Demultiplexing Streamed DNS from HTTP
draft-dkg-dprive-demux-dns-http-01
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Author | Daniel Kahn Gillmor | ||
| Last updated | 2017-05-03 | ||
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draft-dkg-dprive-demux-dns-http-01
dprive D. Gillmor
Internet-Draft ACLU
Updates: 1035, 7230, 7540 (if approved) May 03, 2017
Intended status: Informational
Expires: November 4, 2017
Demultiplexing Streamed DNS from HTTP
draft-dkg-dprive-demux-dns-http-01
Abstract
DNS over TCP and traditional HTTP are both stream-oriented, client-
speaks-first protocols. They can both be run over a stream-based
security protocol like TLS. A server accepting a stream-based client
can distinguish between a valid stream of DNS queries and valid
stream of HTTP requests by simple observation of the first few octets
sent by the client. This can be done without any external
demultiplexing mechanism like TCP port number or ALPN.
Implicit multiplexing of the two protocols over a single listening
port can be useful for obscuring the presence of DNS queries from a
network observer, which makes it relevant for DNS privacy.
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/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 4, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Distinguish only at the start of a stream . . . . . . . . . . 3
2.1. Why not ALPN? . . . . . . . . . . . . . . . . . . . . . . 4
3. Overview of initial octets . . . . . . . . . . . . . . . . . 4
3.1. DNS stream initial octets . . . . . . . . . . . . . . . . 4
3.2. HTTP initial octets . . . . . . . . . . . . . . . . . . . 5
3.2.1. HTTP/0.9 . . . . . . . . . . . . . . . . . . . . . . 6
3.2.2. HTTP/1.0 and HTTP/1.1 . . . . . . . . . . . . . . . . 6
3.2.3. HTTP/2 . . . . . . . . . . . . . . . . . . . . . . . 7
4. Specific octets . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. octets 0 and 1 . . . . . . . . . . . . . . . . . . . . . 8
4.2. octets 2 and 3 . . . . . . . . . . . . . . . . . . . . . 8
4.3. octet 4 . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4. octet 5 . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.5. octets 6 and 7 . . . . . . . . . . . . . . . . . . . . . 10
4.6. octets 8 through 11 . . . . . . . . . . . . . . . . . . . 10
4.7. octets 12 and 13 . . . . . . . . . . . . . . . . . . . . 10
5. Combinations of octets . . . . . . . . . . . . . . . . . . . 10
5.1. Proof: a valid DNS message cannot be an HTTP query . . . 11
6. Guidance for Demultiplexing Servers . . . . . . . . . . . . . 12
6.1. Without supporting HTTP/0.9 . . . . . . . . . . . . . . . 12
6.2. Supporting archaic HTTP/0.9 clients . . . . . . . . . . . 12
6.3. Signaling demultiplexing capacity . . . . . . . . . . . . 13
7. Guidance for DNS clients . . . . . . . . . . . . . . . . . . 13
7.1. Interpreting failure . . . . . . . . . . . . . . . . . . 14
8. Guidance for HTTP clients . . . . . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
12. Document Considerations . . . . . . . . . . . . . . . . . . . 16
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
13.1. Normative References . . . . . . . . . . . . . . . . . . 16
13.2. Informative References . . . . . . . . . . . . . . . . . 17
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
DNS and HTTP are both client-speaks-first protocols capable of
running over stream-based transport like TCP, or as the payload of a
typical TLS [RFC5246] session.
There are some contexts where it is useful for a server to be able to
decide what protocol is used by an incoming TCP stream, to choose
dynamically between DNS and HTTP on the basis of the stream itself
(rather than a port designation or other explicit demultiplexing).
For example, a TLS terminator listening on port 443 might be willing
to serve DNS-over-TLS [RFC7858] as well as HTTPS.
A simple demultiplexing server should do this demuxing based on the
first few bytes sent by the client on a given stream; once a choice
has been established, the rest of the stream is committed to one or
the other interpretation.
This document provides proof that a demultiplexer can robustly
distinguish HTTP from DNS on the basis of the content of the stream
alone.
