net/wireless/lib80211_crypt_wep.c - maze/linux - Git at Google

 /*
  * lib80211 crypt: host-based WEP encryption implementation for lib80211
  *
  * Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi>
  * Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation. See README and COPYING for
  * more details.
  */

 #include <linux/err.h>
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/slab.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 #include <linux/skbuff.h>
 #include <linux/mm.h>
 #include <asm/string.h>

 #include <net/lib80211.h>

 #include <linux/crypto.h>
 #include <linux/crc32.h>

 MODULE_AUTHOR("Jouni Malinen");
 MODULE_DESCRIPTION("lib80211 crypt: WEP");
 MODULE_LICENSE("GPL");

 struct lib80211_wep_data {
 	u32 iv;
 #define WEP_KEY_LEN 13
 	u8 key[WEP_KEY_LEN + 1];
 	u8 key_len;
 	u8 key_idx;
 	struct crypto_blkcipher *tx_tfm;
 	struct crypto_blkcipher *rx_tfm;
 };

 static void *lib80211_wep_init(int keyidx)
 {
 	struct lib80211_wep_data *priv;

 	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
 	if (priv == NULL)
 		goto fail;
 	priv->key_idx = keyidx;

 	priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(priv->tx_tfm)) {
 		printk(KERN_DEBUG "lib80211_crypt_wep: could not allocate "
 		       "crypto API arc4\n");
 		priv->tx_tfm = NULL;
 		goto fail;
 	}

 	priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
 	if (IS_ERR(priv->rx_tfm)) {
 		printk(KERN_DEBUG "lib80211_crypt_wep: could not allocate "
 		       "crypto API arc4\n");
 		priv->rx_tfm = NULL;
 		goto fail;
 	}
 	/* start WEP IV from a random value */
 	get_random_bytes(&priv->iv, 4);

 	return priv;

       fail:
 	if (priv) {
 		if (priv->tx_tfm)
 			crypto_free_blkcipher(priv->tx_tfm);
 		if (priv->rx_tfm)
 			crypto_free_blkcipher(priv->rx_tfm);
 		kfree(priv);
 	}
 	return NULL;
 }

 static void lib80211_wep_deinit(void *priv)
 {
 	struct lib80211_wep_data *_priv = priv;
 	if (_priv) {
 		if (_priv->tx_tfm)
 			crypto_free_blkcipher(_priv->tx_tfm);
 		if (_priv->rx_tfm)
 			crypto_free_blkcipher(_priv->rx_tfm);
 	}
 	kfree(priv);
 }

 /* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
 static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len,
 			       u8 *key, int keylen, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;
 	u32 klen, len;
 	u8 *pos;

 	if (skb_headroom(skb) < 4 || skb->len < hdr_len)
 		return -1;

 	len = skb->len - hdr_len;
 	pos = skb_push(skb, 4);
 	memmove(pos, pos + 4, hdr_len);
 	pos += hdr_len;

 	klen = 3 + wep->key_len;

 	wep->iv++;

 	/* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
 	 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
 	 * can be used to speedup attacks, so avoid using them. */
 	if ((wep->iv & 0xff00) == 0xff00) {
 		u8 B = (wep->iv >> 16) & 0xff;
 		if (B >= 3 && B < klen)
 			wep->iv += 0x0100;
 	}

 	/* Prepend 24-bit IV to RC4 key and TX frame */
 	*pos++ = (wep->iv >> 16) & 0xff;
 	*pos++ = (wep->iv >> 8) & 0xff;
 	*pos++ = wep->iv & 0xff;
 	*pos++ = wep->key_idx << 6;

 	return 0;
 }

 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom
  * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
  * so the payload length increases with 8 bytes.
  *
  * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
  */
 static int lib80211_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;
 	struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
 	u32 crc, klen, len;
 	u8 *pos, *icv;
 	struct scatterlist sg;
 	u8 key[WEP_KEY_LEN + 3];

 	/* other checks are in lib80211_wep_build_iv */
 	if (skb_tailroom(skb) < 4)
 		return -1;

 	/* add the IV to the frame */
 	if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv))
 		return -1;

 	/* Copy the IV into the first 3 bytes of the key */
 	skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);

