Mailman 3 March 2021 - Twisted-web

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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Re: [Twisted-web] [Twisted-Python] Twisted 21.2.0 Release Announcement
by Craig Rodrigues 01 Mar '21

01 Mar '21

On Sun, Feb 28, 2021 at 1:55 PM Adi Roiban <adi(a)roiban.ro> wrote: > > > > Hi, > > Thanks Craig for managing this release. > You are welcome Adi! I am happy to contribute my efforts to the Twisted community and to push the project along. In 2015-2016, unfortunately I lost my job. While in between jobs, I contributed a lot to the effort to port Twisted to Python 3. It was a very enjoyable experience, and I learned a lot of Python at the time. :) I joined the Python 2 porting party late, and there were others who invested a lot of time and effort into it. Amber did a heck of a lot of work before me on Python 3 porting, and did a lot of work after I contributed. I don't remember who else contributed, but there were a lot of folks including you, Jean- , Glyph, and others. The earliest Python 3 ticket I can find in the Trac is this one from 14 years ago filed by Itamar!! https://twistedmatrix.com/trac/ticket/2484 Honestly, at the time, when I was working on Python 3 porting in 2016, I wasn't even sure that Twisted would survive as a project beyond Python 2. So it is nice to see that Python 2.7 is history, and the Twisted codebase is incorporating new language features, types, etc. and is keeping up with newer Python versions. Hurray! -- Craig

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