From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp0 ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by ms0.migadu.com with LMTPS id 4PMWJMo0z2CVHgAAgWs5BA (envelope-from ) for ; Sun, 20 Jun 2021 14:30:02 +0200 Received: from aspmx1.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp0 with LMTPS id MOTpH8o0z2DNaQAA1q6Kng (envelope-from ) for ; Sun, 20 Jun 2021 12:30:02 +0000 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by aspmx1.migadu.com (Postfix) with ESMTPS id C28CCD4D9 for ; Sun, 20 Jun 2021 14:30:01 +0200 (CEST) Received: from localhost ([::1]:41462 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1luwaO-0006ma-Hh for larch@yhetil.org; Sun, 20 Jun 2021 08:30:00 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:33256) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lucjS-0006WT-SF for bug-guix@gnu.org; Sat, 19 Jun 2021 11:18:02 -0400 Received: from debbugs.gnu.org ([209.51.188.43]:48937) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1lucjS-00013o-L0 for bug-guix@gnu.org; Sat, 19 Jun 2021 11:18:02 -0400 Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1lucjS-0005zn-CJ for bug-guix@gnu.org; Sat, 19 Jun 2021 11:18:02 -0400 X-Loop: help-debbugs@gnu.org Subject: bug#49035: [gnutls-help] TLS downgrade at bitbucket.org Resent-From: Daiki Ueno Original-Sender: "Debbugs-submit" Resent-CC: bug-guix@gnu.org Resent-Date: Sat, 19 Jun 2021 15:18:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 49035 X-GNU-PR-Package: guix X-GNU-PR-Keywords: To: Ludovic =?UTF-8?Q?Court=C3=A8s?= Received: via spool by 49035-submit@debbugs.gnu.org id=B49035.162411587323032 (code B ref 49035); Sat, 19 Jun 2021 15:18:02 +0000 Received: (at 49035) by debbugs.gnu.org; 19 Jun 2021 15:17:53 +0000 Received: from localhost ([127.0.0.1]:60483 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1lucjI-0005zQ-NN for submit@debbugs.gnu.org; Sat, 19 Jun 2021 11:17:52 -0400 Received: from eggs.gnu.org ([209.51.188.92]:35424) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1lucjF-0005z9-MA for 49035@debbugs.gnu.org; Sat, 19 Jun 2021 11:17:50 -0400 Received: from fencepost.gnu.org ([2001:470:142:3::e]:39478) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lucj8-0000mx-VW; Sat, 19 Jun 2021 11:17:42 -0400 Received: from deisui.org ([219.94.251.20]:60226 helo=localhost.localdomain) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lucj8-0007O9-AG; Sat, 19 Jun 2021 11:17:42 -0400 Message-ID: <87tultyjcl.fsf-ueno@gnu.org> From: Daiki Ueno References: <871r93v665.fsf@inria.fr> <87pmwns3of.fsf@gnu.org> <87eed2re43.fsf_-_@gnu.org> Date: Sat, 19 Jun 2021 17:17:30 +0200 In-Reply-To: <87eed2re43.fsf_-_@gnu.org> ("Ludovic =?UTF-8?Q?Court=C3=A8s?="'s message of "Tue, 15 Jun 2021 23:51:08 +0200") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.0.50 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-Mailman-Approved-At: Sun, 20 Jun 2021 08:29:45 -0400 X-BeenThere: bug-guix@gnu.org List-Id: Bug reports for GNU Guix List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: 49035@debbugs.gnu.org, Emmanuel Agullo , gnutls-help@lists.gnutls.org Errors-To: bug-guix-bounces+larch=yhetil.org@gnu.org Sender: "bug-Guix" X-Migadu-Flow: FLOW_IN ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=yhetil.org; s=key1; t=1624192202; h=from:from:sender:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding:resent-cc: