ima: extend "mask" policy matching support

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>
Cc: stable@vger.kernel.org

1 files changed, 15 insertions, 5 deletions

diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c
index 525301cf7d90..b3a2038ed424 100644
--- 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
@@ -187,6 +188,9 @@ static bool ima_match_rules(struct ima_rule_entry *rule,
         if ((rule->flags & IMA_MASK) &&
             (rule->mask != mask && func != POST_SETATTR))
                 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;
@@ -448,6 +452,7 @@ static void ima_log_string(struct audit_buffer *ab, char *key, char *value)
 static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
 {
         struct audit_buffer *ab;
+        char *from;
         char *p;
         int result = 0;
 
@@ -538,18 +543,23 @@ static int ima_parse_rule(char *rule, struct ima_rule_entry *entry)
                         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);