") || !tok->value) + return -EINVAL; + + *action = match_token((char *)tok->value, actions, match); + + if (*action == ipe_action_max) + return -EINVAL; + + return 0; +} + +/** + * parse_mod_to_rule: Parse a module token and append the values to the + * provided rule. + * @t: Supplies the token to parse. + * @r: Supplies the rule to modify with the result. + * + * Return: + * 0 - OK + * -ENOENT - No such module to handle @t. + * -ENOMEM - No memory. + * Others - Module defined errors. + */ +static int parse_mod_to_rule(const struct ipe_policy_token *t, struct ipe_rule *r) +{ + int rc = 0; + struct ipe_policy_mod *p = NULL; + const struct ipe_module *m = NULL; + + m = ipe_lookup_module(t->key); + if (IS_ERR_OR_NULL(m)) { + rc = (m) ? PTR_ERR(m) : -ENOENT; + goto err; + } + + p = kzalloc(sizeof(*p), GFP_KERNEL); + if (!p) { + rc = -ENOMEM; + goto err; + } + INIT_LIST_HEAD(&p->next); + p->mod = m; + + rc = m->parse(t->value, &p->mod_value); + if (rc) + goto err2; + + list_add_tail(&p->next, &r->modules); + return 0; +err2: + kfree(p); +err: + return rc; +} + +/** + * parse_rule: Parse a policy line into an ipe_rule structure. + * @line: Supplies the line to parse. + * + * Return: + * Valid ipe_rule - OK + * ERR_PTR(-ENOMEM) - Out of Memory + * ERR_PTR(-ENOENT) - No such module to handle a token + * ERR_PTR(-EINVAL) - An unacceptable value has been encountered. + * ERR_PTR(...) - Module defined errors. + */ +static struct ipe_rule *parse_rule(const struct ipe_policy_line *line) +{ + int rc = 0; + struct ipe_rule *r = NULL; + const struct list_head *node = NULL; + + r = kzalloc(sizeof(*r), GFP_KERNEL); + if (!r) { + rc = -ENOMEM; + goto err; + } + + INIT_LIST_HEAD(&r->next); + INIT_LIST_HEAD(&r->modules); + r->op = (int)ipe_op_alias_max; + r->action = ipe_action_max; + + list_for_each(node, &line->tokens) { + const struct ipe_policy_token *token = NULL; + + token = container_of(node, struct ipe_policy_token, next); + + if (list_is_first(node, &line->tokens)) { + enum ipe_operation op; + + rc = ipe_parse_op(token, &op); + if (rc) + goto err; + + r->op = op; + continue; + } + + if (list_is_last(node, &line->tokens)) { + enum ipe_action action; + + rc = ipe_parse_action(token, &action); + if (rc) + goto err; + + r->action = action; + continue; + } + + rc = parse_mod_to_rule(token, r); + if (rc) + goto err; + } + + if (r->action == ipe_action_max || r->op == (int)ipe_op_alias_max) { + rc = -EBADMSG; + goto err; + } + + return r; +err: + free_rule(r); + return ERR_PTR(rc); +} + +/** + * parse_pass3: Take the partially parsed list of tokens from pass 1 and the + * parial policy from pass 2, and finalize the policy. + * @parsed: Supplies the tokens parsed from pass 1. + * @p: Supplies the partial policy from pass 2. + * + * This function finalizes the IPE policy by parsing all rules in the + * policy. This must occur in pass3, as in pass2, references are resolved + * that can be used in pass3. + * + * Return: + * 0 - OK + * !0 - Standard errno + */ +static int parse_pass3(struct list_head *parsed, + struct ipe_parsed_policy *p) +{ + int rc = 0; + size_t i = 0; + size_t remap_len = 0; + struct ipe_rule *rule = NULL; + struct ipe_policy_line *line = NULL; + const enum ipe_operation *remap; + + list_for_each_entry(line, parsed, next) { + if (line->consumed) + continue; + + rule = parse_rule(line); + if (IS_ERR(rule)) { + rc = PTR_ERR(rule); + goto err; + } + + if (ipe_is_op_alias(rule->op, &remap, &remap_len)) { + for (i = 0; i < remap_len; ++i) { + rule->op = remap[i]; + list_add_tail(&rule->next, &p->rules[rule->op].rules); + rule = parse_rule(line); + } + + free_rule(rule); + } else { + list_add_tail(&rule->next, &p->rules[rule->op].rules); + } + + line->consumed = true; + } + + return 0; +err: + free_rule(rule); + return rc; +} + +/** + * parser_validate: Callback to invoke, validating parsers as necessary + * @parser: parser to call to validate data. + * @ctx: ctx object passed to ipe_for_each_parser. + * + * This function is intended to be used with ipe_for_each_parser only. + * + * Return: + * 0 - OK + * !0 - Validation failed. + */ +static int parser_validate(const struct ipe_parser *parser, void *ctx) +{ + int rc = 0; + const struct ipe_parsed_policy *pol = ctx; + + if (parser->validate) + rc = parser->validate(pol); + + return rc; +} + +/** + * validate_policy: Given a policy structure that was just parsed, validate + * that all necessary fields are present, initialized + * correctly, and all lines parsed are have been consumed. + * @parsed: Supplies the policy lines that were parsed in pass1. + * @policy: Supplies the fully parsed policy. + * + * A parsed policy can be an invalid state for use (a default was undefined, + * a header was undefined) by just parsing the policy. + * + * Return: + * 0 - OK + * -EBADMSG - Policy is invalid. + */ +static int validate_policy(const struct list_head *parsed, + const struct ipe_parsed_policy *p) +{ + int rc = 0; + const struct ipe_policy_line *line = NULL; + + list_for_each_entry(line, parsed, next) { + if (!line->consumed) + return -EBADMSG; + } + + rc = ipe_for_each_parser(parser_validate, + (struct ipe_parsed_policy *)p); + + return rc; +} + +/** + * new_parsed_policy: Allocate and initialize a parsed policy to its default + * values. + * + * Return: + * !IS_ERR - OK + */ +static struct ipe_parsed_policy *new_parsed_policy(void) +{ + size_t i = 0; + struct ipe_parsed_policy *p = NULL; + struct ipe_operation_table *t = NULL; + + p = kzalloc(sizeof(*p), GFP_KERNEL); + if (!p) + return ERR_PTR(-ENOMEM); + + p->global_default = ipe_action_max; + + for (i = 0; i < ARRAY_SIZE(p->rules); ++i) { + t = &p->rules[i]; + + t->default_action = ipe_action_max; + INIT_LIST_HEAD(&t->rules); + } + + return p; +} + +/** + * parse_policy: Given a string, parse the string into an IPE policy + * structure. + * @p: partially filled ipe_policy structure to populate with the result. + * + * @p must have text and textlen set. + * + * Return: + * Valid ipe_policy structure - OK + * ERR_PTR(-EBADMSG) - Invalid Policy Syntax (Unrecoverable) + * ERR_PTR(-ENOMEM) - Out of Memory + */ +static int parse_policy(struct ipe_policy *p) +{ + int rc = 0; + char *dup = NULL; + LIST_HEAD(parsed); + struct ipe_parsed_policy *pp = NULL; + + if (!p->textlen) + return -EBADMSG; + + dup = kmemdup_nul(p->text, p->textlen, GFP_KERNEL); + if (!dup) + return -ENOMEM; + + pp = new_parsed_policy(); + if (IS_ERR(pp)) { + rc = PTR_ERR(pp); + goto out; + } + + rc = parse_pass1(dup, &parsed); + if (rc) + goto err; + + rc = parse_pass2(&parsed, pp); + if (rc) + goto err; + + rc = parse_pass3(&parsed, pp); + if (rc) + goto err; + + rc = validate_policy(&parsed, pp); + if (rc) + goto err; + + p->parsed = pp; + + goto out; +err: + free_parsed_policy(pp); +out: + free_parsed_text(&parsed); + kfree(dup); + + return rc; +} + +/** + * ipe_is_op_alias: Determine if @op is an alias for one or more operations + * @op: Supplies the operation to check. Should be either ipe_operation or + * ipe_op_alias. + * @map: Supplies a pointer to populate with the mapping if @op is an alias + * @size: Supplies the size of @map if @op is an alias. + * + * Return: + * true - @op is an alias + * false - @op is not an alias + */ +bool ipe_is_op_alias(int op, const enum ipe_operation **map, size_t *size) +{ + switch (op) { + default: + return false; + } +} + +/** + * ipe_free_policy: Deallocate a given IPE policy. + * @p: Supplies the policy to free. + * + * Safe to call on IS_ERR/NULL. + */ +void ipe_put_policy(struct ipe_policy *p) +{ + if (IS_ERR_OR_NULL(p) || !refcount_dec_and_test(&p->refcount)) + return; + + free_parsed_policy(p->parsed); + if (!p->pkcs7) + kfree(p->text); + kfree(p->pkcs7); + kfree(p); +} + +static int set_pkcs7_data(void *ctx, const void *data, size_t len, + size_t asn1hdrlen) +{ + struct ipe_policy *p = ctx; + + p->text = (const char *)data; + p->textlen = len; + + return 0; +} + +/** + * ipe_new_policy: allocate and parse an ipe_policy structure. + * + * @text: Supplies a pointer to the plain-text policy to parse. + * @textlen: Supplies the length of @text. + * @pkcs7: Supplies a pointer to a pkcs7-signed IPE policy. + * @pkcs7len: Supplies the length of @pkcs7. + * + * @text/@textlen Should be NULL/0 if @pkcs7/@pkcs7len is set. + * + * The result will still need to be associated with a context via + * ipe_add_policy. + * + * Return: + * !IS_ERR - Success + */ +struct ipe_policy *ipe_new_policy(const char *text, size_t textlen, + const char *pkcs7, size_t pkcs7len) +{ + int rc = 0; + struct ipe_policy *new = NULL; + + new = kzalloc(sizeof(*new), GFP_KERNEL); + if (!new) + return ERR_PTR(-ENOMEM); + + refcount_set(&new->refcount, 1); + + if (!text) { + new->pkcs7len = pkcs7len; + new->pkcs7 = kmemdup(pkcs7, pkcs7len, GFP_KERNEL); + if (!new->pkcs7) { + rc = -ENOMEM; + goto err; + } + + rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len, NULL, + VERIFYING_UNSPECIFIED_SIGNATURE, + set_pkcs7_data, new); + if (rc) + goto err; + } else { + new->textlen = textlen; + new->text = kstrndup(text, textlen, GFP_KERNEL); + if (!new->text) { + rc = -ENOMEM; + goto err; + } + } + + rc = parse_policy(new); + if (rc) + goto err; + + return new; +err: + ipe_put_policy(new); + return ERR_PTR(rc); +} diff --git a/security/ipe/policy.h b/security/ipe/policy.h new file mode 100644 index 000000000000..d78788db238c --- /dev/null +++ b/security/ipe/policy.h @@ -0,0 +1,97 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#ifndef IPE_POLICY_H +#define IPE_POLICY_H + +#include <linux/list.h> +#include <linux/types.h> +#include <linux/refcount.h> + +struct ipe_policy_token { + struct list_head next; /* type: policy_token */ + + const char *key; + const char *value; +}; + +struct ipe_policy_line { + struct list_head next; /* type: policy_line */ + struct list_head tokens; /* type: policy_token */ + + bool consumed; +}; + +struct ipe_module; + +enum ipe_operation { + ipe_operation_max = 0, +}; + +/* + * Extension to ipe_operation, representing operations + * that are just one or more operations under the hood + */ +enum ipe_op_alias { + ipe_op_alias_max = ipe_operation_max, +}; + +enum ipe_action { + ipe_action_allow = 0, + ipe_action_deny, + ipe_action_max, +}; + +struct ipe_policy_mod { + const struct ipe_module *mod; + void *mod_value; + + struct list_head next; +}; + +struct ipe_rule { + enum ipe_operation op; + enum ipe_action action; + + struct list_head modules; + + struct list_head next; +}; + +struct ipe_operation_table { + struct list_head rules; + enum ipe_action default_action; +}; + +struct ipe_parsed_policy { + const char *name; + struct { + u16 major; + u16 minor; + u16 rev; + } version; + + enum ipe_action global_default; + + struct ipe_operation_table rules[ipe_operation_max]; +}; + +struct ipe_policy { + const char *pkcs7; + size_t pkcs7len; + + const char *text; + size_t textlen; + + struct ipe_parsed_policy *parsed; + + refcount_t refcount; +}; + +struct ipe_policy *ipe_new_policy(const char *text, size_t textlen, + const char *pkcs7, size_t pkcs7len); +void ipe_put_policy(struct ipe_policy *pol); +bool ipe_is_op_alias(int op, const enum ipe_operation **map, size_t *size); + +#endif /* IPE_POLICY_H */ -- 2.33.0

