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> (cherry picked from commit dede82143bf1bbf92ea73a519bb0298b19c56cb9) Change-Id: I76c8f84b53e95c40ad3c2b5adac0ec4964cc920c
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@ -1399,6 +1399,12 @@ use_optimistic - BOOLEAN
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0: disabled (default)
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1: enabled
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drop_unicast_in_l2_multicast - BOOLEAN
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Drop any unicast IPv6 packets that are received in link-layer
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multicast (or broadcast) frames.
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By default this is turned off.
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icmp/*:
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ratelimit - INTEGER
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Limit the maximal rates for sending ICMPv6 packets.
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@ -49,6 +49,7 @@ struct ipv6_devconf {
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__s32 mc_forwarding;
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#endif
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__s32 disable_ipv6;
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__s32 drop_unicast_in_l2_multicast;
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__s32 accept_dad;
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__s32 force_tllao;
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__s32 ndisc_notify;
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@ -4430,6 +4430,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
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array[DEVCONF_NDISC_NOTIFY] = cnf->ndisc_notify;
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array[DEVCONF_ACCEPT_RA_MTU] = cnf->accept_ra_mtu;
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array[DEVCONF_USE_OIF_ADDRS_ONLY] = cnf->use_oif_addrs_only;
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array[DEVCONF_DROP_UNICAST_IN_L2_MULTICAST] = cnf->drop_unicast_in_l2_multicast;
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}
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static inline size_t inet6_ifla6_size(void)
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@ -5257,6 +5258,13 @@ static struct addrconf_sysctl_table
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "drop_unicast_in_l2_multicast",
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.data = &ipv6_devconf.drop_unicast_in_l2_multicast,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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/* sentinel */
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}
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@ -130,6 +130,16 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
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IPV6_ADDR_MC_SCOPE(&hdr->daddr) == 1)
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goto err;
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/* If enabled, drop unicast packets that were encapsulated in link-layer
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* multicast or broadcast to protected against the so-called "hole-196"
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* attack in 802.11 wireless.
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*/
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if (!ipv6_addr_is_multicast(&hdr->daddr) &&
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(skb->pkt_type == PACKET_BROADCAST ||
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skb->pkt_type == PACKET_MULTICAST) &&
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idev->cnf.drop_unicast_in_l2_multicast)
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goto err;
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/* RFC4291 2.7
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* Nodes must not originate a packet to a multicast address whose scope
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* field contains the reserved value 0; if such a packet is received, it
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