Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 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 | #include <stdio.h> |
| 65 | #include "cryptlib.h" |
| 66 | #include <openssl/bn.h> |
| 67 | #include <openssl/dh.h> |
| 68 | |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 69 | static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb); |
| 70 | |
| 71 | int DH_generate_parameters_ex(DH *ret, int prime_len, int generator, BN_GENCB *cb) |
| 72 | { |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 73 | if(ret->meth->generate_params) |
| 74 | return ret->meth->generate_params(ret, prime_len, generator, cb); |
Alexandre Savard | 1b09e31 | 2012-08-07 20:33:29 -0400 | [diff] [blame] | 75 | return dh_builtin_genparams(ret, prime_len, generator, cb); |
| 76 | } |
| 77 | |
| 78 | /* We generate DH parameters as follows |
| 79 | * find a prime q which is prime_len/2 bits long. |
| 80 | * p=(2*q)+1 or (p-1)/2 = q |
| 81 | * For this case, g is a generator if |
| 82 | * g^((p-1)/q) mod p != 1 for values of q which are the factors of p-1. |
| 83 | * Since the factors of p-1 are q and 2, we just need to check |
| 84 | * g^2 mod p != 1 and g^q mod p != 1. |
| 85 | * |
| 86 | * Having said all that, |
| 87 | * there is another special case method for the generators 2, 3 and 5. |
| 88 | * for 2, p mod 24 == 11 |
| 89 | * for 3, p mod 12 == 5 <<<<< does not work for safe primes. |
| 90 | * for 5, p mod 10 == 3 or 7 |
| 91 | * |
| 92 | * Thanks to Phil Karn <karn@qualcomm.com> for the pointers about the |
| 93 | * special generators and for answering some of my questions. |
| 94 | * |
| 95 | * I've implemented the second simple method :-). |
| 96 | * Since DH should be using a safe prime (both p and q are prime), |
| 97 | * this generator function can take a very very long time to run. |
| 98 | */ |
| 99 | /* Actually there is no reason to insist that 'generator' be a generator. |
| 100 | * It's just as OK (and in some sense better) to use a generator of the |
| 101 | * order-q subgroup. |
| 102 | */ |
| 103 | static int dh_builtin_genparams(DH *ret, int prime_len, int generator, BN_GENCB *cb) |
| 104 | { |
| 105 | BIGNUM *t1,*t2; |
| 106 | int g,ok= -1; |
| 107 | BN_CTX *ctx=NULL; |
| 108 | |
| 109 | ctx=BN_CTX_new(); |
| 110 | if (ctx == NULL) goto err; |
| 111 | BN_CTX_start(ctx); |
| 112 | t1 = BN_CTX_get(ctx); |
| 113 | t2 = BN_CTX_get(ctx); |
| 114 | if (t1 == NULL || t2 == NULL) goto err; |
| 115 | |
| 116 | /* Make sure 'ret' has the necessary elements */ |
| 117 | if(!ret->p && ((ret->p = BN_new()) == NULL)) goto err; |
| 118 | if(!ret->g && ((ret->g = BN_new()) == NULL)) goto err; |
| 119 | |
| 120 | if (generator <= 1) |
| 121 | { |
| 122 | DHerr(DH_F_DH_BUILTIN_GENPARAMS, DH_R_BAD_GENERATOR); |
| 123 | goto err; |
| 124 | } |
| 125 | if (generator == DH_GENERATOR_2) |
| 126 | { |
| 127 | if (!BN_set_word(t1,24)) goto err; |
| 128 | if (!BN_set_word(t2,11)) goto err; |
| 129 | g=2; |
| 130 | } |
| 131 | #if 0 /* does not work for safe primes */ |
| 132 | else if (generator == DH_GENERATOR_3) |
| 133 | { |
| 134 | if (!BN_set_word(t1,12)) goto err; |
| 135 | if (!BN_set_word(t2,5)) goto err; |
| 136 | g=3; |
| 137 | } |
| 138 | #endif |
| 139 | else if (generator == DH_GENERATOR_5) |
| 140 | { |
| 141 | if (!BN_set_word(t1,10)) goto err; |
| 142 | if (!BN_set_word(t2,3)) goto err; |
| 143 | /* BN_set_word(t3,7); just have to miss |
| 144 | * out on these ones :-( */ |
| 145 | g=5; |
| 146 | } |
| 147 | else |
| 148 | { |
| 149 | /* in the general case, don't worry if 'generator' is a |
| 150 | * generator or not: since we are using safe primes, |
| 151 | * it will generate either an order-q or an order-2q group, |
| 152 | * which both is OK */ |
| 153 | if (!BN_set_word(t1,2)) goto err; |
| 154 | if (!BN_set_word(t2,1)) goto err; |
| 155 | g=generator; |
| 156 | } |
| 157 | |
| 158 | if(!BN_generate_prime_ex(ret->p,prime_len,1,t1,t2,cb)) goto err; |
| 159 | if(!BN_GENCB_call(cb, 3, 0)) goto err; |
| 160 | if (!BN_set_word(ret->g,g)) goto err; |
| 161 | ok=1; |
| 162 | err: |
| 163 | if (ok == -1) |
| 164 | { |
| 165 | DHerr(DH_F_DH_BUILTIN_GENPARAMS,ERR_R_BN_LIB); |
| 166 | ok=0; |
| 167 | } |
| 168 | |
| 169 | if (ctx != NULL) |
| 170 | { |
| 171 | BN_CTX_end(ctx); |
| 172 | BN_CTX_free(ctx); |
| 173 | } |
| 174 | return ok; |
| 175 | } |