/**********************************************************************
 *                             gost94_keyx.c                          *
 *             Copyright (c) 2005-2006 Cryptocom LTD                  *
 *         This file is distributed under the same license as OpenSSL *
 *                                                                    *
 *     Implements generation and parsing of GOST_KEY_TRANSPORT for    *
 *              GOST R 34.10-94 algorithms                            *
 *                                                                    *
 *          Requires OpenSSL 0.9.9 for compilation                    *
 **********************************************************************/
#include <string.h>
#include <openssl/dh.h>
#include <openssl/rand.h>
#include <openssl/evp.h>
#include <openssl/objects.h>

#include "gost89.h"
#include "gosthash.h"
#include "e_gost_err.h"
#include "gost_keywrap.h"
#include "gost_lcl.h"
/* Common functions for both 94 and 2001 key exchange schemes */
/*
 * Implementation of the Diffi-Hellman key agreement scheme based on GOST-94
 * keys
 */

/*
 * Computes Diffie-Hellman key and stores it into buffer in little-endian
 * byte order as expected by both versions of GOST 94 algorithm
 */
static int compute_pair_key_le(unsigned char *pair_key, BIGNUM *pub_key,
                               DH *dh)
{
    unsigned char be_key[128];
    int i, key_size;
    key_size = DH_compute_key(be_key, pub_key, dh);
    if (!key_size)
        return 0;
    memset(pair_key, 0, 128);
    for (i = 0; i < key_size; i++) {
        pair_key[i] = be_key[key_size - 1 - i];
    }
    return key_size;
}

/*
 * Computes 256 bit Key exchange key as specified in RFC 4357
 */
static int make_cp_exchange_key(BIGNUM *priv_key, EVP_PKEY *pubk,
                                unsigned char *shared_key)
{
    unsigned char dh_key[128];
    int ret;
    gost_hash_ctx hash_ctx;
    DH *dh = DH_new();

    if (!dh)
        return 0;
    memset(dh_key, 0, 128);
    dh->g = BN_dup(pubk->pkey.dsa->g);
    dh->p = BN_dup(pubk->pkey.dsa->p);
    dh->priv_key = BN_dup(priv_key);
    ret =
        compute_pair_key_le(dh_key, ((DSA *)(EVP_PKEY_get0(pubk)))->pub_key,
                            dh);
    DH_free(dh);
    if (!ret)
        return 0;
    init_gost_hash_ctx(&hash_ctx, &GostR3411_94_CryptoProParamSet);
    start_hash(&hash_ctx);
    hash_block(&hash_ctx, dh_key, 128);
    finish_hash(&hash_ctx, shared_key);
    done_gost_hash_ctx(&hash_ctx);
    return 1;
}

/* EVP_PKEY_METHOD callback derive. Implements VKO R 34.10-94 */

int pkey_gost94_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen)
{
    EVP_PKEY *pubk = EVP_PKEY_CTX_get0_peerkey(ctx);
    EVP_PKEY *mykey = EVP_PKEY_CTX_get0_pkey(ctx);
    *keylen = 32;
    if (key == NULL)
        return 1;

    return make_cp_exchange_key(gost_get0_priv_key(mykey), pubk, key);
}

/*
 * EVP_PKEY_METHOD callback encrypt for GOST R 34.10-94 cryptopro
 * modification
 */

int pkey_GOST94cp_encrypt(EVP_PKEY_CTX *ctx, unsigned char *out,
                          size_t *outlen, const unsigned char *key,
                          size_t key_len)
{
    GOST_KEY_TRANSPORT *gkt = NULL;
    unsigned char shared_key[32], ukm[8], crypted_key[44];
    const struct gost_cipher_info *param = get_encryption_params(NULL);
    EVP_PKEY *pubk = EVP_PKEY_CTX_get0_pkey(ctx);
    struct gost_pmeth_data *data = EVP_PKEY_CTX_get_data(ctx);
    gost_ctx cctx;
    int key_is_ephemeral = 1;
    EVP_PKEY *mykey = EVP_PKEY_CTX_get0_peerkey(ctx);

    /* Do not use vizir cipher parameters with cryptopro */
    if (!get_gost_engine_param(GOST_PARAM_CRYPT_PARAMS)
        && param == gost_cipher_list) {
        param = gost_cipher_list + 1;
    }

    if (mykey) {
        /* If key already set, it is not ephemeral */
        key_is_ephemeral = 0;
        if (!gost_get0_priv_key(mykey)) {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                    GOST_R_NO_PRIVATE_PART_OF_NON_EPHEMERAL_KEYPAIR);
            goto err;
        }
    } else {
        /* Otherwise generate ephemeral key */
        key_is_ephemeral = 1;
        if (out) {
            mykey = EVP_PKEY_new();
            EVP_PKEY_assign(mykey, EVP_PKEY_base_id(pubk), DSA_new());
            EVP_PKEY_copy_parameters(mykey, pubk);
            if (!gost_sign_keygen(EVP_PKEY_get0(mykey))) {
                goto err;
            }
        }
    }
    if (out)
        make_cp_exchange_key(gost_get0_priv_key(mykey), pubk, shared_key);
    if (data->shared_ukm) {
        memcpy(ukm, data->shared_ukm, 8);
    } else if (out) {
        if (RAND_bytes(ukm, 8) <= 0) {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                    GOST_R_RANDOM_GENERATOR_FAILURE);
            goto err;
        }
    }

