From: Johannes Berg <johannes.b...@intel.com>
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 <j...@ssi.bg>
Signed-off-by: Johannes Berg <johannes.b...@intel.com>
---
Documentation/networking/ip-sysctl.txt | 6 ++++++
include/linux/ipv6.h | 1 +
include/uapi/linux/ipv6.h | 1 +
net/ipv6/addrconf.c | 8 ++++++++
net/ipv6/ip6_input.c | 10 ++++++++++
5 files changed, 26 insertions(+)
diff --git a/Documentation/networking/ip-sysctl.txt
b/Documentation/networking/ip-sysctl.txt
index 56bb6dd881bd..428fb48a19fc 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1666,6 +1666,12 @@ stable_secret - IPv6 address
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 0ef2a97ccdb5..34317cb6a6fc 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -50,6 +50,7 @@ struct ipv6_devconf {
__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 38b4fef20219..4c413570efe8 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -174,6 +174,7 @@ enum {
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 d72fa90d6feb..35f880bcf626 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4672,6 +4672,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf
*cnf,
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)
@@ -5734,6 +5735,13 @@ static struct addrconf_sysctl_table
.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 9075acf081dd..31ac3c56da4b 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -134,6 +134,16 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev,
struct packet_type *pt
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
--
2.7.0
