1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Host AP crypt: host-based WEP encryption implementation for Host AP driver 4 * 5 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi> 6 */ 7 8 #include <crypto/skcipher.h> 9 #include <linux/module.h> 10 #include <linux/init.h> 11 #include <linux/slab.h> 12 #include <linux/random.h> 13 #include <linux/skbuff.h> 14 #include <linux/string.h> 15 #include "rtllib.h" 16 17 #include <linux/scatterlist.h> 18 #include <linux/crc32.h> 19 20 struct prism2_wep_data { 21 u32 iv; 22 #define WEP_KEY_LEN 13 23 u8 key[WEP_KEY_LEN + 1]; 24 u8 key_len; 25 u8 key_idx; 26 struct crypto_sync_skcipher *tx_tfm; 27 struct crypto_sync_skcipher *rx_tfm; 28 }; 29 30 31 static void *prism2_wep_init(int keyidx) 32 { 33 struct prism2_wep_data *priv; 34 35 priv = kzalloc(sizeof(*priv), GFP_ATOMIC); 36 if (priv == NULL) 37 goto fail; 38 priv->key_idx = keyidx; 39 40 priv->tx_tfm = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0); 41 if (IS_ERR(priv->tx_tfm)) { 42 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n"); 43 priv->tx_tfm = NULL; 44 goto fail; 45 } 46 priv->rx_tfm = crypto_alloc_sync_skcipher("ecb(arc4)", 0, 0); 47 if (IS_ERR(priv->rx_tfm)) { 48 pr_debug("rtllib_crypt_wep: could not allocate crypto API arc4\n"); 49 priv->rx_tfm = NULL; 50 goto fail; 51 } 52 53 /* start WEP IV from a random value */ 54 get_random_bytes(&priv->iv, 4); 55 56 return priv; 57 58 fail: 59 if (priv) { 60 crypto_free_sync_skcipher(priv->tx_tfm); 61 crypto_free_sync_skcipher(priv->rx_tfm); 62 kfree(priv); 63 } 64 return NULL; 65 } 66 67 68 static void prism2_wep_deinit(void *priv) 69 { 70 struct prism2_wep_data *_priv = priv; 71 72 if (_priv) { 73 crypto_free_sync_skcipher(_priv->tx_tfm); 74 crypto_free_sync_skcipher(_priv->rx_tfm); 75 } 76 kfree(priv); 77 } 78 79 /* Perform WEP encryption on given skb that has at least 4 bytes of headroom 80 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, 81 * so the payload length increases with 8 bytes. 82 * 83 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 84 */ 85 static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) 86 { 87 struct prism2_wep_data *wep = priv; 88 u32 klen, len; 89 u8 key[WEP_KEY_LEN + 3]; 90 u8 *pos; 91 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + 92 MAX_DEV_ADDR_SIZE); 93 u32 crc; 94 u8 *icv; 95 struct scatterlist sg; 96 int err; 97 98 if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 || 99 skb->len < hdr_len){ 100 pr_err("Error!!! headroom=%d tailroom=%d skblen=%d hdr_len=%d\n", 101 skb_headroom(skb), skb_tailroom(skb), skb->len, hdr_len); 102 return -1; 103 } 104 len = skb->len - hdr_len; 105 pos = skb_push(skb, 4); 106 memmove(pos, pos + 4, hdr_len); 107 pos += hdr_len; 108 109 klen = 3 + wep->key_len; 110 111 wep->iv++; 112 113 /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key 114 * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) 115 * can be used to speedup attacks, so avoid using them. 116 */ 117 if ((wep->iv & 0xff00) == 0xff00) { 118 u8 B = (wep->iv >> 16) & 0xff; 119 120 if (B >= 3 && B < klen) 121 wep->iv += 0x0100; 122 } 123 124 /* Prepend 24-bit IV to RC4 key and TX frame */ 125 *pos++ = key[0] = (wep->iv >> 16) & 0xff; 126 *pos++ = key[1] = (wep->iv >> 8) & 0xff; 127 *pos++ = key[2] = wep->iv & 0xff; 128 *pos++ = wep->key_idx << 6; 129 130 /* Copy rest of the WEP key (the secret part) */ 131 memcpy(key + 3, wep->key, wep->key_len); 132 133 if (!tcb_desc->bHwSec) { 134 SYNC_SKCIPHER_REQUEST_ON_STACK(req, wep->tx_tfm); 135 136 /* Append little-endian CRC32 and encrypt it to produce ICV */ 137 crc = ~crc32_le(~0, pos, len); 138 icv = skb_put(skb, 