* [PATCH] integrity: Always reference the blacklist keyring with apprasial
@ 2023-06-30 16:57 Eric Snowberg
2023-07-04 12:30 ` Mimi Zohar
0 siblings, 1 reply; 3+ messages in thread
From: Eric Snowberg @ 2023-06-30 16:57 UTC (permalink / raw)
To: zohar
Cc: dmitry.kasatkin, paul, jmorris, serge, roberto.sassu,
eric.snowberg, kanth.ghatraju, konrad.wilk, linux-kernel,
linux-integrity, linux-security-module
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(-)
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;
}
--
2.39.3
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] integrity: Always reference the blacklist keyring with apprasial
2023-06-30 16:57 [PATCH] integrity: Always reference the blacklist keyring with apprasial Eric Snowberg
@ 2023-07-04 12:30 ` Mimi Zohar
2023-07-05 21:30 ` Eric Snowberg
0 siblings, 1 reply; 3+ messages in thread
From: Mimi Zohar @ 2023-07-04 12:30 UTC (permalink / raw)
To: Eric Snowberg
Cc: dmitry.kasatkin, paul, jmorris, serge, roberto.sassu,
kanth.ghatraju, konrad.wilk, linux-kernel, linux-integrity,
linux-security-module, Nayna Jain
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.
--
thanks,
Mimi
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] integrity: Always reference the blacklist keyring with apprasial
2023-07-04 12:30 ` Mimi Zohar
@ 2023-07-05 21:30 ` Eric Snowberg
0 siblings, 0 replies; 3+ messages in thread
From: Eric Snowberg @ 2023-07-05 21:30 UTC (permalink / raw)
To: Mimi Zohar
Cc: dmitry.kasatkin@gmail.com, paul@paul-moore.com, jmorris@namei.org,
serge@hallyn.com, Roberto Sassu, Kanth Ghatraju, Konrad Wilk,
linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org, Nayna Jain
> 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.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2023-07-04 12:30 ` Mimi Zohar
2023-07-05 21:30 ` Eric Snowberg
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