| Message ID | 20230630165712.909767-1-eric.snowberg@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | integrity: Always reference the blacklist keyring with apprasial | expand |
Hi Eric, On Fri, 2023-06-30 at 12:57 -0400, Eric Snowberg wrote: > 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. Prior to the above change, keys could be revoked. Finer granularity was added based on file hash to block loading a specific kexec kernel image on powerpc. My concern back then with making this generic was scalability and performance. > 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 <eric.snowberg@oracle.com> Agreed, support for finer revocaton granularity based on file hash is needed. > --- > Documentation/ABI/testing/ima_policy | 6 +++--- > security/integrity/ima/ima_appraise.c | 12 +++++++----- > security/integrity/ima/ima_policy.c | 10 +++++----- > 3 files changed, 15 insertions(+), 13 deletions(-) > > diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy > index 49db0ff288e5..a712c396f6e9 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 apprasial functions set it by default. > digest_type:= verity > Require fs-verity's file digest instead of the > regular IMA file hash. > 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 3ca8b7348c2e..71e270141101 100644 > --- a/security/integrity/ima/ima_policy.c > +++ b/security/integrity/ima/ima_policy.c > @@ -1279,7 +1279,7 @@ 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; > @@ -1354,7 +1354,7 @@ 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; > > /* > @@ -1802,11 +1802,11 @@ 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) && > @@ -1815,7 +1815,7 @@ 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; > } Please update the "case Opt_appraise_flag:" and remove "appraise_flag=" in the powerpc arch specific policy rules.
> On Jul 4, 2023, at 6:30 AM, Mimi Zohar <zohar@linux.ibm.com> wrote: > > Please update the "case Opt_appraise_flag:" and remove "appraise_flag=" > in the powerpc arch specific policy rules. I will make both changes in V2, thanks.
diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy index 49db0ff288e5..a712c396f6e9 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 apprasial functions set it by default. digest_type:= verity Require fs-verity's file digest instead of the regular IMA file hash. 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 3ca8b7348c2e..71e270141101 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -1279,7 +1279,7 @@ 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; @@ -1354,7 +1354,7 @@ 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; /* @@ -1802,11 +1802,11 @@ 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) && @@ -1815,7 +1815,7 @@ 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; }
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 <eric.snowberg@oracle.com> --- Documentation/ABI/testing/ima_policy | 6 +++--- security/integrity/ima/ima_appraise.c | 12 +++++++----- security/integrity/ima/ima_policy.c | 10 +++++----- 3 files changed, 15 insertions(+), 13 deletions(-)