QUIC-LB: Generating Routable QUIC Connection IDs
draft-ietf-quic-load-balancers-14
The information below is for an old version of the document.
| Document | Type |
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|---|---|---|---|
| Authors | Martin Duke , Nick Banks , Christian Huitema | ||
| Last updated | 2022-07-11 (Latest revision 2022-03-28) | ||
| Replaces | draft-duke-quic-load-balancers | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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draft-ietf-quic-load-balancers-14
QUIC M. Duke
Internet-Draft Google
Intended status: Standards Track N. Banks
Expires: 12 January 2023 Microsoft
C. Huitema
Private Octopus Inc.
11 July 2022
QUIC-LB: Generating Routable QUIC Connection IDs
draft-ietf-quic-load-balancers-14
Abstract
QUIC address migration allows clients to change their IP address
while maintaining connection state. To reduce the ability of an
observer to link two IP addresses, clients and servers use new
connection IDs when they communicate via different client addresses.
This poses a problem for traditional "layer-4" load balancers that
route packets via the IP address and port 4-tuple. This
specification provides a standardized means of securely encoding
routing information in the server's connection IDs so that a properly
configured load balancer can route packets with migrated addresses
correctly. As it proposes a structured connection ID format, it also
provides a means of connection IDs self-encoding their length to aid
some hardware offloads.
Note to Readers
Discussion of this document takes place on the QUIC Working Group
mailing list (quic@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/quic/
(https://mailarchive.ietf.org/arch/browse/quic/).
Source for this draft and an issue tracker can be found at
https://github.com/quicwg/load-balancers (https://github.com/quicwg/
load-balancers).
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 https://datatracker.ietf.org/drafts/current/.
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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 12 January 2023.
Copyright Notice
Copyright (c) 2022 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 (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
1.2. Notation . . . . . . . . . . . . . . . . . . . . . . . . 5
2. First CID octet . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Config Rotation . . . . . . . . . . . . . . . . . . . . . 6
2.2. Configuration Failover . . . . . . . . . . . . . . . . . 7
2.3. Length Self-Description . . . . . . . . . . . . . . . . . 7
2.4. Format . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Load Balancing Preliminaries . . . . . . . . . . . . . . . . 8
3.1. Unroutable Connection IDs . . . . . . . . . . . . . . . . 9
3.2. Fallback Algorithms . . . . . . . . . . . . . . . . . . . 10
3.3. Server ID Allocation . . . . . . . . . . . . . . . . . . 10
4. Server ID Encoding in Connection IDs . . . . . . . . . . . . 11
4.1. CID format . . . . . . . . . . . . . . . . . . . . . . . 11
4.2. Configuration Agent Actions . . . . . . . . . . . . . . . 11
4.3. Server Actions . . . . . . . . . . . . . . . . . . . . . 12
4.3.1. Special Case: Single Pass Encryption . . . . . . . . 12
4.3.2. General Case: Four-Pass Encryption . . . . . . . . . 12
4.4. Load Balancer Actions . . . . . . . . . . . . . . . . . . 15
4.4.1. Special Case: Single Pass Encryption . . . . . . . . 16
4.4.2. General Case: Four-Pass Encryption . . . . . . . . . 16
5. Per-connection state . . . . . . . . . . . . . . . . . . . . 16
6. Additional Use Cases . . . . . . . . . . . . . . . . . . . . 17
6.1. Load balancer chains . . . . . . . . . . . . . . . . . . 17
6.2. Server Process Demultiplexing . . . . . . . . . . . . . . 18
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6.3. Moving connections between servers . . . . . . . . . . . 18
7. Version Invariance of QUIC-LB . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 20
8.1. Attackers not between the load balancer and server . . . 20
8.2. Attackers between the load balancer and server . . . . . 21
8.3. Multiple Configuration IDs . . . . . . . . . . . . . . . 21
8.4. Limited configuration scope . . . . . . . . . . . . . . . 21
8.5. Stateless Reset Oracle . . . . . . . . . . . . . . . . . 22
8.6. Connection ID Entropy . . . . . . . . . . . . . . . . . . 22
8.7. Distinguishing Attacks . . . . . . . . . . . . . . . . . 23
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
10.1. Normative References . . . . . . . . . . . . . . . . . . 24
10.2. Informative References . . . . . . . . . . . . . . . . . 24
Appendix A. QUIC-LB YANG Model . . . . . . . . . . . . . . . . . 26
A.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 31
Appendix B. Load Balancer Test Vectors . . . . . . . . . . . . . 32
B.1. Unencrypted CIDs . . . . . . . . . . . . . . . . . . . . 32
B.2. Encrypted CIDs . . . . . . . . . . . . . . . . . . . . . 32
Appendix C. Interoperability with DTLS over UDP . . . . . . . . 33
C.1. DTLS 1.0 and 1.2 . . . . . . . . . . . . . . . . . . . . 33
C.2. DTLS 1.3 . . . . . . . . . . . . . . . . . . . . . . . . 34
C.3. Future Versions of DTLS . . . . . . . . . . . . . . . . . 35
Appendix D. Acknowledgments . . . . . . . . . . . . . . . . . . 35
Appendix E. Change Log . . . . . . . . . . . . . . . . . . . . . 35
E.1. since draft-ietf-quic-load-balancers-13 . . . . . . . . . 35
E.2. since draft-ietf-quic-load-balancers-12 . . . . . . . . . 35
E.3. since draft-ietf-quic-load-balancers-11 . . . . . . . . . 35
E.4. since draft-ietf-quic-load-balancers-10 . . . . . . . . . 35
E.5. since draft-ietf-quic-load-balancers-09 . . . . . . . . . 36
E.6. since draft-ietf-quic-load-balancers-08 . . . . . . . . . 36
E.7. since draft-ietf-quic-load-balancers-07 . . . . . . . . . 36
E.8. since draft-ietf-quic-load-balancers-06 . . . . . . . . . 36
E.9. since draft-ietf-quic-load-balancers-05 . . . . . . . . . 36
E.10. since draft-ietf-quic-load-balancers-04 . . . . . . . . . 37
E.11. since-draft-ietf-quic-load-balancers-03 . . . . . . . . . 37
E.12. since-draft-ietf-quic-load-balancers-02 . . . . . . . . . 37
E.13. since-draft-ietf-quic-load-balancers-01 . . . . . . . . . 37
E.14. since-draft-ietf-quic-load-balancers-00 . . . . . . . . . 38
E.15. Since draft-duke-quic-load-balancers-06 . . . . . . . . . 38
E.16. Since draft-duke-quic-load-balancers-05 . . . . . . . . . 38
E.17. Since draft-duke-quic-load-balancers-04 . . . . . . . . . 38
E.18. Since draft-duke-quic-load-balancers-03 . . . . . . . . . 38
E.19. Since draft-duke-quic-load-balancers-02 . . . . . . . . . 38
E.20. Since draft-duke-quic-load-balancers-01 . . . . . . . . . 39
E.21. Since draft-duke-quic-load-balancers-00 . . . . . . . . . 39
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 39
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1. Introduction
QUIC packets [RFC9000] usually contain a connection ID to allow
endpoints to associate packets with different address/port 4-tuples
to the same connection context. This feature makes connections
robust in the event of NAT rebinding. QUIC endpoints usually
designate the connection ID which peers use to address packets.
