/* crypto/dsa/dsa_ossl.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 <schoch@sheba.arc.nasa.gov> */

#include <stdio.h>
#include <openssl/bn.h>
#include <openssl/dsa.h>
#include <openssl/rand.h>
#include <openssl/asn1.h>
#include <openssl/err.h>
#ifndef OPENSSL_NO_ENGINE
# include <openssl/engine.h>
#endif
#include <openssl/fips.h>

#ifdef OPENSSL_FIPS

static DSA_SIG *dsa_do_sign(const unsigned char *dgst, FIPS_DSA_SIZE_T dlen,
                            DSA *dsa);
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
                          BIGNUM **rp);
static int dsa_do_verify(const unsigned char *dgst, FIPS_DSA_SIZE_T dgst_len,
                         DSA_SIG *sig, DSA *dsa);
static int dsa_init(DSA *dsa);
static int dsa_finish(DSA *dsa);
static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
                       BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
                       BN_MONT_CTX *in_mont);
static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
                          const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);

static const DSA_METHOD openssl_dsa_meth = {
    "OpenSSL FIPS DSA method",
    dsa_do_sign,
    dsa_sign_setup,
    dsa_do_verify,
    dsa_mod_exp,
    dsa_bn_mod_exp,
    dsa_init,
    dsa_finish,
    DSA_FLAG_FIPS_METHOD,
    NULL
};

# if 0
int FIPS_dsa_check(struct dsa_st *dsa)
{
    if (dsa->meth != &openssl_dsa_meth
        || dsa->meth->dsa_do_sign != dsa_do_sign
        || dsa->meth->dsa_sign_setup != dsa_sign_setup
        || dsa->meth->dsa_mod_exp != dsa_mod_exp
        || dsa->meth->bn_mod_exp != dsa_bn_mod_exp
        || dsa->meth->init != dsa_init || dsa->meth->finish != dsa_finish) {
        FIPSerr(FIPS_F_FIPS_DSA_CHECK, FIPS_R_NON_FIPS_METHOD);
        return 0;
    }
    return 1;
}
# endif

const DSA_METHOD *DSA_OpenSSL(void)
{
    return &openssl_dsa_meth;
}

static DSA_SIG *dsa_do_sign(const unsigned char *dgst, FIPS_DSA_SIZE_T 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;

    if (FIPS_selftest_failed()) {
        FIPSerr(FIPS_F_DSA_DO_SIGN, FIPS_R_FIPS_SELFTEST_FAILED);
        return NULL;
    }

    if (FIPS_mode()
        && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS)) {
        DSAerr(DSA_F_DSA_DO_SIGN, DSA_R_KEY_SIZE_TOO_SMALL);
        return NULL;
    }

    BN_init(&m);
    BN_init(&xr);

    if (!dsa->p || !dsa->q || !dsa->g) {
        reason = DSA_R_MISSING_PARAMETERS;
        goto err;
    }

    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->meth->dsa_sign_setup(dsa, ctx, &kinv, &r))
        goto err;

    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);
    if (kinv != NULL)           /* dsa->kinv is NULL now if we used it */
        BN_clear_free(kinv);
    return (ret);
}

static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
                          BIGNUM **rp)
{
    BN_CTX *ctx;
    BIGNUM k, kq, *K, *kinv = NULL, *r = NULL;
    int ret = 0;

    if (!dsa->p || !dsa->q || !dsa->g) {
        DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
        return 0;
    }

    BN_init(&k);
    BN_init(&kq);

    if (ctx_in == NULL) {
        if ((ctx = BN_CTX_new()) == NULL)
            goto err;
    } else
        ctx = ctx_in;

    if ((r = BN_new()) == NULL)
        goto err;

    /* Get random k */
    do
        if (!BN_rand_range(&k, dsa->q))
            goto err;
    while (BN_is_zero(&k)) ;
    if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
        BN_set_flags(&k, BN_FLG_CONSTTIME);
    }

    if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
        if (!BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
                                    CRYPTO_LOCK_DSA, dsa->p, ctx))
            goto err;
    }

    /* Compute r = (g^k mod p) mod q */

    if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0) {
        if (!BN_copy(&kq, &k))
            goto err;

        /*
         * We do not want timing information to leak the length of k, so we
         * compute g^k using an equivalent exponent of fixed length. (This
         * is a kludge that we need because the BN_mod_exp_mont() does not
         * let us specify the desired timing behaviour.)
         */

        if (!BN_add(&kq, &kq, dsa->q))
            goto err;
        if (BN_num_bits(&kq) <= BN_num_bits(dsa->q)) {
            if (!BN_add(&kq, &kq, dsa->q))
                goto err;
        }

