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 * Copyright (C) 2023 Intel Corporation 7 */ 8 9 #include <linux/netdevice.h> 10 #include <linux/types.h> 11 #include <linux/random.h> 12 #include <linux/compiler.h> 13 #include <linux/crc32.h> 14 #include <linux/crypto.h> 15 #include <linux/err.h> 16 #include <linux/mm.h> 17 #include <linux/scatterlist.h> 18 #include <linux/slab.h> 19 #include <asm/unaligned.h> 20 21 #include <net/mac80211.h> 22 #include "ieee80211_i.h" 23 #include "wep.h" 24 25 26 void ieee80211_wep_init(struct ieee80211_local *local) 27 { 28 /* start WEP IV from a random value */ 29 get_random_bytes(&local->wep_iv, IEEE80211_WEP_IV_LEN); 30 } 31 32 static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen) 33 { 34 /* 35 * Fluhrer, Mantin, and Shamir have reported weaknesses in the 36 * key scheduling algorithm of RC4. At least IVs (KeyByte + 3, 37 * 0xff, N) can be used to speedup attacks, so avoid using them. 38 */ 39 if ((iv & 0xff00) == 0xff00) { 40 u8 B = (iv >> 16) & 0xff; 41 if (B >= 3 && B < 3 + keylen) 42 return true; 43 } 44 return false; 45 } 46 47 48 static void ieee80211_wep_get_iv(struct ieee80211_local *local, 49 int keylen, int keyidx, u8 *iv) 50 { 51 local->wep_iv++; 52 if (ieee80211_wep_weak_iv(local->wep_iv, keylen)) 53 local->wep_iv += 0x0100; 54 55 if (!iv) 56 return; 57 58 *iv++ = (local->wep_iv >> 16) & 0xff; 59 *iv++ = (local->wep_iv >> 8) & 0xff; 60 *iv++ = local->wep_iv & 0xff; 61 *iv++ = keyidx << 6; 62 } 63 64 65 static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local, 66 struct sk_buff *skb, 67 int keylen, int keyidx) 68 { 69 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 70 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 71 unsigned int hdrlen; 72 u8 *newhdr; 73 74 hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED); 75 76 if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN)) 77 return NULL; 78 79 hdrlen = ieee80211_hdrlen(hdr->frame_control); 80 newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN); 81 memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen); 82 83 /* the HW only needs room for the IV, but not the actual IV */ 84 if (info->control.hw_key && 85 (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) 86 return newhdr + hdrlen; 87 88 ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen); 89 return newhdr + hdrlen; 90 } 91 92 93 static void ieee80211_wep_remove_iv(struct ieee80211_local *local, 94 struct sk_buff *skb, 95 struct ieee80211_key *key) 96 { 97 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 98 unsigned int hdrlen; 99 100 hdrlen = ieee80211_hdrlen(hdr->frame_control); 101 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 102 skb_pull(skb, IEEE80211_WEP_IV_LEN); 103 } 104 105 106 /* Perform WEP encryption using given key. data buffer must have tailroom 107 * for 4-byte ICV. data_len must not include this ICV. Note: this function 108 * does _not_ add IV. data = RC4(data | CRC32(data)) */ 109 int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key, 110 size_t klen, u8 *data, size_t data_len) 111 { 112 __le32 icv; 113 114 icv = cpu_to_le32(~crc32_le(~0, data, data_len)); 115 put_unaligned(icv, (__le32 *)(data + data_len)); 116 117 arc4_setkey(ctx, rc4key, klen); 118 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN); 119 memzero_explicit(ctx, sizeof(*ctx)); 120 121 return 0; 122 } 123 124 125 /* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the 126 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the 127 * buffer will be added. Both IV and ICV will be transmitted, so the 128 * payload length increases with 8 bytes. 129 * 130 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) 131 */ 132 int ieee80211_wep_encrypt(struct ieee80211_local *local, 133 struct sk_buff *skb, 134 const u8 *key, int keylen, int keyidx) 135 { 136 u8 *iv; 137 size_t len; 138 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 139 140 if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN)) 141 return -1; 142 143 iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx); 144 if (!iv) 145 return -1; 146 147 len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data); 148 149 /* Prepend 24-bit IV to RC4 key */ 150 memcpy(rc4key, iv, 3); 151 152 /* Copy rest of the WEP key (the secret part) */ 153 memcpy(rc4key + 3, key, keylen); 154 155 /* Add room for ICV */ 156 skb_put(skb, IEEE80211_WEP_ICV_LEN); 157 158 return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3, 