This request was evaluated by Red Hat Product Management for inclusion
in a Red Hat Enterprise Linux maintenance release. Product Management has 
requested further review of this request by Red Hat Engineering, for potential
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pls help to provide how to test, thanks.

Sure. The basic idea behind this patchset is to make it so that users use their own credentials to access the server. The idea is to make sure that when users access the server that the resulting accesses are done as those users and not with the credentials used originally on the mount.

Currently this is limited to krb5 auth, so to test...

First, you'll need a kerberized CIFS server. There's an example of how to set one up in RHTS under "kernel-tests/filesystems/cifs/krb5".

Once you set one up, you'll need 2 users set up on the client and server. UID/GIDs should be the same on both machines for the two users and they should have principals in the KDC.

The share exported by the server should be writable by both users.

The client should also have /etc/request-key.conf set up in accordance with the cifs.upcall manpage:

    create  cifs.spnego    * * /usr/sbin/cifs.upcall %k
    create  dns_resolver   * * /usr/sbin/cifs.upcall %k

...as root on the client, kinit as the first user:

    root@client# kinit user1
    Password for user1:

Then, mount the share from the server using krb5 auth and the "multiuser" mount option:

    root@client# mount //server.example.com/share /mnt/cifs -o sec=krb5,multiuser

Be sure to use the FQDN of the server. That will mount the server using the credentials in root's credcache.

Now, "su" to user2 and run kdestroy to delete the credential cache:

    user2@client$ kdestroy

Then try to access /mnt/cifs. It should fail with an EACCES error (Permission denied). This is because user2 has no credentials. Next, kinit as user2:

    user2@client$ kinit
    Password for user2:

Now, try to access /mnt/cifs. It should then work. You can then do any number of operations to make sure that this works as expected:

o Create a file in /mnt/cifs and it should be owned by "user2" (verify it on client and server).

o Go onto the server and create a file in the directory that's only readable by "user1". Try to have user2 read it. That should fail. Then try to have root read it, that should work (since root is using user1's credentials).

Contrast how this works with krb5 auth without the multiuser option. There, every access to the server is done using the same (mount) credentials. So creating files as "user2" in the test above will show files being created on the server as "user1".

Patch(es) available on kernel-2.6.32-112.el6

Jeff hi, 
I have run this case in reserved machine with RHEL6.1, and I also have an environment:

1. two machines: kdc.lijian.com and host.lijian.com using RHEL6.0
hostnames have been added to /etc/hosts

2. kerberos working rightly (tested by sserver/sclient in host.lijian)
  principals :
root
cifs/host.lijian.com@EXAMPLE

3. /etc/samba/smb.conf:
[global]
        workgroup = EXAMPLE
        use kerberos keydtab = yes
        realm = EXAMPLE.COM
        security = ads
        #security = user
        server signing = auto
        dedicated keytab file = /etc/krb5.keytab
        kerberos method = dedicated keytab
[export]
        path = /mnt/smb
        read only = no

4. messages in /var/log/samba/log.smbd:

[2011/03/25 21:16:54.483380,  0] libads/kerberos_verify.c:72(ads_dedicated_keytab_verify_ticket)
  krb5_rd_req failed (Permission denied)
[2011/03/25 21:16:54.484035,  1] smbd/sesssetup.c:332(reply_spnego_kerberos)
  Failed to verify incoming ticket with error NT_STATUS_LOGON_FAILURE!

5. mount command : (root$) mount.cifs //host.lijian.com/export /mnt -o sec=krb5
mount error(13): Permission denied
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)

6. klist
Ticket cache: FILE:/tmp/krb5cc_0
Default principal: root

Valid starting     Expires            Service principal
03/25/11 21:14:46  03/26/11 21:14:35  krbtgt/EXAMPLE.COM
03/25/11 21:16:24  03/26/11 21:14:35  cifs/host.lijian.com

(In reply to comment #12)

> 
> 4. messages in /var/log/samba/log.smbd:
> 
> [2011/03/25 21:16:54.483380,  0]
> libads/kerberos_verify.c:72(ads_dedicated_keytab_verify_ticket)
>   krb5_rd_req failed (Permission denied)
> [2011/03/25 21:16:54.484035,  1] smbd/sesssetup.c:332(reply_spnego_kerberos)
>   Failed to verify incoming ticket with error NT_STATUS_LOGON_FAILURE!
> 

Sounds like smbd doesn't have permission to access /etc/krb5.keytab.

