SOCKS5 and UDP error

[duncanwebb]

I'm trying to write a small test application to test if a Proxy supports UDP over SOCKS5.

Currently the application seems to be sending messages correctly but receiving is falling over when receiving the echoed data. File "E:\pacs\socks.py", line 330, in recvfrom peerhost, peerport = self.proxy_peername TypeError: 'NoneType' object is not iterable

I cannot see how self.proxy_peername is being initialized with socks5 proxy. My test environment is using proxy plus (free edition) with SOCKS activated and the following code

#! /usr/bin/env python

# Client and server for udp (datagram) echo.
#
# Usage: udpecho -s [port]            (to start a server)
# or:    udpecho -c host [port] <file (client)

import sys
import socks
from socket import *

ECHO_PORT = 50000 + 7
BUFSIZE = 1024

def main():
    if len(sys.argv) < 2:
        usage()
    if sys.argv[1] == '-s':
        server()
    elif sys.argv[1] == '-c':
        client()
    elif sys.argv[1] == '-ss':
        sockserver()
    elif sys.argv[1] == '-sc':
        sockclient()
    else:
        usage()

def usage():
    sys.stdout = sys.stderr
    print 'Usage: udpecho -s [port]            (server)'
    print 'or:    udpecho -c host [port] <file (client)'
    sys.exit(2)

def server():
    if len(sys.argv) > 2:
        port = eval(sys.argv[2])
    else:
        port = ECHO_PORT
    s = socket(AF_INET, SOCK_DGRAM)
    s.bind(('', port))
    print 'udp echo server ready'
    while 1:
        data, addr = s.recvfrom(BUFSIZE)
        print 'server received', `data`, 'from', `addr`
        s.sendto(data, addr)

def client():
    if len(sys.argv) < 3:
        usage()
    host = sys.argv[2]
    if len(sys.argv) > 3:
        port = eval(sys.argv[3])
    else:
        port = ECHO_PORT
    addr = host, port
    s = socket(AF_INET, SOCK_DGRAM)
    s.settimeout(100)
    s.bind(('', 0))
    print 'udp echo client ready, reading stdin'
    while 1:
        line = sys.stdin.readline()
        if not line:
            break
        s.sendto(line, addr)
        data, fromaddr = s.recvfrom(BUFSIZE)
        print 'client received', `data`, 'from', `fromaddr`

def sockserver():
    if len(sys.argv) > 2:
        port = eval(sys.argv[2])
    else:
        port = ECHO_PORT
    socks.setdefaultproxy(socks.PROXY_TYPE_SOCKS5, "127.0.0.1", 1080)
    s = socks.socksocket(AF_INET, SOCK_DGRAM)
    s.bind(('', port))
    print 'udp echo server ready'
    while 1:
        data, addr = s.recvfrom(BUFSIZE)
        print 'server received', `data`, 'from', `addr`
        s.sendto(data, addr)

def sockclient():
    if len(sys.argv) < 3:
        usage()
    host = sys.argv[2]
    if len(sys.argv) > 3:
        port = eval(sys.argv[3])
    else:
        port = ECHO_PORT
    addr = host, port
    s = socks.socksocket(AF_INET, SOCK_DGRAM)
    s.set_proxy(socks.SOCKS5, "localhost")
    s.settimeout(100)
    s.bind(('', 0))

    print 'udp echo client ready, reading stdin'
    try:
        while 1:
            line = sys.stdin.readline()
            if not line:
                break
            print 'sending', line, 'to', addr
            s.sendto(line, addr)
            res = s.recvfrom(BUFSIZE)
            print '%r' % res
            print 'client received', `data`, 'from', `fromaddr`
    except KeyboardInterrupt:
        print 'Bye'
        pass

main()

In one command window I run: udpecho.py -s

In the another window: udpecho.py -sc localhost test

The send is working as the server sees udp echo server ready server received 'test\n' from ('127.0.0.1', 49165)

But the receive is failing.

[duncanwebb]

Sorry I don't know the markup of github.

[vadmium]

Stick a line of three back-ticks before and after the code to escape the markup.

It looks like the code I used when I introduced the UDP support calls sock.connect() before calling send() or recvfrom(). That may be a quick workaround for you, but I will try and make a proper fix that receives packets when the socket is not “connected”.

[duncanwebb]

Thanks for the fix, this works (I'd already commented out this block of code).

I wasn't able to find any code examples of using the pysocks with UDP. It looks like bind calls connect() but it may be exiting before with no authentication.

[vadmium]

FYI I added the UDP support fairly recently. Here is a generic script that I originally used it for: https://gist.github.com/vadmium/675e87a148cba14b9e78. It depends on a couple of my personal library routines, but you should be able see the general idea.

Calling bind() on the high-level UDP Py Socks object does invoke a low-level connect() to set the address of the UDP relay. However I thought it best for the high-level connect() to work differently: it sets the remote address and port that the UDP relay forwards packets to, as well as filters packets received according to the remote address that the relay indicates.

[duncanwebb]

Thanks again for the explanation. Using bind works a treat, I can use proxy+ running on one machine and the server and the client on another and packet tracing the conversation there is a nice trace: socksclient -> proxy (socks) proxy -> server (udp) server -> proxy (udp) this is an echo server proxy -> socksclient (socks)

So changing the code to use connect reveals a small python 2 problem

def sockclient():
    if len(sys.argv) < 3:
        usage()
    host = sys.argv[2]
    if len(sys.argv) > 3:
        port = eval(sys.argv[3])
    else:
        port = ECHO_PORT
    addr = host, port
    s = socks.socksocket(AF_INET, SOCK_DGRAM)
    s.set_proxy(socks.SOCKS5, PROXY_HOST)
    s.connect(addr)
    #s.bind(('', 0))
    s.settimeout(100)

    print 'udp echo client ready, reading stdin'
    try:
        while 1:
            line = sys.stdin.readline()
            if not line:
                break
            print 'sending', line, 'to', addr
            s.sendto(line, addr)
            res = s.recvfrom(BUFSIZE)
            #print '%r' % (res,)
            data, fromaddr = res
            print 'client received', `data`, 'from', `fromaddr`
    except KeyboardInterrupt:
        print 'Bye'

Traceback (most recent call last): File "E:\pacs\udpecho.py", line 116, in main() File "E:\pacs\udpecho.py", line 27, in main sockclient() File "E:\pacs\udpecho.py", line 108, in sockclient res = s.recvfrom(BUFSIZE) File "E:\pacs\socks.py", line 333, in recvfrom filterhost = socket.inet_pton(self.family, peerhost).strip(b"\x00") AttributeError: 'module' object has no attribute 'inet_pton'

[vadmium]

Ah crap. I suspect you are using Windows, where inet_pton() is not available. I was trying to check if the host is a null address like 0.0.0.0, but without being IPv4 specific. Maybe it’s simplest to just use the equivalent IPv4 function instead, since IPv6 isn’t supported anyway. Will update PR #15 when I get a chance.

[duncanwebb]

Indeed I'm using Windows, E:\ gives you your confirmation.

Thanks for the package, it has helped me prove that I proxy is not working.