Date: Sun, 27 Sep 2020 15:25:36 -0500 From: Kyle Evans <kevans@freebsd.org> To: Warner Losh <imp@bsdimp.com> Cc: Yuri <yuri@rawbw.com>, Freebsd hackers list <freebsd-hackers@freebsd.org> Subject: Re: Is it possible to exit the chroot(2) environment? Message-ID: <CACNAnaGgk6NoxD3kXGpbtAZk%2Bbc%2B2XVc%2B1sO06QU1e%2BKp9CZwQ@mail.gmail.com> In-Reply-To: <CANCZdfrzCuR4W-JzoFPyW6WCwVJGwQfuesjmCBMRMSnvfXdv7Q@mail.gmail.com> References: <b6412618-02ec-1dbd-f474-b4412d7b774b@rawbw.com> <CANCZdfqJ14-Cpvi9%2Bd%2BHRgWbHk7vDUNNOKLUVOC9iBUqZKX=Pw@mail.gmail.com> <CACNAnaFVg2yZnWbfC=MmPfQ==XZYssHFuz%2BCjz%2B67TkZ108qRA@mail.gmail.com> <CACNAnaF-psLeTzwk=HygP4ESEynRyR-m62T1FAjw=ON6J2PVTg@mail.gmail.com> <a488f94a-6efc-27f3-d0a4-489f6f99772d@rawbw.com> <CACNAnaG_u1aVRJpKeb9n0rK4UqRRZDGBt7i=iRtPf-7kxqYQBw@mail.gmail.com> <9fa46833-63c2-a77f-98dd-111f6502dc74@rawbw.com> <CACNAnaFqtpDkd76Z3vAUMcCMwTpMyfy91NPyufeVd%2B8UAqZHKQ@mail.gmail.com> <CANCZdfrzCuR4W-JzoFPyW6WCwVJGwQfuesjmCBMRMSnvfXdv7Q@mail.gmail.com>
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On Sun, Sep 27, 2020 at 3:15 PM Warner Losh <imp@bsdimp.com> wrote: > > > > On Sun, Sep 27, 2020, 2:09 PM Kyle Evans <kevans@freebsd.org> wrote: >> >> On Sun, Sep 27, 2020 at 3:04 PM Yuri <yuri@rawbw.com> wrote: >> > >> > On 2020-09-27 12:56, Kyle Evans wrote: >> > > kern.chroot_allow_open_directories to some value that isn't 0 or 1. >> > >> > >> > It succeeds with kern.chroot_allow_open_directories=2. >> > >> > >> >> Ok, so Warner's proposal was correct and we've verified the semantics >> work out the same, this is simply a behavioral difference in that >> we're a little more strict -- presumably to make it less trivial to >> break out of a chroot. >> >> I suspect a default change for the sysctl/behavior is unlikely, your >> best bet to move forward is probably to work out if they really need >> to have dangling directories open and correct that if at all possible. > > > To be fair, we are more strict than Linux... but it is documented. Though if there were some way to highlight that better, I'd be open to working that in. Maybe a sentence on 'any other value' paragraph talking about traditional behavior... > +1. I think an additional sentence pointing out that that's the traditional behavior would outline that this is perhaps what's needed, maybe with a specific EPERM reference. It's tempting to also propose switching it to the even-more-strict 0 at some point, perhaps considering a procctl(2) if we really find some scenarios where it's absolutely necessary... we'll leave that battle to a different day, though.
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