<?php
/**
 * This file processes the login request and sends back a token response
 * if successful.
 */
$requestMethod = $_SERVER['REQUEST_METHOD'];

// retrieve the inbound parameters based on request type.
switch($requestMethod) {

    case 'POST':
        $username = '';
        $password = '';
    
        if (isset($_POST['username'])) {$username = $_POST['username'];}
        if (isset($_POST['password'])) {$password = $_POST['password'];}

        if (($username == 'john.doe') && ($password == 'foobar')) {

            require_once('jwt.php');

            /** 
             * Create some payload data with user data we would normally retrieve from a
             * database with users credentials. Then when the client sends back the token,
             * this payload data is available for us to use to retrieve other data 
             * if necessary.
             */
            $userId = 'USER123456';

            /**
             * Uncomment the following line and add an appropriate date to enable the 
             * "not before" feature.
             */
            // $nbf = strtotime('2021-01-01 00:00:01');

            /**
             * Uncomment the following line and add an appropriate date and time to enable the 
             * "expire" feature.
             */
            // $exp = strtotime('2021-01-01 00:00:01');

            // Get our server-side secret key from a secure location.
            $serverKey = '5f2b5cdbe5194f10b3241568fe4e2b24';

            // create a token
            $payloadArray = array();
            $payloadArray['userId'] = $userId;
            if (isset($nbf)) {$payloadArray['nbf'] = $nbf;}
            if (isset($exp)) {$payloadArray['exp'] = $exp;}
            $token = JWT::encode($payloadArray, $serverKey);

            // return to caller
            $returnArray = array('token' => $token);
            $jsonEncodedReturnArray = json_encode($returnArray, JSON_PRETTY_PRINT);
            echo $jsonEncodedReturnArray;

        } 
        else {
            $returnArray = array('error' => 'Invalid user ID or password.');
            $jsonEncodedReturnArray = json_encode($returnArray, JSON_PRETTY_PRINT);
            echo $jsonEncodedReturnArray;
        }

        break;

    case 'GET':

        $token = null;
        
        if (isset($_GET['token'])) {$token = $_GET['token'];}

        if (!is_null($token)) {

            require_once('jwt.php');

            // Get our server-side secret key from a secure location.
            $serverKey = '5f2b5cdbe5194f10b3241568fe4e2b24';

            try {
                $payload = JWT::decode($token, $serverKey, array('HS256'));
                $returnArray = array('userId' => $payload->userId);
                if (isset($payload->exp)) {
                    $returnArray['exp'] = date(DateTime::ISO8601, $payload->exp);;
                }
            }
            catch(Exception $e) {
                $returnArray = array('error' => $e->getMessage());
            }
        } 
        else {
            $returnArray = array('error' => 'You are not logged in with a valid token.');
        }
        
        // return to caller
        $jsonEncodedReturnArray = json_encode($returnArray, JSON_PRETTY_PRINT);
        echo $jsonEncodedReturnArray;

        break;

    default:
        $returnArray = array('error' => 'You have requested an invalid method.');
        $jsonEncodedReturnArray = json_encode($returnArray, JSON_PRETTY_PRINT);
        echo $jsonEncodedReturnArray;
}

<?php

/**
 * JSON Web Token implementation, based on this spec:
 * https://tools.ietf.org/html/rfc7519
 * 
 * This class library is based on original Firebase/JWT source code written by 
 * Neuman Vong and Anant Narayanan found here: https://github.com/firebase/php-jwt
 * 
 * @license  http://opensource.org/licenses/BSD-3-Clause 3-clause BSD
 * 
 */
class JWT {

    public static $leeway = 0;                      // allows for nbf, iat or exp clock skew
    public static $timestamp = null;                // allow timestamp to be specified for testing. Defaults to php (time) if null.
    public static $supported_algs = array(
        'HS256' => array('hash_hmac', 'SHA256'),
        'HS512' => array('hash_hmac', 'SHA512'),
        'HS384' => array('hash_hmac', 'SHA384'),
        'RS256' => array('openssl', 'SHA256'),
        'RS384' => array('openssl', 'SHA384'),
        'RS512' => array('openssl', 'SHA512'),
    );
    /** ----------------------------------------------------------------------------------------------------------
     * Decodes a JWT string into a PHP object.
     *
     * @param string        $token          The JSON web token
     * @param string|array  $key            The secret key                            
     * @param array         $allowed_algs   If the algorithm used is asymmetric, this is the public key list
     *                                      of supported verification algorithms. Supported algorithms are:
     *                                      'HS256', 'HS384', 'HS512' and 'RS256'
     *
     * @return object The JWT's payload as a PHP object
     *
     */
    public static function decode($token, $key, array $allowed_algs = array())
    {
        if ((!isset($timestamp)) || (is_null($timestamp))) {
            $timestamp = time();
        }
        