From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; As is typical with LSMs, IPE uses securityfs as its interface with userspace. for a complete list of the interfaces and the respective inputs/outputs, please see the documentation under admin-guide/LSM/ipe.rst Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Refactor series to: 1. Support a context structure, enabling easier testing * Split up patch 03/12 into two parts: 1. parser [02/16] 2. userspace interface [04/16] (this patch) * Interface changes: 1. "raw" was renamed to "pkcs7" and made read only 2. "raw"'s write functionality (update a policy) moved to "update" 3. introduced "version", "policy_name" nodes. 4. "content" renamed to "policy" 5. The boot policy can now be updated like any other policy. --- security/ipe/Makefile | 2 + security/ipe/ctx.c | 121 +++++++++ security/ipe/ctx.h | 6 + security/ipe/fs.c | 170 +++++++++++++ security/ipe/fs.h | 13 + security/ipe/policy.c | 41 ++++ security/ipe/policy.h | 4 + security/ipe/policyfs.c | 528 ++++++++++++++++++++++++++++++++++++++++ 8 files changed, 885 insertions(+) create mode 100644 security/ipe/fs.c create mode 100644 security/ipe/fs.h create mode 100644 security/ipe/policyfs.c diff --git a/security/ipe/Makefile b/security/ipe/Makefile index 0db69f13e82a..d5660a17364c 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -10,9 +10,11 @@ ccflags-y := -I$(srctree)/security/ipe/modules obj-$(CONFIG_SECURITY_IPE) += \ ctx.o \ eval.o \ + fs.o \ hooks.o \ ipe.o \ modules.o \ parsers/ \ parsers.o \ policy.o \ + policyfs.o \ diff --git a/security/ipe/ctx.c b/security/ipe/ctx.c index 9274e51eff52..664c671a4f9c 100644 --- a/security/ipe/ctx.c +++ b/security/ipe/ctx.c @@ -13,6 +13,29 @@ #include <linux/refcount.h> #include <linux/spinlock.h> +/** + * ver_to_u64: convert an internal ipe_policy_version to a u64 + * @p: Policy to extract the version from + * + * Bits (LSB is index 0): + * [48,32] -> Major + * [32,16] -> Minor + * [16, 0] -> Revision + * + * Return: + * u64 version of the embedded version structure. + */ +static inline u64 ver_to_u64(const struct ipe_policy *const p) +{ + u64 r = 0; + + r = (((u64)p->parsed->version.major) << 32) + | (((u64)p->parsed->version.minor) << 16) + | ((u64)(p->parsed->version.rev)); + + return r; +} + /** * ipe_current_ctx: Helper to retrieve the ipe_context for the current task. * @@ -96,6 +119,7 @@ static void free_ctx_work(struct work_struct *const work) list_for_each_entry(p, &ctx->policies, next) ipe_put_policy(p); + securityfs_remove(ctx->policy_root); kfree(ctx); } @@ -160,6 +184,9 @@ void ipe_remove_policy(struct ipe_policy *p) * ipe_add_policy: Associate @p with @ctx * @ctx: Supplies a pointer to the ipe_context structure to associate @p with. * @p: Supplies a pointer to the ipe_policy structure to associate. + * + * This will increase @p's reference count by one. + * */ void ipe_add_policy(struct ipe_context *ctx, struct ipe_policy *p) { @@ -168,7 +195,101 @@ void ipe_add_policy(struct ipe_context *ctx, struct ipe_policy *p) list_add_tail(&p->next, &ctx->policies); refcount_inc(&p->refcount); spin_unlock(&ctx->lock); +} + +/** + * ipe_replace_policy: Replace @old with @new in the list of policies in @ctx + * @ctx: Supplies the context object to manipulate. + * @old: Supplies a pointer to the ipe_policy to replace with @new + * @new: Supplies a pointer to the ipe_policy structure to replace @old with + */ +int ipe_replace_policy(struct ipe_policy *old, struct ipe_policy *new) +{ + int rc = -EINVAL; + struct ipe_context *ctx; + struct ipe_policy *cursor; + struct ipe_policy *p = NULL; + + ctx = ipe_get_ctx_rcu(old->ctx); + if (!ctx) + return -ENOENT; + + spin_lock(&ctx->lock); + list_for_each_entry(cursor, &ctx->policies, next) { + if (!strcmp(old->parsed->name, cursor->parsed->name)) { + if (ipe_is_policy_active(old)) { + if (ver_to_u64(old) > ver_to_u64(new)) + break; + rcu_assign_pointer(ctx->active_policy, new); + } + list_replace_init(&cursor->next, &new->next); + refcount_inc(&new->refcount); + rcu_assign_pointer(new->ctx, old->ctx); + p = cursor; + rc = 0; + break; + } + } + spin_unlock(&ctx->lock); + synchronize_rcu(); + + ipe_put_policy(p); + ipe_put_ctx(ctx); + return rc; +} + +/** + * ipe_set_active_pol: Make @p the active policy. + * @p: Supplies a pointer to the policy to make active. + */ +int ipe_set_active_pol(const struct ipe_policy *p) +{ + int rc = 0; + struct ipe_policy *ap = NULL; + struct ipe_context *ctx = NULL; + + ctx = ipe_get_ctx_rcu(p->ctx); + if (!ctx) { + rc = -ENOENT; + goto out; + } + + ap = ipe_get_policy_rcu(ctx->active_policy); + if (ap && ver_to_u64(ap) > ver_to_u64(p)) { + rc = -EINVAL; + goto out; + } + + spin_lock(&ctx->lock); + rcu_assign_pointer(ctx->active_policy, p); + spin_unlock(&ctx->lock); synchronize_rcu(); + +out: + ipe_put_policy(ap); + ipe_put_ctx(ctx); + return rc; +} + +/** + * ipe_is_policy_active: Determine wehther @p is the active policy + * @p: Supplies a pointer to the policy to check. + * + * Return: + * true - @p is the active policy of @ctx + * false - @p is not the active policy of @ctx + */ +bool ipe_is_policy_active(const struct ipe_policy *p) +{ + bool rv; + struct ipe_context *ctx; + + rcu_read_lock(); + ctx = rcu_dereference(p->ctx); + rv = !IS_ERR_OR_NULL(ctx) && rcu_access_pointer(ctx->active_policy) == p; + rcu_read_unlock(); + + return rv; } /** diff --git a/security/ipe/ctx.h b/security/ipe/ctx.h index a0da92da818c..fe11fb767788 100644 --- a/security/ipe/ctx.h +++ b/security/ipe/ctx.h @@ -7,6 +7,7 @@ #include <linux/sched.h> #include <linux/types.h> +#include <linux/dcache.h> #include <linux/refcount.h> #include <linux/spinlock.h> #include <linux/workqueue.h> @@ -20,6 +21,8 @@ struct ipe_context { struct list_head policies; /* type: ipe_policy */ + struct dentry *policy_root; + struct work_struct free_work; }; @@ -30,5 +33,8 @@ struct ipe_context *ipe_get_ctx_rcu(struct ipe_context __rcu *ctx); void ipe_put_ctx(struct ipe_context *ctx); void ipe_add_policy(struct ipe_context *ctx, struct ipe_policy *p); void ipe_remove_policy(struct ipe_policy *p); +int ipe_replace_policy(struct ipe_policy *old, struct ipe_policy *new); +int ipe_set_active_pol(const struct ipe_policy *p); +bool ipe_is_policy_active(const struct ipe_policy *p); #endif /* IPE_CONTEXT_H */ diff --git a/security/ipe/fs.c b/security/ipe/fs.c new file mode 100644 index 000000000000..10ad23f8bf92 --- /dev/null +++ b/security/ipe/fs.c @@ -0,0 +1,170 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#include "ipe.h" +#include "fs.h" +#include "policy.h" + +#include <linux/dcache.h> +#include <linux/security.h> + +static struct dentry *np __ro_after_init; +static struct dentry *root __ro_after_init; +static struct dentry *config __ro_after_init; + +/** + * new_policy: Write handler for the securityfs node, "ipe/new_policy" + * @f: Supplies a file structure representing the securityfs node. + * @data: Suppleis a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t new_policy(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + char *copy = NULL; + struct ipe_policy *p = NULL; + struct ipe_context *ctx = NULL; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + ctx = ipe_current_ctx(); + + copy = memdup_user_nul(data, len); + if (IS_ERR(copy)) { + rc = PTR_ERR(copy); + goto err; + } + + p = ipe_new_policy(NULL, 0, copy, len); + if (IS_ERR(p)) { + rc = PTR_ERR(p); + goto err; + } + + rc = ipe_new_policyfs_node(ctx, p); + if (rc) + goto err; + + ipe_add_policy(ctx, p); +err: + ipe_put_policy(p); + ipe_put_ctx(ctx); + return (rc < 0) ? rc : len; +} + +/** + * get_config: Read handler for the securityfs node, "ipe/config" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the read syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t get_config(struct file *f, char __user *data, size_t len, + loff_t *offset) +{ + int rc = 0; + char *buf = NULL; + size_t buflen = 0; + char tmp[30] = { 0 }; + struct ipe_parser *p = NULL; + struct ipe_module *m = NULL; + + for (p = __start_ipe_parsers; p < __end_ipe_parsers; ++p) + buflen += snprintf(NULL, 0, "%s=%d\n", p->first_token, p->version); + for (m = __start_ipe_modules; m < __end_ipe_modules; ++m) + buflen += snprintf(NULL, 0, "%s=%d\n", m->name, m->version); + + ++buflen; + buf = kzalloc(buflen, GFP_KERNEL); + if (!buf) { + rc = -ENOMEM; + goto out; + } + + for (p = __start_ipe_parsers; p < __end_ipe_parsers; ++p) { + memset(tmp, 0x0, ARRAY_SIZE(tmp)); + scnprintf(tmp, ARRAY_SIZE(tmp), "%s=%d\n", p->first_token, p->version); + strcat(buf, tmp); + } + + for (m = __start_ipe_modules; m < __end_ipe_modules; ++m) { + memset(tmp, 0x0, ARRAY_SIZE(tmp)); + scnprintf(tmp, ARRAY_SIZE(tmp), "%s=%d\n", m->name, m->version); + strcat(buf, tmp); + } + + rc = simple_read_from_buffer(data, len, offset, buf, buflen); +out: + kfree(buf); + return rc; +} + +static const struct file_operations cfg_fops = { + .read = get_config, +}; + +static const struct file_operations np_fops = { + .write = new_policy, +}; + +/** + * ipe_init_securityfs: Initialize IPE's securityfs tree at fsinit + * + * Return: + * !0 - Error + * 0 - OK + */ +static int __init ipe_init_securityfs(void) +{ + int rc = 0; + struct ipe_context *ctx = NULL; + + ctx = ipe_current_ctx(); + + root = securityfs_create_dir("ipe", NULL); + if (IS_ERR(root)) { + rc = PTR_ERR(root); + goto err; + } + + np = securityfs_create_file("new_policy", 0200, root, NULL, &np_fops); + if (IS_ERR(np)) { + rc = PTR_ERR(np); + goto err; + } + + config = securityfs_create_file("config", 0400, root, NULL, + &cfg_fops); + if (IS_ERR(config)) { + rc = PTR_ERR(config); + goto err; + } + + ctx->policy_root = securityfs_create_dir("policies", root); + if (IS_ERR(ctx->policy_root)) { + rc = PTR_ERR(ctx->policy_root); + goto err; + } + + return 0; +err: + securityfs_remove(np); + securityfs_remove(root); + securityfs_remove(config); + securityfs_remove(ctx->policy_root); + return rc; +} + +fs_initcall(ipe_init_securityfs); diff --git a/security/ipe/fs.h b/security/ipe/fs.h new file mode 100644 index 000000000000..4ab2f4e8c454 --- /dev/null +++ b/security/ipe/fs.h @@ -0,0 +1,13 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#ifndef IPE_FS_H +#define IPE_FS_H + +void ipe_soft_del_policyfs(struct ipe_policy *p); +int ipe_new_policyfs_node(struct ipe_context *ctx, struct ipe_policy *p); +void ipe_del_policyfs_node(struct ipe_policy *p); + +#endif /* IPE_FS_H */ diff --git a/security/ipe/policy.c b/security/ipe/policy.c index 8970f96453d6..b766824cc08f 100644 --- a/security/ipe/policy.c +++ b/security/ipe/policy.c @@ -4,6 +4,7 @@ */ #include "ipe.h" +#include "fs.h" #include "policy.h" #include "ipe_parser.h" #include "modules.h" @@ -867,6 +868,8 @@ void ipe_put_policy(struct ipe_policy *p) if (IS_ERR_OR_NULL(p) || !refcount_dec_and_test(&p->refcount)) return; + ipe_del_policyfs_node(p); + securityfs_remove(p->policyfs); free_parsed_policy(p->parsed); if (!p->pkcs7) kfree(p->text); @@ -911,6 +914,44 @@ static int set_pkcs7_data(void *ctx, const void *data, size_t len, return 0; } +/** + * ipe_update_policy: parse a new policy and replace @old with it. + * @old: Supplies a pointer to the policy to replace + * @text: Supplies a pointer to the plain text policy + * @textlen: Supplies the length of @text + * @pkcs7: Supplies a pointer to a buffer containing a pkcs7 message. + * @pkcs7len: Supplies the length of @pkcs7len + * + * @text/@textlen is mutually exclusive with @pkcs7/@pkcs7len - see + * ipe_new_policy. + * + * Return: + * !IS_ERR - OK + */ +struct ipe_policy *ipe_update_policy(struct ipe_policy *old, + const char *text, size_t textlen, + const char *pkcs7, size_t pkcs7len) +{ + int rc = 0; + struct ipe_policy *new; + + new = ipe_new_policy(text, textlen, pkcs7, pkcs7len); + if (IS_ERR(new)) { + rc = PTR_ERR(new); + goto err; + } + + if (strcmp(new->parsed->name, old->parsed->name)) { + rc = -EINVAL; + goto err; + } + + rc = ipe_replace_policy(old, new); +err: + ipe_put_policy(new); + return (rc < 0) ? ERR_PTR(rc) : new; +} + /** * ipe_new_policy: allocate and parse an ipe_policy structure. * diff --git a/security/ipe/policy.h b/security/ipe/policy.h index 2b5041c5a75a..6818f6405dd0 100644 --- a/security/ipe/policy.h +++ b/security/ipe/policy.h @@ -88,12 +88,16 @@ struct ipe_policy { refcount_t refcount; + struct dentry *policyfs; struct list_head next; /* type: ipe_policy */ struct ipe_context __rcu *ctx; }; struct ipe_policy *ipe_new_policy(const char *text, size_t textlen, const char *pkcs7, size_t pkcs7len); +struct ipe_policy *ipe_update_policy(struct ipe_policy *old, const char *text, + size_t textlen, const char *pkcs7, + size_t pkcs7len); void ipe_put_policy(struct ipe_policy *pol); bool ipe_is_op_alias(int op, const enum ipe_operation **map, size_t *size); struct ipe_policy *ipe_get_policy_rcu(struct ipe_policy __rcu *p); diff --git a/security/ipe/policyfs.c b/security/ipe/policyfs.c new file mode 100644 index 000000000000..d34c22e99225 --- /dev/null +++ b/security/ipe/policyfs.c @@ -0,0 +1,528 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ +#include "ipe.h" +#include "policy.h" +#include "fs.h" + +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/types.h> +#include <linux/dcache.h> +#include <linux/security.h> + +#define MAX_VERSION_SIZE ARRAY_SIZE("65535.65535.65535") + +/** + * find_policy: Follow the i_private field of a dentry, returning the address + * of the resulting policy structure. + * @f: Securityfs object that contains a link to the dentry containing the + * policy structure. + * + * Return: + * Always-Valid Address Pointer + */ +static inline struct ipe_policy __rcu **find_policy(struct file *f) +{ + struct dentry *link; + + link = d_inode(f->f_path.dentry)->i_private; + + return (struct ipe_policy __rcu **)&(d_inode(link)->i_private); +} + +/** + * ipefs_file: defines a file in securityfs + */ +struct ipefs_file { + const char *name; + umode_t access; + const struct file_operations *fops; +}; + +/** + * read_pkcs7: Read handler for the securityfs node, + * "ipe/policies/$name/pkcs7" + * @f: Supplies a file structure representing the securityfs node. + * @data: Suppleis a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * @data will be populated with the pkcs7 blob representing the policy + * on success. If the policy is unsigned (like the boot policy), this + * will return -ENOENT. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t read_pkcs7(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + struct ipe_policy *p = NULL; + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) + return -ENOENT; + + if (!p->pkcs7) { + rc = -ENOENT; + goto out; + } + + rc = simple_read_from_buffer(data, len, offset, p->pkcs7, p->pkcs7len); + +out: + ipe_put_policy(p); + return rc; +} + +/** + * read_policy: Read handler for the securityfs node, + * "ipe/policies/$name/policy" + * @f: Supplies a file structure representing the securityfs node. + * @data: Suppleis a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * @data will be populated with the plain-text version of the policy + * on success. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t read_policy(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + struct ipe_policy *p = NULL; + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) + return -ENOENT; + + rc = simple_read_from_buffer(data, len, offset, p->text, p->textlen); + + ipe_put_policy(p); + return rc; +} + +/** + * read_name: Read handler for the securityfs node, + * "ipe/policies/$name/name" + * @f: Supplies a file structure representing the securityfs node. + * @data: Suppleis a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * @data will be populated with the policy_name attribute on success + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t read_name(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + struct ipe_policy *p = NULL; + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) + return -ENOENT; + + rc = simple_read_from_buffer(data, len, offset, p->parsed->name, + strlen(p->parsed->name)); + + ipe_put_policy(p); + return rc; +} + +/** + * read_version: Read handler for the securityfs node, + * "ipe/policies/$name/version" + * @f: Supplies a file structure representing the securityfs node. + * @data: Suppleis a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * @data will be populated with the version string on success. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t read_version(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + ssize_t rc = 0; + size_t bufsize = 0; + struct ipe_policy *p = NULL; + char buffer[MAX_VERSION_SIZE] = { 0 }; + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) + return -ENOENT; + + bufsize = scnprintf(buffer, ARRAY_SIZE(buffer), "%hu.%hu.%hu", + p->parsed->version.major, p->parsed->version.minor, + p->parsed->version.rev); + + rc = simple_read_from_buffer(data, len, offset, buffer, bufsize); + + ipe_put_policy(p); + return rc; +} + +/** + * setactive: Write handler for the securityfs node, + * "ipe/policies/$name/active" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t setactive(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + bool value = false; + struct ipe_policy *p = NULL; + struct ipe_context *ctx = NULL; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + rc = kstrtobool_from_user(data, len, &value); + if (rc) + goto out; + + if (!value) { + rc = -EINVAL; + goto out; + } + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) { + rc = -ENOENT; + goto out; + } + + ctx = ipe_get_ctx_rcu(p->ctx); + if (!ctx) { + rc = -ENOENT; + goto out; + } + + rc = ipe_set_active_pol(p); + +out: + ipe_put_ctx(ctx); + ipe_put_policy(p); + return (rc < 0) ? rc : len; +} + +/** + * getactive: Read handler for the securityfs node, + * "ipe/policies/$name/active" + * @f: Supplies a file structure representing the securityfs node. + * @data: Suppleis a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * @data will be populated with the 1 or 0 depending on if the + * corresponding policy is active. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t getactive(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + const char *str; + struct ipe_policy *p = NULL; + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) { + rc = -ENOENT; + goto out; + } + + str = ipe_is_policy_active(p) ? "1" : "0"; + rc = simple_read_from_buffer(data, len, offset, str, 2); + +out: + ipe_put_policy(p); + return rc; +} + +/** + * update_policy: Write handler for the securityfs node, + * "ipe/policies/$name/active" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * On success this updates the policy represented by $name, + * in-place. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t update_policy(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + char *copy = NULL; + struct ipe_policy *new = NULL; + struct ipe_policy *old = NULL; + struct ipe_context *ctx = NULL; + struct ipe_policy __rcu **addr = NULL; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + ctx = ipe_current_ctx(); + if (!ctx) + return -ENOENT; + + addr = find_policy(f); + old = ipe_get_policy_rcu(*addr); + if (!old) { + rc = -ENOENT; + goto err; + } + + copy = memdup_user(data, len); + if (IS_ERR(copy)) { + rc = PTR_ERR(copy); + goto err; + } + + new = ipe_update_policy(old, NULL, 0, copy, len); + if (IS_ERR(new)) { + rc = PTR_ERR(new); + goto err; + } + + spin_lock(&ctx->lock); + rcu_assign_pointer(*addr, new); + spin_unlock(&ctx->lock); + synchronize_rcu(); + + swap(new->policyfs, old->policyfs); + + kfree(copy); + ipe_put_ctx(ctx); + ipe_put_policy(old); + return len; +err: + kfree(copy); + ipe_put_ctx(ctx); + ipe_put_policy(new); + ipe_put_policy(old); + return rc; +} + +/** + * delete_policy: write handler for securityfs dir, "ipe/policies/$name/delete" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * On success this deletes the policy represented by $name. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t delete_policy(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + bool value = false; + struct ipe_policy *p = NULL; + struct ipe_context *ctx = NULL; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + rc = kstrtobool_from_user(data, len, &value); + if (rc) + goto out; + + if (!value) { + rc = -EINVAL; + goto out; + } + + p = ipe_get_policy_rcu(*find_policy(f)); + if (!p) { + rc = -ENOENT; + goto out; + } + + if (ipe_is_policy_active(p)) { + rc = -EPERM; + goto out; + } + + ctx = ipe_get_ctx_rcu(p->ctx); + if (!ctx) { + rc = -ENOENT; + goto out; + } + + ipe_remove_policy(p); +out: + ipe_put_ctx(ctx); + ipe_put_policy(p); + return (rc < 0) ? rc : len; +} + +static const struct file_operations content_fops = { + .read = read_policy, +}; + +static const struct file_operations pkcs7_fops = { + .read = read_pkcs7, +}; + +static const struct file_operations name_fops = { + .read = read_name, +}; + +static const struct file_operations ver_fops = { + .read = read_version, +}; + +static const struct file_operations active_fops = { + .write = setactive, + .read = getactive, +}; + +static const struct file_operations update_fops = { + .write = update_policy, +}; + +static const struct file_operations delete_fops = { + .write = delete_policy, +}; + +/** + * policy_subdir: files under a policy subdirectory + */ +static const struct ipefs_file policy_subdir[] = { + { "pkcs7", 0444, &pkcs7_fops }, + { "policy", 0444, &content_fops }, + { "name", 0444, &name_fops }, + { "version", 0444, &ver_fops }, + { "active", 0600, &active_fops }, + { "update", 0200, &update_fops }, + { "delete", 0200, &delete_fops }, +}; + +/** + * soft_del_policyfs - soft delete the policyfs tree, preventing new + * accesses to the interfaces for this policy. + * @p - Policy to soft delete the tree for. + */ +static void soft_del_policyfs(struct ipe_policy *p) +{ + struct inode *ino = NULL; + struct ipe_policy __rcu **addr = NULL; + + ino = d_inode(p->policyfs); + addr = (struct ipe_policy __rcu **)&ino->i_private; + + inode_lock(ino); + rcu_assign_pointer(*addr, NULL); + inode_unlock(ino); + synchronize_rcu(); +} + +/** + * ipe_del_policyfs_node: Delete a securityfs entry for @p + * @p: Supplies a pointer to the policy to delete a securityfs entry for. + */ +void ipe_del_policyfs_node(struct ipe_policy *p) +{ + size_t i = 0; + struct dentry *d = NULL; + const struct ipefs_file *f = NULL; + + if (IS_ERR_OR_NULL(p->policyfs)) + return; + + soft_del_policyfs(p); + + for (i = 0; i < ARRAY_SIZE(policy_subdir); ++i) { + f = &policy_subdir[i]; + + d = lookup_positive_unlocked(f->name, p->policyfs, + strlen(f->name)); + if (IS_ERR(d)) + continue; + + securityfs_remove(d); + dput(d); + } + + securityfs_remove(p->policyfs); +} + +/** + * ipe_new_policyfs_node: Create a securityfs entry for @p + * @ctx: Supplies a pointer to a context structure that contains the root of + * the policy tree. + * @p: Supplies a pointer to the policy to create a securityfs entry for. + * + * Return: + * 0 - OK + * !0 - Error + */ +int ipe_new_policyfs_node(struct ipe_context *ctx, struct ipe_policy *p) +{ + int rc = 0; + size_t i = 0; + struct dentry *d = NULL; + struct ipe_policy **addr = NULL; + const struct ipefs_file *f = NULL; + + p->policyfs = securityfs_create_dir(p->parsed->name, ctx->policy_root); + if (IS_ERR(p->policyfs)) { + rc = PTR_ERR(p->policyfs); + goto err; + } + + addr = (struct ipe_policy **)&(d_inode(p->policyfs)->i_private); + *addr = p; + + for (i = 0; i < ARRAY_SIZE(policy_subdir); ++i) { + f = &policy_subdir[i]; + + d = securityfs_create_file(f->name, f->access, p->policyfs, p->policyfs, + f->fops); + if (IS_ERR(d)) { + rc = PTR_ERR(d); + goto err; + } + } + + return 0; +err: + ipe_del_policyfs_node(p); + return rc; +} -- 2.33.0

