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
crypto_dh_init(u8 generator,const u8 * prime,size_t prime_len,u8 * privkey,u8 * pubkey)16 int 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
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)42 int 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);
83 fail:
84 bignum_deinit(pub);
85 return res;
86 }
87
88
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)89 int 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
116 error:
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