282 lines
6.7 KiB
C
282 lines
6.7 KiB
C
/*
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* Host AP crypt: host-based WEP encryption implementation for Host AP driver
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*
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* Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation. See README and COPYING for
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* more details.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <linux/random.h>
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#include <linux/skbuff.h>
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#include <asm/string.h>
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#include <net/ieee80211.h>
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#include <linux/crypto.h>
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#include <asm/scatterlist.h>
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#include <linux/crc32.h>
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MODULE_AUTHOR("Jouni Malinen");
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MODULE_DESCRIPTION("Host AP crypt: WEP");
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MODULE_LICENSE("GPL");
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struct prism2_wep_data {
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u32 iv;
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#define WEP_KEY_LEN 13
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u8 key[WEP_KEY_LEN + 1];
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u8 key_len;
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u8 key_idx;
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struct crypto_tfm *tfm;
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};
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static void *prism2_wep_init(int keyidx)
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{
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struct prism2_wep_data *priv;
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priv = kzalloc(sizeof(*priv), GFP_ATOMIC);
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if (priv == NULL)
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goto fail;
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priv->key_idx = keyidx;
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priv->tfm = crypto_alloc_tfm("arc4", 0);
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if (priv->tfm == NULL) {
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printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate "
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"crypto API arc4\n");
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goto fail;
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}
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/* start WEP IV from a random value */
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get_random_bytes(&priv->iv, 4);
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return priv;
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fail:
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if (priv) {
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if (priv->tfm)
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crypto_free_tfm(priv->tfm);
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kfree(priv);
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}
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return NULL;
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}
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static void prism2_wep_deinit(void *priv)
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{
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struct prism2_wep_data *_priv = priv;
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if (_priv && _priv->tfm)
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crypto_free_tfm(_priv->tfm);
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kfree(priv);
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}
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/* Add WEP IV/key info to a frame that has at least 4 bytes of headroom */
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static int prism2_wep_build_iv(struct sk_buff *skb, int hdr_len,
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u8 *key, int keylen, void *priv)
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{
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struct prism2_wep_data *wep = priv;
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u32 klen, len;
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u8 *pos;
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if (skb_headroom(skb) < 4 || skb->len < hdr_len)
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return -1;
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len = skb->len - hdr_len;
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pos = skb_push(skb, 4);
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memmove(pos, pos + 4, hdr_len);
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pos += hdr_len;
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klen = 3 + wep->key_len;
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wep->iv++;
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/* Fluhrer, Mantin, and Shamir have reported weaknesses in the key
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* scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N)
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* can be used to speedup attacks, so avoid using them. */
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if ((wep->iv & 0xff00) == 0xff00) {
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u8 B = (wep->iv >> 16) & 0xff;
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if (B >= 3 && B < klen)
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wep->iv += 0x0100;
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}
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/* Prepend 24-bit IV to RC4 key and TX frame */
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*pos++ = (wep->iv >> 16) & 0xff;
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*pos++ = (wep->iv >> 8) & 0xff;
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*pos++ = wep->iv & 0xff;
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*pos++ = wep->key_idx << 6;
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return 0;
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}
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/* Perform WEP encryption on given skb that has at least 4 bytes of headroom
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* for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted,
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* so the payload length increases with 8 bytes.
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*
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* WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data))
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*/
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static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv)
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{
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struct prism2_wep_data *wep = priv;
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u32 crc, klen, len;
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u8 *pos, *icv;
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struct scatterlist sg;
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u8 key[WEP_KEY_LEN + 3];
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/* other checks are in prism2_wep_build_iv */
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if (skb_tailroom(skb) < 4)
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return -1;
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/* add the IV to the frame */
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if (prism2_wep_build_iv(skb, hdr_len, NULL, 0, priv))
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return -1;
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/* Copy the IV into the first 3 bytes of the key */
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memcpy(key, skb->data + hdr_len, 3);
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/* Copy rest of the WEP key (the secret part) */
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memcpy(key + 3, wep->key, wep->key_len);
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len = skb->len - hdr_len - 4;
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pos = skb->data + hdr_len + 4;
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klen = 3 + wep->key_len;
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/* Append little-endian CRC32 over only the data and encrypt it to produce ICV */
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crc = ~crc32_le(~0, pos, len);
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icv = skb_put(skb, 4);
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icv[0] = crc;
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icv[1] = crc >> 8;
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icv[2] = crc >> 16;
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icv[3] = crc >> 24;
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crypto_cipher_setkey(wep->tfm, key, klen);
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sg.page = virt_to_page(pos);
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sg.offset = offset_in_page(pos);
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sg.length = len + 4;
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crypto_cipher_encrypt(wep->tfm, &sg, &sg, len + 4);
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return 0;
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}
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/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of
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* the frame: IV (4 bytes), encrypted payload (including SNAP header),
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* ICV (4 bytes). len includes both IV and ICV.
