crowd-funder-for-time-pwa/src/libs/didPeer.ts

import asn1 from "asn1-ber";
import { Buffer } from "buffer/";
import { decode as cborDecode } from "cbor-x";
import { createJWS, JWTPayload, verifyJWT } from "did-jwt";
import { DIDResolutionResult, Resolver } from "did-resolver";
import { bytesToMultibase } from "@veramo/utils";
import { startAuthentication } from "@simplewebauthn/browser";
import {
  generateAuthenticationOptions,
  verifyAuthenticationResponse,
  verifyRegistrationResponse,
  VerifyRegistrationResponseOpts,
} from "@simplewebauthn/server";
import { VerifyAuthenticationResponseOpts } from "@simplewebauthn/server/esm/authentication/verifyAuthenticationResponse";
import {
  Base64URLString,
  PublicKeyCredentialRequestOptionsJSON,
} from "@simplewebauthn/types";

export interface JWK {
  kty: string;
  crv: string;
  x: string;
  y: string;
}
export interface PublicKeyCredential {
  rawId: Uint8Array;
  jwt: JWK;
}

function toBase64Url(anything: Uint8Array) {
  return Buffer.from(anything)
    .toString("base64")
    .replace(/\+/g, "-")
    .replace(/\//g, "_")
    .replace(/=+$/, "");
}

export async function registerCredential(
  userId: Uint8Array,
  challenge: Uint8Array,
) {
  const publicKeyOptions: PublicKeyCredentialCreationOptions = {
    challenge: challenge,
    rp: {
      name: "Time Safari",
      id: window.location.hostname,
    },
    user: {
      id: userId,
      name: "Current-User",
      displayName: "Current User",
    },
    pubKeyCredParams: [
      {
        type: "public-key",
        alg: -7, // ES256 algorithm
      },
    ],
    authenticatorSelection: {
      authenticatorAttachment: "platform",
      userVerification: "preferred",
    },
    timeout: 60000,
    attestation: "direct",
  };

  const credential = await navigator.credentials.create({
    publicKey: publicKeyOptions,
  });
  console.log("credential", credential);
  console.log(credential?.id, " is the new ID base64-url-encoded");
  console.log(toBase64Url(credential?.rawId), " is the base64 rawId");
  const attestationResponse = credential?.response;
  const verfInput: VerifyRegistrationResponseOpts = {
    response: {
      id: credential?.id as string,
      rawId: credential?.id as string, //Buffer.from(credential?.rawId).toString("base64"),
      response: {
        attestationObject: toBase64Url(attestationResponse?.attestationObject),
        clientDataJSON: toBase64Url(attestationResponse?.clientDataJSON),
      },
      clientExtensionResults: {},
      type: "public-key",
    },
    expectedChallenge: toBase64Url(challenge),
    expectedOrigin: window.location.origin,
  };
  console.log("verfInput", verfInput);
  const verification = await verifyRegistrationResponse(verfInput);
  console.log("verification", verification);

  // Parse the attestation response to get the public key
  const clientDataJSON = attestationResponse.clientDataJSON;
  console.log("clientDataJSON raw", clientDataJSON);
  console.log(
    "clientDataJSON dec",
    new TextDecoder("utf-8").decode(clientDataJSON),
  );
  const attestationObject = cborDecode(
    new Uint8Array(attestationResponse.attestationObject),
  );
  console.log("attestationObject", attestationObject);

  const jwkObj = cborDecode(
    verification.registrationInfo?.credentialPublicKey as Uint8Array,
  );
  console.log("jwkObj from verification", jwkObj);
  if (
    jwkObj[1] != 2 || // kty "EC"
    jwkObj[3] != -7 || // alg "ES256"
    jwkObj[-1] != 1 || // crv "P-256"
    jwkObj[-2].length != 32 || // x
    jwkObj[-3].length != 32 // y
  ) {
    throw new Error("Unable to extract key.");
  }
  const publicKeyJwk = {
    alg: "ES256",
    crv: "P-256",
    kty: "EC",
    x: toBase64Url(jwkObj[-2]),
    y: toBase64Url(jwkObj[-3]),
  };
  const publicKeyBytes = Buffer.concat([
    Buffer.from(jwkObj[-2]),
    Buffer.from(jwkObj[-3]),
  ]);

