Re: Way to print fingerprint of a key in your known_hosts file?

On Tue, 22 Jun 2010, Dan Mahoney, System Admin wrote:

> Hello there,
>
> The subject line says it all, really.  How can I take a line from my 
> known-hosts file, and print the fingerprint of the thing.
>
> Right now, I can extract it from my known-hosts file with ssh-keygen -F and 
> redirect that to a temporary file, and then run ssh-keygen -l, over it, or 
> ssh-keygen -l -v, or ssh-keygen -B...
>
> I note that -l will not print a fingerprint if -B is on the same line.  -B 
> seems to override -l (regardsless of which comes first).
>
> I also note that -v prints the ascii art representation when used with -B 
> alone, though the manpage makes no reference to this intercompatibility.
>
> Regardless, doing it in one sweep (extracting and fingerprinting) still 
> requires that intermediate step.  ssh-keygen doesn't seem to accept the 
> standard -f - (stdin) argument, nor can I say -f /dev/stdin
>
> So I suppose there are a few questions.
>
> 1) Does anyone have a better way to do this?
>
> 2) Is it worth filing feature requests to modify -f to accept stdin?
>
> 3) Is it worth filing a feature request to make -l and -B usable in the same 
> command?
>
> 4) Or in fact for those commands to work with -F, meaning "find any key 
> matching foo in my known_hosts and print the fingerprint in this format".

To followup, it looks like -F works with -l, or -B, and in either case, -v 
causes the ascii-art to be shown as well, but -l and -B being mutually 
exclusive seems like a bug.

Also, the manpage usage syntax is off:

Instead of:

ssh-keygen -l [-f input_keyfile]
ssh-keygen -B [-f input_keyfile]
ssh-keygen -F hostname [-f known_hosts_file]

It should might say:

ssh-keygen -l [-v] [-f input_keyfile]
ssh-keygen -B [-v] [-f input_keyfile]
ssh-keygen -F [[-B |-l ] -v] hostname [-f known_hosts_file]

And the usage statements for the l, B, and F options should note that 
these are chainable.

Should I open bug reports?

-Dan

-- 

"I wish the Real World would just stop hassling me!"

-Matchbox 20, Real World, off the album "Yourself or Someone Like You"


--------Dan Mahoney--------
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