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https://github.com/stealth/sshttp

SSH/HTTP(S) multiplexer. Run a webserver and a sshd on the same port w/o changes.
https://github.com/stealth/sshttp

http https ipv6 ssh ssh-traffic sshttp tls

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SSH/HTTP(S) multiplexer. Run a webserver and a sshd on the same port w/o changes.

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README 

        
sshttp - hiding SSH servers behind HTTP

=======================================










## 0. Intro



In case your FW policy forbids __SSH__ access to the DMZ or internal

network from outside, but you still want to use ssh on machines

which only have one open port, e.g. __HTTP__, you can use `sshttpd`.



_sshttpd_ can multiplex the following protocol pairs:



* SSH/HTTP

* SSH/HTTPS

* SSH/SMTP (without SMTP multiline banners)

* HTTPS SNI multiplexing

* SSH/HTTPS with SNI multiplexing



## 1. Build



Be sure you run recent Linux kernel and install `nf-conntrack` as well

as `libcap` and `libcap-devel` if you want to use the capability feature.

On older systems the nf-conntrack module is named nf-conntrack-ipv4.



Inside `src` dir:

```

$ make

```



There is a new `splice` branch inside the git. `git checkout splice`

before `make`, if you want to test this new branch. It implements

zero-copy in terms of the __splice(2)__ system call which has a performance

benefit since it avoids copying the network data between user and kernel

land back and forth (__read()/write()__), which could also just be spliced kernel-internally

at the "extra cost" of two additional pipe descriptors per connection.



*proudly sponsored by:*












## 2. Setup for single host



This paragraph describes the setup where all services run on the same host

as _sshttpd_ itself. The muxing happens to the same IP/IP6 address that

the outside connects arrive to, so basically just the ports are changing per

detected service.



_sshttpd_ is an easy to use OSI-Layer5 switching daemon. It runs

transparently on __HTTP(S)__ port (`-L` switch, default 80) and decides

on incoming connections whether this is __SSH__ or __HTTP(S)__ traffic.

If its __HTTP(S)__ traffic, it switches the traffic to the `HTTP_PORT`

(`-H`, default 8080) and if its __SSH__ traffic to `SSH_PORT` (`-S`, default

22) respectively.



After the build it is time to pick the right netfilter script for setting up the fw rules.

In `iptables` directory you will find the old style *iptables* version and in `nft`

the new version for *nft* (but currently only using the compat layer).



You need to edit `nf-setup` script (`nf6-setup`if using IPv6) to match your network device and `$PORTS` (`22` and `8080`

are just fine for the SSH/HTTP case) and run it to install the proxy rules.

Your _sshd_ has to run on `$SSH_PORT` and your webserver on `$HTTP_PORT`.

Thats basically it. Go ahead and run _sshttpd_ (as root) and it will layer5-switch

your traffic destinated to TCP port 80:



**_Take care when running nf-setup on a remote host in an SSH session - it will firewall port 22_**



```

# ./nf-setup

Using network device eth0

Setting up port 22 ...

Setting up port 8080 ...

# ./sshttpd -S 22 -L 80 -H 8080 -U nobody -R /var/empty

sshttpd: Using HTTP_PORT=8080 SSH_PORT=22 and local port=80. Going background. Using caps/chroot.

#

```



If you want to mux __SMTP__ with _sshttpd_, just give `25` as `-L` parameter, `2525`

as `-H` parameter, and setup your smtp daemon to listen on 2525. Then

edit the `nf-setup` script to match these ports. In the `Makefile`, change the

`SMTP_DOMAIN` and `SSH_BANNER` to your needs (`SSH_BANNER` must match exactly

yours of the running _sshd_).

SMTP/SSH muxing was tested with OpenSSH client and Postfix client and server.



When muxing IPv6 connections, the setup is basically the same; just use the `nf6-setup`

script and invoke _sshttpd_ with `-6`.



## 3. Transparent proxy setup



You can run _sshttpd_ also on your gateway machine and transparently proxy/mux

all of your __HTTP(S)/SSH__ traffic to your internal LAN. To do so, run _sshttpd_ with

`-T` and use `nf-tproxy` rather than `nf-setup` as a template for your FW setup.

Carefully read `nf-tproxy` so you don't lock yourself out of the network and all

the network devices and IP addresses match your setup.



## 4. SNI Mux



With _sshttpd_ you can also mux based on the HTTPS SNI. Just set up your

`nf-setup` to contain the SNI ports (there are already samples) and invoke

_sshttpd_ with `-N name:port` e.g. `sshttpd -S 22 -H 4433 -L 443 -N drops.v2:7350`

to hide a sshd on 22 and a [drops setup](https://github.com/stealth/drops) on port 7350 behind port 443, and at the same time serving

your webserver from port 4433 to be visible to outside on port 443.

This works because _drops_ sets the SNI of `drops.v2` in outgoing connects.

Multiple `-N` switches are allowed so you could mux a lot of services

via SNI. The ports/services must run all on the same machine where the original request

was destinated to. If you just want to mux based on SNI, you can set the SSH port to 0 via `-S 0`.



## 5. Misc



You don't need to patch any of your ssh/web/smtp client or server software. It

works as is. _sshttpd_ runs only on Linux and needs `IP_TRANSPARENT` support.

It would work without, but by using `IP_TRANSPARENT` it is possible to even

have unmodified syslogs, e.g. the original source IP/port of incoming connections

is passed as-is to the SSH/HTTP/SMTP servers.



Make sure the `nf_conntrack` and `nf_conntrack_ipv4` or `nf_conntrack_ipv6` modules are loaded.

_sshttpd_ is also a tricky anti-SSH0day (if ever:) and anti SSH-scanning/bruteforcing

measurement.

_sshttpd_ has small footprint and was optimized for speed so it also runs

on heavily loaded web servers.



Since version 0.24, _sshttpd_ also supports multiple CPU cores. Unless

`-n 1` is used as switch, _sshttpd_ binds one thread per CPU core,

to better exploit the hardware if running on heavily used web servers.

It still runs this fixed number of threads no matter how many 1000s connection

it handles at the same time.

_sshttpd_ runs as `nobody` user inside a `chroot()` (configurable via `-U` and `-R` switch)

if compiled with `USE_CAPS`. It can also distinguish between __SSH__ and __SSL__

sessions, you just have to use an `LOCAL_PORT (-L)` of 443 or 4433 and change

the `HTTP_PORT` in the `nf-setup` script to match your webservers __HTTPS__ port.

You cannot mix HTTP/SSH and HTTPS/SSH in one _sshttpd_ instance but you can

run two sshttpd's to reach that goal: one on `LOCAL_PORT 80` and one on

`LOCAL_PORT 443`.



## 6. Alternative docu



As per 2017 it seems you have to provide alternative facts for everything,

so here are some good writeups from other people for better understanding or in case my

description was too brief:



* [by stalkr](http://blog.stalkr.net/2012/02/sshhttps-multiplexing-with-sshttp.html)

* [by Will Rouesnel](http://blog.wrouesnel.com/articles/Setting%20up%20sshttp/)

* [by Yves](http://yalis.fr/cms/index.php/post/2014/02/22/Multiplex-SSH-and-HTTPS-on-a-single-port)