  //const publicKeyBytes = extractPublicKeyCose(attestationObject.authData);
  //const publicKeyJwk = extractPublicKeyJwk(attestationObject.authData);

  return {
    authData: attestationObject.authData,
    credId: credential?.id,
    rawId: credential?.rawId,
    publicKeyJwk,
    publicKeyBytes,
  };
}

// parse authData
// here's one: https://github.com/MasterKale/SimpleWebAuthn/blob/master/packages/server/src/helpers/parseAuthenticatorData.ts#L11
// from https://chatgpt.com/c/0ce72fda-bc5d-42ff-a748-6022f6e39fa0
// from https://chatgpt.com/share/78a5c91d-099d-46dc-aa6d-fc0c916509fa

export function createPeerDid(publicKeyBytes: Uint8Array) {
  // https://github.com/decentralized-identity/veramo/blob/next/packages/did-provider-peer/src/peer-did-provider.ts#L67
  //const provider = new PeerDIDProvider({ defaultKms: LOCAL_KMS_NAME });
  const methodSpecificId = bytesToMultibase(
    publicKeyBytes,
    "base58btc",
    "secp256k1-pub",
  );
  return "did:peer:0" + methodSpecificId;
}

export class PeerSetup {
  public authenticatorData?: ArrayBuffer;
  public clientDataJsonDecoded?: object;

  public async createJwt(
    payload: object,
    issuerDid: string,
    credentialId: string,
  ) {
    const signer = await this.webAuthnES256KSigner(credentialId);

    // from createJWT in did-jwt/src/JWT.ts
    const header: JWTPayload = { typ: "JWT", alg: "ES256K" };
    const timestamps: Partial<JWTPayload> = {
      iat: Math.floor(Date.now() / 1000),
      exp: undefined,
    };
    const fullPayload = { ...timestamps, ...payload, iss: issuerDid };

    const jwt = createJWS(fullPayload, signer, header);
    return jwt;
  }

  async webAuthnES256KSigner(credentialID: string) {
    return async (data: string | Uint8Array) => {
      const signature = await this.generateWebAuthnSignature(
        data,
        credentialID,
      );

      // This converts from the browser ArrayBuffer to a Node.js Buffer, which is a requirement for the asn1 library.
      const signatureBuffer = Buffer.from(signature);
      console.log("signature inside signer", signature);
      console.log("buffer signature inside signer", signatureBuffer);
      // Decode the DER-encoded signature to extract R and S values
      const reader = new asn1.BerReader(signatureBuffer);
      console.log("after reader");
      reader.readSequence();
      console.log("after read sequence");
      const r = reader.readString(asn1.Ber.Integer, true);
      console.log("after r");
      const s = reader.readString(asn1.Ber.Integer, true);
      console.log("after r & s");

      // Ensure R and S are 32 bytes each
      const rBuffer = Buffer.from(r);
      const sBuffer = Buffer.from(s);
      console.log("after rBuffer & sBuffer", rBuffer, sBuffer);
      const rWithoutPrefix = rBuffer.length > 32 ? rBuffer.slice(1) : rBuffer;
      const sWithoutPrefix = sBuffer.length > 32 ? sBuffer.slice(1) : sBuffer;
      const rPadded =
        rWithoutPrefix.length < 32
          ? Buffer.concat([Buffer.alloc(32 - rWithoutPrefix.length), rBuffer])
          : rWithoutPrefix;
      const sPadded =
        rWithoutPrefix.length < 32
          ? Buffer.concat([Buffer.alloc(32 - sWithoutPrefix.length), sBuffer])
          : sWithoutPrefix;

      // Concatenate R and S to form the 64-byte array (ECDSA signature format expected by JWT)
      const combinedSignature = Buffer.concat([rPadded, sPadded]);
      console.log(
        "combinedSignature",
        combinedSignature.length,
        combinedSignature,
      );

      const combSig64 = combinedSignature.toString("base64");
      console.log("combSig64", combSig64);
      const combSig64Url = combSig64
        .replace(/\+/g, "-")
        .replace(/\//g, "_")
        .replace(/=+$/, "");
      console.log("combSig64Url", combSig64Url);
      return combSig64Url;
    };
  }

  async generateWebAuthnSignature(
    dataToSign: string | Uint8Array, // from Signer interface
    credentialId: string,
  ) {
    if (dataToSign instanceof Uint8Array) {
      dataToSign = new TextDecoder("utf-8").decode(dataToSign as Uint8Array);
    }

