mac80211: get a TKIP phase key from skb

This patch makes mac80211 able to compute a TKIP key from an skb.
The requested key can be a phase 1 or a phase 2 key.
This is useful for drivers who need to provide tkip key to their
HW to enable HW encryption.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/tkip.c

@@ -214,6 +214,59 @@ void ieee80211_tkip_gen_rc4key(struct ieee80211_key *key, u8 *ta,
 			   key->u.tkip.iv16, rc4key);
 }
 
+void ieee80211_get_tkip_key(struct ieee80211_key_conf *keyconf,
+			struct sk_buff *skb, enum ieee80211_tkip_key_type type,
+			u8 *outkey)
+{
+	struct ieee80211_key *key = (struct ieee80211_key *)
+			container_of(keyconf, struct ieee80211_key, conf);
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *) skb->data;
+	u8 *data = (u8 *) hdr;
+	u16 fc = le16_to_cpu(hdr->frame_control);
+	int hdr_len = ieee80211_get_hdrlen(fc);
+	u8 *ta = hdr->addr2;
+	u16 iv16;
+	u32 iv32;
+
+	iv16 = data[hdr_len] << 8;
+	iv16 += data[hdr_len + 2];
+	iv32 = data[hdr_len + 4] +
+		(data[hdr_len + 5] >> 8) +
+		(data[hdr_len + 6] >> 16) +
+		(data[hdr_len + 7] >> 24);
+
+#ifdef CONFIG_TKIP_DEBUG
+	printk(KERN_DEBUG "TKIP encrypt: iv16 = 0x%04x, iv32 = 0x%08x\n",
+			iv16, iv32);
+
+	if (iv32 != key->u.tkip.iv32) {
+		printk(KERN_DEBUG "skb: iv32 = 0x%08x key: iv32 = 0x%08x\n",
+			iv32, key->u.tkip.iv32);
+		printk(KERN_DEBUG "Wrap around of iv16 in the middle of a "
+			"fragmented packet\n");
+	}
+#endif /* CONFIG_TKIP_DEBUG */
+
+	/* Update the p1k only when the iv16 in the packet wraps around, this
+	 * might occur after the wrap around of iv16 in the key in case of
+	 * fragmented packets. */
+	if (iv16 == 0 || !key->u.tkip.tx_initialized) {
+		/* IV16 wrapped around - perform TKIP phase 1 */
+		tkip_mixing_phase1(ta, &key->conf.key[ALG_TKIP_TEMP_ENCR_KEY],
+			iv32, key->u.tkip.p1k);
+		key->u.tkip.tx_initialized = 1;
+	}
+
+	if (type == IEEE80211_TKIP_P1_KEY) {
+		memcpy(outkey, key->u.tkip.p1k, sizeof(u16) * 5);
+		return;
+	}
+
+	tkip_mixing_phase2(key->u.tkip.p1k,
+		&key->conf.key[ALG_TKIP_TEMP_ENCR_KEY],	iv16, outkey);
+}
+EXPORT_SYMBOL(ieee80211_get_tkip_key);
+
 /* Encrypt packet payload with TKIP using @key. @pos is a pointer to the
  * beginning of the buffer containing payload. This payload must include
  * headroom of eight octets for IV and Ext. IV and taildroom of four octets