wbn-sign

Signing with Integrity Block

This is a Node.js module for signing Web Bundles with integrityblock.

The module takes an existing bundle file and an ed25519 private key, and emits a new bundle file with cryptographic signature added to the integrity block.

Installation

Using npm:

npm install wbn-sign

Requirements

This plugin requires Node v14.0.0+.

Usage

Please be aware that the APIs are not stable yet and are subject to change at any time.

Signing a web bundle file:

import * as fs from 'fs';
import * as wbnSign from 'wbn-sign';

// Read an existing web bundle file or generate using "wbn" npm package.
const webBundle = fs.readFileSync('./path/to/webbundle.wbn');

const privateKey = wbnSign.parsePemKey(
  fs.readFileSync('./path/to/privatekey.pem', 'utf-8')
);

// Option 1: With the default (`NodeCryptoSigningStrategy`) signing strategy.
const { signedWebBundle } = await new wbnSign.IntegrityBlockSigner(webBundle, {
  key: privateKey,
}).sign();

// Option 2: With specified signing strategy.
const { signedWebBundle } = await new wbnSign.IntegrityBlockSigner(
  webBundle,
  new wbnSign.NodeCryptoSigningStrategy(privateKey)
).sign();

// Option 3: With ones own CustomSigningStrategy class implementing
// ISigningStrategy.
const { signedWebBundle } = await new wbnSign.IntegrityBlockSigner(
  webBundle,
  new (class {
    async sign(data: Uint8Array): Promise<Uint8Array> {
      // E.g. connect to one's external signing service that signs the payload.
    }
    async getPublicKey(): Promise<KeyObject> {
      /** E.g. connect to one's external signing service that returns the public
       * key.*/
    }
  })()
).sign();

fs.writeFileSync(signedWebBundle);

This library also exposes a helper class to calculate the Web Bundle's ID (or App ID) from the private or public ed25519 key, which can then be used when bundling Isolated Web Apps.

Calculating the web bundle ID for Isolated Web Apps:

import * as fs from 'fs';
import * as wbnSign from 'wbn-sign';

const privateKey = wbnSign.parsePemKey(
  fs.readFileSync('./path/to/privatekey.pem', 'utf-8')
);

// Web Bundle ID only:
const webBundleId = new wbnSign.WebBundleId(privateKey).serialize();

// With origin, meaning "isolated-app://" combined with Web Bundle ID:
const webBundleIdWithIWAOrigin = new wbnSign.WebBundleId(
  privateKey
).serializeWithIsolatedWebAppOrigin();

CLI

This package also includes 2 CLI tools

• wbn-sign which lets you sign a web bundle easily without having to write any additional JavaScript.
• wbn-dump-id which can be used to calculate the Web Bundle ID corresponding to your signing key.

Running wbn-sign

There are the following command-line flags available:

• (required) --privateKey <filePath> (-k <filePath>)
  which takes the path to ed25519 private key.
• (required) --input <filePath> (-i <filePath>)
  which takes the path to the web bundle to be signed.
• (optional) --output <filePath> (-o <filePath>)
  which takes the path to the wanted signed web bundle output. Default: signed.swbn.

Example command:

wbn-sign \
-i ~/path/to/webbundle.wbn \
-o ~/path/to/signed-webbundle.swbn \
-k ~/path/to/ed25519key.pem

Running wbn-dump-id

There are the following command-line flags available:

• (required) --privateKey <filePath> (-k <filePath>)
  which takes the path to ed25519 private key.
• (optional) --withIwaScheme <boolean> (-s)
  which dumps the Web Bundle ID with isolated-app:// scheme. By default it only dumps the ID. Default: false.

Example command:

wbn-sign -s -k ~/path/to/ed25519key.pem

This would print the Web Bundle ID calculated from ed25519key.pem into the console with the isolated-app:// scheme.

If one wants to save the ID into a file or into an environment variable, one can do the following (respectively):

wbn-dump-id -k file_enc.pem -s > webbundleid.txt

export DUMP_WEB_BUNDLE_ID="$(wbn-dump-id -k file_enc.pem -s)"

The environment variable set like this, can then be used in other scripts, for example in --baseURL when creating a web bundle with wbn CLI tool.

Generating Ed25519 key

An unencrypted ed25519 private key can be generated with:

openssl genpkey -algorithm Ed25519 -out ed25519key.pem

For better security, one should prefer using passphrase-encrypted ed25519 private keys. To encrypt an unencrypted private key, run:

# encrypt the key (will ask for a passphrase, make sure to use a strong one)
openssl pkcs8 -in ed25519key.pem -topk8 -out encrypted_ed25519key.pem
# delete the unencrypted key
rm ed25519key.pem

If you use an encrypted private key, you will be prompted for its passphrase as part of the signing process. If you want to use the CLI tool programmatically, then you can bypass the passphrase prompt by storing the passphrase in an environment variable named WEB_BUNDLE_SIGNING_PASSPHRASE.

Release Notes

v0.1.2

• Add support for calculating the Web Bundle ID with the CLI tool.

v0.1.1

• Add support for bypassing the passphrase prompt for encrypted private keys by reading the passphrase from the WEB_BUNDLE_SIGNING_PASSPHRASE environment variable if it is set when using the CLI tool directly.

v0.1.0

• BREAKING CHANGE: Introducing the support for using different types of signing strategies. Will enable users to initialize a SigningStrategy class (implementing the newly introduced ISigningStrategy interface). Also sign changes to be an async function.
• Add support for using passphrase-encrypted Ed25519 private keys.

v0.0.1

• Support for signing web bundles with integrity block added.