On 10/13/2021 12:06 PM, deven.desai(a)linux.microsoft.com wrote: Please stick with the lsmname_hook_name convention, as you did with ipe_task_alloc and ipe_task_free. Anyone who is looking at more than one LSM is going to have a much harder time working with your code the way you have it. Think % find security | xargs grep '_bprm_check_security('

Possible problem here. If someone (like me) adds a new file type and forgets to add a case, there will be an out of bound access in evaluate(): rules = &pol->parsed->rules[ctx->op]; due to the static definition of the rules array in the ipe_parsed_policy structure (array length: ipe_operation_max). Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua

Ok, will do a test with your new version of the patch set. Thanks Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua

From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; Users of IPE require a way to identify when and why an operation fails, allowing them to both respond to violations of policy and be notified of potentially malicious actions on their systens with respect to IPE itself. Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Split up patch 02/12 into four parts: 1. context creation [01/16] 2. audit [07/16] (this patch) 3. evaluation loop [03/16] 4. access control hooks [05/16] --- security/ipe/Kconfig | 52 ++++++ security/ipe/Makefile | 2 + security/ipe/audit.c | 264 ++++++++++++++++++++++++++++++ security/ipe/audit.h | 36 ++++ security/ipe/ctx.c | 18 ++ security/ipe/ctx.h | 2 + security/ipe/eval.c | 8 + security/ipe/eval.h | 7 + security/ipe/fs.c | 79 +++++++++ security/ipe/modules/ipe_module.h | 2 + 10 files changed, 470 insertions(+) create mode 100644 security/ipe/audit.c create mode 100644 security/ipe/audit.h diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig index c4503083e92d..ef556b66e674 100644 --- a/security/ipe/Kconfig +++ b/security/ipe/Kconfig @@ -17,3 +17,55 @@ menuconfig SECURITY_IPE requirements on the fly. If unsure, answer N. + +if SECURITY_IPE + +choice + prompt "Hash algorithm used in auditing policies" + default IPE_AUDIT_HASH_SHA1 + depends on AUDIT + help + Specify the hash algorithm used when auditing policies. + The hash is used to uniquely identify a policy from other + policies on the system. + + If unsure, leave default. + + config IPE_AUDIT_HASH_SHA1 + bool "sha1" + depends on CRYPTO_SHA1 + help + Use the SHA128 algorithm to hash policies + in the audit records. + + config IPE_AUDIT_HASH_SHA256 + bool "sha256" + depends on CRYPTO_SHA256 + help + Use the SHA256 algorithm to hash policies + in the audit records. + + config IPE_AUDIT_HASH_SHA384 + bool "sha384" + depends on CRYPTO_SHA512 + help + Use the SHA384 algorithm to hash policies + in the audit records + + config IPE_AUDIT_HASH_SHA512 + bool "sha512" + depends on CRYPTO_SHA512 + help + Use the SHA512 algorithm to hash policies + in the audit records +endchoice + +config IPE_AUDIT_HASH_ALG + string + depends on AUDIT + default "sha1" if IPE_AUDIT_HASH_SHA1 + default "sha256" if IPE_AUDIT_HASH_SHA256 + default "sha384" if IPE_AUDIT_HASH_SHA384 + default "sha512" if IPE_AUDIT_HASH_SHA512 + +endif diff --git a/security/ipe/Makefile b/security/ipe/Makefile index d5660a17364c..6d9ac818e8c6 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -18,3 +18,5 @@ obj-$(CONFIG_SECURITY_IPE) += \ parsers.o \ policy.o \ policyfs.o \ + +obj-$(CONFIG_AUDIT) += audit.o diff --git a/security/ipe/audit.c b/security/ipe/audit.c new file mode 100644 index 000000000000..5f6c0a52b0cb --- /dev/null +++ b/security/ipe/audit.c @@ -0,0 +1,264 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "eval.h" +#include "hooks.h" +#include "policy.h" +#include "audit.h" +#include "modules/ipe_module.h" + +#include <linux/slab.h> +#include <linux/audit.h> +#include <linux/types.h> +#include <crypto/hash.h> + +#define NULLSTR(x) ((x) == NULL ? "NULL" : "!NULL") +#define ACTSTR(x) ((x) == ipe_action_allow ? "ALLOW" : "DENY") + +#define POLICY_LOAD_FMT "IPE policy_name=%s policy_version=%hu.%hu.%hu "\ + CONFIG_IPE_AUDIT_HASH_ALG "=" + +static const char *const audit_hook_names[ipe_hook_max] = { + "EXECVE", + "MMAP", + "MPROTECT", + "KERNEL_READ", + "KERNEL_LOAD", +}; + +static const char *const audit_op_names[ipe_operation_max] = { + "EXECUTE", + "FIRMWARE", + "KMODULE", + "KEXEC_IMAGE", + "KEXEC_INITRAMFS", + "IMA_X509_CERT", + "IMA_POLICY", +}; + +/** + * audit_pathname: retrieve the absoute path to a file being evaluated. + * @f: File to retrieve the absolute path for. + * + * This function walks past symlinks and mounts. + * + * Return: + * !IS_ERR - OK + */ +static char *audit_pathname(const struct file *f) +{ + int rc = 0; + char *pos = NULL; + char *pathbuf = NULL; + char *temp_path = NULL; + + if (IS_ERR_OR_NULL(f)) + return ERR_PTR(-ENOENT); + + pathbuf = __getname(); + if (!pathbuf) + return ERR_PTR(-ENOMEM); + + pos = d_absolute_path(&f->f_path, pathbuf, PATH_MAX); + if (IS_ERR(pos)) { + rc = PTR_ERR(pos); + goto err; + } + + temp_path = __getname(); + if (!temp_path) { + rc = -ENOMEM; + goto err; + } + + strscpy(temp_path, pos, PATH_MAX); + __putname(pathbuf); + + return temp_path; +err: + __putname(pathbuf); + return ERR_PTR(rc); +} + +/** + * audit_eval_ctx: audit an evaluation context structure. + * @ab: Supplies a poniter to the audit_buffer to append to. + * @ctx: Supplies a pointer to the evaluation context to audit + * @enforce: Supplies a boolean representing the enforcement state + */ +static void audit_eval_ctx(struct audit_buffer *ab, + const struct ipe_eval_ctx *const ctx, bool enforce) +{ + char *abspath = NULL; + + audit_log_format(ab, "ctx_pid=%d ", task_tgid_nr(current)); + audit_log_format(ab, "ctx_op=%s ", audit_op_names[ctx->op]); + audit_log_format(ab, "ctx_hook=%s ", audit_hook_names[ctx->hook]); + audit_log_format(ab, "ctx_ns_enforce=%d ", enforce); + audit_log_format(ab, "ctx_comm="); + audit_log_n_untrustedstring(ab, current->comm, ARRAY_SIZE(current->comm)); + audit_log_format(ab, " "); + + /* best effort */ + if (ctx->file) { + abspath = audit_pathname(ctx->file); + if (!IS_ERR(abspath)) { + audit_log_format(ab, "ctx_pathname="); + audit_log_n_untrustedstring(ab, abspath, PATH_MAX); + __putname(abspath); + } + + audit_log_format(ab, " ctx_ino=%ld ctx_dev=%s", + ctx->file->f_inode->i_ino, + ctx->file->f_inode->i_sb->s_id); + } +} + +/** + * audit_rule: audit an IPE policy rule approximation. + * @ab: Supplies a poniter to the audit_buffer to append to. + * @r: Supplies a pointer to the ipe_rule to approximate a string form for. + * + * This is an approximation because aliases like "KERNEL_READ" will be + * emitted in their expanded form. + */ +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r) +{ + const struct ipe_policy_mod *ptr; + + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]); + + list_for_each_entry(ptr, &r->modules, next) { + audit_log_format(ab, "%s=", ptr->mod->name); + + ptr->mod->audit(ab, ptr->mod_value); + + audit_log_format(ab, " "); + } + + audit_log_format(ab, "action=%s\"", ACTSTR(r->action)); +} + +/** + * ipe_audit_match: audit a match for IPE policy. + * @ctx: Supplies a poniter to the evaluation context that was used in the + * evaluation. + * @match_type: Supplies the scope of the match: rule, operation default, + * global default. + * @act: Supplies the IPE's evaluation decision, deny or allow. + * @r: Supplies a pointer to the rule that was matched, if possible. + * @enforce: Supplies the enforcement/permissive state at the point + * the enforcement decision was made. + */ +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action act, const struct ipe_rule *const r, + bool enforce) +{ + struct audit_buffer *ab; + bool success_audit; + + rcu_read_lock(); + success_audit = READ_ONCE(ctx->ci_ctx->success_audit); + rcu_read_unlock(); + + if (act != ipe_action_deny && !success_audit) + return; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TRUST_RESULT); + if (!ab) + return; + + audit_log_format(ab, "IPE "); + audit_eval_ctx(ab, ctx, enforce); + audit_log_format(ab, " "); + + if (match_type == ipe_match_rule) + audit_rule(ab, r); + else if (match_type == ipe_match_table) + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", + audit_op_names[ctx->op], ACTSTR(act)); + else + audit_log_format(ab, "rule=\"DEFAULT action=%s\"", + ACTSTR(act)); + + audit_log_end(ab); +} + +/** + * audit_policy: Audit a policy's name, version and thumprint to @ab + * @ab: Supplies a pointer to the audit buffer to append to. + * @p: Supplies a pointer to the policy to audit + */ +static void audit_policy(struct audit_buffer *ab, + const struct ipe_policy *const p) +{ + u8 *digest = NULL; + struct crypto_shash *tfm; + SHASH_DESC_ON_STACK(desc, tfm); + + tfm = crypto_alloc_shash(CONFIG_IPE_AUDIT_HASH_ALG, 0, 0); + if (IS_ERR(tfm)) + return; + + desc->tfm = tfm; + + digest = kzalloc(crypto_shash_digestsize(tfm), GFP_KERNEL); + if (!digest) + goto out; + + if (crypto_shash_init(desc)) + goto out; + + if (crypto_shash_update(desc, p->pkcs7, p->pkcs7len)) + goto out; + + if (crypto_shash_final(desc, digest)) + goto out; + + audit_log_format(ab, POLICY_LOAD_FMT, p->parsed->name, + p->parsed->version.major, p->parsed->version.minor, + p->parsed->version.rev); + audit_log_n_hex(ab, digest, crypto_shash_digestsize(tfm)); + +out: + kfree(digest); + crypto_free_shash(tfm); +} + +/** + * ipe_audit_policy_activation: Audit a policy being made the active policy. + * @p: Supplies a pointer to the policy to audit + */ +void ipe_audit_policy_activation(const struct ipe_policy *const p) +{ + struct audit_buffer *ab; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TRUST_POLICY_ACTIVATE); + if (!ab) + return; + + audit_policy(ab, p); + + audit_log_end(ab); +} + +/** + * ipe_audit_policy_load: Audit a policy being loaded into the kernel. + * @p: Supplies a pointer to the policy to audit + */ +void ipe_audit_policy_load(const struct ipe_policy *const p) +{ + struct audit_buffer *ab; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TRUST_POLICY_LOAD); + if (!ab) + return; + + audit_policy(ab, p); + + audit_log_end(ab); +} diff --git a/security/ipe/audit.h b/security/ipe/audit.h new file mode 100644 index 000000000000..6b6880f6e8e7 --- /dev/null +++ b/security/ipe/audit.h @@ -0,0 +1,36 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#ifndef IPE_AUDIT_H +#define IPE_AUDIT_H + +#include "ipe.h" +#include "eval.h" + +#ifdef CONFIG_AUDIT +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action act, const struct ipe_rule *const r, + bool enforce); +void ipe_audit_policy_load(const struct ipe_policy *const p); +void ipe_audit_policy_activation(const struct ipe_policy *const p); +#else +static inline void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action act, const struct ipe_rule *const r, + bool enforce) +{ +} + +static inline void ipe_audit_policy_load(const struct ipe_policy *const p) +{ +} + +static inline void ipe_audit_policy_activation(const struct ipe_policy *const p) +{ +} +#endif /* CONFIG_AUDIT */ + +#endif /* IPE_AUDIT_H */ diff --git a/security/ipe/ctx.c b/security/ipe/ctx.c index 664c671a4f9c..77475aedbfe9 100644 --- a/security/ipe/ctx.c +++ b/security/ipe/ctx.c @@ -6,12 +6,16 @@ #include "ipe.h" #include "ctx.h" #include "policy.h" +#include "audit.h" #include <linux/slab.h> #include <linux/types.h> #include <linux/parser.h> #include <linux/refcount.h> #include <linux/spinlock.h> +#include <linux/moduleparam.h> + +static bool success_audit; /** * ver_to_u64: convert an internal ipe_policy_version to a u64 @@ -265,6 +269,7 @@ int ipe_set_active_pol(const struct ipe_policy *p) spin_unlock(&ctx->lock); synchronize_rcu(); + ipe_audit_policy_activation(p); out: ipe_put_policy(ap); ipe_put_ctx(ctx); @@ -330,6 +335,10 @@ int __init ipe_init_ctx(void) goto err; } + spin_lock(&lns->lock); + WRITE_ONCE(lns->success_audit, success_audit); + spin_unlock(&lns->lock); + rcu_assign_pointer(*ipe_tsk_ctx(current), lns); return 0; @@ -337,3 +346,12 @@ int __init ipe_init_ctx(void) ipe_put_ctx(lns); return rc; } + +/* Set the right module name */ +#ifdef KBUILD_MODNAME +#undef KBUILD_MODNAME +#define KBUILD_MODNAME "ipe" +#endif + +module_param(success_audit, bool, 0400); +MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled"); diff --git a/security/ipe/ctx.h b/security/ipe/ctx.h index fe11fb767788..31aea2fb9e49 100644 --- a/security/ipe/ctx.h +++ b/security/ipe/ctx.h @@ -15,6 +15,8 @@ struct ipe_context { struct ipe_policy __rcu *active_policy; + bool __rcu success_audit; + refcount_t refcount; /* Protects concurrent writers */ spinlock_t lock; diff --git a/security/ipe/eval.c b/security/ipe/eval.c index b732f76cfd05..dcb62179e4bf 100644 --- a/security/ipe/eval.c +++ b/security/ipe/eval.c @@ -9,6 +9,7 @@ #include "hooks.h" #include "policy.h" #include "modules/ipe_module.h" +#include "audit.h" #include <linux/slab.h> #include <linux/file.h> @@ -73,7 +74,9 @@ static int evaluate(const struct ipe_eval_ctx *const ctx) { int rc = 0; bool match = false; + bool enforcing = true; enum ipe_action action; + enum ipe_match match_type; struct ipe_policy *pol = NULL; const struct ipe_rule *rule = NULL; const struct ipe_policy_mod *module = NULL; @@ -97,12 +100,17 @@ static int evaluate(const struct ipe_eval_ctx *const ctx) if (match) { action = rule->action; + match_type = ipe_match_rule; } else if (rules->default_action != ipe_action_max) { action = rules->default_action; + match_type = ipe_match_table; } else { action = pol->parsed->global_default; + match_type = ipe_match_global; } + ipe_audit_match(ctx, match_type, action, rule, enforcing); + if (action == ipe_action_deny) rc = -EACCES; diff --git a/security/ipe/eval.h b/security/ipe/eval.h index db6da2998a20..8c08eed5af2b 100644 --- a/security/ipe/eval.h +++ b/security/ipe/eval.h @@ -20,6 +20,13 @@ struct ipe_eval_ctx { struct ipe_context *ci_ctx; }; +enum ipe_match { + ipe_match_rule = 0, + ipe_match_table, + ipe_match_global, + ipe_match_max +}; + int ipe_process_event(const struct file *file, enum ipe_operation op, enum ipe_hook hook); diff --git a/security/ipe/fs.c b/security/ipe/fs.c index 10ad23f8bf92..c202c0753755 100644 --- a/security/ipe/fs.c +++ b/security/ipe/fs.c @@ -5,6 +5,7 @@ #include "ipe.h" #include "fs.h" #include "policy.h" +#include "audit.h" #include <linux/dcache.h> #include <linux/security.h> @@ -12,6 +13,70 @@ static struct dentry *np __ro_after_init; static struct dentry *root __ro_after_init; static struct dentry *config __ro_after_init; +static struct dentry *success_audit __ro_after_init; + +/** + * setaudit: Write handler for the securityfs node, "ipe/success_audit" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t setaudit(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + bool value; + struct ipe_context *ctx; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + rc = kstrtobool_from_user(data, len, &value); + if (rc) + return rc; + + ctx = ipe_current_ctx(); + + spin_lock(&ctx->lock); + WRITE_ONCE(ctx->success_audit, value); + spin_unlock(&ctx->lock); + synchronize_rcu(); + + ipe_put_ctx(ctx); + return len; +} + +/** + * getaudit: Read handler for the securityfs node, "ipe/success_audit" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the read syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t getaudit(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + const char *result; + struct ipe_context *ctx; + + ctx = ipe_current_ctx(); + + rcu_read_lock(); + result = ((READ_ONCE(ctx->success_audit)) ? "1" : "0"); + rcu_read_unlock(); + + ipe_put_ctx(ctx); + return simple_read_from_buffer(data, len, offset, result, 2); +} /** * new_policy: Write handler for the securityfs node, "ipe/new_policy" @@ -54,6 +119,7 @@ static ssize_t new_policy(struct file *f, const char __user *data, goto err; ipe_add_policy(ctx, p); + ipe_audit_policy_load(p); err: ipe_put_policy(p); ipe_put_ctx(ctx); @@ -119,6 +185,11 @@ static const struct file_operations np_fops = { .write = new_policy, }; +static const struct file_operations audit_fops = { + .write = setaudit, + .read = getaudit, +}; + /** * ipe_init_securityfs: Initialize IPE's securityfs tree at fsinit * @@ -152,6 +223,13 @@ static int __init ipe_init_securityfs(void) goto err; } + success_audit = securityfs_create_file("success_audit", 0600, root, + NULL, &audit_fops); + if (IS_ERR(success_audit)) { + rc = PTR_ERR(success_audit); + goto err; + } + ctx->policy_root = securityfs_create_dir("policies", root); if (IS_ERR(ctx->policy_root)) { rc = PTR_ERR(ctx->policy_root); @@ -163,6 +241,7 @@ static int __init ipe_init_securityfs(void) securityfs_remove(np); securityfs_remove(root); securityfs_remove(config); + securityfs_remove(success_audit); securityfs_remove(ctx->policy_root); return rc; } diff --git a/security/ipe/modules/ipe_module.h b/security/ipe/modules/ipe_module.h index b4f975e9218a..6855815d72da 100644 --- a/security/ipe/modules/ipe_module.h +++ b/security/ipe/modules/ipe_module.h @@ -6,6 +6,7 @@ #define IPE_MODULE_H #include <linux/types.h> +#include <linux/audit.h> #include "../eval.h" /** @@ -26,6 +27,7 @@ struct ipe_module { int (*free)(void **value); /* optional */ bool (*eval)(const struct ipe_eval_ctx *ctx, /* required */ const void *val); + void (*audit)(struct audit_buffer *ab, const void *val); /* required */ }; #define IPE_MODULE(parser) \ -- 2.33.0

