Black Hat 2024: Secure Shells in Shambles [pdf]
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Black Hat 2024: Secure Shells in Shambles [pdf]
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Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#2The Secure Shell (SSH) protocol has survived as an internet-facing management protocol for almost 30 years. Over the decades it has transformed from a single patented codebase to a multitude of implementations available on nearly every operating system and network-connected device.
This presentation dives deep into the Secure Shell protocol, its popular implementations, what's changed, what hasn't, and how this leads to unexpected vulnerabilities and novel attacks. An open source tool, dubbed "sshamble", will be demonstrated, which reproduces these attacks and opens the door for further research.
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#3SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop
> SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to connect to services such as SSH in order to make the exploitation of vulnerabilities (both 0-day and unpatched code) more difficult.
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#4SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to conne…
Every now and then I use GnuPG encrypted emails (or a web form) to my servers to open the firewall for certain IP addresses. If the server can decrypt such a message it can safely act on it.
The server's default is to only allow certain network ranges to access certain ports, e.g. from my local providers or employers networks.
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#5SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to conne…
That is interesting! Is this widely used or are there downsides I am not seeing?
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#6SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to conne…
So instead of exposing thoroughly tested OpenSSH to the web, I’m exposing this thing, which can also run shell commands…
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#7SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to conne…
That is interesting! Is this widely used or are there downsides I am not seeing?
Dependencies of reliable Pinholing-by-SMTP are but not limited to:
- reliable SMTP hopping
- a working SMTP account
- pinholer is up and running and robust against DoS/DDoS.
- replayability of PGP (use TOTP in original message as well as wrapper of encrypted SMTP payload)
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#8SSH and other services can be further protected by Single Packet Authentication (SPA), https://github.com/mrash/fwknop > SPA requires only a single packet which is encrypted, non-replayable, and authenticated via an HMAC in order to communicate desired access to a service that is hidden behind a firewall in a default-drop filtering stance. The main application of SPA is to use a firewall to drop all attempts to conne…
So instead of exposing thoroughly tested OpenSSH to the web, I’m exposing this thing, which can also run shell commands…
There are many points made in the presentation, including that a significant number of ~~targets~~ hosts are not running OpenSSH. See the list and the claims that some classes of them are important.
The swipe at "running shell commands" isn't very credible, but the second attack surface is legitimate.
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#9Earlier quoted context omitted.
So instead of exposing thoroughly tested OpenSSH to the web, I’m exposing this thing, which can also run shell commands…
There are many points made in the presentation, including that a significant number of ~~targets~~ hosts are not running OpenSSH. See the list and the claims that some classes of them are important. The swipe at "running shell commands" isn't very credible, but the second attack surface is legitimate.
4th bullet from the bottom sounds credible to me:
> Supports the execution of shell commands on behalf of valid SPA packets.
Even if it were only a statically configured command (no idea if it is or isn't), as soon as that door is opened, it leads to a morass.
Re: Black Hat 2024: Secure Shells in Shambles [pdf]
#10The Secure Shell (SSH) protocol has survived as an internet-facing management protocol for almost 30 years. Over the decades it has transformed from a single patented codebase to a multitude of implementations available on nearly every operating system and network-connected device. This presentation dives deep into the Secure Shell protocol, its popular implementations, what's changed, what hasn't, and how this leads…
I didn't realise the old ssh.com codebase was patented, apart from crypto patents like RSA (or IDEA?)