1729756 – rpc-gssd cannot create security context if selinux is enforcing

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Bug 1729756 - rpc-gssd cannot create security context if selinux is enforcing

Summary: rpc-gssd cannot create security context if selinux is enforcing

Keywords:
Status:	CLOSED WONTFIX
Alias:	None
Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	nfs-utils
Sub Component:
Version:	7.6
Hardware:	x86_64
OS:	Linux
Priority:	unspecified
Severity:	high
Target Milestone:	rc
Target Release:	---
Assignee:	Steve Dickson
QA Contact:	Yongcheng Yang
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+	depends on / blocked

Reported:	2019-07-14 09:44 UTC by Lukas Hejtmanek
Modified:	2021-03-15 07:37 UTC (History)
CC List:	3 users (show)
Fixed In Version:
Doc Type:	If docs needed, set a value
Doc Text:
Clone Of:
Environment:
Last Closed:	2021-03-15 07:37:29 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)

Description Lukas Hejtmanek 2019-07-14 09:44:00 UTC

Description of problem:
If selinux is enforcing and NFSv4 client uses KRB5 security and ssh is configured with GSSAPI, rpc.gssd cannot create security context:
rpc.gssd[75903]: ERROR: GSS-API: error in gss_acquire_cred(): GSS_S_FAILURE (Unspecified GSS failure.  Minor code may provide more information) - (0x9ae73ac4)
rpc.gssd[75903]: WARNING: Failed while limiting krb5 encryption types for user with uid 0
rpc.gssd[75903]: WARNING: Failed to create machine krb5context with cred cache FILE:/tmp/krb5ccmachine_ICS.MUNI.CZ for server storage-brno3-cerit.metacentrum.cz

I believe, this is due to:
type=AVC msg=audit(1563060569.732:5664): avc:  denied  { unlink } for  pid=46136 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=1

this is the file:
ls -Z /tmp/krb5cc_0
-rw-------. root root system_u:object_r:gssd_tmp_t:s0  /tmp/krb5cc_0

if I set selinux to permissive, everything works.

Version-Release number of selected component (if applicable):
everything from 7.6 RHEL up to date.

Comment 2 Yongcheng Yang 2019-07-15 03:36:19 UTC

(In reply to Lukas Hejtmanek from comment #0)
Hey Lukas,

I didn't see this AVC during my krb5/NFS testings.

> this is the file:
> ls -Z /tmp/krb5cc_0
> -rw-------. root root system_u:object_r:gssd_tmp_t:s0  /tmp/krb5cc_0

It's different from my side:

[root]# ls -Z /tmp/krb5cc_0
-rw-------. root root unconfined_u:object_r:user_tmp_t:s0 /tmp/krb5cc_0
[root]# getenforce
Enforcing

> 
> Version-Release number of selected component (if applicable):
> everything from 7.6 RHEL up to date.

By the way, have you tried any version before 7.6? Does it work as expected?

Comment 3 Lukas Hejtmanek 2019-07-15 12:41:39 UTC

Did you try to mount any kerberize NFS volume while there is that -rw-------. root root unconfined_u:object_r:user_tmp_t:s0 /tmp/krb5cc_0 file?

I did not test any previous version.

Comment 4 Yongcheng Yang 2019-07-19 07:43:58 UTC

Okay, after mounting as krb5, the "security context" is updated to "system_u:object_r:gssd_tmp_t:s0".

But I still didn't encounter the failure of comment #0:
-----------------------------------------------------
[root ~]# mount -t nfs4 -o sec=krb5 $HOSTNAME:/ /mnt/
[root ~]# nfsstat -m
/mnt from rhel-7.7.redhat.com:/
 Flags: rw,relatime,vers=4.1,rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=krb5,clientaddr=10.10.10.10,local_lock=none,addr=10.10.10.10

[root ~]# ls -Z /tmp/krb5cc_0
-rw-------. root root system_u:object_r:gssd_tmp_t:s0  /tmp/krb5cc_0
                      ^^^^^^^^^
[root ~]# grep gssd /var/log/messages | egrep -i "err|warn"
[root ~]# grep denied /var/log/audit/audit.log 
[root ~]#

Comment 5 Lukas Hejtmanek 2019-07-22 23:42:09 UTC

[root@ursa ~]# sestatus 
SELinux status:                 enabled
SELinuxfs mount:                /sys/fs/selinux
SELinux root directory:         /etc/selinux
Loaded policy name:             targeted
Current mode:                   enforcing
Mode from config file:          enforcing
Policy MLS status:              enabled
Policy deny_unknown status:     allowed
Max kernel policy version:      31
[root@ursa ~]#

[root@ursa ~]# mount -t nfs4 -o sec=krb5 storage-brno1-cerit.metacentrum.cz:/ /mnt/storage-brno1-cerit
mount.nfs4: access denied by server while mounting storage-brno1-cerit.metacentrum.cz:/
[root@ursa ~]# ls -Z /tmp/krb5cc_0
-rw-------. root root system_u:object_r:tmp_t:s0       /tmp/krb5cc_0
[root@ursa ~]# 

[root@ursa ~]# date
Tue Jul 23 01:35:50 CEST 2019
[root@ursa ~]# grep gssd /var/log/messages | egrep -i "err|warn"
[root@ursa ~]# grep denied /var/log/audit/audit.log
type=AVC msg=audit(1563838547.187:235): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.189:236): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.191:237): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.193:238): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.196:239): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.198:240): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.252:241): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.254:242): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.256:243): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.257:244): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.270:245): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0
type=AVC msg=audit(1563838547.272:246): avc:  denied  { unlink } for  pid=45595 comm="rpc.gssd" name="krb5cc_0" dev="md126p4" ino=67160166 scontext=system_u:system_r:gssd_t:s0 tcontext=system_u:object_r:tmp_t:s0 tclass=file permissive=0



[root@ursa ~]# rm /tmp/krb5cc_0
rm: remove regular file ‘/tmp/krb5cc_0’? y
[root@ursa ~]# mount -t nfs4 -o sec=krb5 storage-brno1-cerit.metacentrum.cz:/ /mnt/storage-brno1-cerit
[root@ursa ~]# 

[root@ursa ~]# ls -Z /tmp/krb5cc_0
-rw-------. root root system_u:object_r:gssd_tmp_t:s0  /tmp/krb5cc_0
[root@ursa ~]#

Comment 6 Trent Anderson 2020-08-20 23:40:16 UTC

I'm running RHEL 7.8 and on all machines I get:

[tanderson@test-sl01 ~]$ ls -Z /tmp/krb5cc_0
-rw-------. root root system_u:object_r:gssd_tmp_t:s0  /tmp/krb5cc_0

But I'm only getting there avc: denied on 2 out of 6 machines and those 2 are luckilly test machines.  Everything is managed by puppet and they are machines that were built as 7.8.

Comment 9 RHEL Program Management 2021-03-15 07:37:29 UTC

After evaluating this issue, there are no plans to address it further or fix it in an upcoming release.  Therefore, it is being closed.  If plans change such that this issue will be fixed in an upcoming release, then the bug can be reopened.

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