One Byte to rule them all | Hacker News Reader

One Byte to rule them all

googleprojectzero.blogspot.com

206 pointscjbprime31 comments

Seems like the high-level lesson is that tagged unions as traditionally implemented can be vulnerable in a manner that pointer/address-focused mitigations don’t affect?

Indeed, a small integer tag seems much more vulnerable than a C++ virtual table pointer.

On modern hardware, how much is the penalty for using magic numbers instead of small indices? (A magic number meaning a constant like 0x85adb9ad instead of 2). The compiler can't optimize switch(it->type) using a jump table, but I suspect that branch prediction and speculation makes this optimization barely relevant.

A jump table isn't likely used for very small unions anyways. The biggest downside that I see is that comparing with zero is slightly cheaper if that is a common value.

At the very end, there is speculation that things like this might get manual inclusion in these mitigations grounded in parts of Ivan Krstić's Black Hat talk from last year.

Huh, I submitted this two days ago -- why does it say two hours ago?

It's common for mods to game the system and resubmit stories they believe are good.

Not sure why this is downvoted. They do do that.

Likely because "game the system" has a strong negative connotation that seems unwarranted.

Only if you can actually speak to the motivation behind the act.... right?

https://news.ycombinator.com/item?id=11662380

It's the invited post list: https://news.ycombinator.com/invited

Assuming this was reposted 'automatically' you should have received an email from HN at the email associated with your HN account telling you that it was going to happen. At least I have received such emails in the past.

dang talks about the "second chance" queue here: https://news.ycombinator.com/item?id=11662380

Sometimes they see a post that didn't get attention, and so they re-up it. Usually, but not always, you get an email to let you know.

Thanks, that was it! (I didn't get an email.)

I think you always get the email, perhaps it went into your spam folder?

The first time I saw such an email I felt great!! Look for it.

What do I need to learn to understand this 100%?

In somewhat increasing order of specificity (and decreasing additional understanding): computers, C, memory safety, newer cross-platform security mitigations, XNU, iOS-specific security mitigations, iOS exploitation techniques, Project Zero's previous work.

The amount of work put into the exploit, the breadth of low-level knowledge involved, and the number of moving parts required for the successful privilege escalation is impressive, to say the least.

I suspect that getting thought this all took months, considering that iOS runs on platforms not exactly open for experimentation of such a kind.

The LotR section headings were a nice touch

great stuff

So what does it mean?!

iOS has a lot of layers and mitigations both in software and proprietary hardware that aren't found in other systems. Keep in mind that this story would be 20 % the length on other systems, because "physical memory read/write primitive" would be a total break.

thanks for that.

I should note that PPL is not designed to protect against the kinds of attack described in this article; it's really meant to prevent substitution of forged page tables and by coincidence the address chosen by the author ended up being unmappable due to an attempt to protect against virtual memory read/write in the kernel.

iOS is full of holes. How can Apple in good faith say it is "secure by design?" (See https://www.apple.com/business/docs/site/AAW_Platform_Securi... )

Let’s give a experienced group of hackers nearly unlimited budget to find security holes in your competitor’s products.

There’s of course, zero bias in that approach, none whatsoever. /s

If project zero spent even half as much time finding and fixing security exploits in Android as they do just finding exploits in IOS, Google would have a truly competitive product from a security perspective.

FYI, it's not just Project Zero. Zerodium stopped paying for iOS exploits due to oversupply[1][2]

[1]: https://appleinsider.com/articles/20/05/14/software-bug-brok...

[2]: https://twitter.com/Zerodium/status/1260541578747064326

I really don't see the problem with this, finding vulnerabilities is hard work and many times the results are used for nefarious purposes.

You seem to be concerned that Project Zero would be used as marketing material against competitors but I saw no sign of that.

Apple should thank Google for the high quality free labor.

Pretty sure Google follows responsible disclosure - https://en.wikipedia.org/wiki/Responsible_disclosure. Also it actually helps Apple, as Google team discovered it before it being exploited in the wild.

My linked list of these comments will continue to grow until you stop doing this: https://news.ycombinator.com/item?id=23504129

> Project Zero

> News and updates from the Project Zero team at Google

>For the last several years, nearly all iOS kernel exploits ...

Damn, Googlers... Still incapable of explaining things to people. What the hell is Project Zero? Why don't you explain it in your tagline? If not, why not at the beginning of the article?

Edit: this sentence in the "about" section does the job:

> Project Zero is a team of security researchers at Google who study zero-day vulnerabilities in the hardware and software systems that are depended upon by users around the world

I suggest you change the tagline to something like "Studying zero-day vulnerabilities at Google".

Reply on news.ycombinator.com