[linux.git] / net / ieee80211 / ieee80211_crypt_wep.c

/*
 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
 *
 * Copyright (c) 2002-2004, Jouni Malinen <[email protected]>
 *
 * 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/skbuff.h>
#include <linux/mm.h>
#include <asm/string.h>

#include <net/ieee80211.h>

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

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

struct prism2_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 *prism2_wep_init(int keyidx)
{
	struct prism2_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 "ieee80211_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 "ieee80211_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 prism2_wep_deinit(void *priv)
{
	struct prism2_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 prism2_wep_build_iv(struct sk_buff *skb, int hdr_len,
			       u8 *key, int keylen, void *priv)
{
	struct prism2_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 prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct prism2_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 prism2_wep_build_iv */
	if (skb_tailroom(skb) < 4)
		return -1;

	/* add the IV to the frame */
	if (prism2_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.page = virt_to_page(pos);
	sg.offset = offset_in_page(pos);
	sg.length = 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 prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
{
	struct prism2_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.page = virt_to_page(pos);
	sg.offset = offset_in_page(pos);
	sg.length = 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 prism2_wep_set_key(void *key, int len, u8 * seq, void *priv)
{
	struct prism2_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 prism2_wep_get_key(void *key, int len, u8 * seq, void *priv)
{
	struct prism2_wep_data *wep = priv;

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

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

	return wep->key_len;
}

static char *prism2_wep_print_stats(char *p, void *priv)
{
	struct prism2_wep_data *wep = priv;
	p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
	return p;
}

static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
	.name = "WEP",
	.init = prism2_wep_init,
	.deinit = prism2_wep_deinit,
	.build_iv = prism2_wep_build_iv,
	.encrypt_mpdu = prism2_wep_encrypt,
	.decrypt_mpdu = prism2_wep_decrypt,
	.encrypt_msdu = NULL,
	.decrypt_msdu = NULL,
	.set_key = prism2_wep_set_key,
	.get_key = prism2_wep_get_key,
	.print_stats = prism2_wep_print_stats,
	.extra_mpdu_prefix_len = 4,	/* IV */
	.extra_mpdu_postfix_len = 4,	/* ICV */
	.owner = THIS_MODULE,
};

static int __init ieee80211_crypto_wep_init(void)
{
	return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
}

static void __exit ieee80211_crypto_wep_exit(void)
{
	ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
}

