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KeyStore Vulnerability Affects 86% of Android Devices
jones_supa (887896) writes "IBM security researchers have published an advisory about an Android vulnerability that may allow attackers to obtain highly sensitive credentials, such as cryptographic keys for some banking services and virtual private networks, and PINs or patterns used to unlock vulnerable devices. It is estimated that the flaw affects 86 percent of Android devices. Android KeyStore has a little bug where the encode_key() routine that is called by encode_key_for_uid() can overflow the filename text buffer, because bounds checking is absent. The advisory says that Google has patched only version 4.4 of Android. There are several technical hurdles an attacker must overcome to successfully perform a stack overflow on Android, as these systems are fortified with modern NX and ASLR protections. The vulnerability is still considered to be serious, as it resides in one of the most sensitive resources of the operating system."
Something new that's compatible with most people's version of Android.
No bounds checking? In a security module of Android? Duh! What sort of idiots do they have coding this thing?
And good luck updating all the Android devices.
Especially sense most of them are abandoned shortly after release and can NEVER be upgraded.
I wrote it. Thanks for the feedback.
the once flagship N1 that I own (and still use since it still mostly works) has been abandoned long ago and I hate google for it.
this is yet another reason not to trust them. I don't care about new features, but porting security fixes should be a must-do for them, given how HUGE that company is. they have endless pockets and can easily afford to keep just a few guys (at least) busy keeping the old google flagship models updated.
they don't. and they suck for it.
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"It is now safe to switch off your computer."
I can understand if Google wants to force vendors to update to the most recent android. However, from a vendor perspective, what's so hard about backporting this patch to, say, android 4.3 and below? Is there a contract with Google forbidding this? Do they get money from NSA?
no, by google, the code OWNER, for much of the code base.
old 2.x android which still works for audio phone and email and simple web (which is 99% of what many users want, actually). but has no security patches from google since the last OTA update was at least 3 yrs ago, maybe more.
google abandons things. it may not be pleasant for fanboys to admit, but its a fact and its part of why I have so much anger toward google. they are not serious. not by my definition. 5 yr old hardware that needs security SHOULD get security updates. even 10 yrs. again, this is the money and power and brain-rich google we're talking about. they do NOT get a pass on being bad about backporting security. a 10 or 100 man company, sure. but google gets no free pass on abandoning their own phones (my case, the N1). total complete abandonment. even the gmail app BY google refuses to work properly on the N1, now. it does not auto poll and show newmail indications. you have to manually poll. a google app on a google phone that is broken. this is why I hate them.
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"It is now safe to switch off your computer."
One difference between enterprise software companies and consumer software is that over 50% of the enterprise revenue is for support. Virtually none for consumer software because people are unwilling to pay for it and the product lifetime is short.
Intron: the portion of DNA which expresses nothing useful.
A rookie mistake. Tools to trap this have been around for ages. And do not give the "but they were optimizing" excuse. The only thing a security module should be optimized for is security. Once again, a rookie mistake.
putting the 'B' in LGBTQ+
That was a new $700+ iPad, from the Apple Store in the summer of 2010 about five months after launch.
So it was abandoned by Apple 28 months after launch. The hardware is still functional. It even still holds its charge. But there's no security updates whatsoever.
I don't think old devices are vulnerable, and while 4.3 devices are vulnerable, most of them have an additional countermeasure in place that should protect against any actual disclosure of private keys.
In older devices, it looks like prior to changing keystore to use the Binder API the bounds checking was done at a higher level in the call stack, so the code isn't actually vulnerable. When keystore's API was changed to be Binder-based, that checking was lost, enabling the bug. Looking at the git log, the Binder keystore API was merged in November 2012 which I believe means that only 4.3 devices are vulnerable. It appears the bug was identified and fixed before 4.4 was released.
But most 4.3 devices, at least from major vendors, have hardware-backed key storage. All Nexus devices do. They're vulnerable to the bug, but the private keys are completely inaccessible to the Android userspace and kernel, so there's no way the key material can be leaked. To see if your device has hardware-backed key storage go to Settings -> Security and scroll down to "Credential Storage". If it says "Storage type Hardware-backed", then keystore private keys are not accessible to the Android OS userspace or kernel, so there's no way they could leak.
One caveat: Until 4.4 (I think), only RSA keys could be managed by secure hardware. So DSA and ECDSA private keys in 4.3 device keystores could leak via this vulnerability. In the future we should have support for all sorts of keys in secure hardware (https://android-review.googlesource.com/#/c/97651/ -- yes, I'm the author of that CL), as well as a mechanism for checking the hardware vs software storage question on individual keys.
I'm not trying to say this wasn't a pretty serious error on Google's part. Even with the bounds check higher in the call stack, it should have been done in keystore as well. Security-sensitive code like this should take a belt-and-suspenders approach, not depending on validation done at other layers, specifically because stuff at other layers changes. Actually, I know the guy who wrote it and that is the way he thinks, too, so I'm somewhat surprised he wrote this bug.
(Note: I recently joined the Android security team, and it looks like I may be the maintainer of keystore. I am taking the lead on hardware-backed key storage. However, I should mention that I'm not speaking in an official capacity, just someone who knows the code a bit and took a few minutes to look through the git logs.)
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