[deliverable/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 <jkmaline@cc.hut.fi>
 *
 * 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/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/random.h>
#include <linux/skbuff.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_tfm *tfm;
};

static void *prism2_wep_init(int keyidx)
{
	struct prism2_wep_data *priv;

	priv = kmalloc(sizeof(*priv), GFP_ATOMIC);
	if (priv == NULL)
		goto fail;
	memset(priv, 0, sizeof(*priv));
	priv->key_idx = keyidx;

	priv->tfm = crypto_alloc_tfm("arc4", 0);
	if (priv->tfm == NULL) {
		printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
		       "crypto API arc4\n");
		goto fail;
	}

	/* start WEP IV from a random value */
	get_random_bytes(&priv->iv, 4);

	return priv;

      fail:
	if (priv) {
		if (priv->tfm)
			crypto_free_tfm(priv->tfm);
		kfree(priv);
	}
	return NULL;
}

static void prism2_wep_deinit(void *priv)
{
	struct prism2_wep_data *_priv = priv;
	if (_priv && _priv->tfm)
		crypto_free_tfm(_priv->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;
	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 */
	memcpy(key, skb->data + hdr_len, 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_cipher_setkey(wep->tfm, key, klen);
	sg.page = virt_to_page(pos);
	sg.offset = offset_in_page(pos);
	sg.length = len + 4;
	crypto_cipher_encrypt(wep->tfm, &sg, &sg, len + 4);

	return 0;
}

/* 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;
	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_cipher_setkey(wep->tfm, key, klen);
	sg.page = virt_to_page(pos);
	sg.offset = offset_in_page(pos);
	sg.length = plen + 4;
	crypto_cipher_decrypt(wep->tfm, &sg, &sg, plen + 4);

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