159 iv + IEEE80211_WEP_IV_LEN, len); 160 } 161 162 163 /* Perform WEP decryption using given key. data buffer includes encrypted 164 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV. 165 * Return 0 on success and -1 on ICV mismatch. */ 166 int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key, 167 size_t klen, u8 *data, size_t data_len) 168 { 169 __le32 crc; 170 171 arc4_setkey(ctx, rc4key, klen); 172 arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN); 173 memzero_explicit(ctx, sizeof(*ctx)); 174 175 crc = cpu_to_le32(~crc32_le(~0, data, data_len)); 176 if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0) 177 /* ICV mismatch */ 178 return -1; 179 180 return 0; 181 } 182 183 184 /* Perform WEP decryption on given skb. Buffer includes whole WEP part of 185 * the frame: IV (4 bytes), encrypted payload (including SNAP header), 186 * ICV (4 bytes). skb->len includes both IV and ICV. 187 * 188 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on 189 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload 190 * is moved to the beginning of the skb and skb length will be reduced. 191 */ 192 static int ieee80211_wep_decrypt(struct ieee80211_local *local, 193 struct sk_buff *skb, 194 struct ieee80211_key *key) 195 { 196 u32 klen; 197 u8 rc4key[3 + WLAN_KEY_LEN_WEP104]; 198 u8 keyidx; 199 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 200 unsigned int hdrlen; 201 size_t len; 202 int ret = 0; 203 204 if (!ieee80211_has_protected(hdr->frame_control)) 205 return -1; 206 207 hdrlen = ieee80211_hdrlen(hdr->frame_control); 208 if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN) 209 return -1; 210 211 len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN; 212 213 keyidx = skb->data[hdrlen + 3] >> 6; 214 215 if (!key || keyidx != key->conf.keyidx) 216 return -1; 217 218 klen = 3 + key->conf.keylen; 219 220 /* Prepend 24-bit IV to RC4 key */ 221 memcpy(rc4key, skb->data + hdrlen, 3); 222 223 /* Copy rest of the WEP key (the secret part) */ 224 memcpy(rc4key + 3, key->conf.key, key->conf.keylen); 225 226 if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen, 227 skb->data + hdrlen + 228 IEEE80211_WEP_IV_LEN, len)) 229 ret = -1; 230 231 /* Trim ICV */ 232 skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN); 233 234 /* Remove IV */ 235 memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen); 236 skb_pull(skb, IEEE80211_WEP_IV_LEN); 237 238 return ret; 239 } 240 241 ieee80211_rx_result 242 ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx) 243 { 244 struct sk_buff *skb = rx->skb; 245 struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb); 246 struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data; 247 __le16 fc = hdr->frame_control; 248 249 if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc)) 250 return RX_CONTINUE; 251 252 if (!(status->flag & RX_FLAG_DECRYPTED)) { 253 if (skb_linearize(rx->skb)) 254 return RX_DROP_U_OOM; 255 if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key)) 256 return RX_DROP_U_WEP_DEC_FAIL; 257 } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) { 258 if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) + 259 IEEE80211_WEP_IV_LEN)) 260 return RX_DROP_U_NO_IV; 261 ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key); 262 /* remove ICV */ 263 if (!(status->flag & RX_FLAG_ICV_STRIPPED) && 264 pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN)) 265 return RX_DROP_U_NO_ICV; 266 } 267 268 return RX_CONTINUE; 269 } 270 271 static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb) 272 { 273 struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb); 274 struct ieee80211_key_conf *hw_key = info->control.hw_key; 275 276 if (!hw_key) { 277 if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key, 278 tx->key->conf.keylen, 279 tx->key->conf.keyidx)) 280 return -1; 281 } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) || 282 (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) { 283 if (!ieee80211_wep_add_iv(tx->local, skb, 284 tx->key->conf.keylen, 285 tx->key->conf.keyidx)) 286 return -1; 287 } 288 289 return 0; 290 } 291 292 ieee80211_tx_result 293 ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx) 294 { 295 struct sk_buff *skb; 296 297 ieee80211_tx_set_protected(tx); 298 299 skb_queue_walk(&tx->skbs, skb) { 300 if (wep_encrypt_skb(tx, skb) < 0) { 301 I802_DEBUG_INC(tx->local->tx_handlers_drop_wep); 302 return TX_DROP; 303 } 304 } 305 306 return TX_CONTINUE; 307 } 308