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 static int generate_key(DH *dh);
66 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh);
67 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
68 const BIGNUM *a, const BIGNUM *p,
69 const BIGNUM *m, BN_CTX *ctx,
70 BN_MONT_CTX *m_ctx);
71 static int dh_init(DH *dh);
72 static int dh_finish(DH *dh);
73
74 int DH_generate_key(DH *dh)
75 {
76 #ifdef OPENSSL_FIPS
77 if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD)
78 && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW))
79 {
80 DHerr(DH_F_DH_GENERATE_KEY, DH_R_NON_FIPS_METHOD);
81 return 0;
82 }
83 #endif
84 return dh->meth->generate_key(dh);
85 }
86
87 int DH_compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
88 {
89 #ifdef OPENSSL_FIPS
90 if (FIPS_mode() && !(dh->meth->flags & DH_FLAG_FIPS_METHOD)
91 && !(dh->flags & DH_FLAG_NON_FIPS_ALLOW))
92 {
93 DHerr(DH_F_DH_COMPUTE_KEY, DH_R_NON_FIPS_METHOD);
94 return 0;
95 }
96 #endif
97 return dh->meth->compute_key(key, pub_key, dh);
98 }
99
100 static DH_METHOD dh_ossl = {
101 "OpenSSL DH Method",
102 generate_key,
103 compute_key,
104 dh_bn_mod_exp,
105 dh_init,
106 dh_finish,
107 0,
108 NULL,
109 NULL
110 };
111
112 const DH_METHOD *DH_OpenSSL(void)
113 {
114 return &dh_ossl;
115 }
116
117 static int generate_key(DH *dh)
118 {
119 int ok=0;
120 int generate_new_key=0;
121 unsigned l;
122 BN_CTX *ctx;
123 BN_MONT_CTX *mont=NULL;
124 BIGNUM *pub_key=NULL,*priv_key=NULL;
125
126 ctx = BN_CTX_new();
127 if (ctx == NULL) goto err;
128
129 if (dh->priv_key == NULL)
130 {
131 priv_key=BN_new();
132 if (priv_key == NULL) goto err;
133 generate_new_key=1;
134 }
135 else
136 priv_key=dh->priv_key;
137
138 if (dh->pub_key == NULL)
139 {
140 pub_key=BN_new();
141 if (pub_key == NULL) goto err;
142 }
143 else
144 pub_key=dh->pub_key;
145
146
147 if (dh->flags & DH_FLAG_CACHE_MONT_P)
148 {
149 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
150 CRYPTO_LOCK_DH, dh->p, ctx);
151 if (!mont)
152 goto err;
153 }
154
155 if (generate_new_key)
156 {
157 if (dh->q)
158 {
159 do
160 {
161 if (!BN_rand_range(priv_key, dh->q))
162 goto err;
163 }
164 while (BN_is_zero(priv_key) || BN_is_one(priv_key));
165 }
166 else
167 {
168 /* secret exponent length */
169 l = dh->length ? dh->length : BN_num_bits(dh->p)-1;
170 if (!BN_rand(priv_key, l, 0, 0)) goto err;
171 }
172 }
173
174 {
175 BIGNUM local_prk;
176 BIGNUM *prk;
177
178 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
179 {
180 BN_init(&local_prk);
181 prk = &local_prk;
182 BN_with_flags(prk, priv_key, BN_FLG_CONSTTIME);
183 }
184 else
185 prk = priv_key;
186
187 if (!dh->meth->bn_mod_exp(dh, pub_key, dh->g, prk, dh->p, ctx, mont)) goto err;
188 }
189
190 dh->pub_key=pub_key;
191 dh->priv_key=priv_key;
192 ok=1;
193 err:
194 if (ok != 1)
195 DHerr(DH_F_GENERATE_KEY,ERR_R_BN_LIB);
196
197 if ((pub_key != NULL) && (dh->pub_key == NULL)) BN_free(pub_key);
198 if ((priv_key != NULL) && (dh->priv_key == NULL)) BN_free(priv_key);
199 BN_CTX_free(ctx);
200 return(ok);
201 }
202
203 static int compute_key(unsigned char *key, const BIGNUM *pub_key, DH *dh)
204 {
205 BN_CTX *ctx=NULL;
206 BN_MONT_CTX *mont=NULL;
207 BIGNUM *tmp;
208 int ret= -1;
209 int check_result;
210
211 if (BN_num_bits(dh->p) > OPENSSL_DH_MAX_MODULUS_BITS)
212 {
213 DHerr(DH_F_COMPUTE_KEY,DH_R_MODULUS_TOO_LARGE);
214 goto err;
215 }
216
217 ctx = BN_CTX_new();
218 if (ctx == NULL) goto err;
219 BN_CTX_start(ctx);
220 tmp = BN_CTX_get(ctx);
221
222 if (dh->priv_key == NULL)
223 {
224 DHerr(DH_F_COMPUTE_KEY,DH_R_NO_PRIVATE_VALUE);
225 goto err;
226 }
227
228 if (dh->flags & DH_FLAG_CACHE_MONT_P)
229 {
230 mont = BN_MONT_CTX_set_locked(&dh->method_mont_p,
231 CRYPTO_LOCK_DH, dh->p, ctx);
232 if ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) == 0)
233 {
234 /* XXX */
235 BN_set_flags(dh->priv_key, BN_FLG_CONSTTIME);
236 }
237 if (!mont)
238 goto err;
239 }
240
241 if (!DH_check_pub_key(dh, pub_key, &check_result) || check_result)
242 {
243 DHerr(DH_F_COMPUTE_KEY,DH_R_INVALID_PUBKEY);
244 goto err;
245 }
246
247 if (!dh->meth->bn_mod_exp(dh, tmp, pub_key, dh->priv_key,dh->p,ctx,mont))
248 {
249 DHerr(DH_F_COMPUTE_KEY,ERR_R_BN_LIB);
250 goto err;
251 }
252
253 ret=BN_bn2bin(tmp,key);
254 err:
255 if (ctx != NULL)
256 {
257 BN_CTX_end(ctx);
258 BN_CTX_free(ctx);
259 }
260 return(ret);
261 }
262
263 static int dh_bn_mod_exp(const DH *dh, BIGNUM *r,
264 const BIGNUM *a, const BIGNUM *p,
265 const BIGNUM *m, BN_CTX *ctx,
266 BN_MONT_CTX *m_ctx)
267 {
268 /* If a is only one word long and constant time is false, use the faster
269 * exponenentiation function.
270 */
271 if (a->top == 1 && ((dh->flags & DH_FLAG_NO_EXP_CONSTTIME) != 0))
272 {
273 BN_ULONG A = a->d[0];
274 return BN_mod_exp_mont_word(r,A,p,m,ctx,m_ctx);
275 }
276 else
277 return BN_mod_exp_mont(r,a,p,m,ctx,m_ctx);
278 }
279
280
281 static int dh_init(DH *dh)
282 {
283 dh->flags |= DH_FLAG_CACHE_MONT_P;
284 return(1);
285 }
286
287 static int dh_finish(DH *dh)
288 {
289 if(dh->method_mont_p)
290 BN_MONT_CTX_free(dh->method_mont_p);
291 return(1);
292 }