Re: Kerberised NFSv4 - everyone gets mapped to nobody on file access

On Thu, Mar 28, 2024 at 3:46 AM Andreas Kempe <kempe@lysator.liu.se> wrote:
>
> On Wed, Mar 27, 2024 at 03:20:03PM -0700, Rick Macklem wrote:
> > On Wed, Mar 27, 2024 at 10:17 AM Andreas Kempe <kempe@lysator.liu.se> wrote:
> > >
> > > On Tue, Mar 26, 2024 at 05:54:38PM -0700, Rick Macklem wrote:
> > > > On Tue, Mar 26, 2024 at 5:33 PM Rick Macklem <rick.macklem@gmail.com> wrote:
> > > > >
> > > > > Take a look at a packet capture in wireshark.
> > > > > Check that the @domain part of Owner and Owner_group attributes are
> > > > > the same and it is not a string of digits.
> > > > Oh, and just fyi, you can use tcpdump to capture the packets, something like:
> > > > # tcpdump -s 0 -w out.pcap host <nfs-server>
> > > > and then you can look at out.pcap whereever it is convenient to
> > > > install wireshark.
> > > > (I run it on this windows laptop.)
> > > > Don't bother to try and look at NFS with tcpdump. It doesn't know how
> > > > to decode it.
> > > >
> > > > > If the domain is not the same, you can use the -domain command line option
> > > > > on nfsuserd to set it.
> > > > > (Since this "domain" is underdefined, I'd suggest only ascii characters and
> > > > > all alphabetics in lower case.)
> > > > > If the client sends a string of digits, check to make sure the sysctl
> > > > > vfs.nfs.enable_uidtostring is set to 0.
> > > > >
> > >
> > > I'm using lysator.liu.se as the domain on both client and server. It
> > > seems to work since listing files give correct owners.
> > >
> > > I have dumped the traffic from mounting and creating a file named
> > > test file that shows up as owned by nobody. I get the following call
> > > made
> > >
> > >         NFS     438     V4 Call (Reply In 131) Open OPEN DH: 0x30a4c0aa/testfil
> > >
> > > In the OPEN (18) opcode, owner is set to
> > >
> > >                 0000   af 16 00 00 93 fc 00 00 07 76 0d 00
> > >
> > > while the server sets owner to ex. kempe@lysator.liu.se as expected
> > > when directory listings are made.
> > Doesn't make sense. What does wireshake show you for the Owner
> > attribute in the setable attributes of the Open arguments. It should flag
> > it as non-UTF8.
> >
>
> I'm afraid I don't really understand how to check this. Wireshark
> secifies "owner: <DATA>" if that says anything.
>
> > If you email me the pcap.out as an attachment, I'll look at it in wireshark.
> > The out.pcap should include both the Open that creates a file and an
> > "ls -l <file>", so there is a Getattr for the file as well.
> >
>
> I'll send you a capture off-list. Thank you for helping!
I looked at the capture. The server is definitely replying
"nobody@lysator.liu.se"
for both owner and owner_group for the file. You can see it in the
reply to Open, Lookup and
the Getattr (you need to go down past where it lists the attributes to
see what their
values are). It does know kempe@lysator.liu.se, since that is reported
for owner for the directory.

I have no idea why it would do that, but it's a Linux server so???

rick
>
> > rick
> > ps: If that is what is in the Owner field, all I can suggest is that was what
> >       a getpwnam() returned on the client. Possibly some weirdness with LDAP.
> >       (I never use LDAP. Only a local /etc/passwd.)
> >
> > >
> > > vfs.nfs.enable_uidtostring is 0 on the client machine and I am not
> > > quite able to make sense of what the 12 bytes in the owner field are
> > > supposed to be. They are not the ASCII representation and nither my
> > > user's GID and UID that are both 0x7b02.
> > >
> > > // Andreas Kempe
> >
>