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Sun JDK Image Parsing Library Vulnerabilities (More ICC Parsing)
------------------------------------------------------------------------
SUMMARY
A vulnerability in Sun JDK image parsing library allows attackers that can
supply the JDK with a malformed JPEG file to trigger a buffer overflow
which in turn can be used at the very least to crash the Java environment,
but in more problematic cases to execute arbitrary code.
DETAILS
Vulnerable Systems:
* JDK version 1.6.0u
Immune Systems:
* JDK 1.6.0u5
JDK comes with an image parsing API based around the javax.imagio.ImageIO
class. A slightly sloppy demo program to exercise this API would be:
import javax.imageio.ImageIO;
import javax.imageio.ImageReader;
import java.util.Iterator;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.ByteArrayInputStream;
import javax.imageio.stream.MemoryCacheImageInputStream;
import javax.imageio.stream.ImageInputStream;
public class ImgReader {
public static void main(String[] args) throws Exception {
InputStream is = new FileInputStream(args[0]);
ImageInputStream iis = new MemoryCacheImageInputStream(is);
Iterator it = ImageIO.getImageReaders(iis);
ImageReader reader = it.next();
reader.setInput(iis);
int width = reader.getWidth(0);
}
}
This program takes the first command line argument as an image filename to
put through the JDK image parsing API.
Of course, most Java image parsing will be safe from the usual gamut of
buffer overflows, integer overflows, subtle memory corruptions, etc. Most,
but not all. The JPEG and BMP parsers support embedded ICC profiles (to do
with colour correction), and the ICC profile parser is actually backed by
native code.
Flaw 1 - DoS due to heap buffer out-of-bounds write with para-type curves
Demo JPG: <http://scary.beasts.org/misc/jdk/evilicc.jpg>
http://scary.beasts.org/misc/jdk/evilicc.jpg. It causes a crash of the
JVM. The crash is caused by writing out-of-bounds to a heap buffer. It is
not immediately clear how controllable the data written past the heap is,
so this may be just a DoS. However, a DoS still represents a serious
problem in a server-side context.
The code flaw would seem quite unfortunate: 4096 bytes are allocated in a
buffer, which is then treated as being capable of fitting 4096 uint16
values. It seems that any ICC profile containing a parametric-type curve
should crash out the JVM.
There seem to be a few genuine reports of what could be this issue in the
wild:
<http://www.google.com/search?hl=en&q=sun.awt.color.CMM.cmmCombineTransforms&btnG=Google+Search>
http://www.google.com/search?hl=en&q=sun.awt.color.CMM.cmmCombineTransforms&btnG=Google+Search
Flaw 2 - heap-based buffer overflow parsing curv-type curves
Demo JPG: <http://scary.beasts.org/misc/jdk/evilicc2.jpg>
http://scary.beasts.org/misc/jdk/evilicc2.jpg. This, on my machine, causes
a crash due to an out-of-bounds heap write. The code flaw is an integer
overflow in SpCurveToPublic:
Limit = SpGetUInt32 (Buf);
..
UInt16Ptr = (KpUInt16_t *)SpMalloc (Limit * (KpInt32_t)sizeof
(*UInt16Ptr));
..
for (Index = 0; Index < Limit; Index++)
*UInt16Ptr++ = SpGetUInt16 (Buf);
..
ADDITIONAL INFORMATION
The information has been provided by <mailto:scarybeasts@gmail.com> Chris
Evans.
The original article can be found at:
<http://scary.beasts.org/security/CESA-2007-005.html>
http://scary.beasts.org/security/CESA-2007-005.html
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