[linux-2.6-block.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 = kzalloc(sizeof(*priv), GFP_ATOMIC);
	if (priv == NULL)
		goto fail;
	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
0da974f4	42	priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
b453872c JG	43	if (priv == NULL)
b453872c JG	44	goto fail;
b453872c JG	45	priv->key_idx = keyidx;
	46
	47	priv->tfm = crypto_alloc_tfm("arc4", 0);
	48	if (priv->tfm == NULL) {
	49	printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
	50	"crypto API arc4\n");
	51	goto fail;
	52	}
	53
	54	/* start WEP IV from a random value */
	55	get_random_bytes(&priv->iv, 4);
	56
	57	return priv;
	58
0edd5b44	59	fail:
b453872c JG	60	if (priv) {
	61	if (priv->tfm)
	62	crypto_free_tfm(priv->tfm);
	63	kfree(priv);
	64	}
	65	return NULL;
	66	}
	67
b453872c JG	68	static void prism2_wep_deinit(void *priv)
	69	{
	70	struct prism2_wep_data *_priv = priv;
	71	if (_priv && _priv->tfm)
	72	crypto_free_tfm(_priv->tfm);
	73	kfree(priv);
	74	}
	75
a4bf26f3	76	/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
9184d934 ZY	77	static int prism2_wep_build_iv(struct sk_buff *skb, int hdr_len,
9184d934 ZY	78	u8 key, int keylen, void priv)
b453872c JG	79	{
b453872c JG	80	struct prism2_wep_data *wep = priv;
a4bf26f3 JB	81	u32 klen, len;
	82	u8 *pos;
	83
	84	if (skb_headroom(skb) < 4 \|\| skb->len < hdr_len)
b453872c JG	85	return -1;
	86
	87	len = skb->len - hdr_len;
	88	pos = skb_push(skb, 4);
	89	memmove(pos, pos + 4, hdr_len);
	90	pos += hdr_len;
	91
	92	klen = 3 + wep->key_len;
	93
	94	wep->iv++;
	95
	96	/* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
	97	* scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
	98	* can be used to speedup attacks, so avoid using them. */
	99	if ((wep->iv & 0xff00) == 0xff00) {
	100	u8 B = (wep->iv >> 16) & 0xff;
	101	if (B >= 3 && B < klen)
	102	wep->iv += 0x0100;
	103	}
	104
	105	/* Prepend 24-bit IV to RC4 key and TX frame */
a4bf26f3 JB	106	*pos++ = (wep->iv >> 16) & 0xff;
	107	*pos++ = (wep->iv >> 8) & 0xff;
	108	*pos++ = wep->iv & 0xff;
b453872c JG	109	*pos++ = wep->key_idx << 6;
b453872c JG	110
a4bf26f3 JB	111	return 0;
	112	}
	113
	114	/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
	115	* for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
	116	* so the payload length increases with 8 bytes.
	117	*
	118	* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
	119	*/
	120	static int prism2_wep_encrypt(struct sk_buff skb, int hdr_len, void priv)
	121	{
	122	struct prism2_wep_data *wep = priv;
	123	u32 crc, klen, len;
	124	u8 pos, icv;
	125	struct scatterlist sg;
	126	u8 key[WEP_KEY_LEN + 3];
	127
	128	/* other checks are in prism2_wep_build_iv */
	129	if (skb_tailroom(skb) < 4)
	130	return -1;
	131
	132	/* add the IV to the frame */
9184d934	133	if (prism2_wep_build_iv(skb, hdr_len, NULL, 0, priv))
a4bf26f3 JB	134	return -1;
	135
	136	/* Copy the IV into the first 3 bytes of the key */
	137	memcpy(key, skb->data + hdr_len, 3);
	138
b453872c JG	139	/* Copy rest of the WEP key (the secret part) */
b453872c JG	140	memcpy(key + 3, wep->key, wep->key_len);
a4bf26f3 JB	141
	142	len = skb->len - hdr_len - 4;
	143	pos = skb->data + hdr_len + 4;
	144	klen = 3 + wep->key_len;
b453872c	145
a4bf26f3	146	/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
b453872c JG	147	crc = ~crc32_le(~0, pos, len);
	148	icv = skb_put(skb, 4);
	149	icv[0] = crc;
	150	icv[1] = crc >> 8;
	151	icv[2] = crc >> 16;
	152	icv[3] = crc >> 24;
	153
	154	crypto_cipher_setkey(wep->tfm, key, klen);
	155	sg.page = virt_to_page(pos);
	156	sg.offset = offset_in_page(pos);
	157	sg.length = len + 4;
	158	crypto_cipher_encrypt(wep->tfm, &sg, &sg, len + 4);
	159
	160	return 0;
	161	}
	162
b453872c JG	163	/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
	164	* the frame: IV (4 bytes), encrypted payload (including SNAP header),
	165	* ICV (4 bytes). len includes both IV and ICV.
