wifi: mac80211: restrict public action ECSA frame handling

Public action extended channel switch announcement (ECSA)
frames cannot be protected well, the spec is unclear about
what should happen in the presence of stations that can
receive protected dual and stations that cannot.

Mitigate these issues by not treating public action frames
as the absolute truth, only treat them as a hint to stop
transmitting (quiet mode), and do the remainder of the CSA
handling only when receiving the next beacon (or protected
action frame) that contains the CSA; or, if it doesn't,
simply stop being quiet and continue operating normally.

This limits the exposure to malicious ECSA public action
frames, since they cannot cause a disconnect now, only a
short interruption in traffic.

Reviewed-by: Miriam Rachel Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20240612143037.ec7ccc45903e.Ife17d55c7ecbf98060f9c52889f3c8ba48798970@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

diff --git a/net/mac80211/ibss.c b/net/mac80211/ibss.c
index bf338f3d4dd329abd2b53627d881611859f6f90f..7db4c3ee7e6d5562976679a1fc147adc870635db 100644 (file)
--- a/net/mac80211/ibss.c
+++ b/net/mac80211/ibss.c
@@ -785,7 +785,8 @@ ieee80211_ibss_process_chanswitch(struct ieee80211_sub_if_data *sdata,
        err = ieee80211_parse_ch_switch_ie(sdata, elems,
                                           ifibss->chandef.chan->band,
                                           vht_cap_info, &conn,
-                                          ifibss->bssid, &csa_ie);
+                                          ifibss->bssid, false,
+                                          &csa_ie);
        /* can't switch to destination channel, fail */
        if (err < 0)
                goto disconnect;

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index b482763e9f99c1a1067422ffb8fdc1fb9c48abde..cb3e28f880893af564c64dc4307c1fb5063f7bcd 100644 (file)
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -2218,6 +2218,8 @@ void ieee80211_process_measurement_req(struct ieee80211_sub_if_data *sdata,
  * @conn: contains information about own capabilities and restrictions
  *     to decide which channel switch announcements can be accepted
  * @bssid: the currently connected bssid (for reporting)
+ * @unprot_action: whether the frame was an unprotected frame or not,
+ *     used for reporting
  * @csa_ie: parsed 802.11 csa elements on count, mode, chandef and mesh ttl.
  *     All of them will be filled with if success only.
  * Return: 0 on success, <0 on error and >0 if there is nothing to parse.
@@ -2227,7 +2229,7 @@ int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
                                 enum nl80211_band current_band,
                                 u32 vht_cap_info,
                                 struct ieee80211_conn_settings *conn,
-                                u8 *bssid,
+                                u8 *bssid, bool unprot_action,
                                 struct ieee80211_csa_ie *csa_ie);
 
 /* Suspend/resume and hw reconfiguration */

diff --git a/net/mac80211/mesh.c b/net/mac80211/mesh.c
index 6d4510221c98e695ea140e40e5e9ec5cbf385a5e..f94e4be0be12ca3cf2976165c7b9e170716d4abf 100644 (file)
--- a/net/mac80211/mesh.c
+++ b/net/mac80211/mesh.c
@@ -1312,7 +1312,7 @@ ieee80211_mesh_process_chnswitch(struct ieee80211_sub_if_data *sdata,
        memset(&params, 0, sizeof(params));
        err = ieee80211_parse_ch_switch_ie(sdata, elems, sband->band,
                                           vht_cap_info, &conn,
-                                          sdata->vif.addr,
+                                          sdata->vif.addr, false,
                                           &csa_ie);
        if (err < 0)
                return false;

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index ac376ec47a592b2cf835e3fa424f0aa64aa76f80..fff158b1615f133c8b73a9c4d37b006058bdf480 100644 (file)
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -2352,7 +2352,8 @@ ieee80211_sta_other_link_csa_disappeared(struct ieee80211_link_data *link,
 enum ieee80211_csa_source {
        IEEE80211_CSA_SOURCE_BEACON,
        IEEE80211_CSA_SOURCE_OTHER_LINK,
-       IEEE80211_CSA_SOURCE_ACTION,
+       IEEE80211_CSA_SOURCE_PROT_ACTION,
+       IEEE80211_CSA_SOURCE_UNPROT_ACTION,
 };
 
 static void
@@ -2393,7 +2394,9 @@ ieee80211_sta_process_chanswitch(struct ieee80211_link_data *link,
                                                   current_band,
                                                   bss->vht_cap_info,
                                                   &link->u.mgd.conn,
-                                                  link->u.mgd.bssid, &csa_ie);
+                                                  link->u.mgd.bssid,
+                                                  source == IEEE80211_CSA_SOURCE_UNPROT_ACTION,
+                                                  &csa_ie);
                if (res == 0) {
                        ch_switch.block_tx = csa_ie.mode;
                        ch_switch.chandef = csa_ie.chanreq.oper;
@@ -2412,12 +2415,17 @@ ieee80211_sta_process_chanswitch(struct ieee80211_link_data *link,
                res = 1;
        }
 
-       if (res < 0)
+       if (res < 0) {
+               /* ignore this case, not a protected frame */
+               if (source == IEEE80211_CSA_SOURCE_UNPROT_ACTION)
+                       return;
                goto drop_connection;
+       }
 
        if (link->conf->csa_active) {
                switch (source) {
-               case IEEE80211_CSA_SOURCE_ACTION:
+               case IEEE80211_CSA_SOURCE_PROT_ACTION:
+               case IEEE80211_CSA_SOURCE_UNPROT_ACTION:
                        /* already processing - disregard action frames */
                        return;
                case IEEE80211_CSA_SOURCE_BEACON:
@@ -2466,9 +2474,35 @@ ieee80211_sta_process_chanswitch(struct ieee80211_link_data *link,
                }
        }
 