 	/* Copy rest of the WEP key (the secret part) */
 	memcpy(key + 3, wep->key, wep->key_len);

 	len = skb->len - hdr_len - 4;
 	pos = skb->data + hdr_len + 4;
 	klen = 3 + wep->key_len;

 	/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
 	crc = ~crc32_le(~0, pos, len);
 	icv = skb_put(skb, 4);
 	icv[0] = crc;
 	icv[1] = crc >> 8;
 	icv[2] = crc >> 16;
 	icv[3] = crc >> 24;

 	crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
 	sg_init_one(&sg, pos, len + 4);
 	return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
 }

 /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
  * the frame: IV (4 bytes), encrypted payload (including SNAP header),
  * ICV (4 bytes). len includes both IV and ICV.
  *
  * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
  * failure. If frame is OK, IV and ICV will be removed.
  */
 static int lib80211_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;
 	struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
 	u32 crc, klen, plen;
 	u8 key[WEP_KEY_LEN + 3];
 	u8 keyidx, *pos, icv[4];
 	struct scatterlist sg;

 	if (skb->len < hdr_len + 8)
 		return -1;

 	pos = skb->data + hdr_len;
 	key[0] = *pos++;
 	key[1] = *pos++;
 	key[2] = *pos++;
 	keyidx = *pos++ >> 6;
 	if (keyidx != wep->key_idx)
 		return -1;

 	klen = 3 + wep->key_len;

 	/* Copy rest of the WEP key (the secret part) */
 	memcpy(key + 3, wep->key, wep->key_len);

 	/* Apply RC4 to data and compute CRC32 over decrypted data */
 	plen = skb->len - hdr_len - 8;

 	crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
 	sg_init_one(&sg, pos, plen + 4);
 	if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
 		return -7;

 	crc = ~crc32_le(~0, pos, plen);
 	icv[0] = crc;
 	icv[1] = crc >> 8;
 	icv[2] = crc >> 16;
 	icv[3] = crc >> 24;
 	if (memcmp(icv, pos + plen, 4) != 0) {
 		/* ICV mismatch - drop frame */
 		return -2;
 	}

 	/* Remove IV and ICV */
 	memmove(skb->data + 4, skb->data, hdr_len);
 	skb_pull(skb, 4);
 	skb_trim(skb, skb->len - 4);

 	return 0;
 }

 static int lib80211_wep_set_key(void *key, int len, u8 * seq, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;

 	if (len < 0 || len > WEP_KEY_LEN)
 		return -1;

 	memcpy(wep->key, key, len);
 	wep->key_len = len;

 	return 0;
 }

 static int lib80211_wep_get_key(void *key, int len, u8 * seq, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;

 	if (len < wep->key_len)
 		return -1;

 	memcpy(key, wep->key, wep->key_len);

 	return wep->key_len;
 }

 static char *lib80211_wep_print_stats(char *p, void *priv)
 {
 	struct lib80211_wep_data *wep = priv;
 	p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
 	return p;
 }

 static struct lib80211_crypto_ops lib80211_crypt_wep = {
 	.name = "WEP",
 	.init = lib80211_wep_init,
 	.deinit = lib80211_wep_deinit,
 	.encrypt_mpdu = lib80211_wep_encrypt,
 	.decrypt_mpdu = lib80211_wep_decrypt,
 	.encrypt_msdu = NULL,
 	.decrypt_msdu = NULL,
 	.set_key = lib80211_wep_set_key,
 	.get_key = lib80211_wep_get_key,
 	.print_stats = lib80211_wep_print_stats,
 	.extra_mpdu_prefix_len = 4,	/* IV */
 	.extra_mpdu_postfix_len = 4,	/* ICV */
 	.owner = THIS_MODULE,
 };

 static int __init lib80211_crypto_wep_init(void)
 {
 	return lib80211_register_crypto_ops(&lib80211_crypt_wep);
 }

 static void __exit lib80211_crypto_wep_exit(void)
 {
 	lib80211_unregister_crypto_ops(&lib80211_crypt_wep);
 }

 module_init(lib80211_crypto_wep_init);
 module_exit(lib80211_crypto_wep_exit);
	/*
	* lib80211 crypt: host-based WEP encryption implementation for lib80211
	*
	* Copyright (c) 2002-2004, Jouni Malinen <j@w1.fi>
	* Copyright (c) 2008, John W. Linville <linville@tuxdriver.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License version 2 as
	* published by the Free Software Foundation. See README and COPYING for
	* more details.
	*/

