This week Jonathan Bennett and Rob Campbell talk with Gareth Coleman and Hamish Cunningham! It’s all about the Unphone, an open source handset sporting an ESP32, color touchscreen, and LoRa radio. It’s open hardware, and used in a 3rd year university course to teach comp sci majors about hardware and embedded development.
Continue reading “FLOSS Weekly Episode 783: Teaching Embedded With The Unphone”
There’s a clever “new” attack against VPNs, called TunnelVision, done by researchers at Leviathan Security. To explain why we put “new” in quotation marks, I’ll just share my note-to-self on this one written before reading the write-up: “Doesn’t using a more specific DHCP route do this already?” And indeed, that’s the secret here: in routing, the more specific route wins. I could not have told you that DHCP option 121 is used to set extra static routes, so that part was new to me. So let’s break this down a bit, for those that haven’t spent the last 20 years thinking about DHCP, networking, and VPNs.
So up first, a route is a collection of values that instruct your computer how to reach a given IP address, and the set of routes on a computer is the routing table. On one of my machines, the (slightly simplified) routing table looks like:
# ip route
default via 10.0.1.1 dev eth0
10.0.1.0/24 dev eth0
The first line there is the default route, where “default” is a short-hand for 0.0.0.0/0. That indicate a network using the Classless Inter-Domain Routing (CIDR) notation. When the Internet was first developed, it was segmented into networks using network classes A, B, and C. The problem there was that the world was limited to just over 2.1 million networks on the Internet, which has since proven to be not nearly enough. CIDR came along, eliminated the classes, and gave us subnets instead.
In CIDR notation, the value after the slash is commonly called the netmask, and indicates the number of bits that are dedicated to the network identifier, and how many bits are dedicated to the address on the network. Put more simply, the bigger the number after the slash, the fewer usable IP addresses on the network. In the context of a route, the IP address here is going to refer to a network identifier, and the whole CIDR string identifies that network and its size.
Back to my routing table, the two routes are a bit different. The first one uses the “via” term to indicate we use a gateway to reach the indicated network. That doesn’t make any sense on its own, as the 10.0.1.1 address is on the 0.0.0.0/0 network. The second route saves the day, indicating that the 10.0.1.0/24 network is directly reachable out the eth0 device. This works because the more specific route — the one with the bigger netmask value, takes precedence.
The next piece to understand is DHCP, the Dynamic Host Configuration Protocol. That’s the way most machines get an IP address from the local network. DHCP not only assigns IP addresses, but it also sets additional information via numeric options. Option 1 is the subnet mask, option 6 advertises DNS servers, and option 3 sets the local router IP. That router is then generally used to construct the default route on the connecting machine — 0.0.0.0/0 via router_IP.
Remember the problem with the gateway IP address belonging to the default network? There’s a similar issue with VPNs. If you want all traffic to flow over the VPN device, tun0, how does the VPN traffic get routed across the Internet to the VPN server? And how does the VPN deal with the existence of the default route set by DHCP? By leaving those routes in place, and adding more specific routes. That’s usually 0.0.0.0/1 and 128.0.0.0/1, neatly slicing the entire Internet into two networks, and routing both through the VPN. These routes are more specific than the default route, but leave the router-provided routes in place to keep the VPN itself online.
And now enter TunnelVision. The key here is DHCP option 121, which sets additional CIDR notation routes. The very same trick a VPN uses to override the network’s default route can be used against it. Yep, DHCP can simply inform a client that networks 0.0.0.0/2, 64.0.0.0/2, 128.0.0.0/2, and 192.0.0.0/2 are routed through malicious_IP. You’d see it if you actually checked your routing table, but how often does anybody do that, when not working a problem?
There is a CVE assigned, CVE-2024-3661, but there’s an interesting question raised: Is this a vulnerability, and in which component? And what’s the right solution? To the first question, everything is basically working the way it is supposed to. The flaw is that some VPNs make the assumption that a /1 route is a bulletproof way to override the default route. The solution is a bit trickier. Continue reading “This Week In Security: TunnelVision, Scarecrows, And Poutine”
This week Jonathan Bennett and David Ruggles chat with Rak Siva and Steve Demchuck to talk about Nitric! That’s the Infrastructure from Code framework that makes it easy to use a cloud back-end in your code, using any of multiple providers, in multiple programming languages.
