upstream commit

Add 'reverse' dynamic forwarding which combines dynamic
forwarding (-D) with remote forwarding (-R) where the remote-forwarded port
expects SOCKS-requests.

The SSH server code is unchanged and the parsing happens at the SSH
clients side. Thus the full SOCKS-request is sent over the forwarded
channel and the client parses c->output. Parsing happens in
channel_before_prepare_select(), _before_ the select bitmask is
computed in the pre[] handlers, but after network input processing
in the post[] handlers.

help and ok djm@

Upstream-ID: aa25a6a3851064f34fe719e0bf15656ad5a64b89

1 files changed, 11 insertions, 5 deletions

diff --git a/ssh_config.5 b/ssh_config.5
index ca5a41103..eab8dd01c 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh_config.5,v 1.255 2017/09/04 06:34:43 jmc Exp $
-.Dd $Mdocdate: September 4 2017 $
+.\" $OpenBSD: ssh_config.5,v 1.256 2017/09/21 19:16:53 markus Exp $
+.Dd $Mdocdate: September 21 2017 $
 .Dt SSH_CONFIG 5
 .Os
 .Sh NAME
@@ -1298,13 +1298,19 @@ accept the tokens described in the
 section.
 .It Cm RemoteForward
 Specifies that a TCP port on the remote machine be forwarded over
-the secure channel to the specified host and port from the local machine.
+the secure channel.
+The remote port may either be fowarded to a specified host and port
+from the local machine, or may act as a SOCKS 4/5 proxy that allows a remote
+client to connect to arbitrary destinations from the local machine.
 The first argument must be
 .Sm off
 .Oo Ar bind_address : Oc Ar port
 .Sm on
-and the second argument must be
-.Ar host : Ns Ar hostport .
+If forwarding to a specific destination then the second argument must be
+.Ar host : Ns Ar hostport ,
+otherwise if no destination argument is specified then the remote forwarding
+will be established as a SOCKS proxy.
+.Pp
 IPv6 addresses can be specified by enclosing addresses in square brackets.
 Multiple forwardings may be specified, and additional
 forwardings can be given on the command line.