About me: My name is Solène Rapenne. I like learning and sharing my knowledge related to IT stuff. Hobbies: '(BSD OpenBSD h+ Lisp cmdline gaming internet-stuff Crossbow). I love percent and lambda characters. OpenBSD developer solene@.

Contact me: solene on Freenode, solene+www at dataswamp dot org or solene@bsd.network (mastodon). If for some reason you want to give me some money, I accept paypal at the address donate@perso.pw.

OpenBSD ttyplot examples

Written by Solène, on 29 July 2019.
Tags: #openbsd66

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I said I will rewrite ttyplot examples to make them work on OpenBSD.

Here they are, but a small notice before:

Examples using systat will only work for 10000 seconds , or increase that -d parameter, or wrap it in an infinite loop so it restart (but don’t loop systat for one run at a time, it needs to start at least once for producing results).

The systat examples won’t work before OpenBSD 6.6, which is not yet released at the time I’m writing this, but it’ll work on a -current after 20 july 2019.

I made a change to systat so it flush output at every cycle, it was not possible to parse its output in realtime before.

Enjoy!

Examples list

ping

Replace test.example by the host you want to ping.

ping test.example | awk '/ms$/ { print substr($7,6) ; fflush }' | ttyplot -t "ping in ms"

cpu usage

vmstat 1 | awk 'NR>2 { print 100-$(NF); fflush(); }' | ttyplot -t "Cpu usage" -s 100

disk io

 systat -d 1000 -b  iostat 1 | awk '/^sd0/ && NR > 20 { print $2/1024 ; print $3/1024 ; fflush }' | ttyplot -2 -t "Disk read/write in kB/s"

load average 1 minute

{ while :; do uptime ; sleep 1 ; done } | awk '{ print substr($8,0,length($8)-1) ; fflush }' | ttyplot -t "load average 1"

load average 5 minutes

{ while :; do uptime ; sleep 1 ; done } | awk '{ print substr($9,0,length($9)-1) ; fflush }' | ttyplot -t "load average 5"

load average 15 minutes

{ while :; do uptime ; sleep 1 ; done } | awk '{ print $10 ; fflush }' | ttyplot -t "load average 15"

wifi signal strengh

Replace iwm0 by your interface name.

{ while :; do ifconfig iwm0 | tr ' ' '\n' ; sleep 1 ; done } | awk '/%$/ { print ; fflush }' | ttyplot -t "Wifi strength in %" -s 100

cpu temperature

{ while :; do sysctl -n hw.sensors.cpu0.temp0 ; sleep 1 ; done } | awk '{ print $1 ; fflush }' | ttyplot -t "CPU temperature in °C"

pf state searches rate

systat -d 10000 -b pf 1 | awk '/state searches/ { print $4 ; fflush }' | ttyplot -t "PF state searches per second"

pf state insertions rate

systat -d 10000 -b pf 1 | awk '/state inserts/ { print $4 ; fflush }' | ttyplot -t "PF state searches per second"

network bandwidth

Replace trunk0 by your interface. This is the same command as in my previous article.

netstat -b -w 1 -I trunk0 | awk 'NR>3 { print $1/1024; print $2/1024; fflush }' | ttyplot -2 -t "IN/OUT Bandwidth in KB/s" -u "KB/s" -c "#"

Tip

You can easily use those examples over ssh for gathering data, and leave the plot locally as in the following example:

ssh remote_server "netstat -b -w 1 -I trunk0" | awk 'NR>3 { print $1/1024; print $2/1024; fflush }' | ttyplot -2 -t "IN/OUT Bandwidth in KB/s" -u "KB/s" -c "#"

or

ssh remote_server "ping test.example" | awk '/ms$/ { print substr($7,6) ; fflush }' | ttyplot -t "ping in ms"

Realtime bandwidth terminal graph visualization

Written by Solène, on 19 July 2019.
Tags: #openbsd66

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If for some reasons you want to visualize your bandwidth traffic on an interface (in or out) in a terminal with a nice graph, here is a small script to do so, involving ttyplot, a nice software making graphics in a terminal.

The following will works on OpenBSD. You can install ttyplot by pkg_add ttyplot as root, ttyplot package appeared since OpenBSD 6.5.

For Linux, the ttyplot official website contains tons of examples.

Example

Output example while updating my packages:

                                          IN Bandwidth in KB/s
  ↑ 1499.2 KB/s#
  │            #
  │            #
  │            #
  │            ##
  │            ##
  │ 1124.4 KB/s##
  │            ##
  │            ##
  │            ##
  │            ##
  │            ##
  │ 749.6 KB/s ##
  │            ##
  │            ##
  │            ##                                                    #
  │            ##      # #       #                     #             ##
  │            ##  #   ###    # ##      #  #  #        ##            ##         #         # ##
  │ 374.8 KB/s ## ##  ####  # # ## # # ### ## ##      ###  #      ## ###    #   #     #   # ##   #    ##
  │            ## ### ##### ########## #############  ###  # ##  ### ##### #### ##    ## ###### ##    ##
  │            ## ### ##### ########## #############  ###  ####  ### ##### #### ## ## ## ###### ##   ###
  │            ## ### ##### ########## ############## ###  ####  ### ##### #### ## ## ######### ##  ####
  │            ## ### ##### ############################## ######### ##### #### ## ## ############  ####
  │            ## ### #################################################### #### ## #####################
  │            ## ### #################################################### #############################
  └────────────────────────────────────────────────────────────────────────────────────────────────────→
     # last=422.0 min=1.3 max=1499.2 avg=352.8 KB/s                             Fri Jul 19 08:30:25 2019
                                                                           github.com/tenox7/ttyplot 1.4

In the following command, we will use trunk0 with INBOUND traffic as the interface to monitor.

At the end of the article, there is a command for displaying both in and out at the same time, and also instructions for customizing to your need.

Article update: the following command is extremely long and complicated, at the end of the article you can find a shorter and more efficient version, removing most of the awk code.

You can copy/paste this command in your OpenBSD system shell, this will produce a graph of trunk0 inbound traffic.

{ while :; do netstat -i -b -n ; sleep 1 ; done } | awk 'BEGIN{old=-1} /^trunk0/ { if(!index($4,":") && old>=0)  { print ($5-old)/1024 ; fflush  ; old = $5 } if(old==-1) { old=$5 } }'  | ttyplot -t "IN Bandwidth in KB/s" -u "KB/s" -c "#"

The script will do an infinite loop doing netstat -ibn every second and sending that output to awk. You can quit it with Ctrl+C.

Explanations

Netstat output contains total bytes (in or out) since system has started so awk needs to remember last value and will display the difference between two output, avoiding first value because it would make a huge spike (aka the total network transfered since boot time).

If I decompose the awk script, this is a lot more readable. Awk is very readable if you take care to format it properly as any source code!

#!/bin/sh
{ while :;
  do
      netstat -i -b -n
      sleep 1
  done
} | awk '
    BEGIN {
        old=-1
    }
    /^trunk0/ { 
        if(!index($4,":") && old>=0) {
            print ($5-old)/1024
            fflush
            old = $5
        }
        if(old==-1) {
            old = $5
        }
    }' | ttyplot -t "IN Bandwidth in KB/s" -u "KB/s" -c "#"

Customization

  • replace trunk0 by your interface name
  • replace both instances of $5 by $6 for OUT traffic
  • replace /1024 by /1048576 for MB/s values
  • remove /1024 for B/s values
  • replace 1 in sleep 1 by another value if you want to have the value every n seconds

IN/OUT version for both data on the same graph + simpler

Thanks to leot on IRC, netstat can be used in a lot more efficient way and remove all the awk parsing! ttyplot supports having two graphs at the same time, one being in opposite color.

netstat -b -w 1 -I trunk0 | awk 'NR>3 { print $1/1024; print $2/1024; fflush }' | ttyplot -2 -t "IN/OUT Bandwidth in KB/s" -u "KB/s" -c "#"

Streaming to Twitch using OpenBSD

Written by Solène, on 06 July 2019.
Tags: #openbsd66 #gaming

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Introduction

If you ever wanted to make a twitch stream from your OpenBSD system, this is now possible, thanks to OpenBSD developer thfr@ who made a wrapper named fauxstream using ffmpeg with relevant parameters.

