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/*
* Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
*
* 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
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*/
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <stdio.h>
#include "ead.h"
#include "sha1.c"
#include "aes.c"
#if EAD_DEBUGLEVEL >= 1
#define DEBUG(n, format, ...) do { \
if (EAD_DEBUGLEVEL >= n) \
fprintf(stderr, format, ##__VA_ARGS__); \
} while (0);
#else
#define DEBUG(n, format, ...) do {} while(0)
#endif
static uint32_t aes_enc_ctx[AES_PRIV_SIZE];
static uint32_t aes_dec_ctx[AES_PRIV_SIZE];
static uint32_t ead_rx_iv;
static uint32_t ead_tx_iv;
static uint32_t ivofs_vec;
static unsigned int ivofs_idx = 0;
static uint32_t W[80]; /* work space for sha1 */
#define EAD_ENC_PAD 64
void
ead_set_key(unsigned char *skey)
{
uint32_t *ivp = (uint32_t *)skey;
memset(aes_enc_ctx, 0, sizeof(aes_enc_ctx));
memset(aes_dec_ctx, 0, sizeof(aes_dec_ctx));
/* first 32 bytes of skey are used as aes key for
* encryption and decryption */
rijndaelKeySetupEnc(aes_enc_ctx, skey);
rijndaelKeySetupDec(aes_dec_ctx, skey);
/* the following bytes are used as initialization vector for messages
* (highest byte cleared to avoid overflow) */
ivp += 8;
ead_rx_iv = ntohl(*ivp) & 0x00ffffff;
ead_tx_iv = ead_rx_iv;
/* the last bytes are used to feed the random iv increment */
ivp++;
ivofs_vec = *ivp;
}
static bool
ead_check_rx_iv(uint32_t iv)
{
if (iv <= ead_rx_iv)
return false;
if (iv > ead_rx_iv + EAD_MAX_IV_INCR)
return false;
ead_rx_iv = iv;
return true;
}
static uint32_t
ead_get_tx_iv(void)
{
unsigned int ofs;
ofs = 1 + ((ivofs_vec >> 2 * ivofs_idx) & 0x3);
ivofs_idx = (ivofs_idx + 1) % 16;
ead_tx_iv += ofs;
return ead_tx_iv;
}
static void
ead_hash_message(struct ead_msg_encrypted *enc, uint32_t *hash, int len)
{
unsigned char *data = (unsigned char *) enc;
/* hash the packet with the stored hash part initialized to zero */
sha_init(hash);
memset(enc->hash, 0, sizeof(enc->hash));
while (len > 0) {
sha_transform(hash, data, W);
len -= 64;
data += 64;
}
}
void
ead_encrypt_message(struct ead_msg *msg, unsigned int len)
{
struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
unsigned char *data = (unsigned char *) enc;
uint32_t hash[5];
int enclen, i;
len += sizeof(struct ead_msg_encrypted);
enc->pad = (EAD_ENC_PAD - (len % EAD_ENC_PAD)) % EAD_ENC_PAD;
enclen = len + enc->pad;
msg->len = htonl(enclen);
enc->iv = htonl(ead_get_tx_iv());
ead_hash_message(enc, hash, enclen);
for (i = 0; i < 5; i++)
enc->hash[i] = htonl(hash[i]);
DEBUG(2, "SHA1 generate (0x%08x), len=%d\n", enc->hash[0], enclen);
while (enclen > 0) {
rijndaelEncrypt(aes_enc_ctx, data, data);
data += 16;
enclen -= 16;
}
}
int
ead_decrypt_message(struct ead_msg *msg)
{
struct ead_msg_encrypted *enc = EAD_DATA(msg, enc);
unsigned char *data = (unsigned char *) enc;
uint32_t hash_old[5], hash_new[5];
int len = ntohl(msg->len);
int i, enclen = len;
if (!len || (len % EAD_ENC_PAD > 0))
return 0;
while (len > 0) {
rijndaelDecrypt(aes_dec_ctx, data, data);
data += 16;
len -= 16;
}
data = (unsigned char *) enc;
if (enc->pad >= EAD_ENC_PAD) {
DEBUG(2, "Invalid padding length\n");
return 0;
}
if (!ead_check_rx_iv(ntohl(enc->iv))) {
DEBUG(2, "RX IV mismatch (0x%08x <> 0x%08x)\n", ead_rx_iv, ntohl(enc->iv));
return 0;
}
for (i = 0; i < 5; i++)
hash_old[i] = ntohl(enc->hash[i]);
ead_hash_message(enc, hash_new, enclen);
if (memcmp(hash_old, hash_new, sizeof(hash_old)) != 0) {
DEBUG(2, "SHA1 mismatch (0x%08x != 0x%08x), len=%d\n", hash_old[0], hash_new[0], enclen);
return 0;
}
enclen -= enc->pad + sizeof(struct ead_msg_encrypted);
return enclen;
}
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