Feeds

Another zombie 'bogus app' bug shambles out of Android

KitKat is safe, older Androids susceptible to .ZIP-derived attack

Website security in corporate America

Jay Freeman, aka @saurik, has detailed another Zip implementation bug in pre-4.4 (Kit Kat) versions of Android which, similarly to the notorious APK vulnerability exposed earlier this year, opens a hole that malware can sneak through.

Freeman – whose previous credentials include security analysis of Google Glass and uncovering the dodginess of the “iMessage for Android” app – has written in a blog post that he uncovered the extra vulnerability in June, but waited until Android 4.4 (with a fix) was shipping.

Freeman's dense post is here, and is unpicked and explained by Sophos' Paul Ducklin at Naked Security here.

In brief, the extra APK vulnerability offered a path for an attacker to exploit the way Android used Zip file headers to verify the software. As Ducklin explains, Zip still carries an obsolete of its history around with it: lots of filename redundancy in case files had to be split across multiple floppy (remember those?) disks. To help a program navigate a file, the header includes a field for filename length – this lets an extractor navigate to where the file data is, by skipping the header.

As Ducklin writes, the problem is this: “The Java code in Android 4.3 and earlier, that extracts the file data to verify it, uses the filename length from the central directory. But the C code that extracts the file to install and execute it uses the filename length in the local header.”

An attacker could then take a verified app, add their malware, and modify the header length the C-code loader uses to point not to the legitimate app, but to the malware. Ducklin's illustration shows this simply:

Paul Ducklin's illustration of the APK vulnerability

Image: Paul Ducklin, Naked Security

As Saurik writes: “The central directory includes a file offset for each local header, so that once the Java code has finished verifying a file, it can jump directly to the next one, thus avoiding the local header data that would cause it to skip forward incorrectly. The imposter data, squeezed between the legitimate file and the next local header, is simply ignored.”

The fix in Kit Kat is to force Java to look at the same data as the C-loader so that a discrepancy is identified. ®

Protecting users from Firesheep and other Sidejacking attacks with SSL

More from The Register

next story
Early result from Scots indyref vote? NAW, Jimmy - it's a SCAM
Anyone claiming to know before tomorrow is telling porkies
Home Depot: 56 million bank cards pwned by malware in our tills
That's about 50 per cent bigger than the Target tills mega-hack
Hackers pop Brazil newspaper to root home routers
Step One: try default passwords. Step Two: Repeat Step One until success
UK.gov lobs another fistful of change at SME infosec nightmares
Senior Lib Dem in 'trying to be relevant' shocker. It's only taxpayers' money, after all
Critical Adobe Reader and Acrobat patches FINALLY make it out
Eight vulns healed, including XSS and DoS paths
Spies would need SUPER POWERS to tap undersea cables
Why mess with armoured 10kV cables when land-based, and legal, snoop tools are easier?
TOR users become FBI's No.1 hacking target after legal power grab
Be afeared, me hearties, these scoundrels be spying our signals
Blood-crazed Microsoft axes Trustworthy Computing Group
Security be not a dirty word, me Satya. But crevice, bigod...
prev story

Whitepapers

Secure remote control for conventional and virtual desktops
Balancing user privacy and privileged access, in accordance with compliance frameworks and legislation. Evaluating any potential remote control choice.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
Storage capacity and performance optimization at Mizuno USA
Mizuno USA turn to Tegile storage technology to solve both their SAN and backup issues.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
The next step in data security
With recent increased privacy concerns and computers becoming more powerful, the chance of hackers being able to crack smaller-sized RSA keys increases.