The setup is quite easy, it only requires a few steps and searching on Twitch website two informations, hopefully, to ease the process, I found the links for you.

You will need to make an account on twitch, get your api key (a long string of characters) which should stay secret because it allow anyone having it to stream on your account.

Preparation steps

  1. Register / connect on twitch
  2. Get your Stream API key at https://www.twitch.tv/YOUR_USERNAME/dashboard/settings (from this page you can also choose if twitch should automatically saves streams as videos for 14 days)
  3. Choose your nearest server from this page
  4. Add in your shell environnement a variable TWITCH=rtmp://SERVER_FROM_STEP_3/YOUR_API_KEY
  5. Get fauxstream with cvs -d anoncvs@anoncvs.thfr.info:/cvs checkout -P projects/fauxstream/
  6. chmod u+x fauxstream/fauxstream
  7. Allow recording of the microphone
  8. Allow recording of the output sound

Once you have all the pieces, start a new shell and check the $TWITCH variable is correctly set, it should looks like rtmp://live-ams.twitch.tv/app/live_2738723987238_jiozjeoizaeiazheizahezah (this is not a real api key).

Using fauxstream

fauxstream script comes with a README.md file containing some useful informations, you can also check the usage

View usage:

$ ./fauxstream

Starting a stream

When you start a stream, take care your API key isn’t displayed on the stream! I redirect stderr to /dev/null so all the output containing the key is not displayed.

Here is the settings I use to stream:

$ ./fauxstream -m -vmic 5.0 -vmon 0.2 -r 1920x1080 -f 20 -b 4000 $TWITCH 2> /dev/null

If you choose a smaller resolution than your screen, imagine a square of that resolution starting at the top left corner of your screen, the content of this square will be streamed.

I recommend bwm-ng package (I wrote a ports of the week article about it) to view your realtime bandwidth usage, if you see the bandwidth reach a fixed number this mean you reached your bandwidth limit and the stream is certainly not working correctly, you should lower resolution, fps or bitrate.

I recommend doing a few tries before you want to stream, to be sure it’s ok. Note that the flag -a may be be required in case of audio/video desynchronization, there is no magic value so you should guess and try.

Adding webcam

I found an easy trick to add webcam on top of a video game.

$ mpv --no-config --video-sync=display-vdrop --framedrop=vo --ontop av://v4l2:/dev/video1

The trick is to use mpv to display your webcam video on your screen and use the flag to make it stay on top of any other window (this won’t work with cwm(1) window manager). Then you can resize it and place it where you want. What you see is what get streamed.

The others mpv flags are to reduce lag between the webcam video stream and the display, mpv slowly get a delay and after 10 minutes, your webcam will be lagging by like 10 seconds and will be totally out of sync between the action and your face.

Don’t forget to use chown to change the ownership of your video device to your user, by default only root has access to video devices. This is reset upon reboot.

Viewing a stream

For less overhead, people can watch a stream using mpv software, I think this will require youtube-dl package too.

Example to view me streaming:

$ mpv https://www.twitch.tv/seriphyde

This would also work with a recorded video:

$ mpv https://www.twitch.tv/videos/447271018

High quality / low latency VOIP server with umurmur/Mumble on OpenBSD

Written by Solène, on 04 July 2019.
Tags: #openbsd66

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Hello,

I HATE Discord.

Discord users keep telling about their so called discord server, which is not dedicated to them at all. And Discord has a very bad quality and a lot of voice distorsion.

Why not run your very own mumble server with high voice quality and low latency and privacy respect? This is very easy to setup on OpenBSD!

Mumble is an open source voip client, it has a client named Mumble (available on various operating system) and at least Android, the server part is murmur but there is a lightweight server named umurmur. People authentication is done through certificate generated locally and automatically accepted on a server, and the certificate get associated with a nickname. Nobody can pick the same nickname as another person if it’s not the same certificate.

How to install?

# pkg_add umurmur
# rcctl enable umurmurd
# cp /usr/local/share/examples/umurmur/umurmur.conf /etc/umurmur/

We can start it as this, you may want to tweak the configuration file to add a password to your server, or set an admin password, create static channels, change ports etc….

You may want to increase the max_bandwidth value to increase audio quality, or choose the right value to fit your bandwidth. Using umurmur on a DSL line is fine up to 1 or 2 remote people. The daemon uses very little CPU and very little memory. Umurmur is meant to be used on a router!

# rcctl start umurmurd

If you have a restrictive firewall (I hope so), you will have to open the ports TCP and UDP 64738.

How to connect to it?

The client is named Mumble and is packaged under OpenBSD, we need to install it:

# pkg_add mumble

The first time you run it, you will have a configuration wizard that will take only a couple of minutes.

Don’t forget to set the sysctl kern.audio.record to 1 to enable audio recording, as OpenBSD did disable audio input by default a few releases ago.

You will be able to choose a push-to-talk mode or voice level to activate and quality level.

Once the configuration wizard is done, you will have another wizard for generating the certificate. I recommend choosing “Automatically create a certificate”, then validate and it’s done.

You will be prompted for a server, click on “Add new”, enter the name server so you can recognized it easily, type its hostname / IP, its port and your nickname and click OK.

Congratulations, you are now using your own private VOIP server, for real!

Nginx and acme-client on OpenBSD

Written by Solène, on 04 July 2019.
Tags: #openbsd66 #openbsd #nginx

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I write this blog post as I spent too much time setting up nginx and SSL on OpenBSD with acme-client, due to nginx being chrooted and not stripping path and not doing it easily.

First, you need to set up /etc/acme-client.conf correctly. Here is mine for the domain ports.perso.pw:

authority letsencrypt {
        api url "https://acme-v02.api.letsencrypt.org/directory"
        account key "/etc/acme/letsencrypt-privkey.pem"
}

domain ports.perso.pw {
        domain key "/etc/ssl/private/ports.key"
        domain full chain certificate "/etc/ssl/ports.fullchain.pem"
        sign with letsencrypt
}

This example is for OpenBSD 6.6 (which is current when I write this) because of Let’s encrypt API URL. If you are running 6.5 or 6.4, replace v02 by v01 in the api url

Then, you have to configure nginx this way, the most important part in the following configuration file is the location block handling acme-challenge request. Remember that nginx is in chroot /var/www so the path to acme directory is acme.

http {
    include       mime.types;
    default_type  application/octet-stream;
    index         index.html index.htm;
    keepalive_timeout  65;
    server_tokens off;

    upstream backendurl {
        server unix:tmp/plackup.sock;
    }

    server {
      listen       80;
      server_name ports.perso.pw;

      access_log logs/access.log;
      error_log  logs/error.log info;

      root /htdocs/;

      location /.well-known/acme-challenge/ {
          rewrite ^/.well-known/acme-challenge/(.*) /$1 break;
          root /acme;
      } 

      location / {
          return 301 https://$server_name$request_uri;
      }
    }

    server {
      listen 443 ssl;
      server_name ports.perso.pw;
      access_log logs/access.log;
      error_log logs_error.log info;
      root /htdocs/;

      ssl_certificate /etc/ssl/ports.fullchain.pem;
      ssl_certificate_key /etc/ssl/private/ports.key;
      ssl_protocols TLSv1.1 TLSv1.2;
      ssl_prefer_server_ciphers on;
      ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH";

      [... stuff removed ...]
    }

}

That’s all! I wish I could have find that on the Internet so I share it here.

OpenBSD as an IPv6 router

Written by Solène, on 13 June 2019.
Tags: #openbsd66 #openbsd #network

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This blog post is an update (OpenBSD 6.5 at that time) of this very same article I published in June 2018. Due to rtadvd replaced by rad, this text was not useful anymore.