module_init(ieee80211_crypto_wep_init);
module_exit(ieee80211_crypto_wep_exit);
Commit	Line	Data
b453872c JG	1	/*
	2	* Host AP crypt: host-based WEP encryption implementation for Host AP driver
	3	*
85d32e7b	4	* Copyright (c) 2002-2004, Jouni Malinen <[email protected]>
b453872c JG	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License version 2 as
	8	* published by the Free Software Foundation. See README and COPYING for
	9	* more details.
	10	*/
	11
f12cc209	12	#include <linux/err.h>
b453872c JG	13	#include <linux/module.h>
	14	#include <linux/init.h>
	15	#include <linux/slab.h>
	16	#include <linux/random.h>
	17	#include <linux/skbuff.h>
d7fe0f24	18	#include <linux/mm.h>
b453872c JG	19	#include <asm/string.h>
	20
	21	#include <net/ieee80211.h>
	22
b453872c JG	23	#include <linux/crypto.h>
	24	#include <asm/scatterlist.h>
	25	#include <linux/crc32.h>
	26
	27	MODULE_AUTHOR("Jouni Malinen");
	28	MODULE_DESCRIPTION("Host AP crypt: WEP");
	29	MODULE_LICENSE("GPL");
	30
b453872c JG	31	struct prism2_wep_data {
	32	u32 iv;
	33	#define WEP_KEY_LEN 13
	34	u8 key[WEP_KEY_LEN + 1];
	35	u8 key_len;
	36	u8 key_idx;
28eb177d JG	37	struct crypto_blkcipher *tx_tfm;
28eb177d JG	38	struct crypto_blkcipher *rx_tfm;
b453872c JG	39	};
b453872c JG	40
6eb6edf0	41	static void *prism2_wep_init(int keyidx)
b453872c JG	42	{
	43	struct prism2_wep_data *priv;
	44
0da974f4	45	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
b453872c JG	46	if (priv == NULL)
b453872c JG	47	goto fail;
b453872c JG	48	priv->key_idx = keyidx;
b453872c JG	49
28eb177d JG	50	priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
28eb177d JG	51	if (IS_ERR(priv->tx_tfm)) {
b453872c JG	52	printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
b453872c JG	53	"crypto API arc4\n");
18379879	54	priv->tx_tfm = NULL;
b453872c JG	55	goto fail;
	56	}
	57
28eb177d JG	58	priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
28eb177d JG	59	if (IS_ERR(priv->rx_tfm)) {
5a656949 ZY	60	printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
5a656949 ZY	61	"crypto API arc4\n");
18379879	62	priv->rx_tfm = NULL;
5a656949 ZY	63	goto fail;
5a656949 ZY	64	}
b453872c JG	65	/* start WEP IV from a random value */
	66	get_random_bytes(&priv->iv, 4);
	67
	68	return priv;
	69
0edd5b44	70	fail:
b453872c	71	if (priv) {
5a656949	72	if (priv->tx_tfm)
28eb177d	73	crypto_free_blkcipher(priv->tx_tfm);
5a656949	74	if (priv->rx_tfm)
28eb177d	75	crypto_free_blkcipher(priv->rx_tfm);
b453872c JG	76	kfree(priv);
	77	}
	78	return NULL;
	79	}
	80
b453872c JG	81	static void prism2_wep_deinit(void *priv)
	82	{
	83	struct prism2_wep_data *_priv = priv;
5a656949 ZY	84	if (_priv) {
5a656949 ZY	85	if (_priv->tx_tfm)
28eb177d	86	crypto_free_blkcipher(_priv->tx_tfm);
5a656949	87	if (_priv->rx_tfm)
28eb177d	88	crypto_free_blkcipher(_priv->rx_tfm);
5a656949	89	}
b453872c JG	90	kfree(priv);
	91	}
	92
a4bf26f3	93	/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
9184d934 ZY	94	static int prism2_wep_build_iv(struct sk_buff *skb, int hdr_len,
9184d934 ZY	95	u8 key, int keylen, void priv)
b453872c JG	96	{
b453872c JG	97	struct prism2_wep_data *wep = priv;
a4bf26f3 JB	98	u32 klen, len;
a4bf26f3 JB	99	u8 *pos;
64265651	100
a4bf26f3	101	if (skb_headroom(skb) < 4 \|\| skb->len < hdr_len)
b453872c JG	102	return -1;
	103
	104	len = skb->len - hdr_len;
	105	pos = skb_push(skb, 4);
	106	memmove(pos, pos + 4, hdr_len);
	107	pos += hdr_len;
	108
	109	klen = 3 + wep->key_len;
	110
	111	wep->iv++;
	112
	113	/* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
	114	* scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
	115	* can be used to speedup attacks, so avoid using them. */
	116	if ((wep->iv & 0xff00) == 0xff00) {
	117	u8 B = (wep->iv >> 16) & 0xff;
	118	if (B >= 3 && B < klen)
	119	wep->iv += 0x0100;
	120	}
	121
	122	/* Prepend 24-bit IV to RC4 key and TX frame */
a4bf26f3 JB	123	*pos++ = (wep->iv >> 16) & 0xff;
	124	*pos++ = (wep->iv >> 8) & 0xff;
	125	*pos++ = wep->iv & 0xff;
b453872c JG	126	*pos++ = wep->key_idx << 6;
b453872c JG	127
a4bf26f3 JB	128	return 0;
	129	}
	130
	131	/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
	132	* for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
	133	* so the payload length increases with 8 bytes.
	134	*
	135	* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
	136	*/
	137	static int prism2_wep_encrypt(struct sk_buff skb, int hdr_len, void priv)
	138	{
	139	struct prism2_wep_data *wep = priv;
28eb177d	140	struct blkcipher_desc desc = { .tfm = wep->tx_tfm };
a4bf26f3 JB	141	u32 crc, klen, len;
	142	u8 pos, icv;
	143	struct scatterlist sg;
	144	u8 key[WEP_KEY_LEN + 3];
	145
	146	/* other checks are in prism2_wep_build_iv */
	147	if (skb_tailroom(skb) < 4)
	148	return -1;
64265651	149
a4bf26f3	150	/* add the IV to the frame */
