SFTPGo has insufficient sanitization of user provided rsync command

Impact

SFTPGo supports execution of a defined set of commands via SSH. Besides a set of default commands some optional commands can be activated, one of them being rsync: it is disabled in the default configuration and it is limited to the local filesystem, it does not work with cloud/remote storage backends.

Due to missing sanitization of the client provided rsync command, an authenticated remote user can use some options of the rsync command to read or write files with the permissions of the SFTPGo server process.

Patches

This issue was fixed in version v2.6.5 by checking the client provided arguments.

https://github.com/drakkan/sftpgo/commit/b347ab6051f6c501da205c09315fe99cd1fa3ba1