A DNS client that knows it is talking to a server which is this
position (e.g. trying to do DNS-over-TLS on TCP port 443, used
traditionally only for HTTPS) might also want to be aware of network
traffic patterns that could confuse such a server. This document
presents explicit mitigations that such a DNS client MAY decide to
use.
This document limits its discussion of HTTP over TCP or TLS or some
other classical stream-based protocol (it excludes HTTP over QUIC,
for example). Likewise, it considers only the TCP variant of DNS
(and excludes DNS over UDP or any other datagram transport).
FIXME: address network stack ossification here?
2. Distinguish only at the start of a stream
A server which attempts to distinguish DNS queries from HTTP requests
individually might consider using these guidelines in the middle of a
running stream (e.g. at natural boundaries, like the end of an HTTP
request, or after a DNS message), but this document focuses
specifically on a heuristic choice for the whole stream, based on the
initial few octets sent by the client.
While it's tempting to consider distinguishing at multiple points in
the stream, the complexities of determining the specific end of an
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HTTP/1.1 request body, and the difficulty in distinguishing an HTTP/2
frame header from a streamed DNS message make this more difficult to
implement. Interleaving the responses themselves on a stream with
multiple data elements is also challenging. So do not use this
technique anywhere but at the beginning of a stream!
If being able to interleave DNS queries with HTTP requests on a
single stream is desired, a strategy like
[I-D.ietf-dnsop-dns-wireformat-http] is recommended instead.
2.1. Why not ALPN?
If this is done over TLS, a natural question is whether the client
should simply indicate its preferred protocol in the TLS handshake's
ALPN [RFC7301] extension.
However, ALPN headers are visible to a network observer, and a
network controller attempting to confine the user's DNS traffic to a
limited set of servers could use the ALPN header as a signal to block
DNS-specific streams.
3. Overview of initial octets
3.1. DNS stream initial octets
[RFC1035] section 4.2.2 ("TCP Usage") shows that every stream-based
DNS connection starts with a DNS message, preceded with a 2-octet
message length field:
The message is prefixed with a two byte length field which gives
the message length, excluding the two byte length field.
[RFC6895] section 2 represents the DNS message header section, which
is the first part of the DNS message on the wire (after the message
length).
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1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| OpCode |AA|TC|RD|RA| Z|AD|CD| RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT/ZOCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT/PRCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT/UPCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
So in a DNS over TCP stream, the interpretation of the initial 14
octets are fixed based on information about the first query sent on
the stream:
o 0,1: length of initial DNS message
o 2,3: DNS Transaction ID
o 4,5: DNS opcode, flags, and response code
o 6,7: Question count (or Zone count in UPDATE)
o 8,9: Answer count (or Prerequisite count in UPDATE)
o 10,11: Authority count (or Update count in UPDATE)
o 12,13: Additional RR count
All DNS streams sent over TCP start with at least these 14 octets.
3.2. HTTP initial octets
In an HTTP stream, the first octets sent from the client are either
the so-called "Simple-Request" (for HTTP/0.9), the "Request-Line"
(for HTTP/1.0 and HTTP/1.1), which has variable characteristics, or
the "connection preface" (for HTTP/2) which is a fixed string.
Some servers may wish to ignore the oldest of these, HTTP/0.9.
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3.2.1. HTTP/0.9
[RFC1945] section 4.1 says that HTTP/0.9 queries (that is, HTTP
queries from before HTTP/1.0 was formalized) use this form:
Simple-Request = "GET" SP Request-URI CRLF
Note that HTTP/0.9 clients send this string and only this string,
nothing else (no request body, no subsequent requests). The
"Request-URI" token is guaranteed to start with a printable ASCII
character, and cannot contain any members of the CTL class (values
0x00 through 0x1F) but due to loose early specifications, it might
sometimes contain high-valued octets (those with the most-significant
bit set - 0x80 or above).
So the first 5 octets are all constrained to be no less than 0x20
(SP) and no more than 0x7F (DEL), and all subsequent octets sent from
the client have a value at least 0x0A (LF).