    console.log("credentialId", credentialId);
    const options = {
      challenge: new TextEncoder().encode(dataToSign).buffer,
      //allowCredentials: [{ id: credentialId, type: "public-key" }],
      userVerification: "preferred",
    };

    const assertion = await navigator.credentials.get({ publicKey: options });
    console.log("assertion", assertion);

    const authenticatorAssertionResponse = assertion?.response;
    this.clientDataJsonDecoded = JSON.parse(
      new TextDecoder("utf-8").decode(
        authenticatorAssertionResponse.clientDataJSON,
      ),
    );
    console.log("clientDataJSON decoded", this.clientDataJsonDecoded);
    this.authenticatorData = authenticatorAssertionResponse.authenticatorData;
    console.log("authenticator data", this.authenticatorData);
    return authenticatorAssertionResponse.signature;
  }
}

export async function verifyJwt(
  jwt: string,
  credId: Base64URLString,
  rawId: Uint8Array,
  authenticatorData: ArrayBuffer,
  clientDataJSON: object,
  publicKey: Uint8Array,
  signature: Base64URLString,
) {
  const options: PublicKeyCredentialRequestOptionsJSON =
    await generateAuthenticationOptions({
      rpID: window.location.hostname,
      // Require users to use a previously-registered authenticator
      // allowCredentials: userPasskeys.map(passkey => ({
      //   id: passkey.id,
      //   transports: passkey.transports,
      // })),
    });
  console.log("authentication options", options);

  const clientAuth = await startAuthentication(options);
  console.log("clientAuth", clientAuth);

  const verfOpts: VerifyAuthenticationResponseOpts = {
    response: clientAuth,
    authenticator: {
      credentialID: credId,
      credentialPublicKey: publicKey,
      counter: 0,
    },
    expectedChallenge: () => true, // options.challenge doesn't work
    expectedOrigin: window.location.origin,
    expectedRPID: window.location.hostname,
  };
  console.log("verfOpts", verfOpts);
  const verificationFromClient = await verifyAuthenticationResponse(verfOpts);
  console.log("client auth verification", verificationFromClient);

  const authData = toBase64Url(Buffer.from(authenticatorData));
  const bufferizedJson = toBase64Url(
    new TextEncoder().encode(JSON.stringify(clientDataJSON)),
  );
  const authOpts: VerifyAuthenticationResponseOpts = {
    response: {
      id: credId,
      rawId: toBase64Url(rawId),
      response: {
        authenticatorData: authData,
        clientDataJSON: bufferizedJson,
        signature: signature,
      },
      clientExtensionResults: {},
      type: "public-key",
    },
    expectedChallenge: () => true, // options.challenge doesn't work
    expectedOrigin: window.location.origin,
    expectedRPID: window.location.hostname,
    authenticator: {
      credentialID: credId,
      credentialPublicKey: publicKey,
      counter: 0,
    },
  };
  const verification = await verifyAuthenticationResponse(authOpts);
  console.log("auth verification", verification);

  const decoded = verifyJWT(jwt, {
    resolver: new Resolver({ peer: peerDidToDidDocument }),
  });
  return decoded;
}

async function peerDidToDidDocument(did: string): Promise<DIDResolutionResult> {
  if (!did.startsWith("did:peer:0z")) {
    throw new Error(
      "This only verifies a peer DID, method 0, encoded base58btc.",
    );
  }
  // this is basically hard-coded based on the results from the @aviarytech/did-peer resolver
  const id = did.split(":")[2];
  const multibase = id.slice(1);
  const encnumbasis = multibase.slice(1);
  const didDocument = {
    "@context": [
      "https://www.w3.org/ns/did/v1",
      "https://w3id.org/security/suites/jws-2020/v1",
    ],
    assertionMethod: [did + "#" + encnumbasis],
    authentication: [did + "#" + encnumbasis],
    capabilityDelegation: [did + "#" + encnumbasis],
    capabilityInvocation: [did + "#" + encnumbasis],
    id: did,
    keyAgreement: undefined,
    service: undefined,
    verificationMethod: [
      {
        controller: did,
        id: did + "#" + encnumbasis,
        publicKeyMultibase: multibase,
        type: "EcdsaSecp256k1VerificationKey2019",
      },
    ],
  };
  return {
    didDocument,
    didDocumentMetadata: {},
    didResolutionMetadata: { contentType: "application/did+ld+json" },
  };
}