choice of fingerprint display upon new host access

Daniel Kahn Gillmor dkg at
Tue Apr 20 04:48:00 EST 2010

When a user encounters a new ssh host, the VisualHostKey option makes
ssh display the visual fingerprint of the host's key.

ssh-keygen also supports BubbleBabble fingerprinting, but i don't see a
way to indicate that ssh should display the bubblebabble fingerprint
upon encountering a new host key.

It seems like it would be nice to make OpenSSH configurable about its
choice of fingerprinting scheme without adding a new option for every
possible flavor of fingerprinting.  In particular, i'm not proposing
that we include a BubbleBabbleHostKey option to ssh_config.

What do people think of the following approach for ssh_config:

 HostKeyFingerprint is an option which takes a comma-separated set of
fingerprint styles to display to the user upon seeing a new host key.
Supported options are: "hex", "bubblebabble", "visual"

   The default is: hex

For backward compatibility, -oVisualHostKey=yes implicitly adds "visual"
to this set if it is not already present.

If people think this is a good idea, i'll open a bugzilla ticket about
it.  I'm also interested to hear if people have any objections to the idea.



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