ecs_ossl.c

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/* crypto/ecdsa/ecs_ossl.c */
/*
 * Written by Nils Larsch for the OpenSSL project
 */
/* ====================================================================
 * Copyright (c) 1998-2004 The OpenSSL Project.  All rights reserved.
 *
 * 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 above 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 acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit. (http://www.OpenSSL.org/)"
 *
 * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For written permission, please contact
 *    [email protected].
 *
 * 5. Products derived from this software may not be called "OpenSSL"
 *    nor may "OpenSSL" appear in their names without prior written
 *    permission of the OpenSSL Project.
 *
 * 6. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by the OpenSSL Project
 *    for use in the OpenSSL Toolkit (http://www.OpenSSL.org/)"
 *
 * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
 * EXPRESSED 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 OpenSSL PROJECT OR
 * ITS 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.
 * ====================================================================
 *
 * This product includes cryptographic software written by Eric Young
 * ([email protected]).  This product includes software written by Tim
 * Hudson ([email protected]).
 *
 */

#include "ecs_locl.h"
#include <openssl/err.h>
#include <openssl/obj_mac.h>
#include <openssl/bn.h>

static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dlen, 
        const BIGNUM *, const BIGNUM *, EC_KEY *eckey);
static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, 
        BIGNUM **rp);
static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len, 
        const ECDSA_SIG *sig, EC_KEY *eckey);

static ECDSA_METHOD openssl_ecdsa_meth = {
    "OpenSSL ECDSA method",
    ecdsa_do_sign,
    ecdsa_sign_setup,
    ecdsa_do_verify,
#if 0
    NULL, /* init     */
    NULL, /* finish   */
#endif
    0,    /* flags    */
    NULL  /* app_data */
};

const ECDSA_METHOD *ECDSA_OpenSSL(void)
{
    return &openssl_ecdsa_meth;
}

static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
        BIGNUM **rp)
{
    BN_CTX   *ctx = NULL;
    BIGNUM   *k = NULL, *r = NULL, *order = NULL, *X = NULL;
    EC_POINT *tmp_point=NULL;
    const EC_GROUP *group;
    int      ret = 0;

    if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL)
    {
        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
        return 0;
    }

    if (ctx_in == NULL) 
    {
        if ((ctx = BN_CTX_new()) == NULL)
        {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,ERR_R_MALLOC_FAILURE);
            return 0;
        }
    }
    else
        ctx = ctx_in;

    k     = BN_new();   /* this value is later returned in *kinvp */
    r     = BN_new();   /* this value is later returned in *rp    */
    order = BN_new();
    X     = BN_new();
    if (!k || !r || !order || !X)
    {
        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
        goto err;
    }
    if ((tmp_point = EC_POINT_new(group)) == NULL)
    {
        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
        goto err;
    }
    if (!EC_GROUP_get_order(group, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
        goto err;
    }
    
    do
    {
        /* get random k */  
        do
            if (!BN_rand_range(k, order))
            {
                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,
                 ECDSA_R_RANDOM_NUMBER_GENERATION_FAILED);  
                goto err;
            }
        while (BN_is_zero(k));

        /* We do not want timing information to leak the length of k,
         * so we compute G*k using an equivalent scalar of fixed
         * bit-length. */

        if (!BN_add(k, k, order)) goto err;
        if (BN_num_bits(k) <= BN_num_bits(order))
            if (!BN_add(k, k, order)) goto err;

        /* compute r the x-coordinate of generator * k */
        if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx))
        {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
            goto err;
        }
        if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == NID_X9_62_prime_field)
        {
            if (!EC_POINT_get_affine_coordinates_GFp(group,
                tmp_point, X, NULL, ctx))
            {
                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,ERR_R_EC_LIB);
                goto err;
            }
        }
#ifndef OPENSSL_NO_EC2M
        else /* NID_X9_62_characteristic_two_field */
        {
            if (!EC_POINT_get_affine_coordinates_GF2m(group,
                tmp_point, X, NULL, ctx))
            {
                ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP,ERR_R_EC_LIB);
                goto err;
            }
        }
#endif
        if (!BN_nnmod(r, X, order, ctx))
        {
            ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
            goto err;
        }
    }
    while (BN_is_zero(r));

    /* compute the inverse of k */
    if (!BN_mod_inverse(k, k, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
        goto err;   
    }
    /* clear old values if necessary */
    if (*rp != NULL)
        BN_clear_free(*rp);
    if (*kinvp != NULL) 
        BN_clear_free(*kinvp);
    /* save the pre-computed values  */
    *rp    = r;
    *kinvp = k;
    ret = 1;
err:
    if (!ret)
    {
        if (k != NULL) BN_clear_free(k);
        if (r != NULL) BN_clear_free(r);
    }
    if (ctx_in == NULL) 
        BN_CTX_free(ctx);
    if (order != NULL)
        BN_free(order);
    if (tmp_point != NULL) 
        EC_POINT_free(tmp_point);
    if (X)
        BN_clear_free(X);
    return(ret);
}


static ECDSA_SIG *ecdsa_do_sign(const unsigned char *dgst, int dgst_len, 
        const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)
{
    int     ok = 0, i;
    BIGNUM *kinv=NULL, *s, *m=NULL,*tmp=NULL,*order=NULL;
    const BIGNUM *ckinv;
    BN_CTX     *ctx = NULL;
    const EC_GROUP   *group;
    ECDSA_SIG  *ret;
    ECDSA_DATA *ecdsa;
    const BIGNUM *priv_key;

    ecdsa    = ecdsa_check(eckey);
    group    = EC_KEY_get0_group(eckey);
    priv_key = EC_KEY_get0_private_key(eckey);
    
