51–60 of 259 posts
1988 called and wants it memory tagging back https://www.devever.net/~hl/ppcas ! But yeah this was support for a the longest time by IBM basically. It's nice to see it's getting more widespread.
The first RS-64 with the PowerPC AS extensions came out in 1995.
> Google took a great first step last year when they offered MTE to those who opt in to their program for at-risk users. But even for users who turn it on, the effectiveness of MTE on Android is limited by the lack of deep integration with the operating system that distinguishes Memory Integrity Enforcement and its use of EMTE on Apple silicon. > With the introduction of the iPhone 17 lineup and iPhone Air, we’re exc…
Apple has been working on this for years. It's not like they started thinking about memory tagging when Daniel decided to turn it on in GrapheneOS.
As an outsider I am quite ignorant to what security developments these companies are considering and when the trade-offs are perhaps too compromising for them to make it to production. So I can't appreciate the scale of what Apple had to do to reach this stage, whereas with GrapheneOS I know they favour privacy/security on balance. I use that as a weak signal to gauge how committed Apple/Google/Microsoft are to realising those kinds of goals too.
Both approaches revealed the same conclusion: Memory Integrity Enforcement vastly reduces the exploitation strategies available to attackers. Though memory corruption bugs are usually interchangeable, MIE cut off so many exploit steps at a fundamental level that it was not possible to restore the chains by swapping in new bugs. Even with substantial effort, we could not rebuild any of these chains to work around MIE.…
In terms of Apple Kremlinology, should this be seen a step towards full capability-based memory safety like CHERI ( https://en.wikipedia.org/wiki/Capability_Hardware_Enhanced_R... ) or more as Apple signaling that it thinks it can get by without something like CHERI?
This is really impressive. It’s my understanding that this won’t protect you in the case where the attacker has a chance to try multiple times. The approach would be something like: go out of bounds far enough to skip the directly adjacent object, or do a use after free with a lot of grooming, so that you get a a chance of getting a matching tag. The probability of getting a matching tag is 1/16. But this post doesn’…
The other 15/16 attempts would crash though, and a bug that unstable is not practically usable in production, both because it would be obvious to the user / send diagnostics upstream and because when you stack a few of those 15/16s together it's actually going to take quite a while to get lucky.
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How does this compare to CHERI?
Substantially less complex and therefore likely to be substantially easier to actually use. CHERI-Morello uses 129-bit capability objects to tag operations, has a parallel capability stack, capability pointers, and requires microarchitectural support for a tag storage memory. Basically with CHERI-Morello, your memory operations also need to provide a pointer to a capability object stored in the capability store. Ever…
This is the opposite of fun computing. This is commercial computing who's only use case it making sure that people can send/receive money through their computers securely. I love being able to peek/poke inside and look at my processes ram, or patch the memory of an executable. All this sounds pretty impossible on Apple's locked down systems. They're not so much general purpose computers anymore as they are locked dow…
Both approaches revealed the same conclusion: Memory Integrity Enforcement vastly reduces the exploitation strategies available to attackers. Though memory corruption bugs are usually interchangeable, MIE cut off so many exploit steps at a fundamental level that it was not possible to restore the chains by swapping in new bugs. Even with substantial effort, we could not rebuild any of these chains to work around MIE.…
In terms of Apple Kremlinology, should this be seen a step towards full capability-based memory safety like CHERI ( https://en.wikipedia.org/wiki/Capability_Hardware_Enhanced_R... ) or more as Apple signaling that it thinks it can get by without something like CHERI?
They also imply a very different system architecture.