1  /**
 2   * Module dependencies.
 3   */
 4  
 5  var crypto = require('crypto');
 6  
 7  /**
 8   * Sign the given `val` with `secret`.
 9   *
10   * @param {String} val
11   * @param {String|NodeJS.ArrayBufferView|crypto.KeyObject} secret
12   * @return {String}
13   * @api private
14   */
15  
16  exports.sign = function(val, secret){
17    if ('string' !== typeof val) throw new TypeError("Cookie value must be provided as a string.");
18    if (null == secret) throw new TypeError("Secret key must be provided.");
19    return val + '.' + crypto
20      .createHmac('sha256', secret)
21      .update(val)
22      .digest('base64')
23      .replace(/\=+$/, '');
24  };
25  
26  /**
27   * Unsign and decode the given `val` with `secret`,
28   * returning `false` if the signature is invalid.
29   *
30   * @param {String} val
31   * @param {String|NodeJS.ArrayBufferView|crypto.KeyObject} secret
32   * @return {String|Boolean}
33   * @api private
34   */
35  
36  exports.unsign = function(val, secret){
37    if ('string' !== typeof val) throw new TypeError("Signed cookie string must be provided.");
38    if (null == secret) throw new TypeError("Secret key must be provided.");
39    var str = val.slice(0, val.lastIndexOf('.'))
40      , mac = exports.sign(str, secret);
41    
42    return sha1(mac) == sha1(val) ? str : false;
43  };
44  
45  /**
46   * Private
47   */
48  
49  function sha1(str){
50    return crypto.createHash('sha1').update(str).digest('hex');
51  }