Server-generated connection IDs create a potential need for out-of-
band communication to support QUIC.
QUIC allows servers (or load balancers) to designate an initial
connection ID to encode useful routing information for load
balancers. It also encourages servers, in packets protected by
cryptography, to provide additional connection IDs to the client.
This allows clients that know they are going to change IP address or
port to use a separate connection ID on the new path, thus reducing
linkability as clients move through the world.
There is a tension between the requirements to provide routing
information and mitigate linkability. Ultimately, because new
connection IDs are in protected packets, they must be generated at
the server if the load balancer does not have access to the
connection keys. However, it is the load balancer that has the
context necessary to generate a connection ID that encodes useful
routing information. In the absence of any shared state between load
balancer and server, the load balancer must maintain a relatively
expensive table of server-generated connection IDs, and will not
route packets correctly if they use a connection ID that was
originally communicated in a protected NEW_CONNECTION_ID frame.
This specification provides common algorithms for encoding the server
mapping in a connection ID given some shared parameters. The mapping
is generally only discoverable by observers that have the parameters,
preserving unlinkability as much as possible.
As this document proposes a structured QUIC Connection ID, it also
proposes a system for self-encoding connection ID length in all
packets, so that crypto offload can efficiently obtain key
information.
While this document describes a small set of configuration parameters
to make the server mapping intelligible, the means of distributing
these parameters between load balancers, servers, and other trusted
intermediaries is out of its scope. There are numerous well-known
infrastructures for distribution of configuration.
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1.1. Terminology
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 RFC 2119 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying significance described in RFC 2119.
In this document, "client" and "server" refer to the endpoints of a
QUIC connection unless otherwise indicated. A "load balancer" is an
intermediary for that connection that does not possess QUIC
connection keys, but it may rewrite IP addresses or conduct other IP
or UDP processing. A "configuration agent" is the entity that
determines the QUIC-LB configuration parameters for the network and
leverages some system to distribute that configuration.
Note that stateful load balancers that act as proxies, by terminating
a QUIC connection with the client and then retrieving data from the
server using QUIC or another protocol, are treated as a server with
respect to this specification.
For brevity, "Connection ID" will often be abbreviated as "CID".
1.2. Notation
All wire formats will be depicted using the notation defined in
Section 1.3 of [RFC9000]. There is one addition: the function len()
refers to the length of a field which can serve as a limit on a
different field, so that the lengths of two fields can be concisely
defined as limited to a sum, for example:
x(A..B) y(C..B-len(x))
indicates that x can be of any length between A and B, and y can be
of any length between C and B provided that (len(x) + len(y)) does
not exceed B.
The example below illustrates the basic framework:
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Example Structure {
One-bit Field (1),
7-bit Field with Fixed Value (7) = 61,
Field with Variable-Length Integer (i),
Arbitrary-Length Field (..),
Variable-Length Field (8..24),
Variable-Length Field with Dynamic Limit
(8..24-len(Variable-Length Field)),
Field With Minimum Length (16..),
Field With Maximum Length (..128),
[Optional Field (64)],
Repeated Field (8) ...,
}
Figure 1: Example Format
2. First CID octet
The first octet of a Connection ID is reserved for two special
purposes, one mandatory (config rotation) and one optional (length
self-description).
Subsequent sections of this document refer to the contents of this
octet as the "first octet."
2.1. Config Rotation
The first two bits of any connection ID MUST encode an identifier for
the configuration that the connection ID uses. This enables
incremental deployment of new QUIC-LB settings (e.g., keys).
When new configuration is distributed to servers, there will be a
transition period when connection IDs reflecting old and new
configuration coexist in the network. The rotation bits allow load
balancers to apply the correct routing algorithm and parameters to
incoming packets.
Configuration Agents SHOULD deliver new configurations to load
balancers before doing so to servers, so that load balancers are
ready to process CIDs using the new parameters when they arrive.
A Configuration Agent SHOULD NOT use a codepoint to represent a new
configuration until it takes precautions to make sure that all
connections using CIDs with an old configuration at that codepoint
have closed or transitioned.
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Servers MUST NOT generate new connection IDs using an old
configuration after receiving a new one from the configuration agent.
Servers MUST send NEW_CONNECTION_ID frames that provide CIDs using
the new configuration, and retire CIDs using the old configuration
using the "Retire Prior To" field of that frame.
It also possible to use these bits for more long-lived distinction of
different configurations, but this has privacy implications (see
Section 8.3).
2.2. Configuration Failover
If a server has not received a valid QUIC-LB configuration, and
believes that low-state, Connection-ID aware load balancers are in
the path, it SHOULD generate connection IDs with the config rotation
bits set to 0b11 and SHOULD use the "disable_active_migration"
transport parameter in all new QUIC connections. It SHOULD NOT send
NEW_CONNECTION_ID frames with new values.
A load balancer that sees a connection ID with config rotation bits
set to 0b11 MUST route using an algorithm based solely on the
address/port 4-tuple, which is consistent well beyond the QUIC
handshake. However, a load balancer MAY observe the connection IDs
used during the handshake and populate a connection ID table that
allows the connection to survive a NAT rebinding, and reduces the
probability of connection failure due to a change in the number of
servers.
When using codepoint 0b11, all bytes but the first SHOULD have no
larger of a chance of collision as random bytes. The connection ID
SHOULD be of at least length 8 to provide 7 bytes of entropy after
the first octet with a low chance of collision. Furthermore, servers
in a pool SHOULD also use a consistent connection ID length to
simplify the load balancer's extraction of a connection ID from short
headers.
2.3. Length Self-Description
Local hardware cryptographic offload devices may accelerate QUIC
servers by receiving keys from the QUIC implementation indexed to the
connection ID. However, on physical devices operating multiple QUIC
servers, it is impractical to efficiently lookup these keys if the
connection ID does not self-encode its own length.
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Note that this is a function of particular server devices and is
irrelevant to load balancers. As such, load balancers MAY omit this
from their configuration. However, the remaining 6 bits in the first
octet of the Connection ID are reserved to express the length of the
following connection ID, not including the first octet.
A server not using this functionality SHOULD make the six bits appear
to be random.
