1 /* Copyright (C) 1995-1998 Eric Young (eay (at) cryptsoft.com) 2 * All rights reserved. 3 * 4 * This package is an SSL implementation written 5 * by Eric Young (eay (at) cryptsoft.com). 6 * The implementation was written so as to conform with Netscapes SSL. 7 * 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 (at) cryptsoft.com). 14 * 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. 21 * 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 (at) cryptsoft.com)" 34 * The word 'cryptographic' can be left out if the rouines from the library 35 * being used are not cryptographic related :-). 36 * 4. If you include any Windows specific code (or a derivative thereof) from 37 * the apps directory (application code) you must include an acknowledgement: 38 * "This product includes software written by Tim Hudson (tjh (at) cryptsoft.com)" 39 * 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. 51 * 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 #include <openssl/dh.h> 58 59 #include <openssl/bn.h> 60 61 #include "internal.h" 62 63 64 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) { 65 int ok = 0; 66 BIGNUM q; 67 68 *ret = 0; 69 BN_init(&q); 70 if (!BN_set_word(&q, 1)) { 71 goto err; 72 } 73 74 if (BN_cmp(pub_key, &q) <= 0) { 75 *ret |= DH_CHECK_PUBKEY_TOO_SMALL; 76 } 77 if (!BN_copy(&q, dh->p) || 78 !BN_sub_word(&q, 1)) { 79 goto err; 80 } 81 if (BN_cmp(pub_key, &q) >= 0) { 82 *ret |= DH_CHECK_PUBKEY_TOO_LARGE; 83 } 84 85 ok = 1; 86 87 err: 88 BN_free(&q); 89 return ok; 90 } 91 92 93 int DH_check(const DH *dh, int *ret) { 94 /* Check that p is a safe prime and if g is 2, 3 or 5, check that it is a 95 * suitable generator where: 96 * for 2, p mod 24 == 11 97 * for 3, p mod 12 == 5 98 * for 5, p mod 10 == 3 or 7 99 * should hold. 100 */ 101 int ok = 0; 102 BN_CTX *ctx = NULL; 103 BN_ULONG l; 104 BIGNUM *t1 = NULL, *t2 = NULL; 105 106 *ret = 0; 107 ctx = BN_CTX_new(); 108 if (ctx == NULL) { 109 goto err; 110 } 111 BN_CTX_start(ctx); 112 t1 = BN_CTX_get(ctx); 113 if (t1 == NULL) { 114 goto err; 115 } 116 t2 = BN_CTX_get(ctx); 117 if (t2 == NULL) { 118 goto err; 119 } 120 121 if (dh->q) { 122 if (BN_cmp(dh->g, BN_value_one()) <= 0) { 123 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 124 } else if (BN_cmp(dh->g, dh->p) >= 0) { 125 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 126 } else { 127 /* Check g^q == 1 mod p */ 128 if (!BN_mod_exp(t1, dh->g, dh->q, dh->p, ctx)) { 129 goto err; 130 } 131 if (!BN_is_one(t1)) { 132 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 133 } 134 } 135 if (!BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL)) { 136 *ret |= DH_CHECK_Q_NOT_PRIME; 137 } 138 /* Check p == 1 mod q i.e. q divides p - 1 */ 139 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) { 140 goto err; 141 } 142 if (!BN_is_one(t2)) { 143 *ret |= DH_CHECK_INVALID_Q_VALUE; 144 } 145 if (dh->j && BN_cmp(dh->j, t1)) { 146 *ret |= DH_CHECK_INVALID_J_VALUE; 147 } 148 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) { 149 l = BN_mod_word(dh->p, 24); 150 if (l != 11) { 151 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 152 } 153 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) { 154 l = BN_mod_word(dh->p, 10); 155 if (l != 3 && l != 7) { 156 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 157 } 158 } else { 159 *ret |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR; 160 } 161 162 if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL)) { 163 *ret |= DH_CHECK_P_NOT_PRIME; 164 } else if (!dh->q) { 165 if (!BN_rshift1(t1, dh->p)) { 166 goto err; 167 } 168 if (!BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL)) { 169 *ret |= DH_CHECK_P_NOT_SAFE_PRIME; 170 } 171 } 172 ok = 1; 173 174 err: 175 if (ctx != NULL) { 176 BN_CTX_end(ctx); 177 BN_CTX_free(ctx); 178 } 179 return ok; 180 } 181
