Title : Using the OpenBSD ports tree with dedicated users
Author: Solène
Date  : 11 January 2020
Tags  : openbsd68

If you want to contribute to OpenBSD ports collection you will want to enable
the`PORTS_PRIVSEP` feature. When this variable is set, ports system will use
dedicated users for tasks.

Source tarballs will be downloaded by the user
_pfetch and all compilation and packaging
will be done by the user _pbuild.

Those users are created at system install and pf have a default rule to
prevent _pbuild user doing network access. This will prevent ports
from doing network stuff, and this is what you want.

This adds a big security to the porting process and any malicious code
run by ports being compiled will be harmless.

In order to enable this feature, a few changes must be made.

The file /etc/mk.conf must contains

    PORTS_PRIVSEP=yes
    SUDO=doas

Then, /etc/doas.conf must allows your user to become \_pfetch and \_pbuild

    permit keepenv nopass solene as _pbuild
    permit keepenv nopass solene as _pfetch
    permit keepenv nopass solene as root

If you don't want to use the last line, there is an explanation in the
bsd.port.mk(5) man page.

Finally, within the ports tree, some permissions must be changed.

    # chown -R _pfetch:_pfetch /usr/ports/distfiles
    # chown -R _pbuild:_pbuild /usr/ports/{packages,plist,pobj,bulk}

If directories doesn't exist yet on your system (this is the case on a fresh
ports checkout / untar), you can create them with the commands:

    # install -d -o _pfetch -g _pfetch /usr/ports/distfiles
    # install -d -o _pbuild -g _pbuild /usr/ports/{packages,plist,pobj,bulk}

Now, when you run a command in the ports tree, privileges should be dropped to
according users.