2.4. Format
First Octet {
Config Rotation (2),
CID Len or Random Bits (6),
}
Figure 2: First Octet Format
The first octet has the following fields:
Config Rotation: Indicates the configuration used to interpret the
CID.
CID Len or Random Bits: Length Self-Description (if applicable), or
random bits otherwise. Encodes the length of the Connection ID
following the First Octet.
3. Load Balancing Preliminaries
In QUIC-LB, load balancers do not generate individual connection IDs
for servers. Instead, they communicate the parameters of an
algorithm to generate routable connection IDs.
The algorithms differ in the complexity of configuration at both load
balancer and server. Increasing complexity improves obfuscation of
the server mapping.
This section describes three participants: the configuration agent,
the load balancer, and the server. For any given QUIC-LB
configuration that enables connection-ID-aware load balancing, there
must be a choice of (1) routing algorithm, (2) server ID allocation
strategy, and (3) algorithm parameters.
Fundamentally, servers generate connection IDs that encode their
server ID. Load balancers decode the server ID from the CID in
incoming packets to route to the correct server.
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There are situations where a server pool might be operating two or
more routing algorithms or parameter sets simultaneously. The load
balancer uses the first two bits of the connection ID to multiplex
incoming DCIDs over these schemes (see Section 2.1).
3.1. Unroutable Connection IDs
QUIC-LB servers will generate Connection IDs that are decodable to
extract a server ID in accordance with a specified algorithm and
parameters. However, QUIC often uses client-generated Connection IDs
prior to receiving a packet from the server.
These client-generated CIDs might not conform to the expectations of
the routing algorithm and therefore not be routable by the load
balancer. Those that are not routable are "unroutable DCIDs" and
receive similar treatment regardless of why they're unroutable:
* The config rotation bits (Section 2.1) may not correspond to an
active configuration. Note: a packet with a DCID with config ID
codepoint 0b11 (see Section 2.2) is always routable.
* The DCID might not be long enough for the decoder to process.
* The extracted server mapping might not correspond to an active
server.
All other DCIDs are routable.
Load balancers MUST forward packets with routable DCIDs to a server
in accordance with the chosen routing algorithm. Exception: if the
load balancer can parse the QUIC packet and makes a routing decision
depending on the contents (e.g., the SNI in a TLS client hello), it
MAY route in accordance with this instead. However, load balancers
MUST always route long header packets it cannot parse in accordance
with the DCID (see Section 7).
Load balancers SHOULD drop short header packets with unroutable
DCIDs.
When forwarding a packet with a long header and unroutable DCID, load
balancers MUST use a fallback algorithm as specified in Section 3.2.
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Load balancers MAY drop packets with long headers and unroutable
DCIDs if and only if it knows that the encoded QUIC version does not
allow an unroutable DCID in a packet with that signature. For
example, a load balancer can safely drop a QUIC version 1 Handshake
packet with an unroutable DCID, as a version 1 Handshake packet sent
to a QUIC-LB routable server will always have a server-generated
routable CID. The prohibition against dropping packets with long
headers remains for unknown QUIC versions.
Furthermore, while the load balancer function MUST NOT drop packets,
the device might implement other security policies, outside the scope
of this specification, that might force a drop.
Servers that receive packets with unroutable CIDs MUST use the
available mechanisms to induce the client to use a routable CID in
future packets. In QUIC version 1, this requires using a routable
CID in the Source CID field of server-generated long headers.
3.2. Fallback Algorithms
There are conditions described below where a load balancer routes a
packet using a "fallback algorithm." It can choose any algorithm,
without coordination with the servers, but the algorithm SHOULD be
deterministic over short time scales so that related packets go to
the same server. The design of this algorithm SHOULD consider the
version-invariant properties of QUIC described in [RFC8999] to
maximize its robustness to future versions of QUIC.
A fallback algorithm MUST NOT make the routing behavior dependent on
any bits in the first octet of the QUIC packet header, except the
first bit, which indicates a long header. All other bits are QUIC
version-dependent and intermediaries SHOULD NOT base their design on
version-specific templates.
For example, one fallback algorithm might convert a unroutable DCID
to an integer and divided by the number of servers, with the modulus
used to forward the packet. The number of servers is usually
consistent on the time scale of a QUIC connection handshake. Another
might simply hash the address/port 4-tuple. See also Section 7.
3.3. Server ID Allocation
Load Balancer configurations include a mapping of server IDs to
forwarding addresses. The corresponding server configurations
contain one or more unique server IDs.
The configuration agent chooses a server ID length for each
configuration that MUST be at least one octet.
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A QUIC-LB configuration MAY significantly over-provision the server
ID space (i.e., provide far more codepoints than there are servers)
to increase the probability that a randomly generated Destination
Connection ID is unroutable.
The configuration agent SHOULD provide a means for servers to express
the number of server IDs it can usefully employ, because a single
routing address actually corresponds to multiple server entities (see
Section 6.1).
Conceptually, each configuration has its own set of server ID
allocations, though two static configurations with identical server
ID lengths MAY use a common allocation between them.
A server encodes one of its assigned server IDs in any CID it
generates using the relevant configuration.
4. Server ID Encoding in Connection IDs
4.1. CID format
All connection IDs use the following format:
QUIC-LB Connection ID {
First Octet (8),
Server ID (8..152-len(Nonce)),
Nonce (32..152-len(Server ID)),
}
Figure 3: CID Format
4.2. Configuration Agent Actions
The configuration agent assigns a server ID to every server in its
pool in accordance with Section 3.3, and determines a server ID
length (in octets) sufficiently large to encode all server IDs,
including potential future servers.
Each configuration specifies the length of the Server ID and Nonce
fields, with limits defined for each algorithm.
Optionally, it also defines a 16-octet key. Note that failure to
define a key means that observers can determine the assigned server
of any connection, significantly increasing the linkability of QUIC
address migration.
The nonce length MUST be at least 4 octets. The server ID length
MUST be at least 1 octet.
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As QUIC version 1 limits connection IDs to 20 octets, the server ID
and nonce lengths MUST sum to 19 octets or less.
4.3. Server Actions
The server writes the first octet and its server ID into their
respective fields.
If there is no key in the configuration, the server MUST fill the
Nonce field with bytes that appear to be random. If there is a key,
the server fills the nonce field with a nonce of its choosing. See
Section 8.6 for details.
The server MAY append additional bytes to the connection ID, up to
the limit specified in that version of QUIC, for its own use. These
bytes MUST NOT provide observers with any information that could link
two connection IDs to the same connection, client, or server. In
particular, all servers using a configuration MUST consistently add
the same length to each connection ID, to preserve the linkability
objectives of QUIC-LB. Any additional bytes SHOULD appear random
unless individual servers are not distinguishable (e.g. any server
using that configuration appends identical bytes to every connection
ID).
