1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Software WEP encryption implementation 4 * Copyright 2002, Jouni Malinen <jkmaline@cc.hut.fi> 5 * Copyright 2003, Instant802 Networks, Inc. 6 */ 7 8 #include <linux/netdevice.h> 9 #include <linux/types.h> 10 #include <linux/random.h> 11 #include <linux/compiler.h> 12 #include <linux/crc32.h> 13 #include <linux/crypto.h> 14 #include <linux/err.h> 15 #include <linux/mm.h> 16 #include <linux/scatterlist.h> 17 #include <linux/slab.h> 18 #include <asm/unaligned.h> 19 20 #include <net/mac80211.h> 21 #include "ieee80211_i.h" 22 #include "wep.h" 23 24 25 int ieee80211_wep_init(struct ieee80211_local *local) 26 { 27 /* start WEP IV from a random value */ 28 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN); 29 30 local->wep_tx_tfm = crypto_alloc_cipher("arc4", 0, 0); 31 if (IS_ERR(local->wep_tx_tfm)) { 32 local->wep_rx_tfm = ERR_PTR(-EINVAL); 33 return PTR_ERR(local->wep_tx_tfm); 34 } 35 36 local->wep_rx_tfm = crypto_alloc_cipher("arc4", 0, 0); 37 if (IS_ERR(local->wep_rx_tfm)) { 38 crypto_free_cipher(local->wep_tx_tfm); 39 local->wep_tx_tfm = ERR_PTR(-EINVAL); 40 return PTR_ERR(local->wep_rx_tfm); 41 } 42 43 return 0; 44 } 45 46 void ieee80211_wep_free(struct ieee80211_local *local) 47 { 48 if (!IS_ERR(local->wep_tx_tfm)) 49 crypto_free_cipher(local->wep_tx_tfm); 50 if (!IS_ERR(local->wep_rx_tfm)) 51 crypto_free_cipher(local->wep_rx_tfm); 52 } 53 54 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) 55 { 56 /* 57 * Fluhrer, Mantin, and Shamir have reported weaknesses in the 58 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 59 * 0xff, N) can be used to speedup attacks, so avoid using them. 60 */ 61 if ((iv & 0xff00) == 0xff00) { 62 u8 B = (iv >> 16) & 0xff; 63 if (B >= 3 && B < 3 + keylen) 64 return true; 65 } 66 return false; 67 } 68 69 70 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 71 int keylen, int keyidx, u8 *iv) 72 { 73 local->wep_iv++; 74 if (ieee80211_wep_weak_iv(local->wep_iv, keylen)) 75 local->wep_iv += 0x0100; 76 77 if (!iv) 78 return; 79 80 *iv++ = (local->wep_iv >> 16) & 0xff; 81 *iv++ = (local->wep_iv >> 8) & 0xff; 82 *iv++ = local->wep_iv & 0xff; 83 *iv++ = keyidx << 6; 84 } 85 86 87 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 88 struct sk_buff *skb, 89 int keylen, int keyidx) 90 { 91 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 92 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 93 unsigned int hdrlen; 94 u8 *newhdr; 95 96 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 97 98 if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN)) 99 return NULL; 100 101 hdrlen = ieee80211_hdrlen(hdr->frame_control); 102 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN); 103 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen); 104 105 /* the HW only needs room for the IV, but not the actual IV */ 106 if (info->control.hw_key && 107 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) 108 return newhdr + hdrlen; 109 110 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 111 return newhdr + hdrlen; 112 } 113 114 115 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 116 struct sk_buff *skb, 117 struct ieee80211_key *key) 118 { 119 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 120 unsigned int hdrlen; 121 122 hdrlen = ieee80211_hdrlen(hdr->frame_control); 123 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 124 skb_pull(skb, IEEE80211_WEP_IV_LEN); 125 } 126 127 128 /* Perform WEP encryption using given key. data buffer must have tailroom 129 * for 4-byte ICV. data_len must not include this ICV. Note: this function 130 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 131 int ieee80211_wep_encrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 132 size_t klen, u8 *data, size_t data_len) 133 { 134 __le32 icv; 135 int i; 136 137 if (IS_ERR(tfm)) 138 return -1; 139 140 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 141 put_unaligned(icv, (__le32 *)(data + data_len)); 142 143 crypto_cipher_setkey(tfm, rc4key, klen); 144 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) 145 crypto_cipher_encrypt_one(tfm, data + i, data + i); 146 147 return 0; 148 } 149 150 151 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 152 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 153 * buffer will be added. Both IV and ICV will be transmitted, so the 154 * payload length increases with 8 bytes. 