/**********************************************************************
 *                          gost2001.c                                *
 *             Copyright (c) 2005-2006 Cryptocom LTD                  *
 *         This file is distributed under the same license as OpenSSL *
 *                                                                    *
 *          Implementation of GOST R 34.10-2001                                   *
 *          Requires OpenSSL 0.9.9 for compilation                    *
 **********************************************************************/
#include "gost_lcl.h"
#include "gost_params.h"
#include <string.h>
#include <openssl/rand.h>
#include <openssl/ecdsa.h>
#include <openssl/err.h>
#include "e_gost_err.h"
#ifdef DEBUG_SIGN
extern
void dump_signature(const char *message, const unsigned char *buffer,
                    size_t len);
void dump_dsa_sig(const char *message, DSA_SIG *sig);
#else

# define dump_signature(a,b,c)
# define dump_dsa_sig(a,b)
#endif

/*
 * Fills EC_KEY structure hidden in the app_data field of DSA structure
 * with parameter information, extracted from parameter array in
 * params.c file.
 *
 * Also fils DSA->q field with copy of EC_GROUP order field to make
 * DSA_size function work
 */
int fill_GOST2001_params(EC_KEY *eckey, int nid)
{
    R3410_2001_params *params = R3410_2001_paramset;
    EC_GROUP *grp = NULL;
    BIGNUM *p = NULL, *q = NULL, *a = NULL, *b = NULL, *x = NULL, *y = NULL;
    EC_POINT *P = NULL;
    BN_CTX *ctx = BN_CTX_new();
    int ok = 0;

    BN_CTX_start(ctx);
    p = BN_CTX_get(ctx);
    a = BN_CTX_get(ctx);
    b = BN_CTX_get(ctx);
    x = BN_CTX_get(ctx);
    y = BN_CTX_get(ctx);
    q = BN_CTX_get(ctx);
    while (params->nid != NID_undef && params->nid != nid)
        params++;
    if (params->nid == NID_undef) {
        GOSTerr(GOST_F_FILL_GOST2001_PARAMS,
                GOST_R_UNSUPPORTED_PARAMETER_SET);
        goto err;
    }
    BN_hex2bn(&p, params->p);
    BN_hex2bn(&a, params->a);
    BN_hex2bn(&b, params->b);

    grp = EC_GROUP_new_curve_GFp(p, a, b, ctx);

    P = EC_POINT_new(grp);

    BN_hex2bn(&x, params->x);
    BN_hex2bn(&y, params->y);
    EC_POINT_set_affine_coordinates_GFp(grp, P, x, y, ctx);
    BN_hex2bn(&q, params->q);
#ifdef DEBUG_KEYS
    fprintf(stderr, "Set params index %d oid %s\nq=",
            (params - R3410_2001_paramset), OBJ_nid2sn(params->nid));
    BN_print_fp(stderr, q);
    fprintf(stderr, "\n");
#endif

    EC_GROUP_set_generator(grp, P, q, NULL);
    EC_GROUP_set_curve_name(grp, params->nid);

    EC_KEY_set_group(eckey, grp);
    ok = 1;
 err:
    EC_POINT_free(P);
    EC_GROUP_free(grp);
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    return ok;
}