	#include <linux/err.h>
	#include <linux/module.h>
	#include <linux/init.h>
	#include <linux/slab.h>
	#include <linux/random.h>
	#include <linux/scatterlist.h>
	#include <linux/skbuff.h>
	#include <linux/mm.h>
	#include <asm/string.h>

	#include <net/lib80211.h>

	#include <linux/crypto.h>
	#include <linux/crc32.h>

	MODULE_AUTHOR("Jouni Malinen");
	MODULE_DESCRIPTION("lib80211 crypt: WEP");
	MODULE_LICENSE("GPL");

	struct lib80211_wep_data {
	u32 iv;
	#define WEP_KEY_LEN 13
	u8 key[WEP_KEY_LEN + 1];
	u8 key_len;
	u8 key_idx;
	struct crypto_blkcipher *tx_tfm;
	struct crypto_blkcipher *rx_tfm;
	};

	static void *lib80211_wep_init(int keyidx)
	{
	struct lib80211_wep_data *priv;

	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
	if (priv == NULL)
	goto fail;
	priv->key_idx = keyidx;

	priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(priv->tx_tfm)) {
	printk(KERN_DEBUG "lib80211_crypt_wep: could not allocate "
	"crypto API arc4\n");
	priv->tx_tfm = NULL;
	goto fail;
	}

	priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
	if (IS_ERR(priv->rx_tfm)) {
	printk(KERN_DEBUG "lib80211_crypt_wep: could not allocate "
	"crypto API arc4\n");
	priv->rx_tfm = NULL;
	goto fail;
	}
	/* start WEP IV from a random value */
	get_random_bytes(&priv->iv, 4);

	return priv;

	fail:
	if (priv) {
	if (priv->tx_tfm)
	crypto_free_blkcipher(priv->tx_tfm);
	if (priv->rx_tfm)
	crypto_free_blkcipher(priv->rx_tfm);
	kfree(priv);
	}
	return NULL;
	}

	static void lib80211_wep_deinit(void *priv)
	{
	struct lib80211_wep_data *_priv = priv;
	if (_priv) {
	if (_priv->tx_tfm)
	crypto_free_blkcipher(_priv->tx_tfm);
	if (_priv->rx_tfm)
	crypto_free_blkcipher(_priv->rx_tfm);
	}
	kfree(priv);
	}

	/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
	static int lib80211_wep_build_iv(struct sk_buff *skb, int hdr_len,
	u8 key, int keylen, void priv)
	{
	struct lib80211_wep_data *wep = priv;
	u32 klen, len;
	u8 *pos;

	if (skb_headroom(skb) < 4 \|\| skb->len < hdr_len)
	return -1;

	len = skb->len - hdr_len;
	pos = skb_push(skb, 4);
	memmove(pos, pos + 4, hdr_len);
	pos += hdr_len;

	klen = 3 + wep->key_len;

	wep->iv++;

	/* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
	* scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
	* can be used to speedup attacks, so avoid using them. */
	if ((wep->iv & 0xff00) == 0xff00) {
	u8 B = (wep->iv >> 16) & 0xff;
	if (B >= 3 && B < klen)
	wep->iv += 0x0100;
	}

	/* Prepend 24-bit IV to RC4 key and TX frame */
	*pos++ = (wep->iv >> 16) & 0xff;
	*pos++ = (wep->iv >> 8) & 0xff;
	*pos++ = wep->iv & 0xff;
	*pos++ = wep->key_idx << 6;

	return 0;
	}

	/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
	* for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
	* so the payload length increases with 8 bytes.
	*
	* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
	*/
	static int lib80211_wep_encrypt(struct sk_buff skb, int hdr_len, void priv)
	{
	struct lib80211_wep_data *wep = priv;
	struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
	u32 crc, klen, len;
	u8 pos, icv;
	struct scatterlist sg;
	u8 key[WEP_KEY_LEN + 3];

	/* other checks are in lib80211_wep_build_iv */
	if (skb_tailroom(skb) < 4)
	return -1;

	/* add the IV to the frame */
	if (lib80211_wep_build_iv(skb, hdr_len, NULL, 0, priv))
	return -1;

