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Hermes SMTP Server) with ESMTPA ID 2eb209f35c81771290ca3d956ba58232; Tue, 28 Jun 2022 01:00:43 +0000 (UTC) From: Casey Schaufler To: casey.schaufler@intel.com, jmorris@namei.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org Cc: casey@schaufler-ca.com, linux-audit@redhat.com, keescook@chromium.org, john.johansen@canonical.com, penguin-kernel@i-love.sakura.ne.jp, paul@paul-moore.com, stephen.smalley.work@gmail.com, linux-kernel@vger.kernel.org Subject: [PATCH v37 05/33] IMA: avoid label collisions with stacked LSMs Date: Mon, 27 Jun 2022 17:55:43 -0700 Message-Id: <20220628005611.13106-6-casey@schaufler-ca.com> X-Mailer: git-send-email 2.36.1 In-Reply-To: <20220628005611.13106-1-casey@schaufler-ca.com> References: <20220628005611.13106-1-casey@schaufler-ca.com> MIME-Version: 1.0 Precedence: bulk List-ID: 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 To: Mimi Zohar To: linux-integrity@vger.kernel.org --- Documentation/ABI/testing/ima_policy | 8 +++- include/linux/security.h | 14 +++--- security/integrity/ima/ima_policy.c | 70 +++++++++++++++++++++++++--- security/security.c | 35 +++++++++++--- 4 files changed, 108 insertions(+), 19 deletions(-) diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index db17fc8a0c9f..bac75acc24ba 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: [digest_type=] [template=] [permit_directio] [appraise_type=] [appraise_flag=] [appraise_algos=] [keyrings=] @@ -138,6 +138,12 @@ 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 5b7a21237fea..5b0b2a596cee 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -1987,25 +1987,27 @@ 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 73917413365b..b04733a5d066 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -93,6 +93,8 @@ struct ima_rule_entry { void *rule; /* LSM file metadata specific */ char *args_p; /* audit value */ int type; /* audit type */ + int rules_lsm; /* which LSM rule applies to */ + bool lsm_specific; /* true if lsm is specified */ } lsm[MAX_LSM_RULES]; char *fsname; struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */ @@ -285,6 +287,30 @@ static int __init default_appraise_policy_setup(char *str) } __setup("ima_appraise_tcb", default_appraise_policy_setup); +static int default_rules_lsm __ro_after_init = LSMBLOB_INVALID; + +static int __init ima_rules_lsm_init(char *str) +{ + const char *oldstr; + int newdrl; + + newdrl = lsm_name_to_slot(str); + if (newdrl >= 0) { + default_rules_lsm = newdrl; + return 1; + } + + oldstr = lsm_slot_to_name(default_rules_lsm); + if (oldstr) { + pr_err("default ima rule lsm \"%s\" not registered, continue using \"%s\"", + str, oldstr); + return 1; + } + + 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 +382,8 @@ 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->lsm[i].rules_lsm); kfree(entry->lsm[i].args_p); } } @@ -407,7 +434,8 @@ 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->lsm[i].rules_lsm); if (!nentry->lsm[i].rule) pr_warn("rule for LSM \'%s\' is undefined\n", nentry->lsm[i].args_p); @@ -623,14 +651,16 @@ 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->lsm[i].rules_lsm); 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->lsm[i].rules_lsm); break; default: break; @@ -1026,7 +1056,7 @@ enum policy_opt { Opt_digest_type, 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 = { @@ -1074,6 +1104,7 @@ static const match_table_t policy_tokens = { {Opt_pcr, "pcr=%s"}, {Opt_template, "template=%s"}, {Opt_keyrings, "keyrings=%s"}, + {Opt_lsm, "lsm=%s"}, {Opt_label, "label=%s"}, {Opt_err, NULL} }; @@ -1093,7 +1124,8 @@ 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->lsm[lsm_rule].rules_lsm); if (!entry->lsm[lsm_rule].rule) { pr_warn("rule for LSM \'%s\' is undefined\n", entry->lsm[lsm_rule].args_p); @@ -1833,6 +1865,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) &(template_desc->num_fields)); entry->template = template_desc; break; + case Opt_lsm: { + int i; + + result = lsm_name_to_slot(args[0].from); + if (result < 0) { + for (i = 0; i < MAX_LSM_RULES; i++) + entry->lsm[i].args_p = NULL; + result = -EINVAL; + break; + } + for (i = 0; i < MAX_LSM_RULES; i++) { + entry->lsm[i].rules_lsm = result; + entry->lsm[i].lsm_specific = true; + } + result = 0; + break; + } case Opt_err: ima_log_string(ab, "UNKNOWN", p); result = -EINVAL; @@ -1878,6 +1927,7 @@ 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; @@ -1895,6 +1945,11 @@ ssize_t ima_parse_add_rule(char *rule) INIT_LIST_HEAD(&entry->list); + for (i = 0; i < MAX_LSM_RULES; i++) { + entry->lsm[i].rules_lsm = default_rules_lsm; + entry->lsm[i].lsm_specific = false; + } + result = ima_parse_rule(p, entry); if (result) { ima_free_rule(entry); @@ -2205,6 +2260,9 @@ int ima_policy_show(struct seq_file *m, void *v) entry->lsm[i].args_p); break; } + if (entry->lsm[i].lsm_specific) + seq_printf(m, pt(Opt_lsm), + lsm_slot_to_name(entry->lsm[i].rules_lsm)); seq_puts(m, " "); } } diff --git a/security/security.c b/security/security.c index 37c14572501e..141922732d10 100644 --- a/security/security.c +++ b/security/security.c @@ -2722,19 +2722,42 @@ 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 */