[bgpd] Bug #354: Take care to keep reads of MP_(UN)REACH_NLRI in bounds
2007-04-08 Paul Jakma <paul.jakma@sun.com>
* bgp_attr.c: (general) Bug #354: parsing of MP_REACH_NLRI and
MP_UNREACH_NLRI does not take sufficient care to ensure reads
from stream buffer stay in-bounds. Hence bgpd may attempt to read
beyond end of stream, if given a crafted packet. As it uses the
stream access methods to do so, this will typically result in
assert() being hit in stream.c. Where code is compiled without
assert() enabled, result is unknown.
(struct message attr_str) should be static.
(bgp_mp_reach_parse) Carefully check length remaining in stream
against amount desired to read from stream, prior to each read,
particularly where lengths are conditional on data obtained from
stream - using STREAM_READABLE.
Remove code to parse SNPA-number, it's a defunct field and changed
to a fixed size in latest BGP MP update RFC - log warning if
SNPA-number is not 0.
(bgp_mp_unreach_parse) Check withdraw_length carefully against
STREAM_READABLE.
(bgp_attr_parse) If attribute-parser function returns error, log
warning.
Log attribute type on mismatch.
diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
index 4c72d80..fc25d21 100644
--- a/bgpd/bgp_attr.c
+++ b/bgpd/bgp_attr.c
@@ -39,7 +39,7 @@
#include "bgpd/bgp_ecommunity.h"
/* Attribute strings for logging. */
-struct message attr_str [] =
+static struct message attr_str [] =
{
{ BGP_ATTR_ORIGIN, "ORIGIN" },
{ BGP_ATTR_AS_PATH, "AS_PATH" },
@@ -58,6 +58,7 @@
{ BGP_ATTR_MP_UNREACH_NLRI, "MP_UNREACH_NLRI" },
{ 0, NULL }
};
+int attr_str_max = sizeof(attr_str)/sizeof(attr_str[0]);
struct hash *cluster_hash;
@@ -934,24 +935,30 @@
{
u_int16_t afi;
u_char safi;
- u_char snpa_num;
- u_char snpa_len;
- u_char *lim;
bgp_size_t nlri_len;
+ size_t start;
int ret;
struct stream *s;
/* Set end of packet. */
- s = peer->ibuf;
- lim = stream_pnt (s) + length;
-
+ s = BGP_INPUT(peer);
+ start = stream_get_getp(s);
+
+ /* safe to read statically sized header? */
+#define BGP_MP_REACH_MIN_SIZE 5
+ if ((length > STREAM_READABLE(s)) || (length < BGP_MP_REACH_MIN_SIZE))
+ return -1;
+
/* Load AFI, SAFI. */
afi = stream_getw (s);
safi = stream_getc (s);
/* Get nexthop length. */
attr->mp_nexthop_len = stream_getc (s);
-
+
+ if (STREAM_READABLE(s) < attr->mp_nexthop_len)
+ return -1;
+
/* Nexthop length check. */
switch (attr->mp_nexthop_len)
{
@@ -997,15 +1004,20 @@
return -1;
}
- snpa_num = stream_getc (s);
-
- while (snpa_num--)
- {
- snpa_len = stream_getc (s);
- stream_forward_getp (s, (snpa_len + 1) >> 1);
- }
+ if (!STREAM_READABLE(s))
+ return -1;
- nlri_len = lim - stream_pnt (s);
+ {
+ u_char val;
+ if ((val = stream_getc (s)))
+ zlog_warn ("%s sent non-zero value, %u, for defunct SNPA-length field",
+ peer->host, val);
+ }
+
+ /* must have nrli_len, what is left of the attribute */
+ nlri_len = length - (stream_get_getp(s) - start);
+ if ((!nlri_len) || (nlri_len > STREAM_READABLE(s)))
+ return -1;
if (safi != BGP_SAFI_VPNV4)
{
@@ -1026,23 +1038,25 @@
/* Multiprotocol unreachable parse */
static int
-bgp_mp_unreach_parse (struct peer *peer, int length,
+bgp_mp_unreach_parse (struct peer *peer, bgp_size_t length,
struct bgp_nlri *mp_withdraw)
{
struct stream *s;
u_int16_t afi;
u_char safi;
- u_char *lim;
u_int16_t withdraw_len;
int ret;
s = peer->ibuf;
- lim = stream_pnt (s) + length;
-
+
+#define BGP_MP_UNREACH_MIN_SIZE 3
+ if ((length > STREAM_READABLE(s)) || (length < BGP_MP_UNREACH_MIN_SIZE))
+ return -1;
+
afi = stream_getw (s);
safi = stream_getc (s);
-
- withdraw_len = lim - stream_pnt (s);
+
+ withdraw_len = length - BGP_MP_UNREACH_MIN_SIZE;
if (safi != BGP_SAFI_VPNV4)
{
@@ -1278,13 +1292,23 @@
/* If error occured immediately return to the caller. */
if (ret < 0)
- return ret;
+ {
+ zlog (peer->log, LOG_WARNING,
+ "%s: Attribute %s, parse error",
+ peer->host,
+ LOOKUP (attr_str, type));
+ bgp_notify_send (peer,
+ BGP_NOTIFY_UPDATE_ERR,
+ BGP_NOTIFY_UPDATE_MAL_ATTR);
+ return ret;
+ }
/* Check the fetched length. */
if (BGP_INPUT_PNT (peer) != attr_endp)
{
zlog (peer->log, LOG_WARNING,
- "%s BGP attribute fetch error", peer->host);
+ "%s: BGP attribute %s, fetch error",
+ peer->host, LOOKUP (attr_str, type));
bgp_notify_send (peer,
BGP_NOTIFY_UPDATE_ERR,
BGP_NOTIFY_UPDATE_ATTR_LENG_ERR);
@@ -1296,7 +1320,8 @@
if (BGP_INPUT_PNT (peer) != endp)
{
zlog (peer->log, LOG_WARNING,
- "%s BGP attribute length mismatch", peer->host);
+ "%s BGP attribute %s, length mismatch",
+ peer->host, LOOKUP (attr_str, type));
bgp_notify_send (peer,
BGP_NOTIFY_UPDATE_ERR,
BGP_NOTIFY_UPDATE_ATTR_LENG_ERR);