If there is no key in the configuration, the Connection ID is
complete. Otherwise, there are further steps, as described in the
two following subsections.
Encryption below uses the AES-128-ECB cipher. Future standards could
add new algorithms that use other ciphers to provide cryptographic
agility in accordance with [RFC7696]. QUIC-LB implementations SHOULD
be extensible to support new algorithms.
4.3.1. Special Case: Single Pass Encryption
When the nonce length and server ID length sum to exactly 16 octets,
the server MUST use a single-pass encryption algorithm. All
connection ID octets except the first form an AES-ECB block. This
block is encrypted once, and the result forms the second through
seventeenth most significant bytes of the connection ID.
4.3.2. General Case: Four-Pass Encryption
Any other field length requires four passes for encryption and at
least three for decryption. To understand this algorithm, it is
useful to define four functions that minimize the amount of bit-
shifting necessary in the event that there are an odd number of
octets.
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The expand_left() function outputs 16 octets, with its first argument
in the most significant bits, its second argument in the least
significant byte, its third argument in the second least significant
byte, and zeros in all other positions. Thus,
expand_left(0xaaba3c, 0x0b, 0x02) =
0xaaba3c0000000000000000000000020b
expand_right() is similar, except that the second argument is in the
most significant byte, the third is in the second most significant
byte, and the first argument is in the least significant bits.
Therefore,
expand_right(0xaaba3c, 0x0b, 0x02) =
0x0b020000000000000000000000aaba3c
Similarly, truncate_left() and truncate_right() take the most
significant and least significant bits, respectively, from a
ciphertext. For example, to take 28 bits of a ciphertext:
truncate_left(0x2094842ca49256198c2deaa0ba53caa0, 28) = 0x2094842
truncate_right(0x2094842ca49256198c2deaa0ba53caa0, 28) = 0xa53caa0
The example at the end of this section helps to clarify the steps
described below.
1. The server concatenates the server ID and nonce to create
plaintext_CID.
2. The server splits plaintext_CID into components left_0 and
right_0 of equal length, splitting an odd octet in half if
necessary. For example, 0x7040b81b55ccf3 would split into a
left_0 of 0x7040b81 and right_0 of 0xb55ccf3.
3. Encrypt the result of expand_left(left_0, index)) to obtain a
ciphertext, where 'index' is one octet: the two most significant
bits of which are 0b00, and the six least significant bits are
the length of the resulting connection ID in bytes, cid_len.
4. XOR the least significant bits of the ciphertext with right_0 to
form right_1.
Thus steps 3 and 4 can be expressed as right_1 = right_0 ^
truncate_right( AES_ECB(key, expand_left(left_0, cid_len, 1)),
len(right_0))
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5. Repeat steps 3 and 4, but use them to compute left_1 by expanding
and encrypting right_1 with the most significant octet as the
concatenation of 0b01 and cid_len, and XOR the results with
left_0.
left_1 = left_0 ^ truncate_left( AES_ECB(key,
expand_right(right_1, cid_len, 2)), len(left_0))
6. Repeat steps 3 and 4, but use them to compute right_2 by
expanding and encrypting left_1 with the least significant octet
as the concatenation of 0b10 and cid_len, and XOR the results
with right_1.
right_2 = right_1 ^ truncate_right( AES_ECB(key,
expand_left(left_1, cid_len, 3), len(right_1))
7. Repeat steps 3 and 4, but use them to compute left_2 by expanding
and encrypting right_2 with the most significant octet as the
concatenation of 0b11 ands cid_len, and XOR the results with
left_1.
left_2 = left_1 ^ truncate_left( AES_ECB(key,
expand_right(right_2, cid_len, 4), len(left_1))
8. The server concatenates left_2 with right_2 to form the
ciphertext CID, which it appends to the first octet.
The following example executes the steps for the provided inputs.
Note that the plaintext is of odd octet length, so the middle octet
will be split evenly left_0 and right_0.
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server_id = 0x31441a
nonce = 0x9c69c275
key = 0xfdf726a9893ec05c0632d3956680baf0
// step 1
plaintext_CID = 0x31441a9c69c275
// step 2
left_0 = 0x31441a9
right_0 = 0xc69c275
// step 3
cid_len = 8
aes_input = 0x31441a90000000000000000000000108
ciphertext = 0xa60469a0a97d565da383af820e3b689a
// step 4
right_1 = 0xc69c275 ^ 0xe3b689a = 0x252aaef
// step 5
aes_input = 0x0802000000000000000000000252aaef
aes_output = 0xd7e5202ae06026c25d5f4d14d5ead17b
left_1 = 0x31441a9 ^ 0xd7e5202 = 0xe6a13ab
// step 6
aes_input = 0xe6a13ab0000000000000000000000308
aes_output = 0x9b6d9e6777cfc4bfb8bbdc63beb34a3d
right_2 = 0x252aaef ^ 0xeb34a3d = 0xce1e0d2
// step 7
aes_input = 0x0804000000000000000000000ce1e0d2
aes_output = 0xd462594b30327d88117ac542c8c33b52
left_2 = 0xe6a13ab ^ 0xd462594 = 0x32c363f
// step 8
cid = first_octet || left_2 || right_2 = 0x0732c363fce1e0d2
4.4. Load Balancer Actions
On each incoming packet, the load balancer extracts consecutive
octets, beginning with the second octet. If there is no key, the
first octets correspond to the server ID.
If there is a key, the load balancer takes one of two actions:
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4.4.1. Special Case: Single Pass Encryption
If server ID length and nonce length sum to exactly 16 octets, they
form a ciphertext block. The load balancer decrypts the block using
the AES-ECB key and extracts the server ID from the most significant
bytes of the resulting plaintext.
4.4.2. General Case: Four-Pass Encryption
First, split the ciphertext CID (excluding the first octet) into its
equal- length components left_2 and right_2. Then follow the process
below:
left_1 = left_2 ^ truncate_left(
AES_ECB(key, expand_right(right_2, cid_len, 4),
len(left_1))
right_1 = right_1 ^ truncate_right(
AES_ECB(key, expand_left(left_1, cid_len, 3),
len(right_1))
left_0 = left_1 ^ truncate_left(
AES_ECB(key, expand_right(right_1, cid_len, 2),
len(left_1))
As the load balancer has no need for the nonce, it can conclude after
3 passes as long as the server ID is entirely contained in left_0
(i.e., the nonce is at least as large as the server ID). If the
server ID is longer, a fourth pass is necessary:
right_0 = right_1 ^ truncate_right( AES_ECB(key, expand_left(left_0,
cid_len, 1), len(right_1))
and the load balancer has to concatenate left_0 and right_0 to obtain
the complete server ID.
