Date: Fri, 27 Nov 2020 12:15:27 +0000 From: "Bjoern A. Zeeb" <bz@FreeBSD.org> To: "Kyle Evans" <kevans@freebsd.org> Cc: freebsd-jail <freebsd-jail@freebsd.org>, freebsd-arch@freebsd.org, trustedbsd-discuss@freebsd.org Subject: Re: RFC: Jail privsets Message-ID: <06F654BB-B087-4AE5-8599-E5837A85A850@FreeBSD.org> In-Reply-To: <CACNAnaEKoBppjG8HH0KgYQv0EHPUcHmB3teyw1PQrjG3xsbXYQ@mail.gmail.com> References: <CACNAnaEKoBppjG8HH0KgYQv0EHPUcHmB3teyw1PQrjG3xsbXYQ@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 27 Nov 2020, at 5:04, Kyle Evans wrote: > (Cross-posting to -arch and -jail for maximum reach) and trustedbsd now as that is where priv(9) came from [ http://www.trustedbsd.org/privileges.html ] > A couple of times recently, I've had a need or desire to increase or > decrease privileges available to jails I create to some extent. You > can write a MAC policy for this, but at some point the downsides of > MAC policies for this became clear: it's either non-trivial to allow > the kind of flexibility you may need in configuring some of these > jails, and you have to rebuild the module otherwise. > > I've got a generally functional patch at [1] that is an approach I'd > like to request comments on for refining jail privileges. It creates a > privset that can be assigned on a per-jail basis, and a creator with > PRIV_JAIL_SETPRIVS can specify any privset mask that's a subset of the > parent prison. > > If no privset was specified at creation time, then we use the default > logic that was previously in prison_priv_check(). prison_priv_check() > has been replaced with a much simpler check of the prison's privset > for the given privilege. > > As I was writing this, I identified the first problem with it: it > doesn't currently respond to ALLOW_* updates and grant the appropriate > privileges after initialization time -- this is a pretty easy fix, and > I will do so if anyone else finds this useful. > > The other caveat is that I have no idea if there's a useful way to > expose this to jail(8) users, but they're not really the primary > target for this -- the primary target is system application developers > that want more fine control over what a jail they're creating can do. > > This is an excellent foot-gun, but with great power comes great > responsibility. While I like the idea I am not sure I like the way it is done. I think it was a long-time goal of Robert (which just never happened to day) to make priv(9) configurable from user space. I am just not sure if hanging it off jails is the right answer. The jail-set is certainly the most extensive in the system, but the priv checks are everywhere and hanging them off, say a thread or credential, would allow people to do a lot more (also non-foot-shooting) than just modifying jails. That said, jails pretty much tie into the entire td/cred concept already so we could happily use them as a jumping platform for experimenting before extending it to the entire system if we are clear that this might not be the final stable way of doing things? Lots of health, /bz
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?06F654BB-B087-4AE5-8599-E5837A85A850>