MetaMask Message Signing Snap

This Snap allows certain messages to be signed & verified through a randomly generated private key.

Installation

yarn add @metamask/message-signing-snap

or

npm install @metamask/message-signing-snap

Usage

See the RPC API for more information on how to interact with the snap.

Example usa of the signing API

// Example: Get Signing Public Key
const publicKey: string = await ethereum.request({
  method: 'wallet_invokeSnap',
  params: {
    // or local:http://localhost:8080 if running snap locally
    snapId: 'npm:@metamask/message-signing-snap',
    request: {
      method: 'getPublicKey',
      params: {
        entropySourceId: '...', // optionally choose a specific SRP
      },
    },
  },
});

// Example: Sign a message
const signature: string = await ethereum.request({
  method: 'wallet_invokeSnap',
  params: {
    // or local:http://localhost:8080 if running snap locally
    snapId: 'npm:@metamask/message-signing-snap',
    request: {
      method: 'signMessage',
      params: {
        message: 'metamask:my message to sign',
        entropySourceId: '...', // optionally choose a specific SRP
      },
    },
  },
});

The signature can be verified against the publicKey.

Example usage of the encryption capabilities

Alice, the user of this functionality, would call the getPublicEncryptionKey method and obtain a hex encoded X25519 public key, which they would broadcast to Bob.

const encryptionPublicKeyHex: string = await ethereum.request({
  method: 'wallet_invokeSnap',
  params: {
    snapId: 'npm:@metamask/message-signing-snap',
    request: {
      method: 'getEncryptionPublicKey',
      params: {
        entropySourceId: '...', // optionally choose a specific SRP
      },
    },
  },
});

Bob would then use a piece of code similar to:

import { encrypt } from '@metamask/eth-sig-util';

const encrypted = encrypt({
  encryptionPublicKeyHex,
  data: 'Hello Alice!',
  version: 'x25519-xsalsa20-poly1305',
});

... and obtain an object such as:

// encrypted data from Bob
{
  version: 'x25519-xsalsa20-poly1305',
  nonce: '8jFlr2cYdkyBIookw6akE8lA0f+odanN',
  ephemPublicKey: 'UOPWFRaPdY6kKDEoM/ovCBCT2p4PSx6MMdOgNzA2gC0=',
  ciphertext: '2UNvHmxnmOHtI9vhf7gfeD/J7Q/q6vqjEQqY',
}

Bob would send this object to Alice who can then call the decryptMessage method of the snap to get the message.

const decryptedMessage: string = await window.ethereum.request({
  method: 'wallet_invokeSnap',
  params: {
    snapId: 'npm:@metamask/message-signing-snap',
    request: {
      method: 'decryptMessage',
      params: {
        data: {
          version: 'x25519-xsalsa20-poly1305',
          nonce: '8jFlr2cYdkyBIookw6akE8lA0f+odanN',
          ephemPublicKey: 'UOPWFRaPdY6kKDEoM/ovCBCT2p4PSx6MMdOgNzA2gC0=',
          ciphertext: '2UNvHmxnmOHtI9vhf7gfeD/J7Q/q6vqjEQqY',
        },
        entropySourceId: '...', // optionally choose a specific SRP
      },
    },
  },
});

Sometimes Alice may not be able to know which SRP she should use to decrypt the message. In that situation the snap will try all available SRPs for the decryption.

API

See our documentation:

• RPC API for more information on how to interact with the snap.

Testing

See our documentation

• Testing Docs on how to call this pre-installed snap.

Contributing

Setup

• Install the current LTS version of Node.js
  • If you are using nvm (recommended) running nvm install will install the latest version and 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.

1. 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.

2. 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.

3. 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.

4. 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 --rc to check that the changelog is correctly formatted.

5. 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.

6. Squash & Merge the release.

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

7. 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.