packages/server/src/helpers/decodeAuthenticatorExtensions.ts


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import cbor from 'cbor';

/**
 * Convert authenticator extension data buffer to a proper object
 *
 * @param extensionData Authenticator Extension Data buffer
 */
export function decodeAuthenticatorExtensions(
  extensionData: Buffer
): AuthenticationExtensionsAuthenticatorOutputs | undefined {
  let toCBOR: AuthenticationExtensionsAuthenticatorOutputs | undefined;
  try {
    toCBOR = cbor.decodeAllSync(extensionData)[0];
  } catch (err) {
    const _err = err as Error;
    throw new Error(`Error decoding authenticator extensions: ${_err.message}`);
  }
  return toCBOR;
}

export type AuthenticationExtensionsAuthenticatorOutputs = {
  devicePublicKey?: DevicePublicKeyAuthenticatorOutput;
  uvm?: UVMAuthenticatorOutput;
}

export type DevicePublicKeyAuthenticatorOutput = {
  dpk?: Buffer;
  scp?: Buffer;
  sig?: string;
  aaguid?: Buffer;
}

// TODO: Need to verify this format
// https://w3c.github.io/webauthn/#sctn-uvm-extension.
export type UVMAuthenticatorOutput = {
  uvm?: Buffer[]
}