5. Per-connection state
QUIC-LB requires no per-connection state at the load balancer. The
load balancer can extract the server ID from the connection ID of
each incoming packet and route that packet accordingly.
However, once the routing decision has been made, the load balancer
MAY associate the 4-tuple or connection ID with the decision. This
has two advantages:
* The load balancer only extracts the server ID once until the
4-tuple or connection ID changes. When the CID is encrypted, this
might reduce computational load.
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* Incoming Stateless Reset packets and ICMP messages are easily
routed to the correct origin server.
In addition to the increased state requirements, however, load
balancers cannot detect the CONNECTION_CLOSE frame to indicate the
end of the connection, so they rely on a timeout to delete connection
state. There are numerous considerations around setting such a
timeout.
In the event a connection ends, freeing an IP and port, and a
different connection migrates to that IP and port before the timeout,
the load balancer will misroute the different connection's packets to
the original server. A short timeout limits the likelihood of such a
misrouting.
Furthermore, if a short timeout causes premature deletion of state,
the routing is easily recoverable by decoding an incoming Connection
ID. However, a short timeout also reduces the chance that an
incoming Stateless Reset is correctly routed.
Servers MAY implement the technique described in Section 14.4.1 of
[RFC9000] in case the load balancer is stateless, to increase the
likelihood a Source Connection ID is included in ICMP responses to
Path Maximum Transmission Unit (PMTU) probes. Load balancers MAY
parse the echoed packet to extract the Source Connection ID, if it
contains a QUIC long header, and extract the Server ID as if it were
in a Destination CID.
6. Additional Use Cases
This section discusses considerations for some deployment scenarios
not implied by the specification above.
6.1. Load balancer chains
Some network architectures may have multiple tiers of low-state load
balancers, where a first tier of devices makes a routing decision to
the next tier, and so on, until packets reach the server. Although
QUIC-LB is not explicitly designed for this use case, it is possible
to support it.
If each load balancer is assigned a range of server IDs that is a
subset of the range of IDs assigned to devices that are closer to the
client, then the first devices to process an incoming packet can
extract the server ID and then map it to the correct forwarding
address. Note that this solution is extensible to arbitrarily large
numbers of load-balancing tiers, as the maximum server ID space is
quite large.
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If the number of necessary server IDs per next hop is uniform, a
simple implementation would use successively longer server IDs at
each tier of load balancing, and the server configuration would match
the last tier. The forward load balancers would simply treat the
least significant bits of the server ID as part of the nonce.
6.2. Server Process Demultiplexing
QUIC servers might have QUIC running on multiple processes listening
on the same address, and have a need to demultiplex between them. In
principle, this demultiplexer is a Layer 4 load balancer, and the
guidance in Section 6.1 applies. However, in many deployments the
demultiplexer lacks the capability to perform decryption operations.
There are some other techniques that might work, depending on the
capabilities of the server architecture.
* Some bytes of the server ID are reserved to encode the process ID.
The demultiplexer might operate based on the 4-tuple or other
legacy indicator, but the receiving server process extracts the
server ID, and if it does not match the one for that process, the
process could "toss" the packet to the correct destination
process.
* Each process could register the connection IDs it generates with
the demultiplexer, which routes those connection IDs accordingly.
* Some bytes of the server ID are reserved to encode the process ID.
The load balancer writes the decrypted connection ID into the
packet. The demultiplexer reads the process ID from the relevant
bytes and routes it accordingly. The receiving server process
immediately re-encrypts the connection ID in deliver the packet to
the correct connection and successfully authenticate the packet.
While this requires coordination between load balancer and server,
this document does not standardize the technique because it is
unsafe to use unless the path between load balancer and server is
fully secure. An observer at that point can determine the server
mapping via the IP address of the destination server, but the
process ID provides additional linkability information.
6.3. Moving connections between servers
Some deployments may transparently move a connection from one server
to another. The means of transferring connection state between
servers is out of scope of this document.
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To support a handover, a server involved in the transition could
issue CIDs that map to the new server via a NEW_CONNECTION_ID frame,
and retire CIDs associated with the new server using the "Retire
Prior To" field in that frame.
Alternately, if the old server is going offline, the load balancer
could simply map its server ID to the new server's address.
7. Version Invariance of QUIC-LB
The server ID encodings, and requirements for their handling, are
designed to be QUIC version independent (see [RFC8999]). A QUIC-LB
load balancer will generally not require changes as servers deploy
new versions of QUIC. However, there are several unlikely future
design decisions that could impact the operation of QUIC-LB.
The maximum Connection ID length could be below the minimum necessary
to use all or part of this specification. The minimum Connection ID
length could exceed the limits in this specification.
Section 3.1 provides guidance about how load balancers should handle
unroutable DCIDs. This guidance, and the implementation of an
algorithm to handle these DCIDs, rests on some assumptions:
* Incoming short headers do not contain DCIDs that are client-
generated.
* The use of client-generated incoming DCIDs does not persist beyond
a few round trips in the connection.
* While the client is using DCIDs it generated, some exposed fields
(IP address, UDP port, client-generated destination Connection ID)
remain constant for all packets sent on the same connection.
While this document does not update the commitments in [RFC8999], the
additional assumptions are minimal and narrowly scoped, and provide a
likely set of constants that load balancers can use with minimal risk
of version- dependence.
If these assumptions are not valid, this specification is likely to
lead to loss of packets that contain unroutable DCIDs, and in extreme
cases connection failure.
Some load balancers might inspect elements of the Server Name
Indication (SNI) extension in the TLS Client Hello to make a routing
decision. Note that the format and cryptographic protection of this
information may change in future versions or extensions of TLS or
QUIC, and therefore this functionality is inherently not version-
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invariant. See also Section 3.1 for other considerations about this
case. Note that an SNI-aware load balancer, faced with an unknown
QUIC version, might misdirect initial packets to the wrong tenant.
While inefficient, this preserves the ability for tenants to deploy
new versions provided they have an out-of-band means of providing a
connection ID for the client to use.
8. Security Considerations
QUIC-LB is intended to prevent linkability. Attacks would therefore
attempt to subvert this purpose.
Note that without a key for the encoding, QUIC-LB makes no attempt to
obscure the server mapping, and therefore does not address these
concerns. Without a key, QUIC-LB merely allows consistent CID
encoding for compatibility across a network infrastructure, which
makes QUIC robust to NAT rebinding. Servers that are encoding their
server ID without a key algorithm SHOULD only use it to generate new
CIDs for the Server Initial Packet and SHOULD NOT send CIDs in QUIC
NEW_CONNECTION_ID frames, except that it sends one new Connection ID
in the event of config rotation Section 2.1. Doing so might falsely
suggest to the client that said CIDs were generated in a secure
fashion.
