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   1 From: Johannes Berg <johannes.berg@intel.com>
   2 Date: Tue, 11 May 2021 20:02:50 +0200
   3 Subject: [PATCH] mac80211: do not accept/forward invalid EAPOL frames
   4
   5 EAPOL frames are used for authentication and key management between the
   6 AP and each individual STA associated in the BSS. Those frames are not
   7 supposed to be sent by one associated STA to another associated STA
   8 (either unicast for broadcast/multicast).
   9
  10 Similarly, in 802.11 they're supposed to be sent to the authenticator
  11 (AP) address.
  12
  13 Since it is possible for unexpected EAPOL frames to result in misbehavior
  14 in supplicant implementations, it is better for the AP to not allow such
  15 cases to be forwarded to other clients either directly, or indirectly if
  16 the AP interface is part of a bridge.
  17
  18 Accept EAPOL (control port) frames only if they're transmitted to the
  19 own address, or, due to interoperability concerns, to the PAE group
  20 address.
  21
  22 Disable forwarding of EAPOL (or well, the configured control port
  23 protocol) frames back to wireless medium in all cases. Previously, these
  24 frames were accepted from fully authenticated and authorized stations
  25 and also from unauthenticated stations for one of the cases.
  26
  27 Additionally, to avoid forwarding by the bridge, rewrite the PAE group
  28 address case to the local MAC address.
  29
  30 Cc: stable@vger.kernel.org
  31 Co-developed-by: Jouni Malinen <jouni@codeaurora.org>
  32 Signed-off-by: Jouni Malinen <jouni@codeaurora.org>
  33 Signed-off-by: Johannes Berg <johannes.berg@intel.com>
  34 ---
  35
  36 --- a/net/mac80211/rx.c
  37 +++ b/net/mac80211/rx.c
  38 @@ -2541,13 +2541,13 @@ static bool ieee80211_frame_allowed(stru
  39         struct ethhdr *ehdr = (struct ethhdr *) rx->skb->data;
  40
  41         /*
  42 -        * Allow EAPOL frames to us/the PAE group address regardless
  43 -        * of whether the frame was encrypted or not.
  44 +        * Allow EAPOL frames to us/the PAE group address regardless of
  45 +        * whether the frame was encrypted or not, and always disallow
  46 +        * all other destination addresses for them.
  47          */
  48 -       if (ehdr->h_proto == rx->sdata->control_port_protocol &&
  49 -           (ether_addr_equal(ehdr->h_dest, rx->sdata->vif.addr) ||
  50 -            ether_addr_equal(ehdr->h_dest, pae_group_addr)))
  51 -               return true;
  52 +       if (unlikely(ehdr->h_proto == rx->sdata->control_port_protocol))
  53 +               return ether_addr_equal(ehdr->h_dest, rx->sdata->vif.addr) ||
  54 +                      ether_addr_equal(ehdr->h_dest, pae_group_addr);
  55
  56         if (ieee80211_802_1x_port_control(rx) ||
  57             ieee80211_drop_unencrypted(rx, fc))
  58 @@ -2572,8 +2572,28 @@ static void ieee80211_deliver_skb_to_loc
  59                 cfg80211_rx_control_port(dev, skb, noencrypt);
  60                 dev_kfree_skb(skb);
  61         } else {
  62 +               struct ethhdr *ehdr = (void *)skb_mac_header(skb);
  63 +
  64                 memset(skb->cb, 0, sizeof(skb->cb));
  65
  66 +               /*
  67 +                * 802.1X over 802.11 requires that the authenticator address
  68 +                * be used for EAPOL frames. However, 802.1X allows the use of
  69 +                * the PAE group address instead. If the interface is part of
  70 +                * a bridge and we pass the frame with the PAE group address,
  71 +                * then the bridge will forward it to the network (even if the
  72 +                * client was not associated yet), which isn't supposed to
  73 +                * happen.
  74 +                * To avoid that, rewrite the destination address to our own
  75 +                * address, so that the authenticator (e.g. hostapd) will see
  76 +                * the frame, but bridge won't forward it anywhere else. Note
  77 +                * that due to earlier filtering, the only other address can
  78 +                * be the PAE group address.
  79 +                */
  80 +               if (unlikely(skb->protocol == sdata->control_port_protocol &&
  81 +                            !ether_addr_equal(ehdr->h_dest, sdata->vif.addr)))
  82 +                       ether_addr_copy(ehdr->h_dest, sdata->vif.addr);
  83 +
  84                 /* deliver to local stack */
  85                 if (rx->list)
  86  #if LINUX_VERSION_IS_GEQ(4,19,0)
  87 @@ -2617,6 +2637,7 @@ ieee80211_deliver_skb(struct ieee80211_r
  88         if ((sdata->vif.type == NL80211_IFTYPE_AP ||
  89              sdata->vif.type == NL80211_IFTYPE_AP_VLAN) &&
  90             !(sdata->flags & IEEE80211_SDATA_DONT_BRIDGE_PACKETS) &&
  91 +           ehdr->h_proto != rx->sdata->control_port_protocol &&
  92             (sdata->vif.type != NL80211_IFTYPE_AP_VLAN || !sdata->u.vlan.sta)) {
  93                 if (is_multicast_ether_addr(ehdr->h_dest) &&
  94                     ieee80211_vif_get_num_mcast_if(sdata) != 0) {