On 10/13/2021 3:54 PM, Randy Dunlap wrote: Oof. That's embarrassing. Sorry, I'll fix this for v8. While I'm at it, is the help text required for choice configs? checkpatch --strict complains with a warning without them, but I see other places in the tree where help text is omitted for these configs attached to a choice. Documentation/process/* doesn't seem to have any guidance, nor Documentation/kbuild/* on whether it is safe to ignore that checkpatch warning.

On 10/15/2021 12:50 PM, Randy Dunlap wrote: I added the help text to keep it from complaining (and added it incorrectly, clearly). Alright. I think the choice guidance is pretty clear: Specify the hash algorithm used when auditing policies. The hash is used to uniquely identify a policy from other policies on the system. So I'll remove the help text for these choices. At worst, I can make the choice text more clear.

From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; IPE is designed to provide system level trust guarantees, this usually implies that trust starts from bootup with a hardware root of trust, which validates the bootloader. After this, the bootloader verifies the kernel and the initramfs. As there's no currently supported integrity method for initramfs, and it's typically already verified by the bootloader, introduce a property that causes the first superblock to have an execution to be "pinned", which is typically initramfs. Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Reword and refactor patch 04/12 to [09/16] --- security/ipe/Kconfig | 2 + security/ipe/Makefile | 1 + security/ipe/eval.c | 71 ++++++++++++++++++++++++++++ security/ipe/eval.h | 5 ++ security/ipe/hooks.c | 14 ++++++ security/ipe/hooks.h | 2 + security/ipe/ipe.c | 1 + security/ipe/modules.c | 25 ++++++++++ security/ipe/modules/Kconfig | 20 ++++++++ security/ipe/modules/Makefile | 8 ++++ security/ipe/modules/boot_verified.c | 24 ++++++++++ security/ipe/modules/ipe_module.h | 2 + 12 files changed, 175 insertions(+) create mode 100644 security/ipe/modules/Kconfig create mode 100644 security/ipe/modules/Makefile create mode 100644 security/ipe/modules/boot_verified.c diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig index ef556b66e674..fcf82a8152ec 100644 --- a/security/ipe/Kconfig +++ b/security/ipe/Kconfig @@ -68,4 +68,6 @@ config IPE_AUDIT_HASH_ALG default "sha384" if IPE_AUDIT_HASH_SHA384 default "sha512" if IPE_AUDIT_HASH_SHA512 +source "security/ipe/modules/Kconfig" + endif diff --git a/security/ipe/Makefile b/security/ipe/Makefile index 6d9ac818e8c6..1e7b2d7fcd9e 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -13,6 +13,7 @@ obj-$(CONFIG_SECURITY_IPE) += \ fs.o \ hooks.o \ ipe.o \ + modules/ \ modules.o \ parsers/ \ parsers.o \ diff --git a/security/ipe/eval.c b/security/ipe/eval.c index e520ce521c05..361efccebad4 100644 --- a/security/ipe/eval.c +++ b/security/ipe/eval.c @@ -11,10 +11,62 @@ #include "modules/ipe_module.h" #include "audit.h" +#include <linux/fs.h> +#include <linux/types.h> #include <linux/slab.h> #include <linux/file.h> #include <linux/sched.h> #include <linux/rcupdate.h> +#include <linux/spinlock.h> + +static struct super_block *pinned_sb; +static DEFINE_SPINLOCK(pin_lock); + +#define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb) + +/** + * pin_sb: pin the underlying superblock of @f, marking it as trusted + * @f: Supplies a file structure to source the super_block from. + */ +static void pin_sb(const struct file *f) +{ + if (!f) + return; + + spin_lock(&pin_lock); + + if (pinned_sb) + goto out; + + pinned_sb = FILE_SUPERBLOCK(f); + +out: + spin_unlock(&pin_lock); +} + +/** + * from_pinned: determine whether @f is source from the pinned super_block. + * @f: Supplies a file structure to check against the pinned super_block. + * + * Return: + * true - @f is sourced from the pinned super_block + * false - @f is not sourced from the pinned super_block + */ +static bool from_pinned(const struct file *f) +{ + bool rv; + + if (!f) + return false; + + spin_lock(&pin_lock); + + rv = !IS_ERR_OR_NULL(pinned_sb) && pinned_sb == FILE_SUPERBLOCK(f); + + spin_unlock(&pin_lock); + + return rv; +} /** * build_ctx: Build an evaluation context. @@ -42,6 +94,7 @@ static struct ipe_eval_ctx *build_ctx(const struct file *file, ctx->op = op; ctx->hook = hook; ctx->ci_ctx = ipe_current_ctx(); + ctx->from_init_sb = from_pinned(file); return ctx; } @@ -145,6 +198,9 @@ int ipe_process_event(const struct file *file, enum ipe_operation op, int rc = 0; struct ipe_eval_ctx *ctx = NULL; + if (op == ipe_operation_exec) + pin_sb(file); + ctx = build_ctx(file, op, hook); if (IS_ERR(ctx)) return PTR_ERR(ctx); @@ -154,3 +210,18 @@ int ipe_process_event(const struct file *file, enum ipe_operation op, free_ctx(ctx); return rc; } + +/** + * ipe_invalidate_pinned_sb: if @mnt_sb is the pinned superblock, ensure + * nothing can match it again. + * @mnt_sb: super_block to check against the pinned super_block + */ +void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb) +{ + spin_lock(&pin_lock); + + if (!IS_ERR_OR_NULL(pinned_sb) && mnt_sb == pinned_sb) + pinned_sb = ERR_PTR(-EIO); + + spin_unlock(&pin_lock); +} diff --git a/security/ipe/eval.h b/security/ipe/eval.h index 8c08eed5af2b..42fb7fdf2599 100644 --- a/security/ipe/eval.h +++ b/security/ipe/eval.h @@ -7,6 +7,7 @@ #define IPE_EVAL_H #include <linux/file.h> +#include <linux/types.h> #include "ctx.h" #include "hooks.h" @@ -18,6 +19,8 @@ struct ipe_eval_ctx { const struct file *file; struct ipe_context *ci_ctx; + + bool from_init_sb; }; enum ipe_match { @@ -30,4 +33,6 @@ enum ipe_match { int ipe_process_event(const struct file *file, enum ipe_operation op, enum ipe_hook hook); +void ipe_invalidate_pinned_sb(const struct super_block *mnt_sb); + #endif /* IPE_EVAL_H */ diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c index 216242408a80..2d4a4f0eead0 100644 --- a/security/ipe/hooks.c +++ b/security/ipe/hooks.c @@ -205,3 +205,17 @@ int ipe_on_kernel_load_data(enum kernel_load_data_id id, bool contents) return ipe_process_event(NULL, op, ipe_hook_kernel_load); } + +/** + * ipe_bdev_free_security: free nested structures within IPE's LSM blob + * in super_blocks + * @mnt_sb: Supplies a pointer to a super_block that contains the structure + * to free. + * + * IPE does not have any structures with mnt_sb, but uses this hook to + * invalidate a pinned super_block. + */ +void ipe_sb_free_security(struct super_block *mnt_sb) +{ + ipe_invalidate_pinned_sb(mnt_sb); +} diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h index c99a0b7f45f7..e7f107ab5620 100644 --- a/security/ipe/hooks.h +++ b/security/ipe/hooks.h @@ -38,4 +38,6 @@ int ipe_on_kernel_read(struct file *file, enum kernel_read_file_id id, int ipe_on_kernel_load_data(enum kernel_load_data_id id, bool contents); +void ipe_sb_free_security(struct super_block *mnt_sb); + #endif /* IPE_HOOKS_H */ diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c index 3f9d43783293..1382d50078ec 100644 --- a/security/ipe/ipe.c +++ b/security/ipe/ipe.c @@ -30,6 +30,7 @@ static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(file_mprotect, ipe_on_mprotect), LSM_HOOK_INIT(kernel_read_file, ipe_on_kernel_read), LSM_HOOK_INIT(kernel_load_data, ipe_on_kernel_load_data), + LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security), }; /** diff --git a/security/ipe/modules.c b/security/ipe/modules.c index fb100c14cce5..3aa9a38fdc0d 100644 --- a/security/ipe/modules.c +++ b/security/ipe/modules.c @@ -107,3 +107,28 @@ int ipe_register_module(struct ipe_module *m) return 0; } + +/** + * ipe_bool_parse: parse a boolean in IPE's policy and associate + * it as @value in IPE's policy. + * @valstr: Supplies the string parsed from the policy + * @value: Supplies a pointer to be populated with the result. + * + * Modules can use this function for simple true/false values + * instead of defining their own. + * + * Return: + * 0 - OK + * !0 - Error + */ +int ipe_bool_parse(const char *valstr, void **value) +{ + if (!strcmp(valstr, "TRUE")) + *value = (void *)true; + else if (!strcmp(valstr, "FALSE")) + *value = (void *)false; + else + return -EBADMSG; + + return 0; +} diff --git a/security/ipe/modules/Kconfig b/security/ipe/modules/Kconfig new file mode 100644 index 000000000000..fad96ba534e2 --- /dev/null +++ b/security/ipe/modules/Kconfig @@ -0,0 +1,20 @@ + +menu "IPE Trust Providers" + +config IPE_PROP_BOOT_VERIFIED + bool "Enable trust for initramfs" + depends on SECURITY_IPE + default N + help + This option enables the property 'boot_verified' in IPE policy. + This property 'pins' the initial superblock when something + is evaluated as an execution. This property will evaluate + to true when the file being evaluated originates from this + superblock. + + This property is useful to authorize a signed initramfs. + + If unsure, answer N. + + +endmenu diff --git a/security/ipe/modules/Makefile b/security/ipe/modules/Makefile new file mode 100644 index 000000000000..e0045ec65434 --- /dev/null +++ b/security/ipe/modules/Makefile @@ -0,0 +1,8 @@ +# SPDX-License-Identifier: GPL-2.0 +# +# Copyright (C) Microsoft Corporation. All rights reserved. +# +# Makefile for building the IPE module as part of the kernel tree. +# + +obj-$(CONFIG_IPE_PROP_BOOT_VERIFIED) += boot_verified.o diff --git a/security/ipe/modules/boot_verified.c b/security/ipe/modules/boot_verified.c new file mode 100644 index 000000000000..3ab944a485c6 --- /dev/null +++ b/security/ipe/modules/boot_verified.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe_module.h" + +#include <linux/fs.h> +#include <linux/types.h> + +static bool bv_eval(const struct ipe_eval_ctx *ctx, const void *val) +{ + bool expect = (bool)val; + + return expect == ctx->from_init_sb; +} + +IPE_MODULE(bv) = { + .name = "boot_verified", + .version = 1, + .parse = ipe_bool_parse, + .free = NULL, + .eval = bv_eval, +}; diff --git a/security/ipe/modules/ipe_module.h b/security/ipe/modules/ipe_module.h index 6855815d72da..08835627bd72 100644 --- a/security/ipe/modules/ipe_module.h +++ b/security/ipe/modules/ipe_module.h @@ -9,6 +9,8 @@ #include <linux/audit.h> #include "../eval.h" +int ipe_bool_parse(const char *valstr, void **value); + /** * ipe_module: definition of an extensible module for IPE properties. * These structures are used to implement 'key=value' pairs -- 2.33.0