    if (out) {
        gost_init(&cctx, param->sblock);
        keyWrapCryptoPro(&cctx, shared_key, ukm, key, crypted_key);
    }
    gkt = GOST_KEY_TRANSPORT_new();
    if (!gkt) {
        goto memerr;
    }
    if (!ASN1_OCTET_STRING_set(gkt->key_agreement_info->eph_iv, ukm, 8)) {
        goto memerr;
    }
    if (!ASN1_OCTET_STRING_set(gkt->key_info->imit, crypted_key + 40, 4)) {
        goto memerr;
    }
    if (!ASN1_OCTET_STRING_set
        (gkt->key_info->encrypted_key, crypted_key + 8, 32)) {
        goto memerr;
    }
    if (key_is_ephemeral) {
        if (!X509_PUBKEY_set
            (&gkt->key_agreement_info->ephem_key, out ? mykey : pubk)) {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                    GOST_R_CANNOT_PACK_EPHEMERAL_KEY);
            goto err;
        }
        if (out)
            EVP_PKEY_free(mykey);
    }
    ASN1_OBJECT_free(gkt->key_agreement_info->cipher);
    gkt->key_agreement_info->cipher = OBJ_nid2obj(param->nid);
    *outlen = i2d_GOST_KEY_TRANSPORT(gkt, out ? &out : NULL);
    if (*outlen <= 0) {
        GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT,
                GOST_R_ERROR_PACKING_KEY_TRANSPORT_INFO);
        goto err;
    }
    if (!key_is_ephemeral) {
        /* Set control "public key from client certificate used" */
        if (EVP_PKEY_CTX_ctrl(ctx, -1, -1, EVP_PKEY_CTRL_PEER_KEY, 3, NULL) <=
            0) {
            GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT, GOST_R_CTRL_CALL_FAILED);
            goto err;
        }
    }
    GOST_KEY_TRANSPORT_free(gkt);
    return 1;
 memerr:
    if (key_is_ephemeral) {
        EVP_PKEY_free(mykey);
    }
    GOSTerr(GOST_F_PKEY_GOST94CP_ENCRYPT, GOST_R_MALLOC_FAILURE);
 err:
    GOST_KEY_TRANSPORT_free(gkt);
    return -1;
}

/*
 * EVP_PLEY_METHOD callback decrypt for GOST R 34.10-94 cryptopro
 * modification
 */
int pkey_GOST94cp_decrypt(EVP_PKEY_CTX *ctx, unsigned char *key,
                          size_t *key_len, const unsigned char *in,
                          size_t in_len)
{
    const unsigned char *p = in;
    GOST_KEY_TRANSPORT *gkt = NULL;
    unsigned char wrappedKey[44];
    unsigned char sharedKey[32];
    gost_ctx cctx;
    const struct gost_cipher_info *param = NULL;
    EVP_PKEY *eph_key = NULL, *peerkey = NULL;
    EVP_PKEY *priv = EVP_PKEY_CTX_get0_pkey(ctx);

    if (!key) {
        *key_len = 32;
        return 1;
    }

    gkt = d2i_GOST_KEY_TRANSPORT(NULL, (const unsigned char **)&p, in_len);
    if (!gkt) {
        GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
                GOST_R_ERROR_PARSING_KEY_TRANSPORT_INFO);
        return 0;
    }
    eph_key = X509_PUBKEY_get(gkt->key_agreement_info->ephem_key);
    if (eph_key) {
        if (EVP_PKEY_derive_set_peer(ctx, eph_key) <= 0) {
            GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
                    GOST_R_INCOMPATIBLE_PEER_KEY);
            goto err;
        }
    } else {
        /* Set control "public key from client certificate used" */
        if (EVP_PKEY_CTX_ctrl(ctx, -1, -1, EVP_PKEY_CTRL_PEER_KEY, 3, NULL) <=
            0) {
            GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT, GOST_R_CTRL_CALL_FAILED);
            goto err;
        }
    }
    peerkey = EVP_PKEY_CTX_get0_peerkey(ctx);
    if (!peerkey) {
        GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT, GOST_R_NO_PEER_KEY);
        goto err;
    }

    param = get_encryption_params(gkt->key_agreement_info->cipher);
    if (!param) {
        goto err;
    }

    gost_init(&cctx, param->sblock);
    OPENSSL_assert(gkt->key_agreement_info->eph_iv->length == 8);
    memcpy(wrappedKey, gkt->key_agreement_info->eph_iv->data, 8);
    OPENSSL_assert(gkt->key_info->encrypted_key->length == 32);
    memcpy(wrappedKey + 8, gkt->key_info->encrypted_key->data, 32);
    OPENSSL_assert(gkt->key_info->imit->length == 4);
    memcpy(wrappedKey + 40, gkt->key_info->imit->data, 4);
    make_cp_exchange_key(gost_get0_priv_key(priv), peerkey, sharedKey);
    if (!keyUnwrapCryptoPro(&cctx, sharedKey, wrappedKey, key)) {
        GOSTerr(GOST_F_PKEY_GOST94CP_DECRYPT,
                GOST_R_ERROR_COMPUTING_SHARED_KEY);
        goto err;
    }

    EVP_PKEY_free(eph_key);
    GOST_KEY_TRANSPORT_free(gkt);
    return 1;
 err:
    EVP_PKEY_free(eph_key);
    GOST_KEY_TRANSPORT_free(gkt);
    return -1;
}
