Transferring NFSv4 nfs/ keys from KDC to client?
Wendy Lin
wendlin1974 at gmail.com
Wed Mar 19 19:04:44 EDT 2014
On 19 March 2014 23:36, steve <steve at steve-ss.com> wrote:
> On Wed, 2014-03-19 at 23:16 +0100, Wendy Lin wrote:
>> On 19 March 2014 14:11, steve <steve at steve-ss.com> wrote:
>> > On Wed, 2014-03-19 at 13:32 +0100, Wendy Lin wrote:
>> >> On 19 March 2014 09:55, steve <steve at steve-ss.com> wrote:
>> >> > On Wed, 2014-03-19 at 00:09 +0100, Wendy Lin wrote:
>> >> >> On 18 March 2014 23:54, steve <steve at steve-ss.com> wrote:
>> >> >> > On Tue, 2014-03-18 at 23:20 +0100, Wendy Lin wrote:
>> >> >> >> Asking here to make sure I got the mechanism right:
>> >> >> >>
>> >> >> >> I created the principal nfs/china.mytest.org at TEST1.MYTEST.ORG on the
>> >> >> >> KDC machine so that NFSv4 client china.mytest.org can mount a NFSv4
>> >> >> >> filesystem.
>> >> >> >>
>> >> >> >> How does the client china.mytest.org now get the keys?
>> >> >> >
>> >> >> > Hi
>> >> >> > It doesn't need to. rpc.gssd can use any of the following keys:
>> >> >> > <HOSTNAME>$@<REALM>
>> >> >> > root/<hostname>@<REALM>
>> >> >> > nfs/<hostname>@<REALM>
>> >> >> > host/<hostname>@<REALM>
>> >> >> > root/<anyname>@<REALM>
>> >> >> > nfs/<anyname>@<REALM>
>> >> >> > host/<anyname>@<REALM>
>> >> >> >
>> >> >> > Just make sure that your keytab has one of them. Usually it will already
>> >> >> > have the CHINA$ key, so you can mount using that. The nfs server keytab
>> >> >> > should have both the nfs servivce and machine keys.
>> >> >> >
>> >> >> > There are many misunderstandings about kerberized nfs:
>> >> >> > http://linuxcostablanca.blogspot.com.es/2012/02/nfsv4-myths-and-legends.html
>> >> >> > HTH
>> >> >> > Steve
>> >> >>
>> >> >> What I did is:
>> >> >> 1. Have kadmind running on the kdc
>> >> >> 2. Run kadmin on the client as user root. A principal root@<REALM> exists
>> >> >> 3. Use ktadd in kamin to download the keys for
>> >> >> nfs/<clienthostname>@<REALM> and host/<clienthostname>@<REALM> .
>> >> >>
>> >> >> Still it does not work here and the mount fails:
>> >> >> mount -t nfs4 test1.mytest.org:/ /mnt
>> >> >> mount.nfs4: access denied by server while mounting nexentapuzzle.nrubsig.org:/
>> >> >
>> >> > Tell it to use Kerberos:
>> >> > mount -t nfs4 test1.mytest.org:/ /mnt -osec=krb5
>> >> >>
>> >> >> gssd is running:
>> >> >> # ps -ef | fgrep gss
>> >> >> root 1403 1 0 Mar18 ? 00:00:00 /usr/sbin/rpc.svcgssd
>> >> >> root 1420 1 0 Mar18 ? 00:00:00 /usr/sbin/rpc.gssd
>> >> >>
>> >> >> I have not a clue what I am doing wrong. Please help.
>> >> >
>> >> > Tell it to use Kerberos:
>> >> > mount -t nfs4 test1.mytest.org:/ /mnt -osec=krb5
>> >> >
>> >> > If still nothing send the output of:
>> >> > klist -ke
>> >> > on both the client and the server?
>> >>
>> >> @(nfs|krb) server (hostname "test1.mytest.org"):
>> >> # klist -ke /etc/krb5.keytab
>> >> Keytab name: WRFILE:/etc/krb5.keytab
>> >> KVNO Principal
>> >> ---- --------------------------------------------------------------------------
>> >> 2 nfs/test1 at TEST1.MYTEST.ORG (DES cbc mode with CRC-32)
>> >> 2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (DES cbc mode with CRC-32)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >> 3 host/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 3 host/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 3 host/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 3 host/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 2 host/test1.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 2 host/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >> 2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 2 nfs/test1.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >> 2 nfs/china.mytest.org at TEST1.MYTEST.ORG (AES-256 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 nfs/china.mytest.org at TEST1.MYTEST.ORG (AES-128 CTS mode with
>> >> 96-bit SHA-1 HMAC)
>> >> 2 nfs/china.mytest.org at TEST1.MYTEST.ORG (Triple DES cbc mode with HMAC/sha1)
>> >> 2 nfs/china.mytest.org at TEST1.MYTEST.ORG (ArcFour with HMAC/md5)
>> >>
>> >> Why do I have duplicate entries in this output? Are they harmful?