        if (empty($key)) {
            throw new Exception('Invalid or missing key.');
        }

        $tokenSegments = explode('.', $token);

        if (count($tokenSegments) != 3) {
            throw new Exception('Wrong number of segments');
        }

        list($headb64, $bodyb64, $cryptob64) = $tokenSegments;
        if (null === ($header = static::jsonDecode(static::urlsafeB64Decode($headb64)))) {
            throw new Exception('Invalid header encoding');
        }

        if (null === $payload = static::jsonDecode(static::urlsafeB64Decode($bodyb64))) {
            throw new Exception('Invalid claims encoding');
        }

        if (false === ($sig = static::urlsafeB64Decode($cryptob64))) {
            throw new Exception('Invalid signature encoding');
        }

        if (empty($header->alg)) {
            throw new Exception('Empty algorithm');
        }

        if (empty(static::$supported_algs[$header->alg])) {
            throw new Exception('Algorithm not supported');
        }

        if (!in_array($header->alg, $allowed_algs)) {
            throw new Exception('Algorithm not allowed');
        }

        if (is_array($key) || $key instanceof ArrayAccess) {
            if (isset($header->kid)) {
                if (!isset($key[$header->kid])) {
                    throw new UnexpectedValueException('"kid" invalid, unable to lookup correct key');
                }
                $key = $key[$header->kid];
            } else {
                throw new UnexpectedValueException('"kid" empty, unable to lookup correct key');
            }
        }

        // Check the signature
        if (!static::verify("$headb64.$bodyb64", $sig, $key, $header->alg)) {
            throw new Exception('Signature verification failed');
        }

        // Check if the nbf if it is defined. This is the time that the
        // token can actually be used. If it's not yet that time, abort.
        if (isset($payload->nbf) && $payload->nbf > ($timestamp + static::$leeway)) {
            throw new Exception(
                'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->nbf)
            );
        }

        // Check that this token has been created before 'now'. This prevents
        // using tokens that have been created for later use (and haven't
        // correctly used the nbf claim).
        if (isset($payload->iat) && $payload->iat > ($timestamp + static::$leeway)) {
            throw new Exception(
                'Cannot handle token prior to ' . date(DateTime::ISO8601, $payload->iat)
            );
        }
        
        // Check if this token has expired.
        if (isset($payload->exp) && ($timestamp - static::$leeway) >= $payload->exp) {
            throw new Exception('Expired token');
        }

        return $payload;
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Converts and signs a PHP object or array into a JWT string.
     *
     * @param object|array  $payload    PHP object or array
     * @param string        $key        The secret key.
     *                                  If the algorithm used is asymmetric, this is the private key
     * @param string        $alg        The signing algorithm.
     *                                  Supported algorithms are 'HS256', 'HS384', 'HS512' and 'RS256'
     * @param mixed         $keyId
     * @param array         $head       An array with header elements to attach
     *
     * @return string A signed JWT
     *
     */
    public static function encode($payload, $key, $alg = 'HS256', $keyId = null, $head = null)
    {
        $header = array('typ' => 'JWT', 'alg' => $alg);

        if ($keyId !== null) {
            $header['kid'] = $keyId;
        }

        if ( isset($head) && is_array($head) ) {
            $header = array_merge($head, $header);
        }

