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58964a49 | 1 | /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) |
d02b48c6 RE |
2 | * All rights reserved. |
3 | * | |
4 | * This package is an SSL implementation written | |
5 | * by Eric Young (eay@cryptsoft.com). | |
6 | * The implementation was written so as to conform with Netscapes SSL. | |
0f113f3e | 7 | * |
d02b48c6 RE |
8 | * This library is free for commercial and non-commercial use as long as |
9 | * the following conditions are aheared to. The following conditions | |
10 | * apply to all code found in this distribution, be it the RC4, RSA, | |
11 | * lhash, DES, etc., code; not just the SSL code. The SSL documentation | |
12 | * included with this distribution is covered by the same copyright terms | |
13 | * except that the holder is Tim Hudson (tjh@cryptsoft.com). | |
0f113f3e | 14 | * |
d02b48c6 RE |
15 | * Copyright remains Eric Young's, and as such any Copyright notices in |
16 | * the code are not to be removed. | |
17 | * If this package is used in a product, Eric Young should be given attribution | |
18 | * as the author of the parts of the library used. | |
19 | * This can be in the form of a textual message at program startup or | |
20 | * in documentation (online or textual) provided with the package. | |
0f113f3e | 21 | * |
d02b48c6 RE |
22 | * Redistribution and use in source and binary forms, with or without |
23 | * modification, are permitted provided that the following conditions | |
24 | * are met: | |
25 | * 1. Redistributions of source code must retain the copyright | |
26 | * notice, this list of conditions and the following disclaimer. | |
27 | * 2. Redistributions in binary form must reproduce the above copyright | |
28 | * notice, this list of conditions and the following disclaimer in the | |
29 | * documentation and/or other materials provided with the distribution. | |
30 | * 3. All advertising materials mentioning features or use of this software | |
31 | * must display the following acknowledgement: | |
32 | * "This product includes cryptographic software written by | |
33 | * Eric Young (eay@cryptsoft.com)" | |
34 | * The word 'cryptographic' can be left out if the rouines from the library | |
35 | * being used are not cryptographic related :-). | |
0f113f3e | 36 | * 4. If you include any Windows specific code (or a derivative thereof) from |
d02b48c6 RE |
37 | * the apps directory (application code) you must include an acknowledgement: |
38 | * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" | |
0f113f3e | 39 | * |
d02b48c6 RE |
40 | * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND |
41 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE | |
42 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE | |
43 | * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE | |
44 | * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL | |
45 | * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS | |
46 | * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) | |
47 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT | |
48 | * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY | |
49 | * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF | |
50 | * SUCH DAMAGE. | |
0f113f3e | 51 | * |
d02b48c6 RE |
52 | * The licence and distribution terms for any publically available version or |
53 | * derivative of this code cannot be changed. i.e. this code cannot simply be | |
54 | * copied and put under another distribution licence | |
55 | * [including the GNU Public Licence.] | |
56 | */ | |
57 | ||
0f113f3e MC |
58 | /* |
59 | * NB: These functions have been upgraded - the previous prototypes are in | |
60 | * dh_depr.c as wrappers to these ones. - Geoff | |
e9224c71 GT |
61 | */ |
62 | ||
d02b48c6 | 63 | #include <stdio.h> |
b39fc560 | 64 | #include "internal/cryptlib.h" |
ec577822 BM |
65 | #include <openssl/bn.h> |
66 | #include <openssl/dh.h> | |
71fa4513 | 67 | |
0f113f3e MC |
68 | static int dh_builtin_genparams(DH *ret, int prime_len, int generator, |
