/* * Host AP crypt: host-based WEP encryption implementation for Host AP driver * * Copyright (c) 2002-2004, Jouni Malinen * * 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 #include #include #include #include #include #include #include #include "hostap_crypt.h" #ifndef CONFIG_CRYPTO #error CONFIG_CRYPTO is required to build this module. #endif #include #include #include 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; if (!try_module_get(THIS_MODULE)) return NULL; priv = (struct prism2_wep_data *) 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 "hostap_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); } module_put(THIS_MODULE); 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); module_put(THIS_MODULE); } /* 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 hostap_crypto_ops hostap_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 */ }; static int __init hostap_crypto_wep_init(void) { if (hostap_register_crypto_ops(&hostap_crypt_wep) < 0) return -1; return 0; } static void __exit hostap_crypto_wep_exit(void) { hostap_unregister_crypto_ops(&hostap_crypt_wep); } module_init(hostap_crypto_wep_init); module_exit(hostap_crypto_wep_exit);