selinux: change the handling of unknown classes

If allow_unknown==deny, SELinux treats an undefined kernel security
class as an error condition rather than as a typical permission denial
and thus does not allow permissions on undefined classes even when in
permissive mode.  Change the SELinux logic so that this case is handled
as a typical permission denial, subject to the usual permissive mode and
permissive domain handling.

Also drop the 'requested' argument from security_compute_av() and
helpers as it is a legacy of the original security server interface and
is unused.

Changes:
- Handle permissive domains consistently by moving up the test for a
permissive domain.
- Make security_compute_av_user() consistent with security_compute_av();
the only difference now is that security_compute_av() performs mapping
between the kernel-private class and permission indices and the policy
values.  In the userspace case, this mapping is handled by libselinux.
- Moved avd_init inside the policy lock.

Based in part on a patch by Paul Moore <paul.moore@hp.com>.

Reported-by: Andrew Worsley <amworsley@gmail.com>
Signed-off-by:  Stephen D. Smalley <sds@tycho.nsa.gov>
Reviewed-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>

security/selinux/avc.c

@@ -746,9 +746,7 @@ int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 		else
 			avd = &avd_entry;
 
-		rc = security_compute_av(ssid, tsid, tclass, requested, avd);
-		if (rc)
-			goto out;
+		security_compute_av(ssid, tsid, tclass, avd);
 		rcu_read_lock();
 		node = avc_insert(ssid, tsid, tclass, avd);
 	} else {
@@ -770,7 +768,6 @@ int avc_has_perm_noaudit(u32 ssid, u32 tsid,
 	}
 
 	rcu_read_unlock();
-out:
 	return rc;
 }
 

security/selinux/include/security.h

@@ -96,13 +96,11 @@ struct av_decision {
 /* definitions of av_decision.flags */
 #define AVD_FLAGS_PERMISSIVE	0x0001
 
-int security_compute_av(u32 ssid, u32 tsid,
-			u16 tclass, u32 requested,
-			struct av_decision *avd);
+void security_compute_av(u32 ssid, u32 tsid,
+			 u16 tclass, struct av_decision *avd);
 
-int security_compute_av_user(u32 ssid, u32 tsid,
-			     u16 tclass, u32 requested,
-			     struct av_decision *avd);
+void security_compute_av_user(u32 ssid, u32 tsid,
+			     u16 tclass, struct av_decision *avd);
 
 int security_transition_sid(u32 ssid, u32 tsid,
 			    u16 tclass, u32 *out_sid);

security/selinux/selinuxfs.c

@@ -494,7 +494,6 @@ static ssize_t sel_write_access(struct file *file, char *buf, size_t size)
 	char *scon, *tcon;
 	u32 ssid, tsid;
 	u16 tclass;
-	u32 req;
 	struct av_decision avd;
 	ssize_t length;
 
@@ -512,7 +511,7 @@ static ssize_t sel_write_access(struct file *file, char *buf, size_t size)
 		goto out;
 
 	length = -EINVAL;
-	if (sscanf(buf, "%s %s %hu %x", scon, tcon, &tclass, &req) != 4)
+	if (sscanf(buf, "%s %s %hu", scon, tcon, &tclass) != 3)
 		goto out2;
 
 	length = security_context_to_sid(scon, strlen(scon)+1, &ssid);
@@ -522,9 +521,7 @@ static ssize_t sel_write_access(struct file *file, char *buf, size_t size)
 	if (length < 0)
 		goto out2;
 
-	length = security_compute_av_user(ssid, tsid, tclass, req, &avd);
-	if (length < 0)
-		goto out2;
+	security_compute_av_user(ssid, tsid, tclass, &avd);
 
 	length = scnprintf(buf, SIMPLE_TRANSACTION_LIMIT,
 			  "%x %x %x %x %u %x",

security/selinux/ss/services.c

@@ -87,11 +87,10 @@ static u32 latest_granting;
 static int context_struct_to_string(struct context *context, char **scontext,
 				    u32 *scontext_len);
 
-static int context_struct_compute_av(struct context *scontext,
-				     struct context *tcontext,
-				     u16 tclass,
-				     u32 requested,
-				     struct av_decision *avd);
+static void context_struct_compute_av(struct context *scontext,
+				      struct context *tcontext,
+				      u16 tclass,
+				      struct av_decision *avd);
 
 struct selinux_mapping {
 	u16 value; /* policy value */
@@ -196,23 +195,6 @@ static u16 unmap_class(u16 tclass)
 	return tclass;
 }
 
