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Black Hat Python proxy tool no data

I recently bought the book Black Hat Python, 2nd Edition, by Justin Seitz, which seems to be a very good book about networking and all that (i am writing my code on Kali Linux)
I have a problem on the TCP Proxy Tool on chapter 2 :
Here is the code :
import sys
import socket
import threading
HEX_FILTER = ''.join(
[(len(repr(chr(i))) == 3) and chr(i) or '.' for i in range(256)])
def hexdump(src, length = 16, show = True):
# basically translates hexadecimal characters to readable ones
if isinstance(src, bytes):
src = src.decode()
results = list()
for i in range(0, len(src), length):
word = str(src[i:i+length])
printable = word.translate(HEX_FILTER)
hexa = ' '.join(['{ord(c):02X}' for c in word])
hexwidth = length*3
results.append('{i:04x} {hexa:<{hexwidth}} {printable}')
if show :
for line in results :
print(line)
else :
return results
def receive_from(connection):
buffer = b""
connection.settimeout(10)
try :
while True :
data = connection.recvfrom(4096)
if not data :
break
buffer += data
except Exception as e:
pass
return buffer
def request_handler(buffer):
# perform packet modifications
return buffer
def response_handler(buffer):
# perform packet modifications
return buffer
def proxy_handler(client_socket, remote_host, remote_port, receive_first):
remote_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
remote_socket.connect((remote_host, remote_port))
if receive_first :
# Check for any data to receive before
going into the main loop (i guess)
remote_buffer = receive_from(remote_socket)
hexdump(remote_buffer)
remote_buffer = response_handler(remote_buffer)
if len(remote_buffer):
print("[<==] Sending %d bytes to localhost." % len(remote_buffer))
client_socket.send(remote_buffer)
while True : # Start the loop
local_buffer = receive_from(client_socket)
if len(local_buffer):
line = "[==>] Received %d bytes from localhost." % len(local_buffer)
print(line)
hexdump(local_buffer)
local_buffer = request_handler(local_buffer)
remote_socket.send(local_buffer)
print("[==>] Sent to remote.")
remote_buffer = receive_from(remote_socket)
if len(remote_buffer):
print("[==>] Received %d bytes from remote." % len(remote_buffer))
hexdump(remote_buffer)
remote_buffer=response_handler(remote_buffer)
client_socket.send(remote_buffer)
print("[<==] Sent to localhost.")
if not len(local_buffer) or not len(remote_buffer):
# If no data is passed, close the sockets and breaks the loop
client_socket.close()
remote_socket.close()
print("[*] No more data. Closing connections. See you later !")
break
def server_loop(local_host, local_port, remote_host, remote_port, receive_first):
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
try :
server.bind((local_host, local_port)) # Bind the local host and the local port
except Exception as e:
print('Problem on bind : %r' %e)
# If an error occurs, prints a
print("[!] Failed to listen on %s:%d" % (local_host, local_port))
print("[!] Check for other listening sockets or correct permissions.")
sys.exit(0)
print("[*] Listening on %s:%d" % (local_host, local_port))
server.listen(5)
while True :
client_socket, addr = server.accept()
# print out the local connection information
line = "> Received incoming connection from %s:%d" % (addr[0], addr[1])
print(line)
# start a thread to talk to the remote host
proxy_thread = threading.Thread(
target = proxy_handler,
args=(client_socket,remote_host,
remote_port, receive_first))
proxy_thread.start()
def main():
if len(sys.argv[1:]) != 5:
print("Usage: ./proxy.py [localhost] [localport]")
print("[remotehost] [remoteport] [receive_first]")
print("Example : ./proxy.py 127.0.0.1 9000 192.168.56.1 9000 True")
sys.exit(0)
loca l_host = sys.argv[1]
local_port = int(sys.argv[2])
remote_host = sys.argv[3]
remote_port = int(sys.argv[4])
receive_first = sys.argv[5]
if "True" in receive_first:
receive_first = True
else :
receive_first = False
server_loop(local_host, local_port,
remote_host, remote_port, receive_first)
if __name__ == '__main__':
main()
(sorry, i had a bit of a trouble formatting it and it's quite long)
Now, normally, i just need to open 2 terminals and run the code with the command line :
sudo python proxy.py 127.0.0.1 21 ftp.dlptest.com 21 True
in one terminal, and :
ftp 127.0.0.1 21
in the other one.
My code seems to be working fine, except that... I receive no data. I tried different ftp servers (notice that i don't use the one quoted in the book), but it still doesn't work. It just says :
[*] Listening on 127.0.0.1
> Received incoming connection from 127.0.0.1:55856
but it doesn't actually displays anything until the connexion times out or that i stop the command with Ctrl + C.
I know this question has already been asked, but they don't resolve my problem.
Please tell me if i forgot a line of code (for example the one that prints the data on the screen lol) or did anything wrong :)

