Re: [PATCH v26 04/25] IMA: avoid label collisions with stacked LSMs

Integrity measurement may filter on security module information and needs to be clear in the case of multiple active security modules which applies. Provide a boot option ima_rules_lsm= to allow the user to specify an active securty module to apply filters to. If not specified, use the first registered module that supports the audit_rule_match() LSM hook. Allow the user to specify in the IMA policy an lsm= option to specify the security module to use for a particular rule. Signed-off-by: Casey Schaufler <casey(a)schaufler-ca.com&gt; To: Mimi Zohar <zohar(a)linux.ibm.com&gt; To: linux-integrity(a)vger.kernel.org --- Documentation/ABI/testing/ima_policy | 8 ++- security/integrity/ima/ima_policy.c | 77 ++++++++++++++++++++-------- 2 files changed, 62 insertions(+), 23 deletions(-) diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index 070779e8d836..84dd19bc4344 100644 --- a/Documentation/ABI/testing/ima_policy +++ b/Documentation/ABI/testing/ima_policy @@ -25,7 +25,7 @@ Description: base: [[func=] [mask=] [fsmagic=] [fsuuid=] [uid=] [euid=] [fowner=] [fsname=]] lsm: [[subj_user=] [subj_role=] [subj_type=] - [obj_user=] [obj_role=] [obj_type=]] + [obj_user=] [obj_role=] [obj_type=] [lsm=]] option: [[appraise_type=]] [template=] [permit_directio] [appraise_flag=] [keyrings=] base: @@ -117,6 +117,12 @@ Description: measure subj_user=_ func=FILE_CHECK mask=MAY_READ + It is possible to explicitly specify which security + module a rule applies to using lsm=. If the security + modules specified is not active on the system the rule + will be rejected. If lsm= is not specified the first + security module registered on the system will be assumed. + Example of measure rules using alternate PCRs:: measure func=KEXEC_KERNEL_CHECK pcr=4 diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 5c40677e881c..d804b9a0dd95 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -79,8 +79,9 @@ struct ima_rule_entry { bool (*uid_op)(kuid_t, kuid_t); /* Handlers for operators */ bool (*fowner_op)(kuid_t, kuid_t); /* uid_eq(), uid_gt(), uid_lt() */ int pcr; + int which_lsm; /* which of the rules to use */ struct { - void *rules[LSMBLOB_ENTRIES]; /* LSM file metadata specific */ + void *rule; /* LSM file metadata specific */ char *args_p; /* audit value */ int type; /* audit type */ } lsm[MAX_LSM_RULES]; @@ -92,17 +93,15 @@ struct ima_rule_entry { /** * ima_lsm_isset - Is a rule set for any of the active security modules - * @rules: The set of IMA rules to check + * @entry: the rule entry to examine + * @lsm_rule: the specific rule type in question * - * If a rule is set for any LSM return true, otherwise return false. + * If a rule is set return true, otherwise return false. */ -static inline bool ima_lsm_isset(void *rules[]) +static inline bool ima_lsm_isset(struct ima_rule_entry *entry, int lsm_rule) { - int i; - - for (i = 0; i < LSMBLOB_ENTRIES; i++) - if (rules[i]) - return true; + if (entry->lsm[lsm_rule].rule) + return true;

return false; } @@ -282,6 +281,20 @@ static int __init default_appraise_policy_setup(char *str) } __setup("ima_appraise_tcb", default_appraise_policy_setup); +static int ima_rules_lsm __ro_after_init; + +static int __init ima_rules_lsm_init(char *str) +{ + ima_rules_lsm = lsm_name_to_slot(str); + if (ima_rules_lsm < 0) { + ima_rules_lsm = 0; + pr_err("rule lsm \"%s\" not registered", str); + } + + return 1; +} +__setup("ima_rules_lsm=", ima_rules_lsm_init); + static struct ima_rule_opt_list *ima_alloc_rule_opt_list(const substring_t *src) { struct ima_rule_opt_list *opt_list; @@ -351,11 +364,10 @@ static void ima_free_rule_opt_list(struct ima_rule_opt_list *opt_list) static void ima_lsm_free_rule(struct ima_rule_entry *entry) { int i; - int r; for (i = 0; i < MAX_LSM_RULES; i++) { - for (r = 0; r < LSMBLOB_ENTRIES; r++) - ima_filter_rule_free(entry->lsm[i].rules[r]); + if (entry->lsm[i].rule) + ima_filter_rule_free(entry->lsm[i].rule); kfree(entry->lsm[i].args_p); } } @@ -406,8 +418,8 @@ static struct ima_rule_entry *ima_lsm_copy_rule(struct ima_rule_entry *entry) ima_filter_rule_init(nentry->lsm[i].type, Audit_equal, nentry->lsm[i].args_p, - &nentry->lsm[i].rules[0]); - if (!ima_lsm_isset(nentry->lsm[i].rules)) + &nentry->lsm[i].rule); + if (!ima_lsm_isset(nentry, i)) pr_warn("rule for LSM \'%s\' is undefined\n", nentry->lsm[i].args_p); } @@ -596,7 +608,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule, int rc = 0; u32 osid; - if (!ima_lsm_isset(rule->lsm[i].rules)) { + if (!ima_lsm_isset(rule, i)) { if (!rule->lsm[i].args_p) continue; else @@ -609,14 +621,14 @@ static bool ima_match_rules(struct ima_rule_entry *rule, security_inode_getsecid(inode, &osid); rc = ima_filter_rule_match(osid, rule->lsm[i].type, Audit_equal, - rule->lsm[i].rules); + rule->lsm[i].rule); break; case LSM_SUBJ_USER: case LSM_SUBJ_ROLE: case LSM_SUBJ_TYPE: rc = ima_filter_rule_match(secid, rule->lsm[i].type, Audit_equal, - rule->lsm[i].rules); + rule->lsm[i].rule); break; default: break; @@ -966,7 +978,7 @@ enum { Opt_uid_lt, Opt_euid_lt, Opt_fowner_lt, Opt_appraise_type, Opt_appraise_flag, Opt_permit_directio, Opt_pcr, Opt_template, Opt_keyrings, - Opt_label, Opt_err + Opt_lsm, Opt_label, Opt_err }; static const match_table_t policy_tokens = { @@ -1004,6 +1016,7 @@ static const match_table_t policy_tokens = { {Opt_template, "template=%s"}, {Opt_keyrings, "keyrings=%s"}, {Opt_label, "label=%s"}, + {Opt_lsm, "lsm=%s"}, {Opt_err, NULL} }; @@ -1012,7 +1025,7 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry, { int result; - if (ima_lsm_isset(entry->lsm[lsm_rule].rules)) + if (ima_lsm_isset(entry, lsm_rule)) return -EINVAL; entry->lsm[lsm_rule].args_p = match_strdup(args); @@ -1022,8 +1035,8 @@ static int ima_lsm_rule_init(struct ima_rule_entry *entry, entry->lsm[lsm_rule].type = audit_type; result = ima_filter_rule_init(entry->lsm[lsm_rule].type, Audit_equal, entry->lsm[lsm_rule].args_p, - &entry->lsm[lsm_rule].rules[0]); - if (!ima_lsm_isset(entry->lsm[lsm_rule].rules)) { + &entry->lsm[lsm_rule].rule); + if (!ima_lsm_isset(entry, lsm_rule)) { pr_warn("rule for LSM \'%s\' is undefined\n", entry->lsm[lsm_rule].args_p); @@ -1561,6 +1574,19 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) &(template_desc->num_fields)); entry->template = template_desc; break; + case Opt_lsm: + result = lsm_name_to_slot(args[0].from); + if (result == LSMBLOB_INVALID) { + int i; + + for (i = 0; i < MAX_LSM_RULES; i++) + entry->lsm[i].args_p = NULL; + result = -EINVAL; + break; + } + entry->which_lsm = result; + result = 0; + break; case Opt_err: ima_log_string(ab, "UNKNOWN", p); result = -EINVAL; @@ -1597,6 +1623,7 @@ ssize_t ima_parse_add_rule(char *rule) struct ima_rule_entry *entry; ssize_t result, len; int audit_info = 0; + int i; p = strsep(&rule, "\n"); len = strlen(p) + 1; @@ -1614,6 +1641,9 @@ ssize_t ima_parse_add_rule(char *rule) INIT_LIST_HEAD(&entry->list); + for (i = 0; i < MAX_LSM_RULES; i++) + entry->which_lsm = ima_rules_lsm; + result = ima_parse_rule(p, entry); if (result) { ima_free_rule(entry); @@ -1830,7 +1860,7 @@ int ima_policy_show(struct seq_file *m, void *v) } for (i = 0; i < MAX_LSM_RULES; i++) { - if (ima_lsm_isset(entry->lsm[i].rules)) { + if (ima_lsm_isset(entry, i)) { switch (i) { case LSM_OBJ_USER: seq_printf(m, pt(Opt_obj_user), @@ -1872,6 +1902,9 @@ int ima_policy_show(struct seq_file *m, void *v) seq_puts(m, "appraise_flag=check_blacklist "); if (entry->flags & IMA_PERMIT_DIRECTIO) seq_puts(m, "permit_directio "); + if (entry->which_lsm >= 0) + seq_printf(m, pt(Opt_lsm), + lsm_slot_to_name(entry->which_lsm)); rcu_read_unlock(); seq_puts(m, "\n"); return 0; -- 2.29.2