diff options
Diffstat (limited to 'net/ieee80211/ieee80211_crypt_wep.c')
| -rw-r--r-- | net/ieee80211/ieee80211_crypt_wep.c | 258 |
1 files changed, 258 insertions, 0 deletions
diff --git a/net/ieee80211/ieee80211_crypt_wep.c b/net/ieee80211/ieee80211_crypt_wep.c new file mode 100644 index 000000000000..b4d2514a0902 --- /dev/null +++ b/net/ieee80211/ieee80211_crypt_wep.c @@ -0,0 +1,258 @@ +/* + * Host AP crypt: host-based WEP encryption implementation for Host AP driver + * + * Copyright (c) 2002-2004, Jouni Malinen <jkmaline@cc.hut.fi> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License version 2 as + * published by the Free Software Foundation. See README and COPYING for + * more details. + */ + +#include <linux/config.h> +#include <linux/version.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/slab.h> +#include <linux/random.h> +#include <linux/skbuff.h> +#include <asm/string.h> + +#include <net/ieee80211.h> + +#include <linux/crypto.h> +#include <asm/scatterlist.h> +#include <linux/crc32.h> + +MODULE_AUTHOR("Jouni Malinen"); +MODULE_DESCRIPTION("Host AP crypt: WEP"); +MODULE_LICENSE("GPL"); + +struct prism2_wep_data { + u32 iv; +#define WEP_KEY_LEN 13 + u8 key[WEP_KEY_LEN + 1]; + u8 key_len; + u8 key_idx; + struct crypto_tfm *tfm; +}; + +static void *prism2_wep_init(int keyidx) +{ + struct prism2_wep_data *priv; + + priv = kmalloc(sizeof(*priv), GFP_ATOMIC); + if (priv == NULL) + goto fail; + memset(priv, 0, sizeof(*priv)); + priv->key_idx = keyidx; + + priv->tfm = crypto_alloc_tfm("arc4", 0); + if (priv->tfm == NULL) { + printk(KERN_DEBUG "ieee80211_crypt_wep: could not allocate " + "crypto API arc4\n"); + goto fail; + } + + /* start WEP IV from a random value */ + get_random_bytes(&priv->iv, 4); + + return priv; + + fail: + if (priv) { + if (priv->tfm) + crypto_free_tfm(priv->tfm); + kfree(priv); + } + return NULL; +} + +static void prism2_wep_deinit(void *priv) +{ + struct prism2_wep_data *_priv = priv; + if (_priv && _priv->tfm) + crypto_free_tfm(_priv->tfm); + kfree(priv); +} + +/* Perform WEP encryption on given skb that has at least 4 bytes of headroom + * for IV and 4 bytes of tailroom for ICV. Both IV and ICV will be transmitted, + * so the payload length increases with 8 bytes. + * + * WEP frame payload: IV + TX key idx, RC4(data), ICV = RC4(CRC32(data)) + */ +static int prism2_wep_encrypt(struct sk_buff *skb, int hdr_len, void *priv) +{ + struct prism2_wep_data *wep = priv; + u32 crc, klen, len; + u8 key[WEP_KEY_LEN + 3]; + u8 *pos, *icv; + struct scatterlist sg; + + if (skb_headroom(skb) < 4 || skb_tailroom(skb) < 4 || + skb->len < hdr_len) + return -1; + + len = skb->len - hdr_len; + pos = skb_push(skb, 4); + memmove(pos, pos + 4, hdr_len); + pos += hdr_len; + + klen = 3 + wep->key_len; + + wep->iv++; + + /* Fluhrer, Mantin, and Shamir have reported weaknesses in the key + * scheduling algorithm of RC4. At least IVs (KeyByte + 3, 0xff, N) + * can be used to speedup attacks, so avoid using them. */ + if ((wep->iv & 0xff00) == 0xff00) { + u8 B = (wep->iv >> 16) & 0xff; + if (B >= 3 && B < klen) + wep->iv += 0x0100; + } + + /* Prepend 24-bit IV to RC4 key and TX frame */ + *pos++ = key[0] = (wep->iv >> 16) & 0xff; + *pos++ = key[1] = (wep->iv >> 8) & 0xff; + *pos++ = key[2] = wep->iv & 0xff; + *pos++ = wep->key_idx << 6; + + /* Copy rest of the WEP key (the secret part) */ + memcpy(key + 3, wep->key, wep->key_len); + + /* Append