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