wifi: cfg80211: clarify and tighten key checks

Currently, we accept per-STA GTK for any interface type
if the IBSS_RSN flag is set, which doesn't make sense,
and also accept various key indices that aren't really
(meant to be) supported, such as IGTK/BIGTK on IBSS or
AP_VLAN etc.

For MESH and NAN_DATA interface types, per-STA GTKs are
required, so their support shouldn't depend on IBSS_RSN.

Conversely a driver setting IBSS_RSN doesn't really say
it also accepts per-STA GTK for other interface types.

Move more checks into cfg80211_valid_key_idx() and make
them more precise:
 - allow IGTK and, if supported, BIGTK for NAN
 - allow per-STA (RX) GTK only for
   - NAN_DATA
   - IBSS if IBSS_RSN is supported
   - MESH
 - allow B/I/GTK for station/P2P-client without mac_addr
   for RX with the current AP (historic API quirk),
   subject to support
 - allow TX GTK for AP/P2P-GO/AP_VLAN
 - allow TX IGTK/BIGTK for AP/P2P-GO subject to support

Other settings are rejected, clearing up corner cases
and disallowing unexpected settings.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://patch.msgid.link/20260715212403.725e6b63e890.I24684374112bb94d0633d61ef76ecb8a1517f7f1@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Author: jmberg-intel

net/wireless/core.h

@@ -443,8 +443,9 @@ void cfg80211_sme_abandon_assoc(struct wireless_dev *wdev);
 
 /* internal helpers */
 bool cfg80211_supported_cipher_suite(struct wiphy *wiphy, u32 cipher);
-bool cfg80211_valid_key_idx(struct cfg80211_registered_device *rdev,
-			    int key_idx, bool pairwise);
+bool cfg80211_valid_key_idx(struct wireless_dev *wdev,
+			    int key_idx, bool pairwise,
+			    const u8 *mac_addr);
 int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
 				   struct wireless_dev *wdev,
 				   struct key_params *params, int key_idx,

net/wireless/nl80211.c

@@ -5409,7 +5409,7 @@ static int nl80211_get_key(struct sk_buff *skb, struct genl_info *info)
 	if (!rdev->ops->get_key)
 		return -EOPNOTSUPP;
 
-	if (!pairwise && mac_addr && !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))
+	if (!cfg80211_valid_key_idx(wdev, key_idx, pairwise, mac_addr))
 		return -ENOENT;
 
 	msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
@@ -5663,19 +5663,16 @@ static int nl80211_del_key(struct sk_buff *skb, struct genl_info *info)
 	    key.type != NL80211_KEYTYPE_GROUP)
 		return -EINVAL;
 
-	if (!cfg80211_valid_key_idx(rdev, key.idx,
-				    key.type == NL80211_KEYTYPE_PAIRWISE))
+	if (!cfg80211_valid_key_idx(wdev, key.idx,
+				    key.type == NL80211_KEYTYPE_PAIRWISE,
+				    mac_addr))
 		return -EINVAL;
 
 	if (!rdev->ops->del_key)
 		return -EOPNOTSUPP;
 
 	err = nl80211_key_allowed(wdev);
 
-	if (key.type == NL80211_KEYTYPE_GROUP && mac_addr &&
-	    !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))
-		err = -ENOENT;
-
 	if (!err)
 		err = nl80211_validate_key_link_id(info, wdev, link_id,
 				key.type == NL80211_KEYTYPE_PAIRWISE);

net/wireless/util.c

@@ -241,10 +241,8 @@ bool cfg80211_supported_cipher_suite(struct wiphy *wiphy, u32 cipher)
 	return false;
 }
 
-static bool
-cfg80211_igtk_cipher_supported(struct cfg80211_registered_device *rdev)
+static bool cfg80211_igtk_cipher_supported(struct wiphy *wiphy)
 {
-	struct wiphy *wiphy = &rdev->wiphy;
 	int i;
 
 	for (i = 0; i < wiphy->n_cipher_suites; i++) {
@@ -260,41 +258,94 @@ cfg80211_igtk_cipher_supported(struct cfg80211_registered_device *rdev)
 	return false;
 }
 
