@metamask/keyring-api

MetaMask Keyring API

This TypeScript module simplifies the integration of Snaps with MetaMask using the Keyring API.

Features:

• Keyring API Interface: The module exposes an interface representing the Keyring API. Snaps can implement this interface to seamlessly interact with MetaMask and leverage its functionality.

• Dapp Client: The module includes a client that enables dapps to communicate with the account Snap. This client allows dapps to send requests to the Snap, such as retrieving account information or submitting requests.

• MetaMask Client: The module provides a client specifically designed for MetaMask integration. This client enables MetaMask to send requests directly to the account Snap, facilitating smooth interoperability between the two applications.

• Request Handler Helper Functions: The module offers a set of helper functions to simplify the implementation of the request handler in the account Snap. These functions assist in processing incoming requests, validating data, and handling various request types from dapps and MetaMask.

Installation

yarn add @metamask/keyring-api

or

npm install @metamask/keyring-api

Account Snaps

:point_up: Important: Before implementing your Snap, please make sure to read the security recommendations and the architecture document.

Starting with MetaMask 11.4, Snaps can implement the Keyring API. This allows users to manage their accounts in a more flexible way, and enables developers to build new types of accounts.

:pencil2: Note: You can also build MetaMask from source from the develop branch.

Follow these steps to implement the Keyring API in your Snap. Please note that these instruction assume that you are already familiar with the process of developing a Snap.

• Implement the Keyring API:

  Inside your Snap, implement the Keyring API:

  class MySnapKeyring implements Keyring {
    // Implement the required methods here...
  }
  

  :point_up: Important: Ensure that your keyring implements the methods called by MetaMask, otherwise some features may not work.

• Handle requests submitted by MetaMask:

  MetaMask will submit requests through the submitRequest method of your the Keyring API (check the supported EVM methods). Here is an example of request:

  {
    "id": "d6e23af6-4bea-48dd-aeb0-7d3c30ea67f9",
    "scope": "",
    "account": "69438371-bef3-4957-9f91-c3f22c1d75f3",
    "request": {
      "method": "personal_sign",
      "params": [
        "0x4578616d706c652060706572736f6e616c5f7369676e60206d657373616765",
        "0x5874174dcf1ab6F7Efd8496f4f09404CD1c5bA84"
      ]
    }
  }
  

  Where:

  • id is unique identifier for the request.

  • scope is the CAIP-2 chain ID of the selected chain. Currently, this property is always an empty string. Your Snap should use the chain ID present in the request object instead.

  • account is the ID of the account that should handle the request.

  • request is the request object.

  Your Snap must respond with either a synchronous result:

  return { pending: false, result };
  

  Or an asynchronous result:

  return { pending: true, redirect: { message, url } };
  

  The redirect message and URL will be displayed to the user to inform them about how to continue the transaction flow.

• Notify MetaMask about events:

  The following actions must be notified to MetaMask:

  • When an account is created:

    try {
      emitSnapKeyringEvent(snap, KeyringEvent.AccountCreated, { account });
      // Update your snap's state...
    } catch (error) {
      // Handle the error...
    }
    

    MetaMask will return an error if the account already exists or if the account object is invalid.

  • When an account is updated:

    try {
      emitSnapKeyringEvent(snap, KeyringEvent.AccountUpdated, { account });
      // Update your snap's state...
    } catch (error) {
      // Handle the error...
    }
    

    MetaMask will return an error if the account does not exist, if the account object is invalid, or if the account address changed.

  • When an account is deleted:

    try {
      emitSnapKeyringEvent(snap, KeyringEvent.AccountDeleted, {
        id: account.id,
      });
      // Update your snap's state...
    } catch (error) {
      // Handle the error...
    }
    

    The delete event is idempotent, so it is safe to emit it even if the account does not exist.

  • When a request is approved:

    try {
      emitSnapKeyringEvent(snap, KeyringEvent.RequestApproved, {
        id: request.id,
        result,
      });
      // Update your snap's state...
    } catch (error) {
      // Handle the error...
    }
    

    MetaMask will return an error if the request does not exist.

    :pencil2: Note: This only applies to Snaps that implement the asynchronous transaction flow.

  • When a request is rejected:

    try {
      emitSnapKeyringEvent(snap, KeyringEvent.RequestRejected, {
        id: request.id,
      });
      // Update your snap's state...
    } catch (error) {
      // Handle the error...
    }
    

    MetaMask will return an error if the request does not exist.

    :pencil2: Note: This only applies to Snaps that implement the asynchronous transaction flow.

• Expose the Keyring API:

  Then create a handler to expose the keyring methods to MetaMask and your dapp:

  export const onKeyringRequest: OnKeyringRequestHandler = async ({
    origin,
    request,
  }) => {
    // Your custom logic here...
    return handleKeyringRequest(keyring, request);
  };
  

• Call the keyring methods from your dapp:

  Now you should be able to call your account Snap from your dapp, for example:

  const client = new KeyringSnapRpcClient(snapId, window.ethereum);
  const accounts = await client.listAccounts();
  

KeyringV2 Interface (WIP, not implemented yet)

A unified keyring interface, designed to work for both native (EVM) keyrings and Snap keyrings, and to support non‑EVM chains and new features like backup & sync.

• Interface name: KeyringV2
• Location: @metamask/keyring-api/src/api/v2/keyring.ts

Keyring wrapper

The KeyringWrapper helper adapts existing keyrings that implement the legacy Keyring interface to the new KeyringV2 interface. It is intended to be subclassed in concrete keyrings, overriding the account management and request-handling methods to delegate to the underlying implementation.