(In reply to comment #14)

> 
> Sounds like smbd doesn't have permission to access /etc/krb5.keytab.
Yes, I think I didn't config smb with krb5 correctly, If you have built such environment, would you give me some tips?

hi jeff, I test with janfu's advertise (https://bugzilla.redhat.com/show_bug.cgi?id=669377#c10), find that:
 1. smb server and kdc stay together (running on a machine), mount.cifs success;
 2. they are running on two machine, mount.cifs fail.

kdc: dell-per910-02.lab.bos.redhat.com
kadmin.local:  list_principals 
K/M.REDHAT.COM
host/dell-per910-02.lab.bos.redhat.com.REDHAT.COM
host/ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com.REDHAT.COM
kadmin/admin.REDHAT.COM
kadmin/changepw.REDHAT.COM
kadmin/dell-per910-02.lab.bos.redhat.com.REDHAT.COM
krbtgt/LAB.BOS.REDHAT.COM.REDHAT.COM
user1.REDHAT.COM
user2.REDHAT.COM

====test commands on both machines with the same result.
$mount.cifs -o user=user1,uid=user1,sec=krb5 //dell-per910-02.lab.bos.redhat.com/public /mnt
#######success
$mount.cifs -o user=user1,uid=user1,sec=krb5 //ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com/public /mnt
mount error(13): Permission denied
Refer to the mount.cifs(8) manual page (e.g. man mount.cifs)


#dell-per910-02.lab.bos.redhat.com
$ klist
Ticket cache: FILE:/tmp/krb5cc_0
Default principal: user1.REDHAT.COM

Valid starting     Expires            Service principal
04/06/11 02:24:38  04/07/11 02:24:38  krbtgt/LAB.BOS.REDHAT.COM.REDHAT.COM
   ...........
04/06/11 02:25:52  04/07/11 02:24:38  host/dell-per910-02.lab.bos.redhat.com.REDHAT.COM
	renew until 04/06/11 02:24:38
04/06/11 02:37:23  04/07/11 02:24:38  host/ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com.REDHAT.COM
	renew until 04/06/11 02:24:38

#ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com
$ klist
Ticket cache: FILE:/tmp/krb5cc_0
Default principal: user1.REDHAT.COM

Valid starting     Expires            Service principal
04/06/11 02:27:34  04/07/11 02:27:34  krbtgt/LAB.BOS.REDHAT.COM.REDHAT.COM
	renew until 04/06/11 02:27:34
04/06/11 02:27:55  04/07/11 02:27:34  host/dell-per910-02.lab.bos.redhat.com.REDHAT.COM
	renew until 04/06/11 02:27:34
04/06/11 02:39:58  04/07/11 02:27:34  host/ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com.REDHAT.COM
	renew until 04/06/11 02:27:34

Hi Jeff, now I am confused of how to test and what to test. This is what I do:

server(smb/kdc): dell-per910-02.lab.bos.redhat.com
	test0:x:10000:10000::/home/test0:/bin/bash
	test1:x:10001:10001::/home/test1:/bin/bash

	smb export : /tmp/test
	[root@dell-per910-02 ~]# ls /tmp/test -la
	total 12
	drwxrwxrwx. 2 root  root  4096 Apr  6 04:04 .
	drwxrwxrwt. 4 root  root  4096 Apr  6 03:59 ..

	principals 
	test0 test1(keytab is hold by both machines)

client: ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com
	test0:x:10000:10000::/home/test0:/bin/bash
	test1:x:10001:10001::/home/test1:/bin/bash

	root$ kinit -k test0
	root$ mount.cifs -o sec=krb5,multiuser //dell-per910-02.lab.bos.redhat.com/public /mnt

	root$ ls -l /
	drwxrwxrwx.   2 root  root      0 Apr  6 04:04 mnt

	[root@ibm-x3655-03 ~]# cd /mnt; ls
	ls: reading directory .: Permission denied
 
	[root@ibm-x3655-03 mnt]# su test1
	[test1@ibm-x3655-03 mnt]$ pwd; ls
	/mnt
	ls: reading directory .: Permission denied