-bool cfg80211_valid_key_idx(struct cfg80211_registered_device *rdev,
-			    int key_idx, bool pairwise)
+bool cfg80211_valid_key_idx(struct wireless_dev *wdev,
+			    int key_idx, bool pairwise,
+			    const u8 *mac_addr)
 {
-	int max_key_idx;
-
-	if (pairwise)
-		max_key_idx = 3;
-	else if (wiphy_ext_feature_isset(&rdev->wiphy,
-					 NL80211_EXT_FEATURE_BEACON_PROTECTION) ||
-		 wiphy_ext_feature_isset(&rdev->wiphy,
-					 NL80211_EXT_FEATURE_BEACON_PROTECTION_CLIENT))
-		max_key_idx = 7;
-	else if (cfg80211_igtk_cipher_supported(rdev))
-		max_key_idx = 5;
-	else
-		max_key_idx = 3;
+	if (WARN_ON(!wdev))
+		return false;
 
-	if (key_idx < 0 || key_idx > max_key_idx)
+	if (key_idx < 0)
 		return false;
 
-	return true;
+	/*
+	 * Can't differentiate ciphers here so allow 0..3.
+	 * Pairwise keys must be for a station (MAC address given).
+	 */
+	if (pairwise) {
+		if (!mac_addr)
+			return false;
+
+		return key_idx < 4;
+	}
+
+	/*
+	 * For group keys, mac_addr==NULL means setting a group key
+	 * for TX, which is only supported on some interface types,
+	 * except for STATION/P2P_CLIENT, where it's setting the RX
+	 * key with the current AP (for legacy reasons.)
+	 *
+	 * Apart from that exception, a non-NULL mac_addr means RX
+	 * key being set.
+	 */
+
+	switch (wdev->iftype) {
+	case NL80211_IFTYPE_ADHOC:
+		if (!(wdev->wiphy->flags & WIPHY_FLAG_IBSS_RSN))
+			return false;
+		fallthrough;
+	case NL80211_IFTYPE_MESH_POINT:
+		/* no support for IGTK/BIGTK (yet?) */
+		return key_idx < 4;
+	case NL80211_IFTYPE_NAN_DATA:
+		/* these always need to support per-STA GTK */
+		return key_idx < 4;
+	case NL80211_IFTYPE_NAN:
+		/* no data */
+		if (key_idx < 4)
+			return false;
+		/* NAN reused this flag */
+		if (wiphy_ext_feature_isset(wdev->wiphy,
+					    NL80211_EXT_FEATURE_BEACON_PROTECTION))
+			return key_idx <= 7;
+		return key_idx <= 5;
+	case NL80211_IFTYPE_STATION:
+	case NL80211_IFTYPE_P2P_CLIENT:
+		/* see note about exception above */
+		if (mac_addr)
+			return false;
+		/* BIGTK support implies IGTK support */
+		if (wiphy_ext_feature_isset(wdev->wiphy,
+					    NL80211_EXT_FEATURE_BEACON_PROTECTION_CLIENT))
+			return key_idx <= 7;
+		fallthrough;
+	case NL80211_IFTYPE_AP:
+	case NL80211_IFTYPE_P2P_GO:
+		/* no RX with [B]IGTK */
+		if (mac_addr)
+			return false;
+		if (wiphy_ext_feature_isset(wdev->wiphy,
+					    NL80211_EXT_FEATURE_BEACON_PROTECTION))
+			return key_idx <= 7;
+		fallthrough;
+	case NL80211_IFTYPE_AP_VLAN:
+		/* no RX with GTK */
+		if (mac_addr)
+			return false;
+		if (cfg80211_igtk_cipher_supported(wdev->wiphy))
+			return key_idx <= 5;
+		return key_idx <= 3;
+	default:
+		return false;
+	}
 }
 
 int cfg80211_validate_key_settings(struct cfg80211_registered_device *rdev,
 				   struct wireless_dev *wdev,
 				   struct key_params *params, int key_idx,
 				   bool pairwise, const u8 *mac_addr)
 {
-	if (!cfg80211_valid_key_idx(rdev, key_idx, pairwise))
-		return -EINVAL;
-
-	if (!pairwise && mac_addr && !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))
-		return -EINVAL;
-
-	if (pairwise && !mac_addr)
+	if (!cfg80211_valid_key_idx(wdev, key_idx, pairwise, mac_addr))
 		return -EINVAL;
 
 	switch (params->cipher) {

net/wireless/wext-compat.c

@@ -454,8 +454,7 @@ static int cfg80211_set_encryption(struct cfg80211_registered_device *rdev,
 				rejoin = true;
 			}
 
-			if (!pairwise && addr &&
-			    !(rdev->wiphy.flags & WIPHY_FLAG_IBSS_RSN))
+			if (!cfg80211_valid_key_idx(wdev, idx, pairwise, addr))
 				err = -ENOENT;
 			else
 				err = rdev_del_key(rdev, wdev, -1, idx, pairwise,