If bitcoind and tor run as different users, bitcoind cannot authenticate with tor control.

This can be resolved by adding the user running bitcoind to the user group of the tor user (in my case debian-tor).

Logs indicate permission issues with the authcookie.

tor: Authentication cookie /var/run/tor/control.authcookie could not be opened (check permissions)

Using hashedpassword authentication did not resolve this issue because at some point it fell back to the cookie method as well.

I'm not sure this is exactly a bug, but it was challenging for me to figure out the solution to the issue. If this isn't a bug would it be appropriate for me to add documentation of this to the tor readme?