Add base Signer and ExternalSigner implementations using PKI.js

Author: dcbr

packages/signer-p12/dist/P12Signer.d.ts

@@ -3,7 +3,7 @@
  * @prop {string} [passphrase]
  * @prop {boolean} [asn1StrictParsing]
  */
-export class P12Signer extends Signer {
+export class P12Signer extends ISigner {
     /**
      * @param {Buffer | Uint8Array | string} p12Buffer
      * @param {SignerOptions} additionalOptions
@@ -19,5 +19,5 @@ export type SignerOptions = {
     passphrase?: string;
     asn1StrictParsing?: boolean;
 };
-import { Signer } from '@signpdf/utils';
+import { ISigner } from '@signpdf/utils';
 //# sourceMappingURL=P12Signer.d.ts.map

packages/signer-p12/dist/P12Signer.d.ts.map

@@ -13,7 +13,7 @@ function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { de
  * @prop {boolean} [asn1StrictParsing]
  */
 
-class P12Signer extends _utils.Signer {
+class P12Signer extends _utils.ISigner {
   /**
    * @param {Buffer | Uint8Array | string} p12Buffer
    * @param {SignerOptions} additionalOptions

packages/signer-p12/dist/P12Signer.js

@@ -1,13 +1,13 @@
 import forge from 'node-forge';
-import {convertBuffer, SignPdfError, Signer} from '@signpdf/utils';
+import {convertBuffer, SignPdfError, ISigner} from '@signpdf/utils';
 
 /**
  * @typedef {object} SignerOptions
  * @prop {string} [passphrase]
  * @prop {boolean} [asn1StrictParsing]
  */
 
-export class P12Signer extends Signer {
+export class P12Signer extends ISigner {
     /**
      * @param {Buffer | Uint8Array | string} p12Buffer
      * @param {SignerOptions} additionalOptions

packages/signer-p12/src/P12Signer.js

@@ -0,0 +1,3 @@
+{
+    "extends": "../../babel.config.json"
+}

packages/signer/.babelrc

@@ -0,0 +1,5 @@
+{
+    "extends": [
+      "@signpdf/eslint-config"
+    ]    
+}

packages/signer/.eslintrc

@@ -0,0 +1,17 @@
+# Signer base implementation with PKI.js
+
+for [![@signpdf](https://raw.githubusercontent.com/vbuch/node-signpdf/master/resources/logo-horizontal.svg?sanitize=true)](https://github.com/vbuch/node-signpdf/)
+
+[![npm version](https://badge.fury.io/js/@signpdf%2Fsigner.svg)](https://badge.fury.io/js/@signpdf%2Fsigner)
+[![Donate to this project using Buy Me A Coffee](https://img.shields.io/badge/buy%20me%20a%20coffee-donate-yellow.svg)](https://buymeacoffee.com/vbuch)
+
+Uses `PKI.js` to create a detached signature of a given `Buffer`.
+
+## Usage
+
+This is an abstract base implementation of the `Signer` and `ExternalSigner` classes. Use any of the available implementations (or subclass any of these classes yourself) to sign an actual PDF file. See for example the [P12Signer package](/packages/signer-p12) for signing with a PKCS#12 certificate bundle.
+
+## Notes
+
+* Make sure to have a look at the docs of the [@signpdf family of packages](https://github.com/vbuch/node-signpdf/).
+* Feel free to copy and paste any part of this code. See its defined [Purpose](https://github.com/vbuch/node-signpdf#purpose).

packages/signer/README.md

@@ -0,0 +1,23 @@
+/**
+ * Abstract ExternalSigner class taking care of creating a suitable signature for a given pdf
+ * using an external signature provider.
+ * Subclasses should specify the required signature and hashing algorithms used by the external
+ * provider (either through the `signAlgorithm` and `hashAlgorithm` attributes, or by overriding
+ * the `getSignAlgorithm` and `getHashAlgorithm` methods), as well as provide the used signing
+ * certificate and final signature (by implementing the `getCertificate` and `getSignature`
+ * methods).
+ */
+export class ExternalSigner extends Signer {
+    /**
+     * Method to retrieve the signature of the given hash (of the given data) from the external
+     * service. The original data is included in case the external signature provider computes
+     * the hash automatically before signing.
+     * To be implemented by subclasses.
+     * @param {Uint8Array} hash
+     * @param {Uint8Array} data
+     * @returns {Promise<Uint8Array>}
+     */
+    getSignature(hash: Uint8Array, data: Uint8Array): Promise<Uint8Array>;
+}
+import { Signer } from './Signer';
+//# sourceMappingURL=ExternalSigner.d.ts.map

