Signature.js

/**
 * Copyright 2018 The AMP HTML Authors. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS-IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

'use strict';

const jsrsasign = require('jsrsasign');

/**
 * A wrapper of the `jsrsasign`, to provide signing for content using the
 * `SHA256withRSA` algorithm.
 */
class Signature {
  constructor(privateKey) {
    this._privateKey = privateKey;
    this._sig = new jsrsasign.Signature({alg: 'SHA256withRSA'});
    this._sig.init(this._privateKey);
  }

  /**
   * Generates a signature for the content
   * @param {string} data the signed content, using base64 url encoding.
   */
  generate(data) {
    const signed = this._sig.signString(data);
    return jsrsasign.hextob64u(signed);
  }
}

module.exports = Signature;