Bug 1951093

(In reply to Jacob Shivers from comment #0)

Hi Jacob,

Could you more explain step by step how reproduce this bug? 

> Steps to Reproduce:

Also could you sent link of nfs-utils rpm? It seem's like links in another bugzilla already aren't valid.

> 1. Install nfs-utils from BZ1868087
> 2. Create user $HOME/.k5identity file for test user.
> 3. Mount then access Kerberized NFS share as user leveraging DEFCKTNAME

(In reply to Patrik Koncity from comment #3)
> (In reply to Jacob Shivers from comment #0)
> 
> Hi Jacob,
> 
> Could you more explain step by step how reproduce this bug? 
> 

Certainly

> > Steps to Reproduce:
> 
> Also could you sent link of nfs-utils rpm? It seem's like links in another
> bugzilla already aren't valid.
> 
> > 1. Install nfs-utils from BZ1868087
> > 2. Create user $HOME/.k5identity file for test user.
> > 3. Mount then access Kerberized NFS share as user leveraging DEFCKTNAME

The original test rpms have expired, but I have original copies saved at http://file.rdu.redhat.com/~jshivers/test_rpms/bugzillas/1868087/. Updated test RPMs can also be found at https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=36725096 for the 8.5 candidate test.

This setup will require a Kerberized environment with a NFS server configured to support Kerberos and a NFS client joined to the same Kerberos realm. c#18 in BZ1868087 goes over the client configuration setup, but the existing infrastructure may be what requires further explanation.

QA for fs has an environment that was used for testing. If this environment can not be accessed, I can certainly set something up that can be accessed for testing and review.

I have an older document, that needs updating including for RHEL8, here ( http://file.rdu.redhat.com/~jshivers/configs/ipa-install_training ) to go over setting up an IPA environment for Kerberzied remote filesystems. If anything more specific is needed or further clarity requested, please inform me.

As https://bugzilla.redhat.com/show_bug.cgi?id=1868087#c33
---
type=AVC msg=audit(1620890462.356:230): avc:  denied  { search } for  pid=20665 comm="rpc.gssd" name="testUser" dev="dm-0" ino=67330672 scontext=system_u:system_r:gssd_t:s0 tcontext=unconfined_u:object_r:user_home_dir_t:s0 tclass=dir permissive=0

If this is the warning that going to be fixed, I can verify the new package with our nfs testcase.

(In reply to Yongcheng Yang from comment #5)
> As https://bugzilla.redhat.com/show_bug.cgi?id=1868087#c33
> ---
> type=AVC msg=audit(1620890462.356:230): avc:  denied  { search } for 
> pid=20665 comm="rpc.gssd" name="testUser" dev="dm-0" ino=67330672
> scontext=system_u:system_r:gssd_t:s0
> tcontext=unconfined_u:object_r:user_home_dir_t:s0 tclass=dir permissive=0
> 
> If this is the warning that going to be fixed, I can verify the new package
> with our nfs testcase.

It should be that error and an open/read error for .k5identity like seen in https://bugzilla.redhat.com/show_bug.cgi?id=1868087#c18

commit 05bacfed6df3f336c50326c7c6f4c3677c7f7d70
Author: Jacob Shivers <jshivers>
Date:   Mon Mar 15 09:22:57 2021 -0400

    gssd: Add options to rpc.gssd to allow for the use of $HOME/.k5identity file

(In reply to Steve Dickson from comment #7)
> commit 05bacfed6df3f336c50326c7c6f4c3677c7f7d70
> Author: Jacob Shivers <jshivers>
> Date:   Mon Mar 15 09:22:57 2021 -0400
> 
>     gssd: Add options to rpc.gssd to allow for the use of $HOME/.k5identity
> file

Hi SteveD, JFYI that this bug is for selinux-policy (NOT nfs-utils).

Above patch you mentioned has already been imported as https://bugzilla.redhat.com/show_bug.cgi?id=1868087#c22

(In reply to Yongcheng Yang from comment #8)
> (In reply to Steve Dickson from comment #7)
> > commit 05bacfed6df3f336c50326c7c6f4c3677c7f7d70
> > Author: Jacob Shivers <jshivers>
> > Date:   Mon Mar 15 09:22:57 2021 -0400
> > 
> >     gssd: Add options to rpc.gssd to allow for the use of $HOME/.k5identity
> > file
> 
> Hi SteveD, JFYI that this bug is for selinux-policy (NOT nfs-utils).
> 
> Above patch you mentioned has already been imported as
> https://bugzilla.redhat.com/show_bug.cgi?id=1868087#c22

Thanks! I like bugs like this!!! :-)

Hi Jacob,

So I made build with possible fix. I label $HOME/.k5identity file as other kerberos files in $HOME and also allow additional permission, which I saw in c#18 BZ1868087 in AVC's.