The group chatted about the role and form of good documentation, as well as whether a Contributor License Agreement is ever appropriate, and what a good CLA would actually look like. Don’t miss it!
Continue reading “FLOSS Weekly Episode 782: Nitric — In Search Of The Right Knob”
The UK has the answer to all our IoT problems: banning bad default passwords. Additionally, the new UK law requires device makers to provide contact info for vulnerability disclosures, as well as a requirement to advertise vulnerability fix schedules. Is this going to help the security of routers, cameras, and other devices? Maybe a bit.
I would argue that default passwords are in themselves the problem, and complexity requirements only nominally help security. Why? Because a good default password becomes worthless once the password, or algorithm leaks. Let’s lay out some scenarios here. First is the static default password. Manufacturer X makes device Y, and sets the devices to username/password admin/new_Complex_P@ssword1!. Those credentials make it onto a default password list, and any extra security is lost.
What about those devices that have a different, random-looking password for each device? Those use an algorithm to derive that password from the MAC address and/or serial number. That may help the situation, but the algorithm can be retrieved from the firmware, and most serial numbers are predictable in one way or another. This approach is better, but not a silver bullet.
So what would a real solution to the password problem look like? How about no default password at all, but no device functionality until the new password passes a cracklib complexity and uniqueness check. I have seen a few devices that do exactly this. The requirement for a disclosure address is a great idea, which we’ve talked about before regarding the similar EU legislation.
Continue reading “This Week In Security: Default Passwords, Lock Slapping, And Mastodown”
This week Jonathan Bennett and Doc Searls sit down with Mathias Buus Madsen and Paolo Ardoino of Holepunch, to talk about the Pear Runtime and the Keet serverless peer-to-peer platform. What happens when you take the technology built for BitTorrent, and apply it to a messaging app? What else does that allow you to do? And what’s the secret to keeping the service running even after the servers go down?
Continue reading “FLOSS Weekly Episode 781: Resistant To The Wrath Of God”
There’s a trend recently, of big-name security appliances getting used in state-sponsored attacks. It looks like Cisco is the latest victim, based on a report by their own Talos Intelligence.
This particular attack has a couple of components, and abuses a couple of vulnerabilities, though the odd thing about this one is that the initial access is still unknown. The first part of the infection is Line Dancer, a memory-only element that disables the system log, leaks the system config, captures packets and more. A couple of the more devious steps are taken, like replacing the crash dump process with a reboot, to keep the in-memory malware secret. And finally, the resident installs a backdoor in the VPN service.
There is a second element, Line Runner, that uses a vulnerability to arbitrary code from disk on startup, and then installs itself onto the device. That one is a long term command and control element, and seems to only get installed on targeted devices. The Talos blog makes a rather vague mention of a 32-byte token that gets pattern-matched, to determine an extra infection step. It may be that Line Runner only gets permanently installed on certain units, or some other particularly fun action is taken.
Fixes for the vulnerabilities that allowed for persistence are available, but again, the initial vector is still unknown. There’s a vulnerability that just got fixed, that could have been such a vulnerability. CVE-2024-20295 allows an authenticated user with read-only privileges perform a command injection as root. Proof of Concept code is out in the wild for this one, but so far there’s no evidence it was used in any attacks, including the one above. Continue reading “This Week In Security: Cisco, Mitel, And AI False Flags”
This week Jonathan Bennett and Aaron Newcomb chat with Isaac Connor about Zoneminder! That’s the project that’s working to store and deliver all the bits from security cameras — but the CCTV world has changed a lot since Zoneminder first started, over 20 years ago. The project is working hard to keep up, with machine learning object detection, WebRTC, and more. Isaac talks a bit about developer burnout, and a case or two over the years where an aggressive contributor seems suspicious in retrospect. And when is the next stable version of Zoneminder coming out, anyway?
Continue reading “FLOSS Weekly Episode 780: Zoneminder — Better Call Randal”
