dsa_sign.c revision 55714
1/* crypto/dsa/dsa_sign.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/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */ 60 61#include <stdio.h> 62#include "cryptlib.h" 63#include <openssl/bn.h> 64#include <openssl/dsa.h> 65#include <openssl/rand.h> 66#include <openssl/asn1.h> 67 68DSA_SIG * DSA_do_sign(const unsigned char *dgst, int dlen, DSA *dsa) 69 { 70 BIGNUM *kinv=NULL,*r=NULL,*s=NULL; 71 BIGNUM m; 72 BIGNUM xr; 73 BN_CTX *ctx=NULL; 74 int i,reason=ERR_R_BN_LIB; 75 DSA_SIG *ret=NULL; 76 77 BN_init(&m); 78 BN_init(&xr); 79 s=BN_new(); 80 if (s == NULL) goto err; 81 82 i=BN_num_bytes(dsa->q); /* should be 20 */ 83 if ((dlen > i) || (dlen > 50)) 84 { 85 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE; 86 goto err; 87 } 88 89 ctx=BN_CTX_new(); 90 if (ctx == NULL) goto err; 91 92 if ((dsa->kinv == NULL) || (dsa->r == NULL)) 93 { 94 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; 95 } 96 else 97 { 98 kinv=dsa->kinv; 99 dsa->kinv=NULL; 100 r=dsa->r; 101 dsa->r=NULL; 102 } 103 104 if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err; 105 106 /* Compute s = inv(k) (m + xr) mod q */ 107 if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ 108 if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ 109 if (BN_cmp(s,dsa->q) > 0) 110 BN_sub(s,s,dsa->q); 111 if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; 112 113 ret=DSA_SIG_new(); 114 if (ret == NULL) goto err; 115 ret->r = r; 116 ret->s = s; 117 118err: 119 if (!ret) 120 { 121 DSAerr(DSA_F_DSA_DO_SIGN,reason); 122 BN_free(r); 123 BN_free(s); 124 } 125 if (ctx != NULL) BN_CTX_free(ctx); 126 BN_clear_free(&m); 127 BN_clear_free(&xr); 128 if (kinv != NULL) /* dsa->kinv is NULL now if we used it */ 129 BN_clear_free(kinv); 130 return(ret); 131 } 132 133/* data has already been hashed (probably with SHA or SHA-1). */ 134 135/* unsigned char *sig: out */ 136/* unsigned int *siglen: out */ 137int DSA_sign(int type, const unsigned char *dgst, int dlen, unsigned char *sig, 138 unsigned int *siglen, DSA *dsa) 139 { 140 DSA_SIG *s; 141 s=DSA_do_sign(dgst,dlen,dsa); 142 if (s == NULL) 143 { 144 *siglen=0; 145 return(0); 146 } 147 *siglen=i2d_DSA_SIG(s,&sig); 148 DSA_SIG_free(s); 149 return(1); 150 } 151 152int DSA_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) 153 { 154 BN_CTX *ctx; 155 BIGNUM k,*kinv=NULL,*r=NULL; 156 int ret=0; 157 158 if (ctx_in == NULL) 159 { 160 if ((ctx=BN_CTX_new()) == NULL) goto err; 161 } 162 else 163 ctx=ctx_in; 164 165 BN_init(&k); 166 if ((r=BN_new()) == NULL) goto err; 167 kinv=NULL; 168 169 /* Get random k */ 170 for (;;) 171 { 172 if (!BN_rand(&k, BN_num_bits(dsa->q), 1, 0)) goto err; 173 if (BN_cmp(&k,dsa->q) >= 0) 174 BN_sub(&k,&k,dsa->q); 175 if (!BN_is_zero(&k)) break; 176 } 177 178 if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) 179 { 180 if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL) 181 if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p, 182 dsa->p,ctx)) goto err; 183 } 184 185 /* Compute r = (g^k mod p) mod q */ 186 if (!BN_mod_exp_mont(r,dsa->g,&k,dsa->p,ctx, 187 (BN_MONT_CTX *)dsa->method_mont_p)) goto err; 188 if (!BN_mod(r,r,dsa->q,ctx)) goto err; 189 190 /* Compute part of 's = inv(k) (m + xr) mod q' */ 191 if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; 192 193 if (*kinvp != NULL) BN_clear_free(*kinvp); 194 *kinvp=kinv; 195 kinv=NULL; 196 if (*rp != NULL) BN_clear_free(*rp); 197 *rp=r; 198 ret=1; 199err: 200 if (!ret) 201 { 202 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); 203 if (kinv != NULL) BN_clear_free(kinv); 204 if (r != NULL) BN_clear_free(r); 205 } 206 if (ctx_in == NULL) BN_CTX_free(ctx); 207 if (kinv != NULL) BN_clear_free(kinv); 208 BN_clear_free(&k); 209 return(ret); 210 } 211 212