/*
 * Computes gost2001 signature as DSA_SIG structure
 *
 *
 */
DSA_SIG *gost2001_do_sign(const unsigned char *dgst, int dlen, EC_KEY *eckey)
{
    DSA_SIG *newsig = NULL;
    BIGNUM *md = hashsum2bn(dgst);
    BIGNUM *order = NULL;
    const EC_GROUP *group;
    const BIGNUM *priv_key;
    BIGNUM *r = NULL, *s = NULL, *X = NULL, *tmp = NULL, *tmp2 = NULL, *k =
        NULL, *e = NULL;
    EC_POINT *C = NULL;
    BN_CTX *ctx = BN_CTX_new();
    BN_CTX_start(ctx);
    OPENSSL_assert(dlen == 32);
    newsig = DSA_SIG_new();
    if (!newsig) {
        GOSTerr(GOST_F_GOST2001_DO_SIGN, GOST_R_NO_MEMORY);
        goto err;
    }
    group = EC_KEY_get0_group(eckey);
    order = BN_CTX_get(ctx);
    EC_GROUP_get_order(group, order, ctx);
    priv_key = EC_KEY_get0_private_key(eckey);
    e = BN_CTX_get(ctx);
    BN_mod(e, md, order, ctx);
#ifdef DEBUG_SIGN
    fprintf(stderr, "digest as bignum=");
    BN_print_fp(stderr, md);
    fprintf(stderr, "\ndigest mod q=");
    BN_print_fp(stderr, e);
    fprintf(stderr, "\n");
#endif
    if (BN_is_zero(e)) {
        BN_one(e);
    }
    k = BN_CTX_get(ctx);
    C = EC_POINT_new(group);
    do {
        do {
            if (!BN_rand_range(k, order)) {
                GOSTerr(GOST_F_GOST2001_DO_SIGN,
                        GOST_R_RANDOM_NUMBER_GENERATOR_FAILED);
                DSA_SIG_free(newsig);
                newsig = NULL;
                goto err;
            }
            if (!EC_POINT_mul(group, C, k, NULL, NULL, ctx)) {
                GOSTerr(GOST_F_GOST2001_DO_SIGN, ERR_R_EC_LIB);
                DSA_SIG_free(newsig);
                newsig = NULL;
                goto err;
            }
            if (!X)
                X = BN_CTX_get(ctx);
            if (!EC_POINT_get_affine_coordinates_GFp(group, C, X, NULL, ctx)) {
                GOSTerr(GOST_F_GOST2001_DO_SIGN, ERR_R_EC_LIB);
                DSA_SIG_free(newsig);
                newsig = NULL;
                goto err;
            }
            if (!r)
                r = BN_CTX_get(ctx);
            BN_nnmod(r, X, order, ctx);
        }
        while (BN_is_zero(r));
        /* s =  (r*priv_key+k*e) mod order */
        if (!tmp)
            tmp = BN_CTX_get(ctx);
        BN_mod_mul(tmp, priv_key, r, order, ctx);
        if (!tmp2)
            tmp2 = BN_CTX_get(ctx);
        BN_mod_mul(tmp2, k, e, order, ctx);
        if (!s)
            s = BN_CTX_get(ctx);
        BN_mod_add(s, tmp, tmp2, order, ctx);
    }
    while (BN_is_zero(s));

    newsig->s = BN_dup(s);
    newsig->r = BN_dup(r);
 err:
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    EC_POINT_free(C);
    BN_free(md);
    return newsig;
}

/*
 * Verifies gost 2001 signature
 *
 */
int gost2001_do_verify(const unsigned char *dgst, int dgst_len,
                       DSA_SIG *sig, EC_KEY *ec)
{
    BN_CTX *ctx = BN_CTX_new();
    const EC_GROUP *group = EC_KEY_get0_group(ec);
    BIGNUM *order;
    BIGNUM *md = NULL, *e = NULL, *R = NULL, *v = NULL, *z1 = NULL, *z2 =
        NULL;
    BIGNUM *X = NULL, *tmp = NULL;
    EC_POINT *C = NULL;
    const EC_POINT *pub_key = NULL;
    int ok = 0;

    BN_CTX_start(ctx);
    order = BN_CTX_get(ctx);
    e = BN_CTX_get(ctx);
    z1 = BN_CTX_get(ctx);
    z2 = BN_CTX_get(ctx);
    tmp = BN_CTX_get(ctx);
    X = BN_CTX_get(ctx);
    R = BN_CTX_get(ctx);
    v = BN_CTX_get(ctx);

    EC_GROUP_get_order(group, order, ctx);
    pub_key = EC_KEY_get0_public_key(ec);
    if (BN_is_zero(sig->s) || BN_is_zero(sig->r) ||
        (BN_cmp(sig->s, order) >= 1) || (BN_cmp(sig->r, order) >= 1)) {
        GOSTerr(GOST_F_GOST2001_DO_VERIFY,
                GOST_R_SIGNATURE_PARTS_GREATER_THAN_Q);
        goto err;

    }
    md = hashsum2bn(dgst);

