| From c37119df45bbf4ef713bc10475af2ee06e12f3bf Mon Sep 17 00:00:00 2001 |
| From: Donatas Abraitis <donatas@opensourcerouting.org> |
| Date: Sun, 29 Oct 2023 22:44:45 +0200 |
| Subject: [PATCH] bgpd: Ignore handling NLRIs if we received MP_UNREACH_NLRI |
| |
| If we receive MP_UNREACH_NLRI, we should stop handling remaining NLRIs if |
| no mandatory path attributes received. |
| |
| In other words, if MP_UNREACH_NLRI received, the remaining NLRIs should be handled |
| as a new data, but without mandatory attributes, it's a malformed packet. |
| |
| In normal case, this MUST not happen at all, but to avoid crashing bgpd, we MUST |
| handle that. |
| |
| Reported-by: Iggy Frankovic <iggyfran@amazon.com> |
| Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org> |
| Upstream-Status: Backport [https://github.com/FRRouting/frr/commit/c37119df45bbf4ef713bc10475af2ee06e12f3bf] |
| CVE: CVE-2023-47234 |
| Signed-off-by: Jonas Gorski <jonas.gorski@bisdn.de> |
| --- |
| bgpd/bgp_attr.c | 19 ++++++++++--------- |
| bgpd/bgp_attr.h | 1 + |
| bgpd/bgp_packet.c | 7 ++++++- |
| 3 files changed, 17 insertions(+), 10 deletions(-) |
| |
| diff --git a/bgpd/bgp_attr.c b/bgpd/bgp_attr.c |
| index 1473dc772502..75aa2ac7cce6 100644 |
| --- a/bgpd/bgp_attr.c |
| +++ b/bgpd/bgp_attr.c |
| @@ -3399,15 +3399,6 @@ static int bgp_attr_check(struct peer *peer, struct attr *attr, |
| !length) |
| return BGP_ATTR_PARSE_WITHDRAW; |
| |
| - /* "An UPDATE message that contains the MP_UNREACH_NLRI is not required |
| - to carry any other path attributes.", though if MP_REACH_NLRI or NLRI |
| - are present, it should. Check for any other attribute being present |
| - instead. |
| - */ |
| - if ((!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_REACH_NLRI)) && |
| - CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_UNREACH_NLRI)))) |
| - return BGP_ATTR_PARSE_PROCEED; |
| - |
| if (!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_ORIGIN))) |
| type = BGP_ATTR_ORIGIN; |
| |
| @@ -3426,6 +3417,16 @@ static int bgp_attr_check(struct peer *peer, struct attr *attr, |
| && !CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_LOCAL_PREF))) |
| type = BGP_ATTR_LOCAL_PREF; |
| |
| + /* An UPDATE message that contains the MP_UNREACH_NLRI is not required |
| + * to carry any other path attributes. Though if MP_REACH_NLRI or NLRI |
| + * are present, it should. Check for any other attribute being present |
| + * instead. |
| + */ |
| + if (!CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_REACH_NLRI)) && |
| + CHECK_FLAG(attr->flag, ATTR_FLAG_BIT(BGP_ATTR_MP_UNREACH_NLRI))) |
| + return type ? BGP_ATTR_PARSE_MISSING_MANDATORY |
| + : BGP_ATTR_PARSE_PROCEED; |
| + |
| /* If any of the well-known mandatory attributes are not present |
| * in an UPDATE message, then "treat-as-withdraw" MUST be used. |
| */ |
| diff --git a/bgpd/bgp_attr.h b/bgpd/bgp_attr.h |
| index fc347e7a1b4b..d30155e6dba0 100644 |
| --- a/bgpd/bgp_attr.h |
| +++ b/bgpd/bgp_attr.h |
| @@ -364,6 +364,7 @@ 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_MISSING_MANDATORY = -4, |
| }; |
| |
| struct bpacket_attr_vec_arr; |
| diff --git a/bgpd/bgp_packet.c b/bgpd/bgp_packet.c |
| index a7514a26aa64..5dc35157ebf6 100644 |
| --- a/bgpd/bgp_packet.c |
| +++ b/bgpd/bgp_packet.c |
| @@ -2359,7 +2359,12 @@ static int bgp_update_receive(struct peer_connection *connection, |
| /* Network Layer Reachability Information. */ |
| update_len = end - stream_pnt(s); |
| |
| - if (update_len && attribute_len) { |
| + /* If we received MP_UNREACH_NLRI attribute, but also NLRIs, then |
| + * NLRIs should be handled as a new data. Though, if we received |
| + * NLRIs without mandatory attributes, they should be ignored. |
| + */ |
| + if (update_len && attribute_len && |
| + attr_parse_ret != BGP_ATTR_PARSE_MISSING_MANDATORY) { |
| /* Set NLRI portion to structure. */ |
| nlris[NLRI_UPDATE].afi = AFI_IP; |
| nlris[NLRI_UPDATE].safi = SAFI_UNICAST; |
| -- |
| 2.42.1 |
| |