one the hexa variable you need to put and f'{ord(c):02x}' because you just have a string and not using the 'c' variable from the list comprehension. That's a small typo you missed fix that and try the whole process again.
hexa = ' '.join([f'{ord(c):02X}' for c in word])
The f should be here ^

File transferring, File can't be opend after transfer

I am currently working on a file transfer server and ran into
a problem. I am able to transfer the file completly and it works perefect,
But when the client that received the file cannot open it through python.
What I mean is that if I transferr a file, I can see it in the dic of the client the received it, but it cannot open it and I get an:IOError that the file doesn't exist.
The server:
def download_manager(self, sock, ADDR, name):
sock.send('Starting file download: '+name)
# Getting the socket that has the file
# Getting the user ip address
BUFSIZ = 1024
fileSock = socket(AF_INET, SOCK_STREAM)
fileSock.connect(ADDR)
print 'connected;'
# Starting the file request protocol.
tries = "2"
# sending number of retries.
fileSock.send(tries + "," + name)
sock.send(tries)
for i in range(int(tries)):
# Accepting the start message.
data, size = fileSock.recv(BUFSIZ).split(',')
sock.send(size)
size = int(size)
if data == 'Start':
fileSock.send('ok')
# Getting first data from the supplier.
data = fileSock.recv(BUFSIZ)
# Sending the data to the request client.
sock.send(data)
current_size = BUFSIZ
while current_size <= size:
# Getting data from the supplier.
data = fileSock.recv(BUFSIZ)
# The server "sleeps" in order to keep a synchronization between the client and the server.
# The client works slower than the server(It needs to save the file as well.
time.sleep(0.0001)
# Sending the data to the request client.
sock.send(data)
current_size += BUFSIZ
print current_size
# Receive for the request client the end message.
#sock.send(data)
data = sock.recv(1024)
if data == 'ok':
fileSock.send(data)
break
else:
fileSock.send(data)
else:
sock.send("wrong")
fileSock.close()
The sender client, Just the relevant part:
print "connection from:", addr
# From here on, the server works by the File-Transfer RFC.
# Accepting number of retries from the server and the name of the file.
data = clientsock.recv(self.BUFSIZ)
tries, name = data.split(',')
# Opening File.
f = file(name, mode='rb')
if not tries:
clientsock.close()
continue
try:
for i in range(int(tries)):
# Sending the file size.
clientsock.send('Start,'+str(self.file_size(name)))
# Accepting an ok.
ok = clientsock.recv(self.BUFSIZ)
if not ok:
continue
if ok == "ok":
# Sending the file.
clientsock.send(f.read(-1))
# Waiting for confirmation.
ok = clientsock.recv(self.BUFSIZ)
if ok == "ok":
break
else:
continue
f.close()
except IOError as e:
f.close()
print e
# An error has occurred, closing the socket.
#clientsock.send('End,None')
clientsock.close()
The recieve Client:
def get_file(self, name):
"""
This function receives and saves the requested file from the server.
:param name: The name of the file( How it is saved )
:return: None.
"""
name = name.split('.')
tries = int(self.sock.recv(self.BUFSIZ))
progress = 0
for i in range(tries):
f = file(name[0] + '.' + name[1], mode='wb')
final_size = int(self.sock.recv(self.BUFSIZ))
data = self.sock.recv(self.BUFSIZ)
f.write(data)
current_size = self.BUFSIZ
while current_size <= final_size:
progress = (float(current_size)/final_size)
if progress > 0.01:
self.app.progress = progress
data = self.sock.recv(self.BUFSIZ)
f.write(data)
current_size += self.BUFSIZ
f.close()
print "Current: " + str(current_size)
print "real: " + str(self.file_size(name[0] + '.' + name[1]))
print "Wanted: " + str(final_size)
self.app.progress = None
if self.file_size(name[0] + '.' + name[1]) == final_size:
print 'ok'
self.sock.send('ok')
break
else:
print 'Bad'
os.remove(name[0] + '.' + name[1])
self.sock.send('Bad')
continue
Any Help is welcomed!

