ipv6: add option to drop unicast encapsulated in L2 multicast
In order to solve a problem with 802.11, the so-called hole-196 attack,
add an option (sysctl) called "drop_unicast_in_l2_multicast" which, if
enabled, causes the stack to drop IPv6 unicast packets encapsulated in
link-layer multi- or broadcast frames. Such frames can (as an attack)
be created by any member of the same wireless network and transmitted
as valid encrypted frames since the symmetric key for broadcast frames
is shared between all stations.
Reviewed-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index a53bbfa..e0e7350 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1674,6 +1674,12 @@
By default the stable secret is unset.
+drop_unicast_in_l2_multicast - BOOLEAN
+ Drop any unicast IPv6 packets that are received in link-layer
+ multicast (or broadcast) frames.
+
+ By default this is turned off.
+
icmp/*:
ratelimit - INTEGER
Limit the maximal rates for sending ICMPv6 packets.
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 402753b..4a4c1ae 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -50,6 +50,7 @@
__s32 mc_forwarding;
#endif
__s32 disable_ipv6;
+ __s32 drop_unicast_in_l2_multicast;
__s32 accept_dad;
__s32 force_tllao;
__s32 ndisc_notify;
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 38b4fef..4c41357 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -174,6 +174,7 @@
DEVCONF_USE_OIF_ADDRS_ONLY,
DEVCONF_ACCEPT_RA_MIN_HOP_LIMIT,
DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN,
+ DEVCONF_DROP_UNICAST_IN_L2_MULTICAST,
DEVCONF_MAX
};
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 38eedde..23e325f 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4711,6 +4711,7 @@
array[DEVCONF_IGNORE_ROUTES_WITH_LINKDOWN] = cnf->ignore_routes_with_linkdown;
/* we omit DEVCONF_STABLE_SECRET for now */
array[DEVCONF_USE_OIF_ADDRS_ONLY] = cnf->use_oif_addrs_only;
+ array[DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] = cnf->drop_unicast_in_l2_multicast;
}
static inline size_t inet6_ifla6_size(void)
@@ -5785,6 +5786,13 @@
.proc_handler = addrconf_sysctl_ignore_routes_with_linkdown,
},
{
+ .procname = "drop_unicast_in_l2_multicast",
+ .data = &ipv6_devconf.drop_unicast_in_l2_multicast,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec,
+ },
+ {
/* sentinel */
}
},
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 9075acf..31ac3c5 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -134,6 +134,16 @@
IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
goto err;
+ /* If enabled, drop unicast packets that were encapsulated in link-layer
+ * multicast or broadcast to protected against the so-called "hole-196"
+ * attack in 802.11 wireless.
+ */
+ if (!ipv6_addr_is_multicast(&hdr->daddr) &&
+ (skb->pkt_type == PACKET_BROADCAST ||
+ skb->pkt_type == PACKET_MULTICAST) &&
+ idev->cnf.drop_unicast_in_l2_multicast)
+ goto err;
+
/* RFC4291 2.7
* Nodes must not originate a packet to a multicast address whose scope
* field contains the reserved value 0; if such a packet is received, it