duplicity-team team mailing list archive

[James Wilson <jmw@xxxxxxxxxxxx>]

Hey, I wanted to resume this discussion. Since April a couple of things have changed: 1) I helped the maintainer of libcap-ng to fix its build issues as of 0.7.4-3 that is available in sid and stretch, and 2) I found another way to limit root capabilities using file capabilities that has a smaller footprint (it doesn't create a new system user).

The catch for #2 is that file capabilities need a real binary executable, because the kernel ignores file capabilities set on interpreted programs. I found a utility called cx_Freeze that uses a minimal binary loader to start up the python environment and run a bundled script. Then we can set inherited file capabilities on /usr/bin/duplicity in the post-install script. The inherited capabilities cannot be harnessed unless the executing user also has the same capabilities in their inherited set, which the system administrator can take care of by granting inherited capabilities on the backup user. The easiest way to do this is using pam_cap.so. One possible issue is that cx_Freeze is available as an ubuntu package (cx-freeze) but it is not in Debian.

I've been running a custom version of duplicity with this setup for several weeks. It's a cleaner solution since it doesn't require a specific duplicity user to exist. The tradeoff is that system-wide backups require more setup since the system administrator will need to set up the inherited user capabilities. It's worth adding some documentation on how to do all of this.

Are either of these directions something you'd like to consider now?
-- 
https://code.launchpad.net/~jmwilson/duplicity/capabilities/+merge/257488
Your team duplicity-team is requested to review the proposed merge of lp:~jmwilson/duplicity/capabilities into lp:duplicity.