Deprecation of scp protocol and improving sftp client

[Andreas Schneider]

On Tuesday, 16 June 2020 20:47:24 CEST Colin Watson wrote:
> On Tue, Jun 16, 2020 at 06:41:09PM +0200, Jakub Jelen wrote:
> >  * Change scp to use sftp internally
> 
> As an existence proof, pscp (from PuTTY) does exactly this; it tries the
> sftp protocol and falls back to the scp protocol if that fails, and it
> has -scp or -sftp options to force one or the other.  I've long meant to
> get round to putting something similar for OpenSSH, but never got far
> enough to really be worth mentioning.  (Of course it would still need to
> retain scp "source" and "sink" modes if invoked with -f or -t, to retain
> compatibility, since those are used on the server when an scp client
> connects; but there's no particular obstacle to that.)
> 
> >  * Modify sshd to use some compatibility "scpd" to support old clients
> 
> This should be unnecessary.  When an scp client connects to an scp
> server, it passes the -f (source) or -t (sink) flag as appropriate;
> neither is part of the documented user-facing interface to scp.  I don't
> see any particular reason why scp (the program) couldn't continue to
> speak the scp protocol when invoked with -f/-t, but speak the sftp
> protocol when invoked in the normal way.

It is necessary. If you replace the protocol of the scp command with sftp then 
there are still scp commands out there speaking the scp protocol. You need to 
keep the server side supported.


	Andreas

-- 
Andreas Schneider                 asn at cryptomilk.org
GPG-ID:     8DFF53E18F2ABC8D8F3C92237EE0FC4DCC014E3D