-static u32 unmap_perm(u16 tclass, u32 tperm)
-{
-	if (tclass < current_mapping_size) {
-		unsigned i;
-		u32 kperm = 0;
-
-		for (i = 0; i < current_mapping[tclass].num_perms; i++)
-			if (tperm & (1<<i)) {
-				kperm |= current_mapping[tclass].perms[i];
-				tperm &= ~(1<<i);
-			}
-		return kperm;
-	}
-
-	return tperm;
-}
-
 static void map_decision(u16 tclass, struct av_decision *avd,
 			 int allow_unknown)
 {
@@ -532,7 +514,6 @@ static void security_dump_masked_av(struct context *scontext,
 static void type_attribute_bounds_av(struct context *scontext,
 				     struct context *tcontext,
 				     u16 tclass,
-				     u32 requested,
 				     struct av_decision *avd)
 {
 	struct context lo_scontext;
@@ -553,7 +534,6 @@ static void type_attribute_bounds_av(struct context *scontext,
 		context_struct_compute_av(&lo_scontext,
 					  tcontext,
 					  tclass,
-					  requested,
 					  &lo_avd);
 		if ((lo_avd.allowed & avd->allowed) == avd->allowed)
 			return;		/* no masked permission */
@@ -569,7 +549,6 @@ static void type_attribute_bounds_av(struct context *scontext,
 		context_struct_compute_av(scontext,
 					  &lo_tcontext,
 					  tclass,
-					  requested,
 					  &lo_avd);
 		if ((lo_avd.allowed & avd->allowed) == avd->allowed)
 			return;		/* no masked permission */
@@ -586,7 +565,6 @@ static void type_attribute_bounds_av(struct context *scontext,
 		context_struct_compute_av(&lo_scontext,
 					  &lo_tcontext,
 					  tclass,
-					  requested,
 					  &lo_avd);
 		if ((lo_avd.allowed & avd->allowed) == avd->allowed)
 			return;		/* no masked permission */
@@ -607,11 +585,10 @@ static void type_attribute_bounds_av(struct context *scontext,
  * Compute access vectors based on a context structure pair for
  * the permissions in a particular class.
  */
-static int context_struct_compute_av(struct context *scontext,
-				     struct context *tcontext,
-				     u16 tclass,
-				     u32 requested,
-				     struct av_decision *avd)
+static void context_struct_compute_av(struct context *scontext,
+				      struct context *tcontext,
+				      u16 tclass,
+				      struct av_decision *avd)
 {
 	struct constraint_node *constraint;
 	struct role_allow *ra;
@@ -622,19 +599,14 @@ static int context_struct_compute_av(struct context *scontext,
 	struct ebitmap_node *snode, *tnode;
 	unsigned int i, j;
 
-	/*
-	 * Initialize the access vectors to the default values.
-	 */
 	avd->allowed = 0;
 	avd->auditallow = 0;
 	avd->auditdeny = 0xffffffff;
-	avd->seqno = latest_granting;
-	avd->flags = 0;
 
 	if (unlikely(!tclass || tclass > policydb.p_classes.nprim)) {
 		if (printk_ratelimit())
 			printk(KERN_WARNING "SELinux:  Invalid class %hu\n", tclass);
-		return -EINVAL;
+		return;
 	}
 
 	tclass_datum = policydb.class_val_to_struct[tclass - 1];
@@ -705,9 +677,7 @@ static int context_struct_compute_av(struct context *scontext,
 	 * permission and notice it to userspace via audit.
 	 */
 	type_attribute_bounds_av(scontext, tcontext,
-				 tclass, requested, avd);
-
-	return 0;
+				 tclass, avd);
 }
 
 static int security_validtrans_handle_fail(struct context *ocontext,
@@ -886,110 +856,116 @@ int security_bounded_transition(u32 old_sid, u32 new_sid)
 	return rc;
 }
 
-
-static int security_compute_av_core(u32 ssid,
-				    u32 tsid,
-				    u16 tclass,
-				    u32 requested,
-				    struct av_decision *avd)
+static void avd_init(struct av_decision *avd)
 {
-	struct context *scontext = NULL, *tcontext = NULL;
-	int rc = 0;
-
-	scontext = sidtab_search(&sidtab, ssid);
-	if (!scontext) {
-		printk(KERN_ERR "SELinux: %s:  unrecognized SID %d\n",
-		       __func__, ssid);
-		return -EINVAL;
-	}
-	tcontext = sidtab_search(&sidtab, tsid);
-	if (!tcontext) {
-		printk(KERN_ERR "SELinux: %s:  unrecognized SID %d\n",
-		       __func__, tsid);
-		return -EINVAL;
-	}
-
-	rc = context_struct_compute_av(scontext, tcontext, tclass,
-				       requested, avd);
-
-	/* permissive domain? */
-	if (ebitmap_get_bit(&policydb.permissive_map, scontext->type))
-		avd->flags |= AVD_FLAGS_PERMISSIVE;
-
-	return rc;
+	avd->allowed = 0;
+	avd->auditallow = 0;
+	avd->auditdeny = 0xffffffff;
+	avd->seqno = latest_granting;
+	avd->flags = 0;
 }
 
