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.
OpenBSD providers pre-compiled binary packages available by using the pkg_add. The pkg_info command can be used to provide information on a package. To search packages, navigate to the page for the installed version:
https://cdn.openbsd.org/pub/OpenBSD/6.8/packages/amd64/
For other versions of OpenBSD, navigate to the version's packages from https://cdn.openbsd.org/pub/OpenBSD/.
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 login 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 no
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
Updates and upgrades
The OpenBSD Project makes system updates, package updates, and system version upgrades very easy, as they view it as an important part to security. After all, if an upgrade is difficult or laborious, how likely are admins to install them?
Package updates
Package updates are relatively easy to install:
servername /home/username $ doas pkg_add -u
System updates
Most versions of OpendBSD will have a dozen or so updates over the life of the version.
servername /home/username $ doas syspatch
Some updates require a reboot, so it is important to note the messages output during the update.
System upgrade
Prior to performing a system upgrade, it is important to make sure all package and OS updates have been installed as per the preceding steps.
servername /home/username $ doas sysupgrade
After the upgrade has completed and the server has rebooted, log in and perform the following:
servername /home/username $ doas pkg_add -Uu $ doas pkg_delete -a $ doas sysmerge
Adding the -U option when running package update will update the dependencies, which can otherwise be a problem after system upgrades.
Running pkg_delete -a will delete unused dependencies, which are often present after upgrades.
The sysmerge command is used to update configuration files after an upgrade.
Customizations
OpenBSD uses the KornShell (ksh) and a few changes can be made to create custom command line entries, some of which borrow from other projects, such defaults found in Unbuntu, which uses GNU Bash (BASH).
ll (ls -alhF)
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 -alhF"
The h option prints file sizes in human readable form (e.g., 1.2G).
Default editor
The default text editor in OpenBSD is vi. To change to a different default text editor, such as nano:
$ nano .profile
Add the following lines:
export EDITOR="$VISUAL" export VISUAL=/usr/local/bin/nano
Do the same for root:
$ doas nano /root/.profile
Add the following lines:
export EDITOR="$VISUAL" export VISUAL=/usr/local/bin/nano
Command prompt
The standard command prompt is somewhat intrusive when operating from nested and long directory names or using long commands while being sparse on information. A still easy to read but more informative prompt can be created with a small change to .profile:
$ nano .profile
Add the following:
PS1='servername $PWD\n$ '
At next login for the user, the command prompt should look like:
servername /home/username $
Web server
OpenBSD has two components for serving websites: relayd and httpd.
Web server with relayd and httpd
Using relayd provides greater flexibility while adding only a little extra work in the initial setup.
Web server with only httpd
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)
Enable DNS resolution and local time
If a package requires local time or DNS resolution, the following configuration will support this within the chroot:
# mkdir /var/www/etc
# cp /etc/{hosts,localtime,resolve.conf} /var/www/etc/
Install PHP
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
Transactional mail configuration
This configuration is for sending transactional mail and supporting DKIM for a single domain that can be used in DNS records for multiple domains.
$ doas pkg_add opensmtpd-filter-dkimsign
Note that the man page for dkimsign is located at man filter-dkimsign.
$ doas openssl genrsa -out /etc/mail/dkim/selector.key 1024 $ doas chmod 0640 /etc/mail/dkim/selector.key $ doas openssl rsa -in /etc/mail/dkim/selector.key -pubout -out /etc/mail/dkim/selector.pub $ doas chown -R _dkimsign:_dkimsign /etc/mail/dkim
The selector can be left as is in the sample text or changed to a different character string, such as a date, a domain, airspeed of an unladen swallow, etc.
$ doas nano /etc/mail/smtpd.conf
Change to:
# This is the smtpd server system-wide configuration file.
# See smtpd.conf(5) for more information.
table aliases file:/etc/mail/aliases
filter "dkimsign" proc-exec "filter-dkimsign \
-d example.com -s selector -t \
-k /etc/mail/dkim/selector.key" user _dkimsign group _dkimsign
listen on socket filter "dkimsign"
listen on lo0 filter "dkimsign"
action "local_mail" mbox alias <aliases>
action "outbound" relay
# Uncomment the following to accept external mail for domain "example.org"
#
# match from any for domain "example.org" action "local_mail"
match for local action "local_mail"
match for any action "outbound"
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, which makes use of multiple partitions, it is currently necessary to create a Vultr instance running OpenBSD, then reinstall OpenBSD using the console in the Vultr dashboard.
Open the console
From the Vultr dashboard, open the OpenBSD instance and click the console icon at the top of the page. Note that when using the console 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.
Load installer through bsd.rd
Log in using root with the password from the Vultr dashboard.
vultr# reboot
Note the above step may be performed through SSH, which may be easier to enter password and access the shell using the local clipboard.
