cfg80211: Support key configuration for Beacon protection (BIGTK)

IEEE P802.11-REVmd/D3.0 adds support for protecting Beacon frames using
a new set of keys (BIGTK; key index 6..7) similarly to the way
group-addressed Robust Management frames are protected (IGTK; key index
4..5). Extend cfg80211 and nl80211 to allow the new BIGTK to be
configured. Add an extended feature flag to indicate driver support for
the new key index values to avoid array overflows in driver
implementations and also to indicate to user space when this
functionality is available.

Signed-off-by: Jouni Malinen <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Johannes Berg <[e-mail]>

include/net/cfg80211.h

···
  * @set_default_key: set the default key on an interface
  *
  * @set_default_mgmt_key: set the default management frame key on an interface
+
+ * @set_default_beacon_key: set the default Beacon frame key on an interface
  *
  * @set_rekey_data: give the data necessary for GTK rekeying to the driver
  *
···
 	int	(*set_default_mgmt_key)(struct wiphy *wiphy,
 					struct net_device *netdev,
 					u8 key_index);
+	int	(*set_default_beacon_key)(struct wiphy *wiphy,
+					  struct net_device *netdev,
+					  u8 key_index);
 
 	int	(*start_ap)(struct wiphy *wiphy, struct net_device *dev,
 			    struct cfg80211_ap_settings *settings);

include/uapi/linux/nl80211.h

···
  *	See &enum nl80211_key_default_types.
  * @NL80211_KEY_MODE: the mode from enum nl80211_key_mode.
  *	Defaults to @NL80211_KEY_RX_TX.
+ * @NL80211_KEY_DEFAULT_BEACON: flag indicating default Beacon frame key
  *
  * @__NL80211_KEY_AFTER_LAST: internal
  * @NL80211_KEY_MAX: highest key attribute
···
 	NL80211_KEY_TYPE,
 	NL80211_KEY_DEFAULT_TYPES,
 	NL80211_KEY_MODE,
+	NL80211_KEY_DEFAULT_BEACON,
 
 	/* keep last */
 	__NL80211_KEY_AFTER_LAST,
···
  *	feature, which prevents bufferbloat by using the expected transmission
  *	time to limit the amount of data buffered in the hardware.
  *
+ * @NL80211_EXT_FEATURE_BEACON_PROTECTION: The driver supports Beacon protection
+ *	and can receive key configuration for BIGTK using key indexes 6 and 7.
+ *
  * @NUM_NL80211_EXT_FEATURES: number of extended features.
  * @MAX_NL80211_EXT_FEATURES: highest extended feature index.
  */
···
 	NL80211_EXT_FEATURE_SAE_OFFLOAD,
 	NL80211_EXT_FEATURE_VLAN_OFFLOAD,
 	NL80211_EXT_FEATURE_AQL,
+	NL80211_EXT_FEATURE_BEACON_PROTECTION,
 
 	/* add new features before the definition below */
 	NUM_NL80211_EXT_FEATURES,

net/wireless/nl80211.c

···
 	[NL80211_ATTR_KEY] = { .type = NLA_NESTED, },
 	[NL80211_ATTR_KEY_DATA] = { .type = NLA_BINARY,
 				    .len = WLAN_MAX_KEY_LEN },
-	[NL80211_ATTR_KEY_IDX] = NLA_POLICY_MAX(NLA_U8, 5),
+	[NL80211_ATTR_KEY_IDX] = NLA_POLICY_MAX(NLA_U8, 7),
 	[NL80211_ATTR_KEY_CIPHER] = { .type = NLA_U32 },
 	[NL80211_ATTR_KEY_DEFAULT] = { .type = NLA_FLAG },
 	[NL80211_ATTR_KEY_SEQ] = { .type = NLA_BINARY, .len = 16 },
···
 	struct key_params p;
 	int idx;
 	int type;
-	bool def, defmgmt;
+	bool def, defmgmt, defbeacon;
 	bool def_uni, def_multi;
 };
 
···
 
 	k->def = !!tb[NL80211_KEY_DEFAULT];
 	k->defmgmt = !!tb[NL80211_KEY_DEFAULT_MGMT];
+	k->defbeacon = !!tb[NL80211_KEY_DEFAULT_BEACON];
 
 	if (k->def) {
 		k->def_uni = true;
 		k->def_multi = true;
 	}
-	if (k->defmgmt)
+	if (k->defmgmt || k->defbeacon)
 		k->def_multi = true;
 
 	if (tb[NL80211_KEY_IDX])
···
 	if (err)
 		return err;
 
-	if (k->def && k->defmgmt) {
-		GENL_SET_ERR_MSG(info, "key with def && defmgmt is invalid");
+	if ((k->def ? 1 : 0) + (k->defmgmt ? 1 : 0) +
+	    (k->defbeacon ? 1 : 0) > 1) {
+		GENL_SET_ERR_MSG(info,
+				 "key with multiple default flags is invalid");
 		return -EINVAL;
 	}
 
