Re: ANN: PyDTLS

Discussion in 'Python' started by rbit, Jan 9, 2013.

  1. rbit

    rbit Guest

    Thank you. I will gladly port to Python 3 if there is interest from
    the community.

    Regarding PEP 3156: asynchronous use of unreliable network protocols
    makes for an interesting use case. In particular, it forces
    applications to deal with packet loss under some circumstances. One
    such situation occurs during DTLS's handshaking phase: if no response
    is received from the peer after some period of time, we must assume
    that our most recent datagram has been lost, and so we need to
    retransmit. The event loop interface as outlined in the PEP makes this
    a bit difficult (as did the asyncore module). One possible way to make
    things easier would be by adding two parameters to add_reader: a
    callable to retrieve the current timeout, and a callable that is
    invoked if that timeout expires before the descriptor becomes
    readable. Each loop iteration would then collect all given timeouts,
    and pass the minimum of that set to whatever polling facility it
    invokes. If that timeout expires, the corresponding timeout handler
    would be invoked prior to the next loop iteration.

    The PEP also considers only stream transports when referring to
    "transport." Datagram transports do not, for example, have the
    property that calling t.write(b'abc'); t.write(b'def') is equivalent
    to calling t.write(b'abcdef'). I'm not sure what sort of impact this
    omission of datagram transports has for an implementation. Though I
    would certainly like to see datagram transports be treated as
    first-class citizens, despite not being nearly used as often as stream
    transports. I would hope that an implementer of, say, RTP over UDP,
    can tie into the same event loop as someone implementing a
    single-process, single-threaded Web server.

    Implementing DTLS as a tulip transport sounds interesting. Is the
    tulip package available somewhere so that I can try it out?

    Ray

    On Tue, Jan 8, 2013 at 6:53 AM, Guido van Rossum <> wrote:
    > This sounds exciting. Are you considering a Python 3 port? It might make a
    > nice demo of PEP 3156.
    >
    >
    > On Monday, January 7, 2013, rbit wrote:
    >>
    >> I would like to announce Datagram Transport Layer Security for
    >> Python. From the top of the project README:
    >>
    >> PyDTLS brings Datagram Transport Layer Security (DTLS - RFC 6347:
    >> http://tools.ietf.org/html/rfc6347) to the Python environment. In a
    >> nutshell, DTLS brings security (encryption, server authentication,
    >> user authentication, and message authentication) to UDP datagram
    >> payloads in a manner equivalent to what SSL/TLS does for TCP stream
    >> content.
    >>
    >> DTLS is now very easy to use in Python. If you're familiar with the
    >> ssl module in Python's standard library, you already know how. All it
    >> takes is passing a datagram/UDP socket to the *wrap_socket* function
    >> instead of a stream/TCP socket. Here's how one sets up the client side
    >> of a connection:
    >>
    >> import ssl
    >> from socket import socket, AF_INET, SOCK_DGRAM
    >> from dtls import do_patch
    >> do_patch()
    >> sock = ssl.wrap_socket(socket(AF_INET, SOCK_DGRAM))
    >> sock.connect(('foo.bar.com', 1234))
    >> sock.send('Hi there')
    >>
    >> The project is hosted at https://github.com/rbit/pydtls, and licensed
    >> under
    >> the Apache license 2.0. PyPI has packages. I can be reached
    >> at code AT liquibits DOT com for questions, feedback, etc.
    >>
    >> <P><A HREF="http://pypi.python.org/pypi/Dtls/0.1.0">Dtls 0.1.0</A> -
    >> Datagram Transport Layer Security for Python. (07-Jan-13)
    >> --
    >> http://mail.python.org/mailman/listinfo/python-announce-list
    >>
    >> Support the Python Software Foundation:
    >> http://www.python.org/psf/donations/

    >
    >
    >
    > --
    > --Guido van Rossum (python.org/~guido)
    >
    > --
    > http://mail.python.org/mailman/listinfo/python-list
    >
    rbit, Jan 9, 2013
    #1
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