Return-Path: Received: from smtp1.linuxfoundation.org (smtp1.linux-foundation.org [172.17.192.35]) by mail.linuxfoundation.org (Postfix) with ESMTPS id 54EDC9D for ; Thu, 9 Jun 2016 01:24:11 +0000 (UTC) X-Greylist: whitelisted by SQLgrey-1.7.6 Received: from mail-vk0-f51.google.com (mail-vk0-f51.google.com [209.85.213.51]) by smtp1.linuxfoundation.org (Postfix) with ESMTPS id BEEE2FB for ; Thu, 9 Jun 2016 01:24:10 +0000 (UTC) Received: by mail-vk0-f51.google.com with SMTP id d64so35693775vkb.0 for ; Wed, 08 Jun 2016 18:24:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to; bh=1dy2zl0uqy9IhhLncVZsoXT2oM1yhbvQo7MAqc0EvIU=; b=y65P5bPst/wu87RcoopWma6qurKzrERFMzf9Qqw52F1irfO3ZD/ebilSVf9p6afZ5Z svH3bPifjJwwyZDAGk9VqLyypTcmSLfzy8qGkeWDaTfaPpfOlmOokugDW4rZcM04bfOE 5NrnT3RiL9lO0fh50kROiXV648Un6invZZbD5wAfVyCCJLi7TLrjDGzHWswthryfXX+7 oUgeBxia68b+nLpfPMnViJWvxh7im3hO/VzhRHpOyTgabxXPA+Qbj2fG2+f+oXaqCCSn GPvjakgxkC4zo/PqzpPC0j73Z4YrOo/FRYL2o0lBZ8wSYt1nHI9OJ+e1Al6l87crUdNu Ef6A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to; bh=1dy2zl0uqy9IhhLncVZsoXT2oM1yhbvQo7MAqc0EvIU=; b=Z9cGwMra4DhcqbaeHI9jCDalxDosvVdfd02q0zaG97thkGhzD7dzh2j5q7J4d97tUT vNopiXDD/YQhDY0GHATbsoy0puBqYEVYeGTqfEkPWfECvucKM2xjOrVHSIJxU8diYc0W owWi5P5kqj7sgM5+JjVXb5Zj1hY5ZjA/vWANCckCJQ4c38/w1Ao1hUpkXrvT+4XO+053 97kow9uwPFn6xNH9pLJZw2MtMs+qIHH60xkwoYX3Sz0wF1juVragcnSvC84bviCtH6BM uco7VXDAHuRFjqtpcu4HXSA4sGTKayR+jotKgcEWQ1eeYYrk6ZoTa6UquBHIlE/DN21X Yhig== X-Gm-Message-State: ALyK8tLdPLOA34n0LEgoKx8+QQAbrq1M2RMHiOp1AXWxq3u19t4rfUcCJOcH4PPfUo4SDdBcZLIpM27LxLx0Rw== X-Received: by 10.31.205.70 with SMTP id d67mr3712777vkg.141.1465435449912; Wed, 08 Jun 2016 18:24:09 -0700 (PDT) MIME-Version: 1.0 Sender: gmaxwell@gmail.com Received: by 10.103.97.135 with HTTP; Wed, 8 Jun 2016 18:24:09 -0700 (PDT) In-Reply-To: <20160608234728.GQ32334@dosf1.alfie.wtf> References: <20160608234728.GQ32334@dosf1.alfie.wtf> From: Gregory Maxwell Date: Thu, 9 Jun 2016 01:24:09 +0000 X-Google-Sender-Auth: DOCd6cv0hREgnlfOVwBOnonY4gc Message-ID: To: Alfie John , Bitcoin Protocol Discussion Content-Type: text/plain; charset=UTF-8 X-Spam-Status: No, score=-2.6 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID, FREEMAIL_FROM, RCVD_IN_DNSWL_LOW autolearn=ham version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on smtp1.linux-foundation.org Subject: Re: [bitcoin-dev] BIP 151 MITM X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.12 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 09 Jun 2016 01:24:11 -0000 On Wed, Jun 8, 2016 at 11:47 PM, Alfie John via bitcoin-dev wrote: > Hi folks, > > Overall I think BIP 151 is a good idea. However unless I'm mistaken, what's to > prevent someone between peers to suppress the initial 'encinit' message during > negotiation, causing both to fallback to plaintext? > > Peers should negotiate a secure channel from the outset or backout entirely > with no option of falling back. This can be indicated loudly by the daemon > listening on an entirely new port. Reduction to plaintext isn't an interesting attack vector for an active attacker: they can simply impersonate the remote side. This is addressed via authentication, where available, which is done by a separate specification that builds on this one. Without authentication this only provides protection against passive attackers.