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--- openbsd [2023/06/23 10:58] – [Services] maja
+++ openbsd [2023/06/23 11:41] (current) – reorder maja
@@ Line 65: / Line 65: @@
 </code>
 eg; to stop the web-server's httpd daemon ''rcctl stop httpd''
-==== Firewall PF ====
-pf.conf and pf.os \\
-pfctl \\
-pftop \\
 ==== 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 ====