A linkability attack would find some means of determining that two
connection IDs route to the same server. As described above, there
is no scheme that strictly prevents linkability for all traffic
patterns, and therefore efforts to frustrate any analysis of server
ID encoding have diminishing returns.
8.1. Attackers not between the load balancer and server
Any attacker might open a connection to the server infrastructure and
aggressively simulate migration to obtain a large sample of IDs that
map to the same server. It could then apply analytical techniques to
try to obtain the server encoding.
An encrypted encoding provides robust protection against this. An
unencrypted one provides none.
Were this analysis to obtain the server encoding, then on-path
observers might apply this analysis to correlating different client
IP addresses.
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8.2. Attackers between the load balancer and server
Attackers in this privileged position are intrinsically able to map
two connection IDs to the same server. The QUIC-LB algorithms do
prevent the linkage of two connection IDs to the same individual
connection if servers make reasonable selections when generating new
IDs for that connection.
8.3. Multiple Configuration IDs
During the period in which there are multiple deployed configuration
IDs (see Section 2.1), there is a slight increase in linkability.
The server space is effectively divided into segments with CIDs that
have different config rotation bits. Entities that manage servers
SHOULD strive to minimize these periods by quickly deploying new
configurations across the server pool.
8.4. Limited configuration scope
A simple deployment of QUIC-LB in a cloud provider might use the same
global QUIC-LB configuration across all its load balancers that route
to customer servers. An attacker could then simply become a
customer, obtain the configuration, and then extract server IDs of
other customers' connections at will.
To avoid this, the configuration agent SHOULD issue QUIC-LB
configurations to mutually distrustful servers that have different
keys for encryption algorithms. In many cases, the load balancers
can distinguish these configurations by external IP address.
However, assigning multiple entities to an IP address is
complimentary with concealing DNS requests (e.g., DoH [RFC8484]) and
the TLS Server Name Indicator (SNI) ([I-D.ietf-tls-esni]) to obscure
the ultimate destination of traffic. While the load balancer's
fallback algorithm (Section 3.2) can use the SNI to make a routing
decision on the first packet, there are three ways to route
subsequent packets:
* all co-tenants can use the same QUIC-LB configuration, leaking the
server mapping to each other as described above;
* co-tenants can be issued one of up to three configurations
distinguished by the config rotation bits (Section 2.1), exposing
information about the target domain to the entire network; or
* tenants can use the 0b11 codepoint in their CIDs (in which case
they SHOULD disable migration in their connections), which
neutralizes the value of QUIC-LB but preserves privacy.
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When configuring QUIC-LB, administrators must evaluate the privacy
tradeoff considering the relative value of each of these properties,
given the trust model between tenants, the presence of methods to
obscure the domain name, and value of address migration in the tenant
use cases.
As the plaintext algorithm makes no attempt to conceal the server
mapping, these deployments SHOULD simply use a common configuration.
8.5. Stateless Reset Oracle
Section 21.9 of [RFC9000] discusses the Stateless Reset Oracle
attack. For a server deployment to be vulnerable, an attacking
client must be able to cause two packets with the same Destination
CID to arrive at two different servers that share the same
cryptographic context for Stateless Reset tokens. As QUIC-LB
requires deterministic routing of DCIDs over the life of a
connection, it is a sufficient means of avoiding an Oracle without
additional measures.
Note also that when a server starts using a new QUIC-LB config
rotation codepoint, new CIDs might not be unique with respect to
previous configurations that occupied that codepoint, and therefore
different clients may have observed the same CID and stateless reset
token. A straightforward method of managing stateless reset keys is
to maintain a separate key for each config rotation codepoint, and
replace each key when the configuration for that codepoint changes.
Thus, a server transitions from one config to another, it will be
able to generate correct tokens for connections using either type of
CID.
8.6. Connection ID Entropy
If a server ever reuses a nonce in generating a CID for a given
configuration, it risks exposing sensitive information. Given the
same server ID, the CID will be identical (aside from a possible
difference in the first octet). This can risk exposure of the QUIC-
LB key. If two clients receive the same connection ID, they also
have each other's stateless reset token unless that key has changed
in the interim.
The encrypted mode needs to generate different cipher text for each
generated Connection ID instance to protect the Server ID. To do so,
at least four octets of the CID are reserved for a nonce that, if
used only once, will result in unique cipher text for each Connection
ID.
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If servers simply increment the nonce by one with each generated
connection ID, then it is safe to use the existing keys until any
server's nonce counter exhausts the allocated space and rolls over.
To maximize entropy, servers SHOULD start with a random nonce value,
in which case the configuration is usable until the nonce value wraps
around to zero and then reaches the initial value again.
Whether or not it implements the counter method, the server MUST NOT
reuse a nonce until it switches to a configuration with new keys.
If the nonce is sent in plaintext, servers MUST generate nonces so
that they appear to be random. Observable correlations between
plaintext nonces would provide trivial linkability between individual
connections, rather than just to a common server.
For any algorithm, configuration agents SHOULD implement an out-of-
band method to discover when servers are in danger of exhausting
their nonce space, and SHOULD respond by issuing a new configuration.
A server that has exhausted its nonces MUST either switch to a
different configuration, or if none exists, use the 4-tuple routing
config rotation codepoint.
When sizing a nonce that is to be randomly generated, the
configuration agent SHOULD consider that a server generating a N-bit
nonce will create a duplicate about every 2^(N/2) attempts, and
therefore compare the expected rate at which servers will generate
CIDs with the lifetime of a configuration.
8.7. Distinguishing Attacks
The Four Pass Encryption algorithm is structured as a 4-round Feistel
network with non-bijective round function. As such, it does not
offer a very high security level against distinguishing attacks, as
explained in [Patarin2008]. Attackers can mount these attacks if
they are in possession of O(SQRT(len/2)) pairs of ciphertext and
known corresponding plain text, where "len" is the sum of the lengths
of the Server ID and the Nonce.
The authors considered increasing the number of passes from 4 to 12,
which would definitely block these attacks. However, this would
require 12 round of AES decryption by load balancers accessing the
CID, a cost deemed prohibitive in the planned deployments.
The attacks described in [Patarin2008] rely on known plain text. In
a normal deployment, the plain text is only known by the server that
generates the ID and by the load balancer that decrypts the content
of the CID. Attackers would have to compensate by guesses about the
allocation of server identifiers or the generation of nonces. The
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these attacks are thus mitigated by making nonces hard to guess, as
specified in Section 8.6, and by rules related to mixed deployments
that use both clear text CID and encrypted CID, for example when
transitioning from clear text to encryption. Such deployments MUST
use different server ID allocations for the clear text and the
encrypted versions.
These attacks cannot be mounted against the Single Pass Encryption
algorithm.
