ssh-mitm VS BDFProxy

I wanted to share some insights into a security concern that echoes the Terrapin-Attack scenario, highlighting a similar vulnerability that has been observed in other tools.

Recently, I came across a Pull Request on GitHub for the SSH-MITM tool, which sheds light on a critical aspect of SSH protocol security, specifically regarding RFC 4253 during the KEXINIT process. The Pull Request, available at GitHub https://github.com/ssh-mitm/ssh-mitm/pull/163, describes the necessity of discarding certain packages during the KEXINIT phase to prevent issues with intercepted clients.

Moreover, a look into the GitHub Blame for SSH-MITM reveals that these crucial changes in the KEXINIT step were integrated into SSH-MITM about 1-2 years ago. You can see the specific changes at this link: https://github.com/ssh-mitm/ssh-mitm/blame/4fc3ef418847c35d17d0c427e2701b33a03c323c/sshmitm/workarounds/transport.py#L178-L188

An important note to add is that this information suggests that a similar form of attack, akin to the Terrapin-Attack, could potentially have been exploited for the last two years. This raises significant concerns about the historical vulnerability of systems to such attack techniques and emphasizes the importance of retroactive security analysis in addition to ongoing vigilance.

There is now an issue ticket in ssh-mitm to discuss the similarities between ssh-mitm and terrapin attack: https://github.com/ssh-mitm/ssh-mitm/issues/165

During some audits, it's likely that you find some ssh public keys laying around on some servers.

If you want to verify if this key is known by other services, but you don't have access to those services, this task might be hard.

SSH-MITM has an additional command, which allows to check if a public ssh key is known by GitHub, GitLab, and other code hosters. It's not limited to GitHub and other major platforms and even works with each service, which is accessible over SSH.

First you must install SSH-MITM. It's recommended to use the AppImage, because this works out of the box on most Linux machines.

$ wget https://github.com/ssh-mitm/ssh-mitm/releases/latest/download/ssh-mitm-x86_64.AppImage

SSH-MITM is a tool to audit ssh sessions and protocols, which uses SSH as the transport protocol: https://github.com/ssh-mitm/ssh-mitm

you can find the project on github: https://github.com/ssh-mitm/ssh-mitm

You should check the Revisionhistory of the Readme file first.. https://github.com/ssh-mitm/ssh-mitm/commit/564028af25c395528446fbb679c7392469d59bfd

The “customized wording” you’re seeing is “The LGPL”. It’s a different license from the GPL.

The history on the repo shows that the original license was GPL (June 2020), the author changed the license to LGPL (December 2022), and now they’re changing it to GPL again. https://github.com/ssh-mitm/ssh-mitm/commits/master/LICENSE

for same sort of thing but not lisp, see backdoor factory that will backdoor any .exe you download over connection that attacker is MITMing. attacker doesn't need to know what specific library you will download from quicklisp, they write a mitmproxy script like that so for any download from quicklisp.org, it opens the .tar.gz, adds some malicious lisp to it (probably that just executes shell command to download and execute their normal malware, password stealer or whatever as I don't think they going to write full malware in lisp), repack it as .tar.gz you were requesting and serve it to you. It's not the same issue as phishing where they email saying please open and run attachment.exe and you click through all the warnings that you are doing something dangerous and about to run untrusted code. You just use quicklisp as you normally do, if you install any package, when an attacker can MITM your connection they can run code on your computer. Yes that is sometimes also possible with browser exploit but browsers have multiple layers of sandbox and protections against it, and when someone finds a vulnerability that gets through it is treated as a serious vulnerability to fix. some of this thread seems people saying well nothing is perfectly secure a sufficiently pacient, skilled, well-funded attacker can always get through somehow, so it doesn't matter raising the bar off the floor by not using http unverified to download code we run on people's computer

Have you seen this mitmproxy plugin: https://github.com/secretsquirrel/BDFProxy They use mitmproxy to capture and replace software auto-updates.