bridge: multicast: add sanity check for query source addresses
Subsystems (3)
PATCH 1/1 bridge: multicast: add sanity check for query source addresses
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.
--- net/bridge/br_multicast.c | 6 ++++++ 1 file changed, 6 insertions(+)
net/bridge/br_multicast.c +6 -0
@@ -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 ;
Signature · 1 line
1.7.10.4
Quoted 23 lines · Linus Lüssing
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 <[email protected]>Signed-off-by Linus Lüssing <[email protected]>--- net/bridge/br_multicast.c | 6 ++++++ 1 file changed, 6 insertions(+)net/bridge/br_multicast.c +0
-0
net/bridge/br_multicast.c static int br_ip6_multicast_query(struct net_bridge *br, · line 1243
Quoted 9 lines
net/bridge/br_multicast.c +6
-0@@ -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; + } +
Shouldn't we allow empty source address, here?
Routers are supposed to drop them but bridges care. Linux uses ::
as source address as long as no valid LL addresses are available, e.g. at boot-up (RFC3810 5.2.13.).
Greetings,
Hannes
Quoted 17 lines · Hannes Frederic Sowa
Quoted 5 lines
net/bridge/br_multicast.c +0
-0net/bridge/br_multicast.c static int br_ip6_multicast_query(struct net_bridge *br, · line 1243
Quoted 9 lines
net/bridge/br_multicast.c +6
-0@@ -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; + } +Shouldn't we allow empty source address, here?
Quoted 3 lines
Routers are supposed to drop them but bridges care. Linux uses ::
as source address as long as no valid LL addresses are available, e.g. at boot-up (RFC3810 5.2.13.).
RFC3810, 5.2.13. refers to MLD reports, not queries, so that shouldn't be relevant, section 5.1.14 should apply. Also the bridge code only issues queries with a valid link-local source address (see br_ip6_multicast_alloc_query() in net/bridge/br_multicast.c). Where does Linux use :: for queries?
Cheers, Linus
Hannes Frederic Sowa
Reviewed-byQuoted 22 lines · Linus Lüssing
Quoted 17 lines · Hannes Frederic Sowa
Quoted 5 lines
net/bridge/br_multicast.c +0
-0net/bridge/br_multicast.c static int br_ip6_multicast_query(struct net_bridge *br, · line 1243
Quoted 9 lines
net/bridge/br_multicast.c +6
-0@@ -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; + } +Shouldn't we allow empty source address, here?
Quoted 3 lines
Routers are supposed to drop them but bridges care. Linux uses ::
as source address as long as no valid LL addresses are available, e.g. at boot-up (RFC3810 5.2.13.).
Quoted 5 lines
RFC3810, 5.2.13. refers to MLD reports, not queries, so that shouldn't be relevant, section 5.1.14 should apply. Also the bridge code only issues queries with a valid link-local source address (see
br_ip6_multicast_alloc_query()innet/bridge/br_multicast.c). Where does Linux use :: for queries?
Sorry, I confused queries with reports.
Your patch looks good, same check as in igmp6_event_query.
Bye,
Hannes
From: Linus Lüssing <[email protected]>
Date: Tue, 4 Mar 2014 03:57:35 +0100
Quoted 12 lines
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.
Quoted 2 lines
Reported-by Jan Stancek <[email protected]>Signed-off-by Linus Lüssing <[email protected]>
Applied.