Internet DRAFT - draft-dickson-dnsop-spartacus-system
draft-dickson-dnsop-spartacus-system
dnsop B. Dickson
Internet-Draft
Intended status: Standards Track October 15, 2014
Expires: April 18, 2015
System to transport DNS over HTTP using JSON
draft-dickson-dnsop-spartacus-system-00
Abstract
This is the SPARTACUS DNS gateway system. It is designed to
facilitate the transport of DNS messages opaquely, across problematic
sections of the Internet. It uses JSON encoding, and HTTP(S) as the
protocol for transport.
The main criteria of SPARTACUS is that it preserve DNS messages
verbatim, and that only properly formatted DNS messages are passed.
There are two modes (so far) defined: DNS forwarder (dns clients
point to a local gateway, which forwards to a remote gateway for
sending to a DNS resolver); and transparent proxy (DNS packets are
intercepted, passed to a local gateway, which sends them to the
remote gateway, with original destination IP address etc. encoded,
and used by the remote gateway as the destination).
DNS messages are NAT-friendly, so changes to IP or UDP headers do not
impact them. Thus, SPARTACUS does not interfere with TSIG, SIG(0),
or Eastlake Cookies.
This document describes the system, the components, and behavior,
with examples.
Author's Note
Intended Status: Proposed Standard.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
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This Internet-Draft will expire on April 18, 2015.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 3
1.2. Rationale . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Related Work . . . . . . . . . . . . . . . . . . . . . . 5
1.3.1. Comparison . . . . . . . . . . . . . . . . . . . . . 5
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6
3. System Overview . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. System Elements . . . . . . . . . . . . . . . . . . . . . 7
3.1.1. Node Types . . . . . . . . . . . . . . . . . . . . . 7
3.2. System Modes . . . . . . . . . . . . . . . . . . . . . . 7
3.2.1. Details on DNS Forwarder mode . . . . . . . . . . . . 8
3.2.2. Details on Transparent Proxy mode . . . . . . . . . . 9
3.3. Interoperability . . . . . . . . . . . . . . . . . . . . 11
3.3.1. In-scope and out-of-scope . . . . . . . . . . . . . . 11
4. Interactions and Behavior . . . . . . . . . . . . . . . . . . 12
4.1. DNS Gateway Encodings . . . . . . . . . . . . . . . . . . 13
4.2. UDP Packet Loss . . . . . . . . . . . . . . . . . . . . . 13
4.3. Malformed UDP response . . . . . . . . . . . . . . . . . 13
4.4. DNSSEC Validation Failure . . . . . . . . . . . . . . . . 14
5. Client-Server Selection and Topology Examples . . . . . . . . 14
5.1. Mixed Traffic Walk-Through . . . . . . . . . . . . . . . 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
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9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18
Appendix A. DNS Message Encoding Examples . . . . . . . . . . . 18
A.1. Simple Query/Answer, No EDNS or DNS Server . . . . . . . 19
A.2. Simple Query/Answer, EDNS, no DNS Server . . . . . . . . 21
A.3. Simple Query/Answer, no EDNS, with DNS Server . . . . . . 24
A.4. Simple Query/Answer, with EDNS and DNS Server . . . . . . 28
Appendix B. Server Gateway HTML code . . . . . . . . . . . . . . 32
Appendix C. Server Gateway HTTP POST Handler Pseudo-code . . . . 32
Appendix D. Client Gateway Pseudo-code . . . . . . . . . . . . . 33
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction
DNS (The Domain Name System) has been deployed since the 1980's
[RFC1033][RFC1034][RFC1035]. Since that time, some of the original
Resource Record types have been made officially obsolete [RFC3425].
Some elements have been clarified [RFC2181][RFC2308]. New Resource
Records have been added [RFC2136][RFC2845][RFC2930][RFC6891]. New
definitions of bits in the header have arisen, in part due to
DNSSEC's AD and CD bits [RFC4033][RFC4034][RFC4035][RFC5155].
This has resulted in now-outdated implementations of stateful devices
(e.g. devices doing either NAT or packet inspection) interfering with
end-to-end communication between DNS speakers. Old devices or
implementations reject DNS packets that include these newer
capabilities, features, or format changes.
At the same time, there has arisen a variety of other devices and
systems whose deliberate function is to block, capture, or modify DNS
traffic, for profit or for ideological reasons. Examples include
hotel wifi systems, ISPs, and state actors.
Owing to the stateless nature of DNS over UDP, it is not possible to
distinguish between deliberate and accidental sources of DNS
interference.
1.1. Problem Statement
There is a need to provide ways of supporting incremental deployment
of new DNS features, in such a way as to prevent deliberate and/or
accidental interference in the communication between DNS speakers.
For example, DNS speakers could communicate over protected channels
and with data integrity validation via DNSSEC. The foremost
limitation is that the communication be over any other port/protocol
combination than UDP port 53. Ideally, the choice should be an
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encoding that is compatible with whatever port/protocol combination
is selected (versus overloading the port/protocol with incompatible
payloads).
