scp between two remote hosts

[Peter Watkins]

On Fri, Jan 18, 2002 at 03:53:58PM -0000, Shih, Robert wrote:

> I am running openssh (OpenSSH_2.9p1, SSH protocols 1.5/2.0).  The scenario
> is that I have got three machines (A, B and C).  The sshd on host A is
> listensing on port 1234, and the sshd on host B is listensing on port 5678.
> How can I set up a scp from a third host C so as to copy a file from host A
> to host B?

You'll have to be creative, I think.

> scp -P 1234 myname at A:/var/tmp/file1 -P 5678 myname at B:/var/tmp/file1

 ssh -p 1234 myname at A "scp -P 5678 /var/tmp/file1 myname at B:/var/tmp/file1"

You'd probably need to use keypair, shosts, etc. to authenticate A -> B.

 ssh -p 1234 myname at A "cat /var/tmp/file1" | ssh -p 5678 myname at B "cat > /var/tmp/file1"

I think either of those tricks would work. The first is more efficient, as 
the data only crosses the network once, but authentication may be sticky; it 
doesn't work for me if A -> B needs interactive password authentication.
The second is more likely to work easily, but the file had to go through
A -> C and C -> B, which is a waste of bandwidth, and might not work, as 
you never said whether C could communicate directly with B.

The second trick definitely works, though with my 2.5.2p2 systems, using 
password auth for both C -> A and C -> B connections, my terminal prompts me 
for both passwords on the same line. I enter one, press return, and then the 
other, ad pres return. The second password I type is echoed to my screen. 
Oops. Maybe someone could try that with the latest release and/or CVS?

-Peter