First, let’s set up the PF table which will control the traffic. Add the following to your /etc/pf.conf :

# add time block table
table <time_block> { } persist

Next, create a PF rule which block traffic for all entries in the time_block table:

# block all CIDR addresses in the time block table
block in quick log from <time_block> to any

Since the time_block table is still empty, no traffic is actually blocked.

The last thing to implement, is periodically manipulating the time_block table. This could be done by creating two cronjobs:

1. allow traffic at the beginning of “business hours”
2. block traffic at the end of “business hours”

crontab -e
# Allow traffic
0 7 * * * /usr/local/scripts/allow_employees.sh > /dev/null 2>&1
# Block traffic
0 17 * * * /usr/local/scripts/block_employees.sh > /dev/null 2>&1


The allow_employees.sh script will allow certain network ranges by ensuring those are removed from the time_block table:

#!/bin/sh

/sbin/pfctl -Td -t time_block 10.1.0.0/24
/sbin/pfctl -Td -t time_block 10.2.0.0/24

The block_employees.sh script will do the exact opposite: it will add ranges to the time_block table so that their network access will be blocked by the firewall:

#!/bin/sh

/sbin/pfctl -Ta -t time_block 10.1.0.0/24
/sbin/pfctl -Ta -t time_block 10.2.0.0/24

Finally deploy your new PF rules (first test them!)

pfctl -nf /etc/pf.conf
pfctl -f /etc/pf.conf

• USB / mSSD drive to install OpenBSD on
• USB drive to boot from
• Serial cable for the initial installation

First go to a mirror and download the amd64 OpenBSD install image, which ends on the .fs extension. The one for OpenBSD 6.0 is called ‘install60.fs’.

The installation procedure will use an USB stick to boot the installation process.
The USB stick itself was created on a Linux Desktop system, using dd. There are many ways to get the install image on an USB stick. Google if you are not using a Linux desktop.

I downloaded the install image to my ‘Downloads’ folder, and the USB stick was on /dev/sdb

dd if=./Downloads/install60.fs of=/dev/sdb bs=1024k

Once the USB stick/ disk is ready, insert it in your Soekris net6501.

Now prepare your terminal console. I’ve used Minicom for this purpose, but any kind of terminal emulation program can be used.

Execute the following on the command line:

minicom -D /dev/ttyUSB0 -b 19200 # no software or hardware flow control

Important to note is:
– The baudrate must be set to 19200 baud
– You must disable software and/ or hardware flow control

Once connected with the serial console cable, plug in the power cable to your Soekris so that it can be boot up.

At the boot prompt, configure the installation image to send its output to the serial console.

Using drive 1, partition 3.
Loading.........
probing: pc0 com0 pci mem[620K 1022M a20=on]
disk: hd0+* hd1+ hd2*
>> OpenBSD/i386 BOOT 3.29
boot> stty com0 19200
boot> set tty com0
switching console to com0
>> OpenBSD/i386 BOOT 3.29
boot> bsd 

There are two commands that must be executed at the boot prompt:
– stty com0 19200
– set tty com0

After the serial console options have been set, boot the kernel by typing bsd and hiting ENTER

The first steps are to configure the network interfaces.
Please also make sure you have enabled sshd, so that after the installation you can access the firewall without using the serial console cable.

The rest of the installation won’t be covered here.

It runs on most operating systems, including Linux, MacOS, Solaris, HP-UX, AIX and OpenBSD.

There is no OSSEC package available on the OSSEC website or in the OpenBSDs ports repositry, so I’ve decided to create an OpenBSD on my own.
OpenBSD packages are pretty easy to create and are very useful when installing, upgrading or deleting software on a server.

