webauthn-p256 v0.0.10

Table of Contents

• Install
• Usage
• Core Reference
  • createCredential
  • sign
  • verify
• Utilities Reference
  • getCredentialCreationOptions
  • getCredentialSignRequestOptions
  • parsePublicKey
  • parseSignature
  • serializePublicKey
  • serializeSignature
• Authors
• License

Install

npm i webauthn-p256

pnpm i webauthn-p256

bun i webauthn-p256

Usage

import { createCredential, sign, verify } from 'webauthn-p256'

// Register a WebAuthn credential (ie. passkey).
const credential = createCredential({
  name: 'Example',
})

// Sign hash with credential.
const { signature, webauthn } = await sign({
  credentialId: credential.id,
  hash: '0x...'
})

// Verify signature with hash, public key, and WebAuthn data.
const verified = await verify({
  hash: '0x...',
  publicKey: credential.publicKey,
  signature,
  webauthn,
})

Onchain Verification

We can also verify WebAuthn signatures onchain via contracts that expose a WebAuthn verifier interface.

The example below uses Viem to call the verify function on the WebAuthn.sol contract. However, in a real world scenario, a contract implementing the WebAuthn verifier interface will call the verify function (e.g. a isValidSignature interface on an ERC-4337 Smart Wallet).

Note: Bytecode for the code variable can be obtained here.

import { createCredential, parsePublicKey, parseSignature, sign } from 'webauthn-p256'
import { createPublicClient, http } from 'viem'
import { mainnet } from 'viem/chains'

const abi = parseAbi([
  'struct WebAuthnAuth { bytes authenticatorData; string clientDataJSON; uint256 challengeIndex; uint256 typeIndex; uint256 r; uint256 s; }',
  'function verify(bytes, bool, WebAuthnAuth, uint256, uint256)'
])
const code = '0x...'

const credential = createCredential({
  name: 'Example',
})

const hash = '0x...'

const { signature, webauthn } = await sign({
  credentialId: credential.id,
  hash
})

const { x, y } = parsePublicKey(credential.publicKey)
const { r, s } = parseSignature(signature)

const verified = await client.readContract({
  abi,
  code,
  functionName: 'verify',
  args: [
    hash,
    webauthn.userVerificationRequired,
    { ...webauthn, r, s },
    x,
    y,
  ],
})

Core Reference

createCredential

Creates a P256 WebAuthn credential with a Passkey authenticator.

Usage

import { createCredential } from 'webauthn-p256'

const credential = createCredential({
  name: 'Example',
})

API

sign

Signs a hash using a stored credential. If no credential is provided, a prompt will be displayed for the user to select an existing credential that was previously registered.

Usage

import { sign } from 'webauthn-p256'

const credential = { /* ... */ }

const { signature, webauthn } = await sign({
  credentialId: credential.id,
  hash: '0x...',
})

API

verify

Verifies a signature using the credential public key and the hash which was signed.

!WARNING The verify implementation mimics Daimo's audited WebAuthn.sol – however, this TypeScript implementation is unaudited.

Usage

import { verify } from 'webauthn-p256'

const credential = { /* ... */ }
const signature = '0x...'
const webauthn = { /* ... */ }
 
const valid = await verify({ 
  hash: '0x...', 
  publicKey: credential.publicKey, 
  signature,
  webauthn,
})

API

Utilities Reference

getCredentialCreationOptions

Returns the credential creation options for a P256-flavoured WebAuthn credential.

Usage

import { getCredentialCreationOptions } from 'webauthn-p256'

const options = getCredentialCreationOptions({
  name: 'Example',
})

API

getCredentialSignRequestOptions

Returns the credential sign request options for a P256-flavoured WebAuthn credential.

Usage

import { getCredentialSignRequestOptions } from 'webauthn-p256'

const options = getCredentialSignRequestOptions({
  credentialId: '...',
  hash: '0x...',
})

API

parsePublicKey

Parses a serialized public key into x and y coordinates.

Usage

import { parsePublicKey } from 'webauthn-p256'

const publicKey = parsePublicKey('0x...')

console.log(publicKey)
// { x: 1231..., y: 12412... }

API

parseSignature

Parses a serialized signature into r and s coordinates.

Usage

import { parseSignature } from 'webauthn-p256'

const signature = parseSignature('0x...')

console.log(signature)
// { r: 1231..., s: 12412... }

API

serializePublicKey

Serializes a public key into a hex string or bytes.

Usage

import { serializePublicKey } from 'webauthn-p256'

const publicKey = serializePublicKey({
  x: 12341...,
  y: 12341...,
})

console.log(publicKey)
// '0x...'

API

serializeSignature

Serializes a signature into a hex string or bytes.

Usage

import { serializeSignature } from 'webauthn-p256'

const signature = serializeSignature({
  r: 12341...,
  s: 12341...,
})

console.log(signature)
// '0x...'

API

Authors

• @jxom (jxom.eth, X)

License

MIT License