From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; Allows author of IPE policy to indicate trust for a singular dm-verity volume, identified by roothash, through "dmverity_roothash" and all signed dm-verity volumes, through "dmverity_signature". Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Squash patch 08/12, 10/12 to [11/16] --- security/ipe/eval.c | 5 ++ security/ipe/eval.h | 10 +++ security/ipe/hooks.c | 48 ++++++++++++++ security/ipe/hooks.h | 6 ++ security/ipe/ipe.c | 9 +++ security/ipe/ipe.h | 3 + security/ipe/modules/Kconfig | 23 +++++++ security/ipe/modules/Makefile | 2 + security/ipe/modules/dmverity_roothash.c | 80 +++++++++++++++++++++++ security/ipe/modules/dmverity_signature.c | 25 +++++++ 10 files changed, 211 insertions(+) create mode 100644 security/ipe/modules/dmverity_roothash.c create mode 100644 security/ipe/modules/dmverity_signature.c diff --git a/security/ipe/eval.c b/security/ipe/eval.c index 361efccebad4..facc05c753f4 100644 --- a/security/ipe/eval.c +++ b/security/ipe/eval.c @@ -23,6 +23,7 @@ static struct super_block *pinned_sb; static DEFINE_SPINLOCK(pin_lock); #define FILE_SUPERBLOCK(f) ((f)->f_path.mnt->mnt_sb) +#define FILE_BLOCK_DEV(f) (FILE_SUPERBLOCK(f)->s_bdev) /** * pin_sb: pin the underlying superblock of @f, marking it as trusted @@ -95,6 +96,10 @@ static struct ipe_eval_ctx *build_ctx(const struct file *file, ctx->hook = hook; ctx->ci_ctx = ipe_current_ctx(); ctx->from_init_sb = from_pinned(file); + if (file) { + if (FILE_BLOCK_DEV(file)) + ctx->ipe_bdev = ipe_bdev(FILE_BLOCK_DEV(file)); + } return ctx; } diff --git a/security/ipe/eval.h b/security/ipe/eval.h index 42fb7fdf2599..25d2d8d55702 100644 --- a/security/ipe/eval.h +++ b/security/ipe/eval.h @@ -13,6 +13,14 @@ #include "hooks.h" #include "policy.h" +struct ipe_bdev { + const u8 *sigdata; + size_t siglen; + + const u8 *hash; + size_t hashlen; +}; + struct ipe_eval_ctx { enum ipe_hook hook; enum ipe_operation op; @@ -20,6 +28,8 @@ struct ipe_eval_ctx { const struct file *file; struct ipe_context *ci_ctx; + const struct ipe_bdev *ipe_bdev; + bool from_init_sb; }; diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c index 2d4a4f0eead0..470fb48e490c 100644 --- a/security/ipe/hooks.c +++ b/security/ipe/hooks.c @@ -13,6 +13,7 @@ #include <linux/types.h> #include <linux/refcount.h> #include <linux/rcupdate.h> +#include <linux/blk_types.h> #include <linux/binfmts.h> #include <linux/mman.h> @@ -219,3 +220,50 @@ void ipe_sb_free_security(struct super_block *mnt_sb) { ipe_invalidate_pinned_sb(mnt_sb); } + +/** + * ipe_bdev_free_security: free nested structures within IPE's LSM blob + * in block_devices + * @bdev: Supplies a pointer to a block_device that contains the structure + * to free. + */ +void ipe_bdev_free_security(struct block_device *bdev) +{ + struct ipe_bdev *blob = ipe_bdev(bdev); + + kfree(blob->sigdata); +} + +/** + * ipe_bdev_setsecurity: associate some data from the block device layer + * with IPE's LSM blob. + * @bdev: Supplies a pointer to a block_device that contains the LSM blob. + * @key: Supplies the string key that uniquely identifies the value. + * @value: Supplies the value to store. + * @len: The length of @value. + */ +int ipe_bdev_setsecurity(struct block_device *bdev, const char *key, + const void *value, size_t len) +{ + struct ipe_bdev *blob = ipe_bdev(bdev); + + if (!strcmp(key, DM_VERITY_SIGNATURE_SEC_NAME)) { + blob->siglen = len; + blob->sigdata = kmemdup(value, len, GFP_KERNEL); + if (!blob->sigdata) + return -ENOMEM; + + return 0; + } + + if (!strcmp(key, DM_VERITY_ROOTHASH_SEC_NAME)) { + blob->hashlen = len; + blob->hash = kmemdup(value, len, GFP_KERNEL); + if (!blob->hash) + return -ENOMEM; + + return 0; + } + + return -ENOSYS; +} diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h index e7f107ab5620..285f35187188 100644 --- a/security/ipe/hooks.h +++ b/security/ipe/hooks.h @@ -10,6 +10,7 @@ #include <linux/sched.h> #include <linux/binfmts.h> #include <linux/security.h> +#include <linux/device-mapper.h> enum ipe_hook { ipe_hook_exec = 0, @@ -40,4 +41,9 @@ int ipe_on_kernel_load_data(enum kernel_load_data_id id, bool contents); void ipe_sb_free_security(struct super_block *mnt_sb); +void ipe_bdev_free_security(struct block_device *bdev); + +int ipe_bdev_setsecurity(struct block_device *bdev, const char *key, + const void *value, size_t len); + #endif /* IPE_HOOKS_H */ diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c index 1382d50078ec..215936cb4574 100644 --- a/security/ipe/ipe.c +++ b/security/ipe/ipe.c @@ -9,6 +9,7 @@ #include "ipe_parser.h" #include "modules/ipe_module.h" #include "modules.h" +#include "eval.h" #include <linux/fs.h> #include <linux/sched.h> @@ -20,8 +21,14 @@ struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = { .lbs_task = sizeof(struct ipe_context __rcu *), + .lbs_bdev = sizeof(struct ipe_bdev), }; +struct ipe_bdev *ipe_bdev(struct block_device *b) +{ + return b->security + ipe_blobs.lbs_bdev; +} + static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(task_alloc, ipe_task_alloc), LSM_HOOK_INIT(task_free, ipe_task_free), @@ -31,6 +38,8 @@ static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(kernel_read_file, ipe_on_kernel_read), LSM_HOOK_INIT(kernel_load_data, ipe_on_kernel_load_data), LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security), + LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security), + LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity), }; /** diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h index ad16d2bebfec..6b4c7e07f204 100644 --- a/security/ipe/ipe.h +++ b/security/ipe/ipe.h @@ -14,10 +14,13 @@ #include <linux/types.h> #include <linux/sched.h> +#include <linux/blk_types.h> #include <linux/lsm_hooks.h> extern struct lsm_blob_sizes ipe_blobs; extern struct ipe_parser __start_ipe_parsers[], __end_ipe_parsers[]; extern struct ipe_module __start_ipe_modules[], __end_ipe_modules[]; +struct ipe_bdev *ipe_bdev(struct block_device *b); + #endif /* IPE_H */ diff --git a/security/ipe/modules/Kconfig b/security/ipe/modules/Kconfig index fad96ba534e2..a6ea06cf0737 100644 --- a/security/ipe/modules/Kconfig +++ b/security/ipe/modules/Kconfig @@ -16,5 +16,28 @@ config IPE_PROP_BOOT_VERIFIED If unsure, answer N. +config IPE_PROP_DM_VERITY_SIGNATURE + bool "Enable support for signed dm-verity volumes" + depends on DM_VERITY_VERIFY_ROOTHASH_SIG + default Y + help + This option enables the property 'dmverity_signature' in + IPE policy. This property evaluates to TRUE when a file + is evaluated against a dm-verity volume that was mounted + with a signed root-hash. + + If unsure, answer Y. + +config IPE_PROP_DM_VERITY_ROOTHASH + bool "Enable support for dm-verity volumes" + depends on DM_VERITY + default Y + help + This option enables the property 'dmverity_roothash' in + IPE policy. This property evaluates to TRUE when a file + is evaluated against a dm-verity volume whose root hash + matches the supplied value. + + If unsure, answer Y. endmenu diff --git a/security/ipe/modules/Makefile b/security/ipe/modules/Makefile index e0045ec65434..84fadce85193 100644 --- a/security/ipe/modules/Makefile +++ b/security/ipe/modules/Makefile @@ -6,3 +6,5 @@ # obj-$(CONFIG_IPE_PROP_BOOT_VERIFIED) += boot_verified.o +obj-$(CONFIG_IPE_PROP_DM_VERITY_SIGNATURE) += dmverity_signature.o +obj-$(CONFIG_IPE_PROP_DM_VERITY_ROOTHASH) += dmverity_roothash.o diff --git a/security/ipe/modules/dmverity_roothash.c b/security/ipe/modules/dmverity_roothash.c new file mode 100644 index 000000000000..0f82bec3b842 --- /dev/null +++ b/security/ipe/modules/dmverity_roothash.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe_module.h" + +#include <linux/fs.h> +#include <linux/types.h> + +struct counted_array { + size_t len; + u8 *data; +}; + +static int dvrh_parse(const char *valstr, void **value) +{ + int rv = 0; + struct counted_array *arr; + + arr = kzalloc(sizeof(*arr), GFP_KERNEL); + if (!arr) { + rv = -ENOMEM; + goto err; + } + + arr->len = (strlen(valstr) / 2); + + arr->data = kzalloc(arr->len, GFP_KERNEL); + if (!arr->data) { + rv = -ENOMEM; + goto err; + } + + rv = hex2bin(arr->data, valstr, arr->len); + if (rv != 0) + goto err2; + + *value = arr; + return rv; +err2: + kfree(arr->data); +err: + kfree(arr); + return rv; +} + +static bool dvrh_eval(const struct ipe_eval_ctx *ctx, const void *val) +{ + const u8 *src; + struct counted_array *expect = (struct counted_array *)val; + + if (!ctx->ipe_bdev) + return false; + + if (ctx->ipe_bdev->hashlen != expect->len) + return false; + + src = ctx->ipe_bdev->hash; + + return !memcmp(expect->data, src, expect->len); +} + +static int dvrh_free(void **val) +{ + struct counted_array *expect = (struct counted_array *)val; + + kfree(expect->data); + kfree(expect); + + return 0; +} + +IPE_MODULE(dvrh) = { + .name = "dmverity_roothash", + .version = 1, + .parse = dvrh_parse, + .free = dvrh_free, + .eval = dvrh_eval, +}; diff --git a/security/ipe/modules/dmverity_signature.c b/security/ipe/modules/dmverity_signature.c new file mode 100644 index 000000000000..08746fcbcb3e --- /dev/null +++ b/security/ipe/modules/dmverity_signature.c @@ -0,0 +1,25 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe_module.h" + +#include <linux/fs.h> +#include <linux/types.h> + +static bool dvv_eval(const struct ipe_eval_ctx *ctx, const void *val) +{ + bool expect = (bool)val; + bool eval = ctx->ipe_bdev && (!!ctx->ipe_bdev->sigdata); + + return expect == eval; +} + +IPE_MODULE(dvv) = { + .name = "dmverity_signature", + .version = 1, + .parse = ipe_bool_parse, + .free = NULL, + .eval = dvv_eval, +}; -- 2.33.0

On 11/25/2021 1:37 AM, Roberto Sassu wrote: ..snip I had tried something similar in a very early draft of IPE. The issue that comes with this is that when you compile device-mapper as a module (CONFIG_BLK_DEV_DM=m) you start to get linking errors with this approach. Obviously, we can fix this in the IPE's module Kconfig by setting the dependency to be =y, but it's something to highlight. My general preference is to support the =m configuration by using these blobs. The runtime approach does work with fs-verity, because fs-verity is a file-system level feature that cannot be compiled as a module.

The line above before the check. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua

From: Fan Wu <wufan(a)linux.microsoft.com&gt; Add security_inode_setsecurity to fsverity signature verification. This can let LSMs save the signature data and digest hashes provided by fsverity. Also changes the implementaion inside the hook function to let multiple LSMs can add hooks. Signed-off-by: Fan Wu <wufan(a)linux.microsoft.com&gt; Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- fs/verity/open.c | 12 ++++++++++++ fs/verity/signature.c | 5 ++++- include/linux/fsverity.h | 3 +++ security/ipe/hooks.c | 1 + security/security.c | 6 +++--- 5 files changed, 23 insertions(+), 4 deletions(-) diff --git a/fs/verity/open.c b/fs/verity/open.c index 92df87f5fa38..1f36dae01c22 100644 --- a/fs/verity/open.c +++ b/fs/verity/open.c @@ -7,6 +7,7 @@ #include "fsverity_private.h" +#include <linux/security.h> #include <linux/slab.h> static struct kmem_cache *fsverity_info_cachep; @@ -177,6 +178,17 @@ struct fsverity_info *fsverity_create_info(const struct inode *inode, fsverity_err(inode, "Error %d computing file digest", err); goto out; } + + err = security_inode_setsecurity((struct inode *)inode, + FS_VERITY_DIGEST_SEC_NAME, + vi->file_digest, + vi->tree_params.hash_alg->digest_size, + 0); + if (err) { + fsverity_err(inode, "Error %d inode setsecurity hook", err); + goto out; + } + pr_debug("Computed file digest: %s:%*phN\n", vi->tree_params.hash_alg->name, vi->tree_params.digest_size, vi->file_digest); diff --git a/fs/verity/signature.c b/fs/verity/signature.c index 143a530a8008..20e585d5fa6d 100644 --- a/fs/verity/signature.c +++ b/fs/verity/signature.c @@ -9,6 +9,7 @@ #include <linux/cred.h> #include <linux/key.h> +#include <linux/security.h> #include <linux/slab.h> #include <linux/verification.h> @@ -84,7 +85,9 @@ int fsverity_verify_signature(const struct fsverity_info *vi, pr_debug("Valid signature for file digest %s:%*phN\n", hash_alg->name, hash_alg->digest_size, vi->file_digest); - return 0; + return security_inode_setsecurity((struct inode *)inode, + FS_VERITY_SIGNATURE_SEC_NAME, + signature, sig_size, 0); } #ifdef CONFIG_SYSCTL diff --git a/include/linux/fsverity.h b/include/linux/fsverity.h index b568b3c7d095..dfd7b5a85c67 100644 --- a/include/linux/fsverity.h +++ b/include/linux/fsverity.h @@ -233,4 +233,7 @@ static inline bool fsverity_active(const struct inode *inode) return fsverity_get_info(inode) != NULL; } +#define FS_VERITY_SIGNATURE_SEC_NAME "fsverity.verity-sig" +#define FS_VERITY_DIGEST_SEC_NAME "fsverity.verity-digest" + #endif /* _LINUX_FSVERITY_H */ diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c index 470fb48e490c..d76e60a3f511 100644 --- a/security/ipe/hooks.c +++ b/security/ipe/hooks.c @@ -232,6 +232,7 @@ void ipe_bdev_free_security(struct block_device *bdev) struct ipe_bdev *blob = ipe_bdev(bdev); kfree(blob->sigdata); + kfree(blob->hash); } /** diff --git a/security/security.c b/security/security.c index d7ac9f01500b..81751a91f438 100644 --- a/security/security.c +++ b/security/security.c @@ -1462,7 +1462,7 @@ int security_inode_getsecurity(struct user_namespace *mnt_userns, int security_inode_setsecurity(struct inode *inode, const char *name, const void *value, size_t size, int flags) { struct security_hook_list *hp; - int rc; + int rc = LSM_RET_DEFAULT(inode_setsecurity); if (unlikely(IS_PRIVATE(inode))) return LSM_RET_DEFAULT(inode_setsecurity); @@ -1472,10 +1472,10 @@ int security_inode_setsecurity(struct inode *inode, const char *name, const void hlist_for_each_entry(hp, &security_hook_heads.inode_setsecurity, list) { rc = hp->hook.inode_setsecurity(inode, name, value, size, flags); - if (rc != LSM_RET_DEFAULT(inode_setsecurity)) + if (rc && rc != LSM_RET_DEFAULT(inode_setsecurity)) return rc; } - return LSM_RET_DEFAULT(inode_setsecurity); + return rc; } int security_inode_listsecurity(struct inode *inode, char *buffer, size_t buffer_size) -- 2.33.0