One of the disadvantages when creating an OpenBSD package, is that you will need to have X11 installed on your OpenBSD system.
In the following example I have used OpenBSD 5.8 to create a package for OSSEC 2.8.2 (OSSEC 2.8.3 doesn’t compile on OpenBSD 5.8)

Step 1: Prerequisites

cd /tmp
wget http://ftp.eu.openbsd.org/pub/OpenBSD/5.8/amd64/xbase58.tgz 
wget http://ftp.eu.openbsd.org/pub/OpenBSD/5.8/amd64/xshare58.tgz
wget http://ftp.eu.openbsd.org/pub/OpenBSD/5.8/amd64/comp58.tgz
tar -C / -xzvphf xbase58.tgz
tar -C / -xzvphf xshare58.tgz
tar -C / -xzvphf comp58.tgz

cd /tmp
ftp http://ftp.eu.openbsd.org/pub/OpenBSD/$(uname -r)/ports.tar.gz
ftp http://ftp.eu.openbsd.org/pub/OpenBSD/$(uname -r)/SHA256.sig
signify -Cp /etc/signify/openbsd-$(uname -r | cut -c 1,3)-base.pub -x SHA256.sig ports.tar.gz

cd /usr
tar xzf /tmp/ports.tar.gz

You will also need a compiler:

pkg_add gcc

Step 2: Download and repack the source

ossec_version="2.8.2"
cd /usr/src
wget https://github.com/ossec/ossec-hids/archive/${ossec_version}.tar.gz 
mv ${ossec_version}.tar.gz ossec-hids-${ossec_version}.tar.gz 
tar xfz ossec-hids-${ossec_version}.tar.gz
cd ossec-hids-${ossec_version}

Since the Makefile for OSSEC is in the src/ sub directory, we will create a proxy Makefile in /usr/src/ossec-hids-2.8.2

cd ossec-hids-2.8.2
vim Makefile

I have actually taken the original Makefile from src/ and narrowed it down to the following:

# Makefile
# http://www.ossec.net/hids/

none:
 @echo "Nothing selected ..."
 @echo "\"make all\" to compile everything."
 @echo "\"make server\" to build the server."
 @echo "\"make local\" to build the local."
 @echo "\"make agent\" to build the agent."
 @echo "\"make clean\" to clean anything built."

clean:
 cd src/ ; $(MAKE) clean

all:
 cd src/ ; $(MAKE) all
 
test:
 cd src/ ; $(MAKE) test

server:
 cd src/ ; $(MAKE) server

local:
 cd src/ ; $(MAKE) local

agent:
 cd src/ ; $(MAKE) agent

We will also edit the ‘ossec-clients.sh‘ script, because we will use this script as a start/stop script. We will have to set the path name in this script.

vim src/init/ossec-client.sh
# LOCAL=/var/ossec
# cd ${LOCAL}
# PWD=`pwd`
DIR=/var/ossec
cd ${DIR}

And that’s the only thing we will need to change in the sources, we can now repackage it.

cd ..
tar czf /usr/ports/distfiles/ossec-hids-2.8.2.tar.gz ossec-hids-2.8.2/

Step 3: Prepare the ports directory

The following steps explain how to set up a ports directory in /usr/ports for OSSEC, in order to build the package.
Custom made packages are built in /usr/ports/mystuff. In there, we will have to one sub directory for the package category (we will use security) and in there the package name, which in our case will be ossec-hids.

cd /usr/ports/mystuff
mkdir -p security/ossec-hids

The configuration file for building an OpenBSD package is a Makefile. There is a template file in /usr/ports/infrastructure/templates/Makefile.template which can be used.

cd security/ossec-hids
cp /usr/ports/infrastructure/templates/Makefile.template Makefile

This file of course needs editing. Not everything is required in this file, so I have narrowed the Makefile down to what I need it for:

# $OpenBSD: Makefile.template,v 1.68 2013/10/02 07:34:45 ajacoutot Exp $
# $FreeBSD/NetBSD: credit FreeBSD/NetBSD if thats where the port came from $
# Original from: credit the original author here
COMMENT =               OSSEC is an Open Source HIDS
DISTNAME =              ossec-hids-2.8.2
CATEGORIES =            security
HOMEPAGE =              http://www.ossec.net/
MAINTAINER =            Johnny Morano <jmorano@moretrix.com>;
MASTER_SITES =          https://github.com/ossec/ossec-hids/

