the file on firebase storage is not accessible if metadata updated

Question

I'm not sure if this is a bug. It works last month and runs into issues a couple of weeks later. I will post a bug report if this issue cannot be resolved.

I have an Android app that allows users to share files with another person via email address. When the file was uploaded to the Firebase Storage successfully, the app pops up a dialog to allow users to type in the address of the recipient for file sharing. And the email address will be written into custom metadata as a key.

In Firebase Storage, each user uploads files to their own folder(email address as folder name). The Storage rules are listed below. The idea is users only can access the files in their own folders, and has read permission for shared files.

rules_version = '2';
service firebase.storage {
  match /b/{bucket}/o {  
    // read and write permission for owners
    match /users/{userEmail}/{allPaths=**} {
        allow read, write: if request.auth.token.email == userEmail && request.auth.token.email_verified;
    }
    // read permission for shared files
    match /users/{userEmail}/{allPaths=**} {
        allow read: if request.auth != null && request.auth.token.email != userEmail && request.auth.token.email in resource.metadata.keys() && request.auth.token.email_verified;
    }
    // samples are public to read
    match /samples/{allPaths=**} {
        allow read;
    }
  }
}

The rules were modified from this thread. Firebase rules: dynamically give access to a specific user

To work with the shared files, the app writes the recipient's email address to the file as a key of custom metadata. The Android code for updating metadata is listed below.

private void updateMetadataForSharing(String fileLocation, String documentId, String recipientEmail) {
    // write file metadata
    StorageMetadata metadata = new StorageMetadata.Builder()
            .setCustomMetadata(recipientEmail,"")
            .build();
    // Update metadata properties
    StorageReference storageRef = storage.getReference();
    StorageReference fileRef = storageRef.child(fileLocation);
    fileRef.updateMetadata(metadata)
            .addOnSuccessListener(new OnSuccessListener<StorageMetadata>() {
                @Override
                public void onSuccess(StorageMetadata storageMetadata) {
                    // Updated metadata is in storageMetadata
                    Toast.makeText(ReviewActivity.this, "The file has been shared to "+recipientEmail+", please paste the sharable link from clipboard.", Toast.LENGTH_LONG).show();
                    String sharableLink = "https://web.app.com/?u="+documentId;
                    ClipboardManager clipboard = (ClipboardManager) getSystemService(Context.CLIPBOARD_SERVICE);
                    ClipData clip = ClipData.newPlainText("sharable link", sharableLink);
                    clipboard.setPrimaryClip(clip);
                }
            })
            .addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception exception) {
                    // Uh-oh, an error occurred!
                    Toast.makeText(ReviewActivity.this, "Error occurred attempting to share the file to "+recipientEmail, Toast.LENGTH_LONG).show();
                }
            });
}

But the file is not accessible after metadata updated. It was fine if the no metadata written to the file. The web app showed the errors as the picture shown. web app error message for failing to download the file

I assume it may associate with the access token of file. It has nothing to do with the rules, because it's still not working when I grant all permissions temporarily. Please advise. Thanks.

Answer 1

I ran into the same problem today with an uploaded file not being accessible after the metadata was updated. It seems like the file becomes inaccessible if the metadata key contains the @ character. For some reason the key cannot contain the character but its fine in the value.