220 lines
6.7 KiB
C
220 lines
6.7 KiB
C
/* crypto/dsa/dsa_sign.c */
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/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.]
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*/
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/* Origional version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
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#include <stdio.h>
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#include "cryptlib.h"
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#include "bn.h"
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#include "dsa.h"
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#include "rand.h"
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#include "asn1.h"
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/* data has already been hashed (probably with SHA or SHA-1). */
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/* DSAerr(DSA_F_DSA_SIGN,DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE); */
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int DSA_sign(type,dgst,dlen,sig,siglen,dsa)
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int type;
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unsigned char *dgst;
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int dlen;
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unsigned char *sig; /* out */
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unsigned int *siglen; /* out */
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DSA *dsa;
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{
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BIGNUM *kinv=NULL,*r=NULL;
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BIGNUM m;
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BIGNUM xr,s;
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BN_CTX *ctx=NULL;
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unsigned char *p;
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int i,len=0,ret=0,reason=ERR_R_BN_LIB;
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ASN1_INTEGER rbs,sbs;
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MS_STATIC unsigned char rbuf[50]; /* assuming r is 20 bytes +extra */
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MS_STATIC unsigned char sbuf[50]; /* assuming s is 20 bytes +extra */
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BN_init(&m);
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BN_init(&xr);
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BN_init(&s);
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i=BN_num_bytes(dsa->q); /* should be 20 */
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if ((dlen > i) || (dlen > 50))
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{
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reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE;
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goto err;
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}
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ctx=BN_CTX_new();
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if (ctx == NULL) goto err;
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if ((dsa->kinv == NULL) || (dsa->r == NULL))
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{
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if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err;
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}
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else
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{
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kinv=dsa->kinv;
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dsa->kinv=NULL;
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r=dsa->r;
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dsa->r=NULL;
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}
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if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err;
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/* Compute s = inv(k) (m + xr) mod q */
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if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
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if (!BN_add(&s, &xr, &m)) goto err; /* s = m + xr */
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if (BN_cmp(&s,dsa->q) > 0)
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BN_sub(&s,&s,dsa->q);
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if (!BN_mod_mul(&s,&s,kinv,dsa->q,ctx)) goto err;
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/*
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* Now create a ASN.1 sequence of the integers R and S.
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*/
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rbs.data=rbuf;
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sbs.data=sbuf;
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rbs.type = V_ASN1_INTEGER;
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sbs.type = V_ASN1_INTEGER;
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rbs.length=BN_bn2bin(r,rbs.data);
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sbs.length=BN_bn2bin(&s,sbs.data);
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len =i2d_ASN1_INTEGER(&rbs,NULL);
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len+=i2d_ASN1_INTEGER(&sbs,NULL);
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p=sig;
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ASN1_put_object(&p,1,len,V_ASN1_SEQUENCE,V_ASN1_UNIVERSAL);
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i2d_ASN1_INTEGER(&rbs,&p);
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i2d_ASN1_INTEGER(&sbs,&p);
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*siglen=(p-sig);
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ret=1;
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err:
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if (!ret) DSAerr(DSA_F_DSA_SIGN,reason);
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#if 1 /* do the right thing :-) */
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if (kinv != NULL) BN_clear_free(kinv);
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if (r != NULL) BN_clear_free(r);
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#endif
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if (ctx != NULL) BN_CTX_free(ctx);
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BN_clear_free(&m);
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BN_clear_free(&xr);
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BN_clear_free(&s);
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return(ret);
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}
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int DSA_sign_setup(dsa,ctx_in,kinvp,rp)
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DSA *dsa;
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BN_CTX *ctx_in;
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BIGNUM **kinvp;
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BIGNUM **rp;
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{
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BN_CTX *ctx;
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BIGNUM k,*kinv=NULL,*r=NULL;
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int ret=0;
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if (ctx_in == NULL)
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{
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if ((ctx=BN_CTX_new()) == NULL) goto err;
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}
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else
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ctx=ctx_in;
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BN_init(&k);
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if ((r=BN_new()) == NULL) goto err;
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kinv=NULL;
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/* Get random k */
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for (;;)
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{
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if (!BN_rand(&k, BN_num_bits(dsa->q), 1, 0)) goto err;
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if (BN_cmp(&k,dsa->q) >= 0)
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BN_sub(&k,&k,dsa->q);
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if (!BN_is_zero(&k)) break;
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}
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if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P))
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{
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if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL)
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if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p,
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dsa->p,ctx)) goto err;
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}
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/* Compute r = (g^k mod p) mod q */
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if (!BN_mod_exp_mont(r,dsa->g,&k,dsa->p,ctx,
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(BN_MONT_CTX *)dsa->method_mont_p)) goto err;
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if (!BN_mod(r,r,dsa->q,ctx)) goto err;
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/* Compute part of 's = inv(k) (m + xr) mod q' */
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if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
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if (*kinvp != NULL) BN_clear_free(*kinvp);
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*kinvp=kinv;
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kinv=NULL;
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if (*rp != NULL) BN_clear_free(*rp);
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*rp=r;
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ret=1;
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err:
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if (!ret)
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{
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DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
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if (kinv != NULL) BN_clear_free(kinv);
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if (r != NULL) BN_clear_free(r);
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}
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if (ctx_in == NULL) BN_CTX_free(ctx);
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if (kinv != NULL) BN_clear_free(kinv);
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BN_clear_free(&k);
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return(ret);
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}
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