PERMIT_PACKAGE_CDROM =  Yes
PERMIT_PACKAGE_FTP =    Yes
PERMIT_DISTFILES_FTP =  Yes

PKG_ARCH =              *
PREFIX = /var/ossec

do-install:
        mkdir -p ${PREFIX}/bin
        mkdir -p ${PREFIX}/logs
        mkdir -p ${PREFIX}/var/run
        mkdir -p ${PREFIX}/queue
        mkdir -p ${PREFIX}/active-response/bin
        mkdir -p ${PREFIX}/agentless
        mkdir -p ${PREFIX}/etc/orig/shared
        mkdir -p ${PREFIX}/doc
        ${INSTALL_SCRIPT} ${WRKSRC}/active-response/firewalls/pf.sh ${PREFIX}/active-response/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/agentlessd/scripts/* ${PREFIX}/agentless
        ${INSTALL_SCRIPT} ${WRKSRC}/src/os_execd/ossec-execd ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/logcollector/ossec-logcollector ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/client-agent/ossec-agentd ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/addagent/manage_agents ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/syscheckd/ossec-syscheckd ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/os_auth/agent-auth ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/init/ossec-client.sh ${PREFIX}/bin/
        ${INSTALL_SCRIPT} ${WRKSRC}/doc/*.txt ${PREFIX}/doc/
        ${INSTALL_SCRIPT} ${WRKSRC}/doc/README.config ${PREFIX}/doc/
        ${INSTALL_SCRIPT} ${WRKSRC}/etc/*.conf ${PREFIX}/etc/orig/
        ${INSTALL_SCRIPT} ${WRKSRC}/etc/*.xml ${PREFIX}/etc/orig/
        ${INSTALL_SCRIPT} ${WRKSRC}/src/rootcheck/db/* ${PREFIX}/etc/orig/shared/

.include <bsd.port.mk>;

The above Makefile will install OSSEC in /var/ossec and will only install the agent files. It does not install the server files.

Step 4: Test the settings

First we will make a checksum and then we will start a fake compile run, to see if everything compiles nicely.

make makesum 
===>  Checking files for ossec-hids-2.8.2
`/usr/ports/distfiles/ossec-hids-2.8.2.tar.gz' is up to date.

make fake
===>  Checking files for ossec-hids-2.8.2
`/usr/ports/distfiles/ossec-hids-2.8.2.tar.gz' is up to date.
>> (SHA256) ossec-hids-2.8.2.tar.gz: OK
===>  Extracting for ossec-hids-2.8.2
===>  Patching for ossec-hids-2.8.2
===>  Configuring for ossec-hids-2.8.2
===>  Building for ossec-hids-2.8.2
***snip***

If there were no errors, then we are ready to create the actual package.

Step 5: Create the OpenBSD package

mkdir pkg
echo "OSSEC is an Open Source HIDS" > pkg/DESCR
make plist
vim pkg/PLIST

Normally we do not need to edit the PLIST file, but I wanted to create an ossec user upon installation and chown the /var/ossec directory to that user.
So I have added the following lines to the top of pkg/PLIST:

@comment $OpenBSD$
@newgroup ossec:1002
@newuser ossec:1005:ossec:daemon:OSSEC User:/var/ossec:/bin/sh

And these to the bottom:

@exec-add mkdir -p /var/ossec
@exec-add chown -R ossec.ossec /var/ossec
@exec-add cp %D/bin/ossec-client.sh /etc/rc.d/ossec

Afterwards you will need to run:

make plist

Now we are ready to build the package:

make package
`/usr/ports/pobj/ossec-hids-2.8.2/fake-amd64/.fake_done' is up to date.
===>  Building package for ossec-hids-2.8.2
Create /usr/ports/packages/amd64/no-arch/ossec-hids-2.8.2.tgz
Link to /usr/ports/packages/amd64/all/ossec-hids-2.8.2.tgz
Link to /usr/ports/packages/amd64/ftp/ossec-hids-2.8.2.tgz
Link to /usr/ports/packages/amd64/cdrom/ossec-hids-2.8.2.tgz

That’s it! This package can now be installed with the pkg_add command.

pkg_add ./ossec-hids-2.8.2.tgz 
quirks-2.114 signed on 2015-08-09T11:57:52Z
UNSIGNED PACKAGE file:./ossec-hids-2.8.2.tgz: install anyway ? [y/N/a] y
ossec-hids-2.8.2: ok
UNSIGNED PACKAGES: ossec-hids-2.8.2