The shortest possible HTTP/0.9 client request is:
char: G E T SP / CR LF
index: 0 1 2 3 4 5 6
The lowest possible HTTP/0.9 client request (sorted ASCIIbetically)
is:
char: G E T SP + : CR LF
index: 0 1 2 3 4 5 6 7
3.2.2. HTTP/1.0 and HTTP/1.1
The request line format for HTTP/1.1 matches that of HTTP/1.0
(HTTP/1.1 adds protocol features like pipelining, but doesn't change
the request form itself). But unlike HTTP/0.9, the initial verb (the
"method") can vary.
[RFC7230] section 3.1.1 says that the first line of an HTTP/1.1
request is:
request-line = method SP request-target SP HTTP-version CRLF
method = token
and [RFC7230] section 3.2.6 says:
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token = 1*tchar
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
/ "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
/ DIGIT / ALPHA
; any VCHAR, except delimiters
and VCHAR is defined in [RFC5234] appendix B.1 as:
VCHAR = %x21-7E
"request-target" itself cannot contain 0x20 (SP) or any CTL
characters, or any characters above the US-ASCII range (> 0x7F).
And the "HTTP-version" token is either the literal string "HTTP/1.0"
or the literal string "HTTP/1.1", both of which are constrained to
the same printable-ASCII range.
The ASCIIbetically-lowest shortest possible HTTP/1.0 or HTTP/1.1
request is:
char: ! SP / SP H T T P / 1 . 0 CR LF CR LF
index: 0 1 2 3 4 5 6 7 8 9 0 a b c d e
In any case, no HTTP/1.0 or HTTP/1.1 request line can include any
values lower than 0x0A (LF) or greater than 0x7F (DEL) in the first
15 octets.
However, [RFC7230] section 3.1.1 also says:
In the interest of robustness, a server that is expecting to receive
and parse a request-line SHOULD ignore at least one empty line (CRLF)
received prior to the request-line.
So we should also consider accepting an arbitrary number of repeated
CRLF sequences before the request-line as a potentially-valid HTTP
client behavior.
3.2.3. HTTP/2
[RFC7540] section 3.5 says:
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In HTTP/2, each endpoint is required to send a connection preface as
a final confirmation of the protocol in use and to establish the
initial settings for the HTTP/2 connection. The client and server
each send a different connection preface.
The client connection preface starts with a sequence of 24 octets,
which in hex notation is:
0x505249202a20485454502f322e300d0a0d0a534d0d0a0d0a
That is, the connection preface starts with the string "PRI *
HTTP/2.0\r\n\r\nSM\r\n\r\n").
The highest valued octet here is 0x54 ("T"), and the lowest is 0x0A
(LF).
4. Specific octets
The sections below examine likely values of specific octet positions
in the stream. All octet indexes are 0-based.
4.1. octets 0 and 1
Any DNS message less than 3338 octets sent as the initial query over
TCP can be reliably distinguished from any version of HTTP by the
first two octets of the TCP stream alone.
3338 is 0x0D0A, or the ASCII string CRLF, which some HTTP clients
might send before an initial request. No HTTP client can
legitimately send anything lower than this.
Most DNS queries are easily within this range automatically.
4.2. octets 2 and 3
In a DNS stream, octets 2 and 3 represent the client-chosen message
ID. The message ID is used to bind messages with responses. Over
connectionless transports like UDP, this is an important anti-
spoofing measure, as well as a distinguishing measure for clients
reusing the same UDP port for multiple outstanding queries. Standard
DNS clients already explicitly randomize this value.
For the connection-oriented streaming DNS discussed here, the anti-
spoofing characteristics are not relevant (the connection itself
provides anti-spoofing), so the client is free to choose arbitrary
values.
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With a standard DNS client which fully-randomizes these values, only
25% of generated queries will have the high bits of both octets set
to 0. 100% of all HTTP requests will have the high bits of both of
these octets cleared. Similarly, some small percentage of randomly-
generated DNS queries will have values here lower than 0x0A, while no
HTTP clients will ever send these low values.
4.3. octet 4
In a DNS stream, octet 4 combines several fields:
0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|
+--+--+--+--+--+--+--+--+
In a standard DNS query sent over a streaming interface, QR, Opcode,
AA, and TC are all set to 0. The least-significant bit (RD -
Recursion Desired) is set when a packet is sent from a stub to a
recursive resolver. The value of such an octet is 0x01. This value
never occurs in octet 4 of a legitimate HTTP client.
