An issue in Unix virtual private networks was disclosed recently, where an attacker could potentially hijack a TCP stream, even though that stream is inside the VPN. This attack affects OpenVPN, Wireguard, and even IPSec VPNs. How was this possible? Unix systems support all manner of different network scenarios, and oftentimes a misconfiguration can lead to problems. Here, packets sent to the VPNs IP address are processed and responded to, even though they are coming in over a different interface.
The attack initially sounds implausible, as an attacker has to know the Virtual IP address of the VPN client, the remote IP address of an active TCP connection, and the sequence and ACK numbers of that connection. That’s a lot of information, but an attacker can figure it out one piece at a time, making it a plausible attack. Continue reading “This Week In Security: VPNs, Patch Tuesday, And Plundervault”→
In an era where everything seems to be getting “smarter” every year, it will probably come as no surprise to find that even relatively middling networking hardware is now packing advanced features and considerable computational power. A case in point is the Dell N1108T-ON Ethernet switch. Despite only costing around $100 USD on the second hand market, [Ben Cox] discovered this particular switch was capable of a lot more than what was advertised by poking around its onboard operating system.
It all started by plugging into the serial port on the front of the switch, which [Ben] happily notes is an integrated FTDI USB serial adapter to make life easy. Booting into recovery mode gave him local shell access, and some poking around determines it’s the sort of BusyBox-powered Linux system that you’d expect on an embedded device. The biggest discoveries were that it was running a relatively recent kernel (3.8.1), and that it apparently had Python installed.
From there, [Ben] found out that these switches have a feature where the administrator can install and run Python “applications” by packaging them up as tarballs and copying them from a USB flash drive. So he wrote up a simple Python program that used the socket library to open up a reverse shell to his desktop computer, and to his surprise, it worked perfectly on the first try. Now with root access, the fun really started.
The next step was getting an SSH installed and running on the switch, so that he didn’t have to do the reverse shell trick every time. He then started installing the packages necessary to turn the switch into a secure VPN tunnel with Wireguard. This took a little fiddling as [Ben] didn’t have the option of installing the normal Wireguard kernel module, but he eventually got the necessary tools modified and cross-compiled to ARM. He believes this is just the start of what’s capable on devices like this, and we’re interested in seeing where the community goes from here.