[RFC][PATCH v4 1/9] ima: Introduce hook DIGEST_LIST_CHECK

[Roberto Sassu]

From: Roberto Sassu <roberto.sassu at huawei.com>

Introduce DIGEST_LIST_CHECK, a new hook to check the integrity of digest
lists.

The new hook is invoked during a kernel read with the file type
READING_DIGEST LIST, which is done by the Integrity Digest Cache when it is
populating a digest cache with a digest list.

The new hook makes it possible to more precisely measure/appraise the
digest lists read by the kernel, as opposed to using the more generic
FILE_CHECK hook, invoked for every file open.

Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
---
 Documentation/ABI/testing/ima_policy | 1 +
 security/integrity/ima/ima.h         | 1 +
 security/integrity/ima/ima_main.c    | 3 ++-
 security/integrity/ima/ima_policy.c  | 3 +++
 4 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/ima_policy b/Documentation/ABI/testing/ima_policy
index c2385183826c..22237fec5532 100644
--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -36,6 +36,7 @@ Description:
 				[KEXEC_KERNEL_CHECK] [KEXEC_INITRAMFS_CHECK]
 				[KEXEC_CMDLINE] [KEY_CHECK] [CRITICAL_DATA]
 				[SETXATTR_CHECK][MMAP_CHECK_REQPROT]
+				[DIGEST_LIST_CHECK]
 			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
 			       [[^]MAY_EXEC]
 			fsmagic:= hex value
diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h
index 2eaa7f224da4..301f4ddfa487 100644
--- a/security/integrity/ima/ima.h
+++ b/security/integrity/ima/ima.h
@@ -317,6 +317,7 @@ static inline unsigned int ima_hash_key(u8 *digest)
 	hook(KEY_CHECK, key)				\
 	hook(CRITICAL_DATA, critical_data)		\
 	hook(SETXATTR_CHECK, setxattr_check)		\
+	hook(DIGEST_LIST_CHECK, digest_list_check)	\
 	hook(MAX_CHECK, none)
 
 #define __ima_hook_enumify(ENUM, str)	ENUM,
diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c
index f6cc0c7a6244..8f732d3bd024 100644
--- a/security/integrity/ima/ima_main.c
+++ b/security/integrity/ima/ima_main.c
@@ -798,7 +798,8 @@ const int read_idmap[READING_MAX_ID] = {
 	[READING_MODULE] = MODULE_CHECK,
 	[READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK,
 	[READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK,
-	[READING_POLICY] = POLICY_CHECK
+	[READING_POLICY] = POLICY_CHECK,
+	[READING_DIGEST_LIST] = DIGEST_LIST_CHECK,
 };
 
 /**
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 09da8e639239..047d50c2eb57 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -1290,6 +1290,7 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
 	case MODULE_CHECK:
 	case KEXEC_KERNEL_CHECK:
 	case KEXEC_INITRAMFS_CHECK:
+	case DIGEST_LIST_CHECK:
 		if (entry->flags & ~(IMA_FUNC | IMA_MASK | IMA_FSMAGIC |
 				     IMA_UID | IMA_FOWNER | IMA_FSUUID |
 				     IMA_INMASK | IMA_EUID | IMA_PCR |
@@ -1533,6 +1534,8 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 				entry->func = CRITICAL_DATA;
 			else if (strcmp(args[0].from, "SETXATTR_CHECK") == 0)
 				entry->func = SETXATTR_CHECK;
+			else if (strcmp(args[0].from, "DIGEST_LIST_CHECK") == 0)
+				entry->func = DIGEST_LIST_CHECK;
 			else
 				result = -EINVAL;
 			if (!result)
-- 
2.47.0.118.gfd3785337b