@polkadot/extension

A very simple scaffolding browser extension that injects a @polkadot/api Signer into a page, along with any associated accounts, allowing for use by any dapp. This is an extensible POC implementation of a Polkadot/Substrate browser signer.

As it stands, it does one thing: it only manages accounts and allows the signing of transactions with those accounts. It does not inject providers for use by dapps at this early point, nor does it perform wallet functions where it constructs and submits txs to the network.

Running

Currently is not packaged since it is under heavy development. As such you need to build it yourself. To use -

1. Build via yarn build or yarn watch
2. Add the extension under chrome://extensions/

• ensure you have the Development flag set
• "Load unpacked" and point to packages/extension/build
• if developing, after making changes - refresh the extension

3. When visiting http://localhost:3000 or https://polkadot.js.org/apps/ it will inject the extension (the manifest currently only lists these 2 endpoints)

Once added, you can create an account (via a generated seed) or import via an existing seed. The UI, when loaded, will show these accounts as <account name> (extension)

Development

The repo is split into a number of packages -

• extension - All the injection and background processing logic (the main entry)
• extension-ui - The UI components for the extension
• extension-dapp - A convenience wrapper to work with the injected objects, simplifying data extraction for any dapp that wishes to integrate the extension (or any extension that supports the interface)

Technical

The extension injects injectedWeb3 into the global window object, exposing the following:

window.injectedWeb3 = {
  // this is the name for this extension, there could be multiples injected,
  // each with their own keys
  'polkadot-js': {
    // semver for the package
    version: '0.1.0',

    // this is called to enable the injection, and returns an injected
    // object containing the accounts, signer and provider interfaces
    // (or it will reject if not authorized)
    enable (originName: string): Promise<Injected>
  }
}

When there is more than one extension, each will populate an entry above, so from an extension implementation perspective, the structure should not be overridded. The Injected interface, as returned via enable, contains the following -

interface Injected {
  readonly accounts: Accounts;
  readonly signer: Signer;
  // not injected as of yet, subscriptable provider for polkadot-js injection
  // readonly provider: Provider
}

interface Account = {
  readonly address: string; // ss-58 encoded address
  readonly name?: string; // optional name for display
};

// exposes accounts
interface Accounts {
  // retrieves the list of accounts for right now
  get (): Promise<Array<Account>>;
  // subscribe to all accounts, updating as they change
  subscribe (cb: (accounts: Array<Account>) => any): () => void
}

// a signer that communicates with the extension via sendMessage
interface Signer extends SignerInterface {
  // no specific signer extensions, exposes the `sign` interface for use by
  // the polkadot-js API
}

The app can use all or any of these, depending on needs. To instantiate the @polkadot/api signer (allowing the extension to sign messages) can be done via (assuming a known, single extension) -

import { ApiPromise } from '@polkadot/api';

const pjsx = await window.injectedWeb3['polkadot-js'].enable('my dapp');
const accounts = await pjsx.accounts.get();
const api = await Api.create({ signer: pjsx.signer });

Generally, you would probably want to have access to all extensions available and have a slighly higher-level interface to work with. For these cases, extension-dapp provides a cleaner interface around the injected object, making it simpler to work with from a dapp perspective.