	166	*
	167	* Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
	168	* failure. If frame is OK, IV and ICV will be removed.
	169	*/
	170	static int prism2_wep_decrypt(struct sk_buff skb, int hdr_len, void priv)
	171	{
	172	struct prism2_wep_data *wep = priv;
	173	u32 crc, klen, plen;
	174	u8 key[WEP_KEY_LEN + 3];
	175	u8 keyidx, *pos, icv[4];
	176	struct scatterlist sg;
	177
	178	if (skb->len < hdr_len + 8)
	179	return -1;
	180
	181	pos = skb->data + hdr_len;
	182	key[0] = *pos++;
	183	key[1] = *pos++;
	184	key[2] = *pos++;
	185	keyidx = *pos++ >> 6;
	186	if (keyidx != wep->key_idx)
	187	return -1;
	188
	189	klen = 3 + wep->key_len;
	190
	191	/* Copy rest of the WEP key (the secret part) */
	192	memcpy(key + 3, wep->key, wep->key_len);
	193
	194	/* Apply RC4 to data and compute CRC32 over decrypted data */
	195	plen = skb->len - hdr_len - 8;
	196
	197	crypto_cipher_setkey(wep->tfm, key, klen);
	198	sg.page = virt_to_page(pos);
	199	sg.offset = offset_in_page(pos);
	200	sg.length = plen + 4;
	201	crypto_cipher_decrypt(wep->tfm, &sg, &sg, plen + 4);
	202
	203	crc = ~crc32_le(~0, pos, plen);
	204	icv[0] = crc;
	205	icv[1] = crc >> 8;
	206	icv[2] = crc >> 16;
	207	icv[3] = crc >> 24;
	208	if (memcmp(icv, pos + plen, 4) != 0) {
	209	/* ICV mismatch - drop frame */
	210	return -2;
	211	}
	212
	213	/* Remove IV and ICV */
	214	memmove(skb->data + 4, skb->data, hdr_len);
	215	skb_pull(skb, 4);
	216	skb_trim(skb, skb->len - 4);
	217
	218	return 0;
	219	}
	220
0edd5b44	221	static int prism2_wep_set_key(void key, int len, u8 seq, void *priv)
b453872c JG	222	{
	223	struct prism2_wep_data *wep = priv;
	224
	225	if (len < 0 \|\| len > WEP_KEY_LEN)
	226	return -1;
	227
	228	memcpy(wep->key, key, len);
	229	wep->key_len = len;
	230
	231	return 0;
	232	}
	233
0edd5b44	234	static int prism2_wep_get_key(void key, int len, u8 seq, void *priv)
b453872c JG	235	{
	236	struct prism2_wep_data *wep = priv;
	237
	238	if (len < wep->key_len)
	239	return -1;
	240
	241	memcpy(key, wep->key, wep->key_len);
	242
	243	return wep->key_len;
	244	}
	245
0edd5b44	246	static char prism2_wep_print_stats(char p, void *priv)
b453872c JG	247	{
b453872c JG	248	struct prism2_wep_data *wep = priv;
0edd5b44	249	p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
b453872c JG	250	return p;
	251	}
	252
b453872c	253	static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
74079fdc JK	254	.name = "WEP",
	255	.init = prism2_wep_init,
	256	.deinit = prism2_wep_deinit,
a4bf26f3	257	.build_iv = prism2_wep_build_iv,
74079fdc JK	258	.encrypt_mpdu = prism2_wep_encrypt,
	259	.decrypt_mpdu = prism2_wep_decrypt,
	260	.encrypt_msdu = NULL,
	261	.decrypt_msdu = NULL,
	262	.set_key = prism2_wep_set_key,
	263	.get_key = prism2_wep_get_key,
	264	.print_stats = prism2_wep_print_stats,
1264fc04 JK	265	.extra_mpdu_prefix_len = 4, /* IV */
1264fc04 JK	266	.extra_mpdu_postfix_len = 4, /* ICV */
74079fdc	267	.owner = THIS_MODULE,
b453872c JG	268	};
b453872c JG	269
b453872c JG	270	static int __init ieee80211_crypto_wep_init(void)
	271	{
	272	return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
	273	}
	274
b453872c JG	275	static void __exit ieee80211_crypto_wep_exit(void)
	276	{
	277	ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
	278	}
	279
b453872c JG	280	module_init(ieee80211_crypto_wep_init);
b453872c JG	281	module_exit(ieee80211_crypto_wep_exit);