User:Paul/sandbox/OpenBSD Basic Server
OpenBSD has earned its reputation as a BSD descendant focused on security. With the increased development of OpenBSD's httpd and OpenSMTPD, plus most of the components commonly used in a basic web server, OpenBSD provides a highly secure and efficient choice for building servers.
Finding online support for OpenBSD can be much more difficult when compared to Linux. While the OpenBSD project requires its man pages to be very complete, support beyond man pages such as tutorials or sample configurations can be much harder to find. This has largely been due to the project being targeted at use primarily by professional systems administrators.
This tutorial will establish a basic web server that includes a functioning mail server with local maildir accessed through mutt.
Initial configuration
The default configuration for OpenBSD is generally acceptable for the majority of users. However, some small changes are necessary to some configurations.
Run updates
On initial login, update OpenBSD and installed packages, then reboot:
servername# syspatch Get/Verify syspatch66-020_vmm_pvc... 100% |*************| 178 KB 00:00 Installing patch 020_vmm_pvclock Get/Verify syspatch66-021_smtpd_e... 100% |*************| 317 KB 00:01 Installing patch 021_smtpd_envelope Relinking to create unique kernel... done; reboot to load the new kernel Errata can be reviewed under /var/syspatch servername# pkg_add -u quirks-3.183 signed on 2020-03-08T21:21:46Z pcre2-10.33->10.34: ok Read shared items: ok servername# reboot
Install nano
Log back into the server using the root
account.
For users not familiar with vi
or mg
, it may be preferable to install a simple text editor, such as nano
servername# pkg_add nano quirks-3.183 signed on 2020-03-08T21:21:46Z nano-4.4: ok
Set up user account
servername# adduser
This will generate adduser.conf
for default new user configuration by asking several questions, followed the option to set up a new user. Default options are presented within brackets []
(e.g, [default]
). Pressing Enter
without typing anything will select the default option.
Couldn't find /etc/adduser.conf: creating a new adduser configuration file Reading /etc/shells Enter your default shell: csh ksh nologin sh [ksh]: Your default shell is: ksh -> /bin/ksh Default login class: authpf bgpd daemon default pbuild staff unbound [default]: Enter your default HOME partition: [/home]: Copy dotfiles from: /etc/skel no [/etc/skel]: Send welcome message?: /path/file default no [no]: yes Really? Type the filepath, 'default' or 'no' [no]: default Message file ``/etc/adduser.message'' created Prompt for passwords by default (y/n) [y]: Default encryption method for passwords: auto blowfish [auto]: Use option ``-silent'' if you don't want to see all warnings and questions. Reading /etc/shells Check /etc/master.passwd Check /etc/group Ok, let's go. Don't worry about mistakes. There will be a chance later to correct any input. Enter username []: username Enter full name []: Full Username Enter shell csh ksh nologin sh [ksh]: Uid [1000]: Login group username [username]: Login group is ``username''. Invite username into other groups: guest no [no]: wheel Login class authpf bgpd daemon default pbuild staff unbound [default]: staff Enter password []: Enter password again []: Name: username Password: **** Fullname: Full Username Uid: 1000 Gid: 1000 (username) Groups: username wheel Login Class: staff HOME: /home/username Shell: /bin/ksh OK? (y/n) [y]: Added user ``username'' Copy files from /etc/skel to /home/username Send welcome message to ``username'' (y/n) [y]: Full Username, your account ``username'' was created. Have fun! See also chpass(1), finger(1), passwd(1) Add anything to the message (y/n) [n]: Copy message to another user?: no root second_mail_address [no]: Mail sent! Add another user? (y/n) [y]: n Goodbye!
The above configured username account is intended to be an administrator account for the server. Adding the wheel
group applies several administrator level privilege configurations, as well as editing or reading privileges of otherwise protected system files and directories. Configuration as staff
grants the account greater resource availability within OpenBSD.
Configure and enable doas
The OpenBSD sudo
command is doas
, but is not configured by default.