There is a further need for the communications channel(s) to be
standardized, and to not introduce further interoperability problems
at the DNS protocol level. Independent implementations need to
interoperate completely, to avoid merely pushing the compatibility
problem around.
In order to solve these problems (individually and/or collectively),
the SPARTACUS system has been developed.
1.2. Rationale
SPARTACUS (Secure, Private Aparatus for Resolution Transported Across
Constraining and/or Unmaintained Systems), is a system for encoding
and decoding DNS messages (the DNS payload of UDP or TCP packet
streams).
The SPARTACUS system consists of bidirectional DNS gateways for
transporting DNS over HTTP(S) using a JSON encoding scheme. This is
intended to create "bridges" between DNS speakers; perhaps a better
analogy would be "ferries", as there is no requirement for a tightly
bound relationship between individual Client nodes and Server nodes.
Standardizing the JSON encoding used by SPARTACUS, is intended to
ensure a greater likelihood of compatible, interoprable
implementations.
The goal is to transport DNS messages from any Client implementation
to any Server implementation.
Each gateway must be liberal in what it accepts (any valid DNS
message conforming to the relevant RFCs, regardless of DNS
implementation) and conservative in what it sends (all packets must
parse correctly as DNS messages). In order to ensure forward
compatibility, unknown Types and (in the case of OPT) sub-types, MUST
be accepted and transported.
DNS messages MUST traverse the encode/decode process unaltered. The
round-trip is designed to, and MUST be implemented to, preserve the
entire DNS message's fidelity. This means a 1:1 binary match between
input, encoding, decoding, and output. The lengths MUST match, and
messages MUST be identical, bit for bit.
A secondary objective of the encoding in JSON is the use of the same
names for data elements and structures as in the DNS RFCs. The idea
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is to provide human-readable JSON encodings, for easier diagnostics
during development, and when investigating operational issues.
1.3. Related Work
A variety of other work exists, and provided inspiration for the
SPARTACUS work. This includes web/JSON DNS portals, for providing
DNS query responses in JSON format, often with a "looking glass"
functionality. FIXME format this list appropriately and decorate
with words. END FIXME
o Multi-location DNS Looking Glass - Tool for performing DNS queries
via RESTful interface in multiple locations, returning results in
JSON format
o DNS Looking Glass - Tool for performing DNS queries via RESTful
interface, returning results in JSON format
o DNS JSON - Source code project from circa 2009, partially
developed but incomplete/abandoned
o DNSSEC-trigger[trigger] - embedded control function in NLnetlabs'
Unbound resolver, for attempting DNS queries over TCP port 80 when
DNSSEC problems are encountered
o Various other web-based DNS lookup tools
1.3.1. Comparison
There has been at least one previous effort to develop code for a
DNS-JSON encoding, which appears to have been abandoned after one-way
encoding was done, circa 2009. The project focused on presenting
results to DNS queries in JSON format, with an intention to create a
client gateway, which never materialized. The project can be found
in two places ([JPF_jsondns] and [jsondns.org]). One major
difference is that DNS query response status is converted to HTTP
error codes, rather than being embedded in the JSON answer. This
makes it unsuitable for bidirectional use. Only a few DNS type codes
were implemented.
Another DNS JSON tool [fileformat.info], similarly focuses only on
answers, with a limited number of type codes.
Yet another tool for looking up DNS via HTTP with JSON responses is
the "dnsrest" [restdns.net]. It too focuses only on answer values,
and is similarly not able to fully produce results that can be turned
back into DNS answer packets.
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The "DNS Looking Glass" [bortzmeyer.org], is primarily designed for
returning DNS answer data. As such, it lacks encoding suitable for a
bidirectional scheme. It is primarily focused on XML output, with
JSON output organized around DNS resolution meta-data, plus answer
data in a generic schema. (The schema itself is described in
[draft-bortzmeyer-dns-json].)
The "Multilocation DNS Looking Glass" [dns-lg.com], uses a RESTful
query mechanism of "node/qname/qtypename" to request the looking
glass (LG) to perform a DNS lookup for the qname and qtype, and
returns the response in a JSON format. The JSON format is generic,
encapsulating all types as string data in presentation format, with a
generic label of "rdata". This does not facilitate decoding easily,
as the JSON scheme provides no information for parsing the rdata
field. The type (qtype for the query, or type for answer/authority/
additional) is in string (symbolic) form, and the elements are
objects and thus in unordered lists. The JSON scheme is fine for
one-way encoding for human readability, but not suitable for two-way
conversion back into DNS.
DNSSEC-trigger[trigger] can only be used in environments that use
NLnetlabs' Unbound resolver, or where Unbound can be deployed as a
replacement for existing recursive resolvers and/or stub resolvers.
A variety of other web lookup tools exist, predominantly producing
DNS validation (zone structure and hierarchy), maps, meta-data, or
literal output from the 'dig' tool, in formats as varied as the
purposes of the tools. Dig output, while being reasonably
deterministic, is not sufficiently well-formed as to facilitate
"screen scraping" as a parsing method.
2. Requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
3. System Overview
The SPARTACUS system is designed to improve the reliability and
security of the DNS system, by providing the means to transport DNS
traffic across segments of the Internet. The goal is to bypass
problem areas which interfere with DNS communications, regardless of
root cause of the interference.
Some familiarity with the DNS protocol is assumed.
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3.1. System Elements
The particular system elements used will differ, based on the mode of
operation of the Client. Clients may request the use of particular
resolvers via additional intra-element signalling.
3.1.1. Node Types
Base node types are the following:
o Standalone SPARTACUS Client forwarder
o Transparent SPARTACUS proxy Client
o Standalone SPARTACUS Server
o Apache module-based SPARTACUS Server
o Stub resolver
o External recursive resolver
o Client-side recursive resolver
o External authority server
Future node types are expected to include:
o Browser-integrated SPARTACUS client and stub resolver
o Mobile-device SPARTACUS client and stub resolver (with exposed
getdns API)
o SMTP-integrated SPARTACUS client and stub resolver
3.2. System Modes
The system has two modes of operation:
o DNS Forwarder - an opaque mode of operation, the Client/Server
pair act collectively as a single DNS forwarder.
o Transparent Proxy - In this mode, regular DNS traffic is diverted
by unspecified means to the SPARTACUS Client.
Additional intra-element signalling facilitates Clients requesting
particular resolvers' (recursive or authoritative) use.
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3.2.1. Details on DNS Forwarder mode
The Server is configured to use a particular DNS recursive resolver,
with the optional ability to support Client-requested resolver(s) via
in-band signaling. If present, the Client-requested resolver IP
address is passed as an EDNS OPT value. The Server, if it is
configured to honor requested resolvers, uses this IP address instead
of the default.
Example: Problem caused by firewalls that do not support DNSSEC:
+------+ +--------------+ +----------+
| | | | Blocked | |
| Stub +--> | Old Firewall +----+X+---> | Resolver |
| | | (no DNSSEC) | Packets | |
+------+ +--------------+ +----------+
Figure 1
Example: How the stub client sees the SPARTACUS Client/Server pair,
in the opaque forwarder configuration:
+------+ +----------------------------------+ +----------+
| | | | | |
| Stub +--> | Forwarder +----> | Resolver |
| | | with DNSSEC | | |
| | <--+ | <----+ |
+------+ +----------------------------------+ +----------+
Figure 2
Example: How the Client/Server pair actually operates:
+------+ +--------+ +--------+ +----------+
| | | | | | | |
| Stub +---> | Client +-------------> | Server +----> | Resolver |
| | DNS | | JSON/HTTP(S) | | DNS | |
| | <---+ | <-------------+ | <----+ |
+------+ +--------+ +--------+ +----------+
Figure 3
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Example: How the Client/Server bypass the old firewall:
+------+ +--------+ +--------------+ +--------+ +----------+
| | | | | Old Firewall | | | | |
| Stub +-> | Client +------------------> | Server +-> | Resolver |
| | | | | (bypassed) | | | | |
| | <-+ | <------------------+ | <-+ |
+------+ +--------+ +--------------+ +--------+ +----------+
Figure 4
3.2.2. Details on Transparent Proxy mode
Transparent Proxy mode supports transport of stub to recursive
traffic (all with the same destination IP address).
Transparent Proxy mode also supports use by a recursive resolver, to
handle recursive-to-authoritative traffic (with different destination
IP addresses per query).
From the perspective of the DNS client (stub or recursive), it
appears that the DNS query packet went to some IP address, and the
reply came back directly.
+----------+ +--------------+
| +------------------------------------> | |
| Stub | | Recursive |
| src=SR | DNS UDP/53 SR<->RR | dst=RR |
| | | |
| | <------------------------------------+ |
+----------+ +--------------+
Figure 5
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+-----------+
| +-----------------------------------> +--------------+
| | | Authority #1 |
| | <-----------------------------------+ dst=AR_1 |
| | +--------------+
| +-----------------------------------> +--------------+
| Recursive | | Authority #2 |
| src=RR | <-----------------------------------+ dst=AR_2 |
| | +--------------+
| | ...
| +-----------------------------------> +--------------+
| | | Authority #N |
| | <-----------------------------------+ dst=AR_N |
+-----------+ +--------------+
DNS UDP/53 RR<->AR_N (N=1,2,...)
Figure 6
In both use cases, the original IP destination is encoded as an EDNS
OPT value, and the DNS message (encoded as JSON) is sent to the
SPARTACUS Server. The Server sends the DNS message to the original
IP destination, with the SPARTACUS Server's IP address as the source.
The resulting answer DNS message is sent to the Client, which changes
the reply source IP address to the original destination IP address.
