crypto/dsa/dsa_sign.c

   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 /* Origional version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
  60
  61 #include <stdio.h>
  62 #include "cryptlib.h"
  63 #include "bn.h"
  64 #include "dsa.h"
  65 #include "rand.h"
  66 #include "asn1.h"
  67
  68 /* data has already been hashed (probably with SHA or SHA-1). */
  69 /*      DSAerr(DSA_F_DSA_SIGN,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); */
  70
  71 int DSA_sign(type,dgst,dlen,sig,siglen,dsa)
  72 int type;
  73 unsigned char *dgst;
  74 int dlen;
  75 unsigned char *sig;     /* out */
  76 unsigned int *siglen;   /* out */
  77 DSA *dsa;
  78         {
  79         BIGNUM *kinv=NULL,*r=NULL;
  80         BIGNUM *m=NULL;
  81         BIGNUM *xr=NULL,*s=NULL;
  82         BN_CTX *ctx=NULL;
  83         unsigned char *p;
  84         int i,len=0,ret=0,reason=ERR_R_BN_LIB;
  85         ASN1_INTEGER rbs,sbs;
  86         MS_STATIC unsigned char rbuf[50]; /* assuming r is 20 bytes +extra */
  87         MS_STATIC unsigned char sbuf[50]; /* assuming s is 20 bytes +extra */
  88
  89         i=BN_num_bytes(dsa->q); /* should be 20 */
  90         if ((dlen > i) || (dlen > 50))
  91                 {
  92                 reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
  93                 goto err;
  94                 }
  95
  96         ctx=BN_CTX_new();
  97         if (ctx == NULL) goto err;
  98
  99         if ((dsa->kinv == NULL) || (dsa->r == NULL))
 100                 {
 101                 if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
 102                 }
 103         else
 104                 {
 105                 kinv=dsa->kinv;
 106                 dsa->kinv=NULL;
 107                 r=dsa->r;
 108                 dsa->r=NULL;
 109                 }
 110
 111         m=BN_new();
 112         xr=BN_new();
 113         s=BN_new();
 114         if (m == NULL || xr == NULL || s == NULL) goto err;
 115
 116         if (BN_bin2bn(dgst,dlen,m) == NULL) goto err;
 117
 118         /* Compute  s = inv(k) (m + xr) mod q */
 119         if (!BN_mul(xr, dsa->priv_key, r)) goto err;    /* s = xr */
 120         if (!BN_add(s, xr, m)) goto err;                /* s = m + xr */
 121         if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
 122
 123         /*
 124          * Now create a ASN.1 sequence of the integers R and S.
 125          */
 126         rbs.data=rbuf;
 127         sbs.data=sbuf;
 128         rbs.type = V_ASN1_INTEGER;
 129         sbs.type = V_ASN1_INTEGER;
 130         rbs.length=BN_bn2bin(r,rbs.data);
 131         sbs.length=BN_bn2bin(s,sbs.data);
 132
 133         len =i2d_ASN1_INTEGER(&rbs,NULL);
 134         len+=i2d_ASN1_INTEGER(&sbs,NULL);
 135
 136         p=sig;
 137         ASN1_put_object(&p,1,len,V_ASN1_SEQUENCE,V_ASN1_UNIVERSAL);
 138         i2d_ASN1_INTEGER(&rbs,&p);
 139         i2d_ASN1_INTEGER(&sbs,&p);
 140         *siglen=(p-sig);
 141         ret=1;
 142 err:
 143         if (!ret) DSAerr(DSA_F_DSA_SIGN,reason);
 144
 145 #if 1 /* do the right thing :-) */
 146         if (kinv != NULL) BN_clear_free(kinv);
 147         if (r != NULL) BN_clear_free(r);
 148 #endif
 149         if (ctx != NULL) BN_CTX_free(ctx);
 150         if (m != NULL) BN_clear_free(m);
 151         if (xr != NULL) BN_clear_free(xr);
 152         if (s != NULL) BN_clear_free(s);
 153         return(ret);
 154         }
 155
 156 int DSA_sign_setup(dsa,ctx_in,kinvp,rp)
 157 DSA *dsa;
 158 BN_CTX *ctx_in;
 159 BIGNUM **kinvp;
 160 BIGNUM **rp;
 161         {
 162         BN_CTX *ctx;
 163         BIGNUM *k=NULL,*kinv=NULL,*r=NULL;
 164         int ret=0;
 165
 166         if (ctx_in == NULL)
 167                 {
 168                 if ((ctx=BN_CTX_new()) == NULL) goto err;
 169                 }
 170         else
 171                 ctx=ctx_in;
 172
 173         r=BN_new();
 174         k=BN_new();
 175         if ((r == NULL) || (k == NULL))
 176                 goto err;
 177         kinv=NULL;
 178
 179         if (r == NULL) goto err;
 180
 181         /* Get random k */
 182         for (;;)
 183                 {
 184                 if (!BN_rand(k, BN_num_bits(dsa->q), 1, 0)) goto err;
 185                 if (BN_cmp(k,dsa->q) >= 0)
 186                         BN_sub(k,k,dsa->q);
 187                 if (!BN_is_zero(k)) break;
 188                 }
 189
 190         /* Compute r = (g^k mod p) mod q */
 191         if (!BN_mod_exp(r,dsa->g,k,dsa->p,ctx)) goto err;
 192         if (!BN_mod(r,r,dsa->q,ctx)) goto err;
 193
 194         /* Compute  part of 's = inv(k) (m + xr) mod q' */
 195         if ((kinv=BN_mod_inverse(k,dsa->q,ctx)) == NULL) goto err;
 196
 197         if (*kinvp != NULL) BN_clear_free(*kinvp);
 198         *kinvp=kinv;
 199         kinv=NULL;
 200         if (*rp != NULL) BN_clear_free(*rp);
 201         *rp=r;
 202         ret=1;
 203 err:
 204         if (!ret)
 205                 {
 206                 DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
 207                 if (kinv != NULL) BN_clear_free(kinv);
 208                 if (r != NULL) BN_clear_free(r);
 209                 }
 210         if (ctx_in == NULL) BN_CTX_free(ctx);
 211         if (k != NULL) BN_clear_free(k);
 212         if (kinv != NULL) BN_clear_free(kinv);
 213         return(ret);
 214         }
 215