I subscribed to a VPN service from the french association Grifon (Grifon website[FR] to get an IPv6 access to the world and play with IPv6. I will not talk about the VPN service, it would be pointless.

I now have an IPv6 prefix of 48 bits which can theorically have 280 addresses.

I would like my computers connected through the VPN to let others computers in my network to have IPv6 connectivity.

On OpenBSD, this is very easy to do. If you want to provide IPv6 to Windows devices on your network, you will need one more.

In my setup, I have a tun0 device which has the IPv6 access and re0 which is my LAN network.

First, configure IPv6 on your lan:

# ifconfig re0 inet6 autoconf

that’s all, you can add a new line “inet6 autoconf” to your file /etc/hostname.if to get it at boot.

Now, we have to allow IPv6 to be routed through the differents interfaces of the router.

# sysctl net.inet6.ip6.forwarding=1

This change can be made persistent across reboot by adding net.inet6.ip6.forwarding=1 to the file /etc/sysctl.conf.

Automatic addressing

Now we have to configure the daemon rad to advertise the we are routing, devices on the network should be able to get an IPv6 address from its advertisement.

The minimal configuration of /etc/rad.conf is the following:

interface re0 {
    prefix 2a00:5414:7311::/48
}

In this configuration file we only define the prefix available, this is equivalent to a dhcp addresses range. Others attributes could provide DNS servers to use for example, see rad.conf man page.

Then enable the service at boot and start it:

# rcctl enable rad
# rcctl start rad

Tweaking resolv.conf

By default OpenBSD will ask for IPv4 when resolving a hostname (see resolv.conf(5) for more explanations). So, you will never have IPv6 traffic until you use a software which will request explicit IPv6 connection or that the hostname is only defined with a AAAA field.

# echo "family inet6 inet4" >> /etc/resolv.conf.tail

The file resolv.conf.tail is appended at the end of resolv.conf when dhclient modifies the file resolv.conf.

Microsoft Windows

If you have Windows systems on your network, they won’t get addresses from rad. You will need to deploy dhcpv6 daemon.

The configuration file for what we want to achieve here is pretty simple, it consists of telling what range we want to allow on DHCPv6 and a DNS server. Create the file /etc/dhcp6s.conf:

interface re0 {
    address-pool pool1 3600;
};
pool pool1 {
    range 2a00:5414:7311:1111::1000 to 2a00:5414:7311:1111::4000;
};
option domain-name-servers 2001:db8::35;

Note that I added “1111” into the range because it should not be on the same network than the router. You can replace 1111 by what you want, even CAFE or 1337 if you want to bring some fun to network engineers.

Now, you have to install and configure the service:

# pkg_add wide-dhcpv6
# touch /etc/dhcp6sctlkey
# chmod 400 /etc/dhcp6sctlkey
# echo SOME_RANDOM_CHARACTERS | openssl enc -base64 > /etc/dhcp6sctlkey
# echo "dhcp6s -c /etc/dhcp6s.conf re0" >> /etc/rc.local

The openbsd package wide-dhcpv6 doesn’t provide a rc file to start/stop the service so it must be started from a command line, a way to do it is to type the command in /etc/rc.local which is run at boot.

The openssl command is needed for dhcpv6 to start, as it requires a base64 string as a secret key in the file /etc/dhcp6sctlkey.

Fun tip #3: Split a line using ed

Written by Solène, on 04 December 2018.
Tags: #fun-tip #unix #openbsd66

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In this new article I will explain how to programmaticaly a line (with a newline) using ed.

We will use commands sent to ed in its stdin to do so. The logic is to locate the part where to add the newline and if a character need to be replaced.

this is a file
with a too much line in it that should be split
but not this one.

In order to do so, we will format using printf(1) the command list using a small trick to insert the newline. The command list is the following:

/too much line
s/that /that
,p

This search the first line matching “too much line” and then replaced “that ” by "that0, the trick is to escape using a backslash so the substitution command can accept the newline, and at the end we print the file (replace ,n by w to write it).

The resulting command line is:

$ printf '/too much line0/that /that\0n0 | ed file.txt
81
> with a too much line in it that should be split
> should be split
> 1     this is a file
2       with a too much line in it that
3       should be split
4       but not this one.
> ?

Fun tip #2: Display trailing spaces using ed

Written by Solène, on 29 November 2018.
Tags: #unix #fun-tip #openbsd66

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This second fun-tip article will explain how to display trailing spaces in a text file, using the ed(1) editor. ed has a special command for showing a dollar character at the end of each line, which mean that if the line has some spaces, the dollar character will spaced from the last visible line character.

$ echo ",pl" | ed some-file.txt
453
This second fun-tip article will explain how to display trailing$
spaces in a text file, using the$
[ed(1)$](https://man.openbsd.org/ed)
editor.$
ed has a special command for showing a dollar character at the end of$
each line, which mean that if the line has some spaces, the dollar$
character will spaced from the last visible line character.$
$
.Bd -literal -offset indent$
echo ",pl" | ed some-file.txt$

This is the output of the article file while I am writing it. As you can notice, there is no trailing space here.

The first number shown in the ed output is the file size, because ed starts at the end of the file and then, wait for commands.

If I use that very same command on a small text files with trailing spaces, the following result is expected:

49
this is full    $
of trailing  $
spaces      !    $

It is also possible to display line numbers using the “n” command instead of the “p” command. This would produce this result for my current article file:

1559
1       .Dd November 29, 2018$
2       .Dt "Show trailing spaces using ed"$
3       This second fun-tip article will explain how to display trailing$
4       spaces in a text file, using the$
5       .Lk https://man.openbsd.org/ed ed(1)$
6       editor.$
7       ed has a special command for showing a dollar character at the end of$
8       each line, which mean that if the line has some spaces, the dollar$
9       character will spaced from the last visible line character.$
10      $
11      .Bd -literal -offset indent$
12      echo ",pl" | ed some-file.txt$
13      453$
14      .Dd November 29, 2018
15      .Dt "Show trailing spaces using ed"
16      This second fun-tip article will explain how to display trailing
17      spaces in a text file, using the
18      .Lk https://man.openbsd.org/ed ed(1)
19      editor.
20      ed has a special command for showing a '\ character at the end of
21      each line, which mean that if the line has some spaces, the '\
22      character will spaced from the last visible line character.
23
24      \&.Bd \-literal \-offset indent
25      \echo ",pl" | ed some-file.txt
26      .Ed$
27      $
28      This is the output of the article file while I am writing it. As you$
29      can notice, there is no trailing space here.$
30      $
31      The first number shown in the ed output is the file size, because ed$
32      starts at the end of the file and then, wait for commands.$
33      $
34      If I use that very same command on a small text files with trailing$
35      spaces, the following result is expected:$
36      $
37      .Bd -literal -offset indent$
38      49$
39      this is full
40      of trailing
41      spaces      !
42      .Ed$
43      $
44      It is also possible to display line numbers using the "n" command$
45      instead of the "p" command.$
46      This would produce this result for my current article file:$
47      .Bd -literal -offset indent$

This shows my article file with each line numbered plus the position of the last character of each line, this is awesome!

I have to admit though that including my own article as example is blowing up my mind, especially as I am writing it using ed.

Tor part 6: onionshare for sharing files anonymously

Written by Solène, on 21 November 2018.
Tags: #tor #unix #network #openbsd66

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If for some reasons you need to share a file anonymously, this can be done through Tor using the port net/onionshare. Onionshare will start a web server displaying an unique page with a list of shared files and a Download Files button leading to a zip file.

While waiting for a download, onionshare will display HTTP logs. By default, onionshare will exit upon successful download of the files but this can be changed with the flag –stay-open.

Its usage is very simple, execute onionshare with the list of files to share, as you can see in the following example:

solene@computer ~ $ onionshare Epictetus-The_Enchiridion.txt
Onionshare 1.3 | https://onionshare.org/
Connecting to the Tor network: 100% - Done
Configuring onion service on port 17616.
Starting ephemeral Tor onion service and awaiting publication
Settings saved to /home/solene/.config/onionshare/onionshare.json
Preparing files to share.
 * Running on http://127.0.0.1:17616/ (Press CTRL+C to quit)
Give this address to the person you're sending the file to:
http://3ngjewzijwb4znjf.onion/hybrid-marbled

Press Ctrl-C to stop server

Now, I need to give the address http://3ngjewzijwb4znjf.onion/hybrid-marbled to the receiver who will need a web browser with Tor to download it.