9184d934	151	if (prism2_wep_build_iv(skb, hdr_len, NULL, 0, priv))
a4bf26f3	152	return -1;
64265651	153
a4bf26f3	154	/* Copy the IV into the first 3 bytes of the key */
d626f62b	155	skb_copy_from_linear_data_offset(skb, hdr_len, key, 3);
a4bf26f3	156
b453872c JG	157	/* Copy rest of the WEP key (the secret part) */
b453872c JG	158	memcpy(key + 3, wep->key, wep->key_len);
64265651	159
a4bf26f3 JB	160	len = skb->len - hdr_len - 4;
	161	pos = skb->data + hdr_len + 4;
	162	klen = 3 + wep->key_len;
b453872c	163
a4bf26f3	164	/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
b453872c JG	165	crc = ~crc32_le(~0, pos, len);
	166	icv = skb_put(skb, 4);
	167	icv[0] = crc;
	168	icv[1] = crc >> 8;
	169	icv[2] = crc >> 16;
	170	icv[3] = crc >> 24;
	171
28eb177d	172	crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
b453872c JG	173	sg.page = virt_to_page(pos);
	174	sg.offset = offset_in_page(pos);
	175	sg.length = len + 4;
f12cc209	176	return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
b453872c JG	177	}
b453872c JG	178
b453872c JG	179	/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
	180	* the frame: IV (4 bytes), encrypted payload (including SNAP header),
	181	* ICV (4 bytes). len includes both IV and ICV.
	182	*
	183	* Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
	184	* failure. If frame is OK, IV and ICV will be removed.
	185	*/
	186	static int prism2_wep_decrypt(struct sk_buff skb, int hdr_len, void priv)
	187	{
	188	struct prism2_wep_data *wep = priv;
28eb177d	189	struct blkcipher_desc desc = { .tfm = wep->rx_tfm };
b453872c JG	190	u32 crc, klen, plen;
	191	u8 key[WEP_KEY_LEN + 3];
	192	u8 keyidx, *pos, icv[4];
	193	struct scatterlist sg;
	194
	195	if (skb->len < hdr_len + 8)
	196	return -1;
	197
	198	pos = skb->data + hdr_len;
	199	key[0] = *pos++;
	200	key[1] = *pos++;
	201	key[2] = *pos++;
	202	keyidx = *pos++ >> 6;
	203	if (keyidx != wep->key_idx)
	204	return -1;
	205
	206	klen = 3 + wep->key_len;
	207
	208	/* Copy rest of the WEP key (the secret part) */
	209	memcpy(key + 3, wep->key, wep->key_len);
	210
	211	/* Apply RC4 to data and compute CRC32 over decrypted data */
	212	plen = skb->len - hdr_len - 8;
	213
28eb177d	214	crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
b453872c JG	215	sg.page = virt_to_page(pos);
	216	sg.offset = offset_in_page(pos);
	217	sg.length = plen + 4;
f12cc209 HX	218	if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
f12cc209 HX	219	return -7;
b453872c JG	220
	221	crc = ~crc32_le(~0, pos, plen);
	222	icv[0] = crc;
	223	icv[1] = crc >> 8;
	224	icv[2] = crc >> 16;
	225	icv[3] = crc >> 24;
	226	if (memcmp(icv, pos + plen, 4) != 0) {
	227	/* ICV mismatch - drop frame */
	228	return -2;
	229	}
	230
	231	/* Remove IV and ICV */
	232	memmove(skb->data + 4, skb->data, hdr_len);
	233	skb_pull(skb, 4);
	234	skb_trim(skb, skb->len - 4);
	235
	236	return 0;
	237	}
	238
0edd5b44	239	static int prism2_wep_set_key(void key, int len, u8 seq, void *priv)
b453872c JG	240	{
	241	struct prism2_wep_data *wep = priv;
	242
	243	if (len < 0 \|\| len > WEP_KEY_LEN)
	244	return -1;
	245
	246	memcpy(wep->key, key, len);
	247	wep->key_len = len;
	248
	249	return 0;
	250	}
	251
0edd5b44	252	static int prism2_wep_get_key(void key, int len, u8 seq, void *priv)
b453872c JG	253	{
	254	struct prism2_wep_data *wep = priv;
	255
	256	if (len < wep->key_len)
	257	return -1;
	258
	259	memcpy(key, wep->key, wep->key_len);
	260
	261	return wep->key_len;
	262	}
	263
0edd5b44	264	static char prism2_wep_print_stats(char p, void *priv)
b453872c JG	265	{
b453872c JG	266	struct prism2_wep_data *wep = priv;
0edd5b44	267	p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
b453872c JG	268	return p;
	269	}
	270
b453872c	271	static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
74079fdc JK	272	.name = "WEP",
	273	.init = prism2_wep_init,
	274	.deinit = prism2_wep_deinit,
a4bf26f3	275	.build_iv = prism2_wep_build_iv,
74079fdc JK	276	.encrypt_mpdu = prism2_wep_encrypt,
	277	.decrypt_mpdu = prism2_wep_decrypt,
	278	.encrypt_msdu = NULL,
	279	.decrypt_msdu = NULL,
	280	.set_key = prism2_wep_set_key,
	281	.get_key = prism2_wep_get_key,
	282	.print_stats = prism2_wep_print_stats,
1264fc04 JK	283	.extra_mpdu_prefix_len = 4, /* IV */
1264fc04 JK	284	.extra_mpdu_postfix_len = 4, /* ICV */
74079fdc	285	.owner = THIS_MODULE,
b453872c JG	286	};
b453872c JG	287
b453872c JG	288	static int __init ieee80211_crypto_wep_init(void)
	289	{
	290	return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
	291	}
	292
b453872c JG	293	static void __exit ieee80211_crypto_wep_exit(void)
	294	{
	295	ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
	296	}
	297
b453872c JG	298	module_init(ieee80211_crypto_wep_init);
b453872c JG	299	module_exit(ieee80211_crypto_wep_exit);