(In reply to comment #17)
> Hi Jeff, now I am confused of how to test and what to test. This is what I do:
> 
> server(smb/kdc): dell-per910-02.lab.bos.redhat.com
>  test0:x:10000:10000::/home/test0:/bin/bash
>  test1:x:10001:10001::/home/test1:/bin/bash
> 
>  smb export : /tmp/test
>  [root@dell-per910-02 ~]# ls /tmp/test -la
>  total 12
>  drwxrwxrwx. 2 root  root  4096 Apr  6 04:04 .
>  drwxrwxrwt. 4 root  root  4096 Apr  6 03:59 ..
> 
>  principals 
>  test0 test1(keytab is hold by both machines)
> 
> client: ibm-x3655-03.ovirt.rhts.eng.bos.redhat.com
>  test0:x:10000:10000::/home/test0:/bin/bash
>  test1:x:10001:10001::/home/test1:/bin/bash
> 
>  root$ kinit -k test0
>  root$ mount.cifs -o sec=krb5,multiuser
> //dell-per910-02.lab.bos.redhat.com/public /mnt
> 
>  root$ ls -l /
>  drwxrwxrwx.   2 root  root      0 Apr  6 04:04 mnt
> 

Nothing else under '/' ? That's odd...

>  [root@ibm-x3655-03 ~]# cd /mnt; ls
>  ls: reading directory .: Permission denied
> 

So, the prompt changed here. Does this mean that you switched users or machines?

>  [root@ibm-x3655-03 mnt]# su test1
>  [test1@ibm-x3655-03 mnt]$ pwd; ls
>  /mnt
>  ls: reading directory .: Permission denied

Does 'test1' have a krb5 ticket in his credcache here? IOW, did you kinit as test1?

Question is resolved, I am confused by SELINUX.

This bug is verified on this environment:

1. SERVER: [test0@intel-sugarbay-dh-01 test]$ uname -a
Linux intel-sugarbay-dh-01.rhts.eng.rdu.redhat.com 2.6.32-130.el6.x86_64 #1 SMP Tue Apr 5 19:58:31 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux

2. CLIENT: [test1@hp-xw6600-01 test]$ uname -a
Linux hp-xw6600-01.rhts.eng.bos.redhat.com 2.6.32-130.el6.x86_64 #1 SMP Tue Apr 5 19:58:31 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux

3. packages
samba-winbind-clients-3.5.6-86.el6.x86_64
samba-3.5.6-86.el6.x86_64
samba-common-3.5.6-86.el6.x86_64
krb5-devel-1.9-8.el6.x86_64
krb5-libs-1.9-8.el6.x86_64
krb5-workstation-1.9-8.el6.x86_64
krb5-server-1.9-8.el6.x86_64
cifs-utils-4.8.1-1.el6.x86_64

4. SELINUX is closed on both machines.
5. krb5.conf & smb.conf 
===krb5.conf
[logging]
 default = FILE:/var/log/krb5libs.log
 kdc = FILE:/var/log/krb5kdc.log
 admin_server = FILE:/var/log/kadmind.log

[libdefaults]
 default_realm = LAB.BOS.REDHAT.COM
 dns_lookup_realm = false
 dns_lookup_kdc = false
 ticket_lifetime = 24h
 renew_lifetime = 7d
 forwardable = true
 allow_weak_crypto = true

[realms]
 LAB.BOS.REDHAT.COM = {
  kdc = intel-sugarbay-dh-01.rhts.eng.rdu.redhat.com
  admin_server = intel-sugarbay-dh-01.rhts.eng.rdu.redhat.com
 }

[domain_realm]
 .lab.bos.redhat.com = LAB.BOS.REDHAT.COM
 lab.bos.redhat.com = LAB.BOS.REDHAT.COM
======smb.conf
[global]
        workgroup = EXAMPLE
        realm =LAB.BOS.REDHAT.COM
        security = ads
        server signing = auto
        kerberos method = system keytab
[public]
        path = /tmp/test
        read only = no
        writable = yes
6. principals on kdc and users on both machins
======
kadmin.local:  list_principals 
K/M.REDHAT.COM
host/hp-xw6600-01.rhts.eng.bos.redhat.com.REDHAT.COM
host/intel-sugarbay-dh-01.rhts.eng.rdu.redhat.com.REDHAT.COM
kadmin/admin.REDHAT.COM
kadmin/changepw.REDHAT.COM
kadmin/intel-sugarbay-dh-01.rhts.eng.rdu.redhat.com.REDHAT.COM
krbtgt/LAB.BOS.REDHAT.COM.REDHAT.COM
test0.REDHAT.COM
test1.REDHAT.COM
======
test0:x:10000:10000::/home/test0:/bin/bash
test1:x:10001:10001::/home/test1:/bin/bash

test steps:
1. prepare a directory exported on SERVER
[root@intel-sugarbay-dh-01 test]# ls -la /mnt/test
total 4
drwxrwxrwx. 2 root root    0 Apr 11 01:59 .
drwxr-xr-x. 6 root root 4096 Apr 10 23:57 ..

