← Back to context

Comment by Tharre

9 days ago

No secure element, no memory tagging support, no proper cellular baseband isolation, no verified boot, taking months to ship security updates .. the list is long.

From a security/privacy perspective the fairphone is on the worse side of options unfortunately.

12 comments

Tharre

Reply
neobrain  9 days ago

> From a security/privacy perspective the fairphone is on the worse side of options unfortunately.

Compared to Pixel phones this is without a doubt true, but how does it compare against your average mid-range Android device? Do those typically have any of the features you mentioned?

  • Tharre  9 days ago

    Very roughly, and assuming mid-range is around 400-500 bucks like the fairphone:

    - Memory tagging is still pixel exclusive for now, but it's part of ARMv9 so it should be available on more devices in the future unless they disable it

    - Most devices now have a secure element, though the exact capabilities vary

    - Baseband isolation - no idea really, most chipsets should support IOMMU (or SMMU as ARM calls it) but is not very obvious if that's setup sanely or even used at all on your average device. So I'm guessing most devices are about the same.

    - Security patches certain vendors are much better (like Samsung, for their non-budget devices anyway) but a lot do much the same. It shouldn't generally be worse because of Google's requirements.

    - Verified boot is pretty standard

    • strcat  3 days ago

      Memory tagging isn't Pixel exclusive anymore. Fairphone doesn't lack baseband isolation since it's a standard Snapdragon feature. Fairphone is worse than many OEMs at providing the standard security features and patches. Repeatedly using publicly available signing keys meant for testing for signing their OS is one example which has hopefully been fully addressed for the latest device.

IshKebab  9 days ago

> no memory tagging support

That's not a security feature though... We established that. Fair enough on the other points.

  • strcat  3 days ago

    Memory tagging is an important security feature. The way GrapheneOS uses it is explained at https://news.ycombinator.com/item?id=44678704.

    Only having 16 possible tags doesn't impact the deterministic protections we provide. One of the tag values is reserved for free data, internal metadata, etc. and can also be used as a form of 16 byte guard page. For heap allocation, we also dynamically omit the most recent adjacent non-free tags and the previous non-free tag for the current slot. There are 15 possible random values but 3 are dynamically omitted.

    An attack often needs to use multiple invalid memory accesses where each one would have a 1/15 chance of success from probabilistic MTE alone. MTE gets combined with other probabilistic memory allocator protections. Our main memory allocator also has slot randomization and quarantine randomization.

    A future revision of MTE could be easily be increased to 8 bits and it paves the path to having much larger memory tagging in the future too.

  • Tharre  9 days ago

    For people out of the loop, parent is referring to TikTag[0], a side-channel speculative execution attack breaking MTE in a probabilistic defense scenario, and the weird cope coming from some people that "MTE was only supposed to be a debugging feature anyway".

    However, you need some form of code execution beforehand already for this attack, and more importantly it doesn't affect any of the deterministic guarantees of MTE. And those are the main appeal to GrapheneOS in the first place, preventing things like use-after-free by tagging the memory such that it simply can't be accessed anymore. So it's very much a security feature.

    [0] https://news.ycombinator.com/item?id=40715018