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Ex-NSA Researcher Claims That DLL-Style Attacks Work Just Fine On OS X
An anonymous reader writes Ex-NSA and NASA researcher Patrick Wardle claims to have developed a reliable technique of Shared Library replacement which renders Apple's OSX operating system just as vulnerable to exploitation as Windows has been (via its 'DLL' shared libraries) for years. Speaking at CanSecWest, Wardle explained that Apple's refusal to encrypt software downloads via its App Store allows an attacker on the same network to inject a malicious 'dylib' (shared library) without altering the hash of the legitimate-but-vulnerable software, thereby leaving the Developer ID signature intact. Wardle ran a crafted Python script on a typical Mac and discovered 150 dylib-dependent applications, including Apple's own Xcode developer environment — revealed last week by Edward Snowden to be a priority target for the NSA due to its ability to propagate compromised software.
don't the shared libs need to be signed.
I was under the impression that as of MacOS/X 10.9.x, all distributed shared libraries in your .app directory needed to be signed as well, or Gatekeeper would treat the app as if it was unsigned. (See the "Code Signing Changes in OS X Mavericks" subsection at this link)
Is the vulnerability described in the article applicable only to older versions of MacOS/X, or has the researcher found a way around that test?
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Is the vulnerability described in the article applicable only to older versions of MacOS/X, or has the researcher found a way around that test?
Quoting the article: "It’s not a point-and-click exploit – the attacker will need to get on the same network as the target Mac, either through a breach or by sharing the same public Wi-Fi access point, and then inject a vulnerable but legitimate application and make some purely cosmetic changes to the appearance of the .dmg (virtual installer disk) file when mounted."
Sounds pretty theoretical at this point. I don't see the "reliable technique of Shared Library replacement" that the summary declares.
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It's complicated. On iOS, the libs all need to be signed and encrypted (the executable portions are encrypted, the metadata is not; so you'd need more than just correct hashing). On OSX, they need to be signed if you enable that in your settings (I haven't checked if the executables from iTunes are encrypted). The researcher is not being very clear. Note for example that the article says, "Wardle is also expected to release following his talk source code for a scanner that discovers apps that are vulnerable to his attack." Note that he didn't say he would release his proof of concept. Any of us can write a Python script that searches for .dylibs.
.dylib with one of your own. Secondly, you could append your own code to a .dylib. It's an old technique explained here. You can actually re-sign this and iOS will accept it and run it. Is this what the researcher is doing? He didn't explain.
.dylib loader code before, and it didn't feel tight at all. There is plenty of potential for an exploit, so I could believe he found one, but once again it's tough to believe this guy if he doesn't release his proof of concept.
So, there are several avenues for attack. One, you could replace a
He claims to have gotten around the need for signing. How did he do that? In his demo, will he merely disable the setting that requires signing? It's hard to know if he doesn't release his proof of concept.
I've looked through the mach-o
The fact that the guy is talking more like a PR representative than a researcher makes him suspicious.
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