[Cialug] {External} Re: Rhel 7 Selinux settings for Root user

Wed Aug 16 17:03:03 UTC 2017

Based on the error, looks as if the SELinux context issue is with /usr/bin/bash.  

Look at the bash command on the system
# which bash 
Check the inode of /bin/bash vs. /usr/bin/bash  - inode should be the same 
# ls -li /bin/bash
# ls -li /usr/bin/bash 
Then check the SELinux context for each  
# ls -lZ /usr/bin/bash
# ls -lZ /bin/bash 

On a Oracle Linux 7 system this is the SELinux context I see for bash 
# ls -lZ /usr/bin/bash
-rwxr-xr-x. root root system_u:object_r:shell_exec_t:s0 /usr/bin/bash

The error indicates on your systems seems to indicate that /usr/bin/bash has the following SELinux context:
sysadm_u:sysadm_r:sysadm_t:s0 	rather than 	system_u:object_r:shell_exec_t:s0

You mentioned running restorecon on / but not with the -R (recursive) option, so try the following and then check the SELinux contect again. 
# restorecon  -R -v /bin/

Chris H. 

-----Original Message-----
From: Cialug [mailto:cialug-bounces at cialug.org] On Behalf Of Kelly Slaugh
Sent: Wednesday, August 16, 2017 11:06 AM
To: 'Central Iowa Linux Users Group'
Subject: Re: [Cialug] {External} Re: Rhel 7 Selinux settings for Root user

[This is an external email. Be cautious with links, attachments and responses.]

**********************************************************************
Well as I expected this is a SELinux problem with invalid contexts for yum.

Looking at log file audit.log I can see that there is an SELINUX_ERR being reported for /bin/yum when I attempt to run the command on the console logged in as root.

Restorecon has been ran on / however no positive results.

The audit.log show this...

# ausearch -a 20311

----

time->Wed Aug 16 10:46:13 2017

type=PATH msg=audit(1502898373.250:20311): item=0 name="/bin/yum" inode=91063 dev=fd:00 mode=0100755 ouid=0 ogid=0 rdev=00:00 obj=system_u:object_r:rpm_exec_t:s0 objtype=NORMAL

type=CWD msg=audit(1502898373.250:20311):  cwd="/root"

type=SYSCALL msg=audit(1502898373.250:20311): arch=c000003e syscall=59 success=no exit=-13 a0=13f2090 a1=13cafc0 a2=13c6dd0 a3=7ffef18bdfb0 items=1 ppid=5835 pid=5853 auid=0 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=tty1 ses=33 comm="bash" exe="/usr/bin/bash" subj=sysadm_u:sysadm_r:sysadm_t:s0-s0:c0.c1023 key=(null)

type=SELINUX_ERR msg=audit(1502898373.250:20311): op=security_compute_sid invalid_context=sysadm_u:system_r:rpm_t:s0-s0:c0.c1023 scontext=sysadm_u:sysadm_r:sysadm_t:s0-s0:c0.c1023 tcontext=system_u:object_r:rpm_exec_t:s0 tclass=process

Any ideas?

Everything is working for me on the system, I'm not going to use root on the console to run commands and I can run the yum command if I need to by first calling python so this is not like the system is not working. I'm more curious on how I can fix SELinux to allow the context or manipulate SELinux to set the correct permissions on the system.

I was able to fix a couple of issues that turned up for some other software on the system by looking in the /var/log/messages & audit.log files. Ran sealer for a few items that popped up when searching messages for "SELinux is preventing" @ChrisHasler thanks for that advice.

-----Original Message-----

From: Cialug [mailto:cialug-bounces at cialug.org] On Behalf Of Hasler, Chris

Sent: Wednesday, August 16, 2017 9:36 AM

To: 'Central Iowa Linux Users Group' <cialug at cialug.org>

Subject: Re: [Cialug] {External} Re: Rhel 7 Selinux settings for Root user

Seems it is a SELinux context issue.

Running the following to see if anything helpful is in the logs.

# grep "SELinux is preventing" /var/log/messages # grep "denied" /var/log/audit/audit.log

Check the context on the yum and python commands # ls -lZ /bin/yum # ls -lZ /usr/bin/python*

Sometimes I've seen this SELinux context issue with user home directory files that have been copied from another server/location.   Since you say the issue is when the root user logs in try restoring the context setting on the root users home subdirectory

# restorecon -R -v /root

Chris H.

-----Original Message-----

From: Cialug [mailto:cialug-bounces at cialug.org] On Behalf Of Kelly Slaugh

Sent: Wednesday, August 16, 2017 8:43 AM

To: 'Central Iowa Linux Users Group'

Subject: Re: [Cialug] {External} Re: Rhel 7 Selinux settings for Root user

[This is an external email. Be cautious with links, attachments and responses.]

**********************************************************************

Thanks for your suggestions. I wanted to make the situation a little clearer so I'm not using my phone to type the email.

Root user is part of the sysadm_u context not unconfined_u, however, even if I add root to unconfined_u the situation with running any local scripts fails. The problem isn't only with the yum command; that was just one example of many.

#semanage login -l

Login Name              SELinux User

__default__             unconfined_u

Root                    sysadm_u

System_u                system_u

What I did find out is that if I run the full path of the command yum works.

#/usr/bin/python /bin/yum check-update"/

The situation is ONLY when logging onto the RHEL 7.3 server through a console as root, if I sudo up to root or log in with a different user & su as root the command "#yum check-update" works. If I'm logged in as root through the console and try to run commands that run scripts I get errors like these.

# yum check-update

# -bash: /bin/yum: /usr/bin/python: bad interpreter: Permission denied

Any ideas?

Thanks,

-----Original Message-----

From: Cialug [mailto:cialug-bounces at cialug.org] On Behalf Of Zachary Kotlarek

Sent: Tuesday, August 15, 2017 1:29 PM

To: Central Iowa Linux Users Group <cialug at cialug.org>

Subject: {External} Re: [Cialug] Rhel 7 Selinux settings for Root user

On 15 Aug 2017, at 7:27, kslaugh19 wrote:

> In Rhel 7, we continue to receive permission denied when logged in as

> Root on a console with selinux enforced.

> If I run the yum command as Root, not sudoing as Root, I get a python

> error. If I run the same yum command but first call the program

> python, yum works. Any ideas on what sebool needs enabled so that root

> can run scripts or programs without having to call the program first?

> Setting selinux as permissive works but not an option.

> Any ideas?

> I've ran the command setsebool and tried to locate any sebool setting

> and toggled quite a bit without any luck.

There are lots of fiddly bits that could be broken, but I’d start with the broadest possibilities:

What context do you have in the root shell (or whatever you’re launching `yum` from)? On RHEL the default for root is “unconfined_u”, which should allow almost anything. Use `id -Z` to see your current context or `semanage login -l` to list all user contexts.

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/SELinux_Users_and_Administrators_Guide/sect-Security-Enhanced_Linux-Targeted_Policy-Confined_and_Unconfined_Users.html

Another thing to check is the on-disk labels; context transitions for executables depend on accurate disk labeling, but the labels are dependent on the policy as compiled so it’s possible for the disk to get out-of-sync with policy. There are utilities like `restorecon` and `fixfiles` for small-scale relabeling; the recommended procedure for global relabeling is to mark the filesystem and let it happen as part of the boot process:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/5/html/Deployment_Guide/sec-sel-fsrelabel.html

        Zach

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