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Asembler.py
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Asembler.py
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import socket, sys
from struct import * #importing required libraries
# Description string with banner and information
desc = "\n" + r"""
""""\t\t\t""""__________ __ ____ __. __
""""\t\t\t""""\______ \____________/ |_ | |/ _| ____ ____ ____ | | __ ___________ ______
""""\t\t\t"""" | ___/ _ \_ __ \ __\ | < / \ / _ \_/ ___\| |/ // __ \_ __ \/ ___/
""""\t\t\t"""" | | ( <_> ) | \/| | | | \| | ( <_> ) \___| <\ ___/| | \/\___ \
""""\t\t\t"""" |____| \____/|__| |__| |____|__ \___| /\____/ \___ >__|_ \\___ >__| /____ >
""""\t\t\t"""" \/ \/ \/ \/ \/ \/
""" "\n\t\t\t\tProvide Source and Destination IP as well as range of ports to scan\n\t\t\t\t\tCheck Flags using -h flag"
# Function for calculating the checksum of packet
def checksum(msg):
# Calculate the 16-bit one's complement of the one's complement sum
# of all 16-bit words in the msg
s = 0
for i in range(0, len(msg), 2):
w = msg[i] + (msg[i + 1] << 8)
s += w
s = (s & 0xffff) + (s >> 16)
# Take the one's complement of the sum
checksum = ~s & 0xffff
checksum += (0x400)
return checksum
# Function for assembling the packet by packing IP/TCP headers
def assemble_packet(sourceip, destip, dest_port, scan):
packet = '';
# source and destination IPs
source_ip = sourceip
dest_ip = destip # or socket.gethostbyname('www.google.com')
# ip header fields
ip_ihl = 5
ip_ver = 4
ip_tos = 0
ip_tot_len = 0 # kernel will fill the correct total length
ip_id = 54321 #Id of this packet
ip_frag_off = 0
ip_ttl = 255
ip_proto = socket.IPPROTO_TCP
ip_check = 0 # kernel will fill the correct checksum
ip_saddr = socket.inet_aton ( source_ip ) #Spoof the source ip address if you want to
ip_daddr = socket.inet_aton ( dest_ip )
ip_ihl_ver = (ip_ver << 4) + ip_ihl
# the ! in the pack format string means network order
ip_header = pack('!BBHHHBBH4s4s' , ip_ihl_ver, ip_tos, ip_tot_len, ip_id, ip_frag_off, ip_ttl, ip_proto, ip_check, ip_saddr, ip_daddr)
# tcp header fields
tcp_source = 4455 # source port
tcp_dest = dest_port # destination port
tcp_seq = 454
tcp_ack_seq = 0
tcp_doff = 5 #4 bit field, size of tcp header, 5 * 4 = 20 bytes
#tcp flags for NULL scan
tcp_fin = 0
tcp_syn = 0
tcp_rst = 0
tcp_psh = 0
tcp_ack = 0
tcp_urg = 0
# tcp flags fot xmas scan
if "xmas" in scan:
tcp_fin = 1
tcp_psh = 1
tcp_urg = 1
# TCP flags for Syn Scan
elif "syn" in scan:
tcp_syn = 1
# TCP flags for fin Scan
elif "fin" in scan:
tcp_fin = 1
# TCP flags for ack Scan
elif "ack" in scan:
tcp_ack = 1
tcp_window = socket.htons (5840) # maximum allowed window size
tcp_check = 0
tcp_urg_ptr = 0
tcp_offset_res = (tcp_doff << 4) + 0
tcp_flags = tcp_fin + (tcp_syn << 1) + (tcp_rst << 2) + (tcp_psh <<3) + (tcp_ack << 4) + (tcp_urg << 5)
# the ! in the pack format string means network order
tcp_header = pack('!HHLLBBHHH' , tcp_source, tcp_dest, tcp_seq, tcp_ack_seq, tcp_offset_res, tcp_flags, tcp_window, tcp_check, tcp_urg_ptr)
#user_data = b'Hello, how are you'
user_data=b'test'
# pseudo header fields
source_address = socket.inet_aton( source_ip )
dest_address = socket.inet_aton(dest_ip)
placeholder = 0
protocol = socket.IPPROTO_TCP
tcp_length = len(tcp_header) + len(user_data)
# packing TCP header
psh = pack('!4s4sBBH' , source_address , dest_address , placeholder , protocol , tcp_length);
psh = psh + tcp_header
# Getting check sum for the packet
tcp_check = checksum(psh)
# make the tcp header again and fill the correct checksum - remember checksum is NOT in network byte order
try:
tcp_header = pack('!HHLLBBH' , tcp_source, tcp_dest, tcp_seq, tcp_ack_seq, tcp_offset_res, tcp_flags, tcp_window) + pack('H' , tcp_check) + pack('!H' , tcp_urg_ptr)
except:
return
# final full packet - syn packets dont have any data
# Getting the full TCP packet and returning to scan for ports
packet = ip_header + tcp_header
return packet