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 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 42 int crypto_dh_derive_secret(u8 generator, const u8 *prime, size_t prime_len, 43 const u8 *privkey, size_t privkey_len, 44 const u8 *pubkey, size_t pubkey_len, 45 u8 *secret, size_t *len) 46 { 47 return crypto_mod_exp(pubkey, pubkey_len, privkey, privkey_len, 48 prime, prime_len, secret, len); 49 } 50 51 52 int crypto_mod_exp(const u8 *base, size_t base_len, 53 const u8 *power, size_t power_len, 54 const u8 *modulus, size_t modulus_len, 55 u8 *result, size_t *result_len) 56 { 57 struct bignum *bn_base, *bn_exp, *bn_modulus, *bn_result; 58 int ret = -1; 59 60 bn_base = bignum_init(); 61 bn_exp = bignum_init(); 62 bn_modulus = bignum_init(); 63 bn_result = bignum_init(); 64 65 if (bn_base == NULL || bn_exp == NULL || bn_modulus == NULL || 66 bn_result == NULL) 67 goto error; 68 69 if (bignum_set_unsigned_bin(bn_base, base, base_len) < 0 || 70 bignum_set_unsigned_bin(bn_exp, power, power_len) < 0 || 71 bignum_set_unsigned_bin(bn_modulus, modulus, modulus_len) < 0) 72 goto error; 73 74 if (bignum_exptmod(bn_base, bn_exp, bn_modulus, bn_result) < 0) 75 goto error; 76 77 ret = bignum_get_unsigned_bin(bn_result, result, result_len); 78 79 error: 80 bignum_deinit(bn_base); 81 bignum_deinit(bn_exp); 82 bignum_deinit(bn_modulus); 83 bignum_deinit(bn_result); 84 return ret; 85 } 86