LXR linux/net/mac80211/wep.c

   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
  25void 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
  31static 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
  47static 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
  64static 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
  92static 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)) */
 108int 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 */
 131int 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. */
 165int 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 */
 191static 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
 240ieee80211_rx_result
 241ieee80211_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
 270static 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
 291ieee80211_tx_result
 292ieee80211_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