9. IANA Considerations
There are no IANA requirements.
10. References
10.1. Normative References
[RFC8999] Thomson, M., "Version-Independent Properties of QUIC",
RFC 8999, DOI 10.17487/RFC8999, May 2021,
<https://www.rfc-editor.org/info/rfc8999>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
10.2. Informative References
[I-D.draft-ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", Work in Progress, Internet-Draft, draft-ietf-tls-
dtls13-43, 30 April 2021,
<https://www.ietf.org/archive/id/draft-ietf-tls-
dtls13-43.txt>.
[I-D.ietf-tls-dtls-connection-id]
Rescorla, E., Tschofenig, H., Fossati, T., and A. Kraus,
"Connection Identifier for DTLS 1.2", Work in Progress,
Internet-Draft, draft-ietf-tls-dtls-connection-id-13, 22
June 2021, <https://www.ietf.org/archive/id/draft-ietf-
tls-dtls-connection-id-13.txt>.
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[I-D.ietf-tls-esni]
Rescorla, E., Oku, K., Sullivan, N., and C. A. Wood, "TLS
Encrypted Client Hello", Work in Progress, Internet-Draft,
draft-ietf-tls-esni-14, 13 February 2022,
<https://www.ietf.org/archive/id/draft-ietf-tls-esni-
14.txt>.
[Patarin2008]
Patarin, J., "Generic Attacks on Feistel Schemes -
Extended Version", 2008,
<https://eprint.iacr.org/2008/036.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, DOI 10.17487/RFC4347, April 2006,
<https://www.rfc-editor.org/info/rfc4347>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
January 2012, <https://www.rfc-editor.org/info/rfc6347>.
[RFC7696] Housley, R., "Guidelines for Cryptographic Algorithm
Agility and Selecting Mandatory-to-Implement Algorithms",
BCP 201, RFC 7696, DOI 10.17487/RFC7696, November 2015,
<https://www.rfc-editor.org/info/rfc7696>.
[RFC7983] Petit-Huguenin, M. and G. Salgueiro, "Multiplexing Scheme
Updates for Secure Real-time Transport Protocol (SRTP)
Extension for Datagram Transport Layer Security (DTLS)",
RFC 7983, DOI 10.17487/RFC7983, September 2016,
<https://www.rfc-editor.org/info/rfc7983>.
[RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
<https://www.rfc-editor.org/info/rfc8340>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
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Appendix A. QUIC-LB YANG Model
These YANG models conform to [RFC6020] and express a complete QUIC-LB
configuration. There is one model for the server and one for the
middlebox (i.e the load balancer and/or Retry Service).
module ietf-quic-lb-server {
yang-version "1.1";
namespace "urn:ietf:params:xml:ns:yang:ietf-quic-lb";
prefix "quic-lb";
import ietf-yang-types {
prefix yang;
reference
"RFC 6991: Common YANG Data Types.";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types.";
}
organization
"IETF QUIC Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/quic>
WG List: <quic@ietf.org>
Authors: Martin Duke (martin.h.duke at gmail dot com)
Nick Banks (nibanks at microsoft dot com)
Christian Huitema (huitema at huitema.net)";
description
"This module enables the explicit cooperation of QUIC servers
with trusted intermediaries without breaking important
protocol features.
Copyright (c) 2022 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
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This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";
revision "2022-02-11" {
description
"Updated to design in version 13 of the draft";
reference
"RFC XXXX, QUIC-LB: Generating Routable QUIC Connection IDs";
}
container quic-lb {
presence "The container for QUIC-LB configuration.";
description
"QUIC-LB container.";
typedef quic-lb-key {
type yang:hex-string {
length 47;
}
description
"This is a 16-byte key, represented with 47 bytes";
}
leaf config-id {
type uint8 {
range "0..2";
}
mandatory true;
description
"Identifier for this CID configuration.";
}
leaf first-octet-encodes-cid-length {
type boolean;
default false;
description
"If true, the six least significant bits of the first
CID octet encode the CID length minus one.";
}
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leaf server-id-length {
type uint8 {
range "1..15";
}
must '. <= (19 - ../nonce-length)' {
error-message
"Server ID and nonce lengths must sum
to no more than 19.";
}
mandatory true;
description
"Length (in octets) of a server ID. Further range-limited
by nonce-length.";
}
leaf nonce-length {
type uint8 {
range "4..18";
}
mandatory true;
description
"Length, in octets, of the nonce. Short nonces mean there
will be frequent configuration updates.";
}
leaf cid-key {
type quic-lb-key;
description
"Key for encrypting the connection ID.";
}
leaf server-id {
type yang:hex-string;
must "string-length(.) = 3 * ../../server-id-length - 1";
mandatory true;
description
"An allocated server ID";
}
}
}
module ietf-quic-lb-middlebox {
yang-version "1.1";
namespace "urn:ietf:params:xml:ns:yang:ietf-quic-lb";
prefix "quic-lb";
import ietf-yang-types {
prefix yang;
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reference
"RFC 6991: Common YANG Data Types.";
}
import ietf-inet-types {
prefix inet;
reference
"RFC 6991: Common YANG Data Types.";
}
organization
"IETF QUIC Working Group";
contact
"WG Web: <http://datatracker.ietf.org/wg/quic>
WG List: <quic@ietf.org>
Authors: Martin Duke (martin.h.duke at gmail dot com)
Nick Banks (nibanks at microsoft dot com)
Christian Huitema (huitema at huitema.net)";
description
"This module enables the explicit cooperation of QUIC servers
with trusted intermediaries without breaking important
protocol features.
Copyright (c) 2021 IETF Trust and the persons identified as
authors of the code. All rights reserved.
Redistribution and use in source and binary forms, with or
without modification, is permitted pursuant to, and subject to
the license terms contained in, the Simplified BSD License set
forth in Section 4.c of the IETF Trust's Legal Provisions
Relating to IETF Documents
(https://trustee.ietf.org/license-info).
This version of this YANG module is part of RFC XXXX
(https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself
for full legal notices.
