Eric Radman : a Journal

An OpenBSD Workstation

Terminal Fonts

The most important feature of any workstation is getting a terminal that is pleasant to use. By default most terminals render text with a heavier weight than I would like. To solve this select a font with a light or book variation. Here is my invocation for the simple terminal

st -f 'Hermit:light:pixelsize=14:antialias=true:autohint=true'

My st port includes

The really compelling feature of st is that it automatically substitutes glyphs from the default font if the one you've selected does not contain them. This enables me to use the really excellent Hermit font while retaining the extended character set of DejaVu Sans.

utf-8 and colors

To ensure you get full Unicode support from applications such as mutt or tmux set your language type using

LC_CTYPE=en_US.UTF-8
export LC_CTYPE

Suspend & Resume

OpenBSD has very good ACPI support, see apmd(8). zzz and ZZZ are shortcuts for suspend and hibernate if apmd is run at startup.

apmd_flags="-A"

-A will automatically scale the CPU frequency to save power.

X Configuration: .xinitrc

# .xinitrc
xset -b

while true; do
    batt="$(sysctl -n hw.sensors.acpibat0.watthour3 | cut -f1,2 -d" ")"
    xsetroot -name "$batt"
    sleep 60
done &
xsetroot -solid gray40
exec dwm

xset -b disables the annoying beep that terminals sometimes make.

I run a loop in the background that read the available battery life (Wh) and updates the window manager's display area. Any sensor data can be included in such output.

Finally set the background color and start your favorite window manager.

Switch to an External Monitor

Hopefully your desktop monitor is larger than your laptop display. I use a little docking script to switch to the external display that detects which connection is used and switches the others off

#!/bin/sh

dp() {
    xrandr --output LVDS1 --off
    xrandr --output VGA1 --off
    xrandr --output DP1 --auto
    xrandr --output HDMI1 --off
}

hdmi() {
    xrandr --output LVDS1 --off
    xrandr --output VGA1 --off
    xrandr --output DP1 --off
    xrandr --output HDMI1 --auto
}

set -x
xrandr --query | grep "DP1 connected" && dp
xrandr --query | grep "VGA1 connected" && hdmi
xrandr --query | grep "HDMI1 connected" && hdmi

Connecting to a Projector

If you started X with the VGA connected, it may pick a resolution common to both your screen and the external display. On my T60 it can be reset like so

xrandr --output LVDS --mode 1400x900

Use --query to find out what modes each display supports.

If the external display supports a lower resolution you can set up a viewport that pans with the mouse pointer

xrandr --output VGA-1 --mode 1280x720 --panning 1400x900

Or force both screens to use the same resolution

xrandr --output VGA-1 --mode 1280x720 --output LVDS --mode 1280x720

I also add some additional logic in my .xinitrc to switch to the external display automatically if X is started while connected to an external monitor:

xrandr --query | grep "DVI-1 connected" && ~/bin/docked-dvi
xrandr --query | grep "VGA-1 connected" && ~/bin/docked-vga

tmux

There's only a few tweaks I make to my terminal multiplexor's configuration. I frequently run entr in a smaller pane on the bottom

bind-key C-t split-window -p 25

I don't know of a terminal color picker, but they can be printed with a shell loop.

#!/bin/ksh

for i in `jot 255`; do
  printf "\033[38;5;${i}mcolour${i}\n"
done

Then I set status background and active border to bright green

set -g status-bg colour118
set -g pane-active-border-fg colour118
set -g pane-border-fg colour30

Most importantly, clean up the status bar so that only the window names are displayed:

# remove status debris
set -g status-left ''
set -g status-right ''

Using Disk Encryption

OpenBSD provides software RAID by way of a virtual host bus adapter called softraid0. This HBA is also used for setting up disk encryption. To set use a disklabel (in my case for sd0g /home set the partition type to RAID

$ doas disklabel -E /dev/sd0c
Label editor (enter '?' for help at any prompt)
  g:         55641600        100653824    RAID
> m g
offset: [100653824]
size: [55641600]
FS type: [4.2BSD] RAID

Now configure it for crypto using -c C

# bioctl -c C -l /dev/sd0g softraid0
New passphrase: My Crypto Pass Phrase
Re-type passphrase: My Crypto Pass Phrase
softraid0: CRYPTO volume attached as sd1

Mount it using the same command. The kernel log will show a new virtual device appear

sd1 at scsibus2 targ 1 lun 0: <OPENBSD, SR CRYPTO, 005> SCSI2 0/direct fixed
sd1: 27168MB, 512 bytes/sector, 55641072 sectors

Now add a disklabel and format the encrypted volume

$ doas disklabel -E /dev/wd0c
$ doas newfs /dev/rwd0a

Devices in OpenBSD may be mounted by device name or by disklabel UID which is a random id generated when the label is created.

$ disklabel /dev/sd1c | grep uid
duid: 779d87bac3905122

It's this ID that we'll to mount the volume, in this way plugging in other drives won't confuse mount after we prompt the user for a password on boot. Adding the following to rc.local will ask for a password four times before giving up

#/etc/rc.local
for attept in 1 2 3 4; do
  bioctl -c C -l f878bdbe8655a6eb.k softraid0 && break
  sleep 1
done
fsck -y 0728fd2c8e49bc73.a
mount -o nodev,nosuid,softdep,wxallowed f12a2aa015f390df.a /home

That last mount parameter wxallowed is important because it will allow you to run certain interpreters such as Python from a virtualenv in your home directory.

If you would like to enable crypto on the entire boot volume see this post by Ted Unangst.