2. mount on CLIENT
[root@hp-xw6600-01 mnt]# kinit -k test0
[root@hp-xw6600-01 mnt]# mount.cifs //intel-sugarbay-dh-01.rhts.eng.rdu.redhat.com/public /mnt/test -o sec=krb5,multiuser

3. create a file on CLIENT and check on SERVER
[root@hp-xw6600-01 mnt]# echo "hello from root(test0)" > test/test0
======CHANGE MACHINE
[root@intel-sugarbay-dh-01 test]# ls -l
total 4
-rw-r--r--. 1 test0 test0 23 Apr 11 02:02 test0
[root@intel-sugarbay-dh-01 test]# cat test0
hello from root(test0)

4. change to test1 on CLIENT and do sth without any pricipals
[test1@hp-xw6600-01 mnt]$ kdestroy
[test1@hp-xw6600-01 mnt]$ ls test
ls: cannot access test: Permission denied

5. get principal test1 on CLIENT and create a file and check on SERVER
[test1@hp-xw6600-01 mnt]$ kinit -k test1
[test1@hp-xw6600-01 mnt]$ echo "hello from test1" >> test/test1
======CHANGE MACHINE
[root@intel-sugarbay-dh-01 test]# ls -la
total 16
drwxrwxrwx. 2 root  root  4096 Apr 11 02:05 .
drwxrwxrwt. 4 root  root  4096 Apr 10 23:56 ..
-rw-r--r--. 1 test0 test0   23 Apr 11 02:02 test0
-rw-r--r--. 1 test1 test1   17 Apr 11 02:05 test1
[root@intel-sugarbay-dh-01 test]# cat test1 
hello from test1

Another test is performed: 
1. 
[root@intel-sugarbay-dh-01 test]# echo "only test0" > onlytest0
[root@intel-sugarbay-dh-01 test]# chown test0:test0 onlytest0 
[root@intel-sugarbay-dh-01 test]# chmod 600 onlytest0 
[root@intel-sugarbay-dh-01 test]# ls -l
total 12
-rw-------. 1 test0 test0 11 Apr 11 02:08 onlytest0
-rw-r--r--. 1 test0 test0 23 Apr 11 02:02 test0
-rw-r--r--. 1 test1 test1 17 Apr 11 02:05 test1
========CHANGE MACHINE
[test1@hp-xw6600-01 test]$ cat onlytest0 
cat: onlytest0: Permission denied

2. mount without multiuser
[root@hp-xw6600-01 mnt]# mount.cifs //$SERVER/public /mnt/test -o sec=krb5
[test1@hp-xw6600-01 test]$ echo "hello from test1 without multiuser" > test1withoutmultiuser
bash: test1withoutmultiuser: Permission denied
=======CHANGE MACHINE
[root@intel-sugarbay-dh-01 test]# ls -la
total 20
drwxrwxrwx. 2 root  root  4096 Apr 11 02:13 .
drwxrwxrwt. 4 root  root  4096 Apr 10 23:56 ..
-rw-------. 1 test0 test0   11 Apr 11 02:08 onlytest0
-rw-r--r--. 1 test0 test0    0 Apr 11 02:13 test
-rw-r--r--. 1 test0 test0   23 Apr 11 02:02 test0
-rw-r--r--. 1 test1 test1   17 Apr 11 02:05 test1
-rw-r--r--. 1 test0 test0    0 Apr 11 02:12 test1withoutmultiuser

Ok, so I take it this is resolved then?

It is correct that if you want to export data via samba with selinux enabled then you need to label the data correctly. See the samba_selinux(8) manpage for info on how to do this.

Yes, I think the result is correct according to comment 0.
But there is still one problem:
  When kerberos'kdc and samba's server is NOT running on the same machine, mount.cifs will fail, just as comment 16 said.

(In reply to comment #23)
> Ok, so I take it this is resolved then?
> 
> It is correct that if you want to export data via samba with selinux enabled
> then you need to label the data correctly. See the samba_selinux(8) manpage for
> info on how to do this.

I'm not sure why that would be, it sounds like maybe you had something misconfigured in that setup? It's a little unclear from the description. Either way, I don't think that's an issue with the client.

An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.

http://rhn.redhat.com/errata/RHSA-2011-0542.html