On Sun, Nov 26, 2017 at 10:53:45AM -0500, Chuck Lever wrote: > > > On Nov 26, 2017, at 6:58 AM, Jeff Layton <jlayton@xxxxxxxxxx> wrote: > > > > On Thu, 2017-11-16 at 15:53 -0500, Chuck Lever wrote: > >>> On Nov 16, 2017, at 10:25 AM, Stefan Hajnoczi <stefanha@xxxxxxxxxx> wrote: > >>> > >>> On Tue, Nov 07, 2017 at 09:01:26AM -0500, Jeff Layton wrote: > >>>> On Tue, 2017-11-07 at 13:31 +0000, Stefan Hajnoczi wrote: > >>>>> On Tue, Oct 31, 2017 at 10:10:38AM -0400, Jeff Layton wrote: > >>>>>> On Fri, 2017-06-30 at 14:23 +0100, Stefan Hajnoczi wrote: > >>>>>>> @@ -595,6 +609,10 @@ int svc_port_is_privileged(struct sockaddr *sin) > >>>>>>> case AF_INET6: > >>>>>>> return ntohs(((struct sockaddr_in6 *)sin)->sin6_port) > >>>>>>> < PROT_SOCK; > >>>>>>> + case AF_VSOCK: > >>>>>>> + return ((struct sockaddr_vm *)sin)->svm_port <= > >>>>>>> + LAST_RESERVED_PORT; > >>>>>>> + > >>>>>>> default: > >>>>>>> return 0; > >>>>>>> } > >>>>>> > >>>>>> Does vsock even have the concept of a privileged port? I would imagine > >>>>>> that root in a guest VM would carry no particular significance from an > >>>>>> export security standpoint > >>>>>> > >>>>>> Since you're defining a new transport here, it might be nice write the > >>>>>> RFCs to avoid that distinction, if possible. > >>>>>> > >>>>>> Note that RDMA just has svc_port_is_privileged always return 1. > >>>>> > >>>>> AF_VSOCK has the same 0-1023 privileged port range as TCP. > >>>>> > >>>> > >>>> But why? And, given that you have 32-bits for a port with AF_VSOCK vs > >>>> the 16 bits on an AF_INET/AF_INET6, why is the range so pitifully small? > >>>> > >>>> Reserved ports are a bit of a dinosaur holdover from when being root on > >>>> a machine on the Internet meant something. With v4.1 it's much less of > >>>> an issue, but in the "olden days", reserved port exhaustion could be a > >>>> real problem. > >>>> > >>>> Mandating low ports can also be a problem in other way. Some well known > >>>> services use ports in the ephemeral range, and if your service starts > >>>> late and someone else has taken the port for an ephemeral one, you're > >>>> out of luck. > >>>> > >>>> I think we have to ask ourselves: > >>>> > >>>> Should the ability to open a low port inside of a VM carry any > >>>> significance at all to an RPC server? I'd suggest not, and I think it'd > >>>> be good to word the RFC to make that explicitly clear. > >>> > >>> AF_VSOCK has had the reserved port range since it was first merged in > >>> 2013. That's before my time but I do see some use for identifying > >>> connections coming from privileged processes. > >>> > >>> Given that TCP has the same privileged port range, is there any reason > >>> why AF_VSOCK would be any worse off than TCP for having it? > >> > >> I agree with Jeff that we need to think carefully about this. > >> > >> I don't especially care for the privileged port check, but: > >> > >> In this case, you are inventing an RPC transport that makes > >> it impossible to use strong security (ie, RPCSEC_GSS). We > >> should be careful about removing the check because only > >> AUTH_NULL and AUTH_UNIX security can be used in this kind > >> of deployment. > >> > > > > I know we've discussed this a bit, but does this transport _really_ > > preclude us from using RPCSEC_GSS? I know we don't have IP addresses > > here, but hosts on either end of a vsocket will have hostnames. > > Yes, even for AUTH_UNIX, something has to go in the "hostname" > field in the credential. Let's say the guest's uname. > > > > WRT kerberos, I don't see a reason why both hosts couldn't communicate > > with a KDC via other means, get tickets and then use those for > > authenticating over their vsock connection. vsock might make it harder > > to determine what SPN to use, but we could potentially work around that > > in other ways. > > "No network configuration" implies to me that the KDC (or > a proxy for it) would have to reside on the host. Their requirement is that network configuration not be mandatory, not that it always be absent. Then again maybe rpcsec_gss/vsock loses any advantage over rpcsec_gss/tcp if the former always requires a network anyway. > >> Note also that the NFSv4 standards require that implementations > >> can support RPCSEC_GSS. NFSv4 on VSOCK cannot. Something will > >> have to be done about that. Which might be: "Make an argument for why that requirement produces no useful result in this case". ? --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