+
 /**
  * security_compute_av - Compute access vector decisions.
  * @ssid: source security identifier
  * @tsid: target security identifier
  * @tclass: target security class
- * @requested: requested permissions
  * @avd: access vector decisions
  *
  * Compute a set of access vector decisions based on the
  * SID pair (@ssid, @tsid) for the permissions in @tclass.
- * Return -%EINVAL if any of the parameters are invalid or %0
- * if the access vector decisions were computed successfully.
  */
-int security_compute_av(u32 ssid,
-			u32 tsid,
-			u16 orig_tclass,
-			u32 orig_requested,
-			struct av_decision *avd)
+void security_compute_av(u32 ssid,
+			 u32 tsid,
+			 u16 orig_tclass,
+			 struct av_decision *avd)
 {
 	u16 tclass;
-	u32 requested;
-	int rc;
+	struct context *scontext = NULL, *tcontext = NULL;
 
 	read_lock(&policy_rwlock);
-
+	avd_init(avd);
 	if (!ss_initialized)
 		goto allow;
 
-	requested = unmap_perm(orig_tclass, orig_requested);
+	scontext = sidtab_search(&sidtab, ssid);
+	if (!scontext) {
+		printk(KERN_ERR "SELinux: %s:  unrecognized SID %d\n",
+		       __func__, ssid);
+		goto out;
+	}
+
+	/* permissive domain? */
+	if (ebitmap_get_bit(&policydb.permissive_map, scontext->type))
+		avd->flags |= AVD_FLAGS_PERMISSIVE;
+
+	tcontext = sidtab_search(&sidtab, tsid);
+	if (!tcontext) {
+		printk(KERN_ERR "SELinux: %s:  unrecognized SID %d\n",
+		       __func__, tsid);
+		goto out;
+	}
+
 	tclass = unmap_class(orig_tclass);
 	if (unlikely(orig_tclass && !tclass)) {
 		if (policydb.allow_unknown)
 			goto allow;
-		rc = -EINVAL;
 		goto out;
 	}
-	rc = security_compute_av_core(ssid, tsid, tclass, requested, avd);
+	context_struct_compute_av(scontext, tcontext, tclass, avd);
 	map_decision(orig_tclass, avd, policydb.allow_unknown);
 out:
 	read_unlock(&policy_rwlock);
-	return rc;
+	return;
 allow:
 	avd->allowed = 0xffffffff;
-	avd->auditallow = 0;
-	avd->auditdeny = 0xffffffff;
-	avd->seqno = latest_granting;
-	avd->flags = 0;
-	rc = 0;
 	goto out;
 }
 
-int security_compute_av_user(u32 ssid,
-			     u32 tsid,
-			     u16 tclass,
-			     u32 requested,
-			     struct av_decision *avd)
+void security_compute_av_user(u32 ssid,
+			      u32 tsid,
+			      u16 tclass,
+			      struct av_decision *avd)
 {
-	int rc;
+	struct context *scontext = NULL, *tcontext = NULL;
 
-	if (!ss_initialized) {
-		avd->allowed = 0xffffffff;
-		avd->auditallow = 0;
-		avd->auditdeny = 0xffffffff;
-		avd->seqno = latest_granting;
-		return 0;
+	read_lock(&policy_rwlock);
+	avd_init(avd);
+	if (!ss_initialized)
+		goto allow;
+
+	scontext = sidtab_search(&sidtab, ssid);
+	if (!scontext) {
+		printk(KERN_ERR "SELinux: %s:  unrecognized SID %d\n",
+		       __func__, ssid);
+		goto out;
 	}
 
-	read_lock(&policy_rwlock);
-	rc = security_compute_av_core(ssid, tsid, tclass, requested, avd);
+	/* permissive domain? */
+	if (ebitmap_get_bit(&policydb.permissive_map, scontext->type))
+		avd->flags |= AVD_FLAGS_PERMISSIVE;
+
+	tcontext = sidtab_search(&sidtab, tsid);
+	if (!tcontext) {
+		printk(KERN_ERR "SELinux: %s:  unrecognized SID %d\n",
+		       __func__, tsid);
+		goto out;
+	}
+
+	if (unlikely(!tclass)) {
+		if (policydb.allow_unknown)
+			goto allow;
+		goto out;
+	}
+
+	context_struct_compute_av(scontext, tcontext, tclass, avd);
+ out:
 	read_unlock(&policy_rwlock);
-	return rc;
+	return;
+allow:
+	avd->allowed = 0xffffffff;
+	goto out;
 }
 
 /*