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 62 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) { 63 *ret = 0; 64 65 BN_CTX *ctx = BN_CTX_new(); 66 if (ctx == NULL) { 67 return 0; 68 } 69 BN_CTX_start(ctx); 70 71 int ok = 0; 72 73 /* Check |pub_key| is greater than 1. */ 74 BIGNUM *tmp = BN_CTX_get(ctx); 75 if (tmp == NULL || 76 !BN_set_word(tmp, 1)) { 77 goto err; 78 } 79 if (BN_cmp(pub_key, tmp) <= 0) { 80 *ret |= DH_CHECK_PUBKEY_TOO_SMALL; 81 } 82 83 /* Check |pub_key| is less than |dh->p| - 1. */ 84 if (!BN_copy(tmp, dh->p) || 85 !BN_sub_word(tmp, 1)) { 86 goto err; 87 } 88 if (BN_cmp(pub_key, tmp) >= 0) { 89 *ret |= DH_CHECK_PUBKEY_TOO_LARGE; 90 } 91 92 if (dh->q != NULL) { 93 /* Check |pub_key|^|dh->q| is 1 mod |dh->p|. This is necessary for RFC 5114 94 * groups which are not safe primes but pick a generator on a prime-order 95 * subgroup of size |dh->q|. */ 96 if (!BN_mod_exp_mont(tmp, pub_key, dh->q, dh->p, ctx, NULL)) { 97 goto err; 98 } 99 if (!BN_is_one(tmp)) { 100 *ret |= DH_CHECK_PUBKEY_INVALID; 101 } 102 } 103 104 ok = 1; 105 106 err: 107 BN_CTX_end(ctx); 108 BN_CTX_free(ctx); 109 return ok; 110 } 111 112 113 int DH_check(const DH *dh, int *ret) { 114 /* Check that p is a safe prime and if g is 2, 3 or 5, check that it is a 115 * suitable generator where: 116 * for 2, p mod 24 == 11 117 * for 3, p mod 12 == 5 118 * for 5, p mod 10 == 3 or 7 119 * should hold. 120 */ 121 int ok = 0, r; 122 BN_CTX *ctx = NULL; 123 BN_ULONG l; 124 BIGNUM *t1 = NULL, *t2 = NULL; 125 126 *ret = 0; 127 ctx = BN_CTX_new(); 128 if (ctx == NULL) { 129 goto err; 130 } 131 BN_CTX_start(ctx); 132 t1 = BN_CTX_get(ctx); 133 if (t1 == NULL) { 134 goto err; 135 } 136 t2 = BN_CTX_get(ctx); 137 if (t2 == NULL) { 138 goto err; 139 } 140 141 if (dh->q) { 142 if (BN_cmp(dh->g, BN_value_one()) <= 0) { 143 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 144 } else if (BN_cmp(dh->g, dh->p) >= 0) { 145 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 146 } else { 147 /* Check g^q == 1 mod p */ 148 if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) { 149 goto err; 150 } 151 if (!BN_is_one(t1)) { 152 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 153 } 154 } 155 r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL); 156 if (r < 0) { 157 goto err; 158 } 159 if (!r) { 160 *ret |= DH_CHECK_Q_NOT_PRIME; 161 } 162 /* Check p == 1 mod q i.e. q divides p - 1 */ 163 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) { 164 goto err; 165 } 166 if (!BN_is_one(t2)) { 167 *ret |= DH_CHECK_INVALID_Q_VALUE; 168 } 169 if (dh->j && BN_cmp(dh->j, t1)) { 170 *ret |= DH_CHECK_INVALID_J_VALUE; 171 } 172 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) { 173 l = BN_mod_word(dh->p, 24); 174 if (l == (BN_ULONG)-1) { 175 goto err; 176 } 177 if (l != 11) { 178 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 179 } 180 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) { 181 l = BN_mod_word(dh->p, 10); 182 if (l == (BN_ULONG)-1) { 183 goto err; 184 } 185 if (l != 3 && l != 7) { 186 *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; 187 } 188 } else { 189 *ret |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR; 190 } 191 192 r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL); 193 if (r < 0) { 194 goto err; 195 } 196 if (!r) { 197 *ret |= DH_CHECK_P_NOT_PRIME; 198 } else if (!dh->q) { 199 if (!BN_rshift1(t1, dh->p)) { 200 goto err; 201 } 202 r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL); 203 if (r < 0) { 204 goto err; 205 } 206 if (!r) { 207 *ret |= DH_CHECK_P_NOT_SAFE_PRIME; 208 } 209 } 210 ok = 1; 211 212 err: 213 if (ctx != NULL) { 214 BN_CTX_end(ctx); 215 BN_CTX_free(ctx); 216 } 217 return ok; 218 } 219
