Re: [PATCH] Split audit filtering into auditfilter.c

On Thu, 2005-12-15 at 14:43 -0600, Dustin Kirkland wrote: Hm, I didn't actually manage to commit them to git at all the second time (having reverted my first version). I've added them to the git tree now; thanks. diff --git a/kernel/audit.h b/kernel/audit.h new file mode 100644 index 0000000..7643e46 --- /dev/null +++ b/kernel/audit.h @@ -0,0 +1,70 @@ +/* audit -- definition of audit_context structure and supporting types + * + * Copyright 2003-2004 Red Hat, Inc. + * Copyright 2005 Hewlett-Packard Development Company, L.P. + * Copyright 2005 IBM Corporation + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <linux/fs.h> +#include <linux/audit.h> + +/* 0 = no checking + 1 = put_count checking + 2 = verbose put_count checking +*/ +#define AUDIT_DEBUG 0 + +/* At task start time, the audit_state is set in the audit_context using + a per-task filter. At syscall entry, the audit_state is augmented by + the syscall filter. */ +enum audit_state { + AUDIT_DISABLED, /* Do not create per-task audit_context. + * No syscall-specific audit records can + * be generated. */ + AUDIT_SETUP_CONTEXT, /* Create the per-task audit_context, + * but don't necessarily fill it in at + * syscall entry time (i.e., filter + * instead). */ + AUDIT_BUILD_CONTEXT, /* Create the per-task audit_context, + * and always fill it in at syscall + * entry time. This makes a full + * syscall record available if some + * other part of the kernel decides it + * should be recorded. */ + AUDIT_RECORD_CONTEXT /* Create the per-task audit_context, + * always fill it in at syscall entry + * time, and always write out the audit + * record at syscall exit time. */ +}; + +/* Rule lists */ +struct audit_entry { + struct list_head list; + struct rcu_head rcu; + struct audit_rule rule; +}; + + +extern int audit_pid; +extern int audit_comparator(const u32 left, const u32 op, const u32 right); + +extern void audit_send_reply(int pid, int seq, int type, + int done, int multi, + void *payload, int size); +extern void audit_log_lost(const char *message); +extern void audit_panic(const char *message); +extern struct semaphore audit_netlink_sem; diff --git a/kernel/auditfilter.c b/kernel/auditfilter.c new file mode 100644 index 0000000..355b812 --- /dev/null +++ b/kernel/auditfilter.c @@ -0,0 +1,378 @@ +/* auditfilter.c -- filtering of audit events + * + * Copyright 2003-2004 Red Hat, Inc. + * Copyright 2005 Hewlett-Packard Development Company, L.P. + * Copyright 2005 IBM Corporation + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ + +#include <linux/kernel.h> +#include <linux/audit.h> +#include <linux/kthread.h> +#include <linux/netlink.h> +#include "audit.h" + +/* There are three lists of rules -- one to search at task creation + * time, one to search at syscall entry time, and another to search at + * syscall exit time. */ +struct list_head audit_filter_list[AUDIT_NR_FILTERS] = { + LIST_HEAD_INIT(audit_filter_list[0]), + LIST_HEAD_INIT(audit_filter_list[1]), + LIST_HEAD_INIT(audit_filter_list[2]), + LIST_HEAD_INIT(audit_filter_list[3]), + LIST_HEAD_INIT(audit_filter_list[4]), + LIST_HEAD_INIT(audit_filter_list[5]), +#if AUDIT_NR_FILTERS != 6 +#error Fix audit_filter_list initialiser +#endif +}; + +/* Copy rule from user-space to kernel-space. Called from + * audit_add_rule during AUDIT_ADD. */ +static inline int audit_copy_rule(struct audit_rule *d, struct audit_rule *s) +{ + int i; + + if (s->action != AUDIT_NEVER + && s->action != AUDIT_POSSIBLE + && s->action != AUDIT_ALWAYS) + return -1; + if (s->field_count < 0 || s->field_count > AUDIT_MAX_FIELDS) + return -1; + if ((s->flags & ~AUDIT_FILTER_PREPEND) >= AUDIT_NR_FILTERS) + return -1; + + d->flags = s->flags; + d->action = s->action; + d->field_count = s->field_count; + for (i = 0; i < d->field_count; i++) { + d->fields[i] = s->fields[i]; + d->values[i] = s->values[i]; + } + for (i = 0; i < AUDIT_BITMASK_SIZE; i++) d->mask[i] = s->mask[i]; + return 0; +} + +/* Check to see if two rules are identical. It is called from + * audit_add_rule during AUDIT_ADD and + * audit_del_rule during AUDIT_DEL. */ +static inline int audit_compare_rule(struct audit_rule *a, struct audit_rule *b) +{ + int i; + + if (a->flags != b->flags) + return 1; + + if (a->action != b->action) + return 1; + + if (a->field_count != b->field_count) + return 1; + + for (i = 0; i < a->field_count; i++) { + if (a->fields[i] != b->fields[i] + || a->values[i] != b->values[i]) + return 1; + } + + for (i = 0; i < AUDIT_BITMASK_SIZE; i++) + if (a->mask[i] != b->mask[i]) + return 1; + + return 0; +} + +/* Note that audit_add_rule and audit_del_rule are called via + * audit_receive() in audit.c, and are protected by + * audit_netlink_sem. */ +static inline int audit_add_rule(struct audit_rule *rule, + struct list_head *list) +{ + struct audit_entry *entry; + int i; + + /* Do not use the _rcu iterator here, since this is the only + * addition routine. */ + list_for_each_entry(entry, list, list) { + if (!audit_compare_rule(rule, &entry->rule)) { + return -EEXIST; + } + } + + for (i = 0; i < rule->field_count; i++) { + if (rule->fields[i] & AUDIT_UNUSED_BITS) + return -EINVAL; + if ( rule->fields[i] & AUDIT_NEGATE ) + rule->fields[i] |= AUDIT_NOT_EQUAL; + else if ( (rule->fields[i] & AUDIT_OPERATORS) == 0 ) + rule->fields[i] |= AUDIT_EQUAL; + rule->fields[i] &= (~AUDIT_NEGATE); + } + + if (!(entry = kmalloc(sizeof(*entry), GFP_KERNEL))) + return -ENOMEM; + if (audit_copy_rule(&entry->rule, rule)) { + kfree(entry); + return -EINVAL; + } + + if (entry->rule.flags & AUDIT_FILTER_PREPEND) { + entry->rule.flags &= ~AUDIT_FILTER_PREPEND; + list_add_rcu(&entry->list, list); + } else { + list_add_tail_rcu(&entry->list, list); + } + + return 0; +} + +static inline void audit_free_rule(struct rcu_head *head) +{ + struct audit_entry *e = container_of(head, struct audit_entry, rcu); + kfree(e); +} + +/* Note that audit_add_rule and audit_del_rule are called via + * audit_receive() in audit.c, and are protected by + * audit_netlink_sem. */ +static inline int audit_del_rule(struct audit_rule *rule, + struct list_head *list) +{ + struct audit_entry *e; + + /* Do not use the _rcu iterator here, since this is the only + * deletion routine. */ + list_for_each_entry(e, list, list) { + if (!audit_compare_rule(rule, &e->rule)) { + list_del_rcu(&e->list); + call_rcu(&e->rcu, audit_free_rule); + return 0; + } + } + return -ENOENT; /* No matching rule */ +} + +static int audit_list_rules(void *_dest) +{ + int pid, seq; + int *dest = _dest; + struct audit_entry *entry; + int i; + + pid = dest[0]; + seq = dest[1]; + kfree(dest); + + down(&audit_netlink_sem); + + /* The *_rcu iterators not needed here because we are + always called with audit_netlink_sem held. */ + for (i=0; i<AUDIT_NR_FILTERS; i++) { + list_for_each_entry(entry, &audit_filter_list[i], list) + audit_send_reply(pid, seq, AUDIT_LIST, 0, 1, + &entry->rule, sizeof(entry->rule)); + } + audit_send_reply(pid, seq, AUDIT_LIST, 1, 1, NULL, 0); + + up(&audit_netlink_sem); + return 0; +} + +/** + * audit_receive_filter - apply all rules to the specified message type + * @type: audit message type + * @pid: target pid for netlink audit messages + * @uid: target uid for netlink audit messages + * @seq: netlink audit message sequence (serial) number + * @data: payload data + * @loginuid: loginuid of sender + */ +int audit_receive_filter(int type, int pid, int uid, int seq, void *data, + uid_t loginuid) +{ + struct task_struct *tsk; + int *dest; + int err = 0; + unsigned listnr; + + switch (type) { + case AUDIT_LIST: + /* We can't just spew out the rules here because we might fill + * the