-       /* nothing to do at all - no active CSA nor a new one */
-       if (res)
+       /* no active CSA nor a new one */
+       if (res) {
+               /*
+                * However, we may have stopped queues when receiving a public
+                * action frame that couldn't be protected, if it had the quiet
+                * bit set. This is a trade-off, we want to be quiet as soon as
+                * possible, but also don't trust the public action frame much,
+                * as it can't be protected.
+                */
+               if (unlikely(link->u.mgd.csa.blocked_tx)) {
+                       link->u.mgd.csa.blocked_tx = false;
+                       ieee80211_vif_unblock_queues_csa(sdata);
+               }
+               return;
+       }
+
+       /*
+        * We don't really trust public action frames, but block queues (go to
+        * quiet mode) for them anyway, we should get a beacon soon to either
+        * know what the CSA really is, or figure out the public action frame
+        * was actually an attack.
+        */
+       if (source == IEEE80211_CSA_SOURCE_UNPROT_ACTION) {
+               if (csa_ie.mode) {
+                       link->u.mgd.csa.blocked_tx = true;
+                       ieee80211_vif_block_queues_csa(sdata);
+               }
                return;
+       }
 
        if (link->conf->chanreq.oper.chan->band !=
            csa_ie.chanreq.oper.chan->band) {
@@ -7453,12 +7487,16 @@ void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
                                        mgmt->u.action.u.chan_switch.variable,
                                        ies_len, true, NULL);
 
-                       if (elems && !elems->parse_error)
+                       if (elems && !elems->parse_error) {
+                               enum ieee80211_csa_source src =
+                                       IEEE80211_CSA_SOURCE_PROT_ACTION;
+
                                ieee80211_sta_process_chanswitch(link,
                                                                 rx_status->mactime,
                                                                 rx_status->device_timestamp,
                                                                 elems, elems,
-                                                                IEEE80211_CSA_SOURCE_ACTION);
+                                                                src);
+                       }
                        kfree(elems);
                } else if (mgmt->u.action.category == WLAN_CATEGORY_PUBLIC) {
                        struct ieee802_11_elems *elems;
@@ -7479,6 +7517,9 @@ void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
                                        ies_len, true, NULL);
 
                        if (elems && !elems->parse_error) {
+                               enum ieee80211_csa_source src =
+                                       IEEE80211_CSA_SOURCE_UNPROT_ACTION;
+
                                /* for the handling code pretend it was an IE */
                                elems->ext_chansw_ie =
                                        &mgmt->u.action.u.ext_chan_switch.data;
@@ -7487,7 +7528,7 @@ void ieee80211_sta_rx_queued_mgmt(struct ieee80211_sub_if_data *sdata,
                                                                 rx_status->mactime,
                                                                 rx_status->device_timestamp,
                                                                 elems, elems,
-                                                                IEEE80211_CSA_SOURCE_ACTION);
+                                                                src);
                        }
 
                        kfree(elems);

diff --git a/net/mac80211/spectmgmt.c b/net/mac80211/spectmgmt.c
index df96d3db1c0e6ed106e7b0032657c6f7e4f591ce..e91ca4ccdd370edcf1a3f7bf92953dca8fa5928c 100644 (file)
--- a/net/mac80211/spectmgmt.c
+++ b/net/mac80211/spectmgmt.c
@@ -223,7 +223,7 @@ int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
                                 enum nl80211_band current_band,
                                 u32 vht_cap_info,
                                 struct ieee80211_conn_settings *conn,
-                                u8 *bssid,
+                                u8 *bssid, bool unprot_action,
                                 struct ieee80211_csa_ie *csa_ie)
 {
        enum nl80211_band new_band = current_band;
@@ -258,8 +258,10 @@ int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
 
                if (!ieee80211_operating_class_to_band(new_op_class, &new_band)) {
                        new_op_class = 0;
-                       sdata_info(sdata, "cannot understand ECSA IE operating class, %d, ignoring\n",
-                                  ext_chansw_elem->new_operating_class);
+                       if (!unprot_action)
+                               sdata_info(sdata,
+                                          "cannot understand ECSA IE operating class, %d, ignoring\n",
+                                          ext_chansw_elem->new_operating_class);
                } else {
                        new_chan_no = ext_chansw_elem->new_ch_num;
                        csa_ie->count = ext_chansw_elem->count;
@@ -293,9 +295,10 @@ int ieee80211_parse_ch_switch_ie(struct ieee80211_sub_if_data *sdata,
        new_freq = ieee80211_channel_to_frequency(new_chan_no, new_band);
        new_chan = ieee80211_get_channel(sdata->local->hw.wiphy, new_freq);
        if (!new_chan || new_chan->flags & IEEE80211_CHAN_DISABLED) {
-               sdata_info(sdata,
-                          "BSS %pM switches to unsupported channel (%d MHz), disconnecting\n",
-                          bssid, new_freq);
+               if (!unprot_action)
+                       sdata_info(sdata,
+                                  "BSS %pM switches to unsupported channel (%d MHz), disconnecting\n",
+                                  bssid, new_freq);
                return -EINVAL;
        }