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Date: Thu, 21 Nov 2013 14:05:54 +0100
From: Johannes Berg <johannes@...solutions.net>
To: linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc: Jouni Malinen <jouni@....qualcomm.com>
Subject: [RFC] wireless, ipv4, ipv6: drop GTK-protected unicast IP packets
From: Jouni Malinen <jouni@....qualcomm.com>
The GTK is shared by all stations in an 802.11 BSS and as such any
one of them can send forged group-addressed frames. To prevent this
kind of attack, drop unicast IP packets if they were protected with
the GTK, i.e. were multicast packets at the 802.11 layer.
Signed-off-by: Jouni Malinen <jouni@....qualcomm.com>
[configuration, IPv6]
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
include/linux/skbuff.h | 5 ++++-
include/net/cfg80211.h | 7 +++++--
include/uapi/linux/nl80211.h | 6 ++++++
net/core/skbuff.c | 1 +
net/ipv4/ip_input.c | 12 ++++++++++++
net/ipv6/ip6_input.c | 11 +++++++++++
net/mac80211/ieee80211_i.h | 3 ++-
net/mac80211/mlme.c | 2 ++
net/mac80211/rx.c | 7 +++++++
net/wireless/nl80211.c | 4 ++++
10 files changed, 54 insertions(+), 4 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2ddb48d..5ed5a19 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -384,6 +384,8 @@ typedef unsigned char *sk_buff_data_t;
* @wifi_acked_valid: wifi_acked was set
* @wifi_acked: whether frame was acked on wifi or not
* @no_fcs: Request NIC to treat last 4 bytes as Ethernet FCS
+ * @drop_unicast: Request protocols to drop frame if it's a unicast frame
+ * in that protocol - used for frames received over wifi multicast
* @dma_cookie: a cookie to one of several possible DMA operations
* done by skb DMA functions
* @napi_id: id of the NAPI struct this skb came from
@@ -498,7 +500,8 @@ struct sk_buff {
* headers if needed
*/
__u8 encapsulation:1;
- /* 7/9 bit hole (depending on ndisc_nodetype presence) */
+ __u8 drop_unicast:1;
+ /* 6/8 bit hole (depending on ndisc_nodetype presence) */
kmemcheck_bitfield_end(flags2);
#if defined CONFIG_NET_DMA || defined CONFIG_NET_RX_BUSY_POLL
diff --git a/include/net/cfg80211.h b/include/net/cfg80211.h
index 6c2bc329..37a4c09 100644
--- a/include/net/cfg80211.h
+++ b/include/net/cfg80211.h
@@ -1560,10 +1560,13 @@ struct cfg80211_auth_request {
*
* @ASSOC_REQ_DISABLE_HT: Disable HT (802.11n)
* @ASSOC_REQ_DISABLE_VHT: Disable VHT
+ * @ASSOC_REQ_DROP_GROUP_PROTECTED_UNICAST: Drop protocol unicast packets
+ * that were group-protected at the link layer.
*/
enum cfg80211_assoc_req_flags {
- ASSOC_REQ_DISABLE_HT = BIT(0),
- ASSOC_REQ_DISABLE_VHT = BIT(1),
+ ASSOC_REQ_DISABLE_HT = BIT(0),
+ ASSOC_REQ_DISABLE_VHT = BIT(1),
+ ASSOC_REQ_DROP_GROUP_PROTECTED_UNICAST = BIT(2),
};
/**
diff --git a/include/uapi/linux/nl80211.h b/include/uapi/linux/nl80211.h
index 4bb8289..8fc8b05 100644
--- a/include/uapi/linux/nl80211.h
+++ b/include/uapi/linux/nl80211.h
@@ -1518,6 +1518,10 @@ enum nl80211_commands {
* @NL80211_ATTR_SUPPORT_5_10_MHZ: A flag indicating that the device supports
* 5 MHz and 10 MHz channel bandwidth.
*
+ * @NL80211_ATTR_DROP_GROUP_PROTECTED_UNICAST: Drop protocol unicast packets
+ * that were group protected at the wireless level. This flag attribute
+ * is valid in the association command.
