Commit f20765fd authored by Eric Snowberg's avatar Eric Snowberg Committed by Mimi Zohar
Browse files

integrity: Always reference the blacklist keyring with appraisal 



Commit 273df864 ("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: default avatarEric Snowberg <eric.snowberg@oracle.com>
Reviewed-by: default avatarNayna Jain <nayna@linux.ibm.com>
Signed-off-by: default avatarMimi Zohar <zohar@linux.ibm.com>
parent 5087fd9e

Documentation/ABI/testing/ima_policy

+3 −3
Original line number Diff line number Diff line
@@ -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.

arch/powerpc/kernel/ima_arch.c

+4 −4
Original line number Diff line number Diff line
@@ -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

};

security/integrity/ima/ima_appraise.c

+7 −5
Original line number Diff line number Diff line
@@ -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);

	} 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;

}

security/integrity/ima/ima_policy.c

+5 −12
Original line number Diff line number Diff line
@@ -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();