        $segments = array();
        $segments[] = static::urlsafeB64Encode(static::jsonEncode($header));
        $segments[] = static::urlsafeB64Encode(static::jsonEncode($payload));
        $signing_input = implode('.', $segments);
        $signature = static::sign($signing_input, $key, $alg);
        $segments[] = static::urlsafeB64Encode($signature);

        return implode('.', $segments);
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Sign a string with a given key and algorithm.
     *
     * @param string            $msg    The message to sign
     * @param string|resource   $key    The secret key
     * @param string            $alg    The signing algorithm.
     *                                  Supported algorithms are 'HS256', 'HS384', 'HS512' and 'RS256'
     *
     * @return string An encrypted message
     *
     */
    public static function sign($msg, $key, $alg = 'HS256')
    {
        if (empty(static::$supported_algs[$alg])) {
            throw new Exception('Algorithm not supported');
        }
        list($function, $algorithm) = static::$supported_algs[$alg];
        switch($function) {
            case 'hash_hmac':
                return hash_hmac($algorithm, $msg, $key, true);
            case 'openssl':
                $signature = '';
                $success = openssl_sign($msg, $signature, $key, $algorithm);
                if (!$success) {
                    throw new Exception("OpenSSL unable to sign data");
                } else {
                    return $signature;
                }
        }
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Verify a signature with the message, key and method. Not all methods
     * are symmetric, so we must have a separate verify and sign method.
     *
     * @param string            $msg        The original message (header and body)
     * @param string            $signature  The original signature
     * @param string|resource   $key        For HS*, a string key works. for RS*, must be a resource of an openssl public key
     * @param string            $alg        The algorithm
     *
     * @return bool
     */
    private static function verify($msg, $signature, $key, $alg)
    {
        if (empty(static::$supported_algs[$alg])) {
            throw new Exception('Algorithm not supported');
        }
        list($function, $algorithm) = static::$supported_algs[$alg];
        switch($function) {
            case 'openssl':
                $success = openssl_verify($msg, $signature, $key, $algorithm);
                if ($success === 1) {
                    return true;
                } elseif ($success === 0) {
                    return false;
                }
                // returns 1 on success, 0 on failure, -1 on error.
                throw new Exception(
                    'OpenSSL error: ' . openssl_error_string()
                );
            case 'hash_hmac':
            default:
                $hash = hash_hmac($algorithm, $msg, $key, true);
                if (function_exists('hash_equals')) {
                    return hash_equals($signature, $hash);
                }
                $len = min(static::safeStrlen($signature), static::safeStrlen($hash));
                $status = 0;
                for ($i = 0; $i < $len; $i++) {
                    $status |= (ord($signature[$i]) ^ ord($hash[$i]));
                }
                $status |= (static::safeStrlen($signature) ^ static::safeStrlen($hash));
                return ($status === 0);
        }
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Decode a JSON string into a PHP object.
     *
     * @param string $input JSON string
     *
     * @return object Object representation of JSON string
     *
     * @throws Exception Provided string was invalid JSON
     */
    public static function jsonDecode($input)
    {
        if (version_compare(PHP_VERSION, '5.4.0', '>=') && !(defined('JSON_C_VERSION') && PHP_INT_SIZE > 4)) {
            /** In PHP >=5.4.0, json_decode() accepts an options parameter, that allows you
             * to specify that large ints (like Steam Transaction IDs) should be treated as
             * strings, rather than the PHP default behaviour of converting them to floats.
             */
            $obj = json_decode($input, false, 512, JSON_BIGINT_AS_STRING);
        } else {
            /** Not all servers will support that, however, so for older versions we must
             * manually detect large ints in the JSON string and quote them (thus converting
             *them to strings) before decoding, hence the preg_replace() call.
             */
            $max_int_length = strlen((string) PHP_INT_MAX) - 1;
            $json_without_bigints = preg_replace('/:\s*(-?\d{'.$max_int_length.',})/', ': "$1"', $input);
            $obj = json_decode($json_without_bigints);
        }
        if (function_exists('json_last_error') && $errno = json_last_error()) {
            static::handleJsonError($errno);
        } elseif ($obj === null && $input !== 'null') {
            throw new Exception('Null result with non-null input');
        }
        return $obj;
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Encode a PHP object into a JSON string.
     *
     * @param object|array $input A PHP object or array
     *
     * @return string JSON representation of the PHP object or array
     *
     * @throws Exception Provided object could not be encoded to valid JSON
     */
    public static function jsonEncode($input)
    {
        $json = json_encode($input);
        if (function_exists('json_last_error') && $errno = json_last_error()) {
            static::handleJsonError($errno);
        } elseif ($json === 'null' && $input !== null) {
            throw new Exception('Null result with non-null input');
        }
        return $json;
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Decode a string with URL-safe Base64.
     *
     * @param string $input A Base64 encoded string
     *
     * @return string A decoded string
     */
    public static function urlsafeB64Decode($input)
    {
        $remainder = strlen($input) % 4;
        if ($remainder) {
            $padlen = 4 - $remainder;
            $input .= str_repeat('=', $padlen);
        }
        return base64_decode(strtr($input, '-_', '+/'));
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Encode a string with URL-safe Base64.
     *
     * @param string $input The string you want encoded
     *
     * @return string The base64 encode of what you passed in
     */
    public static function urlsafeB64Encode($input)
    {
        return str_replace('=', '', strtr(base64_encode($input), '+/', '-_'));
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Helper method to create a JSON error.
     *
     * @param int $errno An error number from json_last_error()
     *
     * @return void
     */
    private static function handleJsonError($errno)
    {
        $messages = array(
            JSON_ERROR_DEPTH => 'Maximum stack depth exceeded',
            JSON_ERROR_STATE_MISMATCH => 'Invalid or malformed JSON',
            JSON_ERROR_CTRL_CHAR => 'Unexpected control character found',
            JSON_ERROR_SYNTAX => 'Syntax error, malformed JSON',
            JSON_ERROR_UTF8 => 'Malformed UTF-8 characters' //PHP >= 5.3.3
        );
        throw new Exception(
            isset($messages[$errno])
            ? $messages[$errno]
            : 'Unknown JSON error: ' . $errno
        );
    }
    /** ----------------------------------------------------------------------------------------------------------
     * Get the number of bytes in cryptographic strings.
     *
     * @param string
     *
     * @return int
     */
    private static function safeStrlen($str)
    {
        if (function_exists('mb_strlen')) {
            return mb_strlen($str, '8bit');
        }
        return strlen($str);
    }
}

