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398 lines
11 KiB
398 lines
11 KiB
/* crypto/dsa/dsa_ossl.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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/* Original 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 <openssl/bn.h>
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#include <openssl/sha.h>
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#include <openssl/dsa.h>
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#include <openssl/rand.h>
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#include <openssl/asn1.h>
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static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
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static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp);
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static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
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DSA *dsa);
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static int dsa_init(DSA *dsa);
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static int dsa_finish(DSA *dsa);
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static DSA_METHOD openssl_dsa_meth = {
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"OpenSSL DSA method",
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dsa_do_sign,
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dsa_sign_setup,
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dsa_do_verify,
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NULL, /* dsa_mod_exp, */
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NULL, /* dsa_bn_mod_exp, */
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dsa_init,
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dsa_finish,
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0,
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NULL,
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NULL,
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NULL
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};
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/* These macro wrappers replace attempts to use the dsa_mod_exp() and
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* bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
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* having a the macro work as an expression by bundling an "err_instr". So;
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*
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* if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
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* dsa->method_mont_p)) goto err;
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*
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* can be replaced by;
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*
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* DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
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* dsa->method_mont_p);
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*/
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#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
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do { \
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int _tmp_res53; \
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if((dsa)->meth->dsa_mod_exp) \
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_tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
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(a2), (p2), (m), (ctx), (in_mont)); \
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else \
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_tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
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(m), (ctx), (in_mont)); \
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if(!_tmp_res53) err_instr; \
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} while(0)
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#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
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do { \
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int _tmp_res53; \
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if((dsa)->meth->bn_mod_exp) \
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_tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
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(m), (ctx), (m_ctx)); \
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else \
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_tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
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if(!_tmp_res53) err_instr; \
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} while(0)
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const DSA_METHOD *DSA_OpenSSL(void)
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{
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return &openssl_dsa_meth;
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}
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static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
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{
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BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
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BIGNUM m;
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BIGNUM xr;
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BN_CTX *ctx=NULL;
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int reason=ERR_R_BN_LIB;
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DSA_SIG *ret=NULL;
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BN_init(&m);
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BN_init(&xr);
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if (!dsa->p || !dsa->q || !dsa->g)
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{
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reason=DSA_R_MISSING_PARAMETERS;
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goto err;
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}
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s=BN_new();
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if (s == NULL) goto err;
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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 (dlen > BN_num_bytes(dsa->q))
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/* if the digest length is greater than the size of q use the
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* BN_num_bits(dsa->q) leftmost bits of the digest, see
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* fips 186-3, 4.2 */
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dlen = BN_num_bytes(dsa->q);
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if (BN_bin2bn(dgst,dlen,&m) == NULL)
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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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if (!BN_sub(s,s,dsa->q)) goto err;
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if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
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ret=DSA_SIG_new();
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if (ret == NULL) goto err;
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ret->r = r;
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ret->s = s;
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err:
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if (!ret)
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{
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DSAerr(DSA_F_DSA_DO_SIGN,reason);
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BN_free(r);
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BN_free(s);
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}
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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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if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
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BN_clear_free(kinv);
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return(ret);
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}
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static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)
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{
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BN_CTX *ctx;
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BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
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int ret=0;
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if (!dsa->p || !dsa->q || !dsa->g)
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{
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DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
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return 0;
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}
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BN_init(&k);
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BN_init(&kq);
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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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if ((r=BN_new()) == NULL) goto err;
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/* Get random k */
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do
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if (!BN_rand_range(&k, dsa->q)) goto err;
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while (BN_is_zero(&k));
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if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
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{
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BN_set_flags(&k, BN_FLG_CONSTTIME);
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}
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if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
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{
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if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
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CRYPTO_LOCK_DSA,
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dsa->p, ctx))
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goto err;
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}
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/* Compute r = (g^k mod p) mod q */
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if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
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{
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if (!BN_copy(&kq, &k)) goto err;
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/* We do not want timing information to leak the length of k,
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* so we compute g^k using an equivalent exponent of fixed length.
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*
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* (This is a kludge that we need because the BN_mod_exp_mont()
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* does not let us specify the desired timing behaviour.) */
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if (!BN_add(&kq, &kq, dsa->q)) goto err;
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if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
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{
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if (!BN_add(&kq, &kq, dsa->q)) goto err;
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}
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K = &kq;
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}
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else
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{
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K = &k;
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}
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DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
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dsa->method_mont_p);
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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 (r != NULL)
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BN_clear_free(r);
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}
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if (ctx_in == NULL) BN_CTX_free(ctx);
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BN_clear_free(&k);
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BN_clear_free(&kq);
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return(ret);
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}
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static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
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DSA *dsa)
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{
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BN_CTX *ctx;
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BIGNUM u1,u2,t1;
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BN_MONT_CTX *mont=NULL;
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int ret = -1, i;
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if (!dsa->p || !dsa->q || !dsa->g)
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{
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DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
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return -1;
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}
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i = BN_num_bits(dsa->q);
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/* fips 186-3 allows only different sizes for q */
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if (i != 160 && i != 224 && i != 256)
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{
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DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
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return -1;
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}
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if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
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{
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DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
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return -1;
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}
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BN_init(&u1);
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BN_init(&u2);
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BN_init(&t1);
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if ((ctx=BN_CTX_new()) == NULL) goto err;
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if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
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BN_ucmp(sig->r, dsa->q) >= 0)
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{
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ret = 0;
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goto err;
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}
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if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
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BN_ucmp(sig->s, dsa->q) >= 0)
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{
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ret = 0;
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goto err;
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}
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/* Calculate W = inv(S) mod Q
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* save W in u2 */
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if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
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/* save M in u1 */
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if (dgst_len > (i >> 3))
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/* if the digest length is greater than the size of q use the
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* BN_num_bits(dsa->q) leftmost bits of the digest, see
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* fips 186-3, 4.2 */
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dgst_len = (i >> 3);
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if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
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/* u1 = M * w mod q */
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if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
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/* u2 = r * w mod q */
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if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
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if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
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{
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mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
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CRYPTO_LOCK_DSA, dsa->p, ctx);
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if (!mont)
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goto err;
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}
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DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
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/* BN_copy(&u1,&t1); */
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/* let u1 = u1 mod q */
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if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
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/* V is now in u1. If the signature is correct, it will be
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* equal to R. */
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ret=(BN_ucmp(&u1, sig->r) == 0);
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err:
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/* XXX: surely this is wrong - if ret is 0, it just didn't verify;
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there is no error in BN. Test should be ret == -1 (Ben) */
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if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
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if (ctx != NULL) BN_CTX_free(ctx);
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BN_free(&u1);
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BN_free(&u2);
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BN_free(&t1);
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return(ret);
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}
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static int dsa_init(DSA *dsa)
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{
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dsa->flags|=DSA_FLAG_CACHE_MONT_P;
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return(1);
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}
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static int dsa_finish(DSA *dsa)
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{
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if(dsa->method_mont_p)
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BN_MONT_CTX_free(dsa->method_mont_p);
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return(1);
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}
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