Reducing Password Fatique with YubiKey

Yubico makes a nice little hardware key that, among other things, can be used to generate one time passwords for user authentication. The yubikey-personalization-gui is a Qt-based program that can be used to write private keys to one of two "slots". Copy the 6-byte private identity and the 16-byte secret key without spaces to like so

echo "5c e1 e0 3e 63 a4" \
        | tr -d ' ' > /var/db/yubikey/$USER.id
echo "57 e3 af 3e 9b 51 2b 10 58 7d 33 fb d9 08 ef 7b" \
        | tr -d ' ' > /var/db/yubikey/$USER.key
chmod 600 /var/db/yubikey/$USER.*

Now set YubiKey as the authentication method for the group staff by editing /etc/login.conf

- :tc=auth-defaults:
+ :auth=yubikey

If you're a long-time BSD user you might be tempted to run cap_mkdb to rebuild the login DB. You don't need to do this; in fact the new .db file will override local changes to /etc/login.conf.

To reduce typing I use the second slot on the Yubikey as a relatively secure method of enabling ssh-agent in order to connect to remote systems where my public key(s) are installed. To start use the yubikey-personalization-gui to generate a random key, then set slot 2 to challange-response mode with this key

hexkey=$(echo "dd b6 68 81 c9 73 f9 64 84 21 7e f0 69 e8 2c 28 1b 6c ad e2" | tr -d ' ')
ykpersonalize -2 -ochal-resp -ochal-hmac -ohmac-lt64 -a $hexkey

Next I create new ssh keys using part of the reply from ykchalresp. installed script as bin/ykauth

#!/bin/sh
ykchalresp -2 "mysecret" | cut -c 1-15

Finally add this bit of logic to .profile to automatically activate these keys when I log in

ssh-add -l > /dev/null 2>&1 || {
    eval `ssh-agent`
    0<&- SSH_ASKPASS='/home/eradman/bin/ykauth' ssh-add
    exec xinit
}
>

Closing STDIN provokes ssh-add to use the program specified in by SSH_ASKPASS

Screen Lock

Add the following to your .xinitrc to automatically lock the screen after 5 minutes of activity

xidle -timeout 300 -program "/usr/local/bin/slock" &

To trigger this action when the system is suspended, create /etc/apm/suspend with an instruction to signal xidle to run the lock program

#!/bin/sh
pkill -USR1 xidle

Using a custom version of slock it is possible to display a custom image. I like to construct a grayscale and slightly blured image based on what's on the screen when slock was called

gm import -screen :0 -window root /tmp/import.png
gm convert -colorspace Gray -motion-blur 0x4+180 /tmp/import{,2}.png
exec /usr/local/bin/slock -i /tmp/import2.png

unlocked screen

locked screen

Switching Networks

One thing that might not be obvious on BSD is how to switch from one network to another. When switching from wireless to wired for example. First, remove any IP addresses and set the interface down.

ifconfig wpi0 -inet down

Removing the IP address from an interface also drops any link-local or so-called "connected" routes. It may be helpful to nuke all routes.

route -n flush

-n prevents route from trying to resolve hostnames.

If you have set up WPA on your wireless card you can likewise remove the network parameters to obtain a broadcast SSID

 ifconfig wpi0 nwid "Mobile Hotspot" wpa wpakey 09123456789
 ifconfig wpi0 -nwid -wpa -wpakey # use broadcast id

Kerberos & Web Browsers

If your workplace uses Kerberos there is a good chance that they provide the list of KDC servers via DNS SRV records

$ host -t srv _kerberos._udp.eradman.com

Heimdal Kerberos will do this lookup automatically. A basic configuration for /etc/heimdal/krb5.conf appears as such

 [libdefaults]
     ignore_acceptor_hostname = true
     rdns = false
     default_realm = ERADMAN.COM

 [realms]
     ERADMAN.COM = {
             default_domain = ERADMAN.COM
     }

 [domain_realm]
 .ERADMAN.COM = ERADMAN.COM
 ERADMAN.COM = ERADMAN.COM

Now get a ticket

$ kinit
radman@ERADMAN.COM's Password: *********
$ klist
Credentials cache: FILE:/tmp/krb5cc_1000
        Principal: eradman@ERADMAN.COM

  Issued                Expires               Principal
Oct 31 10:02:30 2017  Oct 31 20:02:30 2017  krbtgt/ERADMAN.COM@ERADMAN.COM

Firefox

To enable Firefox to pick use Kerberos we need to point it to the GSSAPI library from the heimdal package. For automated configuration this means installing /usr/local/lib/firefox-56.0/browser/defaults/preferences/openbsd.js

pref("network.negotiate-auth.allow-non-fqdn", true);
pref("network.negotiate-auth.gsslib", "/usr/local/heimdal/lib/libgssapi.so.9.0");
pref("network.negotiate-auth.trusted-uris", "eradman.com");
pref("network.negotiate-auth.using-native-gsslib", false);

Chromium

As of OpenBSD 6.2 Chromium is not built with Kerberos support, but it can be easily added by modifying /usr/ports/www/chromium/Makefile

120c120
<    use_kerberos=false \
-
>    use_kerberos=true \
131
<    extra_cppflags=\"-idirafter ... \"
-
>    extra_cppflags=\"-idirafter /usr/local/heimdal/include ... \"
"

Run make install and a mere 12 hours later the build should be complete. A policy file can be applied for installing the file /etc/chromium/policies/managed/openbsd.json

{
  "AuthServerWhitelist": "*.eradman.com.com"
  "GSSAPILibraryName": "/usr/local/heimdal/lib/libgssapi.so.9.0",
}

If Kerberos does't work, grep for authorization logs in ~/.config/chromium/chrome_debug.log after starting Chromimum with verbose logging enabled

chrome --enable-logging --v 1

Last updated on November 07, 2017