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authorCasey Schaufler <casey@schaufler-ca.com>2015-03-21 18:26:40 -0700
committerCasey Schaufler <casey@schaufler-ca.com>2015-03-23 13:21:34 -0700
commitbf4b2fee99799780ea3dbb6d79d1909b3e32be13 (patch)
tree70224834f619caa3bf5abd39a7334f5b77bf5656 /security/smack/smack_access.c
parent7fc5f36e980a8f4830efdae3858f6e64eee538b7 (diff)
downloadlinux-bf4b2fee99799780ea3dbb6d79d1909b3e32be13.tar.gz
Smack: Allow an unconfined label in bringup mode
I have vehemently opposed adding a "permissive" mode to Smack for the simple reasons that it would be subject to massive abuse and that developers refuse to turn it off come product release. I still believe that this is true, and still refuse to add a general "permissive mode". So don't ask again. Bumjin Im suggested an approach that addresses most of the concerns, and I have implemented it here. I still believe that we'd be better off without this sort of thing, but it looks like this minimizes the abuse potential. Firstly, you have to configure Smack Bringup Mode. That allows for "release" software to be ammune from abuse. Second, only one label gets to be "permissive" at a time. You can use it for debugging, but that's about it. A label written to smackfs/unconfined is treated specially. If either the subject or object label of an access check matches the "unconfined" label, and the access would not have been allowed otherwise an audit record and a console message are generated. The audit record "request" string is marked with either "(US)" or "(UO)", to indicate that the request was granted because of an unconfined label. The fact that an inode was accessed by an unconfined label is remembered, and subsequent accesses to that "impure" object are noted in the log. The impurity is not stored in the filesystem, so a file mislabled as a side effect of using an unconfined label may still cause concern after a reboot. So, it's there, it's dangerous, but so many application developers seem incapable of living without it I have given in. I've tried to make it as safe as I can, but in the end it's still a chain saw. Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Diffstat (limited to 'security/smack/smack_access.c')
-rw-r--r--security/smack/smack_access.c43
1 files changed, 33 insertions, 10 deletions
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 1158430f5bb9..0f410fc56e33 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -130,7 +130,8 @@ int smk_access(struct smack_known *subject, struct smack_known *object,
/*
* Hardcoded comparisons.
- *
+ */
+ /*
* A star subject can't access any object.
*/
if (subject == &smack_known_star) {
@@ -189,10 +190,20 @@ int smk_access(struct smack_known *subject, struct smack_known *object,
* succeed because of "b" rules.
*/
if (may & MAY_BRINGUP)
- rc = MAY_BRINGUP;
+ rc = SMACK_BRINGUP_ALLOW;
#endif
out_audit:
+
+#ifdef CONFIG_SECURITY_SMACK_BRINGUP
+ if (rc < 0) {
+ if (object == smack_unconfined)
+ rc = SMACK_UNCONFINED_OBJECT;
+ if (subject == smack_unconfined)
+ rc = SMACK_UNCONFINED_SUBJECT;
+ }
+#endif
+
#ifdef CONFIG_AUDIT
if (a)
smack_log(subject->smk_known, object->smk_known,
@@ -338,19 +349,16 @@ static void smack_log_callback(struct audit_buffer *ab, void *a)
void smack_log(char *subject_label, char *object_label, int request,
int result, struct smk_audit_info *ad)
{
+#ifdef CONFIG_SECURITY_SMACK_BRINGUP
+ char request_buffer[SMK_NUM_ACCESS_TYPE + 5];
+#else
char request_buffer[SMK_NUM_ACCESS_TYPE + 1];
+#endif
struct smack_audit_data *sad;
struct common_audit_data *a = &ad->a;
-#ifdef CONFIG_SECURITY_SMACK_BRINGUP
- /*
- * The result may be positive in bringup mode.
- */
- if (result > 0)
- result = 0;
-#endif
/* check if we have to log the current event */
- if (result != 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
+ if (result < 0 && (log_policy & SMACK_AUDIT_DENIED) == 0)
return;
if (result == 0 && (log_policy & SMACK_AUDIT_ACCEPT) == 0)
return;
@@ -364,6 +372,21 @@ void smack_log(char *subject_label, char *object_label, int request,
smack_str_from_perm(request_buffer, request);
sad->subject = subject_label;
sad->object = object_label;
+#ifdef CONFIG_SECURITY_SMACK_BRINGUP
+ /*
+ * The result may be positive in bringup mode.
+ * A positive result is an allow, but not for normal reasons.
+ * Mark it as successful, but don't filter it out even if
+ * the logging policy says to do so.
+ */
+ if (result == SMACK_UNCONFINED_SUBJECT)
+ strcat(request_buffer, "(US)");
+ else if (result == SMACK_UNCONFINED_OBJECT)
+ strcat(request_buffer, "(UO)");
+
+ if (result > 0)
+ result = 0;
+#endif
sad->request = request_buffer;
sad->result = result;