bgpd: Check capability falls on right multiple of size, where possible.

* bgp_open.c: (cap_modsizes) Table of multiple a capability's data size
  should fall on, if applicable.
  (bgp_capability_parse) Check the header lengthcap_modsizes should fall on.

  Inspiration from Cumulus bgpd-capability-cleanup.patch patch, with a
  slightly different approach.

Acked-by: Donald Sharp <sharpd@cumulusnetworks.com>
(cherry picked from commit 4078f2eb7a3a94ddb30cfd8b76b054e790aab524)

1 files changed, 30 insertions, 0 deletions

diff --git a/bgpd/bgp_open.c b/bgpd/bgp_open.c
index 06cf8a17b..8d2491b96 100644
--- a/bgpd/bgp_open.c
+++ b/bgpd/bgp_open.c
@@ -713,6 +713,23 @@ static const size_t cap_minsizes[] =
   [CAPABILITY_CODE_FQDN]        = CAPABILITY_CODE_MIN_FQDN_LEN,
 };
 
+/* value the capability must be a multiple of.
+ * 0-data capabilities won't be checked against this.
+ * Other capabilities whose data doesn't fall on convenient boundaries for this
+ * table should be set to 1.
+ */
+static const size_t cap_modsizes[] =
+{
+  [CAPABILITY_CODE_MP]          = 4,
+  [CAPABILITY_CODE_REFRESH]     = 1,
+  [CAPABILITY_CODE_ORF]         = 1,
+  [CAPABILITY_CODE_RESTART]     = 1,
+  [CAPABILITY_CODE_AS4]         = 4,
+  [CAPABILITY_CODE_DYNAMIC]     = 1,
+  [CAPABILITY_CODE_REFRESH_OLD] = 1,
+  [CAPABILITY_CODE_ORF_OLD]     = 1,
+};
+
 /**
  * Parse given capability.
  * XXX: This is reading into a stream, but not using stream API
@@ -790,6 +807,19 @@ bgp_capability_parse (struct peer *peer, size_t length, int *mp_capability,
                   bgp_notify_send (peer, BGP_NOTIFY_OPEN_ERR, BGP_NOTIFY_OPEN_MALFORMED_ATTR);
                   return -1;
                 }
+              if (caphdr.length
+                  && caphdr.length % cap_modsizes[caphdr.code] != 0)
+                {
+                  zlog_info ("%s %s Capability length error: got %u,"
+                             " expected a multiple of %u",
+                             peer->host,
+                             LOOKUP (capcode_str, caphdr.code),
+                             caphdr.length,
+			     (unsigned) cap_modsizes[caphdr.code]);
+                  bgp_notify_send (peer, BGP_NOTIFY_OPEN_ERR,
+                                         BGP_NOTIFY_OPEN_UNSPECIFIC);
+                  return -1;
+                }
           /* we deliberately ignore unknown codes, see below */
           default:
             break;