SELinux: Use dentry name in new object labeling

Currently SELinux has rules which label new objects according to 3 criteria.
The label of the process creating the object, the label of the parent
directory, and the type of object (reg, dir, char, block, etc.)  This patch
adds a 4th criteria, the dentry name, thus we can distinguish between
creating a file in an etc_t directory called shadow and one called motd.

There is no file globbing, regex parsing, or anything mystical.  Either the
policy exactly (strcmp) matches the dentry name of the object or it doesn't.
This patch has no changes from today if policy does not implement the new
rules.

Signed-off-by: Eric Paris <eparis@redhat.com>

1 files changed, 31 insertions, 14 deletions

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index a03cfaf0ee0..2e36e03c21f 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -1343,10 +1343,27 @@ out:
 	return -EACCES;
 }
 
+static void filename_compute_type(struct policydb *p, struct context *newcontext,
+				  u32 scon, u32 tcon, u16 tclass,
+				  const struct qstr *qstr)
+{
+	struct filename_trans *ft;
+	for (ft = p->filename_trans; ft; ft = ft->next) {
+		if (ft->stype == scon &&
+		    ft->ttype == tcon &&
+		    ft->tclass == tclass &&
+		    !strcmp(ft->name, qstr->name)) {
+			newcontext->type = ft->otype;
+			return;
+		}
+	}
+}
+
 static int security_compute_sid(u32 ssid,
 				u32 tsid,
 				u16 orig_tclass,
 				u32 specified,
+				const struct qstr *qstr,
 				u32 *out_sid,
 				bool kern)
 {
@@ -1442,6 +1459,11 @@ static int security_compute_sid(u32 ssid,
 		newcontext.type = avdatum->data;
 	}
 
+	/* if we have a qstr this is a file trans check so check those rules */
+	if (qstr)
+		filename_compute_type(&policydb, &newcontext, scontext->type,
+				      tcontext->type, tclass, qstr);
+
 	/* Check for class-specific changes. */
 	if  (tclass == policydb.process_class) {
 		if (specified & AVTAB_TRANSITION) {
@@ -1495,22 +1517,17 @@ out:
  * if insufficient memory is available, or %0 if the new SID was
  * computed successfully.
  */
-int security_transition_sid(u32 ssid,
-			    u32 tsid,
-			    u16 tclass,
-			    u32 *out_sid)
+int security_transition_sid(u32 ssid, u32 tsid, u16 tclass,
+			    const struct qstr *qstr, u32 *out_sid)
 {
 	return security_compute_sid(ssid, tsid, tclass, AVTAB_TRANSITION,
-				    out_sid, true);
+				    qstr, out_sid, true);
 }
 
-int security_transition_sid_user(u32 ssid,
-				 u32 tsid,
-				 u16 tclass,
-				 u32 *out_sid)
+int security_transition_sid_user(u32 ssid, u32 tsid, u16 tclass, u32 *out_sid)
 {
 	return security_compute_sid(ssid, tsid, tclass, AVTAB_TRANSITION,
-				    out_sid, false);
+				    NULL, out_sid, false);
 }
 
 /**
@@ -1531,8 +1548,8 @@ int security_member_sid(u32 ssid,
 			u16 tclass,
 			u32 *out_sid)
 {
-	return security_compute_sid(ssid, tsid, tclass, AVTAB_MEMBER, out_sid,
-				    false);
+	return security_compute_sid(ssid, tsid, tclass, AVTAB_MEMBER, NULL,
+				    out_sid, false);
 }
 
 /**
@@ -1553,8 +1570,8 @@ int security_change_sid(u32 ssid,
 			u16 tclass,
 			u32 *out_sid)
 {
-	return security_compute_sid(ssid, tsid, tclass, AVTAB_CHANGE, out_sid,
-				    false);
+	return security_compute_sid(ssid, tsid, tclass, AVTAB_CHANGE, NULL,
+				    out_sid, false);
 }
 
 /* Clone the SID into the new SID table. */