index.js

var jws = require('jws');
var ms = require('ms');
var JWT = module.exports;

var JsonWebTokenError = JWT.JsonWebTokenError = require('./lib/JsonWebTokenError');
var NotBeforeError = module.exports.NotBeforeError = require('./lib/NotBeforeError');
var TokenExpiredError = JWT.TokenExpiredError = require('./lib/TokenExpiredError');

JWT.decode = function (jwt, options) {
  options = options || {};
  var decoded = jws.decode(jwt, options);
  if (!decoded) { return null; }
  var payload = decoded.payload;

  //try parse the payload
  if(typeof payload === 'string') {
    try {
      var obj = JSON.parse(payload);
      if(typeof obj === 'object') {
        payload = obj;
      }
    } catch (e) { }
  }

  //return header if `complete` option is enabled.  header includes claims
  //such as `kid` and `alg` used to select the key within a JWKS needed to
  //verify the signature
  if (options.complete === true) {
    return {
      header: decoded.header,
      payload: payload,
      signature: decoded.signature
    };
  }
  return payload;
};

JWT.sign = require('./sign');

JWT.verify = function(jwtString, secretOrPublicKey, options, callback) {
  if ((typeof options === 'function') && !callback) {
    callback = options;
    options = {};
  }

  if (!options) options = {};

  var done;

  if (callback) {
    done = function() {
      var args = Array.prototype.slice.call(arguments, 0);
      return process.nextTick(function() {
        callback.apply(null, args);
      });
    };
  } else {
    done = function(err, data) {
      if (err) throw err;
      return data;
    };
  }

  if (!jwtString){
    return done(new JsonWebTokenError('jwt must be provided'));
  }

  var parts = jwtString.split('.');

  if (parts.length !== 3){
    return done(new JsonWebTokenError('jwt malformed'));
  }

  var hasSignature = parts[2].trim() !== '';

  if (!hasSignature && secretOrPublicKey){
    return done(new JsonWebTokenError('jwt signature is required'));
  }

  if (hasSignature && !secretOrPublicKey) {
    return done(new JsonWebTokenError('secret or public key must be provided'));
  }

  if (!hasSignature && !options.algorithms) {
    options.algorithms = ['none'];
  }

  if (!options.algorithms) {
    options.algorithms = ~secretOrPublicKey.toString().indexOf('BEGIN CERTIFICATE') ||
                         ~secretOrPublicKey.toString().indexOf('BEGIN PUBLIC KEY') ?
                          [ 'RS256','RS384','RS512','ES256','ES384','ES512' ] :
                         ~secretOrPublicKey.toString().indexOf('BEGIN RSA PUBLIC KEY') ?
                          [ 'RS256','RS384','RS512' ] :
                          [ 'HS256','HS384','HS512' ];

  }

  var decodedToken;
  try {
    decodedToken = jws.decode(jwtString);
  } catch(err) {
    return done(new JsonWebTokenError('invalid token'));
  }

  if (!decodedToken) {
    return done(new JsonWebTokenError('invalid token'));
  }

  var header = decodedToken.header;

  if (!~options.algorithms.indexOf(header.alg)) {
    return done(new JsonWebTokenError('invalid algorithm'));
  }

  var valid;

  try {
    valid = jws.verify(jwtString, header.alg, secretOrPublicKey);
  } catch (e) {
    return done(e);
  }

  if (!valid)
    return done(new JsonWebTokenError('invalid signature'));

  var payload;

  try {
    payload = JWT.decode(jwtString);
  } catch(err) {
    return done(err);
  }

  if (typeof payload.nbf !== 'undefined' && !options.ignoreNotBefore) {
    if (typeof payload.nbf !== 'number') {
      return done(new JsonWebTokenError('invalid nbf value'));
    }
    if (payload.nbf > Math.floor(Date.now() / 1000) + (options.clockTolerance || 0)) {
      return done(new NotBeforeError('jwt not active', new Date(payload.nbf * 1000)));
    }
  }

  if (typeof payload.exp !== 'undefined' && !options.ignoreExpiration) {
    if (typeof payload.exp !== 'number') {
      return done(new JsonWebTokenError('invalid exp value'));
    }
    if (Math.floor(Date.now() / 1000) >= payload.exp + (options.clockTolerance || 0)) {
      return done(new TokenExpiredError('jwt expired', new Date(payload.exp * 1000)));
    }
  }

  if (options.audience) {
    var audiences = Array.isArray(options.audience)? options.audience : [options.audience];
    var target = Array.isArray(payload.aud) ? payload.aud : [payload.aud];

    var match = target.some(function(aud) { return audiences.indexOf(aud) != -1; });

    if (!match)
      return done(new JsonWebTokenError('jwt audience invalid. expected: ' + audiences.join(' or ')));
  }

  if (options.issuer) {
    var invalid_issuer =
        (typeof options.issuer === 'string' && payload.iss !== options.issuer) ||
        (Array.isArray(options.issuer) && options.issuer.indexOf(payload.iss) === -1);

    if (invalid_issuer) {
      return done(new JsonWebTokenError('jwt issuer invalid. expected: ' + options.issuer));
    }
  }

  if (options.subject) {
    if (payload.sub !== options.subject) {
      return done(new JsonWebTokenError('jwt subject invalid. expected: ' + options.subject));
    }
  }

  if (options.jwtid) {
    if (payload.jti !== options.jwtid) {
      return done(new JsonWebTokenError('jwt jwtid invalid. expected: ' + options.jwtid));
    }
  }

  if (options.maxAge) {
    var maxAge = ms(options.maxAge);
    if (typeof payload.iat !== 'number') {
      return done(new JsonWebTokenError('iat required when maxAge is specified'));
    }
    if (Date.now() - (payload.iat * 1000) > maxAge + (options.clockTolerance || 0) * 1000) {
      return done(new TokenExpiredError('maxAge exceeded', new Date(payload.iat * 1000 + maxAge)));
    }
  }

  return done(null, payload);
};