crypto.pbkdf2 fails silently with NaN bitlength #2987

    'use strict';

    function sha256(buf) {
      return crypto.createHash('sha256').update(buf).digest('hex');
    }

    var crypto = require('crypto');
    var secret = 'my special secret';
    var appPbkdf2Salt = sha256(new Buffer("MY_SALT"));
    var iterations = 1000;
    var bitLength; // oops, forgot to define bit length
    var keyByteLength = bitLength / 8;
    var hashname = 'sha256';

    crypto.pbkdf2(secret, appPbkdf2Salt, iterations, keyByteLength, hashname, function (err, bytes) {
      if (err) {
        throw err;
      }

      console.log('bytes', bytes.toString('hex'));
    });