dh_key.c revision 296465 
1/* crypto/dh/dh_key.c */
2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
3 * All rights reserved.
4 *
5 * This package is an SSL implementation written
6 * by Eric Young (eay@cryptsoft.com).
7 * The implementation was written so as to conform with Netscapes SSL.
8 *
9 * This library is free for commercial and non-commercial use as long as
10 * the following conditions are aheared to.  The following conditions
11 * apply to all code found in this distribution, be it the RC4, RSA,
12 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
13 * included with this distribution is covered by the same copyright terms
14 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
15 *
16 * Copyright remains Eric Young's, and as such any Copyright notices in
17 * the code are not to be removed.
18 * If this package is used in a product, Eric Young should be given attribution
19 * as the author of the parts of the library used.
20 * This can be in the form of a textual message at program startup or
21 * in documentation (online or textual) provided with the package.
22 *
23 * Redistribution and use in source and binary forms, with or without
24 * modification, are permitted provided that the following conditions
25 * are met:
26 * 1. Redistributions of source code must retain the copyright
27 *    notice, this list of conditions and the following disclaimer.
28 * 2. Redistributions in binary form must reproduce the above copyright
29 *    notice, this list of conditions and the following disclaimer in the
30 *    documentation and/or other materials provided with the distribution.
31 * 3. All advertising materials mentioning features or use of this software
32 *    must display the following acknowledgement:
33 *    "This product includes cryptographic software written by
34 *     Eric Young (eay@cryptsoft.com)"
35 *    The word 'cryptographic' can be left out if the rouines from the library
36 *    being used are not cryptographic related :-).
37 * 4. If you include any Windows specific code (or a derivative thereof) from
38 *    the apps directory (application code) you must include an acknowledgement:
39 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
40 *
41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
44 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
51 * SUCH DAMAGE.
52 *
53 * The licence and distribution terms for any publically available version or
54 * derivative of this code cannot be changed.  i.e. this code cannot simply be
55 * copied and put under another distribution licence
56 * [including the GNU Public Licence.]
57 */
58
59#include <stdio.h>
60#include "cryptlib.h"
61#include <openssl/bn.h>
62#include <openssl/rand.h>
63#include <openssl/dh.h>
64
65#ifndef OPENSSL_FIPS
66
67static int generate_key(DH *dh);
68static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
69static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
70                         const BIGNUM *a, const BIGNUM *p,
71                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
72static int dh_init(DH *dh);
73static int dh_finish(DH *dh);
74
75int DH_generate_key(DH *dh)
76{
77    return dh->meth->generate_key(dh);
78}
79
80int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
81{
82    return dh->meth->compute_key(key, pub_key, dh);
83}
84
85static DH_METHOD dh_ossl = {
86    "OpenSSL DH Method",
87    generate_key,
88    compute_key,
89    dh_bn_mod_exp,
90    dh_init,
91    dh_finish,
92    0,
93    NULL,
94    NULL
95};
96
97const DH_METHOD *DH_OpenSSL(void)
98{
99    return &dh_ossl;
100}
101
102static int generate_key(DH *dh)
103{
104    int ok = 0;
105    int generate_new_key = 0;
106    unsigned l;
107    BN_CTX *ctx;
108    BN_MONT_CTX *mont = NULL;
109    BIGNUM *pub_key = NULL, *priv_key = NULL;
110
111    ctx = BN_CTX_new();
112    if (ctx == NULL)
113        goto err;
114
115    if (dh->priv_key == NULL) {
116        priv_key = BN_new();
117        if (priv_key == NULL)
118            goto err;
119        generate_new_key = 1;
120    } else
121        priv_key = dh->priv_key;
122
123    if (dh->pub_key == NULL) {
124        pub_key = BN_new();
125        if (pub_key == NULL)
126            goto err;
127    } else
128        pub_key = dh->pub_key;
129
130    if (dh->flags & DH_FLAG_CACHE_MONT_P) {
131        mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
132                                      CRYPTO_LOCK_DH, dh->p, ctx);
133        if (!mont)
134            goto err;
135    }
136
137    if (generate_new_key) {
138        l = dh->length ? dh->length : BN_num_bits(dh->p) - 1; /* secret
139                                                               * exponent
140                                                               * length */
141        if (!BN_rand(priv_key, l, 0, 0))
142            goto err;
143    }
144
145    {
146        BIGNUM local_prk;
147        BIGNUM *prk;
148
149        if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
150            BN_init(&local_prk);
151            prk = &local_prk;
152            BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
153        } else
154            prk = priv_key;
155
156        if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont))
157            goto err;
158    }
159
160    dh->pub_key = pub_key;
161    dh->priv_key = priv_key;
162    ok = 1;
163 err:
164    if (ok != 1)
165        DHerr(DH_F_GENERATE_KEY, ERR_R_BN_LIB);
166
167    if ((pub_key != NULL) && (dh->pub_key == NULL))
168        BN_free(pub_key);
169    if ((priv_key != NULL) && (dh->priv_key == NULL))
170        BN_free(priv_key);
171    BN_CTX_free(ctx);
172    return (ok);
173}
174
175static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
176{
177    BN_CTX *ctx = NULL;
178    BN_MONT_CTX *mont = NULL;
179    BIGNUM *tmp;
180    int ret = -1;
181    int check_result;
182
183    if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS) {
184        DHerr(DH_F_COMPUTE_KEY, DH_R_MODULUS_TOO_LARGE);
185        goto err;
186    }
187
188    ctx = BN_CTX_new();
189    if (ctx == NULL)
190        goto err;
191    BN_CTX_start(ctx);
192    tmp = BN_CTX_get(ctx);
193
194    if (dh->priv_key == NULL) {
195        DHerr(DH_F_COMPUTE_KEY, DH_R_NO_PRIVATE_VALUE);
196        goto err;
197    }
198
199    if (dh->flags & DH_FLAG_CACHE_MONT_P) {
200        mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
201                                      CRYPTO_LOCK_DH, dh->p, ctx);
202        if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0) {
203            /* XXX */
204            BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
205        }
206        if (!mont)
207            goto err;
208    }
209
210    if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result) {
211        DHerr(DH_F_COMPUTE_KEY, DH_R_INVALID_PUBKEY);
212        goto err;
213    }
214
215    if (!dh->
216        meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key, dh->p, ctx, mont)) {
217        DHerr(DH_F_COMPUTE_KEY, ERR_R_BN_LIB);
218        goto err;
219    }
220
221    ret = BN_bn2bin(tmp, key);
222 err:
223    if (ctx != NULL) {
224        BN_CTX_end(ctx);
225        BN_CTX_free(ctx);
226    }
227    return (ret);
228}
229
230static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
231                         const BIGNUM *a, const BIGNUM *p,
232                         const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
233{
234    /*
235     * If a is only one word long and constant time is false, use the faster
236     * exponenentiation function.
237     */
238    if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0)) {
239        BN_ULONG A = a->d[0];
240        return BN_mod_exp_mont_word(r, A, p, m, ctx, m_ctx);
241    } else
242        return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
243}
244
245static int dh_init(DH *dh)
246{
247    dh->flags |= DH_FLAG_CACHE_MONT_P;
248    return (1);
249}
250
251static int dh_finish(DH *dh)
252{
253    if (dh->method_mont_p)
254        BN_MONT_CTX_free(dh->method_mont_p);
255    return (1);
256}
257
258#endif
259