But under DNS UPDATE ([RFC2136], Opcode is set to 5 and all the
option bits are cleared, which means this value would have 0x40
(ASCII '@'), which could legitimately occur in some HTTP requests at
this position..
4.4. octet 5
In a DNS stream, octet 5 also combines several fields:
0 1 2 3 4 5 6 7
+--+--+--+--+--+--+--+--+
|RA| Z|AD|CD| RCODE |
+--+--+--+--+--+--+--+--+
In some DNS messages sent from a client, all these bits are 0.
However, section 5.7 of [RFC6840] suggests that queries may wish to
set the AD bit to indicate a desire to learn from a validating
resolver whether the resolver considers the contents to be Authentic
Data.
[RFC6840] also suggests that:
validating resolvers SHOULD set the CD bit on every upstream query.
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So many queries, particularly from DNSSEC-validating DNS clients, are
likely to set bits 2 and 3, resulting in a value 0x30 (ASCII '0').
This is usually a legitimate value for octet 5 in an HTTP request.
4.5. octets 6 and 7
In DNS, octets 6 and 7 represent the query count. Most DNS clients
will send one query at a time, which makes this value 0x0001. As
long as the number of initial queries does not exceed 0x0A0A (2570),
then at least one of these octets will have a value less than 0x0A.
No HTTP client sends an octet less than 0x0A in positions 6 or 7.
In DNS UPDATE, octets 6 and 7 represent the zone count. Entries in
the Zone section of the DNS UPDATE message are structured identically
to entries in the Query section of a standard DNS message.
4.6. octets 8 through 11
In streaming DNS, octets 8 through 11 represent answer counts and
authority counts in normal DNS queries, or Prerequisite and Update
counts in DNS UPDATE. Standard DNS queries will set them both 0.
DNS UPDATE queries are likely to include some records in these
sections, so they won't be all zero, but as long as no more than 2570
Prerequisite records and no more than 2570 Update records are sent,
at least one octet will have value less than 0x0A. But No HTTP
client sends an octet less tan 0x0A in these positions.
4.7. octets 12 and 13
In streaming DNS, octets 12 and 13 represent the number of Additional
RRs. When a DNS query is sent with EDNS(0), the OPT RR is accounted
for here. So this is often either 0x0000 or 0x0001. In a Secure DNS
UPDATE [RFC3007], the SIG(0) or TSIG record is also found in this
section, which could increase the values of these octets to 0x0002.
No HTTP client will send octets with these low values at these
positions.
5. Combinations of octets
In a DNS message, each Question in the Question section (or Zone in
the Zone section for DNS UPDATE) is at least 5 octets (1 octet for
zero-length QNAME + 2 octets for QTYPE + 2 octets for QCLASS), and
each RR (in the Answer, Authority, and Additional sections for normal
DNS queries; or in the Prerequisite, Update, and Additional sections
for DNS UPDATE) is at least 11 octets. And the header itself is 12
octets.
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So we know that for a valid DNS stream, the first message has a size
of at least:
min_first_msg_size = 12 + 5 * (256*o[6] + o[7]) +
11 * (256*(o[8] + o[10] + o[12]) +
o[9] + o[11] + o[13])
It's possible to compare this value with the expected first query
size:
first_msg_size = 256 * o[0] + o[1]
if "first_query_size" is less than "min_first_query_size" we can be
confident that the stream is not DNS.
5.1. Proof: a valid DNS message cannot be an HTTP query
For any a valid, stream-based DNS message:
o If there are fewer than 0x0A00 Questions then octet 6 < 0x0A.
o If there are fewer than 0x0A00 Answer RRs, then octet 8 < 0x0A.
o If there are fewer than 0x0A00 Authority RRs, then octet 10 <
0x0A.
o If there are fewer than 0x0A00 Additional RRs, then octet 12 <
0x0A.
If any of these four inequalities hold, then the packet is clearly
DNS, not HTTP.
if none of them hold, then there are at least 0x0A00 (2560) Questions
and 3*2560 == 7680 RRs. But:
12 + 5*2560 + 11*7680 == 97292
So the smallest possible DNS message where none of these four
inequalites hold is 97292 octets. But a DNS message is limited in
size to 65535 octets.
