Bug 1201054

Summary: [SELinux] [Nagios] SELinux blocks Nagios/NRPE plugins which use sudo - RHEL-7.2
Product: Red Hat Enterprise Linux 7 Reporter: James Ralston <ralston>
Component: selinux-policyAssignee: Miroslav Grepl <mgrepl>
Status: CLOSED ERRATA QA Contact: Milos Malik <mmalik>
Severity: medium Docs Contact:
Priority: high    
Version: 7.1CC: adam.winberg, lvrabec, mgrepl, mmalik, plautrba, pprakash, pvrabec, sgraf, skremen, ssekidde, tjeyasin
Target Milestone: rcKeywords: ZStream
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: selinux-policy-3.13.1-26.el7 Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
: 1230299 (view as bug list) Environment:
Last Closed: 2015-11-19 10:28:44 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 1169221, 1212796, 1230299    

Description James Ralston 2015-03-11 23:46:51 UTC 
Description of problem:

Some Nagios plugins, when run remotely via nrpe, need to be run with sudo in order function properly. But SELinux policy is preventing sudo from executing.

Version-Release number of selected component (if applicable):

selinux-policy-targeted-3.13.1-23.el7.noarch

How reproducible:

Call a Nagios plugin remotely via sudo. E.g., use this nrpe definition:

command[check_disk]=sudo /usr/lib64/nagios/plugins/check_disk $ARG1$

$ ls -Z /usr/lib64/nagios/plugins/check_disk 
-rwxr-xr-x. root root system_u:object_r:nagios_checkdisk_plugin_exec_t:s0 /usr/lib64/nagios/plugins/check_disk*

Despite the check_disk plugin having the correct file context, if SELinux is in enforcing mode, when NRPE calls the plugin remotely, it will fail:

$ check_nrpe -H host.example.org -p 5666 -c check_disk -a "-e -E -w 10% -c 5% -p /"
NRPE: Unable to read output

But if SELinux is in non-enforcing mode, the plugin will succeed:

$ check_nrpe -H host.example.org -p 5666 -c check_disk -a "-e -E -w 10% -c 5% -p /"
DISK OK| /=1712MB;14398;15198;0;15998

Additional info:

We had this exact same problem with RHEL6 (bug 917157), although the underlying causes appear to be different in this case.

The denial that is causing the problem is being hidden with dontaudit, so I had to disable dontaudit temporarily to get at it. Here are all of the denials that are being hidden by dontaudit (in non-enforcing mode):

----
time->Wed Mar 11 19:35:01 2015
type=SYSCALL msg=audit(1426116901.940:13713): arch=c000003e syscall=41 success=yes exit=7 a0=10 a1=3 a2=9 a3=7fff45594cb0 items=0 ppid=3435 pid=3436 auid=4294967295 uid=994 gid=993 euid=0 suid=0 fsuid=0 egid=993 sgid=993 fsgid=993 tty=(none) ses=4294967295 comm="sudo" exe="/usr/bin/sudo" subj=system_u:system_r:nrpe_t:s0 key=(null)
type=AVC msg=audit(1426116901.940:13713): avc:  denied  { create } for  pid=3436 comm="sudo" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nrpe_t:s0 tclass=netlink_audit_socket
----
time->Wed Mar 11 19:35:01 2015
type=SYSCALL msg=audit(1426116901.940:13714): arch=c000003e syscall=44 success=yes exit=272 a0=7 a1=7fff4558a490 a2=110 a3=0 items=0 ppid=3435 pid=3436 auid=4294967295 uid=994 gid=993 euid=0 suid=0 fsuid=0 egid=993 sgid=993 fsgid=993 tty=(none) ses=4294967295 comm="sudo" exe="/usr/bin/sudo" subj=system_u:system_r:nrpe_t:s0 key=(null)
type=AVC msg=audit(1426116901.940:13714): avc:  denied  { audit_write } for  pid=3436 comm="sudo" capability=29  scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nrpe_t:s0 tclass=capability
type=AVC msg=audit(1426116901.940:13714): avc:  denied  { nlmsg_relay } for  pid=3436 comm="sudo" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nrpe_t:s0 tclass=netlink_audit_socket
type=AVC msg=audit(1426116901.940:13714): avc:  denied  { write } for  pid=3436 comm="sudo" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nrpe_t:s0 tclass=netlink_audit_socket
----
time->Wed Mar 11 19:35:01 2015
type=SYSCALL msg=audit(1426116901.940:13716): arch=c000003e syscall=45 success=yes exit=36 a0=7 a1=7fff4558c7c0 a2=231c a3=42 items=0 ppid=3435 pid=3436 auid=4294967295 uid=994 gid=993 euid=0 suid=0 fsuid=0 egid=993 sgid=993 fsgid=993 tty=(none) ses=4294967295 comm="sudo" exe="/usr/bin/sudo" subj=system_u:system_r:nrpe_t:s0 key=(null)
type=AVC msg=audit(1426116901.940:13716): avc:  denied  { read } for  pid=3436 comm="sudo" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nrpe_t:s0 tclass=netlink_audit_socket
----
time->Wed Mar 11 19:35:01 2015
type=SYSCALL msg=audit(1426116901.941:13719): arch=c000003e syscall=160 success=yes exit=0 a0=6 a1=7fff45594d40 a2=0 a3=40 items=0 ppid=3435 pid=3436 auid=4294967295 uid=0 gid=993 euid=0 suid=0 fsuid=0 egid=993 sgid=993 fsgid=993 tty=(none) ses=4294967295 comm="sudo" exe="/usr/bin/sudo" subj=system_u:system_r:nrpe_t:s0 key=(null)
type=AVC msg=audit(1426116901.941:13719): avc:  denied  { sys_resource } for  pid=3436 comm="sudo" capability=24  scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nrpe_t:s0 tclass=capability
----
time->Wed Mar 11 19:35:01 2015
type=SYSCALL msg=audit(1426116901.941:13720): arch=c000003e syscall=59 success=yes exit=0 a0=7fd4cdce68f8 a1=7fd4cdcdeb28 a2=7fd4cdce6450 a3=9 items=0 ppid=3436 pid=3437 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="check_disk" exe="/usr/lib64/nagios/plugins/check_disk" subj=system_u:system_r:nagios_checkdisk_plugin_t:s0 key=(null)
type=AVC msg=audit(1426116901.941:13720): avc:  denied  { noatsecure } for  pid=3437 comm="check_disk" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nagios_checkdisk_plugin_t:s0 tclass=process
type=AVC msg=audit(1426116901.941:13720): avc:  denied  { siginh } for  pid=3437 comm="check_disk" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nagios_checkdisk_plugin_t:s0 tclass=process
type=AVC msg=audit(1426116901.941:13720): avc:  denied  { rlimitinh } for  pid=3437 comm="check_disk" scontext=system_u:system_r:nrpe_t:s0 tcontext=system_u:system_r:nagios_checkdisk_plugin_t:s0 tclass=process

