> On May 10, 2018, at 3:07 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote:
>
> On Thu, May 10, 2018 at 2:09 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>>
>>
>>> On May 10, 2018, at 1:40 PM, Olga Kornievskaia <aglo@xxxxxxxxx> wrote:
>>>
>>> On Wed, May 9, 2018 at 5:19 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>>>> I'm right on the edge of my understanding of how this all works.
>>>>
>>>> I've re-keyed my NFS server. Now on my client, I'm seeing this on
>>>> vers=4.0,sec=sys mounts:
>>>>
>>>> May 8 16:40:30 manet kernel: NFS: NFSv4 callback contains invalid cred
>>>> May 8 16:40:30 manet kernel: NFS: NFSv4 callback contains invalid cred
>>>> May 8 16:40:30 manet kernel: NFS: NFSv4 callback contains invalid cred
>>>>
>>>> manet is my client, and klimt is my server. I'm mounting with
>>>> NFS/RDMA, so I'm mounting hostname klimt.ib, not klimt.
>>>>
>>>> Because the client is using krb5i for lease management, the server
>>>> is required to use krb5i for the callback channel (S 3.3.3 of RFC
>>>> 7530).
>>>>
>>>> After a SETCLIENTID, the client copies the acceptor from the GSS
>>>> context it set up, and uses that to check incoming callback
>>>> requests. I instrumented the client's SETCLIENTID proc, and I see
>>>> this:
>>>>
>>>> check_gss_callback_principal: acceptor=nfs@xxxxxxxxxxxxxxxxxxxxxxxx, principal=host@xxxxxxxxxxxxxxxxxxxxx
>>>>
>>>> The principal strings are not equal, and that's why the client
>>>> believes the callback credential is bogus. Now I'm trying to
>>>> figure out whether it is the server's callback client or the
>>>> client's callback server that is misbehaving.
>>>>
>>>> To me, the server's callback principal (host@klimt) seems like it
>>>> is correct. The client would identify as host@manet when making
>>>> calls to the server, for example, so I'd expect the server to
>>>> behave similarly when performing callbacks.
>>>>
>>>> Can anyone shed more light on this?
>>>
>>> What are your full hostnames of each machine and does the reverse
>>> lookup from the ip to hostname on each machine give you what you
>>> expect?
>>>
>>> Sounds like all of them need to be resolved to <>.ib.1015grager.net
>>> but somewhere you are getting <>.1015grager.net instead.
>>
>> The forward and reverse mappings are consistent, and rdns is
>> disabled in my krb5.conf files. My server is multi-homed; it
>> has a 1GbE interface (klimt.1015granger.net); an FDR IB
>> interface (klimt.ib.1015granger.net); and a 25 GbE interface
>> (klimt.roce.1015granger.net).
>
> Ah, so you are keeping it very interesting...
>
>> My theory is that the server needs to use the same principal
>> for callback operations that the client used for lease
>> establishment. The last paragraph of S3.3.3 seems to state
>> that requirement, though it's not especially clear; and the
>> client has required it since commit f11b2a1cfbf5 (2014).
>>
>> So the server should authenticate as nfs@xxxxxxxx and not
>> host@klimt, in this case, when performing callback requests.
>
> Yes I agree that server should have authenticated as nfs@xxxxxxxx and
> that's what I see in my (simple) single home setup.
>
> In nfs-utils there is code that deals with the callback and comment
> about choices for the principal:
> * Restricting gssd to use "nfs" service name is needed for when
> * the NFS server is doing a callback to the NFS client. In this
> * case, the NFS server has to authenticate itself as "nfs" --
> * even if there are other service keys such as "host" or "root"
> * in the keytab.
> So the upcall for the callback should have specifically specified
> "nfs" to look for the nfs/<hostname>. Question is if you key tab has
> both:
> nfs/klmit and nfs/klmit.ib how does it choose which one to take. I'm
> not sure. But I guess in your case you are seeing that it choose
> "host/<>" which would really be a nfs-utils bug.
I think the upcall is correctly requesting an nfs/ principal
(see below).
Not only does it need to choose an nfs/ principal, but it also
has to pick the correct domain name. The domain name does not
seem to be passed up to gssd. fs/nfsd/nfs4state.c has this:
749 static struct rpc_cred *callback_cred;
750
751 int set_callback_cred(void)
752 {
753 if (callback_cred)
754 return 0;
755 callback_cred = rpc_lookup_machine_cred("nfs");
756 if (!callback_cred)
757 return -ENOMEM;
758 return 0;
759 }
760
761 void cleanup_callback_cred(void)
762 {
763 if (callback_cred) {
764 put_rpccred(callback_cred);
765 callback_cred = NULL;
766 }
767 }
768
769 static struct rpc_cred *get_backchannel_cred(struct nfs4_client *clp, struct rpc_clnt *client, struct nfsd4_session *ses)
770 {
771 if (clp->cl_minorversion == 0) {
772 return get_rpccred(callback_cred);
773 } else {
774 struct rpc_auth *auth = client->cl_auth;
775 struct auth_cred acred = {};
776
777 acred.uid = ses->se_cb_sec.uid;
778 acred.gid = ses->se_cb_sec.gid;
779 return auth->au_ops->lookup_cred(client->cl_auth, &acred, 0);
780 }
781 }
rpc_lookup_machine_cred("nfs"); should request an "nfs/" service
principal, shouldn't it?
Though I think this approach is incorrect. The server should not
use the machine cred here, it should use a credential based on
the principal the client used to establish it's lease.
> What's in your server's key tab?
