Memory Integrity Enforcement

>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 excited to deliver Memory Integrity Enforcement: the industry’s first ever, comprehensive, always-on memory-safety protection covering key attack surfaces — including the kernel and over 70 userland processes — built on the Enhanced Memory Tagging Extension (EMTE) and supported by secure typed allocators and tag confidentiality protections.

Of course it is a little disappointing not to see GrapheneOS's efforts in implementing [1] and raising awareness [2] recognised by others but it is very encouraging to see Apple making a serious effort on this. Hopefully it spurs Google on to do the same in Pixel OS. It should also inspire confidence that GrapheneOS are generally among the leaders in creating a system that defends the device owner against unknown threats.

[1] https://grapheneos.org/releases#2023103000 [2] https://xcancel.com/GrapheneOS/status/1716946325277909087#m

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.

GrapheneOS made our own integration of MTE for hardened_malloc and has done significant work on it. It wasn't simply something we turned on. ARM designed and built the feature which was made available in Cortex cores. Google's Tensor uses standard Cortex cores so unlike Qualcomm they didn't need to make their own implementation. Google integrated it into Android and did some work to make it available on Pixels along with fixing many bugs it uncovered, although definitely not all of them. We had to fix many of the issues. Apple had to make their own hardware implementation because they have their own cores, which Qualcomm finally got done too.

Pixels are not the only Android devices with MTE anymore and haven't been for a while. We've tried it on a Samsung tablet which we would have liked to be able to support if Samsung allowed it and did a better job with updates.

GrapheneOS is not a 1 person project and not a hobby project. I wasn't the one to implement MTE for hardened_malloc and have not done most of the work on it. The work was primarily done by Dmitry Muhomor who is the lead developer of GrapheneOS and does much more development work on the OS than I do. That has been the case for years. GrapheneOS is not my personal project.

We've done a large amount of work on it including getting bugs fixed in Linux, AOSP and many third party apps. Our users are doing very broad testing of Android apps with MTE and reporting issues to developers. There's a specific crash reporting system we integrated for it to help users provide usable information to app developers. The hard part is getting apps to deal with their memory corruption bugs and eventually Google is going to need to push for that by enabling heap MTE by default at a new target API level. Ideally stack allocation MTE would also be used but it has a much higher cost than heap MTE which Apple and Google are unlikely to want to introduce for production use.

Android apps were historically largely written in Java which means they have far fewer memory corruption bugs than desktop software and MTE is far easier to deploy than it otherwise would be. Still, there are a lot of native libraries and certain kinds of apps such as AAA games with far more native code have much bigger issues with MTE.

None of this is wrong but none of this really has any impact on what Apple decided to do. In fact Apple very specifically chose not to go in this direction as they describe in their blog post.

The side channel fixes and new MTE instruction features are not specific to Apple. Apple's blog post has some significant misleading claims and omissions. It's marketing material, not a true technical post without massive bias. It's aimed at putting down the existing deployments of MTE, hyping up what they've done and even downplaying the factually widespread exploits of Apple devices which are proven to be happening. If they're not aware of how widespread the exploits of their devices are including by low level law enforcement with widely available tools, that's quite strange.