Twisted-web October 2017

twisted-web@python.org

3 participants
4 discussions

Twisted Web Agent configurable Elliptic Curves settings
by Paul Tremberth 16 Dec '21

16 Dec '21

Hello, The other day, we had a Scrapy user report an issue connecting to https://www.skelbiu.lt/ with OpenSSL 1.1 [1] To not mix scrapy's things with Twisted Web, I used this (adapted from official docs): #--------------- from __future__ import print_function from twisted.internet import reactor from twisted.web.client import Agent from twisted.web.http_headers import Headers agent = Agent(reactor) d = agent.request( 'GET', 'https://www.skelbiu.lt/', Headers({'User-Agent': ['Twisted Web Client Example']}), None) def cbResponse(ignored): print('Response received') d.addCallback(cbResponse) def cbShutdown(ignored): print(ignored) reactor.stop() d.addBoth(cbShutdown) reactor.run() #--------------- And I did get a Handshake failure too: $ python twistedtest.py [Failure instance: Traceback (failure with no frames): <class 'twisted.web._newclient.ResponseNeverReceived'>: [<twisted.python.failure.Failure OpenSSL.SSL.Error: [('SSL routines', 'ssl3_read_bytes', 'sslv3 alert handshake failure')]>] ] It seems this happens (at least) with OpenSSL 1.1.0e (currently in Debian 9 sid [2]) It does not happen (for me) with OpenSSL 1.0.2g for example. I dug into this this afternoon and narrowed it down to the use of _defaultCurveName = u"prime256v1" in twisted.internet._sslverify.py I tried patching the current trunk with _defaultCurveName = u"secp384r1" (the EC that ssllabs.com reports) and it did work. Looking at ClientHello messages for openssl 1.0.2 and 1.1 [4]: with 1.1, only 1 Elliptic Curve is sent by Twisted Web Agent, secp256r1 openssl v1.1 client uses 4 by default: ecdh_x25519, secp256r1, secp521r1, secp384r1 I was wondering what is the proper way to configure requested Elliptic Curves. I haven't seen any interface for this, contrary to ciphers with acceptableCiphers. Thank you for your input. Best, Paul. [1] https://github.com/scrapy/scrapy/issues/2717 [2] https://packages.debian.org/fr/source/sid/openssl [3] https://github.com/twisted/twisted/blob/78679af87e349721a167f35bef239e192e9… [4] https://github.com/scrapy/scrapy/issues/2717#issuecomment-297464034

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Test
by Philippe Lafoucrière 05 Aug '21

05 Aug '21

Hi all just a test

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Twisted Application(Daemon) with multiple clients
by Daniel Doron 23 Oct '17

23 Oct '17

Hi, Sorry in advance for sending this to both Twisted mailing list. i was not sure for which was it was most appropriate. I have a design in which I would like to have a Twisted Application which would periodically connect to a REST Server to pull configuration information, i.e. as client and upon receiving that information and processing would communicate spawn 1 or more clients connecting to local process via Unix sockets to send them configuration information. I think I understand how the standard approach would be: 1. create a function that would be called with callLater/LoopingCall 2. in that function create my client, connect to the REST Server, get info etc... So: 1. Do you think my approach is correct? Essentially as explained I need a service/daemon to periodically connect ot one server to pull information and then connect to other local process to forward them the relevant configuration. 2. How do I turn this into a twisted plugin? (daemon) Thanks -Daniel

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Twisted HTTPS Server-Client Communication problem
by Ohad Shai 23 Oct '17

23 Oct '17

Hi, I have an important question about twisted HTTPS client-server communication. I ran an HTTPS server with my own certs and tried to communicate with a twisted HTTPS client with the specific cert. I am getting an error that says: "Invalid DNS-ID". all the error info with all my code is in here: https://gist.github.com/anonymous/e46d4d8dc1c102857497cde9e2fc4725#file-gis… Twisted-HTTPS-client-server<https://gist.github.com/anonymous/e46d4d8dc1c102857497cde9e2fc4725#file-gis…> gist.github.com Twisted-HTTPS-client-server I will be appreciate if someone has a clue how can I fix this error. Thanks, Ohad Shai Software Engineer, EDR Linux 972-052-6887792 ohad.shai(a)cyberbit.com<mailto:daniel.doron@cyberbit.com>

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Twisted-web October 2017