`getDownloadURL` function fails in emulator mode if storage rules are not allowed

[cabljac]

Reposting this issue from firebase-functions firebase/firebase-functions#1547 as it seems to be an issue with the storage emulator rather than the functions SDK. Feel free to close and correct me if i'm mistaken here.

[REQUIRED] Environment info

firebase-tools: firebase-tools: 13.3.1
node: v20.10.0
firebase-admin: 12.0.0

[REQUIRED] Test case

index.ts

import {initializeApp} from "firebase-admin/app";
import {getDownloadURL, getStorage} from "firebase-admin/storage";
import {onRequest} from "firebase-functions/v2/https";
initializeApp();

export const uploadFile = onRequest(async (_req, res) => {
  // Create a CSV string
  const csvData = "Name,Email,Balance";

  // Create a new file in the bucket
  const bucket = getStorage().bucket();
  const file = bucket.file("csvs/temp.csv");

  // Write the csv data to the file
  await file.save(csvData, {
    metadata: {
      contentType: "text/csv",
    },
  });

  // Get the download url
  const downloadUrl = await getDownloadURL(file);

  res.send(`Download URL: ${downloadUrl}`);
});

With rules:

rules_version = '2';
service firebase.storage {
  match /b/{bucket}/o {
    match /{allPaths=**} {
      allow read, write: if false;
    }
  }
}

[REQUIRED] Steps to reproduce

1. Create a new firebase cloud functions project with typescript and storage emulator
2. Copy the above provided sample codes in functions/src/index.ts and storage.rules respectively.
3. Run firebase emulators:start
4. Send request to the uploadFile function using postman or whatever
5. See error / crash
6. Now update storage.rules to allow all paths (i.e. allow read, write: if true;)
7. Repeat step 4
8. See a download url is sent

[REQUIRED] Expected behavior

As cloud functions don't rely on and basically bypass the firestore.rules, database.rules and storage.rules, a download url should be fetched no matter what the storage.rules are set to.

[REQUIRED] Actual behavior

functions: Error: Permission denied. No READ permission.

[aalej]

Thanks for the detailed report @cabljac! Looking though the information provided, I think this is a similar issue to #7946. That said, I'm going to go ahead and close this as a duplicate, but please let me know if you think this is different issue and needs to be reopened.