[root@klimt ~]# klist -ke /etc/krb5.keytab
Keytab name: FILE:/etc/krb5.keytab
KVNO Principal
---- --------------------------------------------------------------------------
4 host/klimt.1015granger.net@xxxxxxxxxxxxxxx (aes256-cts-hmac-sha1-96)
4 host/klimt.1015granger.net@xxxxxxxxxxxxxxx (aes128-cts-hmac-sha1-96)
4 host/klimt.1015granger.net@xxxxxxxxxxxxxxx (des3-cbc-sha1)
4 host/klimt.1015granger.net@xxxxxxxxxxxxxxx (arcfour-hmac)
3 nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx (aes256-cts-hmac-sha1-96)
3 nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx (aes128-cts-hmac-sha1-96)
3 nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx (des3-cbc-sha1)
3 nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx (arcfour-hmac)
3 nfs/klimt.ib.1015granger.net@xxxxxxxxxxxxxxx (aes256-cts-hmac-sha1-96)
3 nfs/klimt.ib.1015granger.net@xxxxxxxxxxxxxxx (aes128-cts-hmac-sha1-96)
3 nfs/klimt.ib.1015granger.net@xxxxxxxxxxxxxxx (des3-cbc-sha1)
3 nfs/klimt.ib.1015granger.net@xxxxxxxxxxxxxxx (arcfour-hmac)
3 nfs/klimt.roce.1015granger.net@xxxxxxxxxxxxxxx (aes256-cts-hmac-sha1-96)
3 nfs/klimt.roce.1015granger.net@xxxxxxxxxxxxxxx (aes128-cts-hmac-sha1-96)
3 nfs/klimt.roce.1015granger.net@xxxxxxxxxxxxxxx (des3-cbc-sha1)
3 nfs/klimt.roce.1015granger.net@xxxxxxxxxxxxxxx (arcfour-hmac)
[root@klimt ~]#
As a workaround, I bet moving the keys for nfs/klimt.ib to
the front of the keytab file would allow Kerberos to work
with the klimt.ib interface.
> An output from gssd -vvv would be interesting.
May 10 14:43:24 klimt rpc.gssd[1191]: #012handle_gssd_upcall: 'mech=krb5 uid=0 target=host@xxxxxxxxxxxxxxxxxxxxx service=nfs enctypes=18,17,16,2
3,3,1,2 ' (nfsd4_cb/clnt0)
May 10 14:43:24 klimt rpc.gssd[1191]: krb5_use_machine_creds: uid 0 tgtname host@xxxxxxxxxxxxxxxxxxxxx
May 10 14:43:24 klimt rpc.gssd[1191]: Full hostname for 'manet.1015granger.net' is 'manet.1015granger.net'
May 10 14:43:24 klimt rpc.gssd[1191]: Full hostname for 'klimt.1015granger.net' is 'klimt.1015granger.net'
May 10 14:43:24 klimt rpc.gssd[1191]: Success getting keytab entry for 'nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx'
May 10 14:43:24 klimt rpc.gssd[1191]: gssd_get_single_krb5_cred: principal 'nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx' ccache:'FILE:/tmp/krb5ccmachine_1015GRANGER.NET'
May 10 14:43:24 klimt rpc.gssd[1191]: INFO: Credentials in CC 'FILE:/tmp/krb5ccmachine_1015GRANGER.NET' are good until 1526064204
May 10 14:43:24 klimt rpc.gssd[1191]: creating tcp client for server manet.1015granger.net
May 10 14:43:24 klimt rpc.gssd[1191]: creating context with server host@xxxxxxxxxxxxxxxxxxxxx
May 10 14:43:24 klimt rpc.gssd[1191]: doing downcall: lifetime_rec=76170 acceptor=host@xxxxxxxxxxxxxxxxxxxxx
May 10 14:44:31 klimt rpc.gssd[1191]: #012handle_gssd_upcall: 'mech=krb5 uid=0 target=host@xxxxxxxxxxxxxxxxxxxxx service=nfs enctypes=18,17,16,23,3,1,2 ' (nfsd4_cb/clnt1)
May 10 14:44:31 klimt rpc.gssd[1191]: krb5_use_machine_creds: uid 0 tgtname host@xxxxxxxxxxxxxxxxxxxxx
May 10 14:44:31 klimt rpc.gssd[1191]: Full hostname for 'manet.1015granger.net' is 'manet.1015granger.net'
May 10 14:44:31 klimt rpc.gssd[1191]: Full hostname for 'klimt.1015granger.net' is 'klimt.1015granger.net'
May 10 14:44:31 klimt rpc.gssd[1191]: Success getting keytab entry for 'nfs/klimt.1015granger.net@xxxxxxxxxxxxxxx'
May 10 14:44:31 klimt rpc.gssd[1191]: INFO: Credentials in CC 'FILE:/tmp/krb5ccmachine_1015GRANGER.NET' are good until 1526064204
May 10 14:44:31 klimt rpc.gssd[1191]: INFO: Credentials in CC 'FILE:/tmp/krb5ccmachine_1015GRANGER.NET' are good until 1526064204
May 10 14:44:31 klimt rpc.gssd[1191]: creating tcp client for server manet.1015granger.net
May 10 14:44:31 klimt rpc.gssd[1191]: creating context with server host@xxxxxxxxxxxxxxxxxxxxx
May 10 14:44:31 klimt rpc.gssd[1191]: doing downcall: lifetime_rec=76103 acceptor=host@xxxxxxxxxxxxxxxxxxxxx
>> This seems to mean that the server stack is going to need to
>> expose the SName in each GSS context so that it can dig that
>> out to create a proper callback credential for each callback
>> transport.
>>
>> I guess I've reported this issue before, but now I'm tucking
>> in and trying to address it correctly.
--
Chuck Lever
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