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111 lines
3.6 KiB
111 lines
3.6 KiB
From 71422bfe269e34b69d78f9fb02f30426f2fdef48 Mon Sep 17 00:00:00 2001
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From: rpm-build <rpm-build>
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Date: Wed, 13 Dec 2023 16:59:46 +0100
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Subject: [PATCH] bgpd: Treat EOR as withdrawn to avoid unwanted handling of
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malformed attrs
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Treat-as-withdraw, otherwise if we just ignore it, we will pass it to be
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processed as a normal UPDATE without mandatory attributes, that could lead
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to harmful behavior. In this case, a crash for route-maps with the configuration
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such as:
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```
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router bgp 65001
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no bgp ebgp-requires-policy
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neighbor 127.0.0.1 remote-as external
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neighbor 127.0.0.1 passive
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neighbor 127.0.0.1 ebgp-multihop
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neighbor 127.0.0.1 disable-connected-check
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neighbor 127.0.0.1 update-source 127.0.0.2
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neighbor 127.0.0.1 timers 3 90
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neighbor 127.0.0.1 timers connect 1
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!
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address-family ipv4 unicast
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neighbor 127.0.0.1 addpath-tx-all-paths
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neighbor 127.0.0.1 default-originate
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neighbor 127.0.0.1 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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Send a malformed optional transitive attribute:
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```
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import socket
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import time
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OPEN = (b"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
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b"\xff\xff\x00\x62\x01\x04\xfd\xea\x00\x5a\x0a\x00\x00\x01\x45\x02"
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b"\x06\x01\x04\x00\x01\x00\x01\x02\x02\x02\x00\x02\x02\x46\x00\x02"
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b"\x06\x41\x04\x00\x00\xfd\xea\x02\x02\x06\x00\x02\x06\x45\x04\x00"
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b"\x01\x01\x03\x02\x0e\x49\x0c\x0a\x64\x6f\x6e\x61\x74\x61\x73\x2d"
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b"\x70\x63\x00\x02\x04\x40\x02\x00\x78\x02\x09\x47\x07\x00\x01\x01"
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b"\x80\x00\x00\x00")
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KEEPALIVE = (b"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
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b"\xff\xff\xff\xff\xff\xff\x00\x13\x04")
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UPDATE = bytearray.fromhex("ffffffffffffffffffffffffffffffff002b0200000003c0ff00010100eb00ac100b0b001ad908ac100b0b")
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s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
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s.connect(('127.0.0.2', 179))
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s.send(OPEN)
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data = s.recv(1024)
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s.send(KEEPALIVE)
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data = s.recv(1024)
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s.send(UPDATE)
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data = s.recv(1024)
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time.sleep(100)
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s.close()
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```
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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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(cherry picked from commit 6814f2e0138a6ea5e1f83bdd9085d9a77999900b)
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---
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bgpd/bgp_attr.c | 15 ++++++++++++---
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1 file changed, 12 insertions(+), 3 deletions(-)
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diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c
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index a121911..12a6953 100644
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--- a/bgpd/bgp_attr.c
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+++ b/bgpd/bgp_attr.c
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@@ -3079,9 +3079,12 @@ static int bgp_attr_check(struct peer *peer, struct attr *attr)
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uint8_t type = 0;
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/* BGP Graceful-Restart End-of-RIB for IPv4 unicast is signaled as an
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- * empty UPDATE. */
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+ * empty UPDATE. Treat-as-withdraw, otherwise if we just ignore it,
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+ * we will pass it to be processed as a normal UPDATE without mandatory
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+ * attributes, that could lead to harmful behavior.
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+ */
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if (CHECK_FLAG(peer->cap, PEER_CAP_RESTART_RCV) && !attr->flag)
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- return BGP_ATTR_PARSE_PROCEED;
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+ return BGP_ATTR_PARSE_WITHDRAW;
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/* "An UPDATE message that contains the MP_UNREACH_NLRI is not required
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to carry any other path attributes.", though if MP_REACH_NLRI or NLRI
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@@ -3507,7 +3510,13 @@ done:
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aspath_unintern(&as4_path);
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transit = bgp_attr_get_transit(attr);
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- if (ret != BGP_ATTR_PARSE_ERROR) {
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+ /* If we received an UPDATE with mandatory attributes, then
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+ * the unrecognized transitive optional attribute of that
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+ * path MUST be passed. Otherwise, it's an error, and from
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+ * security perspective it might be very harmful if we continue
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+ * here with the unrecognized attributes.
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+ */
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+ if (ret == BGP_ATTR_PARSE_PROCEED) {
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/* Finally intern unknown attribute. */
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if (transit)
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bgp_attr_set_transit(attr, transit_intern(transit));
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--
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2.43.0
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