Therefore at least one of these inequalities holds, and one of the
first 14 octets of a DNS steam is < 0x0A.
But in a standard HTTP request, none of the first 14 octets can have
a value < 0x0A, so a valid DNS message cannot be mistaken for an HTTP
request.
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6. Guidance for Demultiplexing Servers
Upon receiving a connection stream that might be either DNS or HTTP,
a server can inspect the initial octets of the stream to decide where
to send it.
6.1. Without supporting HTTP/0.9
A server that doesn't care about HTTP/0.9 can simply wait for the
first 14 octets of the client's request to come in. Then the
algorithm is:
bytestream = read_from_client(14)
for x in bytestream:
if (x < 0x0A) or (x > 0x7F):
return `DNS`
return `HTTP`
6.2. Supporting archaic HTTP/0.9 clients
A server that decides to try to support HTTP/0.9 clients has a
slightly more challenging task, since some of them may send fewer
octets than the initial DNS message, and the server shouldn't block
waiting for data that will never come.
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bytestream = read_from_client(5)
for x in bytestream[0:5]
if (x < 0x0A) or (x > 0x7F):
return `DNS`
if (bytestream[0:4] != 'GET '): # not HTTP/0.9
bytestream += read_from_client(9)
for x in bytestream[5:14]:
if (x < 0x0A) or (x > 0x7f):
return `DNS`
return `HTTP`
else: # maybe HTTP/0.9
seen_sp = False
seen_high = False
while (len(bytestream) < 14):
if (seen_sp and seen_high):
return `DNS`
x = read_from_client(1)
bytestream += x
if (x > 0x7F):
seen_high = True
elif (x < 0x0A):
return `DNS`
elif (x == 0x20):
seen_sp = True # SP found before CRLF, not HTTP/0.9
elif (x == 0x0A):
return `HTTP`
return `HTTP`
Note that if read_from_client() ever fails to read the number of
requested bytes (e.g. because of EOF), then the stream is neither
valid HTTP nor valid DNS, and can be discarded.
6.3. Signaling demultiplexing capacity
FIXME: should there be a way for a listener to signal somehow that it
is willing and capable of handling both DNS and HTTP traffic? There
would need to be a different signaling mechanism for each stream
(unless the signalling is done somehow in an outer layer like TLS).
This is probably out-of-scope for this draft.
7. Guidance for DNS clients
Consider a DNS client that connects to a server that might be
interested in answering HTTP requests on the same address/port (or
other channel identifier). The client wants to send traffic that is
unambiguously DNS traffic to make it easy for the server to
distinguish it from inbound HTTP requests. Fortunately, this is
trivial to do.
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Such a client should follow these guidelines:
o Send the DNS message size (a 16-bit integer) together in the same
packet with the full header of the first DNS message so that the
recipient can review as much as possible of the frame at once.
This is a best practice for efficient stream-based DNS anyway.
If the client is concerned about stream fragmentation that it cannot
control, and it is talking to a server that might be expecting
HTTP/0.9 clients, then the server might not be willing to wait for
the full initial 14 octets to make a decision.
Note that this fragmentation is not a concern for streams wrapped in
TLS when using modern AEAD ciphersuites. In this case, the client
gets to choose the size of the plaintext record, which is either
recovered by the server in full (unfragmented) or the connection
fails.
If the client does not have such a guarantee from the transport, it
MAY also take one of the following mitigating actions relating to the
first DNS message it sends in the stream [explanation of what the
server gets to see in the fragmented stream case are in square
brackets after each mitigation]:
o Ensure the first message is marked as a query (QR = 0), and it
uses opcode 0 ("Standard Query"). [bytestream[4] < 0x08]
o Ensure that the first message has RA = 0, Z = 0, and RCODE = 0.
[bytestream[5] == 0x00]
o Ensure that the high bit of the first octet of the message ID of
the first message is set. [bytesteam[2] > 0x7F]
o Send an initial short Server Status DNS message ahead of the
otherwise intended initial DNS message. [bytstream[0] == 0x00]
o Use the EDNS(0) padding option [RFC7830] to pad the first message
to a multiple of 256 octets. [bytestream[1] == 0x00]
7.1. Interpreting failure
FIXME: A DNS client that does not already know that a server is
willing to carry both types of traffic SHOULD expect a transport
connection failure of some sort. Can we say something specific about
what it should expect?
