ima: Support additional conditionals in the KEXEC_CMDLINE hook function

Take the properties of the kexec kernel's inode and the current task
ownership into consideration when matching a KEXEC_CMDLINE operation to
the rules in the IMA policy. This allows for some uniformity when
writing IMA policy rules for KEXEC_KERNEL_CHECK, KEXEC_INITRAMFS_CHECK,
and KEXEC_CMDLINE operations.

Prior to this patch, it was not possible to write a set of rules like
this:

 dont_measure func=KEXEC_KERNEL_CHECK obj_type=foo_t
 dont_measure func=KEXEC_INITRAMFS_CHECK obj_type=foo_t
 dont_measure func=KEXEC_CMDLINE obj_type=foo_t
 measure func=KEXEC_KERNEL_CHECK
 measure func=KEXEC_INITRAMFS_CHECK
 measure func=KEXEC_CMDLINE

The inode information associated with the kernel being loaded by a
kexec_kernel_load(2) syscall can now be included in the decision to
measure or not

Additonally, the uid, euid, and subj_* conditionals can also now be
used in KEXEC_CMDLINE rules. There was no technical reason as to why
those conditionals weren't being considered previously other than
ima_match_rules() didn't have a valid inode to use so it immediately
bailed out for KEXEC_CMDLINE operations rather than going through the
full list of conditional comparisons.

Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: kexec@lists.infradead.org
Reviewed-by: Lakshmi Ramasubramanian <nramas@linux.microsoft.com>
Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>

1 files changed, 6 insertions, 11 deletions

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index dcd1aaac4ff0..9284055ee13a 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -443,13 +443,9 @@ static bool ima_match_rules(struct ima_rule_entry *rule, struct inode *inode,
 {
 	int i;
 
-	if ((func == KEXEC_CMDLINE) || (func == KEY_CHECK)) {
-		if ((rule->flags & IMA_FUNC) && (rule->func == func)) {
-			if (func == KEY_CHECK)
-				return ima_match_keyring(rule, keyring, cred);
-			return true;
-		}
-		return false;
+	if (func == KEY_CHECK) {
+		return (rule->flags & IMA_FUNC) && (rule->func == func) &&
+		       ima_match_keyring(rule, keyring, cred);
 	}
 	if ((rule->flags & IMA_FUNC) &&
 	    (rule->func != func && func != POST_SETATTR))
@@ -1035,10 +1031,9 @@ static bool ima_validate_rule(struct ima_rule_entry *entry)
 		if (entry->action & ~(MEASURE | DONT_MEASURE))
 			return false;
 
-		if (entry->flags & ~(IMA_FUNC | IMA_PCR))
-			return false;
-
-		if (ima_rule_contains_lsm_cond(entry))
+		if (entry->flags & ~(IMA_FUNC | IMA_FSMAGIC | IMA_UID |
+				     IMA_FOWNER | IMA_FSUUID | IMA_EUID |
+				     IMA_PCR | IMA_FSNAME))
 			return false;
 
 		break;