mac80211: IEEE 802.11 Extended Key ID support

Add support for Extended Key ID as defined in IEEE 802.11-2016.

 - Implement the nl80211 API for Extended Key ID
 - Extend mac80211 API to allow drivers to support Extended Key ID
 - Enable Extended Key ID by default for drivers only supporting SW
   crypto (e.g. mac80211_hwsim)
 - Allow unicast Tx usage to be supressed (IEEE80211_KEY_FLAG_NO_AUTO_TX)
 - Select the decryption key based on the MPDU keyid
 - Enforce existing assumptions in the code that rekeys don't change the
   cipher

Signed-off-by: Alexander Wetzel <alexander@wetzel-home.de>
[remove module parameter]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 39 insertions, 35 deletions

diff --git a/net/mac80211/rx.c b/net/mac80211/rx.c
index 7f8d93401ce0..4a03c18b39a8 100644
--- a/net/mac80211/rx.c
+++ b/net/mac80211/rx.c
@@ -1005,23 +1005,43 @@ static int ieee80211_get_mmie_keyidx(struct sk_buff *skb)
 	return -1;
 }
 
-static int ieee80211_get_cs_keyid(const struct ieee80211_cipher_scheme *cs,
-				  struct sk_buff *skb)
+static int ieee80211_get_keyid(struct sk_buff *skb,
+			       const struct ieee80211_cipher_scheme *cs)
 {
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 	__le16 fc;
 	int hdrlen;
+	int minlen;
+	u8 key_idx_off;
+	u8 key_idx_shift;
 	u8 keyid;
 
 	fc = hdr->frame_control;
 	hdrlen = ieee80211_hdrlen(fc);
 
-	if (skb->len < hdrlen + cs->hdr_len)
+	if (cs) {
+		minlen = hdrlen + cs->hdr_len;
+		key_idx_off = hdrlen + cs->key_idx_off;
+		key_idx_shift = cs->key_idx_shift;
+	} else {
+		/* WEP, TKIP, CCMP and GCMP */
+		minlen = hdrlen + IEEE80211_WEP_IV_LEN;
+		key_idx_off = hdrlen + 3;
+		key_idx_shift = 6;
+	}
+
+	if (unlikely(skb->len < minlen))
 		return -EINVAL;
 
-	skb_copy_bits(skb, hdrlen + cs->key_idx_off, &keyid, 1);
-	keyid &= cs->key_idx_mask;
-	keyid >>= cs->key_idx_shift;
+	skb_copy_bits(skb, key_idx_off, &keyid, 1);
+
+	if (cs)
+		keyid &= cs->key_idx_mask;
+	keyid >>= key_idx_shift;
+
+	/* cs could use more than the usual two bits for the keyid */
+	if (unlikely(keyid >= NUM_DEFAULT_KEYS))
+		return -EINVAL;
 
 	return keyid;
 }
@@ -1852,9 +1872,9 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 	struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 	int keyidx;
-	int hdrlen;
 	ieee80211_rx_result result = RX_DROP_UNUSABLE;
 	struct ieee80211_key *sta_ptk = NULL;
+	struct ieee80211_key *ptk_idx = NULL;
 	int mmie_keyidx = -1;
 	__le16 fc;
 	const struct ieee80211_cipher_scheme *cs = NULL;
@@ -1892,21 +1912,24 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 
 	if (rx->sta) {
 		int keyid = rx->sta->ptk_idx;
+		sta_ptk = rcu_dereference(rx->sta->ptk[keyid]);
 
-		if (ieee80211_has_protected(fc) && rx->sta->cipher_scheme) {
+		if (ieee80211_has_protected(fc)) {
 			cs = rx->sta->cipher_scheme;
-			keyid = ieee80211_get_cs_keyid(cs, rx->skb);
+			keyid = ieee80211_get_keyid(rx->skb, cs);
+
 			if (unlikely(keyid < 0))
 				return RX_DROP_UNUSABLE;
+
+			ptk_idx = rcu_dereference(rx->sta->ptk[keyid]);
 		}
-		sta_ptk = rcu_dereference(rx->sta->ptk[keyid]);
 	}
 
 	if (!ieee80211_has_protected(fc))
 		mmie_keyidx = ieee80211_get_mmie_keyidx(rx->skb);
 
 	if (!is_multicast_ether_addr(hdr->addr1) && sta_ptk) {
-		rx->key = sta_ptk;
+		rx->key = ptk_idx ? ptk_idx : sta_ptk;
 		if ((status->flag & RX_FLAG_DECRYPTED) &&
 		    (status->flag & RX_FLAG_IV_STRIPPED))
 			return RX_CONTINUE;
@@ -1966,8 +1989,6 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 		}
 		return RX_CONTINUE;
 	} else {
-		u8 keyid;
-
 		/*
 		 * The device doesn't give us the IV so we won't be
 		 * able to look up the key. That's ok though, we
@@ -1981,23 +2002,10 @@ ieee80211_rx_h_decrypt(struct ieee80211_rx_data *rx)
 		    (status->flag & RX_FLAG_IV_STRIPPED))
 			return RX_CONTINUE;
 
-		hdrlen = ieee80211_hdrlen(fc);
-
-		if (cs) {
-			keyidx = ieee80211_get_cs_keyid(cs, rx->skb);
+		keyidx = ieee80211_get_keyid(rx->skb, cs);
 
-			if (unlikely(keyidx < 0))
-				return RX_DROP_UNUSABLE;
-		} else {
-			if (rx->skb->len < 8 + hdrlen)
-				return RX_DROP_UNUSABLE; /* TODO: count this? */
-			/*
-			 * no need to call ieee80211_wep_get_keyidx,
-			 * it verifies a bunch of things we've done already
-			 */
-			skb_copy_bits(rx->skb, hdrlen + 3, &keyid, 1);
-			keyidx = keyid >> 6;
-		}
+		if (unlikely(keyidx < 0))
+			return RX_DROP_UNUSABLE;
 
 		/* check per-station GTK first, if multicast packet */
 		if (is_multicast_ether_addr(hdr->addr1) && rx->sta)
@@ -4042,12 +4050,8 @@ void ieee80211_check_fast_rx(struct sta_info *sta)
 		case WLAN_CIPHER_SUITE_GCMP_256:
 			break;
 		default:
-			/* we also don't want to deal with WEP or cipher scheme
-			 * since those require looking up the key idx in the
-			 * frame, rather than assuming the PTK is used
-			 * (we need to revisit this once we implement the real
-			 * PTK index, which is now valid in the spec, but we
-			 * haven't implemented that part yet)
+			/* We also don't want to deal with
+			 * WEP or cipher scheme.
 			 */
 			goto clear_rcu;
 		}