    if (group == NULL || priv_key == NULL || ecdsa == NULL)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_PASSED_NULL_PARAMETER);
        return NULL;
    }

    ret = ECDSA_SIG_new();
    if (!ret)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
        return NULL;
    }
    s = ret->s;

    if ((ctx = BN_CTX_new()) == NULL || (order = BN_new()) == NULL ||
        (tmp = BN_new()) == NULL || (m = BN_new()) == NULL)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
        goto err;
    }

    if (!EC_GROUP_get_order(group, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_EC_LIB);
        goto err;
    }
    i = BN_num_bits(order);
    /* Need to truncate digest if it is too long: first truncate whole
     * bytes.
     */
    if (8 * dgst_len > i)
        dgst_len = (i + 7)/8;
    if (!BN_bin2bn(dgst, dgst_len, m))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
        goto err;
    }
    /* If still too long truncate remaining bits with a shift */
    if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
        goto err;
    }
    do
    {
        if (in_kinv == NULL || in_r == NULL)
        {
            if (!ECDSA_sign_setup(eckey, ctx, &kinv, &ret->r))
            {
                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN,ERR_R_ECDSA_LIB);
                goto err;
            }
            ckinv = kinv;
        }
        else
        {
            ckinv  = in_kinv;
            if (BN_copy(ret->r, in_r) == NULL)
            {
                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_MALLOC_FAILURE);
                goto err;
            }
        }

        if (!BN_mod_mul(tmp, priv_key, ret->r, order, ctx))
        {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
            goto err;
        }
        if (!BN_mod_add_quick(s, tmp, m, order))
        {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
            goto err;
        }
        if (!BN_mod_mul(s, s, ckinv, order, ctx))
        {
            ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ERR_R_BN_LIB);
            goto err;
        }
        if (BN_is_zero(s))
        {
            /* if kinv and r have been supplied by the caller
             * don't to generate new kinv and r values */
            if (in_kinv != NULL && in_r != NULL)
            {
                ECDSAerr(ECDSA_F_ECDSA_DO_SIGN, ECDSA_R_NEED_NEW_SETUP_VALUES);
                goto err;
            }
        }
        else
            /* s != 0 => we have a valid signature */
            break;
    }
    while (1);

    ok = 1;
err:
    if (!ok)
    {
        ECDSA_SIG_free(ret);
        ret = NULL;
    }
    if (ctx)
        BN_CTX_free(ctx);
    if (m)
        BN_clear_free(m);
    if (tmp)
        BN_clear_free(tmp);
    if (order)
        BN_free(order);
    if (kinv)
        BN_clear_free(kinv);
    return ret;
}

static int ecdsa_do_verify(const unsigned char *dgst, int dgst_len,
        const ECDSA_SIG *sig, EC_KEY *eckey)
{
    int ret = -1, i;
    BN_CTX   *ctx;
    BIGNUM   *order, *u1, *u2, *m, *X;
    EC_POINT *point = NULL;
    const EC_GROUP *group;
    const EC_POINT *pub_key;

    /* check input values */
    if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
        (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_MISSING_PARAMETERS);
        return -1;
    }

    ctx = BN_CTX_new();
    if (!ctx)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
        return -1;
    }
    BN_CTX_start(ctx);
    order = BN_CTX_get(ctx);    
    u1    = BN_CTX_get(ctx);
    u2    = BN_CTX_get(ctx);
    m     = BN_CTX_get(ctx);
    X     = BN_CTX_get(ctx);
    if (!X)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }
    
    if (!EC_GROUP_get_order(group, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
        goto err;
    }

    if (BN_is_zero(sig->r)          || BN_is_negative(sig->r) || 
        BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s)  ||
        BN_is_negative(sig->s)      || BN_ucmp(sig->s, order) >= 0)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ECDSA_R_BAD_SIGNATURE);
        ret = 0;    /* signature is invalid */
        goto err;
    }
    /* calculate tmp1 = inv(S) mod order */
    if (!BN_mod_inverse(u2, sig->s, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }
    /* digest -> m */
    i = BN_num_bits(order);
    /* Need to truncate digest if it is too long: first truncate whole
     * bytes.
     */
    if (8 * dgst_len > i)
        dgst_len = (i + 7)/8;
    if (!BN_bin2bn(dgst, dgst_len, m))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }
    /* If still too long truncate remaining bits with a shift */
    if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7)))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }
    /* u1 = m * tmp mod order */
    if (!BN_mod_mul(u1, m, u2, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }
    /* u2 = r * w mod q */
    if (!BN_mod_mul(u2, sig->r, u2, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }

    if ((point = EC_POINT_new(group)) == NULL)
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_MALLOC_FAILURE);
        goto err;
    }
    if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
        goto err;
    }
    if (EC_METHOD_get_field_type(EC_GROUP_method_of(group)) == NID_X9_62_prime_field)
    {
        if (!EC_POINT_get_affine_coordinates_GFp(group,
            point, X, NULL, ctx))
        {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
            goto err;
        }
    }
#ifndef OPENSSL_NO_EC2M
    else /* NID_X9_62_characteristic_two_field */
    {
        if (!EC_POINT_get_affine_coordinates_GF2m(group,
            point, X, NULL, ctx))
        {
            ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_EC_LIB);
            goto err;
        }
    }
#endif  
    if (!BN_nnmod(u1, X, order, ctx))
    {
        ECDSAerr(ECDSA_F_ECDSA_DO_VERIFY, ERR_R_BN_LIB);
        goto err;
    }
    /*  if the signature is correct u1 is equal to sig->r */
    ret = (BN_ucmp(u1, sig->r) == 0);
err:
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    if (point)
        EC_POINT_free(point);
    return ret;
}