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/*
* AES SIV (RFC 5297)
* Copyright (c) 2013 Cozybit, Inc.
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "aes.h"
#include "aes_wrap.h"
#include "aes_siv.h"
static const u8 zero[AES_BLOCK_SIZE];
static void dbl(u8 *pad)
{
int i, carry;
carry = pad[0] & 0x80;
for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
pad[AES_BLOCK_SIZE - 1] <<= 1;
if (carry)
pad[AES_BLOCK_SIZE - 1] ^= 0x87;
}
static void xor(u8 *a, const u8 *b)
{
int i;
for (i = 0; i < AES_BLOCK_SIZE; i++)
*a++ ^= *b++;
}
static void xorend(u8 *a, int alen, const u8 *b, int blen)
{
int i;
if (alen < blen)
return;
for (i = 0; i < blen; i++)
a[alen - blen + i] ^= b[i];
}
static void pad_block(u8 *pad, const u8 *addr, size_t len)
{
os_memset(pad, 0, AES_BLOCK_SIZE);
os_memcpy(pad, addr, len);
if (len < AES_BLOCK_SIZE)
pad[len] = 0x80;
}
static int aes_s2v(const u8 *key, size_t num_elem, const u8 *addr[],
size_t *len, u8 *mac)
{
u8 tmp[AES_BLOCK_SIZE], tmp2[AES_BLOCK_SIZE];
u8 *buf = NULL;
int ret;
size_t i;
if (!num_elem) {
os_memcpy(tmp, zero, sizeof(zero));
tmp[AES_BLOCK_SIZE - 1] = 1;
return omac1_aes_128(key, tmp, sizeof(tmp), mac);
}
ret = omac1_aes_128(key, zero, sizeof(zero), tmp);
if (ret)
return ret;
for (i = 0; i < num_elem - 1; i++) {
ret = omac1_aes_128(key, addr[i], len[i], tmp2);
if (ret)
return ret;
dbl(tmp);
xor(tmp, tmp2);
}
if (len[i] >= AES_BLOCK_SIZE) {
buf = os_malloc(len[i]);
if (!buf)
return -ENOMEM;
os_memcpy(buf, addr[i], len[i]);
xorend(buf, len[i], tmp, AES_BLOCK_SIZE);
ret = omac1_aes_128(key, buf, len[i], mac);
bin_clear_free(buf, len[i]);
return ret;
}
dbl(tmp);
pad_block(tmp2, addr[i], len[i]);
xor(tmp, tmp2);
return omac1_aes_128(key, tmp, sizeof(tmp), mac);
}
int aes_siv_encrypt(const u8 *key, const u8 *pw,
size_t pwlen, size_t num_elem,
const u8 *addr[], const size_t *len, u8 *out)
{
const u8 *_addr[6];
size_t _len[6];
const u8 *k1 = key, *k2 = key + 16;
u8 v[AES_BLOCK_SIZE];
size_t i;
u8 *iv, *crypt_pw;
if (num_elem > ARRAY_SIZE(_addr) - 1)
return -1;
for (i = 0; i < num_elem; i++) {
_addr[i] = addr[i];
_len[i] = len[i];
}
_addr[num_elem] = pw;
_len[num_elem] = pwlen;
if (aes_s2v(k1, num_elem + 1, _addr, _len, v))
return -1;
iv = out;
crypt_pw = out + AES_BLOCK_SIZE;
os_memcpy(iv, v, AES_BLOCK_SIZE);
os_memcpy(crypt_pw, pw, pwlen);
/* zero out 63rd and 31st bits of ctr (from right) */
v[8] &= 0x7f;
v[12] &= 0x7f;
return aes_128_ctr_encrypt(k2, v, crypt_pw, pwlen);
}
int aes_siv_decrypt(const u8 *key, const u8 *iv_crypt, size_t iv_c_len,
size_t num_elem, const u8 *addr[], const size_t *len,
u8 *out)
{
const u8 *_addr[6];
size_t _len[6];
const u8 *k1 = key, *k2 = key + 16;
size_t crypt_len;
size_t i;
int ret;
u8 iv[AES_BLOCK_SIZE];
u8 check[AES_BLOCK_SIZE];
if (iv_c_len < AES_BLOCK_SIZE || num_elem > ARRAY_SIZE(_addr) - 1)
return -1;
crypt_len = iv_c_len - AES_BLOCK_SIZE;
for (i = 0; i < num_elem; i++) {
_addr[i] = addr[i];
_len[i] = len[i];
}
_addr[num_elem] = out;
_len[num_elem] = crypt_len;
os_memcpy(iv, iv_crypt, AES_BLOCK_SIZE);
os_memcpy(out, iv_crypt + AES_BLOCK_SIZE, crypt_len);
iv[8] &= 0x7f;
iv[12] &= 0x7f;
ret = aes_128_ctr_encrypt(k2, iv, out, crypt_len);
if (ret)
return ret;
ret = aes_s2v(k1, num_elem + 1, _addr, _len, check);
if (ret)
return ret;
if (os_memcmp(check, iv_crypt, AES_BLOCK_SIZE) == 0)
return 0;
return -1;
}
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