There are many example configuration files located in /etc/examples/
:
servername# ls /etc/examples/ acme-client.conf ifstated.conf ospfd.conf ripd.conf bgpd.conf iked.conf pf.conf sasyncd.conf chio.conf inetd.conf printcap sensorsd.conf dhclient.conf ipsec.conf rad.conf snmpd.conf dhcpd.conf ldapd.conf radiusd.conf sysctl.conf doas.conf ldpd.conf rbootd.conf unwind.conf dvmrpd.conf man.conf rc.local vm.conf eigrpd.conf mixerctl.conf rc.securelevel wsconsctl.conf exports mrouted.conf rc.shutdown ypldap.conf hostapd.conf ntpd.conf relayd.conf httpd.conf ospf6d.conf remote
Copy the example doas.conf
file into /etc/
servername# cp /etc/examples/doas.conf /etc/
Edit the configuration file:
servername# nano /etc/doas.conf
Change:
permit persist keepenv :wheel
By adding the configuration to /etc/
, doas
can now be invoked. The configuration file permits members of wheel
to use doas
and permitting persist
means that each time doas
is successfully invoked, a password will not be required when invoked again within five minutes.
Configure sshd
Permitting log in through ssh with the root
account or using passwords to log in are considered bad practice. The sshd
configuration is managed through the sshd_config
configuration file:
servername# nano /etc/ssh/sshd_config
Edit the following keyword line configurations to match the following:
#PermitRootLogin yes
PubkeyAuthentication yes
PasswordAuthentication no
Restart sshd
:
servername# rcctl restart sshd sshd(ok) sshd(ok)
Most security experts are recommending moving away from RSA keys. As configured, OpenBSD will work with RSA and ed25519 keys. In OpenSSH installations in most Linux distributions, both will be installed by default and ed25519 public keys are in the /home/username/.ssh/id_ed25519.pub
file.
Add a public key to the configured user account authorized_keys
file:
servername# nano /home/username/.ssh/authorized_keys
Notable differences from Ubuntu Linux
Shell
Ubuntu default shell uses Bash (BASH) while OpenBSD uses KornShell (ksh).
ll
(ls -alF
)
Ubuntu has a convenient command, ll
, for viewing directory contents that is a shortcut for ls -alF
.
To add ll
to the OpenBSD command line:
$ nano .profile
Add the following line:
alias ll="ls -alF"
Default editor
The default text editor in OpenBSD is vi
. To change to a different default text editor:
$ nano .profile
Add the following line:
export EDITOR=/usr/local/bin/nano
Do the same for root
:
$ doas nano /root/.kshrc
Add the following line:
export EDITOR=/usr/local/bin/nano
Note that this does not change the default editor for doas
, such as when calling the crontab
command.
Web server
Most of the instructions in this article require root
:
$ doas su
OpenBSD comes with httpd
, the project's own web server, installed by default though disabled. The httpd
configuration is managed in its configuration file, /etc/httpd.conf
, which has to be created:
# nano /etc/httpd.conf
Add to the file:
# Main Configuration server "example.com" { listen on * port 80 root "/htdocs/example.com" location "/.well-known/acme-challenge/*" { root "/acme" request strip 2 } location * { block return 302 "https://$HTTP_HOST$REQUEST_URI" } }
Test the configuration:
# httpd -n configuration OK
Start httpd
.
# rcctl -f start httpd httpd(ok)
Add a Let's Encrypt certificate to the server:
# cp /etc/examples/acme-client.conf /etc/acme-client.conf # nano /etc/acme-client.conf
Change example.com
to the desired domain and remove, change, or add subdomains to the alternative
line.
# acme-client -v example.com
After successful registration, create a cron job:
# crontab -e
Add:
0 * * * * sleep $((RANDOM \% 2048)) && \ acme-client example.com && rcctl reload httpd
Now add the SSL/TLS and redirect options httpd.conf
# nano /etc/httpd.conf
Add:
# This is a redirect to the Main Configuration server "www.example.com" { listen on * port 80 listen on * tls port 443 tls { certificate "/etc/ssl/example.com.fullchain.pem" key "/etc/ssl/private/example.com.key" } block return 301 "http://example.com$REQUEST_URI" } server "example.com" { listen on * tls port 443 root "/htdocs/example.com" tls { certificate "/etc/ssl/example.com.fullchain.pem" key "/etc/ssl/private/example.com.key" } location "/.well-known/acme-challenge/*" { root "/acme" request strip 2 } }
Test and restart httpd
# httpd -n Configuration OK # rcctl reload httpd httpd(ok)
OpenBSD in its default configuration comes with opensmtpd
in a very secure configuration that supports outgoing mail. This is primarily useful for transactional email, most especially administrative messages.
