linux/drivers/staging/rtl8192u/ieee80211/ieee80211_crypt_wep.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Host AP crypt: host-based WEP encryption implementation for Host AP driver
   4 *
   5 * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
   6 */
   7
   8#include <linux/fips.h>
   9#include <linux/module.h>
  10#include <linux/init.h>
  11#include <linux/slab.h>
  12#include <linux/random.h>
  13#include <linux/skbuff.h>
  14#include <linux/string.h>
  15
  16#include "ieee80211.h"
  17
  18#include <crypto/arc4.h>
  19#include <linux/crc32.h>
  20
  21MODULE_AUTHOR("Jouni Malinen");
  22MODULE_DESCRIPTION("Host AP crypt: WEP");
  23MODULE_LICENSE("GPL");
  24
  25struct prism2_wep_data {
  26        u32 iv;
  27#define WEP_KEY_LEN 13
  28        u8 key[WEP_KEY_LEN + 1];
  29        u8 key_len;
  30        u8 key_idx;
  31        struct arc4_ctx rx_ctx_arc4;
  32        struct arc4_ctx tx_ctx_arc4;
  33};
  34
  35
  36static void *prism2_wep_init(int keyidx)
  37{
  38        struct prism2_wep_data *priv;
  39
  40        if (fips_enabled)
  41                return NULL;
  42
  43        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
  44        if (!priv)
  45                return NULL;
  46        priv->key_idx = keyidx;
  47
  48        /* start WEP IV from a random value */
  49        get_random_bytes(&priv->iv, 4);
  50
  51        return priv;
  52}
  53
  54
  55static void prism2_wep_deinit(void *priv)
  56{
  57        kfree_sensitive(priv);
  58}
  59
  60/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
  61 * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
  62 * so the payload length increases with 8 bytes.
  63 *
  64 * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
  65 */
  66static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
  67{
  68        struct prism2_wep_data *wep = priv;
  69        u32 klen, len;
  70        u8 key[WEP_KEY_LEN + 3];
  71        u8 *pos;
  72        struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
  73        u32 crc;
  74        u8 *icv;
  75
  76        if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 ||
  77            skb->len < hdr_len)
  78                return -1;
  79
  80        len = skb->len - hdr_len;
  81        pos = skb_push(skb, 4);
  82        memmove(pos, pos + 4, hdr_len);
  83        pos += hdr_len;
  84
  85        klen = 3 + wep->key_len;
  86
  87        wep->iv++;
  88
  89        /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
  90         * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
  91         * can be used to speedup attacks, so avoid using them.
  92         */
  93        if ((wep->iv & 0xff00) == 0xff00) {
  94                u8 B = (wep->iv >> 16) & 0xff;
  95
  96                if (B >= 3 && B < klen)
  97                        wep->iv += 0x0100;
  98        }
  99
 100        /* Prepend 24-bit IV to RC4 key and TX frame */
 101        *pos++ = key[0] = (wep->iv >> 16) & 0xff;
 102        *pos++ = key[1] = (wep->iv >> 8) & 0xff;
 103        *pos++ = key[2] = wep->iv & 0xff;
 104        *pos++ = wep->key_idx << 6;
 105
 106        /* Copy rest of the WEP key (the secret part) */
 107        memcpy(key + 3, wep->key, wep->key_len);
 108
 109        if (!tcb_desc->bHwSec) {
 110                /* Append little-endian CRC32 and encrypt it to produce ICV */
 111                crc = ~crc32_le(~0, pos, len);
 112                icv = skb_put(skb, 4);
 113                icv[0] = crc;
 114                icv[1] = crc >> 8;
 115                icv[2] = crc >> 16;
 116                icv[3] = crc >> 24;
 117
 118                arc4_setkey(&wep->tx_ctx_arc4, key, klen);
 119                arc4_crypt(&wep->tx_ctx_arc4, pos, pos, len + 4);
 120        }
 121
 122        return 0;
 123}
 124
 125
 126/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
 127 * the frame: IV (4 bytes), encrypted payload (including SNAP header),
 128 * ICV (4 bytes). len includes both IV and ICV.
