remote restricted bash does not allow hopping?

Hi,

I'm trying to enable a one-hop login to a remote network to which I
need to go first through a ssh login host, which provides only an rbash
shell and there is no access to standard commands. As far as I can
tell only 'ssh' command works in that server.

When I try to open a file in a host behind the restricted login server
I'm requested for my password (as expected) but then tramp stuck
for ever on 'Found remote shell prompt...' and I never get a dired
buffer on the remote file system.

If I enable tramp-verbose on 10 then I can see one line that repeats
at different moments:

 -rbash: exec: restricted

'exec' is indeed not available in my login server. Is this the
problem? Is there a local tramp based work around?

thanks,
 Rodrigo