rhel: provide our own SELinux custom policy package

CentOS, RHEL and Fedora distributions ship with their own Open vSwitch
SELinux policy that is too strict and prevents Open vSwitch to work
normally out of the box.

As a solution, this patch introduces a new package which will "loosen"
up "openvswitch_t" SELinux domain so that Open vSwitch could operate
normally.

Intended use-cases of this package are:
1. to allow users to install newer Open vSwitch on already released Fedora,
RHEL and CentOS distributions where the default Open vSwitch SELinux policy
that shipped with the corresponding Linux distribution is not up to date
and did not anticipate that a newer Open vSwitch version might need to
invoke new system calls or need to access certain system resources that
it did not before; And
2. to provide alternative means through which Open vSwitch developers
can proactively fix SELinux related policy issues without waiting for
corresponding Linux distribution maintainers to update their central
Open vSwitch SELinux policy.

This patch was tested on Fedora 23 and CentOS 7. I verified that now
on Fedora 23 Open vSwitch can create a NetLink socket; and that I did
not see following error messages:

vlog|INFO|opened log file /var/log/openvswitch/ovs-vswitchd.log
ovs_numa|INFO|Discovered 2 CPU cores on NUMA node 0
ovs_numa|INFO|Discovered 1 NUMA nodes and 2 CPU cores
reconnect|INFO|unix:/var/run/openvswitch/db.sock: connecting...
reconnect|INFO|unix:/var/run/openvswitch/db.sock: connected
netlink_socket|ERR|fcntl: Permission denied
dpif_netlink|ERR|Generic Netlink family 'ovs_datapath' does not exist.
                 The Open vSwitch kernel module is p robably not loaded.
dpif|WARN|failed to enumerate system datapaths: Permission denied
dpif|WARN|failed to create datapath ovs-system: Permission denied

I did not test all Open vSwitch features so there still could be some
OVS configuration that would get "Permission denied" errors.

Since, Open vSwitch daemons on Ubuntu 15.10 by default run under "unconfined"
SELinux domain, then there is no need to create a similar debian package
for Ubuntu, because it works on default Ubuntu installation.

Signed-off-by: Ansis Atteka <[email protected]>
Acked-by: Flavio Leitner <[email protected]>