available socket buffer space and deadlock waiting for + * auditctl to read from it... which isn't ever going to + * happen if we're actually running in the context of auditctl + * trying to _send_ the stuff */ + + dest = kmalloc(2 * sizeof(int), GFP_KERNEL); + if (!dest) + return -ENOMEM; + dest[0] = pid; + dest[1] = seq; + + tsk = kthread_run(audit_list_rules, dest, "audit_list_rules"); + if (IS_ERR(tsk)) { + kfree(dest); + err = PTR_ERR(tsk); + } + break; + case AUDIT_ADD: + listnr = ((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND; + switch(listnr) { + default: + return -EINVAL; + + case AUDIT_FILTER_USER: + case AUDIT_FILTER_EXCLUDE: +#ifdef CONFIG_AUDITSYSCALL + case AUDIT_FILTER_ENTRY: + case AUDIT_FILTER_EXIT: + case AUDIT_FILTER_TASK: +#endif + ; + } + err = audit_add_rule(data, &audit_filter_list[listnr]); + if (!err) + audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, + "auid=%u added an audit rule\n", loginuid); + break; + case AUDIT_DEL: + listnr =((struct audit_rule *)data)->flags & ~AUDIT_FILTER_PREPEND; + if (listnr >= AUDIT_NR_FILTERS) + return -EINVAL; + + err = audit_del_rule(data, &audit_filter_list[listnr]); + if (!err) + audit_log(NULL, GFP_KERNEL, AUDIT_CONFIG_CHANGE, + "auid=%u removed an audit rule\n", loginuid); + break; + default: + return -EINVAL; + } + + return err; +} + +int audit_comparator(const u32 left, const u32 op, const u32 right) +{ + switch (op) { + case AUDIT_EQUAL: + return (left == right); + case AUDIT_NOT_EQUAL: + return (left != right); + case AUDIT_LESS_THAN: + return (left < right); + case AUDIT_LESS_THAN_OR_EQUAL: + return (left <= right); + case AUDIT_GREATER_THAN: + return (left > right); + case AUDIT_GREATER_THAN_OR_EQUAL: + return (left >= right); + default: + return -EINVAL; + } +} + + + +static int audit_filter_user_rules(struct netlink_skb_parms *cb, + struct audit_rule *rule, + enum audit_state *state) +{ + int i; + + for (i = 0; i < rule->field_count; i++) { + u32 field = rule->fields[i] & ~AUDIT_OPERATORS; + u32 op = rule->fields[i] & AUDIT_OPERATORS; + u32 value = rule->values[i]; + int result = 0; + + switch (field) { + case AUDIT_PID: + result = audit_comparator(cb->creds.pid, op, value); + break; + case AUDIT_UID: + result = audit_comparator(cb->creds.uid, op, value); + break; + case AUDIT_GID: + result = audit_comparator(cb->creds.gid, op, value); + break; + case AUDIT_LOGINUID: + result = audit_comparator(cb->loginuid, op, value); + break; + } + + if (!result) + return 0; + } + switch (rule->action) { + case AUDIT_NEVER: *state = AUDIT_DISABLED; break; + case AUDIT_POSSIBLE: *state = AUDIT_BUILD_CONTEXT; break; + case AUDIT_ALWAYS: *state = AUDIT_RECORD_CONTEXT; break; + } + return 1; +} + +int audit_filter_user(struct netlink_skb_parms *cb, int type) +{ + struct audit_entry *e; + enum audit_state state; + int ret = 1; + + rcu_read_lock(); + list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_USER], list) { + if (audit_filter_user_rules(cb, &e->rule, &state)) { + if (state == AUDIT_DISABLED) + ret = 0; + break; + } + } + rcu_read_unlock(); + + return ret; /* Audit by default */ +} + +int audit_filter_exclude(int type) +{ + struct audit_entry *e; + int result = 0; + + rcu_read_lock(); + if (list_empty(&audit_filter_list[AUDIT_FILTER_EXCLUDE])) + goto unlock_and_return; + + list_for_each_entry_rcu(e, &audit_filter_list[AUDIT_FILTER_EXCLUDE], + list) { + struct audit_rule *rule = &e->rule; + int i; + for (i = 0; i < rule->field_count; i++) { + u32 field = rule->fields[i] & ~AUDIT_OPERATORS; + u32 op = rule->fields[i] & AUDIT_OPERATORS; + u32 value = rule->values[i]; + if ( field == AUDIT_MSGTYPE ) { + result = audit_comparator(type, op, value); + if (!result) + break; + } + } + if (result) + goto unlock_and_return; + } +unlock_and_return: + rcu_read_unlock(); + return result; +} + + -- dwmw2