Re: cygport upload: patch for openssh 6.8p1

[Andrew Schulman <schulman.andrew@epa.gov>]

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> On Sun, 2015-05-24 at 12:32 -0400, Andrew Schulman wrote:
> > Since the latest update to openssh, ssh-keygen's output format for key
> > fingerprints has changed.  The default hash algorithm is now base64-encoded
> > SHA256 instead of MD5, and the hash name precedes its value, like
> > 
> >     SHA256:lvRrjAXmEhzDp5kQqzelsei8s5hXJ+zLaqJ2yiGXmYc
> > 
> > This breaks the current logic for detecting key fingerprints in cygport's
> > lib/pkg_upload.cygpart.  The attached patch fixes the problem.  (You might know
> > a more precise regex for the base64-encoded hash value than I do.  I couldn't
> > find any documentation of it anywhere, and just settled for
> > 
> >     SHA256:.{44}
> 
> There's another problem: this is new to 6.8; any out-of-date Cygwin
> systems, or even current RHEL or Fedora 21 systems, won't have this, nor
> do they support the -E flag which could be used to specify md5.
> 
> Any thoughts on a better regex or on keeping compatibility with other
> systems?

Right, OK.  See the attached revised patch, which uses

  [0-9a-f]{2}(:[0-9a-f]{2}){15}|SHA256:.{44}

to detect the key fingerprint.  The left side is the same as now, for pre-6.8
systems, which use MD5 without a label.  The right side is for version 6.8 and
later, where the default is SHA256 with the label 'SHA256:' prepended.  So this
should cover all cases.

Andrew

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--- lib/pkg_upload.cygpart	2015-03-23 02:05:43.493625000 -0400
+++ lib/pkg_upload.cygpart	2015-05-24 12:15:31.969700900 -0400
@@ -74,7 +74,7 @@
 		if ssh-add -l >/dev/null 2>/dev/null
 		then
 			# ssh-agent is already running. Get key fingerprint:
-			key_fingerprint=$(ssh-keygen -l -f "$SSH_KEY" | egrep -o '[0-9a-f]{2}(:[0-9a-f]{2}){15}') \
+			key_fingerprint=$(ssh-keygen -l -f "$SSH_KEY" | egrep -o '[0-9a-f]{2}(:[0-9a-f]{2}){15}|SHA256:.{44}') \
 			|| error "Can't read key fingerprint of ${SSH_KEY}. Not a private key file, or corresponding public key file is missing?"
 
 			# Load key into ssh-agent, if it's not already loaded (prompts for passphrase):