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 *out_flags) { 63 *out_flags = 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 *out_flags |= 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 *out_flags |= 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 *out_flags |= 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 *out_flags) { 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 int ok = 0, r; 121 BN_CTX *ctx = NULL; 122 BN_ULONG l; 123 BIGNUM *t1 = NULL, *t2 = NULL; 124 125 *out_flags = 0; 126 ctx = BN_CTX_new(); 127 if (ctx == NULL) { 128 goto err; 129 } 130 BN_CTX_start(ctx); 131 t1 = BN_CTX_get(ctx); 132 if (t1 == NULL) { 133 goto err; 134 } 135 t2 = BN_CTX_get(ctx); 136 if (t2 == NULL) { 137 goto err; 138 } 139 140 if (dh->q) { 141 if (BN_cmp(dh->g, BN_value_one()) <= 0) { 142 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR; 143 } else if (BN_cmp(dh->g, dh->p) >= 0) { 144 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR; 145 } else { 146 // Check g^q == 1 mod p 147 if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) { 148 goto err; 149 } 150 if (!BN_is_one(t1)) { 151 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR; 152 } 153 } 154 r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL); 155 if (r < 0) { 156 goto err; 157 } 158 if (!r) { 159 *out_flags |= DH_CHECK_Q_NOT_PRIME; 160 } 161 // Check p == 1 mod q i.e. q divides p - 1 162 if (!BN_div(t1, t2, dh->p, dh->q, ctx)) { 163 goto err; 164 } 165 if (!BN_is_one(t2)) { 166 *out_flags |= DH_CHECK_INVALID_Q_VALUE; 167 } 168 if (dh->j && BN_cmp(dh->j, t1)) { 169 *out_flags |= DH_CHECK_INVALID_J_VALUE; 170 } 171 } else if (BN_is_word(dh->g, DH_GENERATOR_2)) { 172 l = BN_mod_word(dh->p, 24); 173 if (l == (BN_ULONG)-1) { 174 goto err; 175 } 176 if (l != 11) { 177 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR; 178 } 179 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) { 180 l = BN_mod_word(dh->p, 10); 181 if (l == (BN_ULONG)-1) { 182 goto err; 183 } 184 if (l != 3 && l != 7) { 185 *out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR; 186 } 187 } else { 188 *out_flags |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR; 189 } 190 191 r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL); 192 if (r < 0) { 193 goto err; 194 } 195 if (!r) { 196 *out_flags |= DH_CHECK_P_NOT_PRIME; 197 } else if (!dh->q) { 198 if (!BN_rshift1(t1, dh->p)) { 199 goto err; 200 } 201 r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL); 202 if (r < 0) { 203 goto err; 204 } 205 if (!r) { 206 *out_flags |= DH_CHECK_P_NOT_SAFE_PRIME; 207 } 208 } 209 ok = 1; 210 211 err: 212 if (ctx != NULL) { 213 BN_CTX_end(ctx); 214 BN_CTX_free(ctx); 215 } 216 return ok; 217 } 218
