From d19727b4ac595f17da530f5fa0bbd3bb16ea2aa1 Mon Sep 17 00:00:00 2001 From: Donatas Abraitis Date: Fri, 20 Oct 2023 17:49:18 +0300 Subject: [PATCH 1/2] bgpd: Handle MP_REACH_NLRI malformed packets with session reset Avoid crashing bgpd. ``` (gdb) bgp_mp_reach_parse (args=, mp_update=0x7fffffffe140) at bgpd/bgp_attr.c:2341 2341 stream_get(&attr->mp_nexthop_global, s, IPV6_MAX_BYTELEN); (gdb) stream_get (dst=0x7fffffffe1ac, s=0x7ffff0006e80, size=16) at lib/stream.c:320 320 { (gdb) 321 STREAM_VERIFY_SANE(s); (gdb) 323 if (STREAM_READABLE(s) < size) { (gdb) 34 return __builtin___memcpy_chk (__dest, __src, __len, __bos0 (__dest)); (gdb) Thread 1 "bgpd" received signal SIGSEGV, Segmentation fault. 0x00005555556e37be in route_set_aspath_prepend (rule=0x555555aac0d0, prefix=0x7fffffffe050, object=0x7fffffffdb00) at bgpd/bgp_routemap.c:2282 2282 if (path->attr->aspath->refcnt) (gdb) ``` With the configuration: ``` neighbor 127.0.0.1 remote-as external neighbor 127.0.0.1 passive neighbor 127.0.0.1 ebgp-multihop neighbor 127.0.0.1 disable-connected-check neighbor 127.0.0.1 update-source 127.0.0.2 neighbor 127.0.0.1 timers 3 90 neighbor 127.0.0.1 timers connect 1 address-family ipv4 unicast redistribute connected neighbor 127.0.0.1 default-originate neighbor 127.0.0.1 route-map RM_IN in exit-address-family ! route-map RM_IN permit 10 set as-path prepend 200 exit ``` Reported-by: Iggy Frankovic Signed-off-by: Donatas Abraitis (cherry picked from commit b08afc81c60607a4f736f418f2e3eb06087f1a35) --- bgpd/bgp_attr.c | 6 +----- bgpd/bgp_attr.h | 1 - bgpd/bgp_packet.c | 6 +----- 3 files changed, 2 insertions(+), 11 deletions(-) diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c index 60e41ac1cc83..bc519a48164f 100644 --- a/bgpd/bgp_attr.c +++ b/bgpd/bgp_attr.c @@ -2388,7 +2388,7 @@ int bgp_mp_reach_parse(struct bgp_attr_parser_args *args, mp_update->afi = afi; mp_update->safi = safi; - return BGP_ATTR_PARSE_EOR; + return bgp_attr_malformed(args, BGP_NOTIFY_UPDATE_MAL_ATTR, 0); } mp_update->afi = afi; @@ -3658,10 +3658,6 @@ enum bgp_attr_parse_ret bgp_attr_parse(struct peer *peer, struct attr *attr, goto done; } - if (ret == BGP_ATTR_PARSE_EOR) { - goto done; - } - if (ret == BGP_ATTR_PARSE_ERROR) { flog_warn(EC_BGP_ATTRIBUTE_PARSE_ERROR, "%s: Attribute %s, parse error", peer->host, diff --git a/bgpd/bgp_attr.h b/bgpd/bgp_attr.h index 1c7e88a4f9e2..3db0863d3b5a 100644 --- a/bgpd/bgp_attr.h +++ b/bgpd/bgp_attr.h @@ -364,7 +364,6 @@ enum bgp_attr_parse_ret { /* only used internally, send notify + convert to BGP_ATTR_PARSE_ERROR */ BGP_ATTR_PARSE_ERROR_NOTIFYPLS = -3, - BGP_ATTR_PARSE_EOR = -4, }; struct bpacket_attr_vec_arr; diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c index ec692277b26b..f88e1e5afcbb 100644 --- a/bgpd/bgp_packet.c +++ b/bgpd/bgp_packet.c @@ -2053,8 +2053,7 @@ static int bgp_update_receive(struct peer *peer, bgp_size_t size) * Non-MP IPv4/Unicast EoR is a completely empty UPDATE * and MP EoR should have only an empty MP_UNREACH */ - if ((!update_len && !withdraw_len && nlris[NLRI_MP_UPDATE].length == 0) - || (attr_parse_ret == BGP_ATTR_PARSE_EOR)) { + if (!update_len && !withdraw_len && nlris[NLRI_MP_UPDATE].length == 0) { afi_t afi = 0; safi_t safi; struct graceful_restart_info *gr_info; @@ -2075,9 +2074,6 @@ static int bgp_update_receive(struct peer *peer, bgp_size_t size) && nlris[NLRI_MP_WITHDRAW].length == 0) { afi = nlris[NLRI_MP_WITHDRAW].afi; safi = nlris[NLRI_MP_WITHDRAW].safi; - } else if (attr_parse_ret == BGP_ATTR_PARSE_EOR) { - afi = nlris[NLRI_MP_UPDATE].afi; - safi = nlris[NLRI_MP_UPDATE].safi; } if (afi && peer->afc[afi][safi]) { From 77e4046de0c602fcaad249909a99fbc037ac5c6b Mon Sep 17 00:00:00 2001 From: Donatas Abraitis Date: Mon, 23 Oct 2023 23:34:10 +0300 Subject: [PATCH 2/2] bgpd: Check mandatory attributes more carefully for UPDATE message If we send a crafted BGP UPDATE message without mandatory