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Some more editing to make this read better.

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Florian Obser 2023-01-15 08:47:01 +01:00
parent c41a8a11a2
commit 9e53448453
1 changed files with 18 additions and 14 deletions
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32
VerifyHostKeyDNS.org
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@ -30,7 +30,7 @@ host-keys of new hosts and new hosts needing to verify host-keys of
existing infrastructure. One way to deal with this is to run a [[https://www.lorier.net/docs/ssh-ca.html][CA, existing infrastructure. One way to deal with this is to run a [[https://www.lorier.net/docs/ssh-ca.html][CA,
sign host-keys with it and roll certificates out]]. sign host-keys with it and roll certificates out]].
I on the other hand prefer to use DNS[fn:: I have a laptop sticker and I on the other hand, prefer to use DNS[fn:: I have a laptop sticker and
travel mug with "We reject kings, presidents and voting. We believe in travel mug with "We reject kings, presidents and voting. We believe in
rough consensus and running code." crossed out with "Fuck that! Just rough consensus and running code." crossed out with "Fuck that! Just
put it in DNS." I also have a RUN DNS sticker. I am biased]. [[https://www.rfc-editor.org/rfc/rfc4255][RFC4255]] provides put it in DNS." I also have a RUN DNS sticker. I am biased]. [[https://www.rfc-editor.org/rfc/rfc4255][RFC4255]] provides
@ -56,10 +56,9 @@ Host *
VerifyHostKeyDNS yes VerifyHostKeyDNS yes
#+end_example #+end_example
into your =.ssh/config= it will not work. The magic is /secure into your =.ssh/config= it will not work. The magic is /secure
fingerprint/. What the man page means is that a DNS answer for SSHFP fingerprint/. What the documentation means is that a DNS answer for
needs to have the /Authentic Data (AD)/ flag set. The flag gets set SSHFP needs to have the /Authentic Data (AD)/ flag set. The flag gets
when a validating name-server is asked for the SSHFP record, it finds set by a validating name-server if it can DNSSEC validate the SSHFP.
it and it can validate the answer using DNSSEC.
But then the libc stub resolver[fn:: The thingy[fn:: Thingy is a But then the libc stub resolver[fn:: The thingy[fn:: Thingy is a
technical term, don't worry about it.] that ssh uses to talk technical term, don't worry about it.] that ssh uses to talk
@ -79,15 +78,20 @@ have a trustworthy validating name-server is to run one on localhost.
trusted. This option is automatically enabled if resolv.conf only trusted. This option is automatically enabled if resolv.conf only
lists name servers on localhost. lists name servers on localhost.
The easiest way is to run [[https://man.openbsd.org/unwind.8][unwind(8)]]. [[https://man.openbsd.org/resolvd.8][resolvd(8)]] will then add The easiest way is to run [[https://man.openbsd.org/unwind.8][unwind(8)]]:
=nameserver 127.0.0.1= into =/etc/resolv.conf= and comment out all #+begin_src shell
other dynamically learned name servers. Just make sure that you are doas rcctl enable unwind
not using any static configured name servers[fn:: I use ~! route doas rcctl start unwind
nameserver $if 149.112.112.9 2620:fe::9 9.9.9.9 2620:fe::fe:9~ in my #+end_src
main [[http://man.openbsd.org/hostname.if.5][hostname.if(5)]] to add some static name servers in case unwind(8)
crashes[fn:: Not sure why it would do that though. Sounds [[https://man.openbsd.org/resolvd.8][resolvd(8)]] will then add =nameserver 127.0.0.1= to
unpleasant.].] because you really want to have only =nameserver =/etc/resolv.conf= and comment out all other dynamically learned name
127.0.0.1= in there. servers. Just make sure that you are not using any static configured
name servers[fn:: I use ~! route nameserver $if 149.112.112.9
2620:fe::9 9.9.9.9 2620:fe::fe:9~ in my main [[http://man.openbsd.org/hostname.if.5][hostname.if(5)]] to add
some static name servers in case unwind(8) crashes[fn:: Not sure why
it would do that though. Sounds unpleasant.].] because you really want
to have only =nameserver 127.0.0.1= in there.
* Putting it all together * Putting it all together
When I install a new host I have out of band access in one way or When I install a new host I have out of band access in one way or
another. It might be a serial console, a fake html5 console or some another. It might be a serial console, a fake html5 console or some