Root/drivers/staging/rtl8192e/rtllib_crypt_wep.c

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/module.h>
13#include <linux/init.h>
14#include <linux/slab.h>
15#include <linux/random.h>
16#include <linux/skbuff.h>
17#include <linux/string.h>
18#include "rtllib.h"
19
20#include <linux/crypto.h>
21
22#include <linux/scatterlist.h>
23#include <linux/crc32.h>
24
25struct prism2_wep_data {
26    u32 iv;
27#define WEP_KEY_LEN 13
28    u8 key[WEP_KEY_LEN + 1];
29    u8 key_len;
30    u8 key_idx;
31    struct crypto_blkcipher *tx_tfm;
32    struct crypto_blkcipher *rx_tfm;
33};
34
35
36static void *prism2_wep_init(int keyidx)
37{
38    struct prism2_wep_data *priv;
39
40    priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
41    if (priv == NULL)
42        goto fail;
43    priv->key_idx = keyidx;
44
45    priv->tx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
46    if (IS_ERR(priv->tx_tfm)) {
47        printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
48               "crypto API arc4\n");
49        priv->tx_tfm = NULL;
50        goto fail;
51    }
52    priv->rx_tfm = crypto_alloc_blkcipher("ecb(arc4)", 0, CRYPTO_ALG_ASYNC);
53    if (IS_ERR(priv->rx_tfm)) {
54        printk(KERN_DEBUG "rtllib_crypt_wep: could not allocate "
55               "crypto API arc4\n");
56        priv->rx_tfm = NULL;
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
65fail:
66    if (priv) {
67        if (priv->tx_tfm)
68            crypto_free_blkcipher(priv->tx_tfm);
69        if (priv->rx_tfm)
70            crypto_free_blkcipher(priv->rx_tfm);
71        kfree(priv);
72    }
73    return NULL;
74}
75
76
77static void prism2_wep_deinit(void *priv)
78{
79    struct prism2_wep_data *_priv = priv;
80
81    if (_priv) {
82        if (_priv->tx_tfm)
83            crypto_free_blkcipher(_priv->tx_tfm);
84        if (_priv->rx_tfm)
85            crypto_free_blkcipher(_priv->rx_tfm);
86    }
87    kfree(priv);
88}
89
90/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
91 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
92 * so the payload length increases with 8 bytes.
93 *
94 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
95 */
96static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
97{
98    struct prism2_wep_data *wep = priv;
99    u32 klen, len;
100    u8 key[WEP_KEY_LEN + 3];
101    u8 *pos;
102    struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
103                    MAX_DEV_ADDR_SIZE);
104    struct blkcipher_desc desc = {.tfm = wep->tx_tfm};
105    u32 crc;
106    u8 *icv;
107    struct scatterlist sg;
108    if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
109        skb->len < hdr_len){
110        printk(KERN_ERR "Error!!! headroom=%d tailroom=%d skblen=%d"
111               " hdr_len=%d\n", skb_headroom(skb), skb_tailroom(skb),
112               skb->len, hdr_len);
113        return -1;
114    }
115    len = skb->len - hdr_len;
116    pos = skb_push(skb, 4);
117    memmove(pos, pos + 4, hdr_len);
118    pos += hdr_len;
119
120    klen = 3 + wep->key_len;
121
122    wep->iv++;
123
124    /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
125     * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
126     * can be used to speedup attacks, so avoid using them. */
127    if ((wep->iv & 0xff00) == 0xff00) {
128        u8 B = (wep->iv >> 16) & 0xff;
129        if (B >= 3 && B < klen)
130            wep->iv += 0x0100;
131    }
132
133    /* Prepend 24-bit IV to RC4 key and TX frame */
134    *pos++ = key[0] = (wep->iv >> 16) & 0xff;
135    *pos++ = key[1] = (wep->iv >> 8) & 0xff;
136    *pos++ = key[2] = wep->iv & 0xff;
137    *pos++ = wep->key_idx << 6;
138
139    /* Copy rest of the WEP key (the secret part) */
140    memcpy(key + 3, wep->key, wep->key_len);
141
142    if (!tcb_desc->bHwSec) {
143
144        /* Append little-endian CRC32 and encrypt it to produce ICV */
145        crc = ~crc32_le(~0, pos, len);
146        icv = skb_put(skb, 4);
147        icv[0] = crc;
148        icv[1] = crc >> 8;
149        icv[2] = crc >> 16;
150        icv[3] = crc >> 24;
151
152        sg_init_one(&sg, pos, len+4);
153        crypto_blkcipher_setkey(wep->tx_tfm, key, klen);
154        return crypto_blkcipher_encrypt(&desc, &sg, &sg, len + 4);
155    }
156
157    return 0;
158}
159
160
161/* Perform WEP decryption on given struct buffer. Buffer includes whole WEP
162 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header),
163 * ICV (4 bytes). len includes both IV and ICV.
