From owner-freebsd-net@freebsd.org Sun Nov 24 15:55:25 2019 Return-Path: Delivered-To: freebsd-net@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 08F221B2D85 for ; Sun, 24 Nov 2019 15:55:25 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from hz.grosbein.net (hz.grosbein.net [IPv6:2a01:4f8:c2c:26d8::2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "hz.grosbein.net", Issuer "hz.grosbein.net" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 47LZWH4vN9z49K0 for ; Sun, 24 Nov 2019 15:55:23 +0000 (UTC) (envelope-from eugen@grosbein.net) Received: from eg.sd.rdtc.ru (eg.sd.rdtc.ru [IPv6:2a03:3100:c:13:0:0:0:5]) by hz.grosbein.net (8.15.2/8.15.2) with ESMTPS id xAOFsqVY029819 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sun, 24 Nov 2019 15:54:53 GMT (envelope-from eugen@grosbein.net) X-Envelope-From: eugen@grosbein.net X-Envelope-To: vas@sibptus.ru Received: from [10.58.0.4] (dadv@[10.58.0.4]) by eg.sd.rdtc.ru (8.15.2/8.15.2) with ESMTPS id xAOFsnr3086702 (version=TLSv1.2 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Sun, 24 Nov 2019 22:54:49 +0700 (+07) (envelope-from eugen@grosbein.net) Subject: Re: Several hosts behind a caching resolver To: Victor Sudakov , freebsd-net@freebsd.org References: <20191124123451.GA6593@admin.sibptus.ru> From: Eugene Grosbein Message-ID: Date: Sun, 24 Nov 2019 22:54:46 +0700 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 MIME-Version: 1.0 In-Reply-To: <20191124123451.GA6593@admin.sibptus.ru> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=0.3 required=5.0 tests=BAYES_00,LOCAL_FROM, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.2 X-Spam-Report: * -2.3 BAYES_00 BODY: Bayes spam probability is 0 to 1% * [score: 0.0000] * 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record * -0.0 SPF_PASS SPF: sender matches SPF record * 2.6 LOCAL_FROM From my domains X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on hz.grosbein.net X-Rspamd-Queue-Id: 47LZWH4vN9z49K0 X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=permerror (mx1.freebsd.org: domain of eugen@grosbein.net uses mechanism not recognized by this client) smtp.mailfrom=eugen@grosbein.net X-Spamd-Result: default: False [-3.78 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[grosbein.net]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; R_SPF_PERMFAIL(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; IP_SCORE(-1.68)[ip: (-4.48), ipnet: 2a01:4f8::/29(-2.32), asn: 24940(-1.59), country: DE(-0.01)]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:2a01:4f8::/29, country:DE]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[] X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 24 Nov 2019 15:55:25 -0000 24.11.2019 19:34, Victor Sudakov wrote: > Dear Colleagues, > > Several hosts of the local network use a FreeBSD server with BIND or > local-unbound as a caching resolver. Let's call it "Resolver A." > Resolver A forwards all queries to another resolver, e.g. 8.8.8.8 or > some other, let's call it "Resolver B." > > Can the operator of Resolver B figure out how many clients there are > behind Resolver A, or obtain any other information about the hosts on > the said local network (like their operating system etc)? In other > words, does Resolver A effectively anonymize the queries, or is some > information about the internal network leaking? No anonymization via unencrypted DNS. The query itself reveals most data about clients. Windows OSes send queries for MS-specific domains periodically, Android for its domains, FreeBSD for pkg.freebsd.org or svn.freebsd.org etc. If a there are multiple recursive queries for both of MS/Androis/MacOS-specific domains, this means there are many clients behind this local resolver.