mac80211: port CCMP to cryptoapi's CCM driver

Use the generic CCM aead chaining mode driver rather than a local
implementation that sits right on top of the core AES cipher.

This allows the use of accelerated implementations of either
CCM as a whole or the CTR mode which it encapsulates.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 20 insertions, 24 deletions

diff --git a/net/mac80211/wpa.c b/net/mac80211/wpa.c
index c9edfcb..d657282 100644
--- a/net/mac80211/wpa.c
+++ b/net/mac80211/wpa.c
@@ -301,22 +301,16 @@ ieee80211_crypto_tkip_decrypt(struct ieee80211_rx_data *rx)
 }
 
 
-static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
+static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *b_0, u8 *aad,
 				int encrypted)
 {
 	__le16 mask_fc;
 	int a4_included, mgmt;
 	u8 qos_tid;
-	u8 *b_0, *aad;
-	u16 data_len, len_a;
+	u16 len_a;
 	unsigned int hdrlen;
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 
-	memset(scratch, 0, 6 * AES_BLOCK_SIZE);
-
-	b_0 = scratch + 3 * AES_BLOCK_SIZE;
-	aad = scratch + 4 * AES_BLOCK_SIZE;
-
 	/*
 	 * Mask FC: zero subtype b4 b5 b6 (if not mgmt)
 	 * Retry, PwrMgt, MoreData; set Protected
@@ -338,20 +332,21 @@ static void ccmp_special_blocks(struct sk_buff *skb, u8 *pn, u8 *scratch,
 	else
 		qos_tid = 0;
 
-	data_len = skb->len - hdrlen - IEEE80211_CCMP_HDR_LEN;
-	if (encrypted)
-		data_len -= IEEE80211_CCMP_MIC_LEN;
+	/* In CCM, the initial vectors (IV) used for CTR mode encryption and CBC
+	 * mode authentication are not allowed to collide, yet both are derived
+	 * from this vector b_0. We only set L := 1 here to indicate that the
+	 * data size can be represented in (L+1) bytes. The CCM layer will take
+	 * care of storing the data length in the top (L+1) bytes and setting
+	 * and clearing the other bits as is required to derive the two IVs.
+	 */
+	b_0[0] = 0x1;
 
-	/* First block, b_0 */
-	b_0[0] = 0x59; /* flags: Adata: 1, M: 011, L: 001 */
 	/* 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, IEEE80211_CCMP_PN_LEN);
-	/* l(m) */
-	put_unaligned_be16(data_len, &b_0[14]);
 
 	/* AAD (extra authenticate-only data) / masked 802.11 header
 	 * FC | A1 | A2 | A3 | SC | [A4] | [QC] */
@@ -407,7 +402,8 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 	u8 *pos;
 	u8 pn[6];
 	u64 pn64;
-	u8 scratch[6 * AES_BLOCK_SIZE];
+	u8 aad[2 * AES_BLOCK_SIZE];
+	u8 b_0[AES_BLOCK_SIZE];
 
 	if (info->control.hw_key &&
 	    !(info->control.hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) &&
@@ -460,9 +456,9 @@ static int ccmp_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 		return 0;
 
 	pos += IEEE80211_CCMP_HDR_LEN;
-	ccmp_special_blocks(skb, pn, scratch, 0);
-	ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, scratch, pos, len,
-				  pos, skb_put(skb, IEEE80211_CCMP_MIC_LEN));
+	ccmp_special_blocks(skb, pn, b_0, aad, 0);
+	ieee80211_aes_ccm_encrypt(key->u.ccmp.tfm, b_0, aad, pos, len,
+				  skb_put(skb, IEEE80211_CCMP_MIC_LEN));
 
 	return 0;
 }
@@ -525,16 +521,16 @@ ieee80211_crypto_ccmp_decrypt(struct ieee80211_rx_data *rx)
 	}
 
 	if (!(status->flag & RX_FLAG_DECRYPTED)) {
-		u8 scratch[6 * AES_BLOCK_SIZE];
+		u8 aad[2 * AES_BLOCK_SIZE];
+		u8 b_0[AES_BLOCK_SIZE];
 		/* hardware didn't decrypt/verify MIC */
-		ccmp_special_blocks(skb, pn, scratch, 1);
+		ccmp_special_blocks(skb, pn, b_0, aad, 1);
 
 		if (ieee80211_aes_ccm_decrypt(
-			    key->u.ccmp.tfm, scratch,
+			    key->u.ccmp.tfm, b_0, aad,
 			    skb->data + hdrlen + IEEE80211_CCMP_HDR_LEN,
 			    data_len,
-			    skb->data + skb->len - IEEE80211_CCMP_MIC_LEN,
-			    skb->data + hdrlen + IEEE80211_CCMP_HDR_LEN))
+			    skb->data + skb->len - IEEE80211_CCMP_MIC_LEN))
 			return RX_DROP_UNUSABLE;
 	}