[SE-2012-01] information regarding recently discovered Java 7 attack

Type securityvulns
Reporter Securityvulns
Modified 2012-08-29T00:00:00


Hello All,

This post is made in reference to recently discovered attack against Java SE 7 platform [1][2]. We discovered that the vulnerabilities used by the attack code are similar to some of the weaknesses that we have found as part of our SE-2012-01 Java SE security research project [3].

The recently reported Java attack relies on a couple of issues, which are briefly described below.

[Vuln 1] The first vulnerability stems from the fact that it is possible to obtain references to restricted classes such as those coming from a sun.* package.

The weakness has its origin in com.sun.beans.finder.ClassFinder class and its findClass method. The bug is caused by insecure usage of reflective forName call of java.lang.Class class.

We reported what seems to be an instance of Vuln 1 to Oracle in Apr 2012 (Issue 11). In our report describing Issue 11 we demonstrated a successful loading of a "sun.awt.SunToolkit" class by the means of a findClass method of ClassFinder class. We however did associate this behavior with a slightly different cause.

[Vuln 2] The second vulnerability relies on the possibility to obtain references to methods of restricted classes. It has its origin in findMethod method of com.sun.beans.finder.MethodFinder class. The bug is caused by insecure usage of reflective getMethod call of java.lang.Class class.

Vuln 2 was reported to Oracle in Apr 2012 (Issue 16).

Insecure ClassFinder and MethodFinder classes were introduced in Java 7. Among other things, this has lead to the modification of java.beans.Statement class implementation. Java 6 implementation of the aforementioned class seems to be more secure as it relies on a ReflectionUtils class introduced at the time of fixing the vulnerabilities reported to Sun Microsystems back in 2005 [4].

[Exploit vector] The exploit vector for the reported code relies on sun.awt.Suntoolkit class and the ability to call its getField method. This method allows to obtain privileged (with override field set to true) references to private fields of arbitrary classes (including restricted ones).

Exploit vector relying on sun.awt.SunToolkit class and its getField method was reported to Oracle in Apr 2012. We demonstrated full JVM sandbox bypass by abusing SunToolkit class implementation, but in a different way than it is done in a circulating code. Again, Java 6 implementation of SunToolkit class seems to be more secure as its getField method is defined to be private (it is public in Java 7).

The reported attack code will not work in Java 6 environment for the reasons described above. Although, Java 7 adoption might not be high yet, with the release of Java SE 7 Update 4, Java SE 7 runtime is the default JRE [5].

On 23 Aug 2012, Oracle provided us with a monthly status report for the security issues reported to the company earlier this year. The company informed us that 19 of the remaining 25 issues were fixed in main codeline and that they are scheduled for a future CPU. This include fixes for some of the issues (11 and 16) that are used by the attack code recently revealed.

We plan to release a short technical paper presenting the results of our Java SE security research after Oracle releases their next Java SE CPU (scheduled for Oct 2012) and most serious issues get fixed.

Thank you.

Best Regards, Adam Gowdiak

Security Explorations http://www.security-explorations.com "We bring security research to the new level"

References: [1] Zero-Day Season is Not Over Yet

http://blog.fireeye.com/research/2012/08/zero-day-season-is-not-over-yet.html#more [2] Let's start the week with a new Java 0-day in Metasploit

https://community.rapid7.com/community/metasploit/blog/2012/08/27/lets-start-the-week-with-a-new-java-0day [3] SE-2012-01 Security vulnerabilities in Java SE http://www.security-explorations.com/en/SE-2012-01.html [4] Sun Alert 200688 http://download.oracle.com/sunalerts/1000543.1.html [5] Moving to Java 7 as default https://blogs.oracle.com/henrik/entry/moving_to_java_7_as