I am intensely using the SSH Public Key Fingerprint (SSHFP, RFC 4255) in all of my environments. Since my zones are secured via DNSSEC I got rid of any “authenticity of host ‘xyz’ can’t be established” problems. As long as I am using my central jump host with OpenSSH and the “VerifyHostKeyDNS yes” option I can securely login into any of my servers without any warnings. Great!
However, I encountered a couple of daily problems when using SSHFP. One of them was the question whether SSHFP works behind CNAMEs, that is, when connecting to an alias. Short answer: yes. Some more details here:
Continue reading SSHFP behind CNAME →
I am testing a lot with my own DNS servers as well as with third-party DNS implementations such as DNS proxies on firewalls, DNSSEC validation on resolvers, etc. While there are a number of free DNS online tools around the Internet I was lacking some DNS test names with certain properties or resource records. Hence I configured a couple of them on my own authoritative DNS servers and its zone
For example, we encountered a bug on the Palo Alto DNS proxy that has not stored the TTL value correctly – hence some test names with different TTL values. Or we had some problems when a single DNS name has more than 15 IPv4/IPv6 addresses – hence some test names with lots of addresses. And many more: Continue reading DNS Test Names & Resource Records →