164 *
165 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
166 * failure. If frame is OK, IV and ICV will be removed.
167 */
168static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
169{
170    struct prism2_wep_data *wep = priv;
171    u32 klen, plen;
172    u8 key[WEP_KEY_LEN + 3];
173    u8 keyidx, *pos;
174    struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb +
175                    MAX_DEV_ADDR_SIZE);
176    struct blkcipher_desc desc = {.tfm = wep->rx_tfm};
177    u32 crc;
178    u8 icv[4];
179    struct scatterlist sg;
180    if (skb->len < hdr_len + 8)
181        return -1;
182
183    pos = skb->data + hdr_len;
184    key[0] = *pos++;
185    key[1] = *pos++;
186    key[2] = *pos++;
187    keyidx = *pos++ >> 6;
188    if (keyidx != wep->key_idx)
189        return -1;
190
191    klen = 3 + wep->key_len;
192
193    /* Copy rest of the WEP key (the secret part) */
194    memcpy(key + 3, wep->key, wep->key_len);
195
196    /* Apply RC4 to data and compute CRC32 over decrypted data */
197    plen = skb->len - hdr_len - 8;
198
199    if (!tcb_desc->bHwSec) {
200        sg_init_one(&sg, pos, plen+4);
201        crypto_blkcipher_setkey(wep->rx_tfm, key, klen);
202        if (crypto_blkcipher_decrypt(&desc, &sg, &sg, plen + 4))
203            return -7;
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
222
223static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
224{
225    struct prism2_wep_data *wep = priv;
226
227    if (len < 0 || len > WEP_KEY_LEN)
228        return -1;
229
230    memcpy(wep->key, key, len);
231    wep->key_len = len;
232
233    return 0;
234}
235
236
237static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
238{
239    struct prism2_wep_data *wep = priv;
240
241    if (len < wep->key_len)
242        return -1;
243
244    memcpy(key, wep->key, wep->key_len);
245
246    return wep->key_len;
247}
248
249
250static char *prism2_wep_print_stats(char *p, void *priv)
251{
252    struct prism2_wep_data *wep = priv;
253    p += sprintf(p, "key[%d] alg=WEP len=%d\n",
254             wep->key_idx, wep->key_len);
255    return p;
256}
257
258static struct lib80211_crypto_ops rtllib_crypt_wep = {
259    .name = "R-WEP",
260    .init = prism2_wep_init,
261    .deinit = prism2_wep_deinit,
262    .encrypt_mpdu = prism2_wep_encrypt,
263    .decrypt_mpdu = prism2_wep_decrypt,
264    .encrypt_msdu = NULL,
265    .decrypt_msdu = NULL,
266    .set_key = prism2_wep_set_key,
267    .get_key = prism2_wep_get_key,
268    .print_stats = prism2_wep_print_stats,
269    .extra_mpdu_prefix_len = 4, /* IV */
270    .extra_mpdu_postfix_len = 4, /* ICV */
271    .owner = THIS_MODULE,
272};
273
274
275int __init rtllib_crypto_wep_init(void)
276{
277    return lib80211_register_crypto_ops(&rtllib_crypt_wep);
278}
279
280
281void __exit rtllib_crypto_wep_exit(void)
282{
283    lib80211_unregister_crypto_ops(&rtllib_crypt_wep);
284}
285
286module_init(rtllib_crypto_wep_init);
287module_exit(rtllib_crypto_wep_exit);
288
289MODULE_LICENSE("GPL");
290

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