101 lines
4.2 KiB
Diff
101 lines
4.2 KiB
Diff
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From e51ca641b4a96e575be069aeea922e31f7b8dfa4 Mon Sep 17 00:00:00 2001
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From: Donatas Abraitis <donatas@opensourcerouting.org>
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Date: Tue, 22 Aug 2023 22:52:04 +0300
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Upstream: yes
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References: CVE-2023-41358,bsc#1214735,https://github.com/FRRouting/frr/pull/14260
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Subject: [PATCH] bgpd: Do not process NLRIs if the attribute length is
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zero
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```
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3 0x00007f423aa42476 in __GI_raise (sig=sig@entry=11) at ../sysdeps/posix/raise.c:26
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4 0x00007f423aef9740 in core_handler (signo=11, siginfo=0x7fffc414deb0, context=<optimized out>) at lib/sigevent.c:246
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5 <signal handler called>
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6 0x0000564dea2fc71e in route_set_aspath_prepend (rule=0x564debd66d50, prefix=0x7fffc414ea30, object=0x7fffc414e400)
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at bgpd/bgp_routemap.c:2258
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7 0x00007f423aeec7e0 in route_map_apply_ext (map=<optimized out>, prefix=prefix@entry=0x7fffc414ea30,
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match_object=match_object@entry=0x7fffc414e400, set_object=set_object@entry=0x7fffc414e400, pref=pref@entry=0x0) at lib/routemap.c:2690
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8 0x0000564dea2d277e in bgp_input_modifier (peer=peer@entry=0x7f4238f59010, p=p@entry=0x7fffc414ea30, attr=attr@entry=0x7fffc414e770,
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afi=afi@entry=AFI_IP, safi=safi@entry=SAFI_UNICAST, rmap_name=rmap_name@entry=0x0, label=0x0, num_labels=0, dest=0x564debdd5130)
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at bgpd/bgp_route.c:1772
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9 0x0000564dea2df762 in bgp_update (peer=peer@entry=0x7f4238f59010, p=p@entry=0x7fffc414ea30, addpath_id=addpath_id@entry=0,
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attr=0x7fffc414eb50, afi=afi@entry=AFI_IP, safi=<optimized out>, safi@entry=SAFI_UNICAST, type=9, sub_type=0, prd=0x0, label=0x0,
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num_labels=0, soft_reconfig=0, evpn=0x0) at bgpd/bgp_route.c:4374
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10 0x0000564dea2e2047 in bgp_nlri_parse_ip (peer=0x7f4238f59010, attr=attr@entry=0x7fffc414eb50, packet=0x7fffc414eaf0)
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at bgpd/bgp_route.c:6249
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11 0x0000564dea2c5a58 in bgp_nlri_parse (peer=peer@entry=0x7f4238f59010, attr=attr@entry=0x7fffc414eb50,
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packet=packet@entry=0x7fffc414eaf0, mp_withdraw=mp_withdraw@entry=false) at bgpd/bgp_packet.c:339
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12 0x0000564dea2c5d66 in bgp_update_receive (peer=peer@entry=0x7f4238f59010, size=size@entry=109) at bgpd/bgp_packet.c:2024
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13 0x0000564dea2c901d in bgp_process_packet (thread=<optimized out>) at bgpd/bgp_packet.c:2933
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14 0x00007f423af0bf71 in event_call (thread=thread@entry=0x7fffc414ee40) at lib/event.c:1995
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15 0x00007f423aebb198 in frr_run (master=0x564deb73c670) at lib/libfrr.c:1213
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16 0x0000564dea261b83 in main (argc=<optimized out>, argv=<optimized out>) at bgpd/bgp_main.c:505
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```
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With the configuration:
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```
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frr version 9.1-dev-MyOwnFRRVersion
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frr defaults traditional
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hostname ip-172-31-13-140
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log file /tmp/debug.log
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log syslog
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service integrated-vtysh-config
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!
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debug bgp keepalives
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debug bgp neighbor-events
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debug bgp updates in
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debug bgp updates out
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!
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router bgp 100
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bgp router-id 9.9.9.9
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no bgp ebgp-requires-policy
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bgp bestpath aigp
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neighbor 172.31.2.47 remote-as 200
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!
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address-family ipv4 unicast
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neighbor 172.31.2.47 default-originate
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neighbor 172.31.2.47 route-map RM_IN in
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exit-address-family
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exit
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!
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route-map RM_IN permit 10
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set as-path prepend 200
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exit
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!
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```
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The issue is that we try to process NLRIs even if the attribute length is 0.
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Later bgp_update() will handle route-maps and a crash occurs because all the
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attributes are NULL, including aspath, where we dereference.
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According to the RFC 4271:
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A value of 0 indicates that neither the Network Layer
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Reachability Information field nor the Path Attribute field is
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present in this UPDATE message.
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But with a fuzzed UPDATE message this can be faked. I think it's reasonable
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to skip processing NLRIs if both update_len and attribute_len are 0.
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Reported-by: Iggy Frankovic <iggyfran@amazon.com>
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Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>
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Signed-off-by: Marius Tomaschewski <mt@suse.com>
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diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c
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index 4947dbc21d..1ef421028f 100644
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--- a/bgpd/bgp_packet.c
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+++ b/bgpd/bgp_packet.c
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@@ -1951,7 +1951,7 @@ static int bgp_update_receive(struct peer *peer, bgp_size_t size)
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/* Network Layer Reachability Information. */
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update_len = end - stream_pnt(s);
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- if (update_len) {
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+ if (update_len && attribute_len) {
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/* Set NLRI portion to structure. */
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nlris[NLRI_UPDATE].afi = AFI_IP;
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nlris[NLRI_UPDATE].safi = SAFI_UNICAST;
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--
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2.35.3
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