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