After the system boots there will be a boot prompt:
boot> bsd.rd
Followed by a question:
Welcome to the OpenBSD/amd64 6.6 installation program (I)nstall, (U)pgrade, (A)utoinstall or (S)hell? I
Install OpenBSD with partitions
Most of the install questions can be answered using the default, which is shown in brackets.
Note the following non-default answers:
Create the root user using the password provided for the instance by Vultr, taking care to correctly enter ambiguous characters.
Enter the domain of the hostname (example.com).
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 reconfigured 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
Configure the partitions
The automatically generated partition table for a 25GB server instance will look something like below and should be edited:
# size offset fstype [fsize bsize cpg] a: 890.7M 64 4.2BSD 2048 16384 1 # / b: 1263.9M 1824160 swap c: 25600.0M 0 unused d: 1305.M 4412544 4.2BSD 2048 16384 1 # /tmp e: 2005.8M 7085376 4.2BSD 2048 16384 1 # /var f: 2240.7M 11193184 4.2BSD 2048 16384 1 # /usr g: 828.4M 15782080 4.2BSD 2048 16384 1 # /usr/X11R6 h: 3246.0M 17478656 4.2BSD 2048 16384 1 # /usr/local i: 1596.3M 24126560 4.2BSD 2048 16384 1 # /usr/src j: 5712.5M 27395712 4.2BSD 2048 16384 1 # /usr/obj k: 6506.4M 39095008 4.2BSD 2048 16384 1 # /home Use (A)uto layout, (E)dit auto layout, or create (C)ustom layout? [a] e
For available commands from the prompt, enter ? or see the disklable(8) man page
The /usr/src and /usr/obj partitions are used when updating or upgrading OpenBSD from source, but this is not planned for usage of this installation so will not be created.
If an error is made when making a change, u will undo the last change, and u a second time will restore the change, while U will undo all changes.
Delete and create partitions. To see the current partition table with changes, use p *.
sd0> z sd0*> a a offset: [64] size: [52420031] 1793024 FS type: [4.2BSD] mount point: [none] / sd0*> a b offset: [1793088] size [50627007] 3073771 FS type: [swap] sd0*> a d offset: [4866859] size: [47553236] 2663840 FS type: [4.2BSD] mount point: [none] /tmp sd0*> a e offset: [7530720] size: [44889375] 20491776 FS type: [4.2BSD] mount point: [/var] sd0*> a f offset: [28022496] size: [24397599] 6147520 FS type: [4.2BSD] mount point: [none] /usr sd0*> a g offset: [37858560] size: [14561535] 1991776 FS type: [4.2BSD] mount point: [none] /usr/X11R6 sd0*> a h offset: [39850336] size: [12569759] 3434400 FS type: [4.2BSD] mount point: [none] /usr/local sd0*> a k offset: [43284736] size: [9135359] FS type: [4.2BSD] mount point: [none] /home sd0*> p * OpenBSD area: 64-52410098; size: 25595.7; free: 0.0M # size offset fstype [fsize bsize cpg] a: 875.5M 64 4.2BSD 2048 16384 1 # / b: 1500.9M 1793088 swap c: 25600.0M 0 unused d: 1300.7M 4866880 4.2BSD 2048 16384 1 # /tmp e: 10005.8M 7530720 4.2BSD 2048 16384 1 # /var f: 4802.8M 28022496 4.2BSD 2048 16384 1 # /usr g: 972.5M 37858560 4.2BSD 2048 16384 1 # /usr/X11R6 h: 1677.0M 39850336 4.2BSD 2048 16384 1 # /usr/local k: 4460.6M 43284736 4.2BSD 2048 16384 1 # /home sd0*> w sd0> q
A sector is 512 bytes and the offset is the sector the partition begins at. If Vultr changes the number of sectors, simply determine the free sectors using the r command and modify the partitions, moving them in similar fashion to above steps (e.g., starting with partition k:).
While the above configuration should be acceptable for most small server needs, it does have some weaknesses. On a busier server, there should likely be separate partitions created for /var/log/, /var/db/, /var/www/, and /var/www/logs/. This is to prevent applications from filling the partition and crashing the server.
Now the partitions will be created and the installer will ask:
Let's install the sets! Location of sets? (cd0 disk http nfs or 'done') [http} HTTP proxy URL? (e.g. 'http://proxy:8080', or 'none') [note] HTTP Server? (hostname, list#, 'done' or '?') [mirrors.sonic.net] Server directory? [pub/OpenBSD/6.6/amd64]
For the software selection, leave all selected and at [done] press enter.
When given the option to reboot, press enter.
Install MariaDB
servername$ doas pkg_add -v mariadb-server