pySerial wait for "#" character to print output from USB serial device

I'm writing a python script that connects to a USB serial device. Whenever a command is sent and executed, the PIC returns with a hashtag. Ie. "Command executed successfully. \n# "
I'd like my python script to wait for the hashtag before outputting the data. How can I do this?
Here's what I have. It doesn't seem to actually print the text received from the PIC. Any help is appreciated
if port.isOpen():
try:
for x in range(0,100):
time.sleep(0.05)
port.write("command 1" + "\r\n")
numLines = 0
// wait for "#" to print output
while True:
response = port.readline()
if "#" in response:
print(response)
numLines = numLines + 1
if(numLines >= 1):
break
time.sleep(0.05)
port.write("command 2" + "\r\n")
numLines = 0
// wait for "#" to print output
while True:
response = port.readline()
if "#" in response:
print(response)
numLines = numLines + 1
if(numLines >= 1):
break
time.sleep(0.05)
port.write("command 3" + "\r\n")
numLines = 0
// wait for "#" to print output
while True:
response = port.readline()
if "#" in response:
print(response)
numLines = numLines + 1
if(numLines >= 1):
break
except Exception, e1:
print("An error occured: " + str(e1))
port.close()

port.readline() will read the serial port till it receives a \n. So, the response will contain the string "Command executed successfully. \n". Since there is no "#" in this string, again the code will encounter the port.readline() statement. This time it will read "#" but since there is no "\n", the code will be stuck there resulting in an infinite loop.
Pyserial provides a method called read():
read(size=1)
Parameters: size – Number of bytes to read. Returns: Bytes read from
the port. Return type: bytes Read size bytes from the serial port. If
a timeout is set it may return less characters as requested. With no
timeout it will block until the requested number of bytes is read.
read() provides a parameter size (with default =1) which specifies the number of bytes to be read. So, you can specify the number of bytes in the string sent by the PIC as a parameter. You can also use the following alternative:
// wait for "#" to print output
while True:
response += port.read()
if "#" in response:
print(response)
numLines = numLines + 1
if(numLines >= 1):
break

If you send some white space to the device, as if it were a terminal command, it will prod it into a response with your "#" in it. I have been successfully using that method. Specifically I send a single space " " plus the terminal line ending (i.e. "\n" or "\r\n" depending on the device).