Administrative message recipients can be configured in the aliases
file and are default configured to be sent to the local root
user local mailbox. To configure additional recipients:
# nano /etc/mail/aliases
Change and add:
# Basic system aliases -- these MUST be present MAILER-DAEMON: postmaster postmaster: root root: username@example.com,anotherusername@example.net
Update the configuration:
# newaliases
Mail server configuration
Create DKIM key and directory:
# mkdir /etc/mail/dkim # openssl genrsa -out /etc/mail/dkim/example.com.key 1024 # chmod 640 /etc/mail/dkim/example.com.key # openssl rsa -in /etc/mail/dkim/example.com.key -pubout -out /etc/mail/dkim/example.com.pub # cat /etc/mail/dkim/example.com.pub
Install and configure antispam packages
# pkg_add redis rspamd opensmtpd-filter-rspamd opensmtpd-filter-senderscore
Configure DKIM signing:
# chown root:_rspamd /etc/mail/dkim/example.com.key # mkdir /etc/rspamd/local.d # nano /etc/rspamd/local.d/dkim_signing.conf allow_username_mismatch = true; domain { example.com { path = "/etc/mail/dkim/example.com.key"; selector = "20200221"; } }
Enable and start redis
and rspamd
:
# rcctl enable redis # rcctl enable rspamd # rcctl start redis redis(ok) # rcctl start rspamd rspamd(ok)
Update the OpenSMTPD configuration:
# mv /etc/mail/smtpd.conf /etc/mail/smtpd.conf.original # nano /etc/mail/smtpd.conf
pki mail.hypno.cat cert "/etc/ssl/mail.hypno.cat.fullchain.pem" pki mail.hypno.cat key "/etc/ssl/private/mail.hypno.cat.key" filter check_dyndns phase connect match rdns regex { '.*\.dyn\..*', '.*\.dsl\..*' } \ disconnect "550 no residential connections" filter check_rdns phase connect match !rdns \ disconnect "550 no rDNS is so 80s" filter check_fcrdns phase connect match !fcrdns \ disconnect "550 no FCrDNS is so 80s" filter senderscore \ proc-exec "filter-senderscore -blockBelow 10 -junkBelow 70 -slowFactor 5000" filter rspamd proc-exec "filter-rspamd" table aliases file:/etc/mail/aliases listen on all tls pki example.com \ filter { check_dyndns, check_rdns, check_fcrdns, senderscore, rspamd } listen on all port submission tls-require pki example.com auth filter rspamd action "local_mail" maildir junk alias <aliases> action "outbound" relay helo example.com match from any for domain "example.com" action "local_mail" match for local action "local_mail" match from any auth for any action "outbound" match for any action "outbound"
Reinstallation on Vultr
To run OpenBSD as configured by the OpenBSD project, it is currently necessary to create a Vultr instance running OpenBSD, then reinstall OpenBSD using the terminal in the Vultr dashboard.
From the Vultr dashboard, open the OpenBSD instance and click the terminal icon at the top of the page. Note that when using the terminal interface, it will not be possible to use a mouse, access the local clipboard, or otherwise interact with the interface other than through the keyboard.
Log in using root
with the password from the Vultr dashboard.
vultr# reboot
After the system boots there will be a boot prompt. Simply enter rc.d
and press enter.
boot> rc.d
Most of the install questions can be answered using the default, which is shown in brackets.
Create the root
user using the password provided for the instance by Vultr.
The non-default selections will be entering the domain of the hostname (example.com) plus the following:
Do you expect to run the X Window System? [yes] no
There is a warning about not allowing root
to ssh log in using password. This is will be configured later in the setup process.
Allow root ssh login? (yes, no, prohibit-password) [no] yes
Location of sets? (cd0 disk http nfs or 'done') [cd0] http
For selecting the download location, enter ?
then note a desired download location and enter the number:
HTTP Server? (hostname, list#, 'done' or '?') ? ... HTTP Server? (hostname, list#, 'done' or '?') 47