Firebase Storage rule different for a specific folder

Question

I have a firebase storage bucket with this hierarchy eg

-Bucket
    --UserData
    --Folder A
    --Folder B
    --Folder C
    --Folder D

I want to apply these rules for [Folder A, Folder B, Folder C, Folder D]

match /{allPaths=**} {
      allow read;
      allow write;
}

but for UserData folder I want to apply these rules

match /UserData/{user_id} {
      allow read; 
      allow write: if request.auth != null && request.auth.uid == user_id;
}

in real life, I have far more folders [A,B,C,D........] and only one folder [UserData] so it is not possible to write storage rule for each specific folders

Answer 1

What you're trying to do is not supported by security rules. You would have to list out each top-level folder separately - there are no wildcards for this.

The easiest way to apply the same rules to unstructured folder content is to organize all that content under a single prefix (folder), and write the rules for that prefix. If you moved everything under EverythingElse, then you could apply a single rule to all of it recursively:

match /UserData/{user_id} {
  allow read; 
  allow write: if request.auth != null && request.auth.uid == user_id;
}
match /EverythingElse/{allPaths=**} {
  // your rules here
}