+-----------+ +-------+ +---------+ +---------------+
| | | | | | | |
| +----------> | Trans.| | Server +-> | Authoritative |
| | | Proxy | | Gateway | | Resolver #1 |
| | <----------+ TP | | SG | <-+ AR_1 |
| | +-----+-+ +------+--+ +---------------+
| | DNS UDP/53 | | DNS UDP/53
| Recursive | RR <-> AR_1 ^ v ^ | SG <-> AR_1
| Resolver | | | |
| RR | +---+-----+ | |
| | | Client +----+ | TCP/80 (or /443)
| | | Gateway | | JSON (EDNS: dst=AR_1)
| | | CG | <-----+ CG <-> SG
+-----------+ +---------+
Figure 7
The only practical difference is that some intermediate devices see
JSON/HTTP(S) instead of DNS/UDP traffic. For some of those devices,
this is in fact the purpose of SPARTACUS - preventing those devices
from inspecting the DNS traffic in a problematic manner.
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3.3. Interoperability
The purpose of this document is to ensure that independent
implementations of Client(s) and Server(s) can interoperate, so long
as each is permitted to interoprate with the other.
It is not required that Servers be operated in a completely "open"
manner. However, the more open Servers there are, the greater the
benefit. Like any web-based service, care should be given towards
managing available resources on a Server. In all likelihood, this
resource management may be most effectively handled via the web
server's own service management system.
3.3.1. In-scope and out-of-scope
The following items are out-of-scope, from an interoperability
standpoint.
This means that individual implementations may make independent
design decisions, without impacting interoperability.
o Choice(s) of default resolver (on Server)
o Server-side DNS retry and time-out values
o How Client(s) select Servers
The following items are in-scope, from an interoperability
standpoint.
o JSON encoding
o How to signal non-support of requested resolver(s)
o How to signal "no response" (timeout) on Server-resolver traffic
o Signalling/encoding of default,requested, and actually-used
resolvers
o Stripping of EDNS OPT private values
o Stripping of synthesized EDNS OPT record
The following items are optional, from an interoperability
standpoint.
o Whether and how to do edns-client-subnet (on Client)
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o Whether to use TLS (HTTPS) on Client-Server traffic
o Whether to honor requested resolvers (on Server)
o Whether to support Transparent Proxy mode (on the Client)
o Whether to do DNSSEC validation
o Whether to do PKI validation of SSL certificates (if HTTPS is used
and CA-issued certs used)
o Whether to do DANE validation of SSL certificates (if HTTPS is
used and TLSA records exist)
o Whether IPv4 or IPv6 is supported
4. Interactions and Behavior
The Client Gateway needs to make informed decisions about Server
Gateways to use. Client Gateways may use pre-configured (static)
gateways, or may employ any number of strategies for selection of
Server Gateways.
In order to enble Client-controlled Server Selection, each Server
Gateway needs to advise the Client about default and actual DNS
Servers used. The Client optionally requests DNS Server(s) that the
Server should use. If present, the Server includes that in the
response.
The SPARTACUS client/server interaction occurs over TCP rather than
UDP. As such, other than TCP-based failures (RST aka "reset" for
example), every query MUST get a response (owing to the HTTP POST
standards).
Since the Server Gateway is performing DNS resolution using UDP
transport, it is possible that network packet loss may occur,
resulting in unanswered queries.
Also, there are reasons other than network-based packet loss that can
result in unanswered queries. DNS resolvers must attempt to infer
what causes queries to not be answered.
It is also possible that various other failure modes could occur,
which need to be handled on the basis of the nature of the failure.
Each of these is addressed in separate sections below.
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4.1. DNS Gateway Encodings
The three DNS Server values (default, requested, actual) are
communicated via EDNS OPT type-length-value (TLV) tuples, using three
distinct types. Pre-standard experimental values are presently being
used. IANA will need to assign permanent OPT Type values for these
three type codes.
In order to ensure that the EDNS OPT record is only returned to the
original DNS client if it existing in the query, it is necessary to
identify cases where the DNS Server value encoding resulted in a
"new" OPT record, rather than being added to an existing record. In
such cases, an additional OPT TLV type is required, and is added to
the OPT record. A fourth OPT Type value needs to be assigned by IANA
for this purpose.
The new OPT codes are used to enable the Client and Server to
maintain all communication details inside the DNS message itself.
This simplifies the design, implementation, and operation of Clients
and Servers, and ensures forward/backward compatibility. OPT codes
specific to the Client-Server communication MUST be removed prior to
forwarding of DNS messages to DNS Clients and Servers. If the EDNS
OPT RR is synthesized (added to the DNS message), it MUST be removed.
4.2. UDP Packet Loss
In cases where the Server Gateway did not get a response from the DNS
Server, it needs to signal this back to the client. It needs to do
this so that the proper Client state is established. This prevents
time-out based (undefined) behavior on the Client from being
triggered. The Server needs to "pass along" packet loss status to
the Client to trigger well-defined Client behavior.
The mechanism is to use a Private EDNS OPT type/length/value (TLV),
with the original Question echoed back (to associate with the Query).
When receiving this TLV, the Client will treat this as a lost UDP
packet, and MUST NOT send back any UDP packet. The UDP client is
responsible for handling this lost UDP packet, per the DNS protocol.
