Interacting with Oauth1 API in cloudflare worker (Flickr)

Question

I'm needing to interact with the Flickr api from a cloudflare worker, but it's turning out to be exceedingly tricky.

My initial idea was to reach for the oauth1.0a library, but unfortunately it requires being passed a synchronous signature function. This is an issue because I need to use WebCrypto on the worker and it only exposes an asynchronous API.

Are there any other libraries I can use? I've currently spent hours trying to manually craft the request but keep getting errors saying the signature is bad.

This is my current attempt using someone's fork of oauth1.0a that adds support for an async signature function. This currently results in an "invalid_signature" response:

import OAuth from 'oauth-1.0a';

const CALLBACK_URL = "https://localhost:3000/oauth/callback";

const encoder = new TextEncoder();

async function signData(baseString: string, keyString: string) {
  return await crypto.subtle.importKey(
    'raw',
    encoder.encode(keyString),
    { name: 'HMAC', hash: 'SHA-1' },
    false,
    ['sign']
  ).then(key => {
    return crypto.subtle.sign(
      "HMAC",
      key,
      encoder.encode(baseString)
    );
  }).then(signature => {
    let b = new Uint8Array(signature);
    // base64 digest
    return btoa(String.fromCharCode(...b));
  });
}

export async function getRequestToken(consumerKey: string, consumerSecret: string) {
  const url = "https://www.flickr.com/services/oauth/request_token";
  const token = {
    key: consumerKey,
    secret: consumerSecret
  }
  const oauth = new OAuth({
    consumer: token,
    signature_method: 'HMAC-SHA1',
    // @ts-ignore
    hash_function: signData,
  });
  const requestData = {
    url,
    method: 'GET',
    data: {
      oauth_callback: CALLBACK_URL
    }
  };

  // @ts-ignore
  const authorisedRequest = await oauth.authorizeAsync(requestData, token);
  let params = new URLSearchParams();
  for (let [key, value] of Object.entries(authorisedRequest)) {
    params.append(key, value as string);
  }
  const response = await fetch(requestData.url + `?${params}`, {
    method: requestData.method,
  });

  const body = await response.text();
  const parsedBody = oauth.deParam(body);
  return parsedBody;
}