11:09 Mon, 29 Jan 2007 PST -0800

Month of Apple Bugs - Patch 27

Today's patch includes fixes for three different issues:

Thanks to my friends William Carrel and Rosyna of Unsanity for their work on tracking down the bugs and assistance in implementing the patches.

You can download the source, or a pre-built binary. As always, you'll need Application Enhancer to use the patches.

Update 9:00 1/29/06: Modified the patch (to 27-1) to match the latest 10.4.8 version of the PowerPC Software Update.app, 2.0.5 (Intel is 2.0.4).

This release also removes a few patches:

Flip4Mac WMV Vulnerability

The ever-handy Flip4Mac WMV QuickTime components are susceptable to a buffer overflow due to an integer overflow when comparing two buffer lengths as signed values. The comparison results in a stack-based buffer overflow that is potentially remotely exploitable by a malicious WMV movie. Both Mail.app and Safari will inline WMV movies (I accidentally crashed Mail.app when I tried to attach a proof-of-concept to an e-mail I'd drafted).

This patch is more complex; nearly all symbols are stripped in Flip4Mac, so finding the vulnerable code requires locating a public symbol and then computing the offset to the vulnerable code, for both PowerPC and Intel. Due to the relatively short length of the function in question, I decided to completely re-implement it, using proper unsigned comparisons. You can peruse the implementation in Google Code's web interface.

Software Update Catalog Filename Format String Vulnerability

Software Update falls prey to a common format string vulnerability, passing the user-supplied file name to an alert panel. However, I'm not aware of any means of delivering a maliciously named file without requiring direct user interaction. The error dialog in question is only displayed when a file without the "sucatalog" extension is passed to Software Update (eg, "swutmp") -- the patch checks file extension, and escaps any '%' characters if the extension is not "sucatalog".

Installer Package Filename Format String Vulnerability

Installer is also susceptable to the same issue -- when an error is encountered while opening a file, Installer will pass the user-supplied file name to an alert panel. A zipped installer package will be automatically opened by Safari if "Open Safe Files" is enabled. The patch works by "context patching" NSRunAlertPanel() while within -[InstallerController openFile:withOptions:]. The guarded NSRunAlertPanel() passes it's msg argument as a vararg argument to the "%@" format string, and the patch is removed when -[InstallerController openFile:withOptions:] exits. A reference count is used to handle recursion.

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