This patch may be removed once Quagga is updated to 0.99.22.2 or
later.


From c51443f4aa6b7f0b0d6ad5409ad7d4b215092443 Mon Sep 17 00:00:00 2001
From: David Lamparter <[email protected]>
Date: Mon, 8 Jul 2013 23:05:28 +0200
Subject: [PATCH] ospfd: CVE-2013-2236, stack overrun in apiserver

the OSPF API-server (exporting the LSDB and allowing announcement of
Opaque-LSAs) writes past the end of fixed on-stack buffers.  This leads
to an exploitable stack overflow.

For this condition to occur, the following two conditions must be true:
- Quagga is configured with --enable-opaque-lsa
- ospfd is started with the "-a" command line option

If either of these does not hold, the relevant code is not executed and
the issue does not get triggered.

Since the issue occurs on receiving large LSAs (larger than 1488 bytes),
it is possible for this to happen during normal operation of a network.
In particular, if there is an OSPF router with a large number of
interfaces, the Router-LSA of that router may exceed 1488 bytes and
trigger this, leading to an ospfd crash.

For an attacker to exploit this, s/he must be able to inject valid LSAs
into the OSPF domain.  Any best-practice protection measure (using
crypto authentication, restricting OSPF to internal interfaces, packet
filtering protocol 89, etc.) will prevent exploitation.  On top of that,
remote (not on an OSPF-speaking network segment) attackers will have
difficulties bringing up the adjacency needed to inject a LSA.

This patch only performs minimal changes to remove the possibility of a
stack overrun.  The OSPF API in general is quite ugly and needs a
rewrite.

Reported-by: Ricky Charlet <[email protected]>
Cc: Florian Weimer <[email protected]>
Signed-off-by: David Lamparter <[email protected]>
---
 ospfd/ospf_api.c |   25 ++++++++++++++++++-------
 1 files changed, 19 insertions(+), 7 deletions(-)

--- ospfd/ospf_api.c
+++ ospfd/ospf_api.c
@@ -21,6 +21,7 @@
  */
 
 #include <zebra.h>
+#include <stddef.h>
 
 #ifdef SUPPORT_OSPF_API
 #ifndef HAVE_OPAQUE_LSA
@@ -472,6 +473,9 @@ new_msg_register_event (u_int32_t seqnum
   emsg->filter.typemask = htons (filter->typemask);
   emsg->filter.origin = filter->origin;
   emsg->filter.num_areas = filter->num_areas;
+  if (len > sizeof (buf))
+    len = sizeof(buf);
+  /* API broken - missing memcpy to fill data */
   return msg_new (MSG_REGISTER_EVENT, emsg, seqnum, len);
 }
 
@@ -488,6 +492,9 @@ new_msg_sync_lsdb (u_int32_t seqnum, str
   smsg->filter.typemask = htons (filter->typemask);
   smsg->filter.origin = filter->origin;
   smsg->filter.num_areas = filter->num_areas;
+  if (len > sizeof (buf))
+    len = sizeof(buf);
+  /* API broken - missing memcpy to fill data */
   return msg_new (MSG_SYNC_LSDB, smsg, seqnum, len);
 }
 
@@ -501,13 +508,15 @@ new_msg_originate_request (u_int32_t seq
   int omsglen;
   char buf[OSPF_API_MAX_MSG_SIZE];
 
-  omsglen = sizeof (struct msg_originate_request) - sizeof (struct lsa_header)
-    + ntohs (data->length);
-
   omsg = (struct msg_originate_request *) buf;
   omsg->ifaddr = ifaddr;
   omsg->area_id = area_id;
-  memcpy (&omsg->data, data, ntohs (data->length));
+
+  omsglen = ntohs (data->length);
+  if (omsglen > sizeof (buf) - offsetof (struct msg_originate_request, data))
+    omsglen = sizeof (buf) - offsetof (struct msg_originate_request, data);
+  memcpy (&omsg->data, data, omsglen);
+  omsglen += sizeof (struct msg_originate_request) - sizeof (struct lsa_header);
 
   return msg_new (MSG_ORIGINATE_REQUEST, omsg, seqnum, omsglen);
 }
@@ -627,13 +636,16 @@ new_msg_lsa_change_notify (u_char msgtyp
   assert (data);
 
   nmsg = (struct msg_lsa_change_notify *) buf;
-  len = ntohs (data->length) + sizeof (struct msg_lsa_change_notify)
-    - sizeof (struct lsa_header);
   nmsg->ifaddr = ifaddr;
   nmsg->area_id = area_id;
   nmsg->is_self_originated = is_self_originated;
   memset (&nmsg->pad, 0, sizeof (nmsg->pad));
-  memcpy (&nmsg->data, data, ntohs (data->length));
+
+  len = ntohs (data->length);
+  if (len > sizeof (buf) - offsetof (struct msg_lsa_change_notify, data))
+    len = sizeof (buf) - offsetof (struct msg_lsa_change_notify, data);
+  memcpy (&nmsg->data, data, len);
+  len += sizeof (struct msg_lsa_change_notify) - sizeof (struct lsa_header);
 
   return msg_new (msgtype, nmsg, seqnum, len);
 }