ima: per hook cache integrity appraisal status

With the new IMA policy 'appraise_type=' option, different hooks
can require different methods for appraising a file's integrity.

For example, the existing 'ima_appraise_tcb' policy defines a
generic rule, requiring all root files to be appraised, without
specfying the appraisal method.  A more specific rule could require
all kernel modules, for example, to be signed.

appraise fowner=0 func=MODULE_CHECK appraise_type=imasig
appraise fowner=0

As a result, the integrity appraisal results for the same inode, but
for different hooks, could differ.  This patch caches the integrity
appraisal results on a per hook basis.

Changelog v2:
- Rename ima_cache_status() to ima_set_cache_status()
- Rename and move get_appraise_status() to ima_get_cache_status()
Changelog v0:
- include IMA_APPRAISE/APPRAISED_SUBMASK in IMA_DO/DONE_MASK (Dmitry)
- Support independent MODULE_CHECK appraise status.
- fixed IMA_XXXX_APPRAISE/APPRAISED flags

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@intel.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 1a2543a8ee53..4d7c0ae656d3 100644
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -218,6 +218,25 @@ retry:
 	return true;
 }
 
+/*
+ * In addition to knowing that we need to appraise the file in general,
+ * we need to differentiate between calling hooks.
+ */
+static int get_subaction(int func)
+{
+	switch(func) {
+	case MMAP_CHECK:
+		return IMA_MMAP_APPRAISE;
+	case BPRM_CHECK:
+		return IMA_BPRM_APPRAISE;
+	case MODULE_CHECK:
+		return IMA_MODULE_APPRAISE;
+	case FILE_CHECK:
+	default:
+		return IMA_FILE_APPRAISE;
+	}
+}
+
 /**
  * ima_match_policy - decision based on LSM and other conditions
  * @inode: pointer to an inode for which the policy decision is being made
@@ -248,6 +267,9 @@ int ima_match_policy(struct inode *inode, enum ima_hooks func, int mask,
 		action |= entry->flags & IMA_ACTION_FLAGS;
 
 		action |= entry->action & IMA_DO_MASK;
+		if (entry->action & IMA_APPRAISE)
+			action |= get_subaction(func);
+
 		if (entry->action & IMA_DO_MASK)
 			actmask &= ~(entry->action | entry->action << 1);
 		else