Tor part 5: onioncat for IPv6 VPN over tor

Written by Solène, on 13 November 2018.
Tags: #tor #unix #network #openbsd66

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This article is about a software named onioncat, it is available as a package on most Unix and Linux systems. This software allows to create an IPv6 VPN over Tor, with no restrictions on network usage.

First, we need to install onioncat, on OpenBSD:

$ doas pkg_add onioncat

Run a tor hidden service, as explained in one of my previous article, and get the hostname value. If you run multiples hidden services, pick one hostname.

# cat /var/tor/ssh_hidden_service/hostname
g6adq2w15j1eakzr.onion

Now that we have the hostname, we just need to run ocat.

# ocat g6adq2w15j1eakzr.onion

If everything works as expected, a tun interface will be created. With a fe80:: IPv6 address assigned to it, and a fd87:: address.

Your system is now reachable, via Tor, through its IPv6 address starting with fd87:: . It supports every IP protocol. Instead of using torsocks wrapper and .onion hostname, you can use the IPv6 address with any software.

Fun tip #1: Apply a diff with ed

Written by Solène, on 13 November 2018.
Tags: #fun-tip #unix #openbsd66

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I am starting a new kind of articles that I chose to name it ”fun facts“. Theses articles will be about one-liners which can have some kind of use, or that I find interesting from a technical point of view. While not useless, theses commands may be used in very specific cases.

The first of its kind will explain how to programmaticaly use diff to modify file1 to file2, using a command line, and without a patch.

First, create a file, with a small content for the example:

$ printf "first line\nsecond line\nthird line\nfourth line with text\n" > file1
$ cp file1{,.orig}
$ printf "very first line\nsecond line\n third line\nfourth line\n" > file1

We will use diff(1) -e flag with the two files.

$ diff -e file1 file1.orig
4c
fourth line
.
1c
very first line
.

The diff(1) output is batch of ed(1) commands, which will transform file1 into file2. This can be embedded into a script as in the following example. We also add w last commands to save the file after edition.

#!/bin/sh
ed file1 <<EOF
4c
fourth line
.
1c
very first line
.
w
EOF

This is a quite convenient way to transform a file into another file, without pushing the entire file. This can be used in a deployment script. This is more precise and less error prone than a sed command.

In the same way, we can use ed to alter configuration file by writing instructions without using diff(1). The following script will change the whole first line containing “Port 22” into Port 2222 in /etc/ssh/sshd_config.

#!/bin/sh
ed /etc/ssh/sshd_config <<EOF
/Port 22
c
Port 2222
.
w
EOF

The sed(1) equivalent would be:

sed -i'' 's/.*Port 22.*/Port 2222/' /etc/ssh/sshd_config

Both programs have their use, pros and cons. The most important is to use the right tool for the right job.

Play Stardew Valley on OpenBSD

Written by Solène, on 09 November 2018.
Tags: #games #openbsd66

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It’s possible to play native Stardew Valley on OpenBSD, and it’s not using a weird trick!

First, you need to buy Stardew Valley, it’s not very expensive and is often available at a lower price. I recommend to buy it on GOG.

Now, follow the steps:

  1. install packages unzip and fnaify
  2. On GOG, download the linux installer
  3. unzip the installer (use unzip command on the .sh file)
  4. cd into data/noarch/game
  5. fnaify -y
  6. ./StardewValley

Enjoy!

Safely restrict commands through SSH

Written by Solène, on 08 November 2018.
Tags: #ssh #security #openbsd66 #highlight

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sshd(8) has a very nice feature that is often overlooked. That feature is the ability to allow a ssh user to run a specified command and nothing else, not even a login shell.

This is really easy to use and the magic happens in the file authorized_keys which can be used to restrict commands per public key.

For example, if you want to allow someone to run the “uptime” command on your server, you can create a user account for that person, with no password so the password login will be disabled, and add his/her ssh public key in ~/.ssh/authorized_keys of that new user, with the following content.

restrict,command="/usr/bin/uptime" ssh-rsa the_key_content_here

The user will not be able to log-in, and doing the command ssh remoteserver will return the output of uptime. There is no way to escape this.

While running uptime is not really helpful, this can be used for a much more interesting use case, like allowing remote users to use vmctl without giving a shell account. The vmctl command requires parameters, the configuration will be slightly different.

restrict,pty,command="/usr/sbin/vmctl $SSH_ORIGINAL_COMMAND" ssh-rsa the_key_content_here"

The variable SSH_ORIGINAL_COMMAND contains the value of what is passed as parameter to ssh. The pty keyword also make an appearance, that will be explained later.

If the user connects to ssh, vmctl with no parameter will be output.

$ ssh remotehost
usage:  vmctl [-v] command [arg ...]
    vmctl console id
    vmctl create "path" [-b base] [-i disk] [-s size]
    vmctl load "path"
    vmctl log [verbose|brief]
    vmctl reload
    vmctl reset [all|vms|switches]
    vmctl show [id]
    vmctl start "name" [-Lc] [-b image] [-r image] [-m size]
            [-n switch] [-i count] [-d disk]* [-t name]
    vmctl status [id]
    vmctl stop [id|-a] [-fw]
    vmctl pause id
    vmctl unpause id
    vmctl send id
    vmctl receive id

If you pass parameters to ssh, it will be passed to vmctl.

$ ssh remotehost show
   ID   PID VCPUS  MAXMEM  CURMEM     TTY        OWNER NAME
1     -     1    1.0G       -       -       solene test
$ ssh remotehost start test
vmctl: started vm 1 successfully, tty /dev/ttyp9
$ ssh -t remotehost console test
(I)nstall, (U)pgrade, (A)utoinstall or (S)hell?

The ssh connections become a call to vmctl and ssh parameters become vmctl parameters.

Note that in the last example, I use “ssh -t”, this is so to force allocation of a pseudo tty device. This is required for vmctl console to get a fully working console. The keyword restrict does not allow pty allocation, that is why we have to add pty after restrict, to allow it.

File versioning with rcs

Written by Solène, on 31 October 2018.
Tags: #openbsd66 #highlight #unix

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In this article I will present you the rcs tools and we will use it for versioning files in /etc to track changes between editions. These tools are part of the OpenBSD base install.

Prerequisites

You need to create a RCS folder where your files are, so the files versions will be saved in it. I will use /etc in the examples, you can adapt to your needs.

# cd /etc
# mkdir RCS

The following examples use the command ci -u. This will be explained later why so.

Tracking a file

We need to add a file to the RCS directory so we can track its revisions. Each time we will proceed, we will create a new revision of the file which contain the whole file at that point of time. This will allow us to see changes between revisions, and the date of each revision (and some others informations).

I really recommend to track the files you edit in your system, or even configuration file in your user directory.

In next example, we will create the first revision of our file with ci, and we will have to write some message about it, like what is doing that file. Once we write the message, we need to validate with a single dot on the line.

# cd /etc
# ci -u fstab
fstab,v  <--  fstab
enter description, terminated with single '.' or end of file:
NOTE: This is NOT the log message!
>> this is the /etc/fstab file
>> .
initial revision: 1.1
done

Editing a file

The process of edition has multiples steps, using ci and co:

  1. checkout the file and lock it, this will make the file available for writing and will prevent using co on it again (due to lock)
  2. edit the file
  3. commit the new file + checkout

When using ci to store the new revision, we need to write a small message, try to use something clear and short. The log messages can be seen in the file history, that should help you to know which change has been made and why. The full process is done in the following example.

