<?php
/******************************************************************************
 * This file is part of the Phactor PHP project. You can always find the latest
 * version of this class and project at: https://github.com/ionux/phactor
 *
 * Copyright (c) 2015-2018 Rich Morgan, rich@richmorgan.me
 *
 * The MIT License (MIT)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of
 * this software and associated documentation files (the "Software"), to deal in
 * the Software without restriction, including without limitation the rights to
 * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
 * the Software, and to permit persons to whom the Software is furnished to do so,
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
 * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
 * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
 * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 ******************************************************************************/

namespace Phactor;

/**
 * Abstract Syntax Notation One (ASN.1) encoding trait for keys and signatures.
 *
 * @author Rich Morgan <rich@richmorgan.me>
 */
trait ASN1
{
    /**
     * Encodes keypair data to PEM format.
     *
     * @param  array  $keypair The keypair info.
     * @return string          The data to decode.
     */
    public function encodePEM($keypair)
    {
        $this->pemInitialDataCheck($keypair);

        $ecpemstruct = array(
                             'sequence_beg' => '30',
                             'total_len'    => '74',
                             'int_sec_beg'  => '02',
                             'int_sec_len'  => '01',
                             'int_sec_val'  => '01',
                             'oct_sec_beg'  => '04',
                             'oct_sec_len'  => '20',
                             'oct_sec_val'  => $keypair[0],
                             'a0_ele_beg'   => 'a0',
                             'a0_ele_len'   => '07',
                             'obj_id_beg'   => '06',
                             'obj_id_len'   => '05',
                             'obj_id_val'   => '2b8104000a',
                             'a1_ele_beg'   => 'a1',
                             'a1_ele_len'   => '44',
                             'bit_str_beg'  => '03',
                             'bit_str_len'  => '42',
                             'bit_str_val'  => '00' . $keypair[1],
                             );

        $dec = trim(implode($ecpemstruct));

        $this->pemDataLenCheck($dec);

        return '-----BEGIN EC PRIVATE KEY-----' . "\r\n" . chunk_split(base64_encode($this->binConv($dec)), 64) . '-----END EC PRIVATE KEY-----';
    }

    /**
     * Decodes PEM data to retrieve the keypair.
     *
     * @param  string $pem_data The data to decode.
     * @return array            The keypair info.
     */
    public function decodePEM($pem_data)
    {
        $pem_data = $this->pemDataClean($pem_data);
        $decoded  = bin2hex(base64_decode($pem_data));

        $this->pemDataLenCheck($decoded);

        $ecpemstruct = array(
                             'oct_sec_val'  => substr($decoded, 14, 64),
                             'obj_id_val'   => substr($decoded, 86, 10),
                             'bit_str_val'  => substr($decoded, 106),
                            );

        $this->pemOidCheck($ecpemstruct['obj_id_val']);

        $private_key = $ecpemstruct['oct_sec_val'];
        $public_key  = '04' . $ecpemstruct['bit_str_val'];

        $this->pemKeyLenCheck(array($private_key, $public_key));

        return array(
                     'private_key' => $private_key,
                     'public_key'  => $public_key
                    );
    }

    /**
     * Ensures the data we want to PEM encode is acceptable.
     *
     * @param  array     $keypair The values to check.
     * @throws \Exception
     */
    private function pemInitialDataCheck($keypair)
    {
        if (true === empty($keypair) || false === is_array($keypair) || strlen($keypair[0]) < 62 || strlen($keypair[1]) < 126) {
            throw new \Exception('Invalid or corrupt secp256k1 keypair provided.  Cannot encode the keys to PEM format.  Value checked was "' . var_export($keypair, true) . '".');
        }
    }

    /**
     * Ensures the decoded PEM data length is acceptable.
     *
     * @param  string     $value The value to check.
     * @throws \Exception
     */
    private function pemDataLenCheck($value)
    {
        if (strlen($value) < 220) {
            throw new \Exception('Invalid or corrupt secp256k1 key provided. Cannot decode the supplied PEM data. Length < 220.  Value received was "' . var_export($value, true) . '".');
        }
    }

    /**
     * Ensures the decoded PEM key lengths are acceptable.
     *
     * @param  array     $values The key values to check.
     * @throws \Exception
     */
    private function pemKeyLenCheck($values)
    {
        if (!is_array($values) || strlen($values[0]) < 62 || strlen($values[1]) < 126) {
            throw new \Exception('Invalid or corrupt secp256k1 key provided. Cannot decode the supplied PEM data. Key lengths too short.  Values checked were "' . var_export($values[0], true) . '" and "' . var_export($values[1], true) . '".');
        }
    }

    /**
     * Ensures the decoded PEM data is for an EC Key.
     *
     * @param  string     $value The value to check.
     * @throws \Exception
     */
    private function pemOidCheck($value)
    {
        if ($value != '2b8104000a') {
            throw new \Exception('Invalid or corrupt secp256k1 key provided. Cannot decode the supplied PEM data. OID is not for EC key.  Value checked was "' . var_export($value, true) . '".');
        }
    }

    /**
     * Cleans the PEM data of unwanted data.
     *
     * @param  string  $value The value to clean.
     * @return string  $value The cleaned value.
     */
    private function pemDataClean($value)
    {
        $value = str_ireplace('-----BEGIN EC PRIVATE KEY-----', '', $value);
        $value = str_ireplace('-----END EC PRIVATE KEY-----', '', $value);
        $value = str_ireplace("\r", '', trim($value));
        $value = str_ireplace("\n", '', trim($value));
        $value = str_ireplace(' ', '', trim($value));

        return $value;
    }

    /**
     * Decodes an OID hex value obtained from
     * a PEM file or other encoded key file.
     *
     * @param  string $data The hex OID string to decode.
     * @return string       The decoded OID string.
     */
    public function decodeOID($data)
    {
        $bin_data      = array();
        $index         = 0;
        $binary_string = '';
        $oid           = array();

        // first two numbers are: (40*x)+y
        // all next chars are 7-bit numbers
        foreach ($data as $key => $value) {
            $bin_data[$index] = bitConv($value);
            $binary_string   .= $bin_data[$index];
            $index++;
        }

        $oid[0] = (int)($data[0] / 0x28);
        $oid[1] = $data[0] % 0x28;

        $elements    = count($bin_data);
        $temp_number = '00000000';

        for ($x = 1; $x < $elements; $x++) {
            $and_temp = $bin_data[$x] & '01111111';

            $temp_number = bitAdd($temp_number, $and_temp);

            if (substr($bin_data[$x], 0, 1) == '0') {
                // This is a final value without
                // a value preceeding it.
                $oid[$x + 1] = decConv($temp_number);
                $temp_number = '';
            } else {
                $temp_number = shiftLeft($temp_number, 7);
            }
        }

        $oid_string = '';

        foreach ($oid as $key => $value) {
            $oid_string .= $value . ".";
        }

        $oid_string = substr($oid_string, 0, -1);

        return $oid_string;
    }
}