INSTALL.SELinux.md

@@ -0,0 +1,173 @@
+Running Open vSwitch under SELinux
+==================================
+
+Security-Enhanced Linux (SELinux) is a Linux kernel security
+module that limits "the malicious things" that certain processes,
+including OVS, can do to the system in case they get compromised.
+In our case SELinux basically serves as the "second line of defense"
+that limits the things that OVS processes are allowed to do.  The
+"first line of defense" is proper input validation that eliminates
+code paths that could be used by attacker to do any sort of
+"escape attacks" (e.g. file name escape, shell escape, command
+line argument escape, buffer escape).  Since developers don't
+always implement proper input validation, then SELinux Access
+Control's goal is to confine damage of such attacks, if they
+turned out to be possible.
+
+Besides Type Enforcement there are other SELinux
+features, but they are out of scope for this document.
+
+Currently there are two SELinux policies for Open vSwitch:
+1. the one that ships with your Linux distribution (i.e.
+   selinux-policy-targeted package); And
+2. the one that ships with OVS (i.e. openvswitch-selinux-policy
+   package).
+
+
+Limitations
+-----------
+
+If Open vSwitch is directly started from command line, then it
+will run under "unconfined_t" SELinux domain that basically lets
+daemon to do whatever it likes.  This is very important for developers
+to understand, because they might introduced code in OVS that invokes
+new system calls that SELinux policy did not anticipate.  This means
+that their feature may have worked out just fine for them.  However,
+if someone else would try to run the same code when Open vSwitch is
+started through systemctl, then Open vSwitch would get Permission Denied
+errors.
+
+Currently the only distributions that enforce SELinux on OVS by
+default are RHEL, CentOS and Fedora.  While Ubuntu and Debian also
+have some SELinux support, they run Open vSwitch under the unrestricted
+"unconfined" domain.  Also, it seems that Ubuntu is leaning towards
+Apparmor that works slightly differently than SELinux.
+
+SELinux and Open vSwitch are moving targets.  What this means
+is that, if you solely rely on your Linux distribution's SELinux policy,
+then this policy might not have correctly anticipated that a newer
+Open vSwitch version needs extra white list rules.  However, if you
+solely rely on SELinux policy that ships with Open vSwitch, then
+Open vSwitch developers might not have correctly anticipated the
+feature set that your SELinux implementation supports.
+
+
+Installation
+------------
+
+Refer to [INSTALL.Fedora.md] for instructions on how to build all
+Open vSwitch rpm packages.
+
+Once the package is built, install it on your Linux distribution with:
+
+   # yum install openvswitch-selinux-policy-2.4.1-1.el7.centos.noarch.rpm
+
+And, then restart Open vSwitch:
+
+   # systemctl restart openvswitch
+
+
+Troubleshooting
+---------------
+
+When SELinux was implemented some of the standard system utilities
+acquired "-Z" flag (e.g. "ps -Z", "ls -Z").  For example, to find out
+under which SELinux security domain process runs, use:
+
+   # ps -AZ | grep ovs-vswitchd
+   system_u:system_r:openvswitch_t:s0 854 ?    ovs-vswitchd
+
+To find out the SELinux label of file or directory, use:
+
+   # ls -Z /etc/openvswitch/conf.db
+   system_u:object_r:openvswitch_rw_t:s0 /etc/openvswitch/conf.db
+
+
+If, for example, SELinux policy for Open vSwitch is too strict,
+then you might see in Open vSwitch log files "Permission Denied"
+errors:
+
+    # cat /var/log/openvswitch/ovs-vswitchd.log
+    vlog|INFO|opened log file /var/log/openvswitch/ovs-vswitchd.log
+    ovs_numa|INFO|Discovered 2 CPU cores on NUMA node 0
+    ovs_numa|INFO|Discovered 1 NUMA nodes and 2 CPU cores
+    reconnect|INFO|unix:/var/run/openvswitch/db.sock: connecting...
+    reconnect|INFO|unix:/var/run/openvswitch/db.sock: connected
+    netlink_socket|ERR|fcntl: Permission denied
+    dpif_netlink|ERR|Generic Netlink family 'ovs_datapath' does not exist.
+                     The Open vSwitch kernel module is probably not loaded.
+    dpif|WARN|failed to enumerate system datapaths: Permission denied
+    dpif|WARN|failed to create datapath ovs-system: Permission denied
+
+
+
+However, not all "Permission denied" errors are caused by SELinux.  So,
+before blaming too strict SELinux policy, make sure that indeed SELinux
+was the one that denied OVS access to certain resources, for example, run:
+
+   # grep "openvswitch_t" /var/log/audit/audit.log | tail
+   type=AVC msg=audit(1453235431.640:114671): avc:  denied  { getopt } for  pid=4583 comm="ovs-vswitchd" scontext=system_u:system_r:openvswitch_t:s0 tcontext=system_u:system_r:openvswitch_t:s0 tclass=netlink_generic_socket permissive=0
+
+
+If SELinux denied OVS access to certain resources, then make sure that you
+have installed our SELinux policy package that "loosens" up distribution's
+SELinux policy:
+
+   # rpm -qa | grep openvswitch-selinux
+   openvswitch-selinux-policy-2.4.1-1.el7.centos.noarch
+
+And, then verify that this module was indeed loaded:
+
+   # semodule -l | grep openvswitch
+   openvswitch-custom    1.0
+   openvswitch          1.1.1
+
+If you still see Permission denied errors, then take a look
+into selinux/openvswitch.te file in the OVS source tree and
+try to add white list rules.  This is really simple, just run
+SELinux audit2allow tool:
+
+   # grep "openvswitch_t" /var/log/audit/audit.log | audit2allow -M ovslocal
+
+See "Contributing SELinux policy patches" section, if you think
+that other Open vSwitch users would benefit from your SELinux policy
+changes.
+
+
+Contributing SELinux policy patches
+-----------------------------------
+
+Here are few things to consider before proposing SELinux policy
+patches to Open vSwitch developer mailing list:
+
+1. The SELinux policy that resides in Open vSwitch source tree
+   amends SELinux policy that ships with your distributions.
+
+   Implications of this are that it is assumed that the distribution's
+   Open vSwitch SELinux module must be already loaded to satisfy
+   dependencies.
+
+2. The SELinux policy that resides in Open vSwitch source tree
+   must work on all currently relevant Linux distributions.
+
+   Implications of this are that you should use only those SELinux
+   policy features that are supported by the lowest SELinux version
+   out there.  Typically this means that you should test your SELinux
+   policy changes on the oldest RHEL or CentOS version that this
+   OVS version supports.  Check INSTALL.Fedora.md file to find out
+   this.
+
+3. The SELinux policy is enforced only when state transition to
+   openvswitch_t domain happens.
+
+   Implications of this are that perhaps instead of loosening SELinux
+   policy you can do certain things at the time rpm package is installed.
+
+
+
+Reporting Bugs
+--------------
+
+Please report problems to [email protected].
+
+[INSTALL.md]:INSTALL.md

Makefile.am

@@ -79,6 +79,7 @@ docs = \
 	INSTALL.Libvirt.md \
 	INSTALL.NetBSD.md \
 	INSTALL.RHEL.md \
+	INSTALL.SELinux.md \
 	INSTALL.SSL.md \
 	INSTALL.XenServer.md \
 	INSTALL.userspace.md \
@@ -432,3 +433,4 @@ include datapath-windows/automake.mk
 include datapath-windows/include/automake.mk
 include windows/automake.mk
 include ovn/automake.mk
+include selinux/automake.mk

NEWS

@@ -29,6 +29,8 @@ Post-v2.5.0
    - python:
      * Added support for Python 3.4+ in addition to existing support
        for 2.7+.
+   - SELinux:
+     * Introduced SELinux policy package.
 
 v2.5.0 - xx xxx xxxx
 ---------------------

README.md

@@ -97,6 +97,8 @@ To use Open vSwitch...
 
