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/*
* Crypto wrapper for internal crypto implementation - modexp
* Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "tls/bignum.h"
#include "crypto.h"
int crypto_dh_init(u8 generator, const u8 *prime, size_t prime_len, u8 *privkey,
u8 *pubkey)
{
size_t pubkey_len, pad;
if (os_get_random(privkey, prime_len) < 0)
return -1;
if (os_memcmp(privkey, prime, prime_len) > 0) {
/* Make sure private value is smaller than prime */
privkey[0] = 0;
}
pubkey_len = prime_len;
if (crypto_mod_exp(&generator, 1, privkey, prime_len, prime, prime_len,
pubkey, &pubkey_len) < 0)
return -1;
if (pubkey_len < prime_len) {
pad = prime_len - pubkey_len;
os_memmove(pubkey + pad, pubkey, pubkey_len);
os_memset(pubkey, 0, pad);
}
return 0;
}
int crypto_dh_derive_secret(u8 generator, const u8 *prime, size_t prime_len,
const u8 *order, size_t order_len,
const u8 *privkey, size_t privkey_len,
const u8 *pubkey, size_t pubkey_len,
u8 *secret, size_t *len)
{
struct bignum *pub;
int res = -1;
if (pubkey_len > prime_len ||
(pubkey_len == prime_len &&
os_memcmp(pubkey, prime, prime_len) >= 0))
return -1;
pub = bignum_init();
if (!pub || bignum_set_unsigned_bin(pub, pubkey, pubkey_len) < 0 ||
bignum_cmp_d(pub, 1) <= 0)
goto fail;
if (order) {
struct bignum *p, *q, *tmp;
int failed;
/* verify: pubkey^q == 1 mod p */
p = bignum_init();
q = bignum_init();
tmp = bignum_init();
failed = !p || !q || !tmp ||
bignum_set_unsigned_bin(p, prime, prime_len) < 0 ||
bignum_set_unsigned_bin(q, order, order_len) < 0 ||
bignum_exptmod(pub, q, p, tmp) < 0 ||
bignum_cmp_d(tmp, 1) != 0;
bignum_deinit(p);
bignum_deinit(q);
bignum_deinit(tmp);
if (failed)
goto fail;
}
res = crypto_mod_exp(pubkey, pubkey_len, privkey, privkey_len,
prime, prime_len, secret, len);
fail:
bignum_deinit(pub);
return res;
}
int crypto_mod_exp(const u8 *base, size_t base_len,
const u8 *power, size_t power_len,
const u8 *modulus, size_t modulus_len,
u8 *result, size_t *result_len)
{
struct bignum *bn_base, *bn_exp, *bn_modulus, *bn_result;
int ret = -1;
bn_base = bignum_init();
bn_exp = bignum_init();
bn_modulus = bignum_init();
bn_result = bignum_init();
if (bn_base == NULL || bn_exp == NULL || bn_modulus == NULL ||
bn_result == NULL)
goto error;
if (bignum_set_unsigned_bin(bn_base, base, base_len) < 0 ||
bignum_set_unsigned_bin(bn_exp, power, power_len) < 0 ||
bignum_set_unsigned_bin(bn_modulus, modulus, modulus_len) < 0)
goto error;
if (bignum_exptmod(bn_base, bn_exp, bn_modulus, bn_result) < 0)
goto error;
ret = bignum_get_unsigned_bin(bn_result, result, result_len);
error:
bignum_deinit(bn_base);
bignum_deinit(bn_exp);
bignum_deinit(bn_modulus);
bignum_deinit(bn_result);
return ret;
}
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