From d8482bf011cb2b173e85b65b4bf3d5061250cdb9 Mon Sep 17 00:00:00 2001 From: Donatas Abraitis 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. Reported-by: Iggy Frankovic Signed-off-by: Donatas Abraitis --- 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 26fd3de..bcc4424 100644 --- a/bgpd/bgp_attr.c +++ b/bgpd/bgp_attr.c @@ -3400,7 +3400,8 @@ 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; @@ -3409,7 +3410,8 @@ static int bgp_attr_check(struct peer *peer, struct attr *attr) * we will pass it to be processed as a normal UPDATE without mandatory * attributes, that could lead to harmful behavior. */ - 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_WITHDRAW; if (!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_ORIGIN))) @@ -3462,7 +3464,7 @@ enum bgp_attr_parse_ret bgp_attr_parse(struct peer *peer, struct attr *attr, bgp_attr_parse_ret_t 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]; @@ -3216,7 +3218,7 @@ bgp_attr_parse_ret_t bgp_attr_parse(struct peer *peer, struct attr *attr, } /* Check all mandatory well-known attributes are present */ - if ((ret = bgp_attr_check(peer, attr)) < 0) + if ((ret = bgp_attr_check(peer, attr, length)) < 0) goto done; /*