# co -l fstab
RCS/fstab,v  -->  fstab
revision 1.1 (locked)
done
# echo "something wrong" >> fstab
# ci -u fstab
RCS/fstab,v  <--  fstab
new revision: 1.4; previous revision: 1.3
enter log message, terminated with a single '.' or end of file:
>> I added a mistake on purpose!
>> .
revision 1.4 (unlocked)
done

View changes since last version

Using previous example, we will use rcsdiff to check the changes since the last version.

# co -l fstab
RCS/fstab,v  -->  fstab
revision 1.1 (locked)
done
# echo "something wrong" >> fstab
# rcsdiff -u fstab
--- fstab   2018/10/28 14:28:29 1.1
+++ fstab   2018/10/28 14:30:41
@@ -9,3 +9,4 @@
 52fdd1ce48744600.j /usr/src ffs rw,nodev,nosuid 1 2
 52fdd1ce48744600.e /var ffs rw,nodev,nosuid 1 2
 52fdd1ce48744600.m /data ffs rw,dev,wxallowed,nosuid 1 2
+something wrong

The -u flag is so to produce an unified diff, which I find easier to read. Lines with + shows additions, and lines with - show deletions (there are none in the example).

Use of ci -u

The examples were using ci -u this is because, if you use ci some_file, the file will be saved in the RCS folder but will be missing in its place. You should use co some_file to get it back (in read-only).

# co -l fstab
RCS/fstab,v  -->  fstab
revision 1.1 (locked)
done
# echo "something wrong" >> fstab
# ci -u fstab
RCS/fstab,v  <--  fstab
new revision: 1.4; previous revision: 1.3
enter log message, terminated with a single '.' or end of file:
>> I added a mistake on purpose!
>> .
done
# ls fstab
ls: fstab: No such file or directory
# co fstab
RCS/fstab,v  -->  fstab
revision 1.5
done
# ls fstab
fstab

Using ci -u is very convenient because it prevent the user to forget to checkout the file after commiting the changes.

Show existing revisions of a file

# rlog fstab
RCS file: RCS/fstab,v
Working file: fstab
head: 1.2
branch:
locks: strict
access list:
symbolic names:
keyword substitution: kv
total revisions: 2;     selected revisions: 2
description:
new file
----------------------------
revision 1.2
date: 2018/10/28 14:45:34;  author: solene;  state: Exp;  lines: +1 -0;
Adding a disk
----------------------------
revision 1.1
date: 2018/10/28 14:45:18;  author: solene;  state: Exp;
Initial revision
=============================================================================

We have revisions 1.1 and 1.2, if we want to display the file in its 1.1 revision, we can use the following command:

# co -p1.1 fstab
RCS/fstab,v  -->  standard output
revision 1.1
52fdd1ce48744600.b none swap sw
52fdd1ce48744600.a / ffs rw 1 1
52fdd1ce48744600.l /home ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.d /tmp ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.f /usr ffs rw,nodev 1 2
52fdd1ce48744600.g /usr/X11R6 ffs rw,nodev 1 2
52fdd1ce48744600.h /usr/local ffs rw,wxallowed,nodev 1 2
52fdd1ce48744600.k /usr/obj ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.j /usr/src ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.e /var ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.m /data ffs rw,dev,wxallowed,nosuid 1 2
done

Note that there is no space between the flag and the revision! This is required.

We can see that the command did output some extra informations about the file and “done” at the end of the file. Thoses extra informations are sent to stderr while the actual file content is sent to stdout. That mean if we redirect stdout to a file, we will get the file content.

# co -p1.1 fstab > a_file
RCS/fstab,v  -->  standard output
revision 1.1
done
# cat a_file
52fdd1ce48744600.b none swap sw
52fdd1ce48744600.a / ffs rw 1 1
52fdd1ce48744600.l /home ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.d /tmp ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.f /usr ffs rw,nodev 1 2
52fdd1ce48744600.g /usr/X11R6 ffs rw,nodev 1 2
52fdd1ce48744600.h /usr/local ffs rw,wxallowed,nodev 1 2
52fdd1ce48744600.k /usr/obj ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.j /usr/src ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.e /var ffs rw,nodev,nosuid 1 2
52fdd1ce48744600.m /data ffs rw,dev,wxallowed,nosuid 1 2

Show a diff of a file since a revision

We can use rcsdiff using -r flag to tell it to show the changes between last and one specific revision.

# rcsdiff -u -r1.1 fstab
--- fstab   2018/10/29 14:45:18 1.1
+++ fstab   2018/10/29 14:45:34
@@ -9,3 +9,4 @@
 52fdd1ce48744600.j /usr/src ffs rw,nodev,nosuid 1 2
 52fdd1ce48744600.e /var ffs rw,nodev,nosuid 1 2
 52fdd1ce48744600.m /data ffs rw,dev,wxallowed,nosuid 1 2
+something wrong

Configure OpenSMTPD to relay on a network

Written by Solène, on 29 October 2018.
Tags: #openbsd66 #highlight #opensmtpd

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With the new OpenSMTPD syntax change which landed with OpenBSD 6.4 release, changes are needed for making opensmtpd to act as a lan relay to a smtp server. This case wasn’t covered in my previous article about opensmtpd, I was only writing about relaying from the local machine, not for a network. Mike (a reader of the blog) shared that it would be nice to have an article about it. Here it is! :)

A simple configuration would look like the following:

listen on em0
listen on lo0

table aliases db:/etc/mail/aliases.db
table secrets db:/etc/mail/secrets.db

action "local" mbox alias <aliases>
action "relay" relay host smtps://myrelay@remote-smtpd.tld auth <secrets>

match for local action "local"
match from local for any action "relay"
match from src 192.168.1.0/24 for action relay

The daemon will listen on em0 interface, and mail delivered from the network will be relayed to remote-smtpd.tld.

For a relay using authentication, the login and passwords must be defined in the file /etc/mail/secrets like this: myrelay login:Pa$$W0rd

smtpd.conf(5) explains creation of /etc/mail/secrets like this:

touch /etc/mail/secrets
chmod 640 /etc/mail/secrets
chown root:_smtpd /etc/mail/secrets

Tor part 3: Tor Browser

Written by Solène, on 24 October 2018.
Tags: #openbsd66 #openbsd #unix #tor

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In this third Tor article, we will discover the web browser Tor Browser.

The Tor Browser is an official Tor project. It is a modified Firefox, including some defaults settings changes and some extensions. The default changes are all related to privacy and anonymity. It has been made to be easy to browse the Internet through Tor without leaving behing any information which could help identify you, because there are much more informations than your public IP address which could be used against you.

It requires tor daemon to be installed and running, as I covered in my first Tor article.

Using it is really straightforward.

How to install tor-browser

$ pkg_add tor-browser

How to start tor-browser

$ tor-browser

It will create a ~/TorBrowser-Data folder at launch. You can remove it as you want, it doesn’t contain anything sensitive but is required for it to work.

Show OpenSMTPD queue and force sending queued mails

Written by Solène, on 24 October 2018.
Tags: #opensmtpd #highlight #openbsd66 #openbsd

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If you are using opensmtpd on a device not always connected on the internet, you may want to see what mail did not go, and force it to be delivered NOW when you are finally connected to the Internet.

We can use smtpctl to show the current queue.

$ doas smtpctl show queue
1de69809e7a84423|local|mta|auth|so@tld|dest@tld|dest@tld|1540362112|1540362112|0|2|pending|406|No MX found for domain

The previous command will report nothing if the queue is empty.

In the previous output, we see that there is one mail from me to dest@tld which is pending due to “NO MX found for domain” (which is normal as I had no internet when I sent the mail).

We need to extract the first field, which is 1de69809e7a84423 in the current example.

In order to tell opensmtpd to deliver it now, we will use the following command:

$ doas smtpctl schedule 1de69809e7a84423
1 envelope scheduled
$ doas smtpctl show queue

My mail was delivered, it’s not in the queue anymore.

