1 /* $OpenBSD: dh_check.c,v 1.15 2015/02/07 13:19:15 doug Exp $ */ 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 #include <stdio.h> 60 61 #include <openssl/bn.h> 62 #include <openssl/dh.h> 63 64 /* 65 * Check that p is a safe prime and 66 * if g is 2, 3 or 5, check that it is a suitable generator 67 * where 68 * for 2, p mod 24 == 11 69 * for 3, p mod 12 == 5 70 * for 5, p mod 10 == 3 or 7 71 * should hold. 72 */ 73 74 int 75 DH_check(const DH *dh, int *ret) 76 { 77 int ok = 0; 78 BN_CTX *ctx = NULL; 79 BN_ULONG l; 80 BIGNUM *q = NULL; 81 82 *ret = 0; 83 ctx = BN_CTX_new(); 84 if (ctx == NULL) 85 goto err; 86 q = BN_new(); 87 if (q == NULL) 88 goto err; 89 90 if (BN_is_word(dh->g, DH_GENERATOR_2)) { 91 l = BN_mod_word(dh->p, 24); 92 if (l == (BN_ULONG)-1) 93 goto err; 94 if (l != 11) 95 *ret |= DH_NOT_SUITABLE_GENERATOR; 96 } else if (BN_is_word(dh->g, DH_GENERATOR_5)) { 97 l = BN_mod_word(dh->p, 10); 98 if (l == (BN_ULONG)-1) 99 goto err; 100 if (l != 3 && l != 7) 101 *ret |= DH_NOT_SUITABLE_GENERATOR; 102 } else 103 *ret |= DH_UNABLE_TO_CHECK_GENERATOR; 104 105 if (!BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL)) 106 *ret |= DH_CHECK_P_NOT_PRIME; 107 else { 108 if (!BN_rshift1(q, dh->p)) 109 goto err; 110 if (!BN_is_prime_ex(q, BN_prime_checks, ctx, NULL)) 111 *ret |= DH_CHECK_P_NOT_SAFE_PRIME; 112 } 113 ok = 1; 114 err: 115 BN_CTX_free(ctx); 116 BN_free(q); 117 return ok; 118 } 119 120 int 121 DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) 122 { 123 BIGNUM *q = NULL; 124 125 *ret = 0; 126 q = BN_new(); 127 if (q == NULL) 128 return 0; 129 BN_set_word(q, 1); 130 if (BN_cmp(pub_key, q) <= 0) 131 *ret |= DH_CHECK_PUBKEY_TOO_SMALL; 132 BN_copy(q, dh->p); 133 BN_sub_word(q, 1); 134 if (BN_cmp(pub_key, q) >= 0) 135 *ret |= DH_CHECK_PUBKEY_TOO_LARGE; 136 137 BN_free(q); 138 return 1; 139 } 140