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Google's Project Zero Team Releases Details On High-Severity macOS Bug 'BuggyCow' (wired.com)
Google's bug-hunting researchers known as Project Zero have revealed a fresh zero-day vulnerability in macOS called "BuggyCow." "The attack takes advantage of an obscure oversight in Apple's protections on its machines' memory to enable so-called privilege escalation, allowing a piece of malware with limited privileges to, in some cases, pierce into deeper, far more trusted parts of a victim's Mac," reports Wired. "The trick's name is based on a loophole the hackers found in the so-called copy-on-write, or CoW, protection built into how MacOS manages a computer's memory." From the report: Some programs, when dealing with large quantities of data, use an efficiency trick that leaves data on a computer's hard drive rather than potentially clog up resources by pulling it into memory. That data, like any data in a computer's memory, can sometimes be used by multiple processes at once. The MacOS memory manager keeps a map of its physical location to help coordinate, but if one of those processes tries to change the data, the memory manager's copy-on-write safeguard requires it to make its own copy. Which is to say, a program can't simply change the data shared by all the other processes -- some of which could be more highly privileged, sensitive programs than the one requesting the change.
Google's BuggyCow trick, however, takes advantage of the fact that when a program mounts a new file system on a hard drive -- basically loading a whole collection of files rather than altering just one -- the memory manager isn't warned. So a hacker can unmount a file system, remount it with new data, and in doing so silently replace the information that some sensitive, highly privileged code is using. Technically, as a zero-day vulnerability with no patch in sight, BuggyCow applies to anyone with an Apple laptop or desktop. But given the technical skill and access needed to pull it off, you shouldn't lose much sleep over it. To even start carrying out this Rube Goldberg -- style attack, a hacker would need a victim to already have some form of malware running on their computer. And while BuggyCow would allow that malware to potentially mess with the inner workings of higher-privileged parts of the computer, it could do so only if it found a highly privileged program that kept its sensitive data on the hard drive rather than memory. Project Zero says it warned Apple about BuggyCow back in November, but Apple hadn't acted to patch it ahead of last week's public reveal.
Google's BuggyCow trick, however, takes advantage of the fact that when a program mounts a new file system on a hard drive -- basically loading a whole collection of files rather than altering just one -- the memory manager isn't warned. So a hacker can unmount a file system, remount it with new data, and in doing so silently replace the information that some sensitive, highly privileged code is using. Technically, as a zero-day vulnerability with no patch in sight, BuggyCow applies to anyone with an Apple laptop or desktop. But given the technical skill and access needed to pull it off, you shouldn't lose much sleep over it. To even start carrying out this Rube Goldberg -- style attack, a hacker would need a victim to already have some form of malware running on their computer. And while BuggyCow would allow that malware to potentially mess with the inner workings of higher-privileged parts of the computer, it could do so only if it found a highly privileged program that kept its sensitive data on the hard drive rather than memory. Project Zero says it warned Apple about BuggyCow back in November, but Apple hadn't acted to patch it ahead of last week's public reveal.
I wonder how much like DirtyCOW this is. I guess it goes to show the meat eaters were right: a cow would kill you if it had the chance.
"The attack takes advantage of an obscure oversight in Apple's protections on its machines' memory to enable so-called privilege escalation, allowing a piece of malware with limited privileges to, in some cases, pierce into deeper, far more trusted parts of a victim's Mac," reports Wired. "The trick's name is based on a loophole the hackers found in the so-called copy-on-write, or CoW, protection built into how MacOS manages a computer's memory."
What's with the dumbed-down language, Wired? "obscure oversight"? "so-called" this and that? Please do tell, this so-called high-severity so-called bug, is it so-called dangerous to the so-called victim?
At least, if one manages to waddle through to the last paragraph, there's this guarded piece of criticism:
"They've had a lot of very-high-profile security-related bugs and some have been really, really stupid," Reed says. "It makes you wonder what's going on with the QA process at Apple. Are they adequately testing? Lately, it seems like they're not."
Apple: copying Microsoft's Win XP security practices takes courage - and now has far better eye candy!
On a single user machine, privilege escalations are not really that damaging. If you manage to hack into my user account on my Mac (or my Windows PC, or many Linux desktops), you have access to all the valuables. There is just nothing of value outside my account.
Totally different on a server. If you have 100 users on a server, then escalation from one hacked user to the other 99 is a fatal problem.
You can unmount/mount a file system without privileges on OSX? I don't think so.
[nt]
Mounting a filesystem anywhere that should actually matter (e.g. /tmp, /var/tmp) typically requires root privileges even in macOS. And any software that might realistically store out-of-bound data in a location where an unprivileged attacker could mount something over top of it (e.g. in the user's home directory) is not likely to be any more privileged than the attacker app.
Is there any actual evidence that this is a real vulnerability, rather than a purely hypothetical one? I mean yes, it's a bug, but in my mind, high severity should be reserved for situations where the bug itself poses a reasonable chance of letting someone destroy or compromise user data, not situations where the author of a critical system daemon does something colossally stupid *and* the bug exists. The high-severity vulnerability would be the critical system daemon storing temporary data in a vulnerable location. This would just be the low-severity springboard that makes that high-severity bug more severe.
Am I missing something?
Check out my sci-fi/humor trilogy at PatriotsBooks.
And the cow goes... ... mooooo!
The perfect name for all apple software
This article is really oddly phrased.
From how I read this, you can basically silently substitute arbitrary code or data pages of programs running in memory. Even ones that might say use security hardware like the T2 chip to make itself less vulnerable even to root based attacks. And from the article, you just have to first execute code on the machine - a feat which with modern browser based and hardware flaw exploits, or even just plain phishing, isn't hard.
And of course, the memory manager/vfs allowing you to swap out in-use disk backed pages is nuts. There seems like there could be a lot of other bugs and exploits there.
If this was a windows flaw it'd be a big deal.
Of course, Apple probably doesn't care, because their long term aim is to get you on a platform where, in theory, you never run software or access information they haven't vetted beforehand anyway.
This attack also requires "a hacker" to mount it. The attack. And the filesystem. At least that's what wired so breathlessly implies.
Apparently BeauHD likes this sort of breathless bullshit also.
Well it IS International Women's Day today.
#Buggycow #IWD
Its quite difficult to understand the bug in start Bordena