On Mon, Oct 05, 2020 at 02:38:37PM +0100, Daniel P. Berrangé wrote: > On Mon, Oct 05, 2020 at 08:21:50AM -0500, Eric Blake wrote: > > On 10/3/20 1:50 PM, Richard W.M. Jones wrote: > > > New nbdkit_peer_pid, nbdkit_peer_uid and nbdkit_peer_gid calls can be > > > used on Linux (only) to read the peer PID, UID and GID from clients > > > connected over a Unix domain socket. This can be used in the > > > preconnect phase to add additional filtering. > > > > > > One use for this is to add an extra layer of authentication for local > > > connections. A subsequent commit will enhance the now misnamed > > > nbdkit-ip-filter to allow filtering on these extra fields. > > > > > > It appears as if it would be possible to implement this for FreeBSD > > > too (see comment in code). > > > --- > > > docs/nbdkit-plugin.pod | 47 +++++++++++++++-- > > > include/nbdkit-common.h | 3 ++ > > > server/nbdkit.syms | 3 ++ > > > server/public.c | 108 ++++++++++++++++++++++++++++++++++++++++ > > > 4 files changed, 156 insertions(+), 5 deletions(-) > > > > > > > > +=head2 C<nbdkit_peer_pid> > > > + > > > +(nbdkit E<ge> 1.24) > > > + > > > + int nbdkit_peer_pid (void); > > > + > > > +Return the peer process ID. This is only available when the client > > > +connected over a Unix domain socket, and only works for Linux. > > > + > > > +On success this returns the peer process ID. On error, > > > +C<nbdkit_error> is called and this call returns C<-1>. > > > > Is int always going to be sufficient? Or are there platforms with > > 64-bit pid_t? Mingw is an interesting beast; I've seen conflicting > > stories on whether 64-bit windows has 32- or 64-bit pids (the spawn APIs > > manage 64-bit handles, but other windows APIs return 32-bit int), so > > 64-bit pid_t on mingw does seem to be a real concern. > > IIUC, POSIX says pid_t is a signed integer, but doesn't specify the > size. Thus libvirt exposed pid_t as "signed long long" in our APIs > to be futureproof. > > > > + > > > +=head2 C<nbdkit_peer_uid> > > > + > > > +(nbdkit E<ge> 1.24) > > > + > > > + int nbdkit_peer_uid (void); > > > + > > > +Return the peer user ID. This is only available when the client > > > +connected over a Unix domain socket, and only works for Linux. > > > + > > > +On success this returns the user ID. On error, C<nbdkit_error> is > > > +called and this call returns C<-1>. > > > + > > > +=head2 C<nbdkit_peer_gid> > > > + > > > +(nbdkit E<ge> 1.24) > > > + > > > + int nbdkit_peer_gid (void); > > > > int for these two is probably fine. > > IIUC, gid_t/uid_t don't have their signed-ness specified by POSIX, > nor size, but you're required to cast negative values eg > > gid_t foo = (gid_t)-1; > > based on this, libvirt chose to expose them as "unsigned long long" to > maximise future proofing.
We need an in-band error indication. I wonder if there are systems with valid UID or GID == (uint64_t)-1 ? Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org _______________________________________________ Libguestfs mailing list Libguestfs@redhat.com https://www.redhat.com/mailman/listinfo/libguestfs