155 * 156 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 157 */ 158 int ieee80211_wep_encrypt(struct ieee80211_local *local, 159 struct sk_buff *skb, 160 const u8 *key, int keylen, int keyidx) 161 { 162 u8 *iv; 163 size_t len; 164 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 165 166 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN)) 167 return -1; 168 169 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 170 if (!iv) 171 return -1; 172 173 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data); 174 175 /* Prepend 24-bit IV to RC4 key */ 176 memcpy(rc4key, iv, 3); 177 178 /* Copy rest of the WEP key (the secret part) */ 179 memcpy(rc4key + 3, key, keylen); 180 181 /* Add room for ICV */ 182 skb_put(skb, IEEE80211_WEP_ICV_LEN); 183 184 return ieee80211_wep_encrypt_data(local->wep_tx_tfm, rc4key, keylen + 3, 185 iv + IEEE80211_WEP_IV_LEN, len); 186 } 187 188 189 /* Perform WEP decryption using given key. data buffer includes encrypted 190 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 191 * Return 0 on success and -1 on ICV mismatch. */ 192 int ieee80211_wep_decrypt_data(struct crypto_cipher *tfm, u8 *rc4key, 193 size_t klen, u8 *data, size_t data_len) 194 { 195 __le32 crc; 196 int i; 197 198 if (IS_ERR(tfm)) 199 return -1; 200 201 crypto_cipher_setkey(tfm, rc4key, klen); 202 for (i = 0; i < data_len + IEEE80211_WEP_ICV_LEN; i++) 203 crypto_cipher_decrypt_one(tfm, data + i, data + i); 204 205 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 206 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0) 207 /* ICV mismatch */ 208 return -1; 209 210 return 0; 211 } 212 213 214 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 215 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 216 * ICV (4 bytes). skb->len includes both IV and ICV. 217 * 218 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 219 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 220 * is moved to the beginning of the skb and skb length will be reduced. 221 */ 222 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 223 struct sk_buff *skb, 224 struct ieee80211_key *key) 225 { 226 u32 klen; 227 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 228 u8 keyidx; 229 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 230 unsigned int hdrlen; 231 size_t len; 232 int ret = 0; 233 234 if (!ieee80211_has_protected(hdr->frame_control)) 235 return -1; 236 237 hdrlen = ieee80211_hdrlen(hdr->frame_control); 238 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN) 239 return -1; 240 241 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN; 242 243 keyidx = skb->data[hdrlen + 3] >> 6; 244 245 if (!key || keyidx != key->conf.keyidx) 246 return -1; 247 248 klen = 3 + key->conf.keylen; 249 250 /* Prepend 24-bit IV to RC4 key */ 251 memcpy(rc4key, skb->data + hdrlen, 3); 252 253 /* Copy rest of the WEP key (the secret part) */ 254 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 255 256 if (ieee80211_wep_decrypt_data(local->wep_rx_tfm, rc4key, klen, 257 skb->data + hdrlen + 258 IEEE80211_WEP_IV_LEN, len)) 259 ret = -1; 260 261 /* Trim ICV */ 262 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN); 263 264 /* Remove IV */ 265 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 266 skb_pull(skb, IEEE80211_WEP_IV_LEN); 267 268 return ret; 269 } 270 271 ieee80211_rx_result 272 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 273 { 274 struct sk_buff *skb = rx->skb; 275 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 276 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 277 __le16 fc = hdr->frame_control; 278 279 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) 280 return RX_CONTINUE; 281 282 if (!(status->flag & RX_FLAG_DECRYPTED)) { 283 if (skb_linearize(rx->skb)) 284 return RX_DROP_UNUSABLE; 285 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 286 return RX_DROP_UNUSABLE; 287 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 288 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + 289 IEEE80211_WEP_IV_LEN)) 290 return RX_DROP_UNUSABLE; 291 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 292 /* remove ICV */ 293 if (!(status->flag & RX_FLAG_ICV_STRIPPED) && 294 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN)) 295 return RX_DROP_UNUSABLE; 296 } 297 298 return RX_CONTINUE; 299 } 300 301 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 302 { 303 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 304 struct ieee80211_key_conf *hw_key = info->control.hw_key; 305 306 if (!hw_key) { 307 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 308 tx->key->conf.keylen, 309 tx->key->conf.keyidx)) 310 return -1; 311 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) || 312 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) { 313 if (!ieee80211_wep_add_iv(tx->local, skb, 314 tx->key->conf.keylen, 315 tx->key->conf.keyidx)) 316 return -1; 317 } 318 319 return 0; 320 } 321 322 ieee80211_tx_result 323 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 324 { 325 struct sk_buff *skb; 326 327 ieee80211_tx_set_protected(tx); 328 329 skb_queue_walk(&tx->skbs, skb) { 330 if (wep_encrypt_skb(tx, skb) < 0) { 331 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 332 return TX_DROP; 333 } 334 } 335 336 return TX_CONTINUE; 337 } 338