Migrating from 0.1.x to 0.2.x

The following changes were made to the API, which may require changes to your implementation:

• In the KeyringAccount type, the supportedMethods property was renamed to methods.

  - supportedMethods: string[];
  + methods: string[];
  

• In the KeyringAccount type, the name property was removed.

  - name: string;
  

• In the KeyringAccount type, add the options property can no longer be null.

  - options: Record<string, unknown> | null;
  + options: Record<string, unknown>;
  

• In the KeyringAccount type, the eth_signTypedData method was removed from the list of available methods.

  - 'eth_signTypedData',
  

  It was an alias for the eth_signTypedData_v1 method, which is still present.

• Snaps should now use the emitSnapKeyringEvent() helper function to notify MetaMask about events:

  // Emit an event to indicate that an account was created.
  emitSnapKeyringEvent(snap, KeyringEvent.AccountCreated, { account });
  
  // Emit an event to indicate that an account was updated.
  emitSnapKeyringEvent(snap, KeyringEvent.AccountUpdated, { account });
  
  // Emit an event to indicate that an account was deleted.
  emitSnapKeyringEvent(snap, KeyringEvent.AccountDeleted, { id: account.id });
  
  // Emit an event to indicate that a request was approved.
  emitSnapKeyringEvent(snap, KeyringEvent.RequestApproved, {
    id: request.id,
    result,
  });
  
  // Emit an event to indicate that a request was rejected.
  emitSnapKeyringEvent(snap, KeyringEvent.RequestRejected, { id: request.id });
  

  :point_up: Important: For all events above, MetaMask may return an error indicating that the event was not handled, possibly because it contains invalid arguments.

• Keyrings that implement the asynchronous transaction flow can now return an optional redirect property that contains an URL and a message to be displayed to the user. This will, in a future release of MetaMask, be used to inform the user on how to continue the transaction flow.

  return {
    pending: true,
    redirect: {
      message: 'Please go to the Snap Dapp to finish sining the transaction.',
      url: 'https://example.com/sign?tx=1234',
    },
  };
  

• The buildHandlersChain helper function was removed from the API. Instead, you must implement your own handler. For example:

  export const onRpcRequest: OnRpcRequestHandler = async ({
    request,
    origin,
  }) => {
    // Check if origin is allowed to call the method.
    if (!hasPermission(origin, request.method)) {
      throw new Error(
        `Origin '${origin}' is not allowed to call '${request.method}'`,
      );
    }
  
    // Dispatch the request to the keyring.
    return handleKeyringRequest(keyring, request);
  };
  

Migrating from 0.2.x to 1.x.x

The following changes were made to the API, which may require changes to your implementation:

• Your Snap must expose the Keyring methods through the onKeyringRequest export instead of the onRpcRequest export.

• Your Snap must request the new endowment:keyring endowment, and list any dapp that should be allowed to call the Keyring methods.

For more details about the changes, please refer to the security guidelines.

API

See our documentation:

• Latest published API documentation
• Latest development API documentation

Contributing

Setup

• Install Node.js version 16
  • If you are using nvm (recommended) running nvm use will automatically choose the right node version for you.
• Install Yarn v3
• Run yarn install to install dependencies and run any required post-install scripts

Testing and Linting

Run yarn test to run the tests once. To run tests on file changes, run yarn test:watch.

Run yarn lint to run the linter, or run yarn lint:fix to run the linter and fix any automatically fixable issues.

Release & Publishing

The project follows the same release process as the other libraries in the MetaMask organization. The GitHub Actions action-create-release-pr and action-publish-release are used to automate the release process; see those repositories for more information about how they work.

• Choose a release version.

  • The release version should be chosen according to SemVer. Analyze the changes to see whether they include any breaking changes, new features, or deprecations, then choose the appropriate SemVer version. See the SemVer specification for more information.

• If this release is backporting changes onto a previous release, then ensure there is a major version branch for that version (e.g. 1.x for a v1 backport release).

  • The major version branch should be set to the most recent release with that major version. For example, when backporting a v1.0.2 release, you'd want to ensure there was a 1.x branch that was set to the v1.0.1 tag.

• Trigger the workflow_dispatch event manually for the Create Release Pull Request action to create the release PR.

  • For a backport release, the base branch should be the major version branch that you ensured existed in step 2. For a normal release, the base branch should be the main branch for that repository (which should be the default value).
  • This should trigger the action-create-release-pr workflow to create the release PR.

• Update the changelog to move each change entry into the appropriate change category (See here for the full list of change categories, and the correct ordering), and edit them to be more easily understood by users of the package.

  • Generally any changes that don't affect consumers of the package (e.g. lockfile changes or development environment changes) are omitted. Exceptions may be made for changes that might be of interest despite not having an effect upon the published package (e.g. major test improvements, security improvements, improved documentation, etc.).
  • Try to explain each change in terms that users of the package would understand (e.g. avoid referencing internal variables/concepts).
  • Consolidate related changes into one change entry if it makes it easier to explain.
  • Run yarn auto-changelog validate --prettier --rc to check that the changelog is correctly formatted.

• Review and QA the release.

  • If changes are made to the base branch, the release branch will need to be updated with these changes and review/QA will need to restart again. As such, it's probably best to avoid merging other PRs into the base branch while review is underway.

• Squash & Merge the release.

  • This should trigger the action-publish-release workflow to tag the final release commit and publish the release on GitHub.

• Publish the release on npm.

  • Wait for the publish-release GitHub Action workflow to finish. This should trigger a second job (publish-npm), which will wait for a run approval by the npm publishers team.
  • Approve the publish-npm job (or ask somebody on the npm publishers team to approve it for you).
  • Once the publish-npm job has finished, check npm to verify that it has been published.