On 10/13/2021 12:24 PM, Eric Biggers wrote: The proposed LSM (IPE) of this series will be the only one to need this information at the  moment. IPE’s goal is to have provide trust-based access control. Trust and Integrity are tied together, as you cannot prove trust without proving integrity. IPE needs the digest information to be able to compare a digest provided by the policy author, against the digest calculated by fsverity to make a decision on whether that specific file, represented by the digest is authorized for the actions specified in the policy. A more concrete example, if an IPE policy author writes:     op=EXECUTE fsverity_digest=<HexDigest > action=DENY IPE takes the digest provided by this security hook, stores it in IPE's security blob on the inode. If this file is later executed, IPE compares the digest stored in the LSM blob, provided by this hook, against <HexDigest> in the policy, if it matches, it denies the access, performing a revocation of that file. This brings me to your next comment: It's available here, but you aren't passing it to this function. The digest is meaningful without the algorithm in this case. IPE does not want to recalculate a digest, that’s expensive and doesn’t provide any value. IPE, in this case, treats this as a buffer to compare the policy-provided one above to make a policy decision about access to the resource. Sorry, will do, not a problem. Sorry, I should've caught these myself. I'll change fsverity_create_info to accept the non-const inode, and change fsverity_verify_signature to accept an additional inode struct as the first arg instead of changing the fsverity_info structure to have a non-const inode field. Could you elaborate on the other signature types that can be used with fs-verity? I’m 99% sure this is what I’m looking for as this is a signature validated in the kernel against the fs-verity keyring as part of the “fsverity enable” utility. It's important that the signature is validated in the kernel, as userspace is considered untrusted until the signature is validated for this case. Sure, signatures, like digests, also provide a way to prove integrity, and the trust component comes from the validation against the keyring, as opposed to a fixed value in IPE’s policy. The use case for fs-verity built-in signatures is that we have a rw ext4 filesystem that has some executable files, and we want to have a execution policy (through IPE) that only _trusted_ executables can run. Perf is important here, hence fs-verity. At the moment, this will just signal to IPE that these fs-verity files were enabled with a built-in signature as opposed to enabled without a signature. In v7, it copies the signature data into IPE's LSM blob attached to the inode. In v8+, I'm changing this to store “true” in IPE's LSM blob instead, as copying the signature data is an unnecessary waste of space and point of failure. This has a _slightly_ different functionality then fs.verity.require_signatures, because even if someone were to disable the require signatures option, IPE would still know if these files were signed or not and be able to make the access control decision based IPE's policy. Very concretely, this powers this kind of rule in IPE:   op=EXECUTE fsverity_signature=TRUE action=ALLOW if that fsverity_signature value in IPE’s LSM blob attached to the inode is true, then fsverity_signature in IPE’s policy will evaluate to true and match this rule. The inverse is also applicable.

I wanted to go back on this question. It seems, at least for fsverity, that you could obtain the root digest at run-time, without storing it in a security blob. I thought I should use fsverity_get_info() but the fsverity_info structure is not exported (it is defined in fs/verity/fsverity_private.h). Then, I defined a new function, fsverity_get_file_digest() to copy the file_digest member of fsverity_info to a buffer and to pass the associated hash algorithm. With that, the code of evaluate() for DIGLIM becomes: info = fsverity_get_info(file_inode(ctx->file)); if (info) ret = fsverity_get_file_digest(info, buffer, sizeof(buffer), &algo); if (!strcmp(expect->data, "diglim") && ret > 0) { ret = diglim_digest_get_info(buffer, algo, COMPACT_FILE, &modifiers, &actions); if (!ret) return true; } Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua

From: Fan Wu <wufan(a)linux.microsoft.com&gt; Enable IPE policy authors to indicate trust for a singular fsverity file, identified by the digest information, through "fsverity_digest" and all fsverity signed by a key via "fsverity_signature". Signed-off-by: Fan Wu <wufan(a)linux.microsoft.com&gt; Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Add FSVerity Support (Introduced) --- security/ipe/eval.c | 1 + security/ipe/eval.h | 9 +++ security/ipe/hooks.c | 58 ++++++++++++++++ security/ipe/hooks.h | 7 ++ security/ipe/ipe.c | 8 +++ security/ipe/ipe.h | 1 + security/ipe/modules/Kconfig | 23 +++++++ security/ipe/modules/Makefile | 2 + security/ipe/modules/fsverity_digest.c | 80 +++++++++++++++++++++++ security/ipe/modules/fsverity_signature.c | 33 ++++++++++ 10 files changed, 222 insertions(+) create mode 100644 security/ipe/modules/fsverity_digest.c create mode 100644 security/ipe/modules/fsverity_signature.c diff --git a/security/ipe/eval.c b/security/ipe/eval.c index facc05c753f4..8f8b91c714c2 100644 --- a/security/ipe/eval.c +++ b/security/ipe/eval.c @@ -97,6 +97,7 @@ static struct ipe_eval_ctx *build_ctx(const struct file *file, ctx->ci_ctx = ipe_current_ctx(); ctx->from_init_sb = from_pinned(file); if (file) { + ctx->ipe_inode = ipe_inode(file->f_inode); if (FILE_BLOCK_DEV(file)) ctx->ipe_bdev = ipe_bdev(FILE_BLOCK_DEV(file)); } diff --git a/security/ipe/eval.h b/security/ipe/eval.h index 25d2d8d55702..d51280f0519f 100644 --- a/security/ipe/eval.h +++ b/security/ipe/eval.h @@ -21,6 +21,14 @@ struct ipe_bdev { size_t hashlen; }; +struct ipe_inode { + const u8 *sigdata; + size_t siglen; + + const u8 *hash; + size_t hashlen; +}; + struct ipe_eval_ctx { enum ipe_hook hook; enum ipe_operation op; @@ -29,6 +37,7 @@ struct ipe_eval_ctx { struct ipe_context *ci_ctx; const struct ipe_bdev *ipe_bdev; + const struct ipe_inode *ipe_inode; bool from_init_sb; }; diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c index d76e60a3f511..78bb3451220a 100644 --- a/security/ipe/hooks.c +++ b/security/ipe/hooks.c @@ -268,3 +268,61 @@ int ipe_bdev_setsecurity(struct block_device *bdev, const char *key, return -ENOSYS; } + +/** + * ipe_inode_setsecurity: Sets the a certain field of a inode security + * blob, based on @key. + * @inode: The inode to source the security blob from. + * @name: The name representing the information to be stored. + * @value: The value to be stored. + * @size: The size of @value. + * @flags: unused + * + * Saves fsverity signature & digest into inode security blob + * + * Return: + * 0 - OK + * !0 - Error + */ +int ipe_inode_setsecurity(struct inode *inode, const char *name, + const void *value, size_t size, + int flags) +{ + struct ipe_inode *inode_sec = ipe_inode(inode); + + if (!strcmp(name, FS_VERITY_SIGNATURE_SEC_NAME)) { + inode_sec->siglen = size; + inode_sec->sigdata = kmemdup(value, size, GFP_KERNEL); + if (!inode_sec->sigdata) + return -ENOMEM; + + return 0; + } + + if (!strcmp(name, FS_VERITY_DIGEST_SEC_NAME)) { + inode_sec->hashlen = size; + inode_sec->hash = kmemdup(value, size, GFP_KERNEL); + if (!inode_sec->hash) + return -ENOMEM; + + return 0; + } + + return -EOPNOTSUPP; +} + +/** + * ipe_node_free_security: Frees all fields of IPE's inode security blob. + * @inode: The inode structure to source the security blob from. + * + * The deallocation of the blob itself is performed later by the LSM + * infrastructure, (on behalf of all LSMs) in lsm_free_file. + * + */ +void ipe_inode_free_security(struct inode *inode) +{ + struct ipe_inode *inode_sec = ipe_inode(inode); + + kfree(inode_sec->sigdata); + kfree(inode_sec->hash); +} diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h index 285f35187188..d6f8c05a8011 100644 --- a/security/ipe/hooks.h +++ b/security/ipe/hooks.h @@ -10,6 +10,7 @@ #include <linux/sched.h> #include <linux/binfmts.h> #include <linux/security.h> +#include <linux/fsverity.h> #include <linux/device-mapper.h> enum ipe_hook { @@ -46,4 +47,10 @@ void ipe_bdev_free_security(struct block_device *bdev); int ipe_bdev_setsecurity(struct block_device *bdev, const char *key, const void *value, size_t len); +void ipe_inode_free_security(struct inode *inode); + +int ipe_inode_setsecurity(struct inode *inode, const char *name, + const void *value, size_t size, + int flags); + #endif /* IPE_HOOKS_H */ diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c index 215936cb4574..c7ecd542c317 100644 --- a/security/ipe/ipe.c +++ b/security/ipe/ipe.c @@ -22,6 +22,7 @@ struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = { .lbs_task = sizeof(struct ipe_context __rcu *), .lbs_bdev = sizeof(struct ipe_bdev), + .lbs_inode = sizeof(struct ipe_inode), }; struct ipe_bdev *ipe_bdev(struct block_device *b) @@ -29,6 +30,11 @@ struct ipe_bdev *ipe_bdev(struct block_device *b) return b->security + ipe_blobs.lbs_bdev; } +struct ipe_inode *ipe_inode(const struct inode *inode) +{ + return inode->i_security + ipe_blobs.lbs_inode; +} + static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(task_alloc, ipe_task_alloc), LSM_HOOK_INIT(task_free, ipe_task_free), @@ -40,6 +46,8 @@ static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security), LSM_HOOK_INIT(bdev_free_security, ipe_bdev_free_security), LSM_HOOK_INIT(bdev_setsecurity, ipe_bdev_setsecurity), + LSM_HOOK_INIT(inode_setsecurity, ipe_inode_setsecurity), + LSM_HOOK_INIT(inode_free_security, ipe_inode_free_security), }; /** diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h index 6b4c7e07f204..16d843614fac 100644 --- a/security/ipe/ipe.h +++ b/security/ipe/ipe.h @@ -22,5 +22,6 @@ extern struct ipe_parser __start_ipe_parsers[], __end_ipe_parsers[]; extern struct ipe_module __start_ipe_modules[], __end_ipe_modules[]; struct ipe_bdev *ipe_bdev(struct block_device *b); +struct ipe_inode *ipe_inode(const struct inode *inode); #endif /* IPE_H */ diff --git a/security/ipe/modules/Kconfig b/security/ipe/modules/Kconfig index a6ea06cf0737..8f823a1edf96 100644 --- a/security/ipe/modules/Kconfig +++ b/security/ipe/modules/Kconfig @@ -40,4 +40,27 @@ config IPE_PROP_DM_VERITY_ROOTHASH If unsure, answer Y. +config IPE_PROP_FS_VERITY_SIGNATURE + bool "Enable property for signed fs-verity files" + depends on FS_VERITY_BUILTIN_SIGNATURES + help + This option enables IPE's integration with FSVerity's + signed hashes. This enables the usage of the property, + "fsverity_signature" in IPE's policy. + + if unsure, answer Y. + +config IPE_PROP_FS_VERITY_DIGEST + bool "Enable property for authorizing fs-verity files via digest" + depends on FS_VERITY + help + This option enables IPE's integration with FSVerity. + This enables the usage of the property "fsverity_digest" in IPE's + policy. This property allows authorization or revocation via a + a hex-string representing the digest of a fsverity file. + + if unsure, answer Y. + + + endmenu diff --git a/security/ipe/modules/Makefile b/security/ipe/modules/Makefile index 84fadce85193..890440b9050f 100644 --- a/security/ipe/modules/Makefile +++ b/security/ipe/modules/Makefile @@ -8,3 +8,5 @@ obj-$(CONFIG_IPE_PROP_BOOT_VERIFIED) += boot_verified.o obj-$(CONFIG_IPE_PROP_DM_VERITY_SIGNATURE) += dmverity_signature.o obj-$(CONFIG_IPE_PROP_DM_VERITY_ROOTHASH) += dmverity_roothash.o +obj-$(CONFIG_IPE_PROP_FS_VERITY_SIGNATURE) += fsverity_signature.o +obj-$(CONFIG_IPE_PROP_FS_VERITY_DIGEST) += fsverity_digest.o diff --git a/security/ipe/modules/fsverity_digest.c b/security/ipe/modules/fsverity_digest.c new file mode 100644 index 000000000000..67944ebbb8d5 --- /dev/null +++ b/security/ipe/modules/fsverity_digest.c @@ -0,0 +1,80 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe_module.h" + +#include <linux/fs.h> +#include <linux/types.h> + +struct counted_array { + size_t len; + u8 *data; +}; + +static int parse(const char *valstr, void **value) +{ + int rv = 0; + struct counted_array *arr; + + arr = kzalloc(sizeof(*arr), GFP_KERNEL); + if (!arr) { + rv = -ENOMEM; + goto err; + } + + arr->len = (strlen(valstr) / 2); + + arr->data = kzalloc(arr->len, GFP_KERNEL); + if (!arr->data) { + rv = -ENOMEM; + goto err; + } + + rv = hex2bin(arr->data, valstr, arr->len); + if (rv != 0) + goto err2; + + *value = arr; + return rv; +err2: + kfree(arr->data); +err: + kfree(arr); + return rv; +} + +static bool evaluate(const struct ipe_eval_ctx *ctx, const void *val) +{ + const u8 *src; + struct counted_array *expect = (struct counted_array *)val; + + if (!ctx->ipe_inode) + return false; + + if (ctx->ipe_inode->hashlen != expect->len) + return false; + + src = ctx->ipe_inode->hash; + + return !memcmp(expect->data, src, expect->len); +} + +static int free_value(void **val) +{ + struct counted_array *expect = (struct counted_array *)val; + + kfree(expect->data); + kfree(expect); + + return 0; +} + +IPE_MODULE(fsv_digest) = { + .name = "fsverity_digest", + .version = 1, + .parse = parse, + .free = free_value, + .eval = evaluate, +}; diff --git a/security/ipe/modules/fsverity_signature.c b/security/ipe/modules/fsverity_signature.c new file mode 100644 index 000000000000..8930a8961f61 --- /dev/null +++ b/security/ipe/modules/fsverity_signature.c @@ -0,0 +1,33 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe_module.h" + +#include <linux/fs.h> +#include <linux/types.h> +#include <linux/slab.h> +#include <linux/audit.h> +#include <linux/mount.h> + +static bool evaluate(const struct ipe_eval_ctx *ctx, const void *value) +{ + bool expect = (bool)value; + + if (!ctx->file) + return false; + + if (!IS_VERITY(ctx->file->f_inode) || !ctx->ipe_inode) + return false; + + return (!!ctx->ipe_inode->sigdata) == expect; +} + +IPE_MODULE(fsvs) = { + .name = "fsverity_signature", + .version = 1, + .parse = ipe_bool_parse, + .free = NULL, + .eval = evaluate, +}; -- 2.33.0

This should be: rc = PTR_ERR(p); Here you need to set a non-zero value, so that ipe_init() does not enable the LSM. I would set to 1 a new global variable, like ipe_lsm_enabled, in ipe_init() just before security_add_hooks(). Then, I would add a check of this variable in ipe_init_securityfs() to avoid the kernel panic. Roberto HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Li Peng, Zhong Ronghua

On 11/3/2021 9:53 AM, Roberto Sassu wrote: Yeah, I actually noticed these two mistakes myself fairly recently. Changes will be applied in v8. That's my plan. -Deven

