diff mbox series

[v4] integrity: Always reference the blacklist keyring with appraisal

Message ID 20230726211725.393056-1-eric.snowberg@oracle.com
State New
Headers
Series [v4] integrity: Always reference the blacklist keyring with appraisal |

Commit Message

Eric Snowberg July 26, 2023, 9:17 p.m. UTC 
  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>
---
v4 changes:
  Fixed typo
  Also did some performance testing with this patch. With the associative array
  implementation used within the keyring code, there doesn't seem to be much of a
  difference between doing  an appraisal with an empty blacklist keyring and one
  containing 1500 entries.  At this time it is unknown how many entries a user
  would place in this keyring, but this seemed like a bigger number than most use
  cases.  With the 1500 entries, there were only 7 lookups to get through the
  entire list for a file not contained within it.  For something that was
  on the list, there was an average of 4 lookups and a single string compare.
  Based on this testing, IMHO, there could be a lot more entries added to the
  blacklist keyring without any real performance issues.

v3 changes:
  No longer display appraise_flag=check_blacklist in the policy

v2 changes:
  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   | 17 +++++------------
 4 files changed, 19 insertions(+), 24 deletions(-)

Comments

Mimi Zohar July 27, 2023, 5:36 p.m. UTC | #1 
On Wed, 2023-07-26 at 17:17 -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>
> ---
> v4 changes:
>   Fixed typo
>   Also did some performance testing with this patch. With the associative array
>   implementation used within the keyring code, there doesn't seem to be much of a
>   difference between doing  an appraisal with an empty blacklist keyring and one
>   containing 1500 entries.  At this time it is unknown how many entries a user
>   would place in this keyring, but this seemed like a bigger number than most use
>   cases.  With the 1500 entries, there were only 7 lookups to get through the
>   entire list for a file not contained within it.  For something that was
>   on the list, there was an average of 4 lookups and a single string compare.
>   Based on this testing, IMHO, there could be a lot more entries added to the
>   blacklist keyring without any real performance issues.

Thank you for the blacklist performance testing.   The patch is now
queued in next-integrity-testing.

--
thanks,

Mimib
Nayna July 31, 2023, 5:04 p.m. UTC | #2 
On 7/26/23 17:17, 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>
> ---
> v4 changes:
>    Fixed typo
>    Also did some performance testing with this patch. With the associative array
>    implementation used within the keyring code, there doesn't seem to be much of a
>    difference between doing  an appraisal with an empty blacklist keyring and one
>    containing 1500 entries.  At this time it is unknown how many entries a user
>    would place in this keyring, but this seemed like a bigger number than most use
>    cases.  With the 1500 entries, there were only 7 lookups to get through the
>    entire list for a file not contained within it.  For something that was
>    on the list, there was an average of 4 lookups and a single string compare.
>    Based on this testing, IMHO, there could be a lot more entries added to the
>    blacklist keyring without any real performance issues.

Nice to see the performance test results.

Reviewed-by: Nayna Jain <nayna@linux.ibm.com>

Thanks & Regards,

      - Nayna

>
> v3 changes:
>    No longer display appraise_flag=check_blacklist in the policy
>
> v2 changes:
>    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   | 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();
diff mbox series

Patch

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();