Patch for CVE-2007-2788: Java Image Parsing Code Buffer Overflow

14 Aug 2007, 00:20 PDT

Four months ago, Chris Evans, of Google's Security Team, released an advisory regarding a heap overflow in Sun's Java ICC (image) profile parsing code. (CVE-2007-2788). The release was cordinated with Sun, and an updated Java release (JDK 1.5.0_11-b03) was made available for Window, Solaris, and Linux.

Apple's Java runtime has not yet been updated, so I've gone ahead and written a run-time patch for my own use. If you'd like to use the patch too, you can download the source, or a pre-built binary. You'll need to install Application Enhancer to use the patch. Alternatively, you could simply disable Java in your browser to close the most likely vector.

The issue is due to an integer overflow that occurs when validating that an ICC header tag does not exceed the total length of the heap allocated profile data buffer; The comparison will overflow if the header declares an too-large tag size (See section 7.1 of the ICC.1:2004-10 specification for more information on the header tag format).

For a proof of concept, I've uploaded my regression pages here -- fair warning -- this link will crash an unpatched browser.


Google Group's file hosting was giving Safari users trouble, so I'm now hosting the run-time patch locally.

Installing the iPhone Toolchain using MacPorts

12 Aug 2007, 15:32 PDT

NOTE: This post has been archived for historical purposes. The toolchain has advanced considerably, and Apple is planning to release their own SDK. I plan to hold out on further development, toolchain or otherwise, until it's released.

Please see iPhone Toolchain Project for up-to-date instructions.

To facilitate my own iPhone development, I've committed three new ports for the iphone-binutils project to MacPorts. Once installed, you're ready to compile Hello, World. Prior to installation, you'll need to acquire a copy of the iPhone root disk image ("Heavenly") and install its contents in /opt/local/arm-apple-darwin/heavenly. The image is required to provide the necessary libraries for linking cross-compiled iPhone binaries, and can't be re-distributed.

Extracting and Installing the iPhone Libraries

To start, download and decompress iPhone1,1_1.0_1A543a_Restore.ipsw:

 user@host> curl -O,1_1.0_1A543a_Restore.ipsw
 user@host> unzip iPhone1,1_1.0_1A543a_Restore.ipsw \*.dmg

This will extract two disk images: "694-5259-38.dmg" and "694-5262-39.dmg". The encrypted "694-5262-39.dmg" disk image contains the iPhone root. The decryption key for this image is stored in plain text within the "asr" binary on the corresponding "694-5259-38.dmg". To retrieve the key, run the following:

 user@host> strings 694-5259-38.dmg| grep "^[0-9a-fA-F]*$" | awk '{ if (length($1) == 72) print; }'

This should output a 72 character hex string, which you'll use as the decryption key.

In order to perform the decryption, you'll need modified 'vfdecrypt' -- a command utility for decrypting Mac OS X disk images. The source is available here. To compile, simply type "make" in the vfdecrypt-iphone directory. The provided version of vfdecrypt was slightly modified to support direct input of the private AES and SHA1 HMAC keys -- these are normally wrapped with a user-supplied passphrase (via 3DES-EDE), which is not available. vfdecrypt was written by Ralf-Philipp Weinmann, Jacob Appelbaum, and Christian Fromme.

Once you've build vfdecrypt, use it to decrypt the disk image:

 user@host> ~/vfdecrypt-iphone/vfdecrypt -i 694-5262-39.dmg -k <hex key> -o heavenly.dmg 

Now, mount the disk image and copy the contents to /opt/local/arm-apple-darwin/heavenly:

 user@host> open heavenly.dmg
 user@host> sudo mkdir -p /opt/local/arm-apple-darwin/heavenly
 user@host> (cd /Volumes/Heavenly1A543a.UserBundle && tar cf - .) | (cd /opt/local/arm-apple-darwin/heavenly && sudo tar xvf -)

Installing the Toolchain

To install the toolchain:

 sudo port install arm-apple-darwin-runtime

You should now be able to compile standard Unix software:

 CC=arm-apple-darwin-cc CPP=llvm-cpp ./configure --host=arm-apple-darwin

For more information on compiling your first GUI application, check out the UIKit Hello World