| Message ID | 20230705225229.1435691-1-eric.snowberg@oracle.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | [v2] integrity: Always reference the blacklist keyring with apprasial | expand |
On Wed, 2023-07-05 at 18:52 -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. > > 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> Thanks, Eric. Other than including "appraise_flag=check_blacklist" when displaying the measurement list, it looks good.
> On Jul 12, 2023, at 11:40 AM, Mimi Zohar <zohar@linux.ibm.com> wrote: > > On Wed, 2023-07-05 at 18:52 -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. >> >> 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> > > Thanks, Eric. Other than including "appraise_flag=check_blacklist" > when displaying the measurement list, it looks good. Thanks for your review. I want to make sure I understand the request here. Do you mean you don’t want to see “appraise_flag=check_blacklist” when you cat /sys/kernel/security/ima/policy? Or are you referencing a change in the /sys/kernel/security/ima/ascii_runtime_measurements list? Thanks.
On Wed, 2023-07-12 at 21:12 +0000, Eric Snowberg wrote: > > > On Jul 12, 2023, at 11:40 AM, Mimi Zohar <zohar@linux.ibm.com> wrote: > > > > On Wed, 2023-07-05 at 18:52 -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. > >> > >> 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> > > > > Thanks, Eric. Other than including "appraise_flag=check_blacklist" > > when displaying the measurement list, it looks good. > > Thanks for your review. > > I want to make sure I understand the request here. Do you mean you > don’t want to see “appraise_flag=check_blacklist” when you cat > /sys/kernel/security/ima/policy? Or are you referencing a change in the > /sys/kernel/security/ima/ascii_runtime_measurements list? Thanks. The IMA policy rules as displayed via <securityfs>/ima/policy should not contain “appraise_flag=check_blacklist".
> On Jul 12, 2023, at 3:33 PM, Mimi Zohar <zohar@linux.ibm.com> wrote: > > On Wed, 2023-07-12 at 21:12 +0000, Eric Snowberg wrote: >> >>> On Jul 12, 2023, at 11:40 AM, Mimi Zohar <zohar@linux.ibm.com> wrote: >>> >>> On Wed, 2023-07-05 at 18:52 -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. >>>> >>>> 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> >>> >>> Thanks, Eric. Other than including "appraise_flag=check_blacklist" >>> when displaying the measurement list, it looks good. >> >> Thanks for your review. >> >> I want to make sure I understand the request here. Do you mean you >> don’t want to see “appraise_flag=check_blacklist” when you cat >> /sys/kernel/security/ima/policy? Or are you referencing a change in the >> /sys/kernel/security/ima/ascii_runtime_measurements list? Thanks. > > The IMA policy rules as displayed via <securityfs>/ima/policy should > not contain “appraise_flag=check_blacklist". Ok, I will fix this in v3, 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/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 3ca8b7348c2e..d2c02d2d740e 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) && @@ -1815,18 +1815,13 @@ 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);
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> --- v2 changes requested by Mimi: Update the "case Opt_apprase_flag" Removed "appraise_flag=" in the powerpc arch specific policy rules --- 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 | 15 +++++---------- 4 files changed, 19 insertions(+), 22 deletions(-)