Sending, receiving with python socket

I'm currently trying to write process that embeds a sequence of n IPs into packets and send it off to n server. Each server remove the outermost IP and then forward it to said IP. This is exactly like tunneling I know. During the process I also want the server to do a traceroute to where it's forwarding the packet and send that back to the previous server.
My code currently will forward the packets but it's stuck on performing the traceroute and getting it. I believe it's currently stuck in the while loop in the intermediate server. I think it's having something to do with me not closing the sockets properly. Any suggestion?
Client
#!/usr/bin/env python
import socket # Import socket module
import sys
import os
s = socket.socket() # Create a socket object
host = socket.gethostname() # Get local machine name
port = 17353 # Reserve a port
FILE = raw_input("Enter filename: \n ")
NIP = raw_input("Enter Number of IPs: ")
accepted_IP = 0
IP= []
while accepted_IP < int(NIP):
IP.append(raw_input("Enter destination IP: \n"))
accepted_IP +=1
#cIP = raw_input("Enter intemediate IP: \n ")
ipv = raw_input("Enter IP version... 4/6")
try:
s.connect((host, port))
print "Connection sucessful!"
except socket.error as err:
print "Connection failed. Error: %s" %err
quit()
raw = open(FILE,"rb")
size = os.stat(FILE).st_size
ls = ""
buf = 0
for i in IP:
while len(i) < 15:
i += "$"
ls += i
header = ipv+NIP+ls+FILE
print ls
s.sendall(header + "\n")
print "Sent header"
data = raw.read(56) +ipv + NIP + ls
print "Begin sending file"
while buf <= size:
s.send(data)
print data
buf += 56
data = raw.read(56) + ipv + NIP + ls
raw.close()
print "Begin receiving traceroute"
with open("trace_log.txt","w") as tracert:
trace = s.recv(1024)
while trace:
treacert.write(trace)
if not trace: break
trace = s.recv(1024)
print "finished forwarding"
s.close()
Intermediate server
#!/usr/bin/env python
import socket
import subprocess
srvsock = socket.socket( socket.AF_INET, socket.SOCK_STREAM )
srvsock.bind( (socket.gethostname(), 17353) )
srvsock.listen( 5 ) # Begin listening with backlog of 5
# Run server
while True:
clisock, (remhost, remport) = srvsock.accept() #Accept connection
print
d = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
header = ""
while True:
b = clisock.recv(1)
if b == "\n":
break
header += b
num = 15 * int(header[1]) + 2
file_name = header[num:]
nheader = header[0]+ str(int(header[1])-1) + header[17:]
d.connect((socket.gethostname(), 12355))
d.sendall(nheader+'\n')
print "begin forwarding"
while True:
raw = clisock.recv(56 + num) # recieve data
ip = raw[-15:] # extract IP
ipv, NIP = raw[57] , str(int(raw[57])-1)
if NIP == "0":
while (raw):
print "stuck in this loop"
d.send(raw[:56])
raw=clisock.recv(56+num)
if not raw: break
else:
while (raw):
print raw[:57] + NIP + raw[59:-15]
print "\n"
d.send(raw[:57] + NIP + raw[59:-15])
raw = clisock.recv(56+num)
if not raw :break
print "Finish forwarding"
d.close()
break
print "Begin traceroute"
tracrt = subprocess.Popen(['traceroute','google.com'], stdout=subprocess.PIPE)
s.sendall(tracrt.communicate()[0])
print "Finished"
clisock.close()
s.close()
Destination server
import socket
s = socket.socket()
host = socket.gethostname()
port = 12355
s.bind((host,port))
s.listen(5)
while True:
csock, (client, cport) = s.accept()
print client
header = ""
while True:
b = csock.recv(1)
if b == "\n":
break
header += b
file_name = header[2:]
r = open("File_test_"+file_name,"wb")
print 'Opening file for writing'
while True:
print "Begin writing file" + " " + file_name
raw = csock.recv(56)
while (raw):
print raw
r.write(raw)
raw = csock.recv(56)
r.flush()
r.close()
print "finish writing"
break
print "closing connection"
csock.close()
s.close()

The intermediate server is stuck in clisock.recv() in this loop because the break condition not raw isn't met before the connection is closed by the client, and the client doesn't close the connection before receiving the traceroute from the intermediate server, so they are waiting on each other.
To remedy this, you might consider sending the file size to the intermediate server, so that it can be used to determine when the receive loop is done. Or, if your platform supports shutting down one half of the connection, you can use
s.shutdown(socket.SHUT_WR)
in the client after sending the file.