From: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; Add IPE's admin and developer documentation to the kernel tree. Co-developed-by: Fan Wu <wufan(a)linux.microsoft.com&gt; Signed-off-by: Fan Wu <wufan(a)linux.microsoft.com&gt; Signed-off-by: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; --- Relevant changes since v6: * Add additional developer-level documentation * Update admin-guide docs to reflect changes. * Drop Acked-by due to significant changes --- Documentation/admin-guide/LSM/index.rst | 1 + Documentation/admin-guide/LSM/ipe.rst | 587 ++++++++++++++++++ .../admin-guide/kernel-parameters.txt | 12 + Documentation/security/index.rst | 1 + Documentation/security/ipe.rst | 339 ++++++++++ MAINTAINERS | 2 + 6 files changed, 942 insertions(+) create mode 100644 Documentation/admin-guide/LSM/ipe.rst create mode 100644 Documentation/security/ipe.rst diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst index a6ba95fbaa9f..ce63be6d64ad 100644 --- a/Documentation/admin-guide/LSM/index.rst +++ b/Documentation/admin-guide/LSM/index.rst @@ -47,3 +47,4 @@ subdirectories. tomoyo Yama SafeSetID + ipe diff --git a/Documentation/admin-guide/LSM/ipe.rst b/Documentation/admin-guide/LSM/ipe.rst new file mode 100644 index 000000000000..56a9fa2fe59b --- /dev/null +++ b/Documentation/admin-guide/LSM/ipe.rst @@ -0,0 +1,587 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Integrity Policy Enforcement (IPE) +================================== + +.. NOTE:: + + This is the documentation for admins, system builders, or individuals + attempting to use IPE, without understanding all of its internal systems. + If you're looking for documentation to extend IPE, understand the design + decisions behind IPE, or are just curious about the internals, please + see :ref:`Documentation/security/ipe.rst` + +Overview +-------- + +IPE is a Linux Security Module which imposes a complimentary model +of mandatory access control to other LSMs. Whereas the existing LSMs +impose access control based on labels or paths, IPE imposes access +control based on the trust of the resource. Simply put, IPE +or restricts access to a resource based on the trust of said resource. + +Trust requirements are established via IPE's policy, sourcing multiple +different implementations within the kernel to build a cohesive trust +model, based on how the system was built. + +Trust vs Integrity +------------------ + +Trust, with respect to computing, is a concept that designates a set +of entities who will endorse a set of resources as non-malicious. +Traditionally, this is done via signatures, which is the act of endorsing +a resource. Integrity, on the other hand, is the concept of ensuring that a +resource has not been modified since a point of time. This is typically done +through cryptography or signatures. + +Trust and integrity are very closely tied together concepts, as integrity +is the way you can prove trust for a resource; otherwise it could have +been modified by an entity who is untrusted. + +IPE provides a way for a user to express trust of resources, by using +pre-existing systems which provide the integrity half of the equation. + +Use Cases +--------- + +IPE works best in fixed-function devices: Devices in which their purpose +is clearly defined and not supposed to be changed (e.g. network firewall +device in a data center, an IoT device, etcetera), where all software and +configuration is built and provisioned by the system owner. + +IPE is a long-way off for use in general-purpose computing: +the Linux community as a whole tends to follow a decentralized trust +model, known as the Web of Trust, which IPE has no support for as of yet. +Instead, IPE supports the PKI Trust Model, which generally designates a +set of entities that provide a measure absolute trust. + +Additionally, while most packages are signed today, the files inside +the packages (for instance, the executables), tend to be unsigned. This +makes it difficult to utilize IPE in systems where a package manager is +expected to be functional, without major changes to the package manager +and ecosystem behind it. + +For the highest level of security, platform firmware should verify the +the kernel and optionally the root filesystem (for example, via U-Boot +verified boot). This forms a chain of trust from the hardware, ensuring +that every stage of the system is trusted. + +Known Gaps +---------- + +IPE cannot verify the integrity of anonymous executable memory, such as +the trampolines created by gcc closures and libffi (<3.4.2), or JIT'd code. +Unfortunately, as this is dynamically generated code, there is no way +for IPE to ensure the integrity of this code to form a trust basis. In all +cases, the return result for these operations will be whatever the admin +configures the DEFAULT action for "EXECUTE". + +IPE cannot verify the integrity of interpreted languages' programs when +these scripts invoked via ``<interpreter> <file>``. This is because the +way interpreters execute these files, the scripts themselves are not +evaluated as executable code through one of IPE's hooks. Interpreters +can be enlightened to the usage of IPE by trying to mmap a file into +executable memory (+X), after opening the file and responding to the +error code appropriately. This also applies to included files, or high +value files, such as configuration files of critical system components [#]_. + +.. [#] Mickaël Salaün's `trusted_for patchset <https://lore.kernel.org/all/20211008104840.1733385-1-mic@digikod.net/>`_ + can be used to leverage this. + +Threat Model +------------ + +The threat type addressed by IPE is tampering of executable user-land +code beyond the initially booted kernel, and the initial verification of +kernel modules that are loaded in userland through ``modprobe`` or +``insmod``. + +Tampering violates integrity, and being unable to verify the integrity, +results in a lack of trust. IPE's role in mitigating this threat is to +verify the integrity (and authenticity) of all executable code and to +deny their use if they cannot be trusted (as integrity verification fails). +IPE generates audit logs which may be utilized to detect failures resulting +from failure to pass policy. + +Tampering threat scenarios include modification or replacement of +executable code by a range of actors including: + +- Actors with physical access to the hardware +- Actors with local network access to the system +- Actors with access to the deployment system +- Compromised internal systems under external control +- Malicious end users of the system +- Compromised end users of the system +- Remote (external) compromise of the system + +IPE does not mitigate threats arising from malicious authorized +developers, or compromised developer tools used by authorized +developers. Additionally, IPE draws hard security boundary between user +mode and kernel mode. As a result, IPE does not provide any protections +against a kernel level exploit, and a kernel-level exploit can disable +or tamper with IPE's protections. + +Policy +------ + +IPE policy is a plain-text [#]_ policy composed of multiple statements +over several lines. There is one required line, at the top of the +policy, indicating the policy name, and the policy version, for +instance:: + + policy_name="Ex Policy" policy_version=0.0.0 + +The policy name is a unique key identifying this policy in a human +readable name. This is used to create nodes under securityfs as well as +uniquely identify policies to deploy new policies vs update existing +policies. + +The policy version indicates the current version of the policy (NOT the +policy syntax version). This is used to prevent rollback of policy to +potentially insecure previous versions of the policy. + +The next portion of IPE policy, are rules. Rules are formed by key=value +pairs, known as properties. IPE rules require two properties: "action", +which determines what IPE does when it encounters a match against the +rule, and "op", which determines when that rule should be evaluated. +The ordering is significant, a rule must start with "op", and end with +"action". Thus, a minimal rule is:: + + op=EXECUTE action=ALLOW + +This example will allow any execution. Additional properties are used to +restrict attributes about the files being evaluated. These properties +are intended to be descriptions of systems within the kernel, that can +provide a measure of integrity verification, such that IPE can determine +the trust of the resource based on the "value" half of the property. + +Rules are evaluated top-to-bottom. As a result, any revocation rules, +or denies should be placed early in the file to ensure that these rules +are evaluated before as rule with "action=ALLOW" is hit. + +IPE policy is designed to be only forward compatible. Userspace can read +what the parser's current configuration (supported statements, properties, +etcetera) via reading the securityfs entry, 'ipe/config' + +IPE policy supports comments. The character '#' will function as a +comment, ignoring all characters to the right of '#' until the newline. + +The default behavior of IPE evaluations can also be expressed in policy, +through the ``DEFAULT`` statement. This can be done at a global level, +or a per-operation level:: + + # Global + DEFAULT action=ALLOW + + # Operation Specific + DEFAULT op=EXECUTE action=ALLOW + +A default must be set for all known operations in IPE. If you want to +preserve older policies being compatible with newer kernels that can introduce +new operations, please set a global default of 'ALLOW', and override the +defaults on a per-operation basis. + +With configurable policy-based LSMs, there's several issues with +enforcing the configurable policies at startup, around reading and +parsing the policy: + +1. The kernel *should* not read files from userland, so directly reading + the policy file is prohibited. +2. The kernel command line has a character limit, and one kernel module + should not reserve the entire character limit for its own + configuration. +3. There are various boot loaders in the kernel ecosystem, so handing + off a memory block would be costly to maintain. + +As a result, IPE has addressed this problem through a concept of a "boot +policy". A boot policy is a minimal policy, compiled into the kernel. +This policy is intended to get the system to a state where userland is +setup and ready to receive commands, at which point a more complex +policy ("user policies") can be deployed via securityfs. The boot policy +can be specified via the Kconfig, ``SECURITY_IPE_BOOT_POLICY``, which +accepts a path to a plain-text version of the IPE policy to apply. This +policy will be compiled into the kernel. If not specified, IPE will be +disabled until a policy is deployed and activated through securityfs. + +.. [#] Please see the :ref:`Documentation/security/ipe.rst` for more on this + topic. + +Deploying Policies +~~~~~~~~~~~~~~~~~~ + +User policies as explained above, are policies that are deployed from +userland, through securityfs. These policies are signed to enforce some +level of authorization of the policies (prohibiting an attacker from +gaining root, and deploying an "allow all" policy), through the PKCS#7 +enveloped data format. These policies must be signed by a certificate +that chains to the ``SYSTEM_TRUSTED_KEYRING``. Through openssl, the +signing can be done via:: + + openssl smime -sign -in "$MY_POLICY" -signer "$MY_CERTIFICATE" \ + -inkey "$MY_PRIVATE_KEY" -binary -outform der -noattr -nodetach \ + -out "$MY_POLICY.p7s" + +Deploying the policies is done through securityfs, through the +``new_policy`` node. To deploy a policy, simply cat the file into the +securityfs node:: + + cat "$MY_POLICY.p7s" > /sys/kernel/security/ipe/new_policy + +Upon success, this will create one subdirectory under +``/sys/kernel/security/ipe/policies/``. The subdirectory will be the +``policy_name`` field of the policy deployed, so for the example above, +the directory will be ``/sys/kernel/security/ipe/policies/Ex\ Policy``. +Within this directory, there will be five files: ``pkcs7``, ``policy``, +``active``, ``update``, and ``delete``. + +The ``pkcs7`` file is rw, reading will provide the raw PKCS#7 data that +was provided to the kernel, representing the policy. Writing, will +deploy an in-place policy update - if this policy is the currently +running policy, the new updated policy will replace it immediately upon +success. If the policy being read is the boot policy, when read, this +will return ENOENT. + +The ``policy`` file is read only. Reading will provide the PKCS#7 inner +content of the policy, which will be the plain text policy. + +The ``active`` file is used to set a policy as the currently active policy. +This file is rw, and accepts a value of ``"1"`` to set the policy as active. +Since only a single policy can be active at one time, all other policies +will be marked inactive. The policy being marked active must have a policy +version greater or equal to the currently-running version. + +The ``update`` file is used to update a policy that is already present in +the kernel. This file is write-only and accepts a PKCS#7 signed policy. +One check will be performed on this policy: the policy_names must match +with the updated version and the existing version. If the policy being +updated is the active policy, the updated policy must have a policy version +greater or equal to the currently-running version. + +The ``delete`` file is used to remove a policy that is no longer needed. +This file is write-only and accepts a value of ``"1"`` to delete the policy. +On deletion, the securityfs node representing the policy will be removed. +The policy that is currently active, cannot be deleted. + +Similarly, the writes to both ``update`` and ``new_policy`` above will +result in an error upon syntactically invalid or untrusted policies. +It will also error if a policy already exists with the same ``policy_name``, +in the case of ``new_policy``. + +Deploying these policies will *not* cause IPE to start enforcing this +policy. Once deployment is successful, a policy can be marked as active, +via ``/sys/kernel/security/ipe/$policy_name/active``. IPE will enforce +whatever policy is marked as active. For our example, we can activate +the ``Ex Policy`` via:: + + echo "1" > "/sys/kernel/security/ipe/Ex Policy/active" + +At which point, ``Ex Policy`` will now be the enforced policy on the +system. + +IPE also provides a way to delete policies. This can be done via the +``delete`` securityfs node, ``/sys/kernel/security/ipe/$policy_name/delete``. +Writing ``1`` to that file will delete that node:: + + echo "1" > "/sys/kernel/security/ipe/$policy_name/delete" + +There is only one requirement to delete a policy: + +1. The policy being deleted must not be the active policy. + +.. NOTE:: + + If a traditional MAC system is enabled (SELinux, apparmor, smack), all + writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``. + +Modes +~~~~~ + +IPE supports two modes of operation: permissive (similar to SELinux's +permissive mode) and enforce. Permissive mode performs the same checks +as enforce mode, and logs policy violations, but will not enforce the +policy. This allows users to test policies before enforcing them. + +The default mode is enforce, and can be changed via the kernel command +line parameter ``ipe.enforce=(0|1)``, or the securityfs node +``/sys/kernel/security/ipe/enforce``. + +.. NOTE:: + + If a traditional MAC system is enabled (SELinux, apparmor, smack, etcetera), + all writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``. + +Audit Events +~~~~~~~~~~~~ + +Success Auditing +^^^^^^^^^^^^^^^^ + +IPE supports success auditing. When enabled, all events that pass IPE +policy and are not blocked will emit an audit event. This is disabled by +default, and can be enabled via the kernel command line +``ipe.success_audit=(0|1)`` or the securityfs node, +``/sys/kernel/security/ipe/success_audit``. + +This is very noisy, as IPE will check every user-mode binary on the +system, but is useful for debugging policies. + +.. NOTE:: + + If a traditional MAC system is enabled (SELinux, apparmor, smack, etcetera), + all writes to ipe's securityfs nodes require ``CAP_MAC_ADMIN``. + +Properties +-------------- + +As explained above, IPE properties are ``key=value`` pairs expressed in +IPE policy. Two properties are built-into the policy parser: 'op' and +'action'. The other properties are determinstic attributes to express +across files. Currently those properties are: 'boot_verified', +'dmverity_signature', 'dmverity_roothash', 'fsverity_signature', +'fsverity_digest'. A description of all properties supported by IPE +are listed below: + +op +~~ + +Indicates the operation for a rule to apply to. Must be in every rule, +as the first token. IPE supports the following operations: + +Version 1 +^^^^^^^^^ + +``EXECUTE`` + + Pertains to any file attempting to be executed, or loaded as an + executable. + +``FIRMWARE``: + + Pertains to firmware being loaded via the firmware_class interface. + This covers both the preallocated buffer and the firmware file + itself. + +``KMODULE``: + + Pertains to loading kernel modules via ``modprobe`` or ``insmod``. + +``KEXEC_IMAGE``: + + Pertains to kernel images loading via ``kexec``. + +``KEXEC_INITRAMFS`` + + Pertains to initrd images loading via ``kexec --initrd``. + +``POLICY``: + + Controls loading IMA policies through the + ``/sys/kernel/security/ima/policy`` securityfs entry. + +``X509_CERT``: + + Controls loading IMA certificates through the Kconfigs, + ``CONFIG_IMA_X509_PATH`` and ``CONFIG_EVM_X509_PATH``. + +``KERNEL_READ``: + + Short hand for all of the following: ``FIRMWARE``, ``KMODULE``, + ``KEXEC_IMAGE``, ``KEXEC_INITRAMFS``, ``POLICY``, and ``X509_CERT``. + +action +~~~~~~ + +Version 1 +^^^^^^^^^ + +Determines what IPE should do when a rule matches. Must be in every +rule, as the final clause. Can be one of: + +``ALLOW``: + + If the rule matches, explicitly allow access to the resource to proceed + without executing any more rules. + +``DENY``: + + If the rule matches, explicitly prohibit access to the resource to + proceed without executing any more rules. + +boot_verified +~~~~~~~~~~~~~ + +Version 1 +^^^^^^^^^ + +This property can be utilized for authorization of the first super-block +that executes a file. This is almost always init. Typically this is used +for systems with an initramfs or other initial disk, where this is unmounted +before the system becomes available, and is not covered by any other property. +This property is controlled by the Kconfig, ``CONFIG_IPE_PROP_BOOT_VERIFIED``. +The format of this property is:: + + boot_verified=(TRUE|FALSE) + + +.. WARNING:: + + This property will trust any disk where the first execution evaluation + occurs. If you do *NOT* have a startup disk that is unpacked and unmounted + (like initramfs), then it will automatically trust the root filesystem and + potentially overauthorize the entire disk. + +dmverity_roothash +~~~~~~~~~~~~~~~~~ + +Version 1 +^^^^^^^^^ + +This property can be utilized for authorization or revocation of +specific dm-verity volumes, identified via root hash. It has a +dependency on the DM_VERITY module. This property is controlled by the +Kconfig ``CONFIG_IPE_PROP_DM_VERITY_ROOTHASH``. The format of this property +is:: + + dmverity_roothash=HashHexDigest + +dmverity_signature +~~~~~~~~~~~~~~~~~~ + +Version 1 +^^^^^^^^^ + +This property can be utilized for authorization of all dm-verity volumes +that have a signed roothash that chains to a keyring specified by dm-verity's +configuration, either the system trusted keyring, or the secondary keyring. +It has an additional dependency on the ``DM_VERITY_VERIFY_ROOTHASH_SIG`` +Kconfig. This property is controlled by the Kconfig +``CONFIG_IPE_PROP_DM_VERITY_SIGNATURE``. The format of this property is:: + + dmverity_signature=(TRUE|FALSE) + +fsverity_digest +~~~~~~~~~~~~~~~ + +Version 