mac80211: 802.11w - CCMP for management frames

Extend CCMP to support encryption and decryption of unicast management
frames.

Signed-off-by: Jouni Malinen <j@w1.fi>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

include/linux/ieee80211.h

@@ -1030,6 +1030,7 @@ enum ieee80211_category {
 	WLAN_CATEGORY_QOS = 1,
 	WLAN_CATEGORY_DLS = 2,
 	WLAN_CATEGORY_BACK = 3,
+	WLAN_CATEGORY_PUBLIC = 4,
 	WLAN_CATEGORY_WMM = 17,
 };
 
@@ -1185,6 +1186,35 @@ static inline u8 *ieee80211_get_DA(struct ieee80211_hdr *hdr)
 		return hdr->addr1;
 }
 
+/**
+ * ieee80211_is_robust_mgmt_frame - check if frame is a robust management frame
+ * @hdr: the frame (buffer must include at least the first octet of payload)
+ */
+static inline bool ieee80211_is_robust_mgmt_frame(struct ieee80211_hdr *hdr)
+{
+	if (ieee80211_is_disassoc(hdr->frame_control) ||
+	    ieee80211_is_deauth(hdr->frame_control))
+		return true;
+
+	if (ieee80211_is_action(hdr->frame_control)) {
+		u8 *category;
+
+		/*
+		 * Action frames, excluding Public Action frames, are Robust
+		 * Management Frames. However, if we are looking at a Protected
+		 * frame, skip the check since the data may be encrypted and
+		 * the frame has already been found to be a Robust Management
+		 * Frame (by the other end).
+		 */
+		if (ieee80211_has_protected(hdr->frame_control))
+			return true;
+		category = ((u8 *) hdr) + 24;
+		return *category != WLAN_CATEGORY_PUBLIC;
+	}
+
+	return false;
+}
+
 /**
  * ieee80211_fhss_chan_to_freq - get channel frequency
  * @channel: the FHSS channel

net/mac80211/tx.c

@@ -330,6 +330,22 @@ ieee80211_tx_h_multicast_ps_buf(struct ieee80211_tx_data *tx)
 	return TX_CONTINUE;
 }
 
+static int ieee80211_use_mfp(__le16 fc, struct sta_info *sta,
+			     struct sk_buff *skb)
+{
+	if (!ieee80211_is_mgmt(fc))
+		return 0;
+
+	if (sta == NULL || !test_sta_flags(sta, WLAN_STA_MFP))
+		return 0;
+
+	if (!ieee80211_is_robust_mgmt_frame((struct ieee80211_hdr *)
+					    skb->data))
+		return 0;
+
+	return 1;
+}
+
 static ieee80211_tx_result
 ieee80211_tx_h_unicast_ps_buf(struct ieee80211_tx_data *tx)
 {
@@ -428,10 +444,15 @@ ieee80211_tx_h_select_key(struct ieee80211_tx_data *tx)
 			if (ieee80211_is_auth(hdr->frame_control))
 				break;
 		case ALG_TKIP:
-		case ALG_CCMP:
 			if (!ieee80211_is_data_present(hdr->frame_control))
 				tx->key = NULL;
 			break;
+		case ALG_CCMP:
+			if (!ieee80211_is_data_present(hdr->frame_control) &&
+			    !ieee80211_use_mfp(hdr->frame_control, tx->sta,
+					       tx->skb))
+				tx->key = NULL;
+			break;
 		}
 	}
 

net/mac80211/wpa.c

@@ -266,7 +266,7 @@ static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 				int encrypted)
 {
 	__le16 mask_fc;
-	int a4_included;
+	int a4_included, mgmt;
 	u8 qos_tid;
 	u8 *b_0, *aad;
 	u16 data_len, len_a;
@@ -277,12 +277,15 @@ static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 	aad = scratch + 4 * AES_BLOCK_LEN;
 
 	/*
-	 * Mask FC: zero subtype b4 b5 b6
+	 * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
 	 * Retry, PwrMgt, MoreData; set Protected
 	 */
+	mgmt = ieee80211_is_mgmt(hdr->frame_control);
 	mask_fc = hdr->frame_control;
-	mask_fc &= ~cpu_to_le16(0x0070 | IEEE80211_FCTL_RETRY |
+	mask_fc &= ~cpu_to_le16(IEEE80211_FCTL_RETRY |
 				IEEE80211_FCTL_PM | IEEE80211_FCTL_MOREDATA);
+	if (!mgmt)
+		mask_fc &= ~cpu_to_le16(0x0070);
 	mask_fc |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
 
 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
@@ -300,8 +303,10 @@ static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 
 	/* First block, b_0 */
 	b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
-	/* Nonce: QoS Priority | A2 | PN */
+	/* Nonce: Nonce Flags | A2 | PN
-	b_0[1] = qos_tid;
+	 * Nonce Flags: Priority (b0..b3) | Management (b4) | Reserved (b5..b7)
+	 */
+	b_0[1] = qos_tid | (mgmt << 4);
 	memcpy(&b_0[2], hdr->addr2, ETH_ALEN);
 	memcpy(&b_0[8], pn, CCMP_PN_LEN);
 	/* l(m) */
@@ -446,7 +451,8 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
 
 	hdrlen = ieee80211_hdrlen(hdr->frame_control);
 
-	if (!ieee80211_is_data(hdr->frame_control))
+	if (!ieee80211_is_data(hdr->frame_control) &&
+	    !ieee80211_is_robust_mgmt_frame(hdr))
 		return RX_CONTINUE;
 
 	data_len = skb->len - hdrlen - CCMP_HDR_LEN - CCMP_MIC_LEN;