[PATCH 3.14 13/44] ima: extend "mask" policy matching support

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mimi Zohar <zohar@linux.vnet.ibm.com>

commit 4351c294b8c1028077280f761e158d167b592974 upstream.

The current "mask" policy option matches files opened as MAY_READ,
MAY_WRITE, MAY_APPEND or MAY_EXEC.  This patch extends the "mask"
option to match files opened containing one of these modes.  For
example, "mask=^MAY_READ" would match files opened read-write.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Dr. Greg Wettstein <gw@idfusion.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 Documentation/ABI/testing/ima_policy |    3 ++-
 security/integrity/ima/ima_policy.c  |   20 +++++++++++++++-----
 2 files changed, 17 insertions(+), 6 deletions(-)

--- a/Documentation/ABI/testing/ima_policy
+++ b/Documentation/ABI/testing/ima_policy
@@ -26,7 +26,8 @@ Description:
 			option:	[[appraise_type=]] [permit_directio]
 
 		base: 	func:= [BPRM_CHECK][MMAP_CHECK][FILE_CHECK][MODULE_CHECK]
-			mask:= [MAY_READ] [MAY_WRITE] [MAY_APPEND] [MAY_EXEC]
+			mask:= [[^]MAY_READ] [[^]MAY_WRITE] [[^]MAY_APPEND]
+			       [[^]MAY_EXEC]
 			fsmagic:= hex value
 			fsuuid:= file system UUID (e.g 8bcbe394-4f13-4144-be8e-5aa9ea2ce2f6)
 			uid:= decimal value
--- a/security/integrity/ima/ima_policy.c
+++ b/security/integrity/ima/ima_policy.c
@@ -27,6 +27,7 @@
 #define IMA_UID		0x0008
 #define IMA_FOWNER	0x0010
 #define IMA_FSUUID	0x0020
+#define IMA_INMASK	0x0040
 #define IMA_EUID	0x0080
 
 #define UNKNOWN		0
@@ -172,6 +173,9 @@ static bool ima_match_rules(struct ima_r
 		return false;
 	if ((rule->flags & IMA_MASK) && rule->mask != mask)
 		return false;
+	if ((rule->flags & IMA_INMASK) &&
+	    (!(rule->mask & mask) && func != POST_SETATTR))
+		return false;
 	if ((rule->flags & IMA_FSMAGIC)
 	    && rule->fsmagic != inode->i_sb->s_magic)
 		return false;
@@ -425,6 +429,7 @@ static void ima_log_string(struct audit_
 static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 {
 	struct audit_buffer *ab;
+	char *from;
 	char *p;
 	int result = 0;
 
@@ -513,18 +518,23 @@ static int ima_parse_rule(char *rule, st
 			if (entry->mask)
 				result = -EINVAL;
 
-			if ((strcmp(args[0].from, "MAY_EXEC")) == 0)
+			from = args[0].from;
+			if (*from == '^')
+				from++;
+
+			if ((strcmp(from, "MAY_EXEC")) == 0)
 				entry->mask = MAY_EXEC;
-			else if (strcmp(args[0].from, "MAY_WRITE") == 0)
+			else if (strcmp(from, "MAY_WRITE") == 0)
 				entry->mask = MAY_WRITE;
-			else if (strcmp(args[0].from, "MAY_READ") == 0)
+			else if (strcmp(from, "MAY_READ") == 0)
 				entry->mask = MAY_READ;
-			else if (strcmp(args[0].from, "MAY_APPEND") == 0)
+			else if (strcmp(from, "MAY_APPEND") == 0)
 				entry->mask = MAY_APPEND;
 			else
 				result = -EINVAL;
 			if (!result)
-				entry->flags |= IMA_MASK;
+				entry->flags |= (*args[0].from == '^')
+				     ? IMA_INMASK : IMA_MASK;
 			break;
 		case Opt_fsmagic:
 			ima_log_string(ab, "fsmagic", args[0].from);