Re: xinetd and su/runuser and dbus
On 04/30/2016 02:49 PM, Troels Arvin wrote:
Hi,
Hello,
Environment:
RHEL 7.2 with all the latest fixes.
The server has the Check_MK agent (check-mk-agent-1.2.6p16-3.el7.x86_64
from EPEL) installed, and the mk_postgres module has been activated by
symlinking /usr/share/check-mk-agent/available-plugins/mk_postgres to
/usr/share/check-mk-agent/plugins/mk_postgres
The agent plugin's code may be viewed here:
http://git.mathias-kettner.de/git/?p=check_mk.git;a=blob;f=agents/plugins/
mk_postgres;h=8333eee316a99e634394aee4f3048b6becc56d69;hb=c33010ba2d24c8b81c4e6221f3cd61bade7e7d9e
PostgreSQL version: rh-postgresql94-postgresql 9.4.6-1.el7.x86_64 (from
RHEL 7's software collections).
Trouble: The Check_MK agent reponse becomes very slow when the
mk_postgres agent plugin is activated -- to the extend that checks time
out, causing monitoring alerts and missing monitoring data.
Meanwhile, in /var/log/audit/audit.log:
type=USER_AVC msg=audit(1462018794.424:153): pid=704 uid=81
auid=4294967295 ses=4294967295 subj=system_u:system_r:system_dbusd_t:s0-
s0:c0.c1023 msg='avc: denied { send_msg } for msgtype=method_return
dest=:1.19 spid=925 tpid=2851
scontext=system_u:system_r:systemd_logind_t:s0
tcontext=system_u:system_r:inetd_child_t:s0-s0:c0.c1023 tclass=dbus
exe="/usr/bin/dbus-daemon" sauid=81 hostname=? addr=? terminal=?'
The AVC denials pop up when the mk_postgres agent plugin performs a "su"
to "postgres". Changing the script to use "runuser" instead of
"su" does
not help.
I've found two different ways to fix this; the latter seems best:
1. Stop the dbus.service and dbus.socket services. But this results in a
subsequent flood of messages like:
Apr 29 21:48:12 hostname su: pam_systemd(su-l:session): Failed to connect
to system bus: Connection refused
2. Add the following SELinux module:
---------------------------------------
module inetd_dbus 1.0;
require {
type systemd_logind_t;
type inetd_child_t;
class dbus send_msg;
}
#============= systemd_logind_t ==============
allow systemd_logind_t inetd_child_t:dbus send_msg;
---------------------------------------
I wonder if the above SELinux module could become part of the main
SELinux
policy? If so, should I open a Bugzilla request for xinetd, dbus, or
SELinux?
Please report bug against selinux-policy component.
--
Lukas Vrabec
SELinux Solutions
Red Hat, Inc.