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
  25int 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        return 0;
  31}
  32
  33static inline bool ieee80211_wep_weak_iv(u32 iv, int keylen)
  34{
  35        /*
  36         * Fluhrer, Mantin, and Shamir have reported weaknesses in the
  37         * key scheduling algorithm of RC4. At least IVs (KeyByte + 3,
  38         * 0xff, N) can be used to speedup attacks, so avoid using them.
  39         */
  40        if ((iv & 0xff00) == 0xff00) {
  41                u8 B = (iv >> 16) & 0xff;
  42                if (B >= 3 && B < 3 + keylen)
  43                        return true;
  44        }
  45        return false;
  46}
  47
  48
  49static void ieee80211_wep_get_iv(struct ieee80211_local *local,
  50                                 int keylen, int keyidx, u8 *iv)
  51{
  52        local->wep_iv++;
  53        if (ieee80211_wep_weak_iv(local->wep_iv, keylen))
  54                local->wep_iv += 0x0100;
  55
  56        if (!iv)
  57                return;
  58
  59        *iv++ = (local->wep_iv >> 16) & 0xff;
  60        *iv++ = (local->wep_iv >> 8) & 0xff;
  61        *iv++ = local->wep_iv & 0xff;
  62        *iv++ = keyidx << 6;
  63}
  64
  65
  66static u8 *ieee80211_wep_add_iv(struct ieee80211_local *local,
  67                                struct sk_buff *skb,
  68                                int keylen, int keyidx)
  69{
  70        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  71        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
  72        unsigned int hdrlen;
  73        u8 *newhdr;
  74
  75        hdr->frame_control |= cpu_to_le16(IEEE80211_FCTL_PROTECTED);
  76
  77        if (WARN_ON(skb_headroom(skb) < IEEE80211_WEP_IV_LEN))
  78                return NULL;
  79
  80        hdrlen = ieee80211_hdrlen(hdr->frame_control);
  81        newhdr = skb_push(skb, IEEE80211_WEP_IV_LEN);
  82        memmove(newhdr, newhdr + IEEE80211_WEP_IV_LEN, hdrlen);
  83
  84        /* the HW only needs room for the IV, but not the actual IV */
  85        if (info->control.hw_key &&
  86            (info->control.hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE))
  87                return newhdr + hdrlen;
  88
  89        ieee80211_wep_get_iv(local, keylen, keyidx, newhdr + hdrlen);
  90        return newhdr + hdrlen;
  91}
  92
  93
  94static void ieee80211_wep_remove_iv(struct ieee80211_local *local,
  95                                    struct sk_buff *skb,
  96                                    struct ieee80211_key *key)
  97{
  98        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
  99        unsigned int hdrlen;
 100
 101        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 102        memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 103        skb_pull(skb, IEEE80211_WEP_IV_LEN);
 104}
 105
 106
 107/* Perform WEP encryption using given key. data buffer must have tailroom
 108 * for 4-byte ICV. data_len must not include this ICV. Note: this function
 109 * does _not_ add IV. data = RC4(data | CRC32(data)) */
 110int ieee80211_wep_encrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
 111                               size_t klen, u8 *data, size_t data_len)
 112{
 113        __le32 icv;
 114
 115        icv = cpu_to_le32(~crc32_le(~0, data, data_len));
 116        put_unaligned(icv, (__le32 *)(data + data_len));
 117
 118        arc4_setkey(ctx, rc4key, klen);
 119        arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
 120        memzero_explicit(ctx, sizeof(*ctx));
 121
 122        return 0;
 123}
 124
 125
 126/* Perform WEP encryption on given skb. 4 bytes of extra space (IV) in the
 127 * beginning of the buffer 4 bytes of extra space (ICV) in the end of the
 128 * buffer will be added. Both IV and ICV will be transmitted, so the
 129 * payload length increases with 8 bytes.
 130 *
 131 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
 132 */
 133int ieee80211_wep_encrypt(struct ieee80211_local *local,
 134                          struct sk_buff *skb,
 135                          const u8 *key, int keylen, int keyidx)
 136{
 137        u8 *iv;
 138        size_t len;
 139        u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 140
 141        if (WARN_ON(skb_tailroom(skb) < IEEE80211_WEP_ICV_LEN))
 142                return -1;
 143
 144        iv = ieee80211_wep_add_iv(local, skb, keylen, keyidx);
 145        if (!iv)
 146                return -1;
 147
 148        len = skb->len - (iv + IEEE80211_WEP_IV_LEN - skb->data);
 149
 150        /* Prepend 24-bit IV to RC4 key */
 151        memcpy(rc4key, iv, 3);
 152
 153        /* Copy rest of the WEP key (the secret part) */
 154        memcpy(rc4key + 3, key, keylen);
 155
 156        /* Add room for ICV */
 157        skb_put(skb, IEEE80211_WEP_ICV_LEN);
 158
 159        return ieee80211_wep_encrypt_data(&local->wep_tx_ctx, rc4key, keylen + 3,
 160                                          iv + IEEE80211_WEP_IV_LEN, len);
 161}
 162
 163
 164/* Perform WEP decryption using given key. data buffer includes encrypted
 165 * payload, including 4-byte ICV, but _not_ IV. data_len must not include ICV.
 166 * Return 0 on success and -1 on ICV mismatch. */
 167int ieee80211_wep_decrypt_data(struct arc4_ctx *ctx, u8 *rc4key,
 168                               size_t klen, u8 *data, size_t data_len)
 169{
 170        __le32 crc;
 171
 172        arc4_setkey(ctx, rc4key, klen);
 173        arc4_crypt(ctx, data, data, data_len + IEEE80211_WEP_ICV_LEN);
 174        memzero_explicit(ctx, sizeof(*ctx));
 175
 176        crc = cpu_to_le32(~crc32_le(~0, data, data_len));
 177        if (memcmp(&crc, data + data_len, IEEE80211_WEP_ICV_LEN) != 0)
 178                /* ICV mismatch */
 179                return -1;
 180
 181        return 0;
 182}
 183
 184
 185/* Perform WEP decryption on given skb. Buffer includes whole WEP part of
 186 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 187 * ICV (4 bytes). skb->len includes both IV and ICV.