Please, can you try this build if everything work properly?

Build: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=37215666

Thanks,
Patrik

(In reply to Patrik Koncity from comment #11)
> Hi Jacob,

Hello Patrik,

> 
> So I made build with possible fix. I label $HOME/.k5identity file as other
> kerberos files in $HOME and also allow additional permission, which I saw in
> c#18 BZ1868087 in AVC's.
> 
> Please, can you try this build if everything work properly?

I have tested the build and can confirm that it works properly by allowing
rpc.gssd the necessary access to $HOME/.k5identity.

Testing below. I will note that I had already done a previous chcon for
.k5identity so this is why the label is already different.


# wget 'http://brew-task-repos.usersys.redhat.com/repos/scratch/pkoncity/selinux-policy/3.14.3/67.el8.1951093/selinux-policy-3.14.3-67.el8.1951093-scratch.repo' -P /etc/yum.repos.d/
# dnf update selinux-policy
# systemctl reboot

# grep -v '#' /etc/nfs.conf
[general]
[exportfs]
[gssd]
verbosity=3
use-gss-proxy=1
set-home=0
[lockd]
[mountd]
[nfsdcld]
[nfsdcltrack]
[nfsd]
[statd]
[sm-notify]

# strace -fvttTyyx -s 4096 -o /tmp/rpc.gssd_with_H-rhel8.strace -p $(pidof rpc.gssd) &
# getenforce 
Enforcing

# mount ad-nfs-server.example.net:/secure /mnt/ -o sec=krb5
# su - dean

$ cat .k5identity 
jeff        host=win2k16-*.example.net      service=nfs
troy        host=samba-701.example.net
dean        host=*.example.net      service=nfs

$ ls -lZ .k5identity
-rw-r--r--. 1 dean domain users unconfined_u:object_r:krb5_home_t:s0 179 Feb  7 15:15 .k5identity


$ klist
klist: No credentials cache found (filename: /tmp/krb5cc_602001124)

$ touch /mnt/gssd_with_H-rhel8-$(date +%F).txt
strace: Process 1739 attached

$ ll /mnt/gssd_with_H-rhel8-$(date +%F).txt
-rw-r--r--. 1 dean root 0 Jun  3 11:45 /mnt/gssd_with_H-rhel8-2021-06-03.txt

$ klist
Ticket cache: FILE:/tmp/krb5cc_602001124
Default principal: dean

Valid starting       Expires              Service principal
06/03/2021 11:45:19  06/03/2021 12:00:19  krbtgt/EXAMPLE.NET
06/03/2021 11:45:19  06/03/2021 12:00:19  nfs/ad-nfs-server.example.net

$ logout

# pkill strace

# ausearch -m avc -i -c rpc.gssd -ts today
<no matches>

# egrep 'geteuid|open.*k5identity' /tmp/rpc.gssd_with_H-rhel8.strace | tail -2
1739  11:45:18.317400 geteuid()         = 602001124 <0.000015>
1739  11:45:18.317527 openat(AT_FDCWD, "/home/dean/.k5identity", O_RDONLY) = 14</home/dean/.k5identity> <0.000180>


Thanks for the test package.

Hi,

that's great. So I made PR and after merging it we will deliver this fix to selinux-policy on RHEL-8.5.0.


PR: https://github.com/fedora-selinux/selinux-policy/pull/767

Thanks, 
Patrik

Commit to backport:
commit 434cb2a6cb4092f49f4bba0f045f28c3660d97d1 (HEAD -> rawhide, upstream/rawhide)
Author: Patrik Koncity <pkoncity>
Date:   Mon May 31 15:15:33 2021 +0200

    Label /.k5identity file allow read of this file to rpc.gssd

    Label kerberos file $HOME/.k5identity as krb5_home_t, which
    is default label for kerberos files in HOME. Also add
    filetransition for this specific object to
    kerberos_filetrans_admin_home_content() and
    kerberos_filetrans_home_content(). And also allow
    read this HOME kerberos files for rpc.gssd. Rpc.gssd is
    daemon, which provide strong security for RPC-based protocols
    such as NFS.

    Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1951093

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (selinux-policy bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:4420