1/*
2 * Crypto wrapper for internal crypto implementation - modexp
3 * Copyright (c) 2006-2009, Jouni Malinen <j@w1.fi>
4 *
5 * This software may be distributed under the terms of the BSD license.
6 * See README for more details.
7 */
8
9#include "includes.h"
10
11#include "common.h"
12#include "tls/bignum.h"
13#include "crypto.h"
14
15
16int crypto_dh_init(u8 generator, const u8 *prime, size_t prime_len, u8 *privkey,
17		   u8 *pubkey)
18{
19	size_t pubkey_len, pad;
20
21	if (os_get_random(privkey, prime_len) < 0)
22		return -1;
23	if (os_memcmp(privkey, prime, prime_len) > 0) {
24		/* Make sure private value is smaller than prime */
25		privkey[0] = 0;
26	}
27
28	pubkey_len = prime_len;
29	if (crypto_mod_exp(&generator, 1, privkey, prime_len, prime, prime_len,
30			   pubkey, &pubkey_len) < 0)
31		return -1;
32	if (pubkey_len < prime_len) {
33		pad = prime_len - pubkey_len;
34		os_memmove(pubkey + pad, pubkey, pubkey_len);
35		os_memset(pubkey, 0, pad);
36	}
37
38	return 0;
39}
40
41
42int crypto_dh_derive_secret(u8 generator, const u8 *prime, size_t prime_len,
43			    const u8 *order, size_t order_len,
44			    const u8 *privkey, size_t privkey_len,
45			    const u8 *pubkey, size_t pubkey_len,
46			    u8 *secret, size_t *len)
47{
48	struct bignum *pub;
49	int res = -1;
50
51	if (pubkey_len > prime_len ||
52	    (pubkey_len == prime_len &&
53	     os_memcmp(pubkey, prime, prime_len) >= 0))
54		return -1;
55
56	pub = bignum_init();
57	if (!pub || bignum_set_unsigned_bin(pub, pubkey, pubkey_len) < 0 ||
58	    bignum_cmp_d(pub, 1) <= 0)
59		goto fail;
60
61	if (order) {
62		struct bignum *p, *q, *tmp;
63		int failed;
64
65		/* verify: pubkey^q == 1 mod p */
66		p = bignum_init();
67		q = bignum_init();
68		tmp = bignum_init();
69		failed = !p || !q || !tmp ||
70			bignum_set_unsigned_bin(p, prime, prime_len) < 0 ||
71			bignum_set_unsigned_bin(q, order, order_len) < 0 ||
72			bignum_exptmod(pub, q, p, tmp) < 0 ||
73			bignum_cmp_d(tmp, 1) != 0;
74		bignum_deinit(p);
75		bignum_deinit(q);
76		bignum_deinit(tmp);
77		if (failed)
78			goto fail;
79	}
80
81	res = crypto_mod_exp(pubkey, pubkey_len, privkey, privkey_len,
82			     prime, prime_len, secret, len);
83fail:
84	bignum_deinit(pub);
85	return res;
86}
87
88
89int crypto_mod_exp(const u8 *base, size_t base_len,
90		   const u8 *power, size_t power_len,
91		   const u8 *modulus, size_t modulus_len,
92		   u8 *result, size_t *result_len)
93{
94	struct bignum *bn_base, *bn_exp, *bn_modulus, *bn_result;
95	int ret = -1;
96
97	bn_base = bignum_init();
98	bn_exp = bignum_init();
99	bn_modulus = bignum_init();
100	bn_result = bignum_init();
101
102	if (bn_base == NULL || bn_exp == NULL || bn_modulus == NULL ||
103	    bn_result == NULL)
104		goto error;
105
106	if (bignum_set_unsigned_bin(bn_base, base, base_len) < 0 ||
107	    bignum_set_unsigned_bin(bn_exp, power, power_len) < 0 ||
108	    bignum_set_unsigned_bin(bn_modulus, modulus, modulus_len) < 0)
109		goto error;
110
111	if (bignum_exptmod(bn_base, bn_exp, bn_modulus, bn_result) < 0)
112		goto error;
113
114	ret = bignum_get_unsigned_bin(bn_result, result, result_len);
115
116error:
117	bignum_deinit(bn_base);
118	bignum_deinit(bn_exp);
119	bignum_deinit(bn_modulus);
120	bignum_deinit(bn_result);
121	return ret;
122}
123