/**
 * crypt.c: pseudo OO wrapper around libmcrypt.
 * Copyright (C) 2011  Georg Hopp
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include <stdarg.h>
#include <stdlib.h>
#include <fcntl.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <mcrypt.h>
#include <mhash.h>

#include "token/cclass.h"
#include "token/crypt.h"


static
void
__construct(struct CRYPT * _this, va_list * params)
{
    _this->algorithm = va_arg(* params, const char * const);
    _this->mode      = va_arg(* params, const char * const);

    _this->mcrypt = mcrypt_module_open(
            (char *)_this->algorithm,
            NULL,
            (char *)_this->mode,
            NULL);

    _this->ivsize  = mcrypt_enc_get_iv_size(_this->mcrypt);
    _this->keysize = mcrypt_enc_get_key_size(_this->mcrypt);
}

static
void
__destruct(struct CRYPT * _this)
{
    if (_this->iv) {
        free(_this->iv);
    }

    mcrypt_module_close(_this->mcrypt);
}

static const
struct CCLASS _crypt = {
    sizeof(struct CRYPT),
    (ctor)__construct,
    NULL,
    (dtor)__destruct,
    NULL
};

const struct CCLASS * const CRYPT = &_crypt;

void *
crypt_createIv(struct CRYPT * _this)
{
    int    urandom;
    size_t rsize  = 0;
    void * iv = NULL;

    iv = calloc(_this->ivsize, sizeof(char));

    urandom = open("/dev/urandom", O_RDONLY);
    rsize   = read(urandom, iv, _this->ivsize);

    if (_this->ivsize != rsize) {
        free(iv);
        iv = NULL;
    }

    return iv;
}

static
void *
createKey(struct CRYPT * _this, const char * const password)
{
    void * key = NULL;

    key = calloc(_this->keysize, sizeof(char));

    mhash_keygen(
            KEYGEN_MCRYPT,
            MHASH_SHA256,
            mhash_keygen_count(),
            key,
            _this->keysize,
            NULL,
            0,
            (char *)password, // @TODO: bad karma...now this might change password.
            strlen(password));

    return key;
}

void *
crypt_encrypt(
        struct CRYPT * _this,
        const void * const data,
        const char * const password,
        size_t * length)
{
    char * encrypted;
    void * iv;
    void * key;

    key = createKey(_this, password);
    if(_this->iv) {
        iv = _this->iv;
    } else {
        iv = crypt_createIv(_this);
    }

    mcrypt_generic_init(_this->mcrypt, key, _this->keysize, iv);

    encrypted = calloc(_this->ivsize + *length, sizeof(char));
    memcpy(encrypted, iv, _this->ivsize);
    memcpy(encrypted + _this->ivsize, data, *length);

    mcrypt_generic(_this->mcrypt, encrypted + _this->ivsize, *length);
    mcrypt_generic_deinit(_this->mcrypt);
    *length += _this->ivsize;

    free(key);
    if (_this->iv != iv) {
        free(iv);
    }

    return encrypted;
}

void *
crypt_decrypt(
        struct CRYPT * _this,
        const void * const data,
        const char * const password,
        size_t * length)
{
    char * decrypted;
    void * iv;
    void * key;

    key = createKey(_this, password);
    iv  = calloc(_this->ivsize, sizeof(char));
    memcpy(iv, data, _this->ivsize);

    mcrypt_generic_init(_this->mcrypt, key, _this->keysize, iv);

    *length -= _this->ivsize;
    decrypted = calloc(*length, sizeof(char));
    memcpy(decrypted, data + _this->ivsize, *length);

    mdecrypt_generic(_this->mcrypt, decrypted, *length);
    mcrypt_generic_deinit(_this->mcrypt);

    free(key);
    free(iv);

    return decrypted;
}

// vim: set et ts=4 sw=4: