Re: [Doh] Privacy Considerations Text (#2)
Eric Rescorla <ekr@rtfm.com> Thu, 21 June 2018 18:56 UTC
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From: Eric Rescorla <ekr@rtfm.com>
Date: Thu, 21 Jun 2018 11:56:06 -0700
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To: Patrick McManus <pmcmanus@mozilla.com>
Cc: DoH WG <doh@ietf.org>
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Subject: Re: [Doh] Privacy Considerations Text (#2)
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Can you please enable comments on the PR so that people can provide detailed feedback -Ekr On Thu, Jun 21, 2018 at 11:43 AM, Patrick McManus <pmcmanus@mozilla.com> wrote: > Hi All, > > We may be getting close to bridging the important points here - so we've > made an update to the PR. (its still not merged into the working copy, but > it has changed). and we can iterate from there. Thank you for the comments, > and especially text proposals - they really help. > > The live copy is at https://github.com/dohwg/ > draft-ietf-doh-dns-over-https/pull/200 and I'll snapshot it again at the > end of this email > > The deltas make more explicit comparisons between DoH and Do(TLS), calls > out some rationale about the full ecosystem in the same text that asks you > to consider the cost/benefits of http features, and includes the new text > about a minimal data set. > > -Patrick > > # Privacy Considerations {#PrivacyConsiderations} > > {{RFC7626}} discusses DNS Privacy Considerations in both "On the > wire" (Section 2.4), and "In the server" (Section 2.5) contexts. This > is also a useful framing for DoH's privacy considerations. > > ## On The Wire {#OnTheWire} > > DoH encrypts DNS traffic and requires authentication of the > server. This mitigates both passive surveillance {{RFC7258}} and > active attacks attempting to divert DNS traffic to rogue servers > ({{RFC7626}} Section 2.5.1). DNS over TLS {{RFC7858}} provides > similar protections, while direct UDP and TCP based transports are > vulnerable to this class of information leak. > > Additionally, the use of the HTTPS default port 443 and the ability to > mix DoH traffic with other HTTPS traffic on the same connection can > deter on-path devices from interfering with DNS operations and make > DNS traffic analysis more difficult. > > ## In The Server {#InTheServer} > > A DoH application is built on IP, TCP, TLS, and HTTP. Each layer > contains one or more common features that can be used to correlate > different queries to the same identity. DNS transports will generally > carry the same privacy properties of the layers used to implement > them. For example, the properties of IP, TCP, and TLS apply to DNS > over TLS implementations. > > The privacy considerations of using the HTTPS layer in DoH are > incremental to those of DNS over TLS. DoH is not known to introduce > new concerns beyond those associated with HTTPS. > > At the IP level, the client address provides obvious correlation > information. This can be mitigated by use of a NAT, proxy, VPN, or > simple address rotation over time. It may be aggravated by use of a > DNS server that can correlate real-time addressing information with > other personal identifiers, such as when a DNS server and DHCP server > are operated by the same entity. > > TCP-based solutions may seek performance through the use of TCP Fast > Open {{RFC7413}}.. The cookies used in TCP Fast Open allow servers to > correlate different TCP sessions together. > > TLS based implementations often achieve better handshake performance > through the use of some form of session resumption mechanism such as > session tickets {{RFC5077}}. Session resumption creates trivial > mechanisms for a server to correlate different TLS connections > together. > > HTTP's feature set can also be used for identification and tracking in > a number of different ways. For example, authentication request header > fields explicitly identify profiles in use, and HTTP Cookies are > designed as an explicit state tracking mechanism between the client > and serving site and often are used as an authentication mechanism. > > Additionally, the User-Agent and Accept-Language request header fields > often convey specific information about the client version or locale. > This facilitates content negotiation and operational work-arounds for > implementation bugs. Request header fields that control caching > can expose state information about a subset of the client's > history. Mixing DoH requests with other HTTP requests on the same > connection also provides an opportunity for richer data correlation. > > The DoH protocol design allows applications to fully leverage all the > features of the HTTP ecosystem, including features not enumerated > here. Implementations of DoH clients and servers need to consider the > benefit and privacy impact of these features, and their deployment > context, when deciding whether or not to enable them. Implementations > should expose the minimal set of data needed to achieve the desired > feature set. > > > _______________________________________________ > Doh mailing list > Doh@ietf.org > https://www.ietf.org/mailman/listinfo/doh > >
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Mateusz Jończyk
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Paul Hoffman
- [Doh] Privacy Considerations Text (#2) Mateusz Jończyk
- Re: [Doh] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] Privacy Considerations Text (#2) nusenu
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Eric Rescorla
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Paul Hoffman
- Re: [Doh] Privacy Considerations Text (#2) Eric Rescorla
- Re: [Doh] Privacy Considerations Text (#2) Hewitt, Rory
- [Doh] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] Privacy Considerations Text (#2) Howard Chu
- Re: [Doh] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] Privacy Considerations Text (#2) nusenu
- Re: [Doh] Privacy Considerations Text (#2) nusenu
- Re: [Doh] Privacy Considerations Text (#2) Sara Dickinson
- Re: [Doh] Privacy Considerations Text (#2) Joseph Lorenzo Hall
- Re: [Doh] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] Privacy Considerations Text (#2) Joseph Lorenzo Hall
- Re: [Doh] Privacy Considerations Text (#2) Andrew Sullivan
- Re: [Doh] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Hewitt, Rory
- Re: [Doh] Privacy Considerations Text (#2) Sara Dickinson
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Patrick McManus
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Mateusz Jończyk
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Ray Bellis
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Paul Hoffman
- Re: [Doh] [Ext] Privacy Considerations Text (#2) Patrick McManus