+ *
* @NL80211_ATTR_MAX: highest attribute number currently defined
* @__NL80211_ATTR_AFTER_LAST: internal use
*/
@@ -1836,6 +1840,8 @@ enum nl80211_attrs {
NL80211_ATTR_SUPPORT_5_10_MHZ,
+ NL80211_ATTR_DROP_GROUP_PROTECTED_UNICAST,
+
/* add attributes here, update the policy in nl80211.c */
__NL80211_ATTR_AFTER_LAST,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index d81cff1..b751e7d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -737,6 +737,7 @@ static void __copy_skb_header(struct sk_buff *new, const struct sk_buff *old)
#endif
new->vlan_proto = old->vlan_proto;
new->vlan_tci = old->vlan_tci;
+ new->drop_unicast = old->drop_unicast;
skb_copy_secmark(new, old);
diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 054a3e9..7de7f84 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -363,6 +363,18 @@ static int ip_rcv_finish(struct sk_buff *skb)
IP_UPD_PO_STATS_BH(dev_net(rt->dst.dev), IPSTATS_MIB_INBCAST,
skb->len);
+ /*
+ * If the received packet was protected in a way that would allow
+ * insider attacks (e.g. IEEE 802.11 networks with GTK shared for all
+ * associated stations in an BSS), group-addressed link layer frames
+ * can be forged. To reduce the effects of such an attack, drop the
+ * packet if it is destined to unicast address, but was sent in a
+ * group-addressed link layer frame.
+ */
+ if (unlikely(skb->drop_unicast &&
+ (rt->rt_type == RTN_UNICAST || rt->rt_type == RTN_LOCAL)))
+ goto drop;
+
return dst_input(skb);
drop:
diff --git a/net/ipv6/ip6_input.c b/net/ipv6/ip6_input.c
index 302d6fb..d9cbf4d 100644
--- a/net/ipv6/ip6_input.c
+++ b/net/ipv6/ip6_input.c
@@ -151,6 +151,17 @@ int ipv6_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt
if (ipv6_addr_is_multicast(&hdr->saddr))
goto err;
+ /*
+ * If the received packet was protected in a way that would allow
+ * insider attacks (e.g. IEEE 802.11 networks with GTK shared for all
+ * associated stations in an BSS), group-addressed link layer frames
+ * can be forged. To reduce the effects of such an attack, drop the
+ * packet if it is destined to unicast address, but was sent in a
+ * group-addressed link layer frame.
+ */
+ if (unlikely(skb->drop_unicast && !ipv6_addr_is_multicast(&hdr->daddr)))
+ goto err;
+
skb->transport_header = skb->network_header + sizeof(*hdr);
IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 61ccf0d..d39cfb5 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -705,7 +705,8 @@ struct ieee80211_sub_if_data {
unsigned long state;
- int drop_unencrypted;
+ bool drop_unencrypted;
+ bool drop_group_protected_unicast;
char name[IFNAMSIZ];
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index e7f0d53..649902b 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -4121,6 +4121,8 @@ int ieee80211_mgd_assoc(struct ieee80211_sub_if_data *sdata,
sdata->control_port_no_encrypt = req->crypto.control_port_no_encrypt;
sdata->encrypt_headroom = ieee80211_cs_headroom(local, &req->crypto,
sdata->vif.type);
+ sdata->drop_group_protected_unicast =
+ req->flags & ASSOC_REQ_DROP_GROUP_PROTECTED_UNICAST;
/* kick off associate process */
diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 5638782..2095be1 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1544,6 +1544,13 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
!is_multicast_ether_addr(hdr->addr1))
rx->key = NULL;
}
+
+ if (rx->key && is_multicast_ether_addr(hdr->addr1) &&
+ rx->sdata->vif.type == NL80211_IFTYPE_STATION &&
+ rx->sdata->drop_group_protected_unicast &&
+ rx->key->conf.cipher != WLAN_CIPHER_SUITE_WEP40 &&
+ rx->key->conf.cipher != WLAN_CIPHER_SUITE_WEP104)
+ rx->skb->drop_unicast = 1;
}
if (rx->key) {
diff --git a/net/wireless/nl80211.c b/net/wireless/nl80211.c
index e39fadc..f8e3c83 100644
--- a/net/wireless/nl80211.c
+++ b/net/wireless/nl80211.c
@@ -357,6 +357,7 @@ static const struct nla_policy nl80211_policy[NL80211_ATTR_MAX+1] = {
[NL80211_ATTR_STA_SUPPORTED_CHANNELS] = { .type = NLA_BINARY },
[NL80211_ATTR_STA_SUPPORTED_OPER_CLASSES] = { .type = NLA_BINARY },
[NL80211_ATTR_HANDLE_DFS] = { .type = NLA_FLAG },
+ [NL80211_ATTR_DROP_GROUP_PROTECTED_UNICAST] = { .type = NLA_FLAG },
};
/* policy for the key attributes */
@@ -6345,6 +6346,9 @@ static int nl80211_associate(struct sk_buff *skb, struct genl_info *info)
sizeof(req.vht_capa));
}
+ if (info->attrs[NL80211_ATTR_DROP_GROUP_PROTECTED_UNICAST])
+ req.flags |= ASSOC_REQ_DROP_GROUP_PROTECTED_UNICAST;
+
err = nl80211_crypto_settings(rdev, info, &req.crypto, 1);
if (!err) {
wdev_lock(dev->ieee80211_ptr);
--
1.8.4.rc3
--
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