4.3. Malformed UDP response
The malformed UDP packet may not be legitimate. To be conservative,
this condition is signaled back to the client, and the (actual)
received UDP packet is rejected/dropped. This is treated by the DNS
client as a lost UDP packet.
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4.4. DNSSEC Validation Failure
If DNSSEC validation fails, the presumption needs to be made that the
failure is deliberate. The DNSSEC standards call for "SRVFAIL"
responses, so that is what a compliant implementation MUST return to
the UDP client.
If the Client and/or Server does DNSSEC Validation, it MUST correctly
implement Validation signalling via the AD and CD bits.
In other words, it MUST return the answer regardless of Validation if
the CD bit is set, and it MUST set the AD bit if Validation succeeds,
regardless of the presence and/or state of EDNS bit DO.
5. Client-Server Selection and Topology Examples
+-----------+
| |
+--> | Server +--+
+-----------+ | | Gateway 1 | |
| Client | | +-----------+ | +-----------+
| Gateway +--+ +-----------+ +--> | |
| | | | | Recursive |
| Selects +-----> | Server +-----> | DNS |
| Random | | Gateway 2 | | Server |
| Server +--+ +-----------+ +--> | |
| Gateway | | +-----------+ | +-----------+
+-----------+ | | | |
+--> | Server +--+
| Gateway 3 |
+-----------+
Figure 8
Figure 8 shows the same Recursive DNS Server being used, via multiple
Server Gateways. There are several benefits to doing this; they
include distributing load among multiple Server Gateways, and
reducing the amount of DNS traffic going via any single Server
Gateway. This limits the impact of the compromise of any single
Server Gateway, or of any single Server Certificate compromise.
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+--------+
| |
+-----> | Server |
+-----------+ | | GW 1 | +-----------+
| Client | +---+----+ +------+-+ +--------+ | |
| Gateway | | | | | | | |
| | | Server | <--+ +---> | Server +--> | |
| Selects | | GW 2 | | | GW 4 | | DNS |
| Random | +--------+ +-+------+ +--------+ | Server |
| Server | | | | |
| Gateway | | Server | | |
| +------------> | GW 3 | | |
+-----------+ +--------+ +-----------+
Figure 9
Figure 9 illustrates a path where more than one Server Gateway is
traversed during resolution. The objective here is to disassociate
the IDENTITY of the client from the CONTENT of the query/answer. The
association is only made directly on the first Server Gateway (and
only with respect to the Client Gateway). The actual association of
the source UDP client is only done on the Client Gateway itself,
which may or may not provide further privacy. Since there is more
than one Server-Server hop, this significantly reduces the ability to
infer associations between Query/Response and Client Gateways.
It should be noted that this looks very much like TOR (The Onion
Router), applied to JSON-encoded UDP DNS traffic. There is a
proposal for DNS privacy enhancements that applies a similar
techique, directly on UDP-based DNS queries/answers. FIXME add xref
here to reference to the appropriate Internet Draft. END FIXME
+---------------+ +--------+ +--------+ +------------+ +----------+
| Client | | WWW/GW | | WWW/GW | | | | |
| Gateway | | Server | | Server | | Web Server | | |
| | | GW 3 | | GW 4 | | | | |
| Selects | +--------+ +--------+ +----------+ | | DNS |
| Among | | Gateway | | | Server |
| Most Recent | DNS traffic mingled | Server | | | |
| Web Server | with web traffic | Module +---> | |
| Gateways +---------------------> | GW 2 | | | |
+---------------+ (or encrypted) +----------+-+ +----------+
Figure 10
Figure 10 illustrates one query/response when the client is
attempting to use something similar to steganography to preserve
privacy. In this context, the privacy against passive monitoring is
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achieved by using un-blocked web servers which are also Server
Gateways. A MitM adversary cannot easily block this traffic without
blocking the entire site, or by inspecting every flow to/from the
site. A passive observer would similarly need to inspect all flows
to find the embedded, encoded DNS traffic. The DNS traffic would be
nearly indistinguishable from regular HTTP traffic.
Note that the use of TLS to protect the Client-Server traffic would
make it impossible to distinguish the DNS traffic from the other web
trafficin this situation. Combining this "tag-along" with TLS
provides both strong privacy and strong security.
5.1. Mixed Traffic Walk-Through
Suppose a client were to visit web sites "a" through "j"
sequentially, i.e. a,b,c,d,e,f,g,h,i,j. Suppose some of those were
also Server Gateways, represented by upper case (vs lower case for
web sites without Server Gateway capabilities). Thus the sequence
would be A,b,C,D,e,f,g,H,I,j. If the Client Gateway chose a Server
Gateway randomly from among the last four web sites visited, the
sequence of events after visiting A through D, would look like:
o Select Server from set {A,C,D}, look up "e". Visit "e".
o Select Server from set {C,D}, look up "f". Visit "f".
o Select Server from set {C,D}, look up "g". Visit "g".
o Select Server from set {D}, look up "h". Visit "h".
o Select Server from set {D,H}, look up "i". Visit "i".
o Select Server from set {H,I}, look up "j". Visit "j".
An observer close to the Client would see traffic within a given time
window, only to the same set of Web servers. An observer close to
any of the Web servers would only see traffic from a given client,
for a small interval of time after the first visit.
6. Security Considerations
(None per se.) Need to list considerations etc.
7. IANA Considerations
This document will eventually contain IANA-specific material.
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8. Acknowledgements
To be added later.
9. References
9.1. Normative References
[RFC1033] Lottor, M., "Domain administrators operations guide", RFC
1033, November 1987.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, April 1997.
[RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS
Specification", RFC 2181, July 1997.
[RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS
NCACHE)", RFC 2308, March 1998.
[RFC2845] Vixie, P., Gudmundsson, O., Eastlake, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, May 2000.
[RFC2930] Eastlake, D., "Secret Key Establishment for DNS (TKEY
RR)", RFC 2930, September 2000.
[RFC3425] Lawrence, D., "Obsoleting IQUERY", RFC 3425, November
2002.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC
4033, March 2005.
[RFC4034] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Resource Records for the DNS Security Extensions",
RFC 4034, March 2005.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, March 2005.
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[RFC5155] Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
Security (DNSSEC) Hashed Authenticated Denial of
Existence", RFC 5155, March 2008.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, April 2013.
9.2. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[JPF_jsondns]
"DNS over HTTP", <http://github.com/jpf/jsondns>.
[jsondns.org]
Franusic, J., "Query DNS via REST", <http://jsondns.org/>.
[fileformat.info]
Marcuse, A., "DNS in client-side JavaScript",
<http://www.fileformat.info/tool/rest/dns-json.htm>.
[restdns.net]
"REST-DNS", <http://restdns.net/>.
[bortzmeyer.org]
Bortzmeyer, S., "DNS Looking Glass",
<http://www.bortzmeyer.org/dns-lg.html>.
[draft-bortzmeyer-dns-json]
Bortzmeyer, S., "DNS in JSON",
<http://tools.ietf.org/html/draft-bortzmeyer-dns-json-01>.
[dns-lg.com]
Cambus, F., "Multilocation DNS Looking Glass",
<http://www.dns-lg.com/>.
[trigger] NLnet Labs, "Dnssec-Trigger",
<http://www.nlnetlabs.nl/projects/dnssec-trigger/>.
Appendix A. DNS Message Encoding Examples
The entire encoding of pairs of DNS messages follows. For each
pair,the first is the query, and the second is the response.
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A.1. Simple Query/Answer, No EDNS or DNS Server
Query encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 26,
"DICTIONARY" : [
"example",
"com",
""
],
"DSIZE2" : 26,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : false,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : false,
"Z" : false,
"AD" : false,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 0,
"NSCOUNT" : 0,
"ARCOUNT" : 0
],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
]
]
Response encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 33,
"DICTIONARY" : [
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"example",
"com",
"",
"@0"
],
"DSIZE2" : 33,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : true,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : true,
"Z" : false,
"AD" : false,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 1,
"NSCOUNT" : 0,
"ARCOUNT" : 0
],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Answer" : [
"RR" : [
"NAME" : [ "example.com." : 0 ],
"TYPE" : [ "A" : 1 ],
"CLASS" : [ "IN" : 1 ],
"TTL" : 5218,
"RDLENGTH" : 4,
"RDATA" : [
"A" : [
"Address" : "93.184.216.119"
]
]
]
]
]
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A.2. Simple Query/Answer, EDNS, no DNS Server
Query encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 31,
"DICTIONARY" : [
"example",
"com",
"",
""
],
"DSIZE2" : 31,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : false,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : false,
"Z" : false,
"AD" : false,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 0,
"NSCOUNT" : 0,
"ARCOUNT" : 1
],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Additional" : [
"RR" : [
"NAME" : [ "." : 3 ],
"TYPE" : [ "OPT" : 41 ],
"Field3" : [
"UDPSIZEFIELD" : [
"UDPSIZE" : 1500
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]
],
"Field4" : [
"Extended_RCode_Flags" : [
"ERCFlagbits" : [
"RCode" : 0,
"Version" : 0,
"DO" : false,
"Resv" : 0
]
]
],
"RDLENGTH" : 0,
"RDATA" : [
"OPT (RFC 6891)" : [
"TLV_LIST" : [
]
]
]
]
]
]
Response encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 38,
"DICTIONARY" : [
"example",
"com",
"",
"@0",
""
],
"DSIZE2" : 38,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : true,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : true,
"Z" : false,
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"AD" : false,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 1,
"NSCOUNT" : 0,
"ARCOUNT" : 1
],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Answer" : [
"RR" : [
"NAME" : [ "example.com." : 0 ],
"TYPE" : [ "A" : 1 ],
"CLASS" : [ "IN" : 1 ],
"TTL" : 4865,
"RDLENGTH" : 4,
"RDATA" : [
"A" : [
"Address" : "93.184.216.119"
]
]
]
],
"Additional" : [
"RR" : [
"NAME" : [ "." : 4 ],
"TYPE" : [ "OPT" : 41 ],
"Field3" : [
"UDPSIZEFIELD" : [
"UDPSIZE" : 4000
]
],
"Field4" : [
"Extended_RCode_Flags" : [
"ERCFlagbits" : [
"RCode" : 0,
"Version" : 0,
"DO" : false,
"Resv" : 0
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]
]
],
"RDLENGTH" : 0,
"RDATA" : [
"OPT (RFC 6891)" : [
"TLV_LIST" : [
]
]
]
]
]
]
A.3. Simple Query/Answer, no EDNS, with DNS Server
Query encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 31,
"DICTIONARY" : [
"example",
"com",
"",
""
],
"DSIZE2" : 31,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : false,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : false,
"Z" : false,
"AD" : false,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 0,
"NSCOUNT" : 0,
"ARCOUNT" : 1
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],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Additional" : [
"RR" : [
"NAME" : [ "." : 3 ],
"TYPE" : [ "OPT" : 41 ],
"Field3" : [
"UDPSIZEFIELD" : [
"UDPSIZE" : 1500
]
],
"Field4" : [
"Extended_RCode_Flags" : [
"ERCFlagbits" : [
"RCode" : 0,
"Version" : 0,
"DO" : false,
"Resv" : 0
]
]
],
"RDLENGTH" : 19,
"RDATA" : [
"OPT (RFC 6891)" : [
"TLV_LIST" : [
"TLV" : [
"TYPE" : [ "PrivateType65500" : 65500 ],
"Len" : 13,
"Data" : [
"PrivateType65500" : [
"GW_NAME" : [ "10:10" , "198.41.1.1" ]
]
]
],
"TLV" : [
"TYPE" : [ "PrivateType65510" : 65510 ],
"Len" : 0,
"Data" : [
]
],
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]
]
]
]
]
]
Response encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 38,
"DICTIONARY" : [
"example",
"com",
"",
"@0",
""
],
"DSIZE2" : 38,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : true,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : true,
"Z" : false,
"AD" : true,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 1,
"NSCOUNT" : 0,
"ARCOUNT" : 1
],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Answer" : [
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"RR" : [
"NAME" : [ "example.com." : 0 ],
"TYPE" : [ "A" : 1 ],
"CLASS" : [ "IN" : 1 ],
"TTL" : 4084,
"RDLENGTH" : 4,
"RDATA" : [
"A" : [
"Address" : "93.184.216.119"
]
]
]
],
"Additional" : [
"RR" : [
"NAME" : [ "." : 4 ],
"TYPE" : [ "OPT" : 41 ],
"Field3" : [
"UDPSIZEFIELD" : [
"UDPSIZE" : 512
]
],
"Field4" : [
"Extended_RCode_Flags" : [
"ERCFlagbits" : [
"RCode" : 0,
"Version" : 0,
"DO" : false,
"Resv" : 0
]
]
],
"RDLENGTH" : 19,
"RDATA" : [
"OPT (RFC 6891)" : [
"TLV_LIST" : [
"TLV" : [
"TYPE" : [ "PrivateType65500" : 65500 ],
"Len" : 13,
"Data" : [
"PrivateType65500" : [
"GW_NAME" : [ "10:10" , "198.41.1.1" ]
]
]
],
"TLV" : [
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"TYPE" : [ "PrivateType65510" : 65510 ],
"Len" : 0,
"Data" : [
]
],
]
]
]
]
]
]
A.4. Simple Query/Answer, with EDNS and DNS Server
Query encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 31,
"DICTIONARY" : [
"example",
"com",
"",
""
],
"DSIZE2" : 31,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : false,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : false,
"Z" : false,
"AD" : false,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 0,
"NSCOUNT" : 0,
"ARCOUNT" : 1
],
"Question" : [
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"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Additional" : [
"RR" : [
"NAME" : [ "." : 3 ],
"TYPE" : [ "OPT" : 41 ],
"Field3" : [
"UDPSIZEFIELD" : [
"UDPSIZE" : 1500
]
],
"Field4" : [
"Extended_RCode_Flags" : [
"ERCFlagbits" : [
"RCode" : 0,
"Version" : 0,
"DO" : false,
"Resv" : 0
]
]
],
"RDLENGTH" : 15,
"RDATA" : [
"OPT (RFC 6891)" : [
"TLV_LIST" : [
"TLV" : [
"TYPE" : [ "PrivateType65500" : 65500 ],
"Len" : 13,
"Data" : [
"PrivateType65500" : [
"GW_NAME" : [ "10:10" , "198.41.1.1" ]
]
]
],
]
]
]
]
]
]