1 +^^^^^^^^^ +This property can be utilized for authorization or revocation of +specific fsverity enabled file, identified via its fsverity digest, +which is the hash of a struct contains the file's roothash and hashing +parameters. It has a dependency on the FS_VERITY module. +This property is controlled by the Kconfig +``CONFIG_IPE_PROP_FS_VERITY_DIGEST``. The format of this property is:: + + fsverity_digest=HashHexDigest + +fsverity_signature +~~~~~~~~~~~~~~~~~~ + +Version 1 +^^^^^^^^^ + +This property can be utilized for authorization of all fsverity enabled +files that is verified by fsverity. The keyring that is verifies against +is subject to fsverity's configuration, which is typically the fsverity +keyring. It has a dependency on the ``CONFIG_FS_VERITY_BUILTIN_SIGNATURES`` +Kconfig. This property is controlled by the Kconfig +``CONFIG_IPE_PROP_FS_VERITY_SIGNATURE``. The format of this property is:: + + fsverity_signature=(TRUE|FALSE) + +Policy Examples +--------------- + +Allow all +~~~~~~~~~ + +:: + + policy_name="Allow All" policy_version=0.0.0 + DEFAULT action=ALLOW + +Allow only initial superblock +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + policy_name="Allow All Initial SB" policy_version=0.0.0 + DEFAULT action=DENY + + op=EXECUTE boot_verified=TRUE action=ALLOW + +Allow any signed dm-verity volume and the initial superblock +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + policy_name="AllowSignedAndInitial" policy_version=0.0.0 + DEFAULT action=DENY + + op=EXECUTE boot_verified=TRUE action=ALLOW + op=EXECUTE dmverity_signature=TRUE action=ALLOW + +Prohibit execution from a specific dm-verity volume +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + policy_name="AllowSignedAndInitial" policy_version=0.0.0 + DEFAULT action=DENY + + op=EXECUTE dmverity_roothash=401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=DENY + op=EXECUTE boot_verified=TRUE action=ALLOW + op=EXECUTE dmverity_signature=TRUE action=ALLOW + +Allow only a specific dm-verity volume +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + policy_name="AllowSignedAndInitial" policy_version=0.0.0 + DEFAULT action=DENY + + op=EXECUTE dmverity_roothash=401fcec5944823ae12f62726e8184407a5fa9599783f030dec146938 action=ALLOW + +Allow any signed fs-verity file +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + policy_name="AllowSignedFSVerity" policy_version=0.0.0 + DEFAULT action=DENY + + op=EXECUTE fsverity_signature=TRUE action=ALLOW + +Prohibit execution of a specific fs-verity file +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +:: + + policy_name="ProhibitSpecificFSVF" policy_version=0.0.0 + DEFAULT action=DENY + + op=EXECUTE fsverity_digest=fd88f2b8824e197f850bf4c5109bea5cf0ee38104f710843bb72da796ba5af9e action=DENY + op=EXECUTE boot_verified=TRUE action=ALLOW + op=EXECUTE dmverity_signature=TRUE action=ALLOW + +Additional Information +---------------------- + +- `Github Repository <https://github.com/microsoft/ipe>`_ +- `Design Documentation </security/ipe>`_ + +FAQ +--- + +:Q: What's the difference between other LSMs which provide trust-based + access control, for instance, IMA? + +:A: IMA is a fantastic option when needing measurement in addition to the + trust-based access model. All of IMA is centered around their measurement + hashes, so you save time when doing both actions. IPE, on the other hand, + is a highly performant system that does not rely (and explicitly prohibits), + generating its own integrity mechanisms - separating measurement and access + control. Simply put, IPE provides only the enforcement of trust, while other + subsystems provide the integrity guarantee that IPE needs to determine the + trust of a resource. IMA provides both the integrity guarantee, and the + enforcement of trust. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 43dc35fe5bc0..85dd654e642f 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2096,6 +2096,18 @@ ipcmni_extend [KNL] Extend the maximum number of unique System V IPC identifiers from 32,768 to 16,777,216. + ipe.enforce= [IPE] + Format: <bool> + Determine whether IPE starts in permissive (0) or + enforce (1) mode. The default is enforce. + + ipe.success_audit= + [IPE] + Format: <bool> + Start IPE with success auditing enabled, emitting + an audit event when a binary is allowed. The default + is 0. + irqaffinity= [SMP] Set the default irq affinity mask The argument is a cpu list, as described above. diff --git a/Documentation/security/index.rst b/Documentation/security/index.rst index 16335de04e8c..c06530b50514 100644 --- a/Documentation/security/index.rst +++ b/Documentation/security/index.rst @@ -17,3 +17,4 @@ Security Documentation tpm/index digsig landlock + ipe diff --git a/Documentation/security/ipe.rst b/Documentation/security/ipe.rst new file mode 100644 index 000000000000..e691e08e0303 --- /dev/null +++ b/Documentation/security/ipe.rst @@ -0,0 +1,339 @@ +.. SPDX-License-Identifier: GPL-2.0 + +Integrity Policy Enforcement (IPE) - Design Documents +===================================================== + +.. NOTE:: + + This is the documentation for kernel developers and other individuals + who want to understand the reason behind why IPE is designed the way it + is, as well as a tour of the implementation. If you're looking for + documentation on the usage of IPE, please see + :ref:`Documentation/admin-guide/LSM/ipe.rst` + +Role and Scope +-------------- + +IPE originally started with a simple goal: create a system that can +ensure that only trusted usermode binaries are allowed to be executed. + +During the design phase it was apparent that there are multiple systems +within the Linux kernel that can provide some level of integrity +verification, and by association, trust for its content: + + 1. DM-Verity + 2. FS-Verity + 3. IMA + EVM + +However, of those systems only the third option has the ability to enforce +trust requirements on the whole system. Its architecture, however is centered +around its own form of verifications, and a multitude of actions surrounding +those verifications with various purposes, the most prominent being measurement +and verification (appraisal). This makes it unsuitable from a layering and +architectural purpose, as IPE's goal is limited to ensure just trusted usermode +binaries are executed, with the intentional goal of supporting multiple methods +from a higher subsystem layer (i.e. fs, block, or super_block). + +The two other options, dm-verity and fs-verity are missing a crucial component +to accomplish the goal of IPE: a policy to indicate the requirements of +answering the question "What is Trusted?" and a system-wide level of enforcing +those requirements. + +Therefore, IPE was designed around: + + 1. Easy configuration of trust mechanisms + 2. Ease of integration with other layers + 3. Ease of use for platform administrators. + +Design Decisions +---------------- + +Policy +~~~~~~ + +Plain Text +^^^^^^^^^^ + +Unlike other LSMs, IPE's policy is plain-text. This introduces slightly larger +policy files than other LSMs, but solves two major problems that occurs with +other trust-based access control systems. + +The first issue is one of code maintenance and duplication. To author policies, +the policy has to be some form of string representation (be it structured, +through XMl, JSON, YAML, etcetera), to allow the policy author to understand +what is being written. In a hypothetical binary policy design, that a serializer +must be written to write said binary form, for a *majority* of humans to be +able to utilize it properly. + +Additionally, a deserializer will eventually be needed to transform the binary +back into text with as much information preserved. Without a deserializer, a +user of this access control system will have to keep a lookup table of either +a checksum, or the file itself to try to understand what policies have been +deployed on this system and what policies have not. For a single user, this +may be alright, as old policies can be discarded almost immediately after +the update takes hold. + +For users that manage fleets in the thousands, if not hundreds of thousands, +this quickly becomes an issue, as stale policies from years ago may be present, +quickly resulting in the need to recover the policy or fund extensive +infrastructure to track what each policy contains. + +Secondly, a serializer is still needed with a plain-text policy (as the plain +text policy still has to be serialized to a data structure in the kernel), so +not much is saved. + +The second issue is one of transparency. As IPE controls access based on trust, +it's policy must also be trusted to be changed. This is done through signatures, +chaining to the SYSTEM_TRUSTED_KEYRING. The confidence of signing a plain-text +policy in which you can see every aspect of what is being signed is a step higher +than signing an opaque binary blob. + +Boot Policy +~~~~~~~~~~~ + +Additionally, IPE shouldn't have any obvious gaps in its enforcement story. +That means, a policy that configures trust requirements, if specified, must +be enforced as soon as the kernel starts up. That can be accomplished one +of three ways: + + 1. The policy file(s) live on disk and the kernel loads the policy prior + to an code path that would result in an enforcement decision. + 2. The policy file(s) are passed by the bootloader to the kernel, who + parses the policy. + 3. There is a policy file that is compiled into the kernel that is + parsed and enforced on initialization. + +The first option has problems: the kernel reading files from userspace +is typically discouraged and very uncommon in the kernel. + +The second option also has problems: Linux supports a variety of bootloaders +across its entire ecosystem - every bootloader would have to support this +new methodology or there must be an independent source. Additionally, it +would likely result in more drastic changes to the kernel startup than +necessary. + +The third option is the best but it's important to be aware that the policy +will take disk space against the kernel it's compiled in. It's important to +keep this policy generalized enough that userspace can load a new, more +complicated policy, but restrictive enough that it will not overauthorize +and cause security issues. + +The initramfs, provides a way that this bootup path can be established. The +kernel starts with a minimal policy, that just trusts the initramfs. Inside +the initramfs, when the real rootfs is mounted, but not yet transferred to, +it deploys and activates a policy that trusts the new root filesystem(s). +This prevents overauthorization at any step, and keeps the kernel policy +to a minimal size. + +Startup +^^^^^^^ + +Not every system, however starts with an initramfs, so the startup policy +compiled into the kernel will need some flexibility to express how trust +is established for the next phase of the bootup. To this end, if we just +make the compiled-in policy a full IPE policy, it allows system builders +to express the first stage bootup requirements appropriately. + +Updatable, Rebootless Policy +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +As time goes on, trust requirements are changed (vulnerabilities are found in +previously trusted applcations, keys roll, etcetera). Updating a kernel to +change the trust requirements is not always a suitable option, as updates +are not always risk-free and without consequence. This means IPE requires +a policy that can be completely updated from a source external to the kernel. + +Additionally, since the kernel is relatively stateless between invocations, +and we've established that reading policy files off the disk from kernel +space is a *bad idea*, then the policy updates have to be done rebootlessly. + +To allow an update from an external source, it could be potentially malicious, +so this policy needs to have a way to be identified as trusted. This will be +done via a signature, chained to a trust source in the kernel. Arbitrarily, +this will be the ``SYSTEM_TRUSTED_KEYRING``, a keyring that is initially +populated at kernel compile-time, as this matches the expectation that the +author of the compiled-in policy described above is the same entity that can +deploy policy updates. + +Anti-Rollback / Anti-Replay +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Over time, vulnerabilities are found and trusted resources may not be +trusted anymore. IPE's policy has no exception to this. There can be +instances where a mistaken policy author deploys an insecure policy, +before correcting it with a secure policy. + +Assuming that as soon as the insecure policy was signed, an attacker +can acquire the insecure policy, IPE needs a way to prevent rollback +from the secure policy update, to the insecure policy update. + +Initially, IPE's policy can have a policy_version that states the +minimum required version across all policies that can be active on +the system. This will prevent rollback while the system is live. + +.. WARNING:: + + However, since the kernel is stateless across boots, this policy + version will be reset to 0.0.0 on the next boot. System builders + need to be aware of this, and ensure the new secure policies are + deployed ASAP after a boot to ensure that the window of + opportunity is minimal for an attacker to deploy the insecure policy[#]_. + +Implementation +-------------- + +Context +~~~~~~~ + +An ``ipe_context`` structure represent a context in which IPE can be enforced. +It contains all the typical values that one would expect are global: + + 1. Enforce/Permissive State + 2. Active Policy + 3. List of Policies + 4. Success Auditing State + +A context is created at boot time and attached to the ``task_struct`` as a +security blob. All new ``task_struct`` will inherit the original ``ipe_context`` +that the system boots with. This structure is reference counted. + +Initially, a system will only ever have one context; for ``init``, and since +all userspace processes are descendents of ``init``, all of usermode will have +this execution context. + +This architecture has some advantages - namely, it allows for a natural +extension for IPE to create new contexts - such as applying a different +policy for trust for a privledged container from that of its host. + +Anonymous Memory +~~~~~~~~~~~~~~~~ + +Anonymous memory isn't treated any differently than any other access in IPE. +When anonymous memory is mapped with ``+X``, it still comes into the ``file_mmap`` +hook, but with a ``NULL`` file object. This is submitted to the evaluation, like +any other file, however, all trust mechanisms will return false as there is +nothing to evaluate. This means anonymous memory execution is subject to +whatever the ``DEFAULT`` is for ``EXECUTE``. + +.. WARNING:: + + This also occurs with the ``kernel_load_data`` hook, which is used by signed + and compressed kernel modules. Using this with IPE will result in the + ``DEFAULT`` for ``KMODULE`` being taken. + +Policy Parser +~~~~~~~~~~~~~ + +The policy parser is the staple of IPE's functionality, providing a +modular way to introduce new integrations. As such, it's functionality +is divided into 4 passes. This gives the benefit of clearly defined pre +and post-condition states after each pass, giving debugging benefits +when something goes wrong. + +In pass1, the policy is transformed into a 2D, jagged, array of tokens, +where a token is defined as a "key=value" pair, or a singular token, +for example, "DEFAULT". Quoted values are parsed as a single value-pair, +which is why ``<linux/parser.h>`` parser is insufficient - it does not +understand quoted values. + +In pass2, the jagged array produced in pass1 is partially ingested, +creating a partially populated policy, where no rules have been parsed +yet, but metadata and references are created that can be now used in +pass3. + +Examples of parsing that would be done in pass2:: + + policy_name="my-policy" policy_version=0.0.0 + DEFAULT action=DENY + +As these lines are not rules in of themselves, but effect the policy +itself. + +In pass3, the remaining lines in the jagged array produced in pass1 and +partially-consumed in pass2 is consumed completely, parsing all the +rules in IPE policy. This can leverage the data used in pass2. +Example lines parsed in pass3:: + + op=EXECUTE dmverity_signature=TRUE action=DENY + +A rule is strictly defined as starts with the op token and ends with +the action token. + +After this pass, a policy is deemed fully constructed but not yet valid, +as there could be missing elements (such as a required DEFAULT for all +actions, missing a policy_name), etc. + +Additionally, as IPE policy supports operation aliases (an operation +that maps to two or more other operations), support is added here. + +The purpose in the division of pass2 and pass3 is to allow for +declarations in IPE's syntax. For example, in the future, if we were +to introduce this syntax:: + + CERTIFICATE=FakeCert thumbprint=DEADBEEF CN="Contoso" + +And use it like so:: + + op=EXECUTE dmverity_signature=FakeCert action=ALLOW + +The ``CERTIFICATE`` lines can be grouped together at any place in the policy. + +After pass3, an IPE policy can still be technically invalid for use, as +a policy can be lacking required elements to eliminated the possibility +of undefined or unknown behavior. + +A concrete example is when a policy does not define a default action for +all possibilities:: + + DEFAULT op=EXECUTE action=ALLOW + +At this point, while a technically syntactically and semantically valid +policy, it does not contain enough information to determine what should +be done for an operation other than "EXECUTE". As IPE's design +explicitly prohibits the implicit setting of a DEFAULT, it is important +for cases like these are prevented from occurring. + +To resolve all these cases, a final check on the policy is done to ensure +it valid for use. + +In all cases, the parser is the number one bottleneck when it comes to +IPE's performance, but has the benefit of happening rarely, and as a +direct consequence of user-input. + +Module vs Parser +~~~~~~~~~~~~~~~~ + +A "module", "trust provider", or "property" as defined in IPE's code and +commits is an integration with an external subsystem that provides a way +to identify a resource as trusted. It's the code that powers the key=value +pairs in between the ``op`` token and the ``action`` token. These are called +in pass3 when parsing a policy (via the ``parse`` method), and during +evaluation when evaluating a access attempt (via the ``eval`` method). These +discrete modules are single files in ``security/ipe/modules`` and are +versioned independently. The documentation in the admin guide and be used +to cross reference what version supports what syntax. + +A "parser", on the other hand is a discrete unit of code that is *only* +used when parsing a policy in pass2. The intention is to make it easy +to introduce statements, like the ``DEFAULT`` statement:: + + DEFAULT op=EXECUTE action=ALLOW + DEFAULT action=ALLOW + +or, the policy header:: + + policy_name="MyPolicy" policy_version=0.0.0 + +These individual fragments of code, as such, gain access to manipulating +IPE's policy structure directly, as opposed to the opaque ``void *`` that +modules get. + +.. [#] This is something we're interested in solving, using some + persistent storage + +Tests +~~~~~ + +IPE initially has KUnit Tests, testing primarily the parser and the context +structures. A majority of these are table-based testing, please contribute +to them, especially when adding new properties. diff --git a/MAINTAINERS b/MAINTAINERS index a84ca781199b..909db5ba6f87 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9283,6 +9283,8 @@ INTEGRITY POLICY ENFORCEMENT (IPE) M: Deven Bowers <deven.desai(a)linux.microsoft.com&gt; M: Fan Wu <wufan(a)linux.microsoft.com&gt; S: Supported +F: Documentation/admin-guide/LSM/ipe.rst +F: Documentation/security/ipe.rst F: scripts/ipe/ F: security/ipe/ -- 2.33.0