129 lines
3.9 KiB
PHP
Executable File
129 lines
3.9 KiB
PHP
Executable File
<?php
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/**
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* Paytm uses checksum signature to ensure that API requests and responses shared between your
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* application and Paytm over network have not been tampered with. We use SHA256 hashing and
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* AES128 encryption algorithm to ensure the safety of transaction data.
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*
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* @author Lalit Kumar
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* @version 2.0
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* @link https://developer.paytm.com/docs/checksum/#php
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*/
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class PaytmChecksum{
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private static $iv = "@@@@&&&&####$$$$";
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static public function encrypt($input, $key) {
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$key = html_entity_decode($key);
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if(function_exists('openssl_encrypt')){
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$data = openssl_encrypt ( $input , "AES-128-CBC" , $key, 0, self::$iv );
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} else {
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$size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, 'cbc');
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$input = self::pkcs5Pad($input, $size);
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$td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', 'cbc', '');
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mcrypt_generic_init($td, $key, self::$iv);
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$data = mcrypt_generic($td, $input);
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mcrypt_generic_deinit($td);
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mcrypt_module_close($td);
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$data = base64_encode($data);
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}
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return $data;
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}
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static public function decrypt($encrypted, $key) {
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$key = html_entity_decode($key);
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if(function_exists('openssl_decrypt')){
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$data = openssl_decrypt ( $encrypted , "AES-128-CBC" , $key, 0, self::$iv );
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} else {
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$encrypted = base64_decode($encrypted);
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$td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', 'cbc', '');
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mcrypt_generic_init($td, $key, self::$iv);
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$data = mdecrypt_generic($td, $encrypted);
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mcrypt_generic_deinit($td);
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mcrypt_module_close($td);
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$data = self::pkcs5Unpad($data);
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$data = rtrim($data);
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}
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return $data;
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}
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static public function generateSignature($params, $key) {
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if(!is_array($params) && !is_string($params)){
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throw new Exception("string or array expected, ".gettype($params)." given");
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}
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if(is_array($params)){
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$params = self::getStringByParams($params);
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}
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return self::generateSignatureByString($params, $key);
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}
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static public function verifySignature($params, $key, $checksum){
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if(!is_array($params) && !is_string($params)){
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throw new Exception("string or array expected, ".gettype($params)." given");
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}
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if(isset($params['CHECKSUMHASH'])){
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unset($params['CHECKSUMHASH']);
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}
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if(is_array($params)){
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$params = self::getStringByParams($params);
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}
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return self::verifySignatureByString($params, $key, $checksum);
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}
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static private function generateSignatureByString($params, $key){
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$salt = self::generateRandomString(4);
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return self::calculateChecksum($params, $key, $salt);
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}
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static private function verifySignatureByString($params, $key, $checksum){
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$paytm_hash = self::decrypt($checksum, $key);
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$salt = substr($paytm_hash, -4);
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return $paytm_hash == self::calculateHash($params, $salt) ? true : false;
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}
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static private function generateRandomString($length) {
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$random = "";
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srand((double) microtime() * 1000000);
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$data = "9876543210ZYXWVUTSRQPONMLKJIHGFEDCBAabcdefghijklmnopqrstuvwxyz!@#$&_";
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for ($i = 0; $i < $length; $i++) {
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$random .= substr($data, (rand() % (strlen($data))), 1);
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}
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return $random;
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}
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static private function getStringByParams($params) {
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ksort($params);
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$params = array_map(function ($value){
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return ($value !== null && strtolower($value) !== "null") ? $value : "";
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}, $params);
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return implode("|", $params);
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}
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static private function calculateHash($params, $salt){
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$finalString = $params . "|" . $salt;
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$hash = hash("sha256", $finalString);
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return $hash . $salt;
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}
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static private function calculateChecksum($params, $key, $salt){
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$hashString = self::calculateHash($params, $salt);
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return self::encrypt($hashString, $key);
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}
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static private function pkcs5Pad($text, $blocksize) {
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$pad = $blocksize - (strlen($text) % $blocksize);
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return $text . str_repeat(chr($pad), $pad);
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}
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static private function pkcs5Unpad($text) {
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$pad = ord($text[strlen($text) - 1]);
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if ($pad > strlen($text))
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return false;
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return substr($text, 0, -1 * $pad);
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}
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} |