attributes, we do not check if the length of the path attributes is zero or not. We only check if attr->flag is at least set or not. Imagine we send only unknown transit attribute, then attr->flag is always 0. Also, this is true only if graceful-restart capability is received. A crash: ``` bgpd[7834]: [TJ23Y-GY0RH] 127.0.0.1 Unknown attribute is received (type 31, length 16) bgpd[7834]: [PCFFM-WMARW] 127.0.0.1(donatas-pc) rcvd UPDATE wlen 0 attrlen 20 alen 17 BGP[7834]: Received signal 11 at 1698089639 (si_addr 0x0, PC 0x55eefd375b4a); aborting... BGP[7834]: /usr/local/lib/libfrr.so.0(zlog_backtrace_sigsafe+0x6d) [0x7f3205ca939d] BGP[7834]: /usr/local/lib/libfrr.so.0(zlog_signal+0xf3) [0x7f3205ca9593] BGP[7834]: /usr/local/lib/libfrr.so.0(+0xf5181) [0x7f3205cdd181] BGP[7834]: /lib/x86_64-linux-gnu/libpthread.so.0(+0x12980) [0x7f3204ff3980] BGP[7834]: /usr/lib/frr/bgpd(+0x18ab4a) [0x55eefd375b4a] BGP[7834]: /usr/local/lib/libfrr.so.0(route_map_apply_ext+0x310) [0x7f3205cd1290] BGP[7834]: /usr/lib/frr/bgpd(+0x163610) [0x55eefd34e610] BGP[7834]: /usr/lib/frr/bgpd(bgp_update+0x9a5) [0x55eefd35c1d5] BGP[7834]: /usr/lib/frr/bgpd(bgp_nlri_parse_ip+0xb7) [0x55eefd35e867] BGP[7834]: /usr/lib/frr/bgpd(+0x1555e6) [0x55eefd3405e6] BGP[7834]: /usr/lib/frr/bgpd(bgp_process_packet+0x747) [0x55eefd345597] BGP[7834]: /usr/local/lib/libfrr.so.0(event_call+0x83) [0x7f3205cef4a3] BGP[7834]: /usr/local/lib/libfrr.so.0(frr_run+0xc0) [0x7f3205ca10a0] BGP[7834]: /usr/lib/frr/bgpd(main+0x409) [0x55eefd2dc979] ``` Sending: ``` import socket import time OPEN = (b"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" b"\xff\xff\x00\x62\x01\x04\xfd\xea\x00\x5a\x0a\x00\x00\x01\x45\x02" b"\x06\x01\x04\x00\x01\x00\x01\x02\x02\x02\x00\x02\x02\x46\x00\x02" b"\x06\x41\x04\x00\x00\xfd\xea\x02\x02\x06\x00\x02\x06\x45\x04\x00" b"\x01\x01\x03\x02\x0e\x49\x0c\x0a\x64\x6f\x6e\x61\x74\x61\x73\x2d" b"\x70\x63\x00\x02\x04\x40\x02\x00\x78\x02\x09\x47\x07\x00\x01\x01" b"\x80\x00\x00\x00") KEEPALIVE = (b"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" b"\xff\xff\xff\xff\xff\xff\x00\x13\x04") UPDATE = bytearray.fromhex("ffffffffffffffffffffffffffffffff003c0200000014ff1f001000040146464646460004464646464646664646f50d05800100010200ffff000000") s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect(('127.0.0.2', 179)) s.send(OPEN) data = s.recv(1024) s.send(KEEPALIVE) data = s.recv(1024) s.send(UPDATE) data = s.recv(1024) time.sleep(1000) s.close() ``` Reported-by: Iggy Frankovic Signed-off-by: Donatas Abraitis (cherry picked from commit d8482bf011cb2b173e85b65b4bf3d5061250cdb9) --- bgpd/bgp_attr.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c index bc519a48164f..7badc6a17cbf 100644 --- a/bgpd/bgp_attr.c +++ b/bgpd/bgp_attr.c @@ -3349,13 +3349,15 @@ bgp_attr_unknown(struct bgp_attr_parser_args *args) } /* Well-known attribute check. */ -static int bgp_attr_check(struct peer *peer, struct attr *attr) +static int bgp_attr_check(struct peer *peer, struct attr *attr, + bgp_size_t length) { uint8_t type = 0; /* BGP Graceful-Restart End-of-RIB for IPv4 unicast is signaled as an * empty UPDATE. */ - if (CHECK_FLAG(peer->cap, PEER_CAP_RESTART_RCV) && !attr->flag) + if (CHECK_FLAG(peer->cap, PEER_CAP_RESTART_RCV) && !attr->flag && + !length) return BGP_ATTR_PARSE_PROCEED; /* "An UPDATE message that contains the MP_UNREACH_NLRI is not required @@ -3407,7 +3409,7 @@ enum bgp_attr_parse_ret bgp_attr_parse(struct peer *peer, struct attr *attr, enum bgp_attr_parse_ret ret; uint8_t flag = 0; uint8_t type = 0; - bgp_size_t length; + bgp_size_t length = 0; uint8_t *startp, *endp; uint8_t *attr_endp; uint8_t seen[BGP_ATTR_BITMAP_SIZE]; @@ -3730,7 +3732,7 @@ enum bgp_attr_parse_ret bgp_attr_parse(struct peer *peer, struct attr *attr, } /* Check all mandatory well-known attributes are present */ - ret = bgp_attr_check(peer, attr); + ret = bgp_attr_check(peer, attr, length); if (ret < 0) goto done;