Re: [PATCH v35 05/29] 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 security 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 ++++- include/linux/security.h | 14 ++++---- security/integrity/ima/ima_policy.c | 51 ++++++++++++++++++++++++---- security/security.c | 35 +++++++++++++++---- 4 files changed, 89 insertions(+), 19 deletions(-) diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index 839fab811b18..64863e9d87ea 100644 --- a/Documentation/ABI/testing/ima_policy +++ b/Documentation/ABI/testing/ima_policy @@ -26,7 +26,7 @@ Description: [uid=] [euid=] [gid=] [egid=] [fowner=] [fgroup=]] 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=] [appraise_algos=] [keyrings=] base: @@ -126,6 +126,12 @@ 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 + module 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/include/linux/security.h b/include/linux/security.h index d00870d2b416..3666eddad59a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1985,25 +1985,27 @@ static inline void security_audit_rule_free(struct audit_lsm_rules *lsmrules) #endif /* CONFIG_AUDIT */ #if defined(CONFIG_IMA_LSM_RULES) && defined(CONFIG_SECURITY) -int ima_filter_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule); -int ima_filter_rule_match(u32 secid, u32 field, u32 op, void *lsmrule); -void ima_filter_rule_free(void *lsmrule); +int ima_filter_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule, + int lsmslot); +int ima_filter_rule_match(u32 secid, u32 field, u32 op, void *lsmrule, + int lsmslot); +void ima_filter_rule_free(void *lsmrule, int lsmslot); #else static inline int ima_filter_rule_init(u32 field, u32 op, char *rulestr, - void **lsmrule) + void **lsmrule, int lsmslot) { return 0; } static inline int ima_filter_rule_match(u32 secid, u32 field, u32 op, - void *lsmrule) + void *lsmrule, int lsmslot) { return 0; } -static inline void ima_filter_rule_free(void *lsmrule) +static inline void ima_filter_rule_free(void *lsmrule, int lsmslot) { } #endif /* defined(CONFIG_IMA_LSM_RULES) && defined(CONFIG_SECURITY) */ diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index eea6e92500b8..97470354c8ae 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -89,6 +89,7 @@ struct ima_rule_entry { bool (*fgroup_op)(kgid_t cred_gid, kgid_t rule_gid); /* gid_eq(), gid_gt(), gid_lt() */ int pcr; unsigned int allowed_algos; /* bitfield of allowed hash algorithms */ + int which; /* which LSM rule applies to */ struct { void *rule; /* LSM file metadata specific */ char *args_p; /* audit value */ @@ -285,6 +286,20 @@ 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; @@ -356,7 +371,7 @@ static void ima_lsm_free_rule(struct ima_rule_entry *entry) int i; for (i = 0; i < MAX_LSM_RULES; i++) { - ima_filter_rule_free(entry->lsm[i].rule); + ima_filter_rule_free(entry->lsm[i].rule, entry->which); kfree(entry->lsm[i].args_p); } } @@ -407,7 +422,8 @@ 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].rule); + &nentry->lsm[i].rule, + entry->which); if (!nentry->lsm[i].rule) pr_warn("rule for LSM \'%s\' is undefined\n", nentry->lsm[i].args_p); @@ -623,14 +639,16 @@ 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].rule); + rule->lsm[i].rule, + rule->which); 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].rule); + rule->lsm[i].rule, + rule->which); break; default: break; @@ -1025,7 +1043,7 @@ enum policy_opt { Opt_fowner_lt, Opt_fgroup_lt, Opt_appraise_type, Opt_appraise_flag, Opt_appraise_algos, 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 = { @@ -1073,6 +1091,7 @@ 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} }; @@ -1091,7 +1110,8 @@ 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].rule); + &entry->lsm[lsm_rule].rule, + entry->which); if (!entry->lsm[lsm_rule].rule) { pr_warn("rule for LSM \'%s\' is undefined\n", entry->lsm[lsm_rule].args_p); @@ -1780,6 +1800,19 @@ 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 = result; + result = 0; + break; case Opt_err: ima_log_string(ab, "UNKNOWN", p); result = -EINVAL; @@ -1816,6 +1849,7 @@ 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; @@ -1833,6 +1867,9 @@ ssize_t ima_parse_add_rule(char *rule) INIT_LIST_HEAD(&entry->list); + for (i = 0; i < MAX_LSM_RULES; i++) + entry->which = ima_rules_lsm; + result = ima_parse_rule(p, entry); if (result) { ima_free_rule(entry); @@ -2158,6 +2195,8 @@ 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 >= 0) + seq_printf(m, pt(Opt_lsm), lsm_slot_to_name(entry->which)); rcu_read_unlock(); seq_puts(m, "\n"); return 0; diff --git a/security/security.c b/security/security.c index d1ddbb857af1..9e0139b0d346 100644 --- a/security/security.c +++ b/security/security.c @@ -2728,19 +2728,42 @@ int security_audit_rule_match(u32 secid, u32 field, u32 op, * The integrity subsystem uses the same hooks as * the audit subsystem. */ -int ima_filter_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule) +int ima_filter_rule_init(u32 field, u32 op, char *rulestr, void **lsmrule, + int lsmslot) { - return call_int_hook(audit_rule_init, 0, field, op, rulestr, lsmrule); + struct security_hook_list *hp; + + hlist_for_each_entry(hp, &security_hook_heads.audit_rule_init, list) + if (hp->lsmid->slot == lsmslot) + return hp->hook.audit_rule_init(field, op, rulestr, + lsmrule); + + return 0; } -void ima_filter_rule_free(void *lsmrule) +void ima_filter_rule_free(void *lsmrule, int lsmslot) { - call_void_hook(audit_rule_free, lsmrule); + struct security_hook_list *hp; + + hlist_for_each_entry(hp, &security_hook_heads.audit_rule_free, list) { + if (hp->lsmid->slot == lsmslot) { + hp->hook.audit_rule_free(lsmrule); + return; + } + } } -int ima_filter_rule_match(u32 secid, u32 field, u32 op, void *lsmrule) +int ima_filter_rule_match(u32 secid, u32 field, u32 op, void *lsmrule, + int lsmslot) { - return call_int_hook(audit_rule_match, 0, secid, field, op, lsmrule); + struct security_hook_list *hp; + + hlist_for_each_entry(hp, &security_hook_heads.audit_rule_match, list) + if (hp->lsmid->slot == lsmslot) + return hp->hook.audit_rule_match(secid, field, op, + lsmrule); + + return 0; } #endif /* CONFIG_IMA_LSM_RULES */