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Parser exploits aside, HTTPS would help ensure the signed image you received was the one you asked for. So say there's an exploitable security flaw in 1.1.5 of
by peeters 10y ago
Parser exploits aside, HTTPS would help ensure the signed image you received was the one you asked for. So say there's an exploitable security flaw in 1.1.5 of the firmware and the firmware requests an upgrade from http://whatever.com/images/latest.img http://whatever.com/images/latest.img. Someone could return the legitimate 1.1.5 image instead, and assuming no other version validation, cause a downgrade that will allow further attacks.
If you assume there IS further version validation, then the question is how do you know what version you should be expecting without HTTPS?
- okket 10y agoTo prevent downgrade attacks, include a list of banned signatures/hashes of previous versions in an upgrade? Plus only allow higher version numbers? Downside: Reverting is not possible if you make a serious mistake in an upgrade. If you can't initiate another upgrade process, bricking is possible... I don't know much about the world of really small devices aka IoT, but from my laymen perspective: Is a full TLS stack still a huge obstacle there? Sane signature checks are at least a step in the right direction.
- sneak 10y agoA device running 1.0 could still be upgraded to a vulnerable signed 1.1 when a patched 1.2 with blacklist is current on the site.
- 0x0 10y agoA device running a vulnerable signed 1.1 could still be denied an upgrade to 1.2 by a MITM blocking port 443 even if you used HTTPS.
- peeters 10y agoYeah but it's kind of irrelevant because the device is already vulnerable in your example. The point of this was to say that you can turn a safe device into a vulnerable device as part of a multi-phase attack.
- hawski 10y agoGenerate a new package every day or week and include current date. Do not allow to update to package older than X. Synchronize time using one of the time signals available in the area or use signed channel for time sync. Using radio time signal it can be easy to spoof it if your location is known by the intruder, but makes it practically impossible for remote exploits. But radio signals may have bad reception inside a house.
- IshKebab 10y agoSo assuming the version is signed (likely given they seem to have done this competently) the worst an adversary can do is prevent upgrades? They could do that by blocking HTTPS too.
- peeters 10y agoI think so, but I don't think it's actually a correct assumption. The article talks about the list of firmware versions (and where to download them from) as being fetched from a JSON file delivered over HTTP. That json file isn't signed in any way, so you could first intercept that, change the links and expected versions, and you're home free.