Homework - Python Proxy Server

For a programming exercise (from Computer Networking: A Top-Down Approach (6th Edition) by Kurose and Ross), we're trying to develop a simple proxy server in python.
We were given the following code, wherever it says #Fill in start. ... #Fill in end. that is where we need to write code. My specific question and attempts will be below this original snippet.
We need to start the python server with: python proxyserver.py [server_ip] then navigate to localhost:8888/google.com and it should work when we're finished.
from socket import *
import sys
if len(sys.argv) <= 1:
print 'Usage : "python ProxyServer.py server_ip"\n[server_ip : It is the IP Address Of Proxy Server'
sys.exit(2)
# Create a server socket, bind it to a port and start listening
tcpSerSock = socket(AF_INET, SOCK_STREAM)
# Fill in start.
# Fill in end.
while 1:
# Strat receiving data from the client
print 'Ready to serve...'
tcpCliSock, addr = tcpSerSock.accept()
print 'Received a connection from:', addr
message = # Fill in start. # Fill in end. print message
# Extract the filename from the given message print message.split()[1]
filename = message.split()[1].partition("/")[2] print filename
fileExist = "false"
filetouse = "/" + filename
print filetouse
try:
# Check wether the file exist in the cache
f = open(filetouse[1:], "r")
outputdata = f.readlines()
fileExist = "true"
# ProxyServer finds a cache hit and generates a response message
tcpCliSock.send("HTTP/1.0 200 OK\r\n")
tcpCliSock.send("Content-Type:text/html\r\n")
# Fill in start.
# Fill in end.
print 'Read from cache'
# Error handling for file not found in cache
except IOError:
if fileExist == "false":
# Create a socket on the proxyserver
c = # Fill in start. # Fill in end.
hostn = filename.replace("www.","",1)
print hostn
try:
# Connect to the socket to port 80
# Fill in start.
# Fill in end.
# Create a temporary file on this socket and ask port 80 for the file requested by the client
fileobj = c.makefile('r', 0)
fileobj.write("GET "+"http://" + filename + "HTTP/1.0\n\n")
# Read the response into buffer
# Fill in start.
# Fill in end.
# Create a new file in the cache for the requested file.
# Also send the response in the buffer to client socket and the corresponding file in the cache
tmpFile = open("./" + filename,"wb")
# Fill in start.
# Fill in end.
except:
print "Illegal request"
else:
# HTTP response message for file not found
# Fill in start.
# Fill in end.
# Close the client and the server sockets
tcpCliSock.close()
# Fill in start.
# Fill in end.
Where it says:
# Create a socket on the proxyserver
c = # Fill in start. # Fill in end.
I tried:
c = socket(AF_INET, SOCK_STREAM)
This seems to be how you create a socket, then for connecting to port 80 of the host, I have:
c.connect((hostn, 80))
Here, hostn is correctly google.com according to some local print statements I have. The next section for me to fill in says to #Read response into buffer but I don't really understand what that means. I presume it has something to do with the fileobj that is created just above.
Thanks in advance, please let me know if I missed anything I should be adding.
UPDATE
My current code can be found here to see what I've been trying:
https://github.com/ardavis/Computer-Networks/blob/master/Lab%203/ProxyServer.py

This seems to be my potential solution. The pdf from the homework mentions I need to do something at the end, not sure what it is. But the cache and proxy seems to function with this. I hope it helps someone else.
from socket import *
import sys
if len(sys.argv) <= 1:
print 'Usage: "python ProxyServer.py server_ip"\n[server_ip : It is the IP Address of the Proxy Server'
sys.exit(2)
# Create a server socket, bind it to a port and start listening
tcpSerPort = 8888
tcpSerSock = socket(AF_INET, SOCK_STREAM)
# Prepare a server socket
tcpSerSock.bind(('', tcpSerPort))
tcpSerSock.listen(5)
while True:
# Start receiving data from the client
print 'Ready to serve...'
tcpCliSock, addr = tcpSerSock.accept()
print 'Received a connection from: ', addr
message = tcpCliSock.recv(1024)
# Extract the filename from the given message
print message.split()[1]
filename = message.split()[1].partition("/")[2]
fileExist = "false"
filetouse = "/" + filename
try:
# Check whether the file exists in the cache
f = open(filetouse[1:], "r")
outputdata = f.readlines()
fileExist = "true"
print 'File Exists!'
# ProxyServer finds a cache hit and generates a response message
tcpCliSock.send("HTTP/1.0 200 OK\r\n")
tcpCliSock.send("Content-Type:text/html\r\n")
# Send the content of the requested file to the client
for i in range(0, len(outputdata)):
tcpCliSock.send(outputdata[i])
print 'Read from cache'
# Error handling for file not found in cache
except IOError:
print 'File Exist: ', fileExist
if fileExist == "false":
# Create a socket on the proxyserver
print 'Creating socket on proxyserver'
c = socket(AF_INET, SOCK_STREAM)
hostn = filename.replace("www.", "", 1)
print 'Host Name: ', hostn
try:
# Connect to the socket to port 80
c.connect((hostn, 80))
print 'Socket connected to port 80 of the host'
# Create a temporary file on this socket and ask port 80
# for the file requested by the client
fileobj = c.makefile('r', 0)
fileobj.write("GET " + "http://" + filename + " HTTP/1.0\n\n")
# Read the response into buffer
buff = fileobj.readlines()
# Create a new file in the cache for the requested file.
# Also send the response in the buffer to client socket
# and the corresponding file in the cache
tmpFile = open("./" + filename, "wb")
for i in range(0, len(buff)):
tmpFile.write(buff[i])
tcpCliSock.send(buff[i])
except:
print 'Illegal request'
else:
# HTTP response message for file not found
# Do stuff here
print 'File Not Found...Stupid Andy'
a = 2
# Close the socket and the server sockets
tcpCliSock.close()
# Do stuff here