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*
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* Returns 0 if frame was decrypted successfully and ICV was correct and -1 on
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* failure. If frame is OK, IV and ICV will be removed.
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*/
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static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv)
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{
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struct prism2_wep_data *wep = priv;
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u32 crc, klen, plen;
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u8 key[WEP_KEY_LEN + 3];
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u8 keyidx, *pos, icv[4];
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struct scatterlist sg;
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if (skb->len < hdr_len + 8)
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return -1;
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pos = skb->data + hdr_len;
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key[0] = *pos++;
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key[1] = *pos++;
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key[2] = *pos++;
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keyidx = *pos++ >> 6;
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if (keyidx != wep->key_idx)
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return -1;
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klen = 3 + wep->key_len;
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/* Copy rest of the WEP key (the secret part) */
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memcpy(key + 3, wep->key, wep->key_len);
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/* Apply RC4 to data and compute CRC32 over decrypted data */
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plen = skb->len - hdr_len - 8;
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crypto_cipher_setkey(wep->tfm, key, klen);
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sg.page = virt_to_page(pos);
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sg.offset = offset_in_page(pos);
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sg.length = plen + 4;
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crypto_cipher_decrypt(wep->tfm, &sg, &sg, plen + 4);
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crc = ~crc32_le(~0, pos, plen);
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icv[0] = crc;
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icv[1] = crc >> 8;
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icv[2] = crc >> 16;
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icv[3] = crc >> 24;
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if (memcmp(icv, pos + plen, 4) != 0) {
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/* ICV mismatch - drop frame */
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return -2;
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}
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/* Remove IV and ICV */
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memmove(skb->data + 4, skb->data, hdr_len);
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skb_pull(skb, 4);
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skb_trim(skb, skb->len - 4);
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return 0;
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}
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static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv)
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{
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struct prism2_wep_data *wep = priv;
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if (len < 0 || len > WEP_KEY_LEN)
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return -1;
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memcpy(wep->key, key, len);
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wep->key_len = len;
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return 0;
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}
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static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv)
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{
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struct prism2_wep_data *wep = priv;
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if (len < wep->key_len)
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return -1;
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memcpy(key, wep->key, wep->key_len);
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return wep->key_len;
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}
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static char *prism2_wep_print_stats(char *p, void *priv)
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{
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struct prism2_wep_data *wep = priv;
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p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len);
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return p;
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}
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static struct ieee80211_crypto_ops ieee80211_crypt_wep = {
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.name = "WEP",
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.init = prism2_wep_init,
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.deinit = prism2_wep_deinit,
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.build_iv = prism2_wep_build_iv,
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.encrypt_mpdu = prism2_wep_encrypt,
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.decrypt_mpdu = prism2_wep_decrypt,
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.encrypt_msdu = NULL,
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.decrypt_msdu = NULL,
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.set_key = prism2_wep_set_key,
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.get_key = prism2_wep_get_key,
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.print_stats = prism2_wep_print_stats,
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.extra_mpdu_prefix_len = 4, /* IV */
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.extra_mpdu_postfix_len = 4, /* ICV */
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.owner = THIS_MODULE,
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};
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static int __init ieee80211_crypto_wep_init(void)
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{
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return ieee80211_register_crypto_ops(&ieee80211_crypt_wep);
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}
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static void __exit ieee80211_crypto_wep_exit(void)
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{
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ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep);
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}
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module_init(ieee80211_crypto_wep_init);
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module_exit(ieee80211_crypto_wep_exit);
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