diff mbox series

[v2] integrity: Always reference the blacklist keyring with apprasial

Message ID 20230705225229.1435691-1-eric.snowberg@oracle.com
State New
Headers
Series [v2] integrity: Always reference the blacklist keyring with apprasial |

Commit Message

Eric Snowberg July 5, 2023, 10:52 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>
---
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(-)

Comments

Mimi Zohar July 12, 2023, 5:40 p.m. UTC | #1 
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.
Eric Snowberg July 12, 2023, 9:12 p.m. UTC | #2 
> 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.
Mimi Zohar July 12, 2023, 9:33 p.m. UTC | #3 
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".
Eric Snowberg July 13, 2023, 3:25 p.m. UTC | #4 
> 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 mbox series

Patch

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);