sslh [ -tnum ] [-plistening address] [-ltarget address for SSL] [-starget address for SSH] [-uusername] [-Ppidfile] [-v] [-i] [-V]
sslh lets one accept both HTTPS and SSH connections on
the same port. It makes it possible to connect to an SSH
server on port 443 (e.g. from inside a corporate firewall,
which almost never block port 443) while still serving HTTPS
on that port.
The idea is to have sslh listen to the external 443 port,
accept the incoming connections, work out what type of
connection it is, and then fordward to the appropriate
The protocol detection is made based on a small difference
between SSL and SSH: an SSL client connecting to a server
speaks first, whereas an SSH client expects the SSH server
to speak first (announcing itself with a banner). sslh
waits for some time for the incoming connection to send data.
If it does before the timeout occurs, it is supposed to be
an SSL connection. Otherwise, it is supposed to be an SSH
One drawback of sslh is that the ssh and httpd
servers do not see the original IP address of the client
anymore, as the connection is forwarded through sslh.
sslh provides enough logging to circumvent that problem.
However it is common to limit access to ssh using
libwrap or tcpd. For this reason, sslh can be
compiled to check SSH accesses against SSH access lists as
defined in /etc/hosts.allow and /etc/hosts.deny.
Timeout before a connection is considered to be SSH. Default
Interface and port on which to listen, e.g. foobar:443,
where foobar is the name of an interface (typically the
IP address on which the Internet connection ends up).
Defaults to 0.0.0.0:443 (listen to port 443 on all
-ltarget address for SSL
Interface and port on which to forward SSL connection,
Defaults to localhost:443 (this assumes you would
configure your httpd process to listen to port 443).
Note that you can set sslh to listen on ext_ip:443 and
httpd to listen on localhost:443: this allows clients
inside your network to just connect directly to httpd.
-starget address for SSH
Interface and port on which to forward SSH connection,
defaults to localhost:22.
Prints sslh version.
Requires to run under the specified username. Defaults to
nobody (which is not perfect --- ideally sslh should
run under its own UID).
Specifies the file in which to write the PID of the main
server. Defaults to /var/run/sslh.pid.
Runs as an inetd server. Options -P (PID file), -p
(listen address), -u (user) are ignored.
Start-up script. The standard actions start, stop and
restart are supported.
Server configuration. These are environment variables
loaded by the start-up script and passed to sslh as
command-line arguments. Refer to the OPTIONS section for a
detailed explanation of the variables used by sslh.