Re: Shell-quoting issue for sshx/scpx on MS Windows

[Jim Porter]

On Wed, Apr 14, 2021 at 4:30 AM Michael Albinus <michael.albinus@gmx.de> wrote:
>
> Jim Porter <jporterbugs@gmail.com> writes:
>
> Hi Jim,
>
> >> Doesn't work. Do you have an idea, which kind of quoting for the remote
> >> target I need?
> >
> > I haven't spent too much time looking at the scp method under MS
> > Windows, but I know there have been some changes to Win32-OpenSSH that
> > might affect things here. In v7.9.0.0p1-Beta[1], the quoting logic was
> > improved (see the "Rich command-line support..." bullet point in the
> > release notes for details). This might fix the issue you're seeing.
>
> Thanks, this looks helpful!

I tested out Win32-OpenSSH v8.1, and the quoting issue hasn't been
resolved. In fact, it's somewhat worse. I found that you can escape
the spaces like so:

  scp "server:~/'foo bar.txt'" dest.txt          (1)

However, newer versions of OpenSSH have strict filename checking, and
the single-quotes run afoul of that check. You can add `-T' to disable
that, but older versions of OpenSSH don't support that flag, so you'd
have to check the version in use to decide whether to add `-T'. I
think it would be a lot better if you could escape the space more like
you would on a Linux system, something like:

  scp "server:~/foo\ bar.txt" dest.txt          (2)

Then the escaping logic in Tramp could look something like
`(client-escape (remote-escape filename))', where `remote-escape'
would use backslashes to escape special characters, and
`client-escape' would then apply the usual shell-escaping logic for
the local system. Since (as I understand it), Tramp requires the
server side of the SSH connection to be POSIXy, that would be
sufficient if Win32-OpenSSH worked correctly. Hopefully that explains
things well enough; these escaping rules are a bit complicated.

I filed an issue on the Win32-OpenSSH repo to request that scp accept
the example (2) above:
https://github.com/PowerShell/Win32-OpenSSH/issues/1790

- Jim