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From ef9b66e742f9016b3bf283920b528cf20d2c969f Mon Sep 17 00:00:00 2001
From: Donatas Abraitis <donatas@opensourcerouting.org>
Date: Tue, 5 Sep 2023 11:36:13 +0000
Subject: [PATCH 2/2] bgpd: Do not process NLRIs if the attribute length is
zero
```
3 0x00007f423aa42476 in __GI_raise (sig=sig@entry=11) at ../sysdeps/posix/raise.c:26
4 0x00007f423aef9740 in core_handler (signo=11, siginfo=0x7fffc414deb0, context=<optimized out>) at lib/sigevent.c:246
5 <signal handler called>
6 0x0000564dea2fc71e in route_set_aspath_prepend (rule=0x564debd66d50, prefix=0x7fffc414ea30, object=0x7fffc414e400)
at bgpd/bgp_routemap.c:2258
7 0x00007f423aeec7e0 in route_map_apply_ext (map=<optimized out>, prefix=prefix@entry=0x7fffc414ea30,
match_object=match_object@entry=0x7fffc414e400, set_object=set_object@entry=0x7fffc414e400, pref=pref@entry=0x0) at lib/routemap.c:2690
8 0x0000564dea2d277e in bgp_input_modifier (peer=peer@entry=0x7f4238f59010, p=p@entry=0x7fffc414ea30, attr=attr@entry=0x7fffc414e770,
afi=afi@entry=AFI_IP, safi=safi@entry=SAFI_UNICAST, rmap_name=rmap_name@entry=0x0, label=0x0, num_labels=0, dest=0x564debdd5130)
at bgpd/bgp_route.c:1772
9 0x0000564dea2df762 in bgp_update (peer=peer@entry=0x7f4238f59010, p=p@entry=0x7fffc414ea30, addpath_id=addpath_id@entry=0,
attr=0x7fffc414eb50, afi=afi@entry=AFI_IP, safi=<optimized out>, safi@entry=SAFI_UNICAST, type=9, sub_type=0, prd=0x0, label=0x0,
num_labels=0, soft_reconfig=0, evpn=0x0) at bgpd/bgp_route.c:4374
10 0x0000564dea2e2047 in bgp_nlri_parse_ip (peer=0x7f4238f59010, attr=attr@entry=0x7fffc414eb50, packet=0x7fffc414eaf0)
at bgpd/bgp_route.c:6249
11 0x0000564dea2c5a58 in bgp_nlri_parse (peer=peer@entry=0x7f4238f59010, attr=attr@entry=0x7fffc414eb50,
packet=packet@entry=0x7fffc414eaf0, mp_withdraw=mp_withdraw@entry=false) at bgpd/bgp_packet.c:339
12 0x0000564dea2c5d66 in bgp_update_receive (peer=peer@entry=0x7f4238f59010, size=size@entry=109) at bgpd/bgp_packet.c:2024
13 0x0000564dea2c901d in bgp_process_packet (thread=<optimized out>) at bgpd/bgp_packet.c:2933
14 0x00007f423af0bf71 in event_call (thread=thread@entry=0x7fffc414ee40) at lib/event.c:1995
15 0x00007f423aebb198 in frr_run (master=0x564deb73c670) at lib/libfrr.c:1213
16 0x0000564dea261b83 in main (argc=<optimized out>, argv=<optimized out>) at bgpd/bgp_main.c:505
```
With the configuration:
```
frr version 9.1-dev-MyOwnFRRVersion
frr defaults traditional
hostname ip-172-31-13-140
log file /tmp/debug.log
log syslog
service integrated-vtysh-config
!
debug bgp keepalives
debug bgp neighbor-events
debug bgp updates in
debug bgp updates out
!
router bgp 100
bgp router-id 9.9.9.9
no bgp ebgp-requires-policy
bgp bestpath aigp
neighbor 172.31.2.47 remote-as 200
!
address-family ipv4 unicast
neighbor 172.31.2.47 default-originate
neighbor 172.31.2.47 route-map RM_IN in
exit-address-family
exit
!
route-map RM_IN permit 10
set as-path prepend 200
exit
!
```
The issue is that we try to process NLRIs even if the attribute length is 0.
Later bgp_update() will handle route-maps and a crash occurs because all the
attributes are NULL, including aspath, where we dereference.
According to the RFC 4271:
A value of 0 indicates that neither the Network Layer
Reachability Information field nor the Path Attribute field is
present in this UPDATE message.
But with a fuzzed UPDATE message this can be faked. I think it's reasonable
to skip processing NLRIs if both update_len and attribute_len are 0.
Reported-by: Iggy Frankovic <iggyfran@amazon.com>
Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>
CVE: CVE-2023-41358
Upstream-Status: Backport [https://github.com/FRRouting/frr/pull/14260/commits/28ccc24d38df1d51ed8a563507e5d6f6171fdd38]
Signed-off-by: Narpat Mali <narpat.mali@windriver.com>
---
bgpd/bgp_packet.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
index 0166dc6a2..2fd28aae3 100644
--- a/bgpd/bgp_packet.c
+++ b/bgpd/bgp_packet.c
@@ -1767,7 +1767,7 @@ static int bgp_update_receive(struct peer *peer, bgp_size_t size)
/* Network Layer Reachability Information. */
update_len = end - stream_pnt(s);
- if (update_len) {
+ if (update_len && attribute_len) {
/* Set NLRI portion to structure. */
nlris[NLRI_UPDATE].afi = AFI_IP;
nlris[NLRI_UPDATE].safi = SAFI_UNICAST;
--
2.40.0
|
