/*
 * %CopyrightBegin%
 *
 * Copyright Ericsson AB 2010-2018. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * %CopyrightEnd%
 */

#include "evp.h"

ERL_NIF_TERM evp_compute_key_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
    /*    (Curve, PeerBin, MyBin) */
{
#ifdef HAVE_ED_CURVE_DH
    int type;
    EVP_PKEY_CTX *ctx = NULL;
    ErlNifBinary peer_bin, my_bin, key_bin;
    EVP_PKEY *peer_key = NULL, *my_key = NULL;
    size_t max_size;

    if (argv[0] == atom_x25519) type = EVP_PKEY_X25519;
    else if (argv[0] == atom_x448) type = EVP_PKEY_X448;
    else return enif_make_badarg(env);

    if (!enif_inspect_binary(env, argv[1], &peer_bin) ||
        !enif_inspect_binary(env, argv[2], &my_bin)) 
        goto return_badarg;

    if (!(my_key = EVP_PKEY_new_raw_private_key(type, NULL, my_bin.data, my_bin.size)) ||
        !(ctx = EVP_PKEY_CTX_new(my_key, NULL))) 
        goto return_badarg;

    if (!EVP_PKEY_derive_init(ctx)) 
        goto return_badarg;

    if (!(peer_key = EVP_PKEY_new_raw_public_key(type, NULL, peer_bin.data, peer_bin.size)) ||
        !EVP_PKEY_derive_set_peer(ctx, peer_key)) 
        goto return_badarg;

    if (!EVP_PKEY_derive(ctx, NULL, &max_size)) 
        goto return_badarg;

    if (!enif_alloc_binary(max_size, &key_bin) ||
        !EVP_PKEY_derive(ctx, key_bin.data, &key_bin.size)) 
        goto return_badarg;

    if (key_bin.size < max_size) {
        size_t actual_size = key_bin.size;
        if (!enif_realloc_binary(&key_bin, actual_size)) 
            goto return_badarg;
    }

    EVP_PKEY_free(my_key);
    EVP_PKEY_free(peer_key);
    EVP_PKEY_CTX_free(ctx);
    return enif_make_binary(env, &key_bin);

return_badarg:
    if (my_key)   EVP_PKEY_free(my_key);
    if (peer_key) EVP_PKEY_free(peer_key);
    if (ctx)      EVP_PKEY_CTX_free(ctx);
    return enif_make_badarg(env);
#else
    return atom_notsup;
#endif
}

ERL_NIF_TERM evp_generate_key_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
/* (Curve) */
{
#ifdef HAVE_ED_CURVE_DH
    int type;
    EVP_PKEY_CTX *ctx = NULL;
    EVP_PKEY *pkey = NULL;
    ERL_NIF_TERM ret_pub, ret_prv;
    size_t key_len;

    if (argv[0] == atom_x25519) type = EVP_PKEY_X25519;
    else if (argv[0] == atom_x448) type = EVP_PKEY_X448;
    else return enif_make_badarg(env);

    if (!(ctx = EVP_PKEY_CTX_new_id(type, NULL))) return enif_make_badarg(env);

    if (!EVP_PKEY_keygen_init(ctx)) goto return_error;
    if (!EVP_PKEY_keygen(ctx, &pkey)) goto return_error;

    if (!EVP_PKEY_get_raw_public_key(pkey, NULL, &key_len)) goto return_error;
    if (!EVP_PKEY_get_raw_public_key(pkey,
                                     enif_make_new_binary(env, key_len, &ret_pub),
                                     &key_len))
        goto return_error;

    if (!EVP_PKEY_get_raw_private_key(pkey, NULL, &key_len)) goto return_error;
    if (!EVP_PKEY_get_raw_private_key(pkey,
                                      enif_make_new_binary(env, key_len, &ret_prv),
                                      &key_len))
        goto return_error;

    EVP_PKEY_free(pkey);
    EVP_PKEY_CTX_free(ctx);
    return enif_make_tuple2(env, ret_pub, ret_prv);

return_error:
    if (pkey) EVP_PKEY_free(pkey);
    if (ctx)  EVP_PKEY_CTX_free(ctx);
    return atom_error;

#else
    return atom_notsup;
#endif
}