Limiting an authorized key to scp access

[dknodel at csc.com.au]

Hi.
      I've attempted to restrict a certain authorized key to running scp
(using the command=... prefix), but without much luck; has anyone set this
up before?  I'm not sure if it's because scp on the server end gets command
line parameters, or for some other reason.

I've fallen back to using sftp instead, which I have been able to restrict
an authorized key to, but the transfer rates I get through sftp are vastly
slower than through scp (which didn't make sense to me either; if anyone
had an idea why that might be, or has done some comparisons and found them
not to be as different as I have, I'd appreciate the information).

I'll also soon be trying to set up a key restricted to rsync over ssh, but
I may run into a command-line parameter issue in the command=... prefix
(I'm not sure if the rsync server process gets invoked with any arguments
or not).


Thanks for any information...
David Knodel