        K = &kq;
    } else {
        K = &k;
    }
    if (!dsa->meth->bn_mod_exp(dsa, 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);
    BN_clear_free(&kq);
    return (ret);
}

static int dsa_do_verify(const unsigned char *dgst, FIPS_DSA_SIZE_T dgst_len,
                         DSA_SIG *sig, DSA *dsa)
{
    BN_CTX *ctx;
    BIGNUM u1, u2, t1;
    BN_MONT_CTX *mont = NULL;
    int ret = -1;

    if (!dsa->p || !dsa->q || !dsa->g) {
        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
        return -1;
    }

    if (FIPS_selftest_failed()) {
        FIPSerr(FIPS_F_DSA_DO_VERIFY, FIPS_R_FIPS_SELFTEST_FAILED);
        return -1;
    }

    if (BN_num_bits(dsa->q) != 160) {
        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_BAD_Q_VALUE);
        return -1;
    }

    if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS) {
        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MODULUS_TOO_LARGE);
        return -1;
    }

    if (FIPS_mode()
        && (BN_num_bits(dsa->p) < OPENSSL_DSA_FIPS_MIN_MODULUS_BITS)) {
        DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_KEY_SIZE_TOO_SMALL);
        return -1;
    }

    BN_init(&u1);
    BN_init(&u2);
    BN_init(&t1);

    if ((ctx = BN_CTX_new()) == NULL)
        goto err;

    if (BN_is_zero(sig->r) || sig->r->neg || BN_ucmp(sig->r, dsa->q) >= 0) {
        ret = 0;
        goto err;
    }
    if (BN_is_zero(sig->s) || sig->s->neg || BN_ucmp(sig->s, dsa->q) >= 0) {
        ret = 0;
        goto err;
    }

    /*
     * Calculate W = inv(S) mod Q save W in u2
     */
    if ((BN_mod_inverse(&u2, sig->s, dsa->q, ctx)) == NULL)
        goto err;

    /* save M in u1 */
    if (BN_bin2bn(dgst, dgst_len, &u1) == NULL)
        goto err;

    /* u1 = M * w mod q */
    if (!BN_mod_mul(&u1, &u1, &u2, dsa->q, ctx))
        goto err;

    /* u2 = r * w mod q */
    if (!BN_mod_mul(&u2, sig->r, &u2, dsa->q, ctx))
        goto err;

    if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
        mont = BN_MONT_CTX_set_locked((BN_MONT_CTX **)&dsa->method_mont_p,
                                      CRYPTO_LOCK_DSA, dsa->p, ctx);
        if (!mont)
            goto err;
    }
# if 0
    {
        BIGNUM t2;

        BN_init(&t2);
        /* v = ( g^u1 * y^u2 mod p ) mod q */
        /* let t1 = g ^ u1 mod p */
        if (!BN_mod_exp_mont(&t1, dsa->g, &u1, dsa->p, ctx, mont))
            goto err;
        /* let t2 = y ^ u2 mod p */
        if (!BN_mod_exp_mont(&t2, dsa->pub_key, &u2, dsa->p, ctx, mont))
            goto err;
        /* let u1 = t1 * t2 mod p */
        if (!BN_mod_mul(&u1, &t1, &t2, dsa->p, ctx))
            goto err_bn;
        BN_free(&t2);
    }
    /* let u1 = u1 mod q */
    if (!BN_mod(&u1, &u1, dsa->q, ctx))
        goto err;
# else
    {
        if (!dsa->meth->dsa_mod_exp(dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2,
                                    dsa->p, ctx, mont))
            goto err;
        /* BN_copy(&u1,&t1); */
        /* let u1 = u1 mod q */
        if (!BN_mod(&u1, &t1, dsa->q, ctx))
            goto err;
    }
# endif
    /*
     * V is now in u1.  If the signature is correct, it will be equal to R.
     */
    ret = (BN_ucmp(&u1, sig->r) == 0);

 err:
    if (ret != 1)
        DSAerr(DSA_F_DSA_DO_VERIFY, ERR_R_BN_LIB);
    if (ctx != NULL)
        BN_CTX_free(ctx);
    BN_free(&u1);
    BN_free(&u2);
    BN_free(&t1);
    return (ret);
}

static int dsa_init(DSA *dsa)
{
    FIPS_selftest_check();
    dsa->flags |= DSA_FLAG_CACHE_MONT_P;
    return (1);
}

static int dsa_finish(DSA *dsa)
{
    if (dsa->method_mont_p)
        BN_MONT_CTX_free((BN_MONT_CTX *)dsa->method_mont_p);
    return (1);
}

static int dsa_mod_exp(DSA *dsa, BIGNUM *rr, BIGNUM *a1, BIGNUM *p1,
                       BIGNUM *a2, BIGNUM *p2, BIGNUM *m, BN_CTX *ctx,
                       BN_MONT_CTX *in_mont)
{
    return BN_mod_exp2_mont(rr, a1, p1, a2, p2, m, ctx, in_mont);
}

static int dsa_bn_mod_exp(DSA *dsa, BIGNUM *r, BIGNUM *a, const BIGNUM *p,
                          const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx)
{
    return BN_mod_exp_mont(r, a, p, m, ctx, m_ctx);
}

#else                           /* ndef OPENSSL_FIPS */

static void *dummy = &dummy;

#endif                          /* ndef OPENSSL_FIPS */