69 | BN_GENCB *cb); | |
0e4aa0d2 | 70 | |
0f113f3e MC |
71 | int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, |
72 | BN_GENCB *cb) | |
73 | { | |
74 | if (ret->meth->generate_params) | |
75 | return ret->meth->generate_params(ret, prime_len, generator, cb); | |
76 | return dh_builtin_genparams(ret, prime_len, generator, cb); | |
77 | } | |
0e4aa0d2 | 78 | |
1d97c843 TH |
79 | /*- |
80 | * We generate DH parameters as follows | |
d02b48c6 RE |
81 | * find a prime q which is prime_len/2 bits long. |
82 | * p=(2*q)+1 or (p-1)/2 = q | |
83 | * For this case, g is a generator if | |
84 | * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. | |
85 | * Since the factors of p-1 are q and 2, we just need to check | |
86 | * g^2 mod p != 1 and g^q mod p != 1. | |
87 | * | |
88 | * Having said all that, | |
89 | * there is another special case method for the generators 2, 3 and 5. | |
90 | * for 2, p mod 24 == 11 | |
4486d0cd | 91 | * for 3, p mod 12 == 5 <<<<< does not work for safe primes. |
d02b48c6 RE |
92 | * for 5, p mod 10 == 3 or 7 |
93 | * | |
94 | * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the | |
95 | * special generators and for answering some of my questions. | |
96 | * | |
97 | * I've implemented the second simple method :-). | |
4486d0cd | 98 | * Since DH should be using a safe prime (both p and q are prime), |
d02b48c6 RE |
99 | * this generator function can take a very very long time to run. |
100 | */ | |
0f113f3e MC |
101 | /* |
102 | * Actually there is no reason to insist that 'generator' be a generator. | |
82652aaf BM |
103 | * It's just as OK (and in some sense better) to use a generator of the |
104 | * order-q subgroup. | |
105 | */ | |
0f113f3e MC |
106 | static int dh_builtin_genparams(DH *ret, int prime_len, int generator, |
107 | BN_GENCB *cb) | |
108 | { | |
109 | BIGNUM *t1, *t2; | |
110 | int g, ok = -1; | |
111 | BN_CTX *ctx = NULL; | |
d02b48c6 | 112 | |
0f113f3e MC |
113 | ctx = BN_CTX_new(); |
114 | if (ctx == NULL) | |
115 | goto err; | |
116 | BN_CTX_start(ctx); | |
117 | t1 = BN_CTX_get(ctx); | |
118 | t2 = BN_CTX_get(ctx); | |
119 | if (t1 == NULL || t2 == NULL) | |
120 | goto err; | |
e9224c71 | 121 | |
0f113f3e MC |
122 | /* Make sure 'ret' has the necessary elements */ |
123 | if (!ret->p && ((ret->p = BN_new()) == NULL)) | |
124 | goto err; | |
125 | if (!ret->g && ((ret->g = BN_new()) == NULL)) | |
126 | goto err; | |
127 | ||
128 | if (generator <= 1) { | |
129 | DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_BAD_GENERATOR); | |
130 | goto err; | |
131 | } | |
132 | if (generator == DH_GENERATOR_2) { | |
133 | if (!BN_set_word(t1, 24)) | |
134 | goto err; | |
135 | if (!BN_set_word(t2, 11)) | |
136 | goto err; | |
137 | g = 2; | |
dfb56425 | 138 | } else if (generator == DH_GENERATOR_5) { |
0f113f3e MC |
139 | if (!BN_set_word(t1, 10)) |
140 | goto err; | |
141 | if (!BN_set_word(t2, 3)) | |
142 | goto err; | |
143 | /* | |
144 | * BN_set_word(t3,7); just have to miss out on these ones :-( | |
145 | */ | |
146 | g = 5; | |
147 | } else { | |
148 | /* | |
149 | * in the general case, don't worry if 'generator' is a generator or | |
150 | * not: since we are using safe primes, it will generate either an | |
151 | * order-q or an order-2q group, which both is OK | |
152 | */ | |
153 | if (!BN_set_word(t1, 2)) | |
154 | goto err; | |
155 | if (!BN_set_word(t2, 1)) | |
156 | goto err; | |
157 | g = generator; | |
158 | } | |
159 | ||
160 | if (!BN_generate_prime_ex(ret->p, prime_len, 1, t1, t2, cb)) | |
161 | goto err; | |
162 | if (!BN_GENCB_call(cb, 3, 0)) | |
163 | goto err; | |
164 | if (!BN_set_word(ret->g, g)) | |
165 | goto err; | |
166 | ok = 1; | |
167 | err: | |
168 | if (ok == -1) { | |
169 | DHerr(DH_F_DH_BUILTIN_GENPARAMS, ERR_R_BN_LIB); | |
170 | ok = 0; | |
171 | } | |
d02b48c6 | 172 | |
0f113f3e MC |
173 | if (ctx != NULL) { |
174 | BN_CTX_end(ctx); | |
175 | BN_CTX_free(ctx); | |
176 | } | |
177 | return ok; | |
178 | } |