    BN_mod(e, md, order, ctx);
#ifdef DEBUG_SIGN
    fprintf(stderr, "digest as bignum: ");
    BN_print_fp(stderr, md);
    fprintf(stderr, "\ndigest mod q: ");
    BN_print_fp(stderr, e);
#endif
    if (BN_is_zero(e))
        BN_one(e);
    v = BN_mod_inverse(v, e, order, ctx);
    BN_mod_mul(z1, sig->s, v, order, ctx);
    BN_sub(tmp, order, sig->r);
    BN_mod_mul(z2, tmp, v, order, ctx);
#ifdef DEBUG_SIGN
    fprintf(stderr, "\nInverted digest value: ");
    BN_print_fp(stderr, v);
    fprintf(stderr, "\nz1: ");
    BN_print_fp(stderr, z1);
    fprintf(stderr, "\nz2: ");
    BN_print_fp(stderr, z2);
#endif
    C = EC_POINT_new(group);
    if (!EC_POINT_mul(group, C, z1, pub_key, z2, ctx)) {
        GOSTerr(GOST_F_GOST2001_DO_VERIFY, ERR_R_EC_LIB);
        goto err;
    }
    if (!EC_POINT_get_affine_coordinates_GFp(group, C, X, NULL, ctx)) {
        GOSTerr(GOST_F_GOST2001_DO_VERIFY, ERR_R_EC_LIB);
        goto err;
    }
    BN_mod(R, X, order, ctx);
#ifdef DEBUG_SIGN
    fprintf(stderr, "\nX=");
    BN_print_fp(stderr, X);
    fprintf(stderr, "\nX mod q=");
    BN_print_fp(stderr, R);
    fprintf(stderr, "\n");
#endif
    if (BN_cmp(R, sig->r) != 0) {
        GOSTerr(GOST_F_GOST2001_DO_VERIFY, GOST_R_SIGNATURE_MISMATCH);
    } else {
        ok = 1;
    }
 err:
    EC_POINT_free(C);
    BN_CTX_end(ctx);
    BN_CTX_free(ctx);
    BN_free(md);
    return ok;
}

/*
 * Computes GOST R 34.10-2001 public key
 *
 *
 */
int gost2001_compute_public(EC_KEY *ec)
{
    const EC_GROUP *group = EC_KEY_get0_group(ec);
    EC_POINT *pub_key = NULL;
    const BIGNUM *priv_key = NULL;
    BN_CTX *ctx = NULL;
    int ok = 0;

    if (!group) {
        GOSTerr(GOST_F_GOST2001_COMPUTE_PUBLIC,
                GOST_R_KEY_IS_NOT_INITIALIZED);
        return 0;
    }
    ctx = BN_CTX_new();
    BN_CTX_start(ctx);
    if (!(priv_key = EC_KEY_get0_private_key(ec))) {
        GOSTerr(GOST_F_GOST2001_COMPUTE_PUBLIC, ERR_R_EC_LIB);
        goto err;
    }

    pub_key = EC_POINT_new(group);
    if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx)) {
        GOSTerr(GOST_F_GOST2001_COMPUTE_PUBLIC, ERR_R_EC_LIB);
        goto err;
    }
    if (!EC_KEY_set_public_key(ec, pub_key)) {
        GOSTerr(GOST_F_GOST2001_COMPUTE_PUBLIC, ERR_R_EC_LIB);
        goto err;
    }
    ok = 256;
 err:
    BN_CTX_end(ctx);
    EC_POINT_free(pub_key);
    BN_CTX_free(ctx);
    return ok;
}

/*
 *
 * Generates GOST R 34.10-2001 keypair
 *
 *
 */
int gost2001_keygen(EC_KEY *ec)
{
    BIGNUM *order = BN_new(), *d = BN_new();
    const EC_GROUP *group = EC_KEY_get0_group(ec);
    EC_GROUP_get_order(group, order, NULL);

    do {
        if (!BN_rand_range(d, order)) {
            GOSTerr(GOST_F_GOST2001_KEYGEN,
                    GOST_R_RANDOM_NUMBER_GENERATOR_FAILED);
            BN_free(d);
            BN_free(order);
            return 0;
        }
    }
    while (BN_is_zero(d));
    EC_KEY_set_private_key(ec, d);
    BN_free(d);
    BN_free(order);
    return gost2001_compute_public(ec);
}