On Mon, Aug 10, 2026 at 11:55 AM Daniel P. Berrangé <[email protected]> wrote:
> On Mon, Aug 10, 2026 at 11:37:34AM +0300, Kostiantyn Kostiuk wrote: > > On Mon, Aug 10, 2026 at 11:20 AM Daniel P. Berrangé <[email protected] > > > > wrote: > > > > > On Mon, Aug 10, 2026 at 11:06:27AM +0300, Kostiantyn Kostiuk wrote: > > > > Hi Valentino, > > > > > > > > Sorry for the long delay. > > > > I have a question for you > > > > > > > > On Tue, Jul 14, 2026 at 7:10 PM Valentino Paulon < > > > > [email protected]> wrote: > > > > > > > > > > > So, you propose to call seteuid/setegid before any I/O > operation? > > > > > > > > > > > > Yes, specifically for the SSH commands, because they're unusual > in > > > > > > that we're doing stuff on behalf of an unprivileged user. > > > > > > > > > > +1 on the euid/egid direction -- as the reporter that's the > outcome I > > > > > was hoping for. It confines every step (read, mkdir, create, > rename, > > > > > chown) to what the target user could already do himself, which > removes > > > > > the whole TOCTOU class instead of chasing one instance of it. > > > > > > > > > > A few implementation details that tend to bite with this pattern, > in > > > > > case they save a round-trip: > > > > > > > > > > - drop the supplementary groups too, not just egid: initgroups() > (or > > > > > setgroups() with the user's list) while still root, otherwise the > > > > > agent's effective access won't match the user's in either direction > > > > > > > > > > > > > Technically, there is no limitation to running QGA in unprivileged > mode. > > > > Normally, it is a system daemon, but this is not mandatory. > > > > In this case, we can not call initgroups because the caller must > > > > have CAP_SETGID. > > > > We can call initgroups only when QGA runs as root. What do you think? > > > > > > In any practical sense it is a system daemon given the set of commands > > > it is exposing. Thus, IMHO, deploying as an unprivileged user should > > > be considered a broken deployment. We could make that explicit by > > > refusing to launch. > > > > > > > Makes sense, but we have one more issue with QGA unit tests in this case. > > They are called by an unprivileged user (build user), and initgroups > broke > > it. > > Is it possible to enter the namespace automatically by the test engine? > > We can't assume that is possible todo in all build/test environments. > > Doing things as different user accounts feels pretty dubious for the > scope of a unit test too - that is really functional or integration > testing. > > Can we somehow restructure the tests and/or agent code to avoid the > changing groups stuff in unit tests. > There are two possible options: 1. add #ifdef QGA_BUILD_UNIT_TEST into qmp_guest_ssh_* functions 2. check the current uid and skip initgroups if it is zero (my initial question) > > With regards, > Daniel > -- > |: https://berrange.com ~~ https://hachyderm.io/@berrange :| > |: https://libvirt.org ~~ https://entangle-photo.org :| > |: https://pixelfed.art/berrange ~~ https://fstop138.berrange.com :| > >
