/* crypto/dsa/dsa_sign.c */ /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */ /* Original version from Steven Schoch */ #include #include "cryptlib.h" #include "bn.h" #include "dsa.h" #include "rand.h" #include "asn1.h" DSA_SIG * DSA_do_sign(unsigned char *dgst, int dlen, DSA *dsa) { BIGNUM *kinv=NULL,*r=NULL,*s=NULL; BIGNUM m; BIGNUM xr; BN_CTX *ctx=NULL; int i,reason=ERR_R_BN_LIB; DSA_SIG *ret=NULL; BN_init(&m); BN_init(&xr); s=BN_new(); if (s == NULL) goto err; i=BN_num_bytes(dsa->q); /* should be 20 */ if ((dlen > i) || (dlen > 50)) { reason=DSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE; goto err; } ctx=BN_CTX_new(); if (ctx == NULL) goto err; if ((dsa->kinv == NULL) || (dsa->r == NULL)) { if (!DSA_sign_setup(dsa,ctx,&kinv,&r)) goto err; } else { kinv=dsa->kinv; dsa->kinv=NULL; r=dsa->r; dsa->r=NULL; } if (BN_bin2bn(dgst,dlen,&m) == NULL) goto err; /* Compute s = inv(k) (m + xr) mod q */ if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */ if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */ if (BN_cmp(s,dsa->q) > 0) BN_sub(s,s,dsa->q); if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err; ret=DSA_SIG_new(); if (ret == NULL) goto err; ret->r = r; ret->s = s; err: if (!ret) { DSAerr(DSA_F_DSA_DO_SIGN,reason); BN_free(r); BN_free(s); } if (ctx != NULL) BN_CTX_free(ctx); BN_clear_free(&m); BN_clear_free(&xr); return(ret); } /* data has already been hashed (probably with SHA or SHA-1). */ /* unsigned char *sig: out */ /* unsigned int *siglen: out */ int DSA_sign(int type, unsigned char *dgst, int dlen, unsigned char *sig, unsigned int *siglen, DSA *dsa) { DSA_SIG *s; s=DSA_do_sign(dgst,dlen,dsa); if (s == NULL) { *siglen=0; return(0); } *siglen=i2d_DSA_SIG(s,&sig); DSA_SIG_free(s); return(1); } int DSA_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp) { BN_CTX *ctx; BIGNUM k,*kinv=NULL,*r=NULL; int ret=0; if (ctx_in == NULL) { if ((ctx=BN_CTX_new()) == NULL) goto err; } else ctx=ctx_in; BN_init(&k); if ((r=BN_new()) == NULL) goto err; kinv=NULL; /* Get random k */ for (;;) { if (!BN_rand(&k, BN_num_bits(dsa->q), 1, 0)) goto err; if (BN_cmp(&k,dsa->q) >= 0) BN_sub(&k,&k,dsa->q); if (!BN_is_zero(&k)) break; } if ((dsa->method_mont_p == NULL) && (dsa->flags & DSA_FLAG_CACHE_MONT_P)) { if ((dsa->method_mont_p=(char *)BN_MONT_CTX_new()) != NULL) if (!BN_MONT_CTX_set((BN_MONT_CTX *)dsa->method_mont_p, dsa->p,ctx)) goto err; } /* Compute r = (g^k mod p) mod q */ if (!BN_mod_exp_mont(r,dsa->g,&k,dsa->p,ctx, (BN_MONT_CTX *)dsa->method_mont_p)) goto err; if (!BN_mod(r,r,dsa->q,ctx)) goto err; /* Compute part of 's = inv(k) (m + xr) mod q' */ if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err; if (*kinvp != NULL) BN_clear_free(*kinvp); *kinvp=kinv; kinv=NULL; if (*rp != NULL) BN_clear_free(*rp); *rp=r; ret=1; err: if (!ret) { DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB); if (kinv != NULL) BN_clear_free(kinv); if (r != NULL) BN_clear_free(r); } if (ctx_in == NULL) BN_CTX_free(ctx); if (kinv != NULL) BN_clear_free(kinv); BN_clear_free(&k); return(ret); }