Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 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> |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 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> |
| 18 | #include <asm/string.h> |
| 19 | |
| 20 | #include <net/ieee80211.h> |
| 21 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 22 | #include <linux/crypto.h> |
| 23 | #include <asm/scatterlist.h> |
| 24 | #include <linux/crc32.h> |
| 25 | |
| 26 | MODULE_AUTHOR("Jouni Malinen"); |
| 27 | MODULE_DESCRIPTION("Host AP crypt: WEP"); |
| 28 | MODULE_LICENSE("GPL"); |
| 29 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 30 | struct prism2_wep_data { |
| 31 | u32 iv; |
| 32 | #define WEP_KEY_LEN 13 |
| 33 | u8 key[WEP_KEY_LEN + 1]; |
| 34 | u8 key_len; |
| 35 | u8 key_idx; |
| 36 | struct crypto_tfm *tfm; |
| 37 | }; |
| 38 | |
James Ketrenos | 6eb6edf | 2005-09-22 10:34:15 +0000 | [diff] [blame] | 39 | static void *prism2_wep_init(int keyidx) |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 40 | { |
| 41 | struct prism2_wep_data *priv; |
| 42 | |
| 43 | priv = kmalloc(sizeof(*priv), GFP_ATOMIC); |
| 44 | if (priv == NULL) |
| 45 | goto fail; |
| 46 | memset(priv, 0, sizeof(*priv)); |
| 47 | priv->key_idx = keyidx; |
| 48 | |
| 49 | priv->tfm = crypto_alloc_tfm("arc4", 0); |
| 50 | if (priv->tfm == NULL) { |
| 51 | printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate " |
| 52 | "crypto API arc4\n"); |
| 53 | goto fail; |
| 54 | } |
| 55 | |
| 56 | /* start WEP IV from a random value */ |
| 57 | get_random_bytes(&priv->iv, 4); |
| 58 | |
| 59 | return priv; |
| 60 | |
Jeff Garzik | 0edd5b4 | 2005-09-07 00:48:31 -0400 | [diff] [blame] | 61 | fail: |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 62 | if (priv) { |
| 63 | if (priv->tfm) |
| 64 | crypto_free_tfm(priv->tfm); |
| 65 | kfree(priv); |
| 66 | } |
| 67 | return NULL; |
| 68 | } |
| 69 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 70 | static void prism2_wep_deinit(void *priv) |
| 71 | { |
| 72 | struct prism2_wep_data *_priv = priv; |
| 73 | if (_priv && _priv->tfm) |
| 74 | crypto_free_tfm(_priv->tfm); |
| 75 | kfree(priv); |
| 76 | } |
| 77 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 78 | /* Perform WEP encryption on given skb that has at least 4 bytes of headroom |
| 79 | * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, |
| 80 | * so the payload length increases with 8 bytes. |
| 81 | * |
| 82 | * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) |
| 83 | */ |
| 84 | static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) |
| 85 | { |
| 86 | struct prism2_wep_data *wep = priv; |
| 87 | u32 crc, klen, len; |
| 88 | u8 key[WEP_KEY_LEN + 3]; |
| 89 | u8 *pos, *icv; |
| 90 | struct scatterlist sg; |
| 91 | |
| 92 | if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 || |
| 93 | skb->len < hdr_len) |
| 94 | return -1; |
| 95 | |
| 96 | len = skb->len - hdr_len; |
| 97 | pos = skb_push(skb, 4); |
| 98 | memmove(pos, pos + 4, hdr_len); |
| 99 | pos += hdr_len; |
| 100 | |
| 101 | klen = 3 + wep->key_len; |
| 102 | |
| 103 | wep->iv++; |
| 104 | |
| 105 | /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key |
| 106 | * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) |
| 107 | * can be used to speedup attacks, so avoid using them. */ |
| 108 | if ((wep->iv & 0xff00) == 0xff00) { |
| 109 | u8 B = (wep->iv >> 16) & 0xff; |
| 110 | if (B >= 3 && B < klen) |
| 111 | wep->iv += 0x0100; |
| 112 | } |
| 113 | |
| 114 | /* Prepend 24-bit IV to RC4 key and TX frame */ |
| 115 | *pos++ = key[0] = (wep->iv >> 16) & 0xff; |
| 116 | *pos++ = key[1] = (wep->iv >> 8) & 0xff; |
| 117 | *pos++ = key[2] = wep->iv & 0xff; |
| 118 | *pos++ = wep->key_idx << 6; |
| 119 | |
| 120 | /* Copy rest of the WEP key (the secret part) */ |
| 121 | memcpy(key + 3, wep->key, wep->key_len); |
| 122 | |
| 123 | /* Append little-endian CRC32 and encrypt it to produce ICV */ |
| 124 | crc = ~crc32_le(~0, pos, len); |
| 125 | icv = skb_put(skb, 4); |
| 126 | icv[0] = crc; |
| 127 | icv[1] = crc >> 8; |
| 128 | icv[2] = crc >> 16; |
| 129 | icv[3] = crc >> 24; |
| 130 | |
| 131 | crypto_cipher_setkey(wep->tfm, key, klen); |
| 132 | sg.page = virt_to_page(pos); |
| 133 | sg.offset = offset_in_page(pos); |
| 134 | sg.length = len + 4; |
| 135 | crypto_cipher_encrypt(wep->tfm, &sg, &sg, len + 4); |
| 136 | |
| 137 | return 0; |
| 138 | } |
| 139 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 140 | /* Perform WEP decryption on given buffer. Buffer includes whole WEP part of |
| 141 | * the frame: IV (4 bytes), encrypted payload (including SNAP header), |
