From 6565b9eeef194afbb3beec80d6dd2447f4091f8c Mon Sep 17 00:00:00 2001 From: Linus Lüssing Date: Tue, 4 Mar 2014 03:57:35 +0100 Subject: bridge: multicast: add sanity check for query source addresses MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MLD queries are supposed to have an IPv6 link-local source address according to RFC2710, section 4 and RFC3810, section 5.1.14. This patch adds a sanity check to ignore such broken MLD queries. Without this check, such malformed MLD queries can result in a denial of service: The queries are ignored by any MLD listener therefore they will not respond with an MLD report. However, without this patch these malformed MLD queries would enable the snooping part in the bridge code, potentially shutting down the according ports towards these hosts for multicast traffic as the bridge did not learn about these listeners. Reported-by: Jan Stancek Signed-off-by: Linus Lüssing Reviewed-by: Hannes Frederic Sowa Signed-off-by: David S. Miller --- net/bridge/br_multicast.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'net/bridge') diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index ef66365b735..fb0e36fac66 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -1235,6 +1235,12 @@ static int br_ip6_multicast_query(struct net_bridge *br, (port && port->state == BR_STATE_DISABLED)) goto out; + /* RFC2710+RFC3810 (MLDv1+MLDv2) require link-local source addresses */ + if (!(ipv6_addr_type(&ip6h->saddr) & IPV6_ADDR_LINKLOCAL)) { + err = -EINVAL; + goto out; + } + if (skb->len == sizeof(*mld)) { if (!pskb_may_pull(skb, sizeof(*mld))) { err = -EINVAL; -- cgit v1.2.3-18-g5258 From 9ed973cc40c588abeaa58aea0683ea665132d11d Mon Sep 17 00:00:00 2001 From: Linus Lüssing Date: Mon, 10 Mar 2014 22:25:24 +0100 Subject: bridge: multicast: add sanity check for general query destination MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit General IGMP and MLD queries are supposed to have the multicast link-local all-nodes address as their destination according to RFC2236 section 9, RFC3376 section 4.1.12/9.1, RFC2710 section 8 and RFC3810 section 5.1.15. Without this check, such malformed IGMP/MLD queries can result in a denial of service: The queries are ignored by most IGMP/MLD listeners therefore they will not respond with an IGMP/MLD report. However, without this patch these malformed MLD queries would enable the snooping part in the bridge code, potentially shutting down the according ports towards these hosts for multicast traffic as the bridge did not learn about these listeners. Reported-by: Jan Stancek Signed-off-by: Linus Lüssing Signed-off-by: David S. Miller --- net/bridge/br_multicast.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'net/bridge') diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index fb0e36fac66..e56bae4f59c 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -1181,6 +1181,14 @@ static int br_ip4_multicast_query(struct net_bridge *br, IGMPV3_MRC(ih3->code) * (HZ / IGMP_TIMER_SCALE) : 1; } + /* RFC2236+RFC3376 (IGMPv2+IGMPv3) require the multicast link layer + * all-systems destination addresses (224.0.0.1) for general queries + */ + if (!group && iph->daddr != htonl(INADDR_ALLHOSTS_GROUP)) { + err = -EINVAL; + goto out; + } + br_multicast_query_received(br, port, &br->ip4_querier, !!iph->saddr, max_delay); @@ -1228,6 +1236,7 @@ static int br_ip6_multicast_query(struct net_bridge *br, unsigned long max_delay; unsigned long now = jiffies; const struct in6_addr *group = NULL; + bool is_general_query; int err = 0; spin_lock(&br->multicast_lock); @@ -1262,6 +1271,16 @@ static int br_ip6_multicast_query(struct net_bridge *br, max_delay = max(msecs_to_jiffies(mldv2_mrc(mld2q)), 1UL); } + is_general_query = group && ipv6_addr_any(group); + + /* RFC2710+RFC3810 (MLDv1+MLDv2) require the multicast link layer + * all-nodes destination address (ff02::1) for general queries + */ + if (is_general_query && !ipv6_addr_is_ll_all_nodes(&ip6h->daddr)) { + err = -EINVAL; + goto out; + } + br_multicast_query_received(br, port, &br->ip6_querier, !ipv6_addr_any(&ip6h->saddr), max_delay); -- cgit v1.2.3-18-g5258 From 20a599bec95a52fa72432b2376a2ce47c5bb68fb Mon Sep 17 00:00:00 2001 From: Linus Lüssing Date: Mon, 10 Mar 2014 22:25:25 +0100 Subject: bridge: multicast: enable snooping on general queries only MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Without this check someone could easily create a denial of service by injecting multicast-specific queries to enable the bridge snooping part if no real querier issuing periodic general queries is present on the link which would result in the bridge wrongly shutting down ports for multicast traffic as the bridge did not learn about these listeners. With this patch the snooping code is enabled upon receiving valid, general queries only. Signed-off-by: Linus Lüssing Signed-off-by: David S. Miller --- net/bridge/br_multicast.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'net/bridge') diff --git a/net/bridge/br_multicast.c b/net/bridge/br_multicast.c index e56bae4f59c..93067ecdb9a 100644 --- a/net/bridge/br_multicast.c +++ b/net/bridge/br_multicast.c @@ -1127,9 +1127,10 @@ static void br_multicast_query_received(struct net_bridge *br, struct net_bridge_port *port, struct bridge_mcast_querier *querier, int saddr, + bool is_general_query, unsigned long max_delay) { - if (saddr) + if (saddr && is_general_query) br_multicast_update_querier_timer(br, querier, max_delay); else if (timer_pending(&querier->timer)) return; @@ -1190,7 +1191,7 @@ static int br_ip4_multicast_query(struct net_bridge *br, } br_multicast_query_received(br, port, &br->ip4_querier, !!iph->saddr, - max_delay); + !group, max_delay); if (!group) goto out; @@ -1282,7 +1283,8 @@ static int br_ip6_multicast_query(struct net_bridge *br, } br_multicast_query_received(br, port, &br->ip6_querier, - !ipv6_addr_any(&ip6h->saddr), max_delay); + !ipv6_addr_any(&ip6h->saddr), + is_general_query, max_delay); if (!group) goto out; -- cgit v1.2.3-18-g5258