	/* Copy the IV into the first 3 bytes of the key */
	skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);

	/* Copy rest of the WEP key (the secret part) */
	memcpy(key + 3, wep->key, wep->key_len);

	len = skb->len - hdr_len - 4;
	pos = skb->data + hdr_len + 4;
	klen = 3 + wep->key_len;

	/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
	crc = ~crc32_le(~0, pos, len);
	icv = skb_put(skb, 4);
	icv[0] = crc;
	icv[1] = crc >> 8;
	icv[2] = crc >> 16;
	icv[3] = crc >> 24;

	crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
	sg_init_one(&sg, pos, len + 4);
	return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
	}

	/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
	* the frame: IV (4 bytes), encrypted payload (including SNAP header),
	* ICV (4 bytes). len includes both IV and ICV.
	*
	* Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
	* failure. If frame is OK, IV and ICV will be removed.
	*/
	static int lib80211_wep_decrypt(struct sk_buff skb, int hdr_len, void priv)
	{
	struct lib80211_wep_data *wep = priv;
	struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
	u32 crc, klen, plen;
	u8 key[WEP_KEY_LEN + 3];
	u8 keyidx, *pos, icv[4];
	struct scatterlist sg;

	if (skb->len < hdr_len + 8)
	return -1;

	pos = skb->data + hdr_len;
	key[0] = *pos++;
	key[1] = *pos++;
	key[2] = *pos++;
	keyidx = *pos++ >> 6;
	if (keyidx != wep->key_idx)
	return -1;

	klen = 3 + wep->key_len;

	/* Copy rest of the WEP key (the secret part) */
	memcpy(key + 3, wep->key, wep->key_len);

	/* Apply RC4 to data and compute CRC32 over decrypted data */
	plen = skb->len - hdr_len - 8;

	crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
	sg_init_one(&sg, pos, plen + 4);
	if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
	return -7;

	crc = ~crc32_le(~0, pos, plen);
	icv[0] = crc;
	icv[1] = crc >> 8;
	icv[2] = crc >> 16;
	icv[3] = crc >> 24;
	if (memcmp(icv, pos + plen, 4) != 0) {
	/* ICV mismatch - drop frame */
	return -2;
	}

	/* Remove IV and ICV */
	memmove(skb->data + 4, skb->data, hdr_len);
	skb_pull(skb, 4);
	skb_trim(skb, skb->len - 4);

	return 0;
	}

	static int lib80211_wep_set_key(void key, int len, u8 seq, void *priv)
	{
	struct lib80211_wep_data *wep = priv;

	if (len < 0 \|\| len > WEP_KEY_LEN)
	return -1;

	memcpy(wep->key, key, len);
	wep->key_len = len;

	return 0;
	}

	static int lib80211_wep_get_key(void key, int len, u8 seq, void *priv)
	{
	struct lib80211_wep_data *wep = priv;

	if (len < wep->key_len)
	return -1;

	memcpy(key, wep->key, wep->key_len);

	return wep->key_len;
	}

	static char lib80211_wep_print_stats(char p, void *priv)
	{
	struct lib80211_wep_data *wep = priv;
	p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
	return p;
	}

	static struct lib80211_crypto_ops lib80211_crypt_wep = {
	.name = "WEP",
	.init = lib80211_wep_init,
	.deinit = lib80211_wep_deinit,
	.encrypt_mpdu = lib80211_wep_encrypt,
	.decrypt_mpdu = lib80211_wep_decrypt,
	.encrypt_msdu = NULL,
	.decrypt_msdu = NULL,
	.set_key = lib80211_wep_set_key,
	.get_key = lib80211_wep_get_key,
	.print_stats = lib80211_wep_print_stats,
	.extra_mpdu_prefix_len = 4, /* IV */
	.extra_mpdu_postfix_len = 4, /* ICV */
	.owner = THIS_MODULE,
	};

	static int __init lib80211_crypto_wep_init(void)
	{
	return lib80211_register_crypto_ops(&lib80211_crypt_wep);
	}

	static void __exit lib80211_crypto_wep_exit(void)
	{
	lib80211_unregister_crypto_ops(&lib80211_crypt_wep);
	}

	module_init(lib80211_crypto_wep_init);
	module_exit(lib80211_crypto_wep_exit);