SSHDoor

An LD_PRELOAD wrapper to hide a network service (typically SSH) behind another.

Usage

Edit sshdoor.c and adjust according to your needs:

• Change trigger to whatever secret value in the beginning of the stream should trigger the alternate service. The default of SSH-2.0- is fine for SSH. You want this to be as short as possible

• Change program to whichever service you wish to run. Note that for ssh, the server must be run as root. You can use { "sshd", "-i" } for minimal overhead. Another easy alternative is to use {"nc", "-q0", "localhost", "22"} to defer to an already-running sshd.

Compile the wrapper:

make

Edit your service scripts to set LD_PRELOAD=/path/to/sshdoor.so