>> >
>> > They represent the different encryption types. They're not harmful but
>> > as this is the server, there is no need for the client keys. You can
>> > tidy it up using e.g. ktutil.
>> >>
>> >>
>> >> @(nfs|krb) client (hostname "china.mytest.org"):
>> >> # klist -ke
>> >> Keytab name: FILE:/etc/krb5.keytab
>> >> klist: No such file or directory while starting keytab scan
>> >>
>> >> Client is my problem, how can I get the keys to it? ssh them over?
>> >
>> > Working on the kdc, create a keytab (as you did above) with the machine
>> > key of the client, CHINA$, If you use ktutil, something like:
>> > wkt /tmp/china.keytab
>> >
>> > Then simply copy it to the client using scp or (even easier and more
>> > secure) using a USB memory stick. Rename china.keytab to krb5.keytab and
>> > copy it 0600 to /etc
>> >
>> >>
>> >> >
>> >> > What does /etc/exports look like on the server?
>> >>
>> >> # cat /etc/exports
>> >> /nfsv4krbtest *(sec=krb5,rw,fsid=0
>> >
>> > Lose the fsid0. For now, replace the * with the IP of china
>> >
>> >> # uname -a
>> >> Linux test1.mytest.org 2.6.34.10-0.6-desktop #1 SMP PREEMPT 2011-12-13
>> >> 18:27:38 +0100 x86_64 x86_64 x86_64 GNU/Linux
>> >>
>> >> > Note that it is no longer recommended to export nfs4 as a fsid=0 pseudo
>> >> > root. Simply export it as we always have done nfs3.
>> >>
>> >> is this recommendation valid for the quite old 2.6.34.10-0.6-desktop
>> >> kernel in Suse 11.3?
>> >
>> > Dunno. Must it be nfs4 for anything in particular? Security perhaps?
>> > nfs3 works fine with kerberos.
>>
>> NFSv4 is better for going through a firewall and is less sensitive to
>> hacking attempts.
>>
>> But:
>> if I try to mount the share from the client I now see this:
>> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:03:42 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:03:43 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:03:43 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:03:43 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:03:44 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:03:44 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:03:44 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:04:29 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR:
>> prepare_krb5_rfc_cfx_buffer: not implemented
>> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: ERROR: failed serializing
>> krb5 context for kernel
>> Mar 19 23:04:30 test1 rpc.svcgssd[5154]: WARNING: handle_nullreq:
>> serialize_context_for_kernel failed
>>
> It doesn't like the encryption type. (On openSUSE 13.1 it's been fixed)
> Try:
> allow_weak_crypto = true
> permitted_enctypes = "des-cbc-crc arcfour-hmac des3-cbc-sha1
> aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96"
>
> to [libdefaults] in /etc/krb5.conf
I have this now for [libdefaults]:
---------------------------------------------------
[libdefaults]
# default_realm = EXAMPLE.COM
default_realm = TEST1.MYTEST.ORG
clockskew = 300
allow_weak_crypto = true
permitted_enctypes = "des-cbc-crc arcfour-hmac des3-cbc-sha1
aes128-cts-hmac-sha1-96 aes256-cts-hmac-sha1-96"
---------------------------------------------------
is this what you wished to suggest? Client has the same
permitted_enctypes, and I did a hard reboot of all machines.
Unfortunately it does not work. Neither does this change+mount with NFSv3 btw
>
>> Do you have a very, very bad English curse word which I can use to
>> swear at the machine? It doesn't have to be nice or politically
>> correct. Just very, very bad.
> Yes. Try, 'kerberos'. Shout it very loud as you start rpc.gssd!
Done
Coworker came by and questioned my sanity until I showed him my
problem. He suggested to tape off the parking lot in front of the
building and then throw the server the 14 stories down to the lot.
I wish for a bad curse word, one which is not kerberos, just common
English language
>> Oh, and I take any suggestions how to fix the 'rpc.svcgssd[5154]:
>> ERROR: prepare_krb5_rfc_cfx_buffer: not implemented' too.
> Above.
>>
>
> Do you have everything you need?
> pa aux | grep rpc
> on both server and client
yes
>> Wendy
> Good luck,
> Steve
>
>
>
Wendy
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