 188 *
 189 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 190 * failure. If frame is OK, IV and ICV will be removed, i.e., decrypted payload
 191 * is moved to the beginning of the skb and skb length will be reduced.
 192 */
 193static int ieee80211_wep_decrypt(struct ieee80211_local *local,
 194                                 struct sk_buff *skb,
 195                                 struct ieee80211_key *key)
 196{
 197        u32 klen;
 198        u8 rc4key[3 + WLAN_KEY_LEN_WEP104];
 199        u8 keyidx;
 200        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 201        unsigned int hdrlen;
 202        size_t len;
 203        int ret = 0;
 204
 205        if (!ieee80211_has_protected(hdr->frame_control))
 206                return -1;
 207
 208        hdrlen = ieee80211_hdrlen(hdr->frame_control);
 209        if (skb->len < hdrlen + IEEE80211_WEP_IV_LEN + IEEE80211_WEP_ICV_LEN)
 210                return -1;
 211
 212        len = skb->len - hdrlen - IEEE80211_WEP_IV_LEN - IEEE80211_WEP_ICV_LEN;
 213
 214        keyidx = skb->data[hdrlen + 3] >> 6;
 215
 216        if (!key || keyidx != key->conf.keyidx)
 217                return -1;
 218
 219        klen = 3 + key->conf.keylen;
 220
 221        /* Prepend 24-bit IV to RC4 key */
 222        memcpy(rc4key, skb->data + hdrlen, 3);
 223
 224        /* Copy rest of the WEP key (the secret part) */
 225        memcpy(rc4key + 3, key->conf.key, key->conf.keylen);
 226
 227        if (ieee80211_wep_decrypt_data(&local->wep_rx_ctx, rc4key, klen,
 228                                       skb->data + hdrlen +
 229                                       IEEE80211_WEP_IV_LEN, len))
 230                ret = -1;
 231
 232        /* Trim ICV */
 233        skb_trim(skb, skb->len - IEEE80211_WEP_ICV_LEN);
 234
 235        /* Remove IV */
 236        memmove(skb->data + IEEE80211_WEP_IV_LEN, skb->data, hdrlen);
 237        skb_pull(skb, IEEE80211_WEP_IV_LEN);
 238
 239        return ret;
 240}
 241
 242ieee80211_rx_result
 243ieee80211_crypto_wep_decrypt(struct ieee80211_rx_data *rx)
 244{
 245        struct sk_buff *skb = rx->skb;
 246        struct ieee80211_rx_status *status = IEEE80211_SKB_RXCB(skb);
 247        struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 248        __le16 fc = hdr->frame_control;
 249
 250        if (!ieee80211_is_data(fc) && !ieee80211_is_auth(fc))
 251                return RX_CONTINUE;
 252
 253        if (!(status->flag & RX_FLAG_DECRYPTED)) {
 254                if (skb_linearize(rx->skb))
 255                        return RX_DROP_UNUSABLE;
 256                if (ieee80211_wep_decrypt(rx->local, rx->skb, rx->key))
 257                        return RX_DROP_UNUSABLE;
 258        } else if (!(status->flag & RX_FLAG_IV_STRIPPED)) {
 259                if (!pskb_may_pull(rx->skb, ieee80211_hdrlen(fc) +
 260                                            IEEE80211_WEP_IV_LEN))
 261                        return RX_DROP_UNUSABLE;
 262                ieee80211_wep_remove_iv(rx->local, rx->skb, rx->key);
 263                /* remove ICV */
 264                if (!(status->flag & RX_FLAG_ICV_STRIPPED) &&
 265                    pskb_trim(rx->skb, rx->skb->len - IEEE80211_WEP_ICV_LEN))
 266                        return RX_DROP_UNUSABLE;
 267        }
 268
 269        return RX_CONTINUE;
 270}
 271
 272static int wep_encrypt_skb(struct ieee80211_tx_data *tx, struct sk_buff *skb)
 273{
 274        struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
 275        struct ieee80211_key_conf *hw_key = info->control.hw_key;
 276
 277        if (!hw_key) {
 278                if (ieee80211_wep_encrypt(tx->local, skb, tx->key->conf.key,
 279                                          tx->key->conf.keylen,
 280                                          tx->key->conf.keyidx))
 281                        return -1;
 282        } else if ((hw_key->flags & IEEE80211_KEY_FLAG_GENERATE_IV) ||
 283                   (hw_key->flags & IEEE80211_KEY_FLAG_PUT_IV_SPACE)) {
 284                if (!ieee80211_wep_add_iv(tx->local, skb,
 285                                          tx->key->conf.keylen,
 286                                          tx->key->conf.keyidx))
 287                        return -1;
 288        }
 289
 290        return 0;
 291}
 292
 293ieee80211_tx_result
 294ieee80211_crypto_wep_encrypt(struct ieee80211_tx_data *tx)
 295{
 296        struct sk_buff *skb;
 297
 298        ieee80211_tx_set_protected(tx);
 299
 300        skb_queue_walk(&tx->skbs, skb) {
 301                if (wep_encrypt_skb(tx, skb) < 0) {
 302                        I802_DEBUG_INC(tx->local->tx_handlers_drop_wep);
 303                        return TX_DROP;
 304                }
 305        }
 306
 307        return TX_CONTINUE;
 308}
 309