[RFC PATCH 3/3] lib80211/wep: switch to skcipher interface for arc4

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

The WEP code uses the arc4 cipher interface, and invokes it byte by
byte. This is rather inefficient, and since the cipher interface in
general is not really suitable for use outside of the crypto subsystem,
move this code to use the skcipher interface instead.

Given that the only driver that provides a RC4 cipher also provides
a skcipher implementation, this is guaranteed to work. (Note that
ARC4_BLOCK_SIZE is #define'd as 1 so ecb(arc4) behaves as a stream
cipher, as is required in this case)

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 net/wireless/lib80211_crypt_wep.c | 52 ++++++++++++++------
 1 file changed, 36 insertions(+), 16 deletions(-)

diff --git a/net/wireless/lib80211_crypt_wep.c b/net/wireless/lib80211_crypt_wep.c
index 20c1ad63ad44..461f94afe6e9 100644
--- a/net/wireless/lib80211_crypt_wep.c
+++ b/net/wireless/lib80211_crypt_wep.c
@@ -23,6 +23,7 @@
 #include <net/lib80211.h>
 
 #include <linux/crypto.h>
+#include <crypto/skcipher.h>
 #include <linux/crc32.h>
 
 MODULE_AUTHOR("Jouni Malinen");
@@ -35,8 +36,10 @@ struct lib80211_wep_data {
 	u8 key[WEP_KEY_LEN + 1];
 	u8 key_len;
 	u8 key_idx;
-	struct crypto_cipher *tx_tfm;
-	struct crypto_cipher *rx_tfm;
+	struct crypto_skcipher *tx_tfm;
+	struct crypto_skcipher *rx_tfm;
+	struct skcipher_request *tx_req;
+	struct skcipher_request *rx_req;
 };
 
 static void *lib80211_wep_init(int keyidx)
@@ -48,17 +51,26 @@ static void *lib80211_wep_init(int keyidx)
 		goto fail;
 	priv->key_idx = keyidx;
 
-	priv->tx_tfm = crypto_alloc_cipher("arc4", 0, 0);
+	priv->tx_tfm = crypto_alloc_skcipher("ecb(arc4)", 0, 0);
 	if (IS_ERR(priv->tx_tfm)) {
 		priv->tx_tfm = NULL;
 		goto fail;
 	}
 
-	priv->rx_tfm = crypto_alloc_cipher("arc4", 0, 0);
+	priv->rx_tfm = crypto_alloc_skcipher("arc4", 0, 0);
 	if (IS_ERR(priv->rx_tfm)) {
 		priv->rx_tfm = NULL;
 		goto fail;
 	}
+
+	priv->tx_req = skcipher_request_alloc(priv->tx_tfm, GFP_KERNEL);
+	if (!priv->tx_req)
+		goto fail;
+
+	priv->rx_req = skcipher_request_alloc(priv->rx_tfm, GFP_KERNEL);
+	if (!priv->tx_req)
+		goto fail;
+
 	/* start WEP IV from a random value */
 	get_random_bytes(&priv->iv, 4);
 
@@ -66,8 +78,10 @@ static void *lib80211_wep_init(int keyidx)
 
       fail:
 	if (priv) {
-		crypto_free_cipher(priv->tx_tfm);
-		crypto_free_cipher(priv->rx_tfm);
+		skcipher_request_free(priv->tx_req);
+		skcipher_request_free(priv->rx_req);
+		crypto_free_skcipher(priv->tx_tfm);
+		crypto_free_skcipher(priv->rx_tfm);
 		kfree(priv);
 	}
 	return NULL;
@@ -77,8 +91,10 @@ static void lib80211_wep_deinit(void *priv)
 {
 	struct lib80211_wep_data *_priv = priv;
 	if (_priv) {
-		crypto_free_cipher(_priv->tx_tfm);
-		crypto_free_cipher(_priv->rx_tfm);
+		skcipher_request_free(_priv->tx_req);
+		skcipher_request_free(_priv->rx_req);
+		crypto_free_skcipher(_priv->tx_tfm);
+		crypto_free_skcipher(_priv->rx_tfm);
 	}
 	kfree(priv);
 }
@@ -129,10 +145,10 @@ static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len,
 static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;
+	struct scatterlist sg;
 	u32 crc, klen, len;
 	u8 *pos, *icv;
 	u8 key[WEP_KEY_LEN + 3];
-	int i;
 
 	/* other checks are in lib80211_wep_build_iv */
 	if (skb_tailroom(skb) < 4)
@@ -160,10 +176,11 @@ static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 	icv[2] = crc >> 16;
 	icv[3] = crc >> 24;
 
-	crypto_cipher_setkey(wep->tx_tfm, key, klen);
-
-	for (i = 0; i < len + 4; i++)
-		crypto_cipher_encrypt_one(wep->tx_tfm, pos + i, pos + i);
+	crypto_skcipher_setkey(wep->tx_tfm, key, klen);
+	sg_init_one(&sg, pos, len + 4);
+	skcipher_request_set_crypt(wep->tx_req, &sg, &sg, len + 4, NULL);
+	if (crypto_skcipher_encrypt(wep->tx_req) < 0)
+		return -1;
 
 	return 0;
 }
@@ -178,6 +195,7 @@ static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;
+	struct scatterlist sg;
 	u32 crc, klen, plen;
 	u8 key[WEP_KEY_LEN + 3];
 	u8 keyidx, *pos, icv[4];
@@ -202,9 +220,11 @@ static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 	/* Apply RC4 to data and compute CRC32 over decrypted data */
 	plen = skb->len - hdr_len - 8;
 
-	crypto_cipher_setkey(wep->rx_tfm, key, klen);
-	for (i = 0; i < plen + 4; i++)
-		crypto_cipher_decrypt_one(wep->rx_tfm, pos + i, pos + i);
+	crypto_skcipher_setkey(wep->rx_tfm, key, klen);
+	sg_init_one(&sg, pos, plen + 4);
+	skcipher_request_set_crypt(wep->rx_req, &sg, &sg, plen + 4, NULL);
+	if (crypto_skcipher_decrypt(wep->rx_req) < 0)
+		return -1;
 
 	crc = ~crc32_le(~0, pos, plen);
 	icv[0] = crc;
-- 
2.20.1