packages/signer/dist/ExternalSigner.d.ts

@@ -0,0 +1,76 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.ExternalSigner = void 0;
+var pkijs = _interopRequireWildcard(require("pkijs"));
+var _utils = require("@signpdf/utils");
+var _Signer = require("./Signer");
+function _getRequireWildcardCache(nodeInterop) { if (typeof WeakMap !== "function") return null; var cacheBabelInterop = new WeakMap(); var cacheNodeInterop = new WeakMap(); return (_getRequireWildcardCache = function (nodeInterop) { return nodeInterop ? cacheNodeInterop : cacheBabelInterop; })(nodeInterop); }
+function _interopRequireWildcard(obj, nodeInterop) { if (!nodeInterop && obj && obj.__esModule) { return obj; } if (obj === null || typeof obj !== "object" && typeof obj !== "function") { return { default: obj }; } var cache = _getRequireWildcardCache(nodeInterop); if (cache && cache.has(obj)) { return cache.get(obj); } var newObj = {}; var hasPropertyDescriptor = Object.defineProperty && Object.getOwnPropertyDescriptor; for (var key in obj) { if (key !== "default" && Object.prototype.hasOwnProperty.call(obj, key)) { var desc = hasPropertyDescriptor ? Object.getOwnPropertyDescriptor(obj, key) : null; if (desc && (desc.get || desc.set)) { Object.defineProperty(newObj, key, desc); } else { newObj[key] = obj[key]; } } } newObj.default = obj; if (cache) { cache.set(obj, newObj); } return newObj; }
+/* eslint-disable no-unused-vars */
+
+/**
+ * Abstract ExternalSigner class taking care of creating a suitable signature for a given pdf
+ * using an external signature provider.
+ * Subclasses should specify the required signature and hashing algorithms used by the external
+ * provider (either through the `signAlgorithm` and `hashAlgorithm` attributes, or by overriding
+ * the `getSignAlgorithm` and `getHashAlgorithm` methods), as well as provide the used signing
+ * certificate and final signature (by implementing the `getCertificate` and `getSignature`
+ * methods).
+ */
+class ExternalSigner extends _Signer.Signer {
+  /**
+   * Method to retrieve the signature of the given hash (of the given data) from the external
+   * service. The original data is included in case the external signature provider computes
+   * the hash automatically before signing.
+   * To be implemented by subclasses.
+   * @param {Uint8Array} hash
+   * @param {Uint8Array} data
+   * @returns {Promise<Uint8Array>}
+   */
+  async getSignature(hash, data) {
+    throw new _utils.SignPdfError(`getSignature() is not implemented on ${this.constructor.name}`, _utils.SignPdfError.TYPE_INPUT);
+  }
+
+  /**
+   * Get a "crypto" extension and override the function used by SignedData.sign to support
+   * external signing.
+   * @returns {pkijs.ICryptoEngine}
+   */
+  getCrypto() {
+    const crypto = super.getCrypto();
+    crypto.sign = async (_algo, _key, data) => {
+      // Calculate hash
+      const hash = await crypto.digest({
+        name: this.hashAlgorithm
+      }, data);
+      // And pass it to the external signature provider
+      const signature = await this.getSignature(Buffer.from(hash), Buffer.from(data));
+      return signature;
+    };
+    return crypto;
+  }
+
+  /**
+   * Obtain a dummy private key to pass the correct signing parameters to the sign function.
+   * @returns {CryptoKey}
+   */
+  async obtainKey() {
+    // The algorithm parameters cannot be passed directly to the SignedData.sign function, so we
+    // need to generate a dummy private key with the required parameters and pass that to the
+    // sign function. The private key is not actually used for signing, as we override the
+    // crypto.sign function in the getCrypto method.
+    const algorithmParams = this.crypto.getAlgorithmParameters(this.signAlgorithm, 'generatekey').algorithm;
+    const keypair = await this.crypto.generateKey({
+      name: this.signAlgorithm,
+      ...algorithmParams,
+      hash: {
+        name: this.hashAlgorithm
+      }
+    }, false, ['sign', 'verify']);
+    return keypair.privateKey;
+  }
+}
+exports.ExternalSigner = ExternalSigner;