<?php

echo "Chiffrage\n";
$key = random_bytes(SODIUM_CRYPTO_SECRETBOX_KEYBYTES);
$nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
$ciphertext = sodium_crypto_secretbox('This is a secret!', $nonce, $key);
$encoded = base64_encode($nonce . $ciphertext);
var_dump($encoded);
echo "Déchiffrage\n";
$decoded = base64_decode($encoded);
$nonce = mb_substr($decoded, 0, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES, '8bit');
$ciphertext = mb_substr($decoded, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES, null, '8bit');
$plaintext = sodium_crypto_secretbox_open($ciphertext, $nonce, $key);
var_dump($plaintext);

$msg = 'This is a super secret message!';

// Generating an encryption key and a nonce
$key   = random_bytes(SODIUM_CRYPTO_SECRETBOX_KEYBYTES); // 256 bit
$nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES); // 24 bytes

// Encrypt
$ciphertext = sodium_crypto_secretbox($msg, $nonce, $key);
// Decrypt
$plaintext = sodium_crypto_secretbox_open($ciphertext, $nonce, $key);

echo $plaintext === $msg ? 'Success' : 'Error';

$msg = 'This is the message to authenticate!';
$key = random_bytes(SODIUM_CRYPTO_SECRETBOX_KEYBYTES); // 256 bit
 
// Generate the Message Authentication Code
$mac = sodium_crypto_auth($msg, $key);
 
// Altering $mac or $msg, verification will fail
echo sodium_crypto_auth_verify($mac, $msg, $key) ? 'Success' : 'Error';

$password = 'password';
echo "\nArgon2i with Sodium\n";
$hash = sodium_crypto_pwhash_str(
    $password,
    SODIUM_CRYPTO_PWHASH_OPSLIMIT_INTERACTIVE,
    SODIUM_CRYPTO_PWHASH_MEMLIMIT_INTERACTIVE
); // 97 bytes

echo sodium_crypto_pwhash_str_verify($hash, $password) ?
     'OK' : 'Error';

echo "\nArgon2i without Sodium\n";
$hash = password_hash($password, PASSWORD_ARGON2I); // 95 bytes

echo password_verify($password, $hash) ? 'OK' : 'Error';

?>