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Response encoded in JSON:
"PACKET (RFC 1035)" : [
"ROLE" : "client",
"DSIZE" : 38,
"DICTIONARY" : [
"example",
"com",
"",
"@0",
""
],
"DSIZE2" : 38,
"Header" : [
"ID" : 42,
"HFlags" : [
"QR" : true,
"Opcode" : [ "Query" : 0 ],
"AA" : false,
"TC" : false,
"RD" : true,
"RA" : true,
"Z" : false,
"AD" : true,
"CD" : false,
"RCODE" : [ "NoError (RFC 1035)" : 0 ]
],
"QDCOUNT" : 1,
"ANCOUNT" : 1,
"NSCOUNT" : 0,
"ARCOUNT" : 1
],
"Question" : [
"QUESTION (RFC 1035)" : [
"QNAME" : [ "example.com." : 0 ],
"QTYPE" : [ "A" : 1 ],
"QCLASS" : [ "IN" : 1 ]
]
],
"Answer" : [
"RR" : [
"NAME" : [ "example.com." : 0 ],
"TYPE" : [ "A" : 1 ],
"CLASS" : [ "IN" : 1 ],
"TTL" : 4084,
"RDLENGTH" : 4,
"RDATA" : [
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"A" : [
"Address" : "93.184.216.119"
]
]
]
],
"Additional" : [
"RR" : [
"NAME" : [ "." : 4 ],
"TYPE" : [ "OPT" : 41 ],
"Field3" : [
"UDPSIZEFIELD" : [
"UDPSIZE" : 512
]
],
"Field4" : [
"Extended_RCode_Flags" : [
"ERCFlagbits" : [
"RCode" : 0,
"Version" : 0,
"DO" : false,
"Resv" : 0
]
]
],
"RDLENGTH" : 15,
"RDATA" : [
"OPT (RFC 6891)" : [
"TLV_LIST" : [
"TLV" : [
"TYPE" : [ "PrivateType65500" : 65500 ],
"Len" : 13,
"Data" : [
"PrivateType65500" : [
"GW_NAME" : [ "10:10" , "198.41.1.1" ]
]
]
],
]
]
]
]
]
]
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Appendix B. Server Gateway HTML code
The entire HTML document needed on the Server for the Client to send/
receive JSON-encoded DNS messages follows:
<html>
<body>
<form action="cgi-bin/json-resolver2.pl" method="POST">
<P>
<TEXTAREA name="query" rows="20" cols="80">
</TEXTAREA>
<INPUT type="submit" value="Send"><INPUT type="reset">
</P>
</form>
</body>
</html>
The "action" target needs to exist and be executable, and ideally be
performance-optimized (e.g. via use of mod_perl).
Appendix C. Server Gateway HTTP POST Handler Pseudo-code
The following pseudo-code illustrates the high-level behavior of the
HTML handler for the Server.
The handler is passed the contents of the TEXTAREA, which will be the
JSON-encoded DNS message.
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// initialize parser etc.
// set up socket for UDP query/response to default Resolver
// set up socket for UDP query/response to client-supplied Resolver
// extract JSON-encoded DNS message from HTTP POST variable 'query'
// save original Query-ID, assign new Query-ID (to avoid collisions)
// decode DNS message (into DNS wire format)
// if DNS message has OPT Resource Record
// if OPT has Client-supplied Resolver option
// extract Resolver value
// delete Resolver option from OPT
// endif
// if OPT was synthesized by Client
// delete OPT Resource Record
// endif
// send DNS message to Client-specified Resolver
// else
// send DNS message to default Resolver
// endif
// wait for response or timeout
// if timeout && retry-count < max-retry-count
// resend DNS message
// elsif timeout && retry-count >= max-retry-count
// send "retry-count-exceeded" via OPT (synthesized if necessary)
// else
// set DNS answer's Query-ID value to original Query-ID
// encode DNS answer
// send JSON-encoded answer to Client
// endif
Appendix D. Client Gateway Pseudo-code
The following pseudo-code illustrates the high-level behavior of the
Client.
The Client in this example is pre-configured with a single Server
Gateway's address.
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// initialize parser etc.
// set up socket for UDP query/response (Listener)
// set up HTTP connection to Server Gateway
// do an HTTP "GET" to the predefined URL of the Server HTML code
// extract HTML elements needed: handler, variable name
// loop forever:
// listen for DNS query packet
// fork (to handle this packet)
// if child
// save old DNS Query-ID, set new Query-ID
// if Use-Supplied-Resolver
// if exits OPT
// add client-supplied-resolver to OPT
// else
// synthesize OPT and add client-supplied-resolver
// endif
// endif
// encode DNS message (into JSON)
// write HTTP POST onto socket
// wait for HTTP response
// extract JSON-encoded answer from HTTP
// decode DNS answer (from JSON)
// if OPT
// if OPT.option is error condition
// drop answer and continue loop forever:
// elsif OPT synthesized
// delete OPT
// elsif OPT.option SPARTACUS-specific value
// delete option
// endif
// endif
// set answer.Query-ID to saved value
// send answer to sender
// end-of-loop
Author's Address
Brian Dickson
12047B 36th Ave NE
Seattle, wA 98125
Email: brian.peter.dickson@gmail.com
Dickson Expires April 18, 2015 [Page 34]
