Filename: //usr/share/doc/openssh-sftp-server/README.dns

How to verify host keys using OpenSSH and DNS --------------------------------------------- OpenSSH contains support for verifying host keys using DNS as described in https://tools.ietf.org/html/rfc4255. The document contains very brief instructions on how to use this feature. Configuring DNS is out of the scope of this document. (1) Server: Generate and publish the DNS RR To create a DNS resource record (RR) containing a fingerprint of the public host key, use the following command: ssh-keygen -r hostname -f keyfile -g where "hostname" is your fully qualified hostname and "keyfile" is the file containing the public host key file. If you have multiple keys, you should generate one RR for each key. In the example above, ssh-keygen will print the fingerprint in a generic DNS RR format parsable by most modern name server implementations. If your nameserver has support for the SSHFP RR you can omit the -g flag and ssh-keygen will print a standard SSHFP RR. To publish the fingerprint using the DNS you must add the generated RR to your DNS zone file and sign your zone. (2) Client: Enable ssh to verify host keys using DNS To enable the ssh client to verify host keys using DNS, you have to add the following option to the ssh configuration file ($HOME/.ssh/config or /etc/ssh/ssh_config): VerifyHostKeyDNS yes Upon connection the client will try to look up the fingerprint RR using DNS. If the fingerprint received from the DNS server matches the remote host key, the user will be notified. Jakob Schlyter Wesley Griffin $OpenBSD: README.dns,v 1.2 2003/10/14 19:43:23 jakob Exp $

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