encrypt_aes.py

#!/usr/bin/python3

# Author: Shubham Singh
# Student ID: SLAE - 1342
from Crypto.Cipher import AES
from Crypto import Random
import base64,sys,binascii,os,getopt
# Argument List
argumentList = sys.argv[1:] 
# Options 
options = "hed:"
  
# Long options 
long_options = ["help","encrypt", "decrypt"] 

# 16 Character long.Don't share it  
secret = 'slaespiritedwolf' 
BLOCK_SIZE = 16

# PADING
def pad(s):
	return s + (BLOCK_SIZE - len(s) % BLOCK_SIZE) * chr(BLOCK_SIZE - len(s) % BLOCK_SIZE)

# UNPADING -> It will be usefull while decrypting
def unpad(s):
	return s[:-ord(s[len(s) - 1:])]

# Encode the cipher with correct pading and encode it into base64.
def encode_aes(cipher,s):
	return base64.b64encode(cipher.encrypt(pad(s)))

# Encryption function which will encrypt our shellcode with AES , MODE: CBC
def enc(shellcode):
	inp = shellcode.replace("\\x","")
	shellcode = inp.decode("hex")
	iv = Random.new().read(AES.block_size)
	cipher = AES.new(secret,AES.MODE_CBC, iv)
	encoded = base64.b64encode(iv + cipher.encrypt(pad(shellcode)))
	print("Encoded String:"+ encoded)
	return 1
# Decryption function which will decrypt our AES encrypted data
def dec(encrypted_string):
#	print('stage 1:',encrypted_string)
	encrypt = base64.b64decode(encrypted_string)
#	print('stage 2:',encrypt)
	iv = encrypt[:16]
#	print('IV:', iv)
	cipher = AES.new(secret, AES.MODE_CBC, iv)
	cipher_1 = cipher.decrypt(encrypt)
#	print('FINAL 1:',cipher_1)
	cipher_2 = unpad(cipher_1)
#	print('FINAL 2:', cipher_2)
	convert_string_to_byte = bytes(cipher_2)
	hex_string = binascii.b2a_hex(convert_string_to_byte)
	# Decrypted shellcode
	lol = hex_string[32:]
	shell = lol
	# Add \x after every 2 character
	shell_for_copy = "\\x"
	shell_for_copy += '\\x'.join(a+b for a,b in zip(shell[::2], shell[1::2]))
	print(shell_for_copy)
	# Write the shellcode in our shellcode.c file
	write_to_file = open("shellcode.c", "w")
	write_to_file.write("""
#include<stdio.h>
#include<string.h>

unsigned char shellcode[]= \\
\"""")
	write_to_file.close()
	write_to_file = open("shellcode.c", "a")
	write_to_file.write(shell_for_copy)
	write_to_file.close()
	write_to_file = open("shellcode.c", "a")
	write_to_file.write('''\";

main()
{
	printf(\"Shellcode length: %d\\n\", strlen(shellcode));
  	int (*ret)()=(int (*)())shellcode;
        ret();
}
''')
	write_to_file.close()

	# Compile the shellcode.c file with GCC compiler and execute the shellcode after compiling.
	os.system("gcc -fno-stack-protector -z execstack shellcode.c -o shellcode && ./shellcode")
	
	return 1

try: 
    	# Parsing argument 
	arguments, values = getopt.getopt(argumentList, options, long_options) 
      
    	# Checking each argument 
	for currentArgument, currentValue in arguments: 
  
		if currentArgument in ("-h", "--help"):
			print ("Diplaying Help\n-h	--help		Show this Help Menu\n-e	--encrypt	Encrypt the shellcode using: python3 encrypt_aes.py -e <shellcode>\n-d	--decrypt	Decrypt the AES encrypted data using: python3 encrypt_aes.py -d <AES>")
		elif currentArgument in ("-e", "--encrypt"):
			shellcode = sys.argv[2]
			encrypted_arg = enc(shellcode)

		elif currentArgument in ("-d", "--decrypt"):
			decode_string = sys.argv[2]
			print(decode_string)
			print(type(decode_string))
			decrypted_arg = dec(decode_string)

except getopt.error as err: 
    	# output error, and return with an error code 
	print (str(err))