[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/config.h>
#include <linux/version.h>
#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);
}


/* 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 key[WEP_KEY_LEN + 3];
	u8 *pos, *icv;
	struct scatterlist sg;

	if (skb_headroom(skb) < 4 || skb_tailroom(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++ = key[0] = (wep->iv >> 16) & 0xff;
	*pos++ = key[1] = (wep->iv >> 8) & 0xff;
	*pos++ = key[2] = wep->iv & 0xff;
	*pos++ = wep->key_idx << 6;

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

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