4); 139 icv[0] = crc; 140 icv[1] = crc >> 8; 141 icv[2] = crc >> 16; 142 icv[3] = crc >> 24; 143 144 sg_init_one(&sg, pos, len+4); 145 crypto_sync_skcipher_setkey(wep->tx_tfm, key, klen); 146 skcipher_request_set_sync_tfm(req, wep->tx_tfm); 147 skcipher_request_set_callback(req, 0, NULL, NULL); 148 skcipher_request_set_crypt(req, &sg, &sg, len + 4, NULL); 149 err = crypto_skcipher_encrypt(req); 150 skcipher_request_zero(req); 151 return err; 152 } 153 154 return 0; 155 } 156 157 158 /* Perform WEP decryption on given struct buffer. Buffer includes whole WEP 159 * part of the frame: IV (4 bytes), encrypted payload (including SNAP header), 160 * ICV (4 bytes). len includes both IV and ICV. 161 * 162 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 163 * failure. If frame is OK, IV and ICV will be removed. 164 */ 165 static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) 166 { 167 struct prism2_wep_data *wep = priv; 168 u32 klen, plen; 169 u8 key[WEP_KEY_LEN + 3]; 170 u8 keyidx, *pos; 171 struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + 172 MAX_DEV_ADDR_SIZE); 173 u32 crc; 174 u8 icv[4]; 175 struct scatterlist sg; 176 int err; 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 if (!tcb_desc->bHwSec) { 198 SYNC_SKCIPHER_REQUEST_ON_STACK(req, wep->rx_tfm); 199 200 sg_init_one(&sg, pos, plen+4); 201 crypto_sync_skcipher_setkey(wep->rx_tfm, key, klen); 202 skcipher_request_set_sync_tfm(req, wep->rx_tfm); 203 skcipher_request_set_callback(req, 0, NULL, NULL); 204 skcipher_request_set_crypt(req, &sg, &sg, plen + 4, NULL); 205 err = crypto_skcipher_decrypt(req); 206 skcipher_request_zero(req); 207 if (err) 208 return -7; 209 crc = ~crc32_le(~0, pos, plen); 210 icv[0] = crc; 211 icv[1] = crc >> 8; 212 icv[2] = crc >> 16; 213 icv[3] = crc >> 24; 214 if (memcmp(icv, pos + plen, 4) != 0) { 215 /* ICV mismatch - drop frame */ 216 return -2; 217 } 218 } 219 /* Remove IV and ICV */ 220 memmove(skb->data + 4, skb->data, hdr_len); 221 skb_pull(skb, 4); 222 skb_trim(skb, skb->len - 4); 223 224 return 0; 225 } 226 227 228 static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv) 229 { 230 struct prism2_wep_data *wep = priv; 231 232 if (len < 0 || len > WEP_KEY_LEN) 233 return -1; 234 235 memcpy(wep->key, key, len); 236 wep->key_len = len; 237 238 return 0; 239 } 240 241 242 static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv) 243 { 244 struct prism2_wep_data *wep = priv; 245 246 if (len < wep->key_len) 247 return -1; 248 249 memcpy(key, wep->key, wep->key_len); 250 251 return wep->key_len; 252 } 253 254 255 static void prism2_wep_print_stats(struct seq_file *m, void *priv) 256 { 257 struct prism2_wep_data *wep = priv; 258 259 seq_printf(m, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); 260 } 261 262 static struct lib80211_crypto_ops rtllib_crypt_wep = { 263 .name = "R-WEP", 264 .init = prism2_wep_init, 265 .deinit = prism2_wep_deinit, 266 .encrypt_mpdu = prism2_wep_encrypt, 267 .decrypt_mpdu = prism2_wep_decrypt, 268 .encrypt_msdu = NULL, 269 .decrypt_msdu = NULL, 270 .set_key = prism2_wep_set_key, 271 .get_key = prism2_wep_get_key, 272 .print_stats = prism2_wep_print_stats, 273 .extra_mpdu_prefix_len = 4, /* IV */ 274 .extra_mpdu_postfix_len = 4, /* ICV */ 275 .owner = THIS_MODULE, 276 }; 277 278 279 static int __init rtllib_crypto_wep_init(void) 280 { 281 return lib80211_register_crypto_ops(&rtllib_crypt_wep); 282 } 283 284 285 static void __exit rtllib_crypto_wep_exit(void) 286 { 287 lib80211_unregister_crypto_ops(&rtllib_crypt_wep); 288 } 289 290 module_init(rtllib_crypto_wep_init); 291 module_exit(rtllib_crypto_wep_exit); 292 293 MODULE_LICENSE("GPL"); 294