ima: provide 'ima_appraise=log' kernel option

The kernel boot parameter "ima_appraise" currently defines 'off',
'enforce' and 'fix' modes.  When designing a policy and labeling
the system, access to files are either blocked in the default
'enforce' mode or automatically fixed in the 'fix' mode.  It is
beneficial to be able to run the system in a logging only mode,
without fixing it, in order to properly analyze the system. This
patch adds a 'log' mode to run the system in a permissive mode and
log the appraisal results.

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

Documentation/kernel-parameters.txt

@@ -1292,7 +1292,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			Set number of hash buckets for inode cache.
 
 	ima_appraise=	[IMA] appraise integrity measurements
-			Format: { "off" | "enforce" | "fix" }
+			Format: { "off" | "enforce" | "fix" | "log" }
 			default: "enforce"
 
 	ima_appraise_tcb [IMA]

security/integrity/ima/ima.h

@@ -159,8 +159,9 @@ void ima_delete_rules(void);
 /* Appraise integrity measurements */
 #define IMA_APPRAISE_ENFORCE	0x01
 #define IMA_APPRAISE_FIX	0x02
-#define IMA_APPRAISE_MODULES	0x04
-#define IMA_APPRAISE_FIRMWARE	0x08
+#define IMA_APPRAISE_LOG	0x04
+#define IMA_APPRAISE_MODULES	0x08
+#define IMA_APPRAISE_FIRMWARE	0x10
 
 #ifdef CONFIG_IMA_APPRAISE
 int ima_appraise_measurement(int func, struct integrity_iint_cache *iint,

security/integrity/ima/ima_appraise.c

@@ -23,6 +23,8 @@ static int __init default_appraise_setup(char *str)
 {
 	if (strncmp(str, "off", 3) == 0)
 		ima_appraise = 0;
+	else if (strncmp(str, "log", 3) == 0)
+		ima_appraise = IMA_APPRAISE_LOG;
 	else if (strncmp(str, "fix", 3) == 0)
 		ima_appraise = IMA_APPRAISE_FIX;
 	return 1;