Differences

This shows you the differences between two versions of the page.

--- openbsd [2023/06/23 09:00] – about and better context and spelling maja
+++ openbsd [2023/06/23 11:41] (current) – reorder maja
@@ Line 23: / Line 23: @@
 \\
 ===== Installation =====
-Text based install only
+OpenBSD installer is a text_only affair. (like many other BSD's or Linux server distros)\\
+Although initially jarring compared to modern GUI installers, the OpenBSD installer is light, fast, and easy to follow along.\\
+\\
+Choosing the disk-sets can be tricky from a USB booted image, as seems you have to re-mount it, and advanced disk partitioning can be daunting initially.\\
+\\
+The [[https://www.openbsd.org/faq/index.html|FAQ]] has all the info you need, including steps for disk encryption and raid configs.
 ===== Setup =====
-post install:
+my normal post install adjustments include:\\
-create user, add to wheel, operator, staff with #usermod -G wheel operator staff my-user-name \\
-add to staff login group with #usermod -L staff my-user-name \\
-config ''/etc/doas.conf'' with "permit persist keepenv :wheel" \\
-secure ssh server ''/etc/ssh/sshd_config'' by forcing ed22159 host keys, key-auth and disable root-password \\
-patch os #syspatch, and packages #pkg_add -u \\
-firewall config appropriate for host in ''/etc/pf.conf'' normally blocking all , allowing sshd and web with connection thresholds and overflows \\
-if web server, config httpd, acme-client, and php \\
 \\
+add my user to the operator and staff user groups with ''usermod -G wheel operator staff my-user-name'' \\
+add my user to the staff login profile with ''usermod -L staff my-user-name'' \\
+\\
+sudo has been replaced with ''doas''\\
+as root create/config file ''/etc/doas.conf'' with ''"permit persist keepenv :wheel"'' \\
+\\
+i only use strong modern ssh keys, so i like to further secure the ssh-server\\
+edit the ''/etc/ssh/sshd_config'' file and force ed22159 host keys, key-auth and disable root-password \\
+\\
+keeping the OS and Apps upto date with binary patches\\
+os ''syspatch'', and packages ''pkg_add -u'' \\
+\\
+For Servers adjust the firewall to allow access to services\\
+using ''PF'' firewall config appropriate for host in ''/etc/pf.conf''\\
+normally blocking all , allowing sshd and web with connection thresholds and overflows \\
+i might also install ''pftop'' ''curl'' and ''wget''
+\\
+and if your setting up a web server, config ''httpd'', ''acme-client'', ''php'' and ''dokuwiki'' \\
+\\
+For Desktops allow xenodm and setup your favorite DM/DE. FVWM and CWM are there in base, but XFCE and Gnome are in packages, as is Firefox and Chromium.
 ===== Services =====
-check in rc.conf and /etc/examples for guidance and ideas \\
+init based service control system, check in ''/etc/rc.conf'' , ''/etc/rc.local'' and ''/etc/examples'' for guidance and ideas \\
-rcctl enable|disable|start|stop|reload \\\
+services are easily controlled, with ''rcctl''\\
-==== Firewall PF ====
+<code>
-pf.conf and pf.os \\
+usage:	rcctl get|getdef|set service | daemon [variable [arguments]]
-pfctl \\
+	rcctl [-df] configtest|check|reload|restart|stop|start daemon ...
-pftop \\
+	rcctl disable|enable|order [daemon ...]
+	rcctl ls all|failed|off|on|rogue|started|stopped
+</code>
+eg; to stop the web-server's httpd daemon ''rcctl stop httpd''
 ==== SSHD ====
+OpenBSD team long ago forked SSH and created their own version, and probably their best known project. it's so good its now the de-facto variant installed on most other OS's.\\
+\\
+As a client i rarely modify the local file. if the host is a workstation/laptop i create a new ed25519 private key. ''ssh-keygen -t ed25519''\\
+\\
+although defaults are always sane, for servers  i modify the ''/etc/ssh/sshd_config'' file and allow only ed25519 host keys from being presented, this gets rid of of a lot of probing attempts, as well as adjusting root login conditions\\
+<file - sshd_config>
+#HostKey /etc/ssh/ssh_host_rsa_key
+#HostKey /etc/ssh/ssh_host_ecdsa_key
+HostKey /etc/ssh/ssh_host_ed25519_key
+#PermitRootLogin yes
+PermitRootLogin prohibit-password
+</file>
+\\
+which ends up with entertaining log files like ''/etc/var/authlog''\\
+<code>
+Jun 23 09:44:58 freyja sshd[95566]: Unable to negotiate with 35.167.89.48 port 44522: no matching host key type found. Their offer: ssh-rsa [preauth]
+Jun 23 09:44:59 freyja sshd[72370]: Unable to negotiate with 35.167.89.48 port 45206: no matching host key type found. Their offer: ssh-dss [preauth]
+Jun 23 10:11:40 freyja sshd[39801]: Unable to negotiate with 218.92.0.112 port 29204: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:12:17 freyja sshd[52019]: Unable to negotiate with 61.177.172.185 port 51943: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:13:23 freyja sshd[12803]: Unable to negotiate with 218.92.0.31 port 11816: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:16:04 freyja sshd[56545]: Unable to negotiate with 220.135.177.191 port 46403: no matching host key type found. Their offer: ssh-rsa,ssh-dss [preauth]
+Jun 23 10:18:30 freyja sshd[23558]: Unable to negotiate with 218.92.0.35 port 43999: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:41:08 freyja sshd[82987]: Unable to negotiate with 218.92.0.17 port 38235: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:43:22 freyja sshd[50498]: Unable to negotiate with 218.92.0.113 port 55744: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:53:12 freyja sshd[8374]: Unable to negotiate with 218.92.0.31 port 17833: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:55:36 freyja sshd[93234]: Unable to negotiate with 218.92.0.17 port 25671: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 10:57:45 freyja sshd[16168]: Unable to negotiate with 218.92.0.35 port 42553: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 11:02:15 freyja sshd[48351]: Unable to negotiate with 218.92.0.24 port 61448: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 11:12:35 freyja sshd[75959]: Unable to negotiate with 218.92.0.31 port 41679: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 11:25:11 freyja sshd[38673]: Unable to negotiate with 218.92.0.98 port 18570: no matching host key type found. Their offer: ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa,ssh-dss [preauth]
+Jun 23 11:26:01 freyja sshd[53372]: Unable to negotiate with 220.80.14.246 port 63144: no matching host key type found. Their offer: ssh-rsa,ssh-dss [preauth]
+$ grep negotiate /var/log/authlog | wc -l
+</code>
+==== Firewall PF ====
+PF is a super firewall, there is a good doco available in the [[https://www.openbsd.org/faq/pf/index.html|FAQ]] section\\
+main file is the ''/etc/pf.conf'' and by default everything in is blocked and everything out allowed.\\
+''pfctl'' is the main command to interact with pf. including viewing and modifying config on the fly.\\
+''pftop'' is a additional package, and is a top-like cli tool to monitor pf live\\
+\\
+Combine SSH and PF and you'll passively discard a lot
+<file text pf.conf>
+# Allow SSH, trap and block offenders into 'ssh-abuse' table
+pass inet proto tcp from any to $ext_if port ssh \
+        flags S/SA keep state \
+        (max-src-conn 20, max-src-conn-rate 5/3, \
+         overload <ssh-abuse> flush global)
+</file>
+<code>
+$ doas pfctl -t ssh-abuse -Ts | wc -l
+</code>
 ==== Spamd ====