In enforcing mode, only the first denial (the failure to create self:netlink_audit_socket) is logged, so that is the denial that kills sudo.

I don't know whether the successive denials would be fatal to sudo.
Comment 2 James Ralston 2015-03-18 19:49:46 UTC 
We rolled the following custom SELinux module to address these issues:

    # Module name and version.
    policy_module(nagios-local, 1.1.0)

    # Type requires.
    require {
            type nrpe_t;
            type sudo_exec_t;
    }

    # Permit NRPE to call sudo.
    can_exec(nrpe_t, sudo_exec_t)

    # Permit NRPE to send audit messages, via sudo.
    allow nrpe_t self:capability { audit_write sys_ptrace };
    allow nrpe_t self:netlink_audit_socket { create nlmsg_relay read write };

(We use this same policy module on both RHEL6 and RHEL7, so it's a superset of the permissions required on both.)

It would be really nice if you could fix the upstream policy, though, so we didn't have to resort to this work-around.
Comment 3 Miroslav Grepl 2015-04-09 09:14:18 UTC 
I would add a boolean for this.
Comment 4 Milos Malik 2015-04-20 09:49:46 UTC 
I believe that following files should not be labeled bin_t:

/usr/lib64/nagios/plugins/negate
/usr/lib64/nagios/plugins/urlize
/usr/lib64/nagios/plugins/utils.sh
Comment 5 James Ralston 2015-04-29 03:30:08 UTC 
In reply to Miroslav in comment 3: adding a boolean seems perfectly reasonable to me, as I can imagine that only a subset of Nagios/NRPE users need to call NRPE plugins via sudo.
Comment 7 Miroslav Grepl 2015-05-14 13:21:15 UTC 
Any chance to test it with

https://brewweb.devel.redhat.com/buildinfo?buildID=435085
Comment 8 Miroslav Grepl 2015-05-19 10:04:10 UTC 
We have some fixes but I am working on additional fixes now.
Comment 12 Simon Sekidde 2015-06-13 22:48:43 UTC 
*** Bug 1230670 has been marked as a duplicate of this bug. ***
Comment 13 Stanislav Graf 2015-06-24 19:25:39 UTC 
I've retested today with
selinux-policy-targeted-3.13.1-29.el7.noarch

All works as expected. I saw one new nrpe related issue on one of RHEL6 nodes, created Bug 1235405.

I had following booleans status on nagios server node:
nagios_run_pnp4nagios --> on
nagios_run_sudo --> on

and following on monitored node:
nagios_run_pnp4nagios --> off
nagios_run_sudo --> on
Comment 16 errata-xmlrpc 2015-11-19 10:28:44 UTC 
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, 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://rhn.redhat.com/errata/RHBA-2015-2300.html