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>

3 files changed, 64 insertions, 7 deletions

diff --git a/include/linux/ieee80211.h b/include/linux/ieee80211.h
index cade2556af0e..d5165895f316 100644
--- a/include/linux/ieee80211.h
+++ b/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,
 };
 
@@ -1186,6 +1187,35 @@ static inline u8 *ieee80211_get_DA(struct ieee80211_hdr *hdr)
 }
 
 /**
+ * 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
  *
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index cd6bc87eec73..50c6c4fabea5 100644
--- a/net/mac80211/tx.c
+++ b/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;
                 }
         }
 
diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index 7aa63caf8d50..aff46adde3f0 100644
--- a/net/mac80211/wpa.c
+++ b/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 */
-        b_0[1] = qos_tid;
+        /* Nonce: Nonce Flags | A2 | PN
+         * 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;