Dec 22, 2017

scp between two remote hosts from 3rd host

scp [email protected]:/home/user1/file1.txt [email protected]:/home/user2/file1.txt
 use the -3 option, as follows:

    scp -3 [email protected]:/home/user1/file1.txt [email protected]:/home/user2/file1.txt

The -3 option instructs scp to route traffic through the PC on which the command is issued, even though it is a 3rd party to the transfer. This way, authorization credentials must reside only on the issuing PC, the third party.