SELinux: Better integration between peer labeling subsystems

Rework the handling of network peer labels so that the different peer labeling
subsystems work better together.  This includes moving both subsystems to a
single "peer" object class which involves not only changes to the permission
checks but an improved method of consolidating multiple packet peer labels.
As part of this work the inbound packet permission check code has been heavily
modified to handle both the old and new behavior in as sane a fashion as
possible.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 85 insertions, 0 deletions

diff --git a/security/selinux/ss/services.c b/security/selinux/ss/services.c
index 8ee04a424df7..7f0ee1b91e1d 100644
--- a/security/selinux/ss/services.c
+++ b/security/selinux/ss/services.c
@@ -2054,6 +2054,91 @@ out:
         return rc;
 }
 
+/**
+ * security_net_peersid_resolve - Compare and resolve two network peer SIDs
+ * @nlbl_sid: NetLabel SID
+ * @nlbl_type: NetLabel labeling protocol type
+ * @xfrm_sid: XFRM SID
+ *
+ * Description:
+ * Compare the @nlbl_sid and @xfrm_sid values and if the two SIDs can be
+ * resolved into a single SID it is returned via @peer_sid and the function
+ * returns zero.  Otherwise @peer_sid is set to SECSID_NULL and the function
+ * returns a negative value.  A table summarizing the behavior is below:
+ *
+ *                                 | function return |      @sid
+ *   ------------------------------+-----------------+-----------------
+ *   no peer labels                |        0        |    SECSID_NULL
+ *   single peer label             |        0        |    <peer_label>
+ *   multiple, consistent labels   |        0        |    <peer_label>
+ *   multiple, inconsistent labels |    -<errno>     |    SECSID_NULL
+ *
+ */
+int security_net_peersid_resolve(u32 nlbl_sid, u32 nlbl_type,
+                                 u32 xfrm_sid,
+                                 u32 *peer_sid)
+{
+        int rc;
+        struct context *nlbl_ctx;
+        struct context *xfrm_ctx;
+
+        /* handle the common (which also happens to be the set of easy) cases
+         * right away, these two if statements catch everything involving a
+         * single or absent peer SID/label */
+        if (xfrm_sid == SECSID_NULL) {
+                *peer_sid = nlbl_sid;
+                return 0;
+        }
+        /* NOTE: an nlbl_type == NETLBL_NLTYPE_UNLABELED is a "fallback" label
+         * and is treated as if nlbl_sid == SECSID_NULL when a XFRM SID/label
+         * is present */
+        if (nlbl_sid == SECSID_NULL || nlbl_type == NETLBL_NLTYPE_UNLABELED) {
+                *peer_sid = xfrm_sid;
+                return 0;
+        }
+
+        /* we don't need to check ss_initialized here since the only way both
+         * nlbl_sid and xfrm_sid are not equal to SECSID_NULL would be if the
+         * security server was initialized and ss_initialized was true */
+        if (!selinux_mls_enabled) {
+                *peer_sid = SECSID_NULL;
+                return 0;
+        }
+
+        POLICY_RDLOCK;
+
+        nlbl_ctx = sidtab_search(&sidtab, nlbl_sid);
+        if (!nlbl_ctx) {
+                printk(KERN_ERR
+                       "security_sid_mls_cmp:  unrecognized SID %d\n",
+                       nlbl_sid);
+                rc = -EINVAL;
+                goto out_slowpath;
+        }
+        xfrm_ctx = sidtab_search(&sidtab, xfrm_sid);
+        if (!xfrm_ctx) {
+                printk(KERN_ERR
+                       "security_sid_mls_cmp:  unrecognized SID %d\n",
+                       xfrm_sid);
+                rc = -EINVAL;
+                goto out_slowpath;
+        }
+        rc = (mls_context_cmp(nlbl_ctx, xfrm_ctx) ? 0 : -EACCES);
+
+out_slowpath:
+        POLICY_RDUNLOCK;
+        if (rc == 0)
+                /* at present NetLabel SIDs/labels really only carry MLS
+                 * information so if the MLS portion of the NetLabel SID
+                 * matches the MLS portion of the labeled XFRM SID/label
+                 * then pass along the XFRM SID as it is the most
+                 * expressive */
+                *peer_sid = xfrm_sid;
+        else
+                *peer_sid = SECSID_NULL;
+        return rc;
+}
+
 static int get_classes_callback(void *k, void *d, void *args)
 {
         struct class_datum *datum = d;