If you wish to deliver all enveloppes in the queue, this is as simple as:

$ doas smtpctl schedule all

Tor part 2: hidden service

Written by Solène, on 11 October 2018.
Tags: #openbsd66 #openbsd #unix #tor #security

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In this second Tor article, I will present an interesting Tor feature named hidden service. The principle of this hidden service is to make available a network service from anywhere, with only prerequisites that the computer must be powered on, tor not blocked and it has network access.

This service will be available through an address not disclosing anything about the server internet provider or its IP, instead, a hostname ending by .onion will be provided by tor for connecting. This hidden service will be only accessible through Tor.

There are a few advantages of using hidden services:

  • privacy, hostname doesn’t contain any hint
  • security, secure access to a remote service not using SSL/TLS
  • no need for running some kind of dynamic dns updater

The drawback is that it’s quite slow and it only work for TCP services.

From here, we assume that Tor is installed and working.

Running an hidden service require to modify the Tor daemon configuration file, located in /etc/tor/torrc on OpenBSD.

Add the following lines in the configuration file to enable a hidden service for SSH:

HiddenServiceDir /var/tor/ssh_service
HiddenServicePort 22 127.0.0.1:22

The directory /var/tor/ssh_service will be be created. The directory /var/tor is owned by user _tor and not readable by other users. The hidden service directory can be named as you want, but it should be owned by user _tor with restricted permissions. Tor daemon will take care at creating the directory with correct permissions once you reload it.

Now you can reload the tor daemon to make the hidden service available.

$ doas rcctl reload tor

In the /var/tor/ssh_service directory, two files are created. What we want is the content of the file hostname which contains the hostname to reach our hidden service.

$ doas cat /var/tor/ssh_service/hostname
piosdnzecmbijclc.onion

Now, we can use the following command to connect to the hidden service from anywhere.

$ torsocks ssh piosdnzecmbijclc.onion

In Tor network, this feature doesn’t use an exit node. Hidden services can be used for various services like http, imap, ssh, gopher etc…

Using hidden service isn’t illegal nor it makes the computer to relay tor network, as previously, just check if you can use Tor on your network.

Note: it is possible to have a version 3 .onion address which will prevent hostname collapsing, but this produce very long hostnames. This can be done like in the following example:

HiddenServiceDir /var/tor/ssh_service
HiddenServicePort 22 127.0.0.1:22
HiddenServiceVersion 3

This will produce a really long hostname like tgoyfyp023zikceql5njds65ryzvwei5xvzyeubu2i6am5r5uzxfscad.onion

If you want to have the short and long hostnames, you need to specify twice the hidden service, with differents folders.

Take care, if you run a ssh service on your website and using this same ssh daemon on the hidden service, the host keys will be the same, implying that someone could theoricaly associate both and know that this public IP runs this hidden service, breaking anonymity.

Tor part 1: how-to use Tor

Written by Solène, on 10 October 2018.
Tags: #openbsd66 #openbsd #unix #tor #security

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Tor is a network service allowing to hide your traffic. People sniffing your network will not be able to know what server you reach and people on the remote side (like the administrator of a web service) will not know where you are from. Tor helps keeping your anonymity and privacy.

To make it quick, tor make use of an entry point that you reach directly, then servers acting as relay not able to decrypt the data relayed, and up to an exit node which will do the real request for you, and the network response will do the opposite way.

You can find more details on the Tor project homepage.

Installing tor is really easy on OpenBSD. We need to install it, and start its daemon. The daemon will listen by default on localhost on port 9050. On others systems, it may be quite similar, install the tor package and enable the daemon if not enabled by default.

# pkg_add tor
# rcctl enable tor
# rcctl start tor

Now, you can use your favorite program, look at the proxy settings and choose “SOCKS” proxy, v5 if possible (it manage the DNS queries) and use the default address: 127.0.0.1 with port 9050.

If you need to use tor with a program that doesn’t support setting a SOCKS proxy, it’s still possible to use torsocks to wrap it, that will work with most programs. It is very easy to use.

# pkg_add torsocks
$ torsocks ssh remoteserver

This will make ssh going through tor network.

Using tor won’t make you relaying anything, and is legal in most countries. Tor is like a VPN, some countries has laws about VPN, check for your country laws if you plan to use tor. Also, note that using tor may be forbidden in some networks (companies, schools etc..) because this allows to escape filtering which may be against some kind of “Agreement usage” of the network.

I will cover later the relaying part, which can lead to legal uncertainty.

Note: as torsocks is a bit of a hack, because it uses LD_PRELOAD to wrap network system calls, there is a way to do it more cleanly with ssh (or any program supporting a custom command for initialize the connection) using netcat.

ssh -o ProxyCommand='/usr/bin/nc -X 5 -x 127.0.0.1:9050 %h %p' address.onion

This can be simplified by adding the following lines to your ~/.ssh/config file, in order to automatically use the proxy command when you connect to a .onion hostname:

Host *.onion
ProxyCommand='/usr/bin/nc -X 5 -x 127.0.0.1:9050 %h %p'

This netcat command is tested under OpenBSD, there are differents netcat implementations, the flags may be differents or may not even exist.

Add an new OpenBSD partition from unused space

Written by Solène, on 20 September 2018.
Tags: #openbsd66 #openbsd #highlight

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The default OpenBSD partition layout uses a pre-defined template. If you have a disk more than 356 GB you will have unused space with the default layout (346 GB before 6.4).

It’s possible to create a new partition to use that space if you did not modify the default layout at installation. You only need to start disklabel with flag -E* and type a to add a partition, default will use all remaining space for the partition.

# disklabel -E sd0
Label editor (enter '?' for help at any prompt)
> a
partition: [m]
offset: [741349952]
size: [258863586]
FS type: [4.2BSD]
> w
> q
No label changes.

The new partition here is m. We can format it with:

# newfs /dev/rsd0m

Then, you should add it to your /etc/fstab, for that, use the same uuid as for other partitions, it would look something like 52fdd1ce48744600

52fdd1ce48744600.e /data ffs rw,nodev,nosuid 1 2

It will be auto mounted at boot, you only need to create the folder /data. Now you can do

# mkdir /data
# mount /data

and /data is usable right now.

You can read disklabel(8) and newfs for more informations.

Display the size of installed packages ordered by size

Written by Solène, on 11 September 2018.
Tags: #openbsd66 #openbsd #highlight

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Simple command line to display your installed packages listed by size from smallest to biggest.

$ pkg_info -sa | paste - - - - | sort -n -k 5

Thanks to sthen@ for the command, I was previously using one involving awk which was less readable. paste is often forgotten, it has very specifics uses which can’t be mimic easily with other tools, its purpose is to joins multiples lines into one with some specific rules.

You can easily modify the output to convert the size from bytes to megabytes with awk:

$ pkg_info -sa | paste - - - - | sort -n -k 5 | awk '{ NF=$NF/1024/1024 ; print }'

This divides the last element (using space separator) of each line twice by 1024 and displays the line.

Manage ”nice” priority of daemons on OpenBSD

Written by Solène, on 11 September 2018.
Tags: #openbsd66 #openbsd #highlight

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Following a discussion on the OpenBSD mailing list misc, today I will write about how to manage the priority (as in nice priority) of your daemons or services.

In man page rc(8), one can read:

Before init(8) starts rc, it sets the process priority, umask, and
resource limits according to the “daemon” login class as described in
login.conf(5).  It then starts rc and attempts to execute the sequence of
commands therein.

Using /etc/login.conf we can manage some limits for services and daemon, using their rc script name.

For example, to make jenkins at lowest priority (so it doesn’t make troubles if it builds), using this line will set it to nice 20.

jenkins:priority=20

If you have a file /etc/login.conf.db you have to update it from /etc/login.conf using the software cap_mkdb. This creates a hashed database for faster information retrieval when this file is big. By default, that file doesn’t exist and you don’t have to run cap_mkdb. See login.conf(5) for more informations.

Configuration of OpenSMTPD to relay mails to outbound smtp server

Written by Solène, on 06 September 2018.
Tags: #openbsd66 #openbsd #opensmtpd #highlight

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In this article I will show how to configure OpenSMTPD, the default mail server on OpenBSD, to relay mail sent locally to your smtp server. In pratice, this allows to send mail through “localhost” by the right relay, so it makes also possible to send mail even if your computer isn’t connected to the internet. Once connected, opensmtpd will send the mails.

