On Mon, 2017-11-27 at 11:46 -0500, Bruce Fields wrote: > 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. A proxy would be fine. The whole point of krb5 is that you can't rely on the network anyway... > > 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". ? I guess it just seems like we can allow RPCSEC_GSS over this channel, even if it's not terribly useful today. I don't think we ought to word in a way that specifically forbids it, unless it really does fall short of some key requirement. GSSAPI is more than just krb5 too...maybe LIPKEY will make a comeback someday? :) -- Jeff Layton <jlayton@xxxxxxxxxx> -- 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
