Tor on HardenedBSD

In this post, we’ll detail how we set up Tor on HardenedBSD. We’ll use HardenedBSD 11-STABLE, which ships with LibreSSL as the default crypto library in base and in ports. The vast majority of Tor infrastructure nodes run Linux and OpenSSL. Emerald Onion believes running HardenedBSD will help improve the diversity and resiliency of the Tor network. Additionally, running HardenedBSD gives us peace of mind due to its expertly crafted, robust, and scalable exploit mitigations. Together, Emerald Onion and HardenedBSD are working towards a safer and more secure Tor network.

This article should be considered a living document. We’ll keep it up-to-date as HardenedBSD and Emerald Onion evolve.

Initial Steps

Downloading and installing HardenedBSD 11-STABLE is simple. Navigate to the latest build and download the installation media that suits your needs. The memstick image is suited for USB flash drives. Boot the installation media.

Installing HardenedBSD is simple. Follow the prompts. Sample screenshots are provided below:

  1. Select Install:
  2. Select your keymap. If you use a standard US English keyboard, the default is fine:
  3. Choose a hostname:
  4. Select the distribution sets to install:
  5. Choose your filesystem. For purposes of this article, we’ll use ZFS for full-disk encryption:
  6. Selecting the Pool Type will allow you to configure your ZFS pool the way you want. We will just use a single disk in this article:
  7. Since we’re using a single disk, we’ll select the Stripe option:
  8. Select the disks to use in the pool. Only a single disk for us:
  9. After selecting the disks, you’ll go back to the original ZFS setup menu. We’ve made a few changes (Encrypt Disks, Swap Size, Encrypt Swap):
  10. Review the changes:
  11. Set the password on your encrypted ZFS pool:
  12. Validate the password:
  13. Encrypted ZFS will initialize itself:
  14. HardenedBSD will now install distribution sets:
  15. Set the root password:
  16. If you want to set up networking, select the network device to configure. In this article, we’ll set up a dynamic (DHCP) network configuration:
  17. We want to use IPv4:
  18. We want to use DHCP:
  19. It will try to acquire a DHCP lease:
  20. At Emerald Onion, we put IPv6 first. However, in this example article, we won’t use IPv6 as it’s not currently available. So we’ll choose no when prompted to set up IPv6:
  21. Ensure the DNS information is correct and make any changes if needed:
  22. It’s now time to choose the system timezone. Select the region:
  23. We chose America. We’ll choose United States for the country next:
  24. Finally we’ll chose the actual timezone:
  25. Confirm the timezone:
  26. Because we use NTP, we’ll skip setting the date:
  27. We’ll also skip setting the time:
  28. Select the services to start at boot:
  29. Select the system hardening options. HardenedBSD sets options one through five by default, so there’s no need to set them here.
  30. We will go ahead and add an unprivileged user. Make sure to add the user to the “wheel” group for access to use the su program:
  31. Set the user’s details:
  32. HardenedBSD is now installed! Exit the installer. The installer will do things in the background so there may be some delay between exiting and the next prompt:
  33. We don’t want to make further modifications to the installation prior to rebooting:
  34. Go ahead and reboot:

The installation is now complete!

Installing Tor

Installing Tor is simple, too. Once HardenedBSD is installed and you’ve logged in, run the following command:

# pkg install tor

The Tor package on HardenedBSD, and its upstream FreeBSD, currently does not ship with a modified Tor configuration file, which can be found at /usr/local/etc/tor/torrc. Tor isn’t set up to log outside of initial startup messages. You will need to edit the Tor configuration file to suit your needs. Take a look at the tor(1) manpage for all the available configuration options.

In our set up, Tor listens on TCP ports 80 and 443 as an unprivileged user. We need to tell HardenedBSD to allow non-root users to be able to bind to ports that traditionally require root privileges:

# echo 'net.inet.ip.portrange.reservedhigh=0' >> /etc/sysctl.conf
# service sysctl start

Multi-Instance Tor

At Emerald Onion, we run multiple instances of Tor on the same server. This allows us to scale Tor to our needs. The following instructions detail how to set up multi-instance Tor. The same instructions can be used for single-instance Tor.