 - ...without using a kernel module, read [INSTALL.userspace.md].
 
+- ...with SELinux, read [INSTALL.SELinux.md].
+
 For answers to common questions, read [FAQ.md].
 
 To learn how to set up SSL support for Open vSwitch, read [INSTALL.SSL.md].

rhel/openvswitch-fedora.spec.in

@@ -46,6 +46,7 @@ BuildRequires: systemd-units openssl openssl-devel
 BuildRequires: python python-twisted-core python-zope-interface PyQt4 python-six
 BuildRequires: desktop-file-utils
 BuildRequires: groff graphviz
+BuildRequires: checkpolicy, selinux-policy-devel
 # make check dependencies
 BuildRequires: procps-ng
 %if %{with libcapng}
@@ -72,6 +73,15 @@ Open vSwitch provides standard network bridging functions and
 support for the OpenFlow protocol for remote per-flow control of
 traffic.
 
+%package selinux-policy
+Summary: Open vSwitch SELinux policy
+License: ASL 2.0
+BuildArch: noarch
+Requires: selinux-policy-targeted
+
+%description selinux-policy
+Tailored Open vSwitch SELinux policy
+
 %package -n python-openvswitch
 Summary: Open vSwitch python bindings
 License: ASL 2.0
@@ -131,6 +141,8 @@ overlays and security groups.
 	--with-pkidir=%{_sharedstatedir}/openvswitch/pki
 
 make %{?_smp_mflags}
+cd selinux
+make -f %{_datadir}/selinux/devel/Makefile
 
 %install
 rm -rf $RPM_BUILD_ROOT
@@ -172,6 +184,9 @@ install -d -m 0755 $RPM_BUILD_ROOT/%{_sharedstatedir}/openvswitch
 touch $RPM_BUILD_ROOT%{_sysconfdir}/openvswitch/conf.db
 touch $RPM_BUILD_ROOT%{_sysconfdir}/openvswitch/system-id.conf
 
+install -p -m 644 -D selinux/openvswitch-custom.pp \
+        $RPM_BUILD_ROOT%{_datadir}/selinux/packages/%{name}/openvswitch-custom.pp
+
 # remove unpackaged files
 rm -f $RPM_BUILD_ROOT%{_bindir}/ovs-parse-backtrace \
         $RPM_BUILD_ROOT%{_bindir}/ovs-pcap \
@@ -244,6 +259,9 @@ rm -rf $RPM_BUILD_ROOT
     fi
 %endif
 
+%post selinux-policy
+/usr/sbin/semodule -i %{_datadir}/selinux/packages/%{name}/openvswitch-custom.pp &> /dev/null || :
+
 %postun
 %if 0%{?systemd_postun_with_restart:1}
     %systemd_postun_with_restart %{name}.service
@@ -270,6 +288,15 @@ rm -rf $RPM_BUILD_ROOT
     fi
 %endif
 
+%postun selinux-policy
+if [ $1 -eq 0 ] ; then
+  /usr/sbin/semodule -r openvswitch-custom &> /dev/null || :
+fi
+
+%files selinux-policy
+%defattr(-,root,root)
+%{_datadir}/selinux/packages/%{name}/openvswitch-custom.pp
+
 %files -n python-openvswitch
 %{python_sitelib}/ovs
 %doc COPYING

selinux/automake.mk

@@ -0,0 +1,9 @@
+# Copyright (C) 2016 Nicira, Inc.
+#
+# Copying and distribution of this file, with or without modification,
+# are permitted in any medium without royalty provided the copyright
+# notice and this notice are preserved.  This file is offered as-is,
+# without warranty of any kind.
+
+EXTRA_DIST += \
+        selinux/openvswitch-custom.te

selinux/openvswitch-custom.te

@@ -0,0 +1,9 @@
+module openvswitch-custom 1.0;
+
+require {
+        type openvswitch_t;
+        class netlink_socket { setopt getopt create connect getattr write read };
+}
+
+#============= openvswitch_t ==============
+allow openvswitch_t self:netlink_socket { setopt getopt create connect getattr write read };