All you need to understand the configuration and write your own one is in the man page smtpd.conf(5). This is only a highlight on was it possible and how to achieve it.

In OpenBSD 6.4 release, the configuration of opensmtpd changed drasticaly, now you have to defines rules and action to do when a mail match the rules, and you have to define those actions.

In the following example, we will see two kinds of relay, the first is through smtp over the Internet, it’s the most likely you will want to setup. And the other one is how to relay to a remote server not allowing relaying from outside.

/etc/mail/smtpd.conf

table aliases file:/etc/mail/aliases
table secrets file:/etc/mail/secrets
listen on lo0

action "local" mbox alias <aliases>
action "relay" relay
action "myserver" relay host smtps://myrelay@perso.pw auth <secrets>
action "openbsd"  relay host localhost:2525

match mail-from "@perso.pw"    for any action "myserver"
match mail-from "@openbsd.org" for any action "openbsd"
match for local action "local"
match for any action "relay"

I defined 2 actions, one from “myserver”, it has a label “myrelay” and we use auth <secrets> to tell opensmtpd it needs authentication.

The other action is “openbsd”, it will only relay to localhost on port 2525.

To use them, I define 2 matching rules of the very same kind. If the mail that I want to send match the @domain-name, then choose relay “myserver” or “openbsd”.

The “openbsd” relay is only available when I create a SSH tunnel, binding the local port 25 of the remote server to my port 2525, with flags -L 2525:127.0.0.1:25.

For a relay using authentication, the login and passwords must be defined in the file /etc/mail/secrets like this: myrelay login:Pa$$W0rd

smtpd.conf(5) explains creation of /etc/mail/secrets like this:

touch /etc/mail/secrets
chmod 640 /etc/mail/secrets
chown root:_smtpd /etc/mail/secrets

Now, restarts your server. Then if you need to send mails, just use “mail” command or localhost as a smtp server. Depending on your From address, a different relay will be used.

Deliveries can be checked in /var/log/maillog log file.

See mails in queue

doas smtpctl show queue

Try to deliver now

doas smtpctl schedule all

Automatic switch wifi/ethernet on OpenBSD

Written by Solène, on 30 August 2018.
Tags: #openbsd66 #openbsd #network #highlight

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Today I will cover a specific topic on OpenBSD networking. If you are using a laptop, you may switch from ethernet to wireless network from time to time. There is a simple way to keep the network instead of having to disconnect / reconnect everytime.

It’s possible to aggregate your wireless and ethernet devices into one trunk pseudo device in failover mode, which give ethernet the priority if connected.

To achieve this, it’s quite simple. If you have devices em0 and iwm0 create the following files.

/etc/hostname.em0

up

/etc/hostname.iwm0

join "office_network"  wpakey "mypassword"
join "my_home_network" wpakey "9charshere"
join "roaming phone"   wpakey "something"
join "Public Wifi"
up

/etc/hostname.trunk0

trunkproto failover trunkport em0 trunkport iwm0
dhcp

As you can see in the wireless device configuration we can specify multiples network to join, it is a new feature that will be available from 6.4 release.

You can enable the new configuration by running sh /etc/netstart as root.

This setup is explained in trunk(4) man page and in the OpenBSD FAQ as well.

Easy encrypted backups on OpenBSD with base tools

Written by Solène, on 26 June 2018.
Tags: #unix #openbsd66 #openbsd

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Old article

Hello, it turned out that this article is obsolete. The security used in is not safe at all so the goal of this backup system isn’t achievable, thus it should not be used and I need another backup system.

One of the most important feature of dump for me was to keep track of the inodes numbers. A solution is to save the list of the inodes numbers and their path in a file before doing a backup. This can be achieved with the following command.

$ doas ncheck -f "\I \P\n" /var

If you need a backup tool, I would recommend the following:

Duplicity

It supports remote backend like ftp/sftp which is quite convenient as you don’t need any configuration on this other side. It supports compression and incremental backup. I think it has some GUI tools available.

Restic

It supports remote backend like cloud storage provider or sftp, it doesn’t require any special tool on the remote side. It supports deduplication of the files and is able to manage multiples hosts in the same repository, this mean that if you backup multiple computers, the deduplication will work across them. This is the only backup software I know allowing this (I do not count backuppc which I find really unusable).

Borg

It supports remote backend like ssh only if borg is installed on the other side. It supports compression and deduplication but it is not possible to save multiples hosts inside the same repository without doing a lot of hacks (which I won’t recommend).

Mount a folder on another folder

Written by Solène, on 22 May 2018.
Tags: #openbsd66 #openbsd

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This article will explain quickly how to bind a folder to access it from another path. It can be useful to give access to a specific folder from a chroot without moving or duplicating the data into the chroot.

Real world example: “I want to be able to access my 100GB folder /home/my_data/ from my httpd web server chrooted in /var/www/”.

The trick on OpenBSD is to use NFS on localhost. It’s pretty simple.

# rcctl enable portmap nfsd mountd
# echo "/home/my_data -network=127.0.0.1 -mask=255.255.255.255" > /etc/exports
# rcctl start portmap nfsd mountd

The order is really important. You can check that the folder is available through NFS with the following command:

$ showmount -e
Exports list on localhost:
/home/my_data               127.0.0.1

If you don’t have any line after “Exports list on localhost:”, you should kill mountd with pkill -9 mountd and start mountd again. I experienced it twice when starting all the daemons from the same commands but I’m not able to reproduce it. By the way, mountd only supports reload.

If you modify /etc/exports, you only need to reload mountd using rcctl reload mountd.

Once you have check that everything was alright, you can mount the exported folder on another folder with the command:

# mount localhost:/home/my_data /var/www/htdocs/my_data

You can add -ro parameter in the /etc/exports file on the export line if you want it to be read-only where you mount it.

Note: On FreeBSD/DragonflyBSD, you can use mount_nullfs /from /to, there is no need to setup a local NFS server. And on Linux you can use mount --bind /from /to and some others ways that I won’t cover here.

Use ramdisk on /tmp on OpenBSD

Written by Solène, on 08 May 2018.
Tags: #openbsd66 #openbsd

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If you have enough memory on your system and that you can afford to use a few hundred megabytes to store temporary files, you may want to mount a mfs filesystem on /tmp. That will help saving your SSD drive, and if you use an old hard drive or a memory stick, that will reduce your disk load and improve performances. You may also want to mount a ramdisk on others mount points like ~/.cache/ or a database for some reason, but I will just explain how to achieve this for /tmp with is a very common use case.

First, you may have heard about tmpfs, but it has been disabled in OpenBSD years ago because it wasn’t stable enough and nobody fixed it. So, OpenBSD has a special filesystem named mfs, which is a FFS filesystem on a reserved memory space. When you mount a mfs filesystem, the size of the partition is reserved and can’t be used for anything else (tmpfs, as the same on Linux, doesn’t reserve the memory).

Add the following line in /etc/fstab (following fstab(5)):

swap /tmp mfs rw,nodev,nosuid,-s=300m 0 0

The permissions of the mountpoint /tmp should be fixed before mounting it, meaning that the /tmp folder on / partition should be changed to 1777:

# umount /tmp
# chmod 1777 /tmp
# mount /tmp

This is required because mount_mfs inherits permissions from the mountpoint.

Unofficial OpenBSD FAQ

Written by Solène, on 16 March 2018.
Tags: #openbsd66 #openbsd

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Frequently asked questions (with answers) on #openbsd IRC channel

Please read the official OpenBSD FAQ

I am writing this to answer questions asked too many times. If some answers get good enough, maybe we could try to merge it in the OpenBSD FAQ if the topic isn’t covered. If the topic is covered, then a link to the official FAQ should be used.

