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Re: DNSSEC working but SSHFP reported as insecure




On Dec 3, 2022, at 9:22 AM, Andre Rodier <andre@rodier.me> wrote:

ssh -o VerifyHostKeyDNS=yes main.homebox.world

Yes, this is the default option in my ssh/config file.

I tried on the command line as well, but same result:

It could be that your default DNS resolver is not validating.  ssh simply looks at the result of the DNSSEC validation provided by your default resolver [1], so if it's not validating then you will never get "secure".  In the example in your original post, you queried 1.1.1.1, which is a validating resolver.  But your default resolver might yield different results.  To test, do the following:

$ dig +dnssec main.homebox.world sshfp

And look for the presence of the "ad" (authenticated data) flag in the response.

Casey

[1] https://github.com/openssh/openssh-portable/blob/master/dns.c#L230

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