1 /* 2 * Crypto wrapper for internal crypto implementation - modexp 3 * Copyright (c) 2006-2009, Jouni Malinen <j (at) 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 *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 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
