[331] | 1 | /*
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| 2 | * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
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| 3 | *
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| 4 | * Licensed under the OpenSSL license (the "License"). You may not use
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| 5 | * this file except in compliance with the License. You can obtain a copy
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| 6 | * in the file LICENSE in the source distribution or at
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| 7 | * https://www.openssl.org/source/license.html
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| 8 | */
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| 9 |
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| 10 | #include <stdio.h>
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| 11 | #include "internal/cryptlib.h"
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| 12 | #include "dh_locl.h"
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| 13 | #include "internal/bn_int.h"
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| 14 |
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| 15 | static int generate_key(DH *dh);
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| 16 | static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
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| 17 | static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
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| 18 | const BIGNUM *a, const BIGNUM *p,
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| 19 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
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| 20 | static int dh_init(DH *dh);
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| 21 | static int dh_finish(DH *dh);
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| 22 |
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| 23 | int DH_generate_key(DH *dh)
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| 24 | {
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| 25 | return dh->meth->generate_key(dh);
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| 26 | }
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| 27 |
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| 28 | int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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| 29 | {
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| 30 | return dh->meth->compute_key(key, pub_key, dh);
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| 31 | }
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| 32 |
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| 33 | int DH_compute_key_padded(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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| 34 | {
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| 35 | int rv, pad;
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| 36 | rv = dh->meth->compute_key(key, pub_key, dh);
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| 37 | if (rv <= 0)
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| 38 | return rv;
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| 39 | pad = BN_num_bytes(dh->p) - rv;
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| 40 | if (pad > 0) {
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| 41 | memmove(key + pad, key, rv);
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| 42 | memset(key, 0, pad);
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| 43 | }
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| 44 | return rv + pad;
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| 45 | }
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| 46 |
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| 47 | static DH_METHOD dh_ossl = {
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| 48 | "OpenSSL DH Method",
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| 49 | generate_key,
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| 50 | compute_key,
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| 51 | dh_bn_mod_exp,
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| 52 | dh_init,
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| 53 | dh_finish,
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| 54 | DH_FLAG_FIPS_METHOD,
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| 55 | NULL,
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| 56 | NULL
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| 57 | };
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| 58 |
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| 59 | const DH_METHOD *DH_OpenSSL(void)
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| 60 | {
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| 61 | return &dh_ossl;
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| 62 | }
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| 63 |
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| 64 | static int generate_key(DH *dh)
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| 65 | {
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| 66 | int ok = 0;
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| 67 | int generate_new_key = 0;
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| 68 | unsigned l;
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| 69 | BN_CTX *ctx;
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| 70 | BN_MONT_CTX *mont = NULL;
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| 71 | BIGNUM *pub_key = NULL, *priv_key = NULL;
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| 72 |
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| 73 | ctx = BN_CTX_new();
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| 74 | if (ctx == NULL)
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| 75 | goto err;
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| 76 |
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| 77 | if (dh->priv_key == NULL) {
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| 78 | priv_key = BN_secure_new();
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| 79 | if (priv_key == NULL)
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| 80 | goto err;
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| 81 | generate_new_key = 1;
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| 82 | } else
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| 83 | priv_key = dh->priv_key;
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| 84 |
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| 85 | if (dh->pub_key == NULL) {
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| 86 | pub_key = BN_new();
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| 87 | if (pub_key == NULL)
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| 88 | goto err;
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| 89 | } else
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| 90 | pub_key = dh->pub_key;
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| 91 |
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| 92 | if (dh->flags & DH_FLAG_CACHE_MONT_P) {
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| 93 | mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
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| 94 | dh->lock, dh->p, ctx);
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| 95 | if (!mont)
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| 96 | goto err;
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| 97 | }
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| 98 |
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| 99 | if (generate_new_key) {
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| 100 | if (dh->q) {
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| 101 | do {
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| 102 | if (!BN_rand_range(priv_key, dh->q))
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| 103 | goto err;
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| 104 | }
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| 105 | while (BN_is_zero(priv_key) || BN_is_one(priv_key));
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| 106 | } else {
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| 107 | /* secret exponent length */
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| 108 | l = dh->length ? dh->length : BN_num_bits(dh->p) - 1;