 129 *
 130 * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
 131 * failure. If frame is OK, IV and ICV will be removed.
 132 */
 133static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
 134{
 135        struct prism2_wep_data *wep = priv;
 136        u32  klen, plen;
 137        u8 key[WEP_KEY_LEN + 3];
 138        u8 keyidx, *pos;
 139        struct cb_desc *tcb_desc = (struct cb_desc *)(skb->cb + MAX_DEV_ADDR_SIZE);
 140        u32 crc;
 141        u8 icv[4];
 142
 143        if (skb->len < hdr_len + 8)
 144                return -1;
 145
 146        pos = skb->data + hdr_len;
 147        key[0] = *pos++;
 148        key[1] = *pos++;
 149        key[2] = *pos++;
 150        keyidx = *pos++ >> 6;
 151        if (keyidx != wep->key_idx)
 152                return -1;
 153
 154        klen = 3 + wep->key_len;
 155
 156        /* Copy rest of the WEP key (the secret part) */
 157        memcpy(key + 3, wep->key, wep->key_len);
 158
 159        /* Apply RC4 to data and compute CRC32 over decrypted data */
 160        plen = skb->len - hdr_len - 8;
 161
 162        if (!tcb_desc->bHwSec) {
 163                arc4_setkey(&wep->rx_ctx_arc4, key, klen);
 164                arc4_crypt(&wep->rx_ctx_arc4, pos, pos, plen + 4);
 165
 166                crc = ~crc32_le(~0, pos, plen);
 167                icv[0] = crc;
 168                icv[1] = crc >> 8;
 169                icv[2] = crc >> 16;
 170                icv[3] = crc >> 24;
 171                if (memcmp(icv, pos + plen, 4) != 0) {
 172                        /* ICV mismatch - drop frame */
 173                        return -2;
 174                }
 175        }
 176        /* Remove IV and ICV */
 177        memmove(skb->data + 4, skb->data, hdr_len);
 178        skb_pull(skb, 4);
 179        skb_trim(skb, skb->len - 4);
 180
 181        return 0;
 182}
 183
 184
 185static int prism2_wep_set_key(void *key, int len, u8 *seq, void *priv)
 186{
 187        struct prism2_wep_data *wep = priv;
 188
 189        if (len < 0 || len > WEP_KEY_LEN)
 190                return -1;
 191
 192        memcpy(wep->key, key, len);
 193        wep->key_len = len;
 194
 195        return 0;
 196}
 197
 198
 199static int prism2_wep_get_key(void *key, int len, u8 *seq, void *priv)
 200{
 201        struct prism2_wep_data *wep = priv;
 202
 203        if (len < wep->key_len)
 204                return -1;
 205
 206        memcpy(key, wep->key, wep->key_len);
 207
 208        return wep->key_len;
 209}
 210
 211
 212static char *prism2_wep_print_stats(char *p, void *priv)
 213{
 214        struct prism2_wep_data *wep = priv;
 215
 216        p += sprintf(p, "key[%d] alg=WEP len=%d\n",
 217                     wep->key_idx, wep->key_len);
 218        return p;
 219}
 220
 221
 222static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
 223        .name                   = "WEP",
 224        .init                   = prism2_wep_init,
 225        .deinit                 = prism2_wep_deinit,
 226        .encrypt_mpdu           = prism2_wep_encrypt,
 227        .decrypt_mpdu           = prism2_wep_decrypt,
 228        .encrypt_msdu           = NULL,
 229        .decrypt_msdu           = NULL,
 230        .set_key                = prism2_wep_set_key,
 231        .get_key                = prism2_wep_get_key,
 232        .print_stats            = prism2_wep_print_stats,
 233        .extra_prefix_len       = 4, /* IV */
 234        .extra_postfix_len      = 4, /* ICV */
 235        .owner                  = THIS_MODULE,
 236};
 237
 238int __init ieee80211_crypto_wep_init(void)
 239{
 240        return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
 241}
 242
 243void __exit ieee80211_crypto_wep_exit(void)
 244{
 245        ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
 246}
 247
 248