1 /* crypto/dh/dh_check.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 #include <stdio.h> 60 #include "cryptlib.h" 61 #include <openssl/bn.h> 62 #include <openssl/dh.h> 63 64 /* Check that p is a safe prime and 65 * if g is 2, 3 or 5, check that it is a suitable generator 66 * where 67 * for 2, p mod 24 == 11 68 * for 3, p mod 12 == 5 69 * for 5, p mod 10 == 3 or 7 70 * should hold. 71 */ 72 73 int DH_check(const DH *dh, int *ret) 74 { 75 int ok=0; 76 BN_CTX *ctx=NULL; 77 BN_ULONG l; 78 BIGNUM *q=NULL; 79 80 *ret=0; 81 ctx=BN_CTX_new(); 82 if (ctx == NULL) goto err; 83 q=BN_new(); 84 if (q == NULL) goto err; 85 86 if (BN_is_word(dh->g,DH_GENERATOR_2)) 87 { 88 l=BN_mod_word(dh->p,24); 89 if (l != 11) *ret|=DH_NOT_SUITABLE_GENERATOR; 90 } 91 #if 0 92 else if (BN_is_word(dh->g,DH_GENERATOR_3)) 93 { 94 l=BN_mod_word(dh->p,12); 95 if (l != 5) *ret|=DH_NOT_SUITABLE_GENERATOR; 96 } 97 #endif 98 else if (BN_is_word(dh->g,DH_GENERATOR_5)) 99 { 100 l=BN_mod_word(dh->p,10); 101 if ((l != 3) && (l != 7)) 102 *ret|=DH_NOT_SUITABLE_GENERATOR; 103 } 104 else 105 *ret|=DH_UNABLE_TO_CHECK_GENERATOR; 106 107 if (!BN_is_prime_ex(dh->p,BN_prime_checks,ctx,NULL)) 108 *ret|=DH_CHECK_P_NOT_PRIME; 109 else 110 { 111 if (!BN_rshift1(q,dh->p)) goto err; 112 if (!BN_is_prime_ex(q,BN_prime_checks,ctx,NULL)) 113 *ret|=DH_CHECK_P_NOT_SAFE_PRIME; 114 } 115 ok=1; 116 err: 117 if (ctx != NULL) BN_CTX_free(ctx); 118 if (q != NULL) BN_free(q); 119 return(ok); 120 } 121 122 int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) 123 { 124 int ok=0; 125 BIGNUM *q=NULL; 126 127 *ret=0; 128 q=BN_new(); 129 if (q == NULL) goto err; 130 BN_set_word(q,1); 131 if (BN_cmp(pub_key,q)<=0) 132 *ret|=DH_CHECK_PUBKEY_TOO_SMALL; 133 BN_copy(q,dh->p); 134 BN_sub_word(q,1); 135 if (BN_cmp(pub_key,q)>=0) 136 *ret|=DH_CHECK_PUBKEY_TOO_LARGE; 137 138 ok = 1; 139 err: 140 if (q != NULL) BN_free(q); 141 return(ok); 142 } 143