resent-from:resent-sender:resent-message-id:in-reply-to:in-reply-to: references:references:list-id:list-help:list-unsubscribe: list-subscribe:list-post; bh=e8L7RJo/1uZOZBGXcziuVsCKqFvFmNDUp44choG+9sA=; b=SRLp5PFlcDS1YpwxNnub1dis/jRHW6eWRwAAovFA1O6pySqyzCSMe3Djridi7l/pFrZznZ K+yppptv//yYxKM+oG9ZPYgWMZUdPg0j+Z2SgtHY4frErzuevGMwwFfQRncNGvaJYniRfZ mJ8G4bzBCJ8E7UOvLyN4+hXJocDBe2VudkPu3TvH9iUZRMx4qMCtD20VJ9xLg5l7NY4OJ0 7CWc6QzT7lUcnzg1t74Q8xBLNjRew3IJqXSkKVdMU7tMp9xGXLzwCr6VgfgmRJXbEw/FSi aQgbe0ePpaiDJGAAKbv0aHVHzMM40c77pp6w8q0xtUFUSOGK4PMNRnbzxXVY3A== ARC-Seal: i=1; s=key1; d=yhetil.org; t=1624192202; a=rsa-sha256; cv=none; b=mcGO9NSNcYHjgUW6uk99FkY6Di33HAe0Be7KYjRyXCIl5tFFu1JVPKCrbm4D7u10ErXadR 8pY/vLHNOGz+UrzkkUwh9X2qFyT+/lqRqdGbY9yWDpF/u/6lDfoxQnUflphIo2Zlr+RYWK OoJwqlAUnc6z6Di9rzBcqdohga+nTlMOVksptTkP4/e7tbLqIBtHkdRDk6y0FcHqvu4ier baQHMO+bIClBmUm39Vno1kOejo3HhA3oR33jFIiVUYNHWqrhSZ94PiZNnQ2SM4pIh+32bI DoRdb5PGn4UmokNEta/dYF+PH5YnRCDEsS7fUx2vLSxnMYr0h36btoraiPLtVA== ARC-Authentication-Results: i=1; aspmx1.migadu.com; dkim=none; dmarc=pass (policy=none) header.from=gnu.org; spf=pass (aspmx1.migadu.com: domain of bug-guix-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=bug-guix-bounces@gnu.org X-Migadu-Spam-Score: -1.93 Authentication-Results: aspmx1.migadu.com; dkim=none; dmarc=pass (policy=none) header.from=gnu.org; spf=pass (aspmx1.migadu.com: domain of bug-guix-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=bug-guix-bounces@gnu.org X-Migadu-Queue-Id: C28CCD4D9 X-Spam-Score: -1.93 X-Migadu-Scanner: scn0.migadu.com X-TUID: mXXbEguJjHna Ludovic Court=C3=A8s writes: > $ gnutls-cli --priority=3D"NORMAL:-ARCFOUR-128:-CTYPE-ALL:+CTYPE-X509:-VE= RS-SSL3.0:-VERS-TLS-ALL:+VERS-TLS1.0:+VERS-TLS1.1:+VERS-TLS1.2:+VERS-TLS1.3= " -p https bitbucket.org > Processed 444 CA certificate(s). > Resolving 'bitbucket.org:https'... > Connecting to '2406:da00:ff00::6b17:d1f5:443'... > |<1>| Detected downgrade to TLS 1.2 from TLS 1.3 > *** Fatal error: An illegal parameter has been received. [...] > The key thing here is =E2=80=9CDetected downgrade to TLS 1.2 from TLS 1.3= =E2=80=9D. > > Why is a downgrade detected when using the most explicit priority > string and not when using the shorter string? I would say this is an expected behavior when the TLS downgrade protection mechanism[1] is in action. What happens is as follows: - the client advertises TLS 1.0, TLS 1.1, TLS 1.2, and TLS 1.3 (in this order) in the supported_versions extension - the server skips TLS 1.0 and TLS 1.1 (maybe it's disabled), sees TLS 1.2 first in supported_versions, then TLS 1.3; while it also supports TLS 1.3, as TLS 1.2 has precedence and it selects TLS 1.2 and sends the downgrade sentinel in server_random - the client sees the sentinel while TLS 1.3 is enabled, treats it as an unwanted protocol downgrade > Aren=E2=80=99t these two priority strings supposed to be equivalent today? No. If -VERS-TLS-ALL is used, the default priorities on TLS versions in NORMAL are ignored; the user is responsible for building the priority string so it reflects the actual preference, which in this case is: -VERS-TLS-ALL:+VERS-TLS1.3:+VERS-TLS1.2:+VERS-TLS1.1:+VERS-TLS1.0 Footnotes: [1] https://datatracker.ietf.org/doc/html/rfc8446#section-4.1.3 Regards, --=20 Daiki Ueno