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1 : : /* crypto/dh/dh_gen.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 : : /* NB: These functions have been upgraded - the previous prototypes are in
60 : : * dh_depr.c as wrappers to these ones.
61 : : * - Geoff
62 : : */
63 : :
64 : : #define OPENSSL_FIPSAPI
65 : :
66 : : #include <stdio.h>
67 : : #include "cryptlib.h"
68 : : #include <openssl/bn.h>
69 : : #include <openssl/dh.h>
70 : :
71 : : #ifdef OPENSSL_FIPS
72 : : #include <openssl/fips.h>
73 : : #endif
74 : :
75 : : static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb);
76 : :
77 : 1 : int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, BN_GENCB *cb)
78 : : {
79 [ - + ]: 1 : if(ret->meth->generate_params)
80 : 0 : return ret->meth->generate_params(ret, prime_len, generator, cb);
81 : 1 : return dh_builtin_genparams(ret, prime_len, generator, cb);
82 : : }
83 : :
84 : : /* We generate DH parameters as follows
85 : : * find a prime q which is prime_len/2 bits long.
86 : : * p=(2*q)+1 or (p-1)/2 = q
87 : : * For this case, g is a generator if
88 : : * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1.
89 : : * Since the factors of p-1 are q and 2, we just need to check
90 : : * g^2 mod p != 1 and g^q mod p != 1.
91 : : *
92 : : * Having said all that,
93 : : * there is another special case method for the generators 2, 3 and 5.
94 : : * for 2, p mod 24 == 11
95 : : * for 3, p mod 12 == 5 <<<<< does not work for safe primes.
96 : : * for 5, p mod 10 == 3 or 7
97 : : *
98 : : * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the
99 : : * special generators and for answering some of my questions.
100 : : *
101 : : * I've implemented the second simple method :-).
102 : : * Since DH should be using a safe prime (both p and q are prime),
103 : : * this generator function can take a very very long time to run.
104 : : */
105 : : /* Actually there is no reason to insist that 'generator' be a generator.
106 : : * It's just as OK (and in some sense better) to use a generator of the
107 : : * order-q subgroup.
108 : : */
109 : 2 : static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb)
110 : : {
111 : : BIGNUM *t1,*t2;
112 : 1 : int g,ok= -1;
113 : 1 : BN_CTX *ctx=NULL;
114 : :
115 : : #ifdef OPENSSL_FIPS
116 : : if(FIPS_selftest_failed())
117 : : {
118 : : FIPSerr(FIPS_F_DH_BUILTIN_GENPARAMS,FIPS_R_FIPS_SELFTEST_FAILED);
119 : : return 0;
120 : : }
121 : :
122 : : if (FIPS_module_mode() && (prime_len < OPENSSL_DH_FIPS_MIN_MODULUS_BITS))
123 : : {
124 : : DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_KEY_SIZE_TOO_SMALL);
125 : : goto err;
126 : : }
127 : : #endif
128 : :
129 : 1 : ctx=BN_CTX_new();
130 [ + - ]: 1 : if (ctx == NULL) goto err;
131 : 1 : BN_CTX_start(ctx);
132 : 1 : t1 = BN_CTX_get(ctx);
133 : 1 : t2 = BN_CTX_get(ctx);
134 [ + - ]: 1 : if (t1 == NULL || t2 == NULL) goto err;
135 : :
136 : : /* Make sure 'ret' has the necessary elements */
137 [ + - ][ + - ]: 1 : if(!ret->p && ((ret->p = BN_new()) == NULL)) goto err;
138 [ + - ][ + - ]: 1 : if(!ret->g && ((ret->g = BN_new()) == NULL)) goto err;
139 : :
140 [ - + ]: 1 : if (generator <= 1)
141 : : {
142 : 0 : DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_BAD_GENERATOR);
143 : : goto err;
144 : : }
145 [ - + ]: 1 : if (generator == DH_GENERATOR_2)
146 : : {
147 [ # # ]: 0 : if (!BN_set_word(t1,24)) goto err;
148 [ # # ]: 0 : if (!BN_set_word(t2,11)) goto err;
149 : : g=2;
150 : : }
151 : : #if 0 /* does not work for safe primes */
152 : : else if (generator == DH_GENERATOR_3)
153 : : {
154 : : if (!BN_set_word(t1,12)) goto err;
155 : : if (!BN_set_word(t2,5)) goto err;
156 : : g=3;
157 : : }
158 : : #endif
159 [ + - ]: 1 : else if (generator == DH_GENERATOR_5)
160 : : {
161 [ + - ]: 1 : if (!BN_set_word(t1,10)) goto err;
162 [ + - ]: 1 : if (!BN_set_word(t2,3)) goto err;
163 : : /* BN_set_word(t3,7); just have to miss
164 : : * out on these ones :-( */
165 : : g=5;
166 : : }
167 : : else
168 : : {
169 : : /* in the general case, don't worry if 'generator' is a
170 : : * generator or not: since we are using safe primes,
171 : : * it will generate either an order-q or an order-2q group,
172 : : * which both is OK */
173 [ # # ]: 0 : if (!BN_set_word(t1,2)) goto err;
174 [ # # ]: 0 : if (!BN_set_word(t2,1)) goto err;
175 : : g=generator;
176 : : }
177 : :
178 [ + - ]: 1 : if(!BN_generate_prime_ex(ret->p,prime_len,1,t1,t2,cb)) goto err;
179 [ + - ]: 1 : if(!BN_GENCB_call(cb, 3, 0)) goto err;
180 [ + - ]: 1 : if (!BN_set_word(ret->g,g)) goto err;
181 : 1 : ok=1;
182 : : err:
183 [ - + ]: 1 : if (ok == -1)
184 : : {
185 : 0 : DHerr(DH_F_DH_BUILTIN_GENPARAMS,ERR_R_BN_LIB);
186 : 0 : ok=0;
187 : : }
188 : :
189 [ + - ]: 1 : if (ctx != NULL)
190 : : {
191 : 1 : BN_CTX_end(ctx);
192 : 1 : BN_CTX_free(ctx);
193 : : }
194 : 1 : return ok;
195 : : }
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