Description of problem:
SELinux prevents /sbin/realm (...PackageKit) from installation of additional packages required for joining an AD domain, when they are not present on the system while it is preparing to enroll a machine into given domain.

Version-Release number of selected component (if applicable):
# rpm -q realmd selinux-policy adcli
realmd-0.12-1.fc18.x86_64
selinux-policy-3.11.1-76.

How reproducible:
always (before the missing pakcages are installed)
so make sure to remove them each time while testing your fix

Steps to Reproduce:
1. Setup M$ AD as described here: http://stef.thewalter.net/2012/08/how-to-create-active-directory-domain.html

2. Try to discover the domain: 
# realm discover security.baseos.qe
...
  required-package: sssd-tools
  required-package: sssd
  required-package: adcli
  required-package: samba-common
...

3. Try to join the configured domain: 
# realm join -v security.baseos.qe
 * Searching for kerberos SRV records for domain: _kerberos._udp.security.baseos.qe
 * Searching for MSDCS SRV records on domain: _kerberos._tcp.dc._msdcs.security.baseos.qe
 * dc.security.baseos.qe:88 
 * Found kerberos DNS records for: security.baseos.qe
 * Found AD style DNS records for: security.baseos.qe
 * Successfully discovered: security.baseos.qe
 * Couldn't find file: /usr/sbin/sss_cache
 * Assuming packages installed
 ! Failed to enroll machine in realm: GDBus.Error:org.freedesktop.DBus.Error.AccessDenied: An SELinux policy prevents this sender from sending this message to this recipient, 0 matched rules; type="method_call", sender=":1.121" (uid=0 pid=12103 comm="/usr/lib64/realmd/realmd ") interface="org.freedesktop.PackageKit" member="CreateTransaction" error name="(unset)" requested_reply="0" destination=":1.304" (uid=0 pid=19277 comm="/usr/libexec/packagekitd ")
realm: Couldn't join realm: Failed to enroll machine in realm. See diagnostics.

[root@godot ~]# ausearch -m user_avc -ts recent
----
time->Wed Feb 13 17:36:06 2013
type=USER_AVC msg=audit(1360773366.578:684): pid=755 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_call interface=org.freedesktop.DBus.Properties member=GetAll dest=:1.304 spid=12103 tpid=19277 scontext=system_u:system_r:realmd_t:s0-s0:c0.c1023 tcontext=system_u:system_r:rpm_t:s0-s0:c0.c1023 tclass=dbus  exe="/usr/bin/dbus-daemon" sauid=81 hostname=? addr=? terminal=?'
----
time->Wed Feb 13 17:36:06 2013
type=USER_AVC msg=audit(1360773366.579:685): pid=755 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_call interface=org.freedesktop.DBus.Properties member=GetAll dest=:1.304 spid=12103 tpid=19277 scontext=system_u:system_r:realmd_t:s0-s0:c0.c1023 tcontext=system_u:system_r:rpm_t:s0-s0:c0.c1023 tclass=dbus  exe="/usr/bin/dbus-daemon" sauid=81 hostname=? addr=? terminal=?'
----
time->Wed Feb 13 17:36:06 2013
type=USER_AVC msg=audit(1360773366.579:686): pid=755 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_call interface=org.freedesktop.PackageKit member=CreateTransaction dest=:1.304 spid=12103 tpid=19277 scontext=system_u:system_r:realmd_t:s0-s0:c0.c1023 tcontext=system_u:system_r:rpm_t:s0-s0:c0.c1023 tclass=dbus  exe="/usr/bin/dbus-daemon" sauid=81 hostname=? addr=? terminal=?'
  
Actual results:
realm fails to enroll machine

Expected results:
successful enrolment

Additional info:
Creation of a policy module similar to the one below allowed installation of the missing packages, though some more policy tuning might help even more ;-)

module realmd-dbus 1.0;

require {
	type realmd_t;
	type rpm_t;
	class dbus send_msg;
}

#============= realmd_t ==============
allow realmd_t rpm_t:dbus send_msg;