Date: Mon, 20 Aug 2018 17:02:03 +0200 From: Stefan Bethke <stb@lassitu.de> To: Eugene Grosbein <eugen@grosbein.net> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: Bind to port <1024 in jail Message-ID: <89646FDB-F1A9-4070-87EC-22C0CFAFF4E7@lassitu.de> In-Reply-To: <6bfc8608-946d-39eb-cc57-88b3dc3bd7c5@grosbein.net> References: <75536186-7D58-498C-BFC6-9284EB7CB444@lassitu.de> <6bfc8608-946d-39eb-cc57-88b3dc3bd7c5@grosbein.net>
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Am 20.08.2018 um 16:59 schrieb Eugene Grosbein <eugen@grosbein.net>: > > 20.08.2018 21:47, Stefan Bethke wrote: > >> I have a Go program (acme-dns) that wants to bind 53, 80, and 443, and I’d rather have it run as a non-privileged user. The program doesn’t provide a facility to drop privs after binding the ports. I’m planning to run it in a jail. >> >> After some googling, it appears that a couple of years ago I should have been able to do: >> sysctl net.inet.ip.portrange.reservedhigh=0 >> and allow all processes to bind to „low“ ports. This does not work in my jails on a 11-stable host. >> >> $ sudo sysctl net.inet.ip.portrange.reservedhigh=0 >> net.inet.ip.portrange.reservedhigh: 1023 >> sysctl: net.inet.ip.portrange.reservedhigh=0: Operation not permitted >> >> Securelevel should not interfere: >> $ sysctl kern.securelevel >> kern.securelevel: -1 >> >> Is there a way to allow regular processes to bind to low ports? > > Yes. Just use mac_portacl kernel module: kldload mac_portacl > > Once loaded, it duplicates net.inet.ip.portrange.reservedhigh protection > with its own security.mac.portacl.port_high, so it's safe to disable > "reservedhigh" for whole system by running sysctl net.inet.ip.portrange.reservedhigh=0 > for host. > > The trick is that mac_portacl provides a way to selectively give permission for non-root UID > to bind low ports: > > security.mac.portacl.rules=uid:88:tcp:80,uid:88:tcp:443,uid:53:tcp:53,uid:53:udp:53 > > It works just fine for a host and I use it for name servers utilizing port 53 > for a box with dynamically created interfaces, so it may bind the port for distinct IP addresses > after it dropped privilegies when new interface is created and get new IP assigned. > > I have not tried it for a jails, though. Please try and respond. Thanks, but do I understand correctly that the security.mac.portacl.rules are system-wide and not per-jail? I’m running ~10 jails on this host, and I don’t want to allow all of them to bind to low ports. Stefan -- Stefan Bethke <stb@lassitu.de> Fon +49 151 14070811
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