From nobody Thu Apr 1 11:14:21 2021 Return-Path: X-Original-To: tls@ietfa.amsl.com Delivered-To: tls@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 828093A1E0D for ; Thu, 1 Apr 2021 11:14:13 -0700 (PDT) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -2.099 X-Spam-Level: X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_MED=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, HTML_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cloudflare.com Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 7uuVgQ7ZDf3M for ; Thu, 1 Apr 2021 11:14:09 -0700 (PDT) Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 5415A3A1E0E for ; Thu, 1 Apr 2021 11:14:09 -0700 (PDT) Received: by mail-qk1-x736.google.com with SMTP id y5so3088100qkl.9 for ; Thu, 01 Apr 2021 11:14:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=TMVwbf24IBzPSpuMa8XxrNsCXTvVZeZcOAeAv1If418=; b=Ww1ffOxuQwhhr3hGLpdGCKdcCJvF5DOi+3DMiFAaa1oWEWWFDhTSNF3uGW6AFhW8uH qAHh6J8IIfXrk2tf20YjVWgdnoYIg5y+yDrq/B2kTUGckmYJASLXfhJBtGJJJS6llqMy hb3PdEnXY/RGAapvSwmuyp5wQPYr0df4CPmd0= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=TMVwbf24IBzPSpuMa8XxrNsCXTvVZeZcOAeAv1If418=; b=iwGsoRfMwEQx5tGmKiae5mfmxBVNimFfFalR4lbvY2b/zxOW2ELhQU8PmCPOO11pFO GatG/X61F49BDWToDX5DtRnqsk2mRTtub6X4aL2dYUpyrpUKU0DVuDb9U5kSr+Rdk3vs ZmxFuTWH7yC4A5XFBmmBaBEYqq8ybz6owRkQGD/J2gSxJoEgnL5hAb3j9Z0w89rQI22i EzMOIgSPxM7G+IaEzOLo7RXYn7+3q6tXTduLbpAn7NOVLrzW7W8GWnNnJwRocQ+BRBtL gYNZBiNYMCCwS/p3cxHAOQAfN6VStywt1uXTPKgj/yr8uuoAgm7CNMi06D2qTkGx6lGZ 2aGg== X-Gm-Message-State: AOAM531IqgDLOMGxCnvy5mqmVnIlngZgPiDXMzYgTPPwNT0qnHmB6jDu +n42EGaBPYVfN7M7VdXrZ/mfLjlqJWVCmsJs2gitAw== X-Google-Smtp-Source: ABdhPJy41SMS3tZ+AGagx843osJpQEkUZblBS1UrUYmRKpyiYQ1TCeNtBMnzcuuHQDf0R00uFqO7JS9M3ByI/M3zpjI= X-Received: by 2002:a05:620a:1528:: with SMTP id n8mr9547480qkk.329.1617300847327; Thu, 01 Apr 2021 11:14:07 -0700 (PDT) MIME-Version: 1.0 References: <8f69f37e-b011-85a3-cd76-75cff00156a2@cs.tcd.ie> In-Reply-To: <8f69f37e-b011-85a3-cd76-75cff00156a2@cs.tcd.ie> From: Christopher Patton Date: Thu, 1 Apr 2021 11:13:56 -0700 Message-ID: To: Stephen Farrell Cc: Martin Thomson , "" Content-Type: multipart/alternative; boundary="000000000000801dac05beed3254" Archived-At: Subject: Re: [TLS] Don't Split HelloRetryRequest X-BeenThere: tls@ietf.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "This is the mailing list for the Transport Layer Security working group of the IETF." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 01 Apr 2021 18:14:19 -0000 --000000000000801dac05beed3254 Content-Type: text/plain; charset="UTF-8" > But let me ask a question meanwhile - how often does HRR > actually happen and could we not just let ECH fail in a > bunch of situations that would otherwise require all this > new complexity? > One way HRR is used is in case the client's and server's cipher suite preferences don't intersect. This feature is an essential part of TLS, as there's no a priori reason why the client and server will initially advertise overlapping preferences. (They usually do, hence the claim that HRR is rare.) I don't think aborting the handshake instead of HRR is an acceptable solution, as this would mean there are deployments with which TLS couldn't be used. Chris P. --000000000000801dac05beed3254 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
=C2= =A0
But let me ask a question meanwhile - how often does HRR
actually happen and could we not just let ECH fail in a
bunch of situations that would otherwise require all this
new complexity?

One way HRR is used is = in case the client's and server's cipher suite preferences don'= t intersect. This feature is an essential part of TLS, as there's no a = priori reason why the client and server will initially advertise overlappin= g preferences. (They usually do, hence the claim that HRR is rare.) I don&#= 39;t think aborting the handshake instead of HRR is an acceptable solution,= as this would mean there are deployments with which TLS couldn't be us= ed.

Chris P.

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