If you want to participate, you can fetch the page using gopher protocol and send me a diff:

$ printf '/~solene/article-openbsd-faq.txt\r\n' | nc dataswamp.org 70 > faq.md

OpenBSD features / not features

Here is a list for newcomers to tell what is and what is not OpenBSD

See OpenBSD Innovations

  • Packet Filter : super awesome firewall

  • Sane defaults : you install, it works, no tweak

  • Stability : upgrades go smooth and are easy

  • pledge and unveil : security features to reduce privileges of software, lots of ports are patched

  • W^X security

  • Microphone muted by default, unlockable by root only

  • Video devices owned by root by default, not usable by users until permission change

  • Has only FFS file system which is slow and has no “feature”

  • No wine for windows compatibility

  • No linux compatibility

  • No bluetooth support

  • No usb3 full speed performance

  • No VM guest additions

  • Only in-house VMM for being a VM host, only supports OpenBSD and some Linux

  • Poor fuse support (it crashes quite often)

  • No nvidia support (nvidia’s fault)

  • No container / docker / jails

Does OpenBSD has a Code Of Conduct?

No and there is no known plan of having one.

This is a topic upsetting OpenBSD people, just don’t ask about it and send patches.

What is the OpenBSD release process?

OpenBSD FAQ official information

The last two releases are called “-release” and are officially supported (patches for security issues are provided).

-stable version is the latest release with the base system patches applied, the -stable ports tree has some patches backported from -current, mainly to fix security issues. Official packages for -stable are built and are picked up automatically by pkg_add(1).

What is -current?

It’s the development version with latest packages and latest code. You shouldn’t use it only to get latest package versions.

How do I install -current ?

OpenBSD FAQ about current

  • download the latest snapshot install .iso or .fs file from your favorite mirror under /snapshots/ directory
  • boot from it

How do I upgrade to -current

OpenBSD FAQ about current

You can use the script sysupgrade -s, note that the flag is only useful if you are not running -current right now but harmless otherwise.

Low bandwidth: Fetch OpenBSD sources

Written by Solène, on 09 November 2017.
Tags: #openbsd66 #openbsd

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When you fetch OpenBSD src or ports from CVS and that you want to save bandwidth during the process there is a little trick that change everything: compression

Just add -z9 to the parameter of your cvs command line and the remote server will send you compressed files, saving 10 times the bandwidth, or speeding up 10 times the transfer, or both (I’m in the case where I have differents users on my network and I’m limiting my incoming bandwidth so other people can have bandwidth too so it is important to reduce the packets transffered if possible).

The command line should looks like:

$ cvs -z9 -qd anoncvs@anoncvs.fr.openbsd.org:/cvs checkout -P src

Don’t abuse this, this consumes CPU on the mirror.

Bandwidth limit / queue on OpenBSD 6.6

Written by Solène, on 25 April 2017.
Tags: #openbsd66 #openbsd #unix #network

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Today I will explain how to do traffic limit with OpenBSD and PF. This is not hard at all if you want something easy, the man page pf.conf(5) in QUEUEING section is pretty good but it may disturbing when you don’t understand how it works. This is not something I master, I’m not sure of the behaviour in some cases but the following example works as I tested it ! :)

Use case

Internet is down at home, I want to use my phone as 4G router trough my OpenBSD laptop which will act as router. I don’t want the quota (some Gb) to be eaten in a few seconds, this connection allow to download up to 10 Mb/s so it can go quickly !

We will limit the total bandwidth to 1M (~ 110 kb/s) for people behind the NAT. It will be slow, but we will be sure that nothing behind the NAT like a program updating, cloud stuff synchronizing or videos in auto play won’t consume our quota.

Edit /etc/pf.conf accordigly to your network

internet="urndis0"
lan="em0"

# we define our available bandwidth
queue main on $lan bandwidth 100M

# we will let 1M but we will allow
# 3M during 200 ms when initiating connection to keep the web a bit interactive
queue limited parent main bandwidth 1M min 0K max 1M burst 3M for 200ms default

set skip on lo

# we do NAT here
match out on egress inet from !(egress:network) to any nat-to (egress:0)

block all
pass out quick inet

# we apply the queue here on EVERYTHING coming from the internet
pass in on $lan set queue limited

This ONLY defines queue for DOWNLOADING, you can only set the queue on the lan interface, this won’t work on egress (network interface having internet) because you can’t limit what go in your interface, it’s already there when you want to limit.

Per protocol ?

You can define queues per remote port by creating new queues and doing something like this:

pass in on $lan proto tcp port ssh set queue ssh
pass in on $lan proto tcp port www set queue web

Per host ?

As before, you can apply queues on IP host/range rather than protocols, or you can even mix both if you want.

Warning

The limit function changed in OpenBSD 5.5, everything you can read on the internet about ALTQ isn’t working anymore.

Connect to pfsense box console by usb

Written by Solène, on 10 April 2017.
Tags: #unix #network #openbsd66 #openbsd

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Hello,

I have a pfsense appliance (Netgate 2440) with a usb console port, while it used to be a serial port, now devices seems to have a usb one. If you plug an usb wire from an openbsd box to it, you woull see this in your dmesg

uslcom0 at uhub0 port 5 configuration 1 interface 0 "Silicon Labs CP2104 USB to UART Bridge Controller" rev 2.00/1.00 addr 7
ucom0 at uslcom0 portno 0

To connect to it from OpenBSD, use the following command:

# cu -l /dev/cuaU0 -s 115200

And you’re done

Let's encrypt on OpenBSD in 5 minutes

Written by Solène, on 20 January 2017.
Tags: #security #openbsd66 #openbsd

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Let’s encrypt is a free service which provides free SSL certificates. It is fully automated and there are a few tools to generate your certificates with it. In the following lines, I will just explain how to get a certificate in a few minutes. You can find more informations on Let’s Encrypt website.

To make it simple, the tool we will use will generate some keys on the computer, send a request to Let’s Encrypt service which will use http challenging (there are also dns and another one kind of challenging) to see if you really own the domain for which you want the certificate. If the challenge process is ok, you have the certificate.

Please, if you don’t understand the following commands, don’t type it.

While the following is right for OpenBSD, it may change slightly for others systems. Acme-client is part of the base system, you can read the man page acme-client(1).

Prepare your http server

For each certificate you will ask a certificate, you will be challenged for each domain on the port 80. A file must be available in a path under “/.well-known/acme-challenge/”.

You must have this in your httpd config file. If you use another web server, you need to adapt.

server "mydomain.com" {
    root "/empty"
    listen on * port 80
    location "/.well-known/acme-challenge/*" {
        root { "/acme/" , request strip 2 }
    }
}

The request strip 2 part is IMPORTANT. (I’ve lost 45 minutes figuring out why root “/acme/” wasn’t working.)

Prepare the folders

As stated in acme-client man page and if you don’t need to change the path. You can do the following commands with root privileges :

# mkdir /var/www/acme
# mkdir -p /etc/ssl/acme/private /etc/acme
# chmod 0700 /etc/ssl/acme/private /etc/acme

Request the certificates

As root, in the acme-client sources folder, type the following the generate the certificates. The verbose flag is interesting and you will see if the challenging step work. If it doesn’t work, you should try manually to get a file like with the same path tried from Let’s encrypt, and try again the command when you succeed.

$ acme-client -vNn mydomain.com www.mydomain.com mail.mydomain.com

Use the certificates

Now, you can use your SSL certificates for your mail server, imap server, ftp server, http server…. There is a little drawback, if you generate certificates for a lot of domains, they are all written in the certificate. This implies that if someone visit one page, look at the certificate, this person will know every domain you have under SSL. I think that it’s possible to ask every certificate independently but you will have to play with acme-client flags and make some kind of scripts to automatize this.

Certificate file is located at /etc/ssl/acme/fullchain.pem and contains the full certification chain (as its name is explicit). And the private key is located at /etc/ssl/acme/private/privkey.pem.

Restart the service with the certificate.

Renew certificates

Certificates are valid for 3 months. Just type

./acme-client mydomain.com www.mydomain.com mail.mydomain.com

Restart your ssl services

EASY !