little-endian CRC32 and encrypt it to produce ICV */ + crc = ~crc32_le(~0, pos, len); + icv = skb_put(skb, 4); + icv[0] = crc; + icv[1] = crc >> 8; + icv[2] = crc >> 16; + icv[3] = crc >> 24; + + crypto_cipher_setkey(wep->tfm, key, klen); + sg.page = virt_to_page(pos); + sg.offset = offset_in_page(pos); + sg.length = len + 4; + crypto_cipher_encrypt(wep->tfm, &sg, &sg, len + 4); + + return 0; +} + +/* Perform WEP decryption on given buffer. Buffer includes whole WEP part of + * the frame: IV (4 bytes), encrypted payload (including SNAP header), + * ICV (4 bytes). len includes both IV and ICV. + * + * Returns 0 if frame was decrypted successfully and ICV was correct and -1 on + * failure. If frame is OK, IV and ICV will be removed. + */ +static int prism2_wep_decrypt(struct sk_buff *skb, int hdr_len, void *priv) +{ + struct prism2_wep_data *wep = priv; + u32 crc, klen, plen; + u8 key[WEP_KEY_LEN + 3]; + u8 keyidx, *pos, icv[4]; + struct scatterlist sg; + + if (skb->len < hdr_len + 8) + return -1; + + pos = skb->data + hdr_len; + key[0] = *pos++; + key[1] = *pos++; + key[2] = *pos++; + keyidx = *pos++ >> 6; + if (keyidx != wep->key_idx) + return -1; + + klen = 3 + wep->key_len; + + /* Copy rest of the WEP key (the secret part) */ + memcpy(key + 3, wep->key, wep->key_len); + + /* Apply RC4 to data and compute CRC32 over decrypted data */ + plen = skb->len - hdr_len - 8; + + crypto_cipher_setkey(wep->tfm, key, klen); + sg.page = virt_to_page(pos); + sg.offset = offset_in_page(pos); + sg.length = plen + 4; + crypto_cipher_decrypt(wep->tfm, &sg, &sg, plen + 4); + + crc = ~crc32_le(~0, pos, plen); + icv[0] = crc; + icv[1] = crc >> 8; + icv[2] = crc >> 16; + icv[3] = crc >> 24; + if (memcmp(icv, pos + plen, 4) != 0) { + /* ICV mismatch - drop frame */ + return -2; + } + + /* Remove IV and ICV */ + memmove(skb->data + 4, skb->data, hdr_len); + skb_pull(skb, 4); + skb_trim(skb, skb->len - 4); + + return 0; +} + +static int prism2_wep_set_key(void *key, int len, u8 * seq, void *priv) +{ + struct prism2_wep_data *wep = priv; + + if (len < 0 || len > WEP_KEY_LEN) + return -1; + + memcpy(wep->key, key, len); + wep->key_len = len; + + return 0; +} + +static int prism2_wep_get_key(void *key, int len, u8 * seq, void *priv) +{ + struct prism2_wep_data *wep = priv; + + if (len < wep->key_len) + return -1; + + memcpy(key, wep->key, wep->key_len); + + return wep->key_len; +} + +static char *prism2_wep_print_stats(char *p, void *priv) +{ + struct prism2_wep_data *wep = priv; + p += sprintf(p, "key[%d] alg=WEP len=%d\n", wep->key_idx, wep->key_len); + return p; +} + +static struct ieee80211_crypto_ops ieee80211_crypt_wep = { + .name = "WEP", + .init = prism2_wep_init, + .deinit = prism2_wep_deinit, + .encrypt_mpdu = prism2_wep_encrypt, + .decrypt_mpdu = prism2_wep_decrypt, + .encrypt_msdu = NULL, + .decrypt_msdu = NULL, + .set_key = prism2_wep_set_key, + .get_key = prism2_wep_get_key, + .print_stats = prism2_wep_print_stats, + .extra_prefix_len = 4, /* IV */ + .extra_postfix_len = 4, /* ICV */ + .owner = THIS_MODULE, +}; + +static int __init ieee80211_crypto_wep_init(void) +{ + return ieee80211_register_crypto_ops(&ieee80211_crypt_wep); +} + +static void __exit ieee80211_crypto_wep_exit(void) +{ + ieee80211_unregister_crypto_ops(&ieee80211_crypt_wep); +} + +module_init(ieee80211_crypto_wep_init); +module_exit(ieee80211_crypto_wep_exit); |