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| 109 | if (!BN_rand(priv_key, l, BN_RAND_TOP_ONE, BN_RAND_BOTTOM_ANY))
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| 110 | goto err;
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| 111 | }
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| 112 | }
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| 113 |
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| 114 | {
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| 115 | BIGNUM *prk = BN_new();
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| 116 |
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| 117 | if (prk == NULL)
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| 118 | goto err;
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| 119 | BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
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| 120 |
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| 121 | if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) {
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| 122 | BN_free(prk);
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| 123 | goto err;
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| 124 | }
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| 125 | /* We MUST free prk before any further use of priv_key */
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| 126 | BN_free(prk);
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| 127 | }
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| 128 |
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| 129 | dh->pub_key = pub_key;
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| 130 | dh->priv_key = priv_key;
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| 131 | ok = 1;
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| 132 | err:
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| 133 | if (ok != 1)
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| 134 | DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
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| 135 |
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| 136 | if (pub_key != dh->pub_key)
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| 137 | BN_free(pub_key);
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| 138 | if (priv_key != dh->priv_key)
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| 139 | BN_free(priv_key);
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| 140 | BN_CTX_free(ctx);
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| 141 | return (ok);
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| 142 | }
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| 143 |
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| 144 | static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
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| 145 | {
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| 146 | BN_CTX *ctx = NULL;
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| 147 | BN_MONT_CTX *mont = NULL;
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| 148 | BIGNUM *tmp;
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| 149 | int ret = -1;
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| 150 | int check_result;
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| 151 |
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| 152 | if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
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| 153 | DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
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| 154 | goto err;
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| 155 | }
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| 156 |
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| 157 | ctx = BN_CTX_new();
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| 158 | if (ctx == NULL)
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| 159 | goto err;
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| 160 | BN_CTX_start(ctx);
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| 161 | tmp = BN_CTX_get(ctx);
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| 162 | if (tmp == NULL)
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| 163 | goto err;
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| 164 |
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| 165 | if (dh->priv_key == NULL) {
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| 166 | DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
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| 167 | goto err;
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| 168 | }
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| 169 |
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| 170 | if (dh->flags & DH_FLAG_CACHE_MONT_P) {
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| 171 | mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
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| 172 | dh->lock, dh->p, ctx);
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| 173 | BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
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| 174 | if (!mont)
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| 175 | goto err;
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| 176 | }
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| 177 |
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| 178 | if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
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| 179 | DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
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| 180 | goto err;
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| 181 | }
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| 182 |
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| 183 | if (!dh->
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| 184 | meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
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| 185 | DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
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| 186 | goto err;
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| 187 | }
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| 188 |
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| 189 | ret = BN_bn2bin(tmp, key);
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| 190 | err:
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| 191 | if (ctx != NULL) {
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| 192 | BN_CTX_end(ctx);
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| 193 | BN_CTX_free(ctx);
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| 194 | }
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| 195 | return (ret);
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| 196 | }
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| 197 |
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| 198 | static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
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| 199 | const BIGNUM *a, const BIGNUM *p,
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| 200 | const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
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| 201 | {
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| 202 | return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
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| 203 | }
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| 204 |
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| 205 | static int dh_init(DH *dh)
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| 206 | {
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| 207 | dh->flags |= DH_FLAG_CACHE_MONT_P;
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| 208 | return (1);
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| 209 | }
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| 210 |
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| 211 | static int dh_finish(DH *dh)
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| 212 | {
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| 213 | BN_MONT_CTX_free(dh->method_mont_p);
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| 214 | return (1);
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| 215 | }
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