From f20765fdfdc2c8f47b41cb08489fdad3194a8465 Mon Sep 17 00:00:00 2001 From: Eric Snowberg Date: Wed, 26 Jul 2023 17:17:25 -0400 Subject: integrity: Always reference the blacklist keyring with appraisal Commit 273df864cf746 ("ima: Check against blacklisted hashes for files with modsig") introduced an appraise_flag option for referencing the blacklist keyring. Any matching binary found on this keyring fails signature validation. This flag only works with module appended signatures. An important part of a PKI infrastructure is to have the ability to do revocation at a later time should a vulnerability be found. Expand the revocation flag usage to all appraisal functions. The flag is now enabled by default. Setting the flag with an IMA policy has been deprecated. Without a revocation capability like this in place, only authenticity can be maintained. With this change, integrity can now be achieved with digital signature based IMA appraisal. Signed-off-by: Eric Snowberg Reviewed-by: Nayna Jain Signed-off-by: Mimi Zohar --- Documentation/ABI/testing/ima_policy | 6 +++--- arch/powerpc/kernel/ima_arch.c | 8 ++++---- security/integrity/ima/ima_appraise.c | 12 +++++++----- security/integrity/ima/ima_policy.c | 17 +++++------------ 4 files changed, 19 insertions(+), 24 deletions(-) diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index 49db0ff288e5..c2385183826c 100644 --- a/Documentation/ABI/testing/ima_policy +++ b/Documentation/ABI/testing/ima_policy @@ -57,9 +57,9 @@ Description: stored in security.ima xattr. Requires specifying "digest_type=verity" first.) - appraise_flag:= [check_blacklist] - Currently, blacklist check is only for files signed with appended - signature. + appraise_flag:= [check_blacklist] (deprecated) + Setting the check_blacklist flag is no longer necessary. + All appraisal functions set it by default. digest_type:= verity Require fs-verity's file digest instead of the regular IMA file hash. diff --git a/arch/powerpc/kernel/ima_arch.c b/arch/powerpc/kernel/ima_arch.c index 957abd592075..b7029beed847 100644 --- a/arch/powerpc/kernel/ima_arch.c +++ b/arch/powerpc/kernel/ima_arch.c @@ -23,9 +23,9 @@ bool arch_ima_get_secureboot(void) * is not enabled. */ static const char *const secure_rules[] = { - "appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig", + "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig", #ifndef CONFIG_MODULE_SIG - "appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig", + "appraise func=MODULE_CHECK appraise_type=imasig|modsig", #endif NULL }; @@ -49,9 +49,9 @@ static const char *const trusted_rules[] = { static const char *const secure_and_trusted_rules[] = { "measure func=KEXEC_KERNEL_CHECK template=ima-modsig", "measure func=MODULE_CHECK template=ima-modsig", - "appraise func=KEXEC_KERNEL_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig", + "appraise func=KEXEC_KERNEL_CHECK appraise_type=imasig|modsig", #ifndef CONFIG_MODULE_SIG - "appraise func=MODULE_CHECK appraise_flag=check_blacklist appraise_type=imasig|modsig", + "appraise func=MODULE_CHECK appraise_type=imasig|modsig", #endif NULL }; diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 491c1aca0b1c..870dde67707b 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -458,11 +458,13 @@ int ima_check_blacklist(struct integrity_iint_cache *iint, ima_get_modsig_digest(modsig, &hash_algo, &digest, &digestsize); rc = is_binary_blacklisted(digest, digestsize); - if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) - process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize, - "blacklisted-hash", NONE, - pcr, NULL, false, NULL, 0); - } + } else if (iint->flags & IMA_DIGSIG_REQUIRED && iint->ima_hash) + rc = is_binary_blacklisted(iint->ima_hash->digest, iint->ima_hash->length); + + if ((rc == -EPERM) && (iint->flags & IMA_MEASURE)) + process_buffer_measurement(&nop_mnt_idmap, NULL, digest, digestsize, + "blacklisted-hash", NONE, + pcr, NULL, false, NULL, 0); return rc; } diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index c9b3bd8f1bb9..69452b79686b 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -1280,7 +1280,7 @@ static bool ima_validate_rule(struct ima_rule_entry *entry) IMA_FSNAME | IMA_GID | IMA_EGID | IMA_FGROUP | IMA_DIGSIG_REQUIRED | IMA_PERMIT_DIRECTIO | IMA_VALIDATE_ALGOS | - IMA_VERITY_REQUIRED)) + IMA_CHECK_BLACKLIST | IMA_VERITY_REQUIRED)) return false; break; @@ -1355,7 +1355,7 @@ static bool ima_validate_rule(struct ima_rule_entry *entry) /* Ensure that combinations of flags are compatible with each other */ if (entry->flags & IMA_CHECK_BLACKLIST && - !(entry->flags & IMA_MODSIG_ALLOWED)) + !(entry->flags & IMA_DIGSIG_REQUIRED)) return false; /* @@ -1803,11 +1803,11 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) if (entry->flags & IMA_VERITY_REQUIRED) result = -EINVAL; else - entry->flags |= IMA_DIGSIG_REQUIRED; + entry->flags |= IMA_DIGSIG_REQUIRED | IMA_CHECK_BLACKLIST; } else if (strcmp(args[0].from, "sigv3") == 0) { /* Only fsverity supports sigv3 for now */ if (entry->flags & IMA_VERITY_REQUIRED) - entry->flags |= IMA_DIGSIG_REQUIRED; + entry->flags |= IMA_DIGSIG_REQUIRED | IMA_CHECK_BLACKLIST; else result = -EINVAL; } else if (IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG) && @@ -1816,18 +1816,13 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry) result = -EINVAL; else entry->flags |= IMA_DIGSIG_REQUIRED | - IMA_MODSIG_ALLOWED; + IMA_MODSIG_ALLOWED | IMA_CHECK_BLACKLIST; } else { result = -EINVAL; } break; case Opt_appraise_flag: ima_log_string(ab, "appraise_flag", args[0].from); - if (IS_ENABLED(CONFIG_IMA_APPRAISE_MODSIG) && - strstr(args[0].from, "blacklist")) - entry->flags |= IMA_CHECK_BLACKLIST; - else - result = -EINVAL; break; case Opt_appraise_algos: ima_log_string(ab, "appraise_algos", args[0].from); @@ -2271,8 +2266,6 @@ int ima_policy_show(struct seq_file *m, void *v) } if (entry->flags & IMA_VERITY_REQUIRED) seq_puts(m, "digest_type=verity "); - if (entry->flags & IMA_CHECK_BLACKLIST) - seq_puts(m, "appraise_flag=check_blacklist "); if (entry->flags & IMA_PERMIT_DIRECTIO) seq_puts(m, "permit_directio "); rcu_read_unlock(); -- cgit v1.2.3-59-g8ed1b