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8. Guidance for HTTP clients
HTTP clients SHOULD NOT send HTTP/0.9 requests, since modern HTTP
servers are not required to support HTTP/0.9. Sending an HTTP/1.0
request (or any later version) is sufficient for a server to be able
to distinguish the two protocols.
9. Security Considerations
FIXME: Clients should locally validate DNSSEC (servers may still be
able to omit some records)
FIXME: if widely deployed, consider amplification for DDoS against
authoritative servers?
FIXME: consider dnssec transparency
FIXME: consider TLS session resumption - this counts as a new stream
boundary, so the multiplexing decision need not persist across
resumption.
FIXME: consider 0-RTT
FIXME: consider X.509 cert validation
FIXME: what other security considerations should clients take?
FIXME: what other security considerations should servers take?
10. Privacy Considerations
FIXME: DNS queries and HTTP requests can reveal potentially sensitive
information about the sender.
FIXME: consider DNS and HTTP traffic analysis - how should requests
or responses be padded, aggregated, or delayed given that streams are
multiplexed?
FIXME: any other privacy considerations?
11. IANA Considerations
This document does not ask IANA to make any changes to existing
registries.
However, it does update the DNS and HTTP specifications, to reflect
the fact that services using this demultiplexing technique may be
constrained in adoption of future versions of either DNS or HTTP if
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those future versions modify either protocol in a way that breaks
with the distinctions documented here.
Future revisions of or extensions to stream-based DNS or HTTP should
take this demultiplexing technique into consideration.
12. Document Considerations
[ RFC Editor: please remove this section before publication ]
This document is currently edited as markdown. Minor editorial
changes can be suggested via merge requests at
https://gitlab.com/dkg/hddemux or by e-mail to the author. Please
direct all significant commentary to the public IETF DNS Privacy
mailing list: dns-privacy@ietf.org or to the IETF HTTP WG mailing
list: ietf-http-wg@w3.org
13. References
13.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Frystyk, "Hypertext
Transfer Protocol -- HTTP/1.0", RFC 1945,
DOI 10.17487/RFC1945, May 1996,
<http://www.rfc-editor.org/info/rfc1945>.
[RFC2136] Vixie, P., Ed., Thomson, S., Rekhter, Y., and J. Bound,
"Dynamic Updates in the Domain Name System (DNS UPDATE)",
RFC 2136, DOI 10.17487/RFC2136, April 1997,
<http://www.rfc-editor.org/info/rfc2136>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<http://www.rfc-editor.org/info/rfc5234>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.
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[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.
13.2. Informative References
[I-D.ietf-dnsop-dns-wireformat-http]
Song, L., Vixie, P., Kerr, S., and R. Wan, "DNS wire-
format over HTTP", draft-ietf-dnsop-dns-wireformat-http-01
(work in progress), March 2017.
[RFC3007] Wellington, B., "Secure Domain Name System (DNS) Dynamic
Update", RFC 3007, DOI 10.17487/RFC3007, November 2000,
<http://www.rfc-editor.org/info/rfc3007>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC6840] Weiler, S., Ed. and D. Blacka, Ed., "Clarifications and
Implementation Notes for DNS Security (DNSSEC)", RFC 6840,
DOI 10.17487/RFC6840, February 2013,
<http://www.rfc-editor.org/info/rfc6840>.
[RFC6895] Eastlake 3rd, D., "Domain Name System (DNS) IANA
Considerations", BCP 42, RFC 6895, DOI 10.17487/RFC6895,
April 2013, <http://www.rfc-editor.org/info/rfc6895>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <http://www.rfc-editor.org/info/rfc7301>.
[RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830,
DOI 10.17487/RFC7830, May 2016,
<http://www.rfc-editor.org/info/rfc7830>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <http://www.rfc-editor.org/info/rfc7858>.
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Author's Address
Daniel Kahn Gillmor
American Civil Liberties Union
125 Broad St.
New York, NY 10004
USA
Email: dkg@fifthhorseman.net
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