storage.rules

rules_version = '2';

// Returns true if the uploaded file is an image and its size is below the given number of MB.
function isImageBelowMaxSize(maxSizeMB) {
  return request.resource.size < maxSizeMB * 1024 * 1024
      && request.resource.contentType.matches('image/.*');
}

function isSignedIn() {
    return request.auth != null
                    && request.auth.token.firebase.sign_in_provider != 'anonymous'
}


service firebase.storage {
  match /b/{bucket}/o {
    match /users/{userId}/{fileName} {
      allow write, update: if isSignedIn() && request.auth.uid == userId && isImageBelowMaxSize(5);
      allow read;
    }

    match /posts/{postId}/{fileName} {
      allow write: if isSignedIn() && isImageBelowMaxSize(5);
      allow read;
    }
  }
}