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[README.dns]
update
Resynced with OpenBSD too: DNSFP support is now always compiled in
so the configure support (and documentation thereof) can go away.
48 lines
1.6 KiB
Plaintext
48 lines
1.6 KiB
Plaintext
How to verify host keys using OpenSSH and DNS
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---------------------------------------------
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OpenSSH contains support for verifying host keys using DNS as described in
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draft-ietf-secsh-dns-05.txt. The document contains very brief instructions
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on how to use this feature. Configuring DNS is out of the scope of this
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document.
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(1) Server: Generate and publish the DNS RR
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To create a DNS resource record (RR) containing a fingerprint of the
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public host key, use the following command:
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ssh-keygen -r hostname -f keyfile -g
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where "hostname" is your fully qualified hostname and "keyfile" is the
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file containing the public host key file. If you have multiple keys,
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you should generate one RR for each key.
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In the example above, ssh-keygen will print the fingerprint in a
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generic DNS RR format parsable by most modern name server
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implementations. If your nameserver has support for the SSHFP RR
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you can omit the -g flag and ssh-keygen will print a standard SSHFP RR.
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To publish the fingerprint using the DNS you must add the generated RR
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to your DNS zone file and sign your zone.
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(2) Client: Enable ssh to verify host keys using DNS
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To enable the ssh client to verify host keys using DNS, you have to
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add the following option to the ssh configuration file
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($HOME/.ssh/config or /etc/ssh/ssh_config):
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VerifyHostKeyDNS yes
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Upon connection the client will try to look up the fingerprint RR
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using DNS. If the fingerprint received from the DNS server matches
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the remote host key, the user will be notified.
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Jakob Schlyter
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Wesley Griffin
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$OpenBSD: README.dns,v 1.2 2003/10/14 19:43:23 jakob Exp $
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