Connecting via a web client using a web proxy

[AlexanderZhirov]

I have a large number of embedded systems that use Dropbear as an SSH server. The task is to make them freely accessible using a web application. To do this, I have developed an internal site in which I want to implement an SSH client based on web sockets. For this purpose, I used a ready-made open source product SSHy. Since he was not active in development for a long time, I used a modified fork of this project. I used websockify as a proxy server.

The problem is that there is a hang during the connection process. As far as my knowledge allows me to understand all this, I mean that the problem is in the handshake process - at some stage of the packet exchange, some kind of failure occurs somewhere. I can't quite identify it, because I don't fully understand the whole concept of SSH.

Using tcpdump, I took a packet dump. It can be seen that the connection is happening, but the process freezes.

On the server side, you can also see that the connection is taking place and the Dropbear child process appears.

I tried to join the OpenSSH server using this client and the connection was successful. I mean that the exchange process happens somehow differently. And how exactly - I can't understand. I ask for guru's help.

pcap dropbear connection file

[mkj]

I've made a try at fixing the SSHy version parsing, though couldn't get index.html to work with my websocksify (didn't even get to connecting) - you can see if it works or modify as required.

[AlexanderZhirov]

@mkj For some reason, the utility does not quite correctly create a library for me. It will be necessary to try again.

I'll try again and write to you later. Thank you very much!

[AlexanderZhirov]

@mkj No, after all, the library was assembled correctly, without errors, but, for some reason, with 4 warnings.

/usr/lib/openjdk-8/bin/java -jar closure-compiler.jar --js_output_file=combinedJS.comb.js js/defines.js js/src/*.js js/*.js '!**.comb.js'
...
0 error(s), 4 warning(s)

At the same time, there were even more errors. I suspect that the error most likely occurs at the initialization stage.

I'm using a template wrapper.html. It uses the combinedJS.comb.js, so I build it through java

...
	<script type="text/javascript">
		var wsproxyURL = "ws://46.72.31.224:2222"
		setProxyEncoding("binary");
	</script>
...

I have websockify running on port 2222 in Docker. It redirects to port 22 on Dropbear.

You can check. You can not create a proxy for yourself, but use mine, which will knock on Dropbear. I keep it all on virtual machines, so access is open.

• 46.72.31.224:22 - DropBear
• 46.72.31.224:2222 - Websockify => Dropbear:22

user:     root
password: poOZp*ZTK-69Y

[mkj]

Seems to be working now with SSHy changes discussed in mkj/SSHy@7ac3941

[AlexanderZhirov]

Thanks! 😃