doc: Convert INSTALL.SELinux to rST

Refer to 'dnf' and not the deprecated 'yum'.

Signed-off-by: Stephen Finucane <stephen@that.guru>
Signed-off-by: Russell Bryant <russell@ovn.org>

Author: stephenfin

INSTALL.SELinux.md

@@ -0,0 +1,174 @@
+..
+      Licensed under the Apache License, Version 2.0 (the "License"); you may
+      not use this file except in compliance with the License. You may obtain
+      a copy of the License at
+
+          http://www.apache.org/licenses/LICENSE-2.0
+
+      Unless required by applicable law or agreed to in writing, software
+      distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+      WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+      License for the specific language governing permissions and limitations
+      under the License.
+
+      Convention for heading levels in Open vSwitch documentation:
+
+      =======  Heading 0 (reserved for the title in a document)
+      -------  Heading 1
+      ~~~~~~~  Heading 2
+      +++++++  Heading 3
+      '''''''  Heading 4
+
+      Avoid deeper levels because they do not render well.
+
+=========================
+Open vSwitch with 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", such as 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:
+
+- the one that ships with your Linux distribution (i.e.
+  selinux-policy-targeted package)
+
+- 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 the `Fedora installation guide <INSTALL.Fedora.rst>`__ for
+instructions on how to build all Open vSwitch rpm packages.
+
+Once the package is built, install it on your Linux distribution::
+
+    $ dnf install openvswitch-selinux-policy-2.4.1-1.el7.centos.noarch.rpm
+
+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
+
+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
+
+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.rst 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
+--------------
+
+Report problems to bugs@openvswitch.org.

INSTALL.SELinux.rst

@@ -81,7 +81,7 @@ docs = \
 	INSTALL.Libvirt.rst \
 	INSTALL.NetBSD.rst \
 	INSTALL.RHEL.rst \
-	INSTALL.SELinux.md \
+	INSTALL.SELinux.rst \
 	INSTALL.SSL.rst \
 	INSTALL.XenServer.rst \
 	INSTALL.userspace.rst \

Makefile.am

@@ -96,7 +96,7 @@ To use Open vSwitch...
 
 - ...with DPDK, see `here <INSTALL.DPDK.rst>`__.
 
-- ...with SELinux, see `here <INSTALL.SELinux.md>`__.
+- ...with SELinux, see `here <INSTALL.SELinux.rst>`__.
 
 For answers to common questions, refer to the `FAQ <FAQ.rst>`__.