-	if (k->defmgmt) {
+	if (k->defmgmt || k->defbeacon) {
 		if (k->def_uni || !k->def_multi) {
-			GENL_SET_ERR_MSG(info, "defmgmt key must be mcast");
+			GENL_SET_ERR_MSG(info,
+					 "defmgmt/defbeacon key must be mcast");
 			return -EINVAL;
 		}
 	}
···
 						 "defmgmt key idx not 4 or 5");
 				return -EINVAL;
 			}
+		} else if (k->defbeacon) {
+			if (k->idx < 6 || k->idx > 7) {
+				GENL_SET_ERR_MSG(info,
+						 "defbeacon key idx not 6 or 7");
+				return -EINVAL;
+			}
 		} else if (k->def) {
 			if (k->idx < 0 || k->idx > 3) {
 				GENL_SET_ERR_MSG(info, "def key idx not 0-3");
 				return -EINVAL;
 			}
 		} else {
-			if (k->idx < 0 || k->idx > 5) {
-				GENL_SET_ERR_MSG(info, "key idx not 0-5");
+			if (k->idx < 0 || k->idx > 7) {
+				GENL_SET_ERR_MSG(info, "key idx not 0-7");
 				return -EINVAL;
 			}
 		}
···
 	void *hdr;
 	struct sk_buff *msg;
 
-	if (info->attrs[NL80211_ATTR_KEY_IDX])
+	if (info->attrs[NL80211_ATTR_KEY_IDX]) {
 		key_idx = nla_get_u8(info->attrs[NL80211_ATTR_KEY_IDX]);
+		if (key_idx > 5 &&
+		    !wiphy_ext_feature_isset(
+			    &rdev->wiphy,
+			    NL80211_EXT_FEATURE_BEACON_PROTECTION))
+			return -EINVAL;
+	}
 
 	if (info->attrs[NL80211_ATTR_MAC])
 		mac_addr = nla_data(info->attrs[NL80211_ATTR_MAC]);
···
 	/* Only support setting default key and
 	 * Extended Key ID action NL80211_KEY_SET_TX.
 	 */
-	if (!key.def && !key.defmgmt &&
+	if (!key.def && !key.defmgmt && !key.defbeacon &&
 	    !(key.p.mode == NL80211_KEY_SET_TX))
 		return -EINVAL;
 
···
 #ifdef CONFIG_CFG80211_WEXT
 		dev->ieee80211_ptr->wext.default_mgmt_key = key.idx;
 #endif
+	} else if (key.defbeacon) {
+		if (key.def_uni || !key.def_multi) {
+			err = -EINVAL;
+			goto out;
+		}
+
+		if (!rdev->ops->set_default_beacon_key) {
+			err = -EOPNOTSUPP;
+			goto out;
+		}
+
+		err = nl80211_key_allowed(dev->ieee80211_ptr);
+		if (err)
+			goto out;
+
+		err = rdev_set_default_beacon_key(rdev, dev, key.idx);
+		if (err)
+			goto out;
 	} else if (key.p.mode == NL80211_KEY_SET_TX &&
 		   wiphy_ext_feature_isset(&rdev->wiphy,
 					   NL80211_EXT_FEATURE_EXT_KEY_ID)) {

net/wireless/rdev-ops.h

···
 	return ret;
 }
 
+static inline int
+rdev_set_default_beacon_key(struct cfg80211_registered_device *rdev,
+			    struct net_device *netdev, u8 key_index)
+{
+	int ret;
+
+	trace_rdev_set_default_beacon_key(&rdev->wiphy, netdev, key_index);
+	ret = rdev->ops->set_default_beacon_key(&rdev->wiphy, netdev,
+						key_index);
+	trace_rdev_return_int(&rdev->wiphy, ret);
+	return ret;
+}
+
 static inline int rdev_start_ap(struct cfg80211_registered_device *rdev,
 				struct net_device *dev,
 				struct cfg80211_ap_settings *settings)

net/wireless/sme.c

···
 	 * Delete all the keys ... pairwise keys can't really
 	 * exist any more anyway, but default keys might.
 	 */
-	if (rdev->ops->del_key)
-		for (i = 0; i < 6; i++)
+	if (rdev->ops->del_key) {
+		int max_key_idx = 5;
+
+		if (wiphy_ext_feature_isset(
+			    wdev->wiphy,
+			    NL80211_EXT_FEATURE_BEACON_PROTECTION))
+			max_key_idx = 7;
+		for (i = 0; i <= max_key_idx; i++)
 			rdev_del_key(rdev, dev, i, false, NULL);
+	}
 
 	rdev_set_qos_map(rdev, dev, NULL);
 

net/wireless/trace.h

···
 		  WIPHY_PR_ARG, NETDEV_PR_ARG, __entry->key_index)
 );
 
+TRACE_EVENT(rdev_set_default_beacon_key,
+	TP_PROTO(struct wiphy *wiphy, struct net_device *netdev, u8 key_index),
+	TP_ARGS(wiphy, netdev, key_index),
+	TP_STRUCT__entry(
+		WIPHY_ENTRY
+		NETDEV_ENTRY
+		__field(u8, key_index)
+	),
+	TP_fast_assign(
+		WIPHY_ASSIGN;
+		NETDEV_ASSIGN;
+		__entry->key_index = key_index;
+	),
+	TP_printk(WIPHY_PR_FMT ", " NETDEV_PR_FMT ", key index: %u",
+		  WIPHY_PR_ARG, NETDEV_PR_ARG, __entry->key_index)
+);
+
 TRACE_EVENT(rdev_start_ap,
 	TP_PROTO(struct wiphy *wiphy, struct net_device *netdev,
 		 struct cfg80211_ap_settings *settings),

net/wireless/util.c

···
 				   struct key_params *params, int key_idx,
 				   bool pairwise, const u8 *mac_addr)
 {
-	if (key_idx < 0 || key_idx > 5)
+	int max_key_idx = 5;
+
+	if (wiphy_ext_feature_isset(&rdev->wiphy,
+				    NL80211_EXT_FEATURE_BEACON_PROTECTION))
+		max_key_idx = 7;
+	if (key_idx < 0 || key_idx > max_key_idx)
 		return -EINVAL;
 
 	if (!pairwise && mac_addr && !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))