| 142 | * ICV (4 bytes). len includes both IV and ICV. |
| 143 | * |
| 144 | * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on |
| 145 | * failure. If frame is OK, IV and ICV will be removed. |
| 146 | */ |
| 147 | static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) |
| 148 | { |
| 149 | struct prism2_wep_data *wep = priv; |
| 150 | u32 crc, klen, plen; |
| 151 | u8 key[WEP_KEY_LEN + 3]; |
| 152 | u8 keyidx, *pos, icv[4]; |
| 153 | struct scatterlist sg; |
| 154 | |
| 155 | if (skb->len < hdr_len + 8) |
| 156 | return -1; |
| 157 | |
| 158 | pos = skb->data + hdr_len; |
| 159 | key[0] = *pos++; |
| 160 | key[1] = *pos++; |
| 161 | key[2] = *pos++; |
| 162 | keyidx = *pos++ >> 6; |
| 163 | if (keyidx != wep->key_idx) |
| 164 | return -1; |
| 165 | |
| 166 | klen = 3 + wep->key_len; |
| 167 | |
| 168 | /* Copy rest of the WEP key (the secret part) */ |
| 169 | memcpy(key + 3, wep->key, wep->key_len); |
| 170 | |
| 171 | /* Apply RC4 to data and compute CRC32 over decrypted data */ |
| 172 | plen = skb->len - hdr_len - 8; |
| 173 | |
| 174 | crypto_cipher_setkey(wep->tfm, key, klen); |
| 175 | sg.page = virt_to_page(pos); |
| 176 | sg.offset = offset_in_page(pos); |
| 177 | sg.length = plen + 4; |
| 178 | crypto_cipher_decrypt(wep->tfm, &sg, &sg, plen + 4); |
| 179 | |
| 180 | crc = ~crc32_le(~0, pos, plen); |
| 181 | icv[0] = crc; |
| 182 | icv[1] = crc >> 8; |
| 183 | icv[2] = crc >> 16; |
| 184 | icv[3] = crc >> 24; |
| 185 | if (memcmp(icv, pos + plen, 4) != 0) { |
| 186 | /* ICV mismatch - drop frame */ |
| 187 | return -2; |
| 188 | } |
| 189 | |
| 190 | /* Remove IV and ICV */ |
| 191 | memmove(skb->data + 4, skb->data, hdr_len); |
| 192 | skb_pull(skb, 4); |
| 193 | skb_trim(skb, skb->len - 4); |
| 194 | |
| 195 | return 0; |
| 196 | } |
| 197 | |
Jeff Garzik | 0edd5b4 | 2005-09-07 00:48:31 -0400 | [diff] [blame] | 198 | static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv) |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 199 | { |
| 200 | struct prism2_wep_data *wep = priv; |
| 201 | |
| 202 | if (len < 0 || len > WEP_KEY_LEN) |
| 203 | return -1; |
| 204 | |
| 205 | memcpy(wep->key, key, len); |
| 206 | wep->key_len = len; |
| 207 | |
| 208 | return 0; |
| 209 | } |
| 210 | |
Jeff Garzik | 0edd5b4 | 2005-09-07 00:48:31 -0400 | [diff] [blame] | 211 | static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv) |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 212 | { |
| 213 | struct prism2_wep_data *wep = priv; |
| 214 | |
| 215 | if (len < wep->key_len) |
| 216 | return -1; |
| 217 | |
| 218 | memcpy(key, wep->key, wep->key_len); |
| 219 | |
| 220 | return wep->key_len; |
| 221 | } |
| 222 | |
Jeff Garzik | 0edd5b4 | 2005-09-07 00:48:31 -0400 | [diff] [blame] | 223 | static char *prism2_wep_print_stats(char *p, void *priv) |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 224 | { |
| 225 | struct prism2_wep_data *wep = priv; |
Jeff Garzik | 0edd5b4 | 2005-09-07 00:48:31 -0400 | [diff] [blame] | 226 | p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 227 | return p; |
| 228 | } |
| 229 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 230 | static struct ieee80211_crypto_ops ieee80211_crypt_wep = { |
James Ketrenos | 74079fd | 2005-09-13 17:35:21 -0500 | [diff] [blame] | 231 | .name = "WEP", |
| 232 | .init = prism2_wep_init, |
| 233 | .deinit = prism2_wep_deinit, |
| 234 | .encrypt_mpdu = prism2_wep_encrypt, |
| 235 | .decrypt_mpdu = prism2_wep_decrypt, |
| 236 | .encrypt_msdu = NULL, |
| 237 | .decrypt_msdu = NULL, |
| 238 | .set_key = prism2_wep_set_key, |
| 239 | .get_key = prism2_wep_get_key, |
| 240 | .print_stats = prism2_wep_print_stats, |
James Ketrenos | 1264fc0 | 2005-09-21 11:54:53 -0500 | [diff] [blame] | 241 | .extra_mpdu_prefix_len = 4, /* IV */ |
| 242 | .extra_mpdu_postfix_len = 4, /* ICV */ |
James Ketrenos | 74079fd | 2005-09-13 17:35:21 -0500 | [diff] [blame] | 243 | .owner = THIS_MODULE, |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 244 | }; |
| 245 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 246 | static int __init ieee80211_crypto_wep_init(void) |
| 247 | { |
| 248 | return ieee80211_register_crypto_ops(&ieee80211_crypt_wep); |
| 249 | } |
| 250 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 251 | static void __exit ieee80211_crypto_wep_exit(void) |
| 252 | { |
| 253 | ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep); |
| 254 | } |
| 255 | |
Jeff Garzik | b453872 | 2005-05-12 22:48:20 -0400 | [diff] [blame] | 256 | module_init(ieee80211_crypto_wep_init); |
| 257 | module_exit(ieee80211_crypto_wep_exit); |