On Thu, May 10, 2018 at 3:23 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
>
>> 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'
I think that's the problem. This should have been
klimt.ib.1015granger.net. nfs-utils just calls gethostname() to get
the local domain name. And this is what it'll match against the key
tab entry. So I think even if you move the key tabs around it probably
will still pick nfs@xxxxxxxxxxxxxxxxxxxxx.
Honestly, I'm also surprised that "target=host@xxxxxxxxxxxxxxxxxxxxx"
and not "target=host@xxxxxxxxxxxxxxxxxxxxxxxx". What principal name
did the client use to authenticate to the server? I also somehow
assumed that this should have been
"target=nfs@xxxxxxxxxxxxxxxxxxxxxxxx".
> 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
Going back to the original mail where you wrote:
check_gss_callback_principal: acceptor=nfs@xxxxxxxxxxxxxxxxxxxxxxxx,
principal=host@xxxxxxxxxxxxxxxxxxxxx
Where is this output on the client kernel or server kernel?
According to the gssd output. In the callback authentication
nfs@xxxxxxxxxxxxxxxxxxxxx is authenticating to
host@xxxxxxxxxxxxxxxxxxxxx. None of them match the
"check_gss_callback_principal" output. So I'm confused...
>
>
>>> 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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