Google Drive SDK: Modify application-owned file as user

0
votes

I have a Google App Engine application that:

  1. Authenticates a user and authorizes the drive.file scope;

  2. Creates and stores a file on behalf of a user via an application-owned 'regular' Google account;

  3. Shares that file with the user (grants write access).

However, when a user attempts to update one of these files via an authorized Drive service created by the app, the following exception is raised:

403: The authenticated user has not granted the app {appId} access to the file {fileId}.

What am I missing? Given that the file was both initially created by and is still owned by the application, why is it necessary for the user to specifically grant the application access to the file?

My goal is for users to modify files (to which they have write access, that are stored in/owned by an application-owned account) as themselves in order to maintain appropriate 'last modifying user' attribution.

Is there anything I can do to work around this, other than (a) authorizing the 'drive' scope, (b) using the Google Picker or Drive UI to 'explicitly' open files with my app (does this imply the file must live in the user's Drive account?), or (c) having my application-owned account perform all file update operations?

1
google-app-enginegoogle-drive-api

1 Answers

2
votes

File scope authorization is currently done as a user-app pair. Each user must individually authorize the app to access to the file.

Given that, I think you've identified the possible solutions. For b, the file doesn't need to be owned by the user, they just need access to it. Having shared it with them should be sufficient.