We named our instances simple names: instance-01, instance-02, instance-03, and so on. Each instance has its own configuration file, located at /usr/local/etc/tor/torrc@${instance_name}. We first set up a template config file:

Nickname EmeraldOnion%%INSTANCE%%
Address tor01.emeraldonion.org
ContactInfo abuse_at_emeraldonion_dot_org
Log notice file /var/log/tor/instance-%%INSTANCE%%/notices.log
OutboundBindAddressExit %%IP4ADDR%%
OutboundBindAddressOR %%IP4ADDR%%
DirPort %%IP4ADDR%%:80
ORPort %%IP4ADDR%%:443
ORPort %%IP6ADDR%%:443
RelayBandwidthRate 24 MBytes
RelayBandwidthBurst 125 MBytes
MyFamily %%FAMILY%%
IPv6Exit 1
ExitPolicy accept *:*
ExitPolicy accept6 *:*
SocksPort 0

The next script installs the appropriate config file based on the above template. Some things are sanitized. Shawn, who wrote the script, is a fan of zsh.

#!/usr/local/bin/zsh

ninstances=5

family=""

for ((i=1; i <= ${ninstances}; i++)); do
	instance=$(printf '%02d' ${i})

	family=""
	for ((k=1; k <= ${ninstances}; k++)); do
		[ ${k} -eq ${i} ] && continue
		[ ${#family} -gt 0 ] && family="${family},"
		family="${family}EmeraldOnion$(printf '%02d' ${k})"
	done

	sed -e "s/%%INSTANCE%%/${instance}/g" \
		-e "s/%%IP4ADDR%%/192.168.1.$((${i} + 10))/g" \
		-e "s/%%IP6ADDR%%/\[fe80::$((${i} + 10))\]/g" \
		-e "s/%%FAMILY%%/${family}/g" \
		tmpl.config > /usr/local/etc/tor/torrc@instance-${instance}
	mkdir -p /var/log/tor/instance-${instance}
	chown _tor:_tor /var/log/instance-${instance}
	chmod 700 /var/log/instance-${instance}
done

We then instructed the Tor rc script not to run the default instance of Tor:

# sysrc tor_disable_default_instance=YES

Then we tell the rc system which Tor instances we want to run and set Tor to start at boot:

# sysrc tor_instances="instance-01 instance-02 instance-03 instance-04 instance-05"
# sysrc tor_enable=YES

Then we start Tor. The first time the Tor rc script starts Tor, it will create the data and logging directories for you with the proper permissions.

# service tor start

Keeping HardenedBSD and Tor Up-To-Date

Updating HardenedBSD is simple with hbsd-update. We publish updates for base periodically. Feel free to use hbsd-update as often as you’d like to check for updates to the base operating system.

For example:

# hbsd-update
# shutdown -r now

To update your packages, including Tor, use:

# pkg upgrade

Tor Service Management Basics

The tor rc script uses SIGINT when shutting Tor down. This causes Tor to shutdown in an ungraceful manner, immediately halting connections from clients. Instead of using the traditional service tor stop command, directly issue SIGTERM to the instance you wish to stop.

# service tor status instance-01
tor is running as pid 70918.
# kill -SIGTERM 70918

If you’d like to stop all instances in a graceful way at the same time:

# killall -SIGTERM tor

In a multi-instance setup, you can tell the service command which instance you want to control by appending the instance name (the portion after the @ symbol of the torrc file) at the end of the command. For example, to reload the config file for instance-01, issue the following command:

# service tor reload instance-01

If you want to reload the config file for all instances, simply remove the instance name from the above command. The rc script will issue the reload command across all instances.

If you’d like to look at an instance’s log file, you can use the tail command:

# tail -f /var/log/tor/instance-01/notices.log

Future Work

In the future, we would like to further harden our Tor setup by having each instance deployed in its own HardenedBSD jail. Once that is complete, we will document and publish the steps we took.