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
'MAY', and 'OPTIONAL' in this document are to be interpreted as
described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
they appear in all capitals, as shown here.";
revision "2021-02-11" {
description
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"Updated to design in version 13 of the draft";
reference
"RFC XXXX, QUIC-LB: Generating Routable QUIC Connection IDs";
}
container quic-lb {
presence "The container for QUIC-LB configuration.";
description
"QUIC-LB container.";
typedef quic-lb-key {
type yang:hex-string {
length 47;
}
description
"This is a 16-byte key, represented with 47 bytes";
}
list cid-configs {
key "config-rotation-bits";
description
"List up to three load balancer configurations";
leaf config-rotation-bits {
type uint8 {
range "0..2";
}
mandatory true;
description
"Identifier for this CID configuration.";
}
leaf server-id-length {
type uint8 {
range "1..15";
}
must '. <= (19 - ../nonce-length)' {
error-message
"Server ID and nonce lengths must sum to
no more than 19.";
}
mandatory true;
description
"Length (in octets) of a server ID. Further range-limited
by nonce-length.";
}
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leaf cid-key {
type quic-lb-key;
description
"Key for encrypting the connection ID.";
}
leaf nonce-length {
type uint8 {
range "4..18";
}
mandatory true;
description
"Length, in octets, of the nonce. Short nonces mean there
will be frequent configuration updates.";
}
list server-id-mappings {
key "server-id";
description "Statically allocated Server IDs";
leaf server-id {
type yang:hex-string;
must "string-length(.) = 3 * ../../server-id-length - 1";
mandatory true;
description
"An allocated server ID";
}
leaf server-address {
type inet:ip-address;
mandatory true;
description
"Destination address corresponding to the server ID";
}
}
}
}
}
A.1. Tree Diagram
This summary of the YANG models uses the notation in [RFC8340].
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module: ietf-quic-lb-server
+--rw quic-lb!
+--rw config-id uint8
+--rw first-octet-encodes-cid-length? boolean
+--rw server-id-length uint8
+--rw nonce-length uint8
+--rw cid-key? quic-lb-key
+--rw server-id yang:hex-string
module: ietf-quic-lb-middlebox
+--rw quic-lb!
+--rw cid-configs* [config-rotation-bits]
| +--rw config-rotation-bits uint8
| +--rw server-id-length uint8
| +--rw cid-key? quic-lb-key
| +--rw nonce-length uint8
| +--rw server-id-mappings* [server-id]
| +--rw server-id yang:hex-string
| +--rw server-address inet:ip-address
Appendix B. Load Balancer Test Vectors
This section uses the following abbreviations:
cid Connection ID
cr_bits Config Rotation Bits
LB Load Balancer
sid Server ID
In all cases, the server is configured to encode the CID length.
B.1. Unencrypted CIDs
cr_bits sid nonce cid
0 c4605e 4504cc4f 07c4605e4504cc4f
1 350d28b420 3487d970b 40a350d28b4203487d970b
B.2. Encrypted CIDs
The key for all of these examples is
8f95f09245765f80256934e50c66207f. The test vectors include an
example that uses the 16-octet single-pass special case, as well as
an instance where the server ID length exceeds the nonce length,
requiring a fourth decryption pass.
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cr_bits sid nonce cid
0 ed793a ee080dbf 0727edaa37e7fac8
1 ed793a51d49b8f5fab65 ee080dbf48
4f22614a97ceee84341ed7fbfeb1e6e2
2 ed793a51d49b8f5f ee080dbf48c0d1e5
904dd2d05a7b0de9b2b9907afb5ecf8cc3
0 ed793a51d49b8f5fab ee080dbf48c0d1e55d
125e3b00aa5fcfd1a9a58102a89a19a1e4a10e
Appendix C. Interoperability with DTLS over UDP
Some environments may contain DTLS traffic as well as QUIC operating
over UDP, which may be hard to distinguish.
In most cases, the packet parsing rules above will cause a QUIC-LB
load balancer to route DTLS traffic in an appropriate way. DTLS 1.3
implementations that use the connection_id extension
[I-D.ietf-tls-dtls-connection-id] might use the techniques in this
document to generate connection IDs and achieve robust routability
for DTLS associations if they meet a few additional requirements.
This non-normative appendix describes this interaction.
C.1. DTLS 1.0 and 1.2
DTLS 1.0 [RFC4347] and 1.2 [RFC6347] use packet formats that a QUIC-
LB router will interpret as short header packets with CIDs that
request 4-tuple routing. As such, they will route such packets
consistently as long as the 4-tuple does not change. Note that DTLS
1.0 has been deprecated by the IETF.
The first octet of every DTLS 1.0 or 1.2 datagram contains the
content type. A QUIC-LB load balancer will interpret any content
type less than 128 as a short header packet, meaning that the
subsequent octets should contain a connection ID.
Existing TLS content types comfortably fit in the range below 128.
Assignment of codepoints greater than 64 would require coordination
in accordance with [RFC7983], and anyway would likely create problems
demultiplexing DTLS and version 1 of QUIC. Therefore, this document
believes it is extremely unlikely that TLS content types of 128 or
greater will be assigned. Nevertheless, such an assignment would
cause a QUIC-LB load balancer to interpret the packet as a QUIC long
header with an essentially random connection ID, which is likely to
be routed irregularly.
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The second octet of every DTLS 1.0 or 1.2 datagram is the bitwise
complement of the DTLS Major version (i.e. version 1.x = 0xfe). A
QUIC-LB load balancer will interpret this as a connection ID that
requires 4-tuple based load balancing, meaning that the routing will
be consistent as long as the 4-tuple remains the same.
[I-D.ietf-tls-dtls-connection-id] defines an extension to add
connection IDs to DTLS 1.2. Unfortunately, a QUIC-LB load balancer
will not correctly parse the connection ID and will continue 4-tuple
routing. An modified QUIC-LB load balancer that correctly identifies
DTLS and parses a DTLS 1.2 datagram for the connection ID is outside
the scope of this document.
C.2. DTLS 1.3
DTLS 1.3 [I-D.draft-ietf-tls-dtls13] changes the structure of
datagram headers in relevant ways.
Handshake packets continue to have a TLS content type in the first
octet and 0xfe in the second octet, so they will be 4-tuple routed,
which should not present problems for likely NAT rebinding or address
change events.
Non-handshake packets always have zero in their most significant bit
and will therefore always be treated as QUIC short headers. If the
connection ID is present, it follows in the succeeding octets.
Therefore, a DTLS 1.3 association where the server utilizes
Connection IDs and the encodings in this document will be routed
correctly in the presence of client address and port changes.
However, if the client does not include the connection_id extension
in its ClientHello, the server is unable to use connection IDs. In
this case, non- handshake packets will appear to contain random
connection IDs and be routed randomly. Thus, unmodified QUIC-LB load
balancers will not work with DTLS 1.3 if the client does not
advertise support for connection IDs, or the server does not request
the use of a compliant connection ID.
A QUIC-LB load balancer might be modified to identify DTLS 1.3
packets and correctly parse the fields to identify when there is no
connection ID and revert to 4-tuple routing, removing the server
requirement above. However, such a modification is outside the scope
of this document, and classifying some packets as DTLS might be
incompatible with future versions of QUIC.
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C.3. Future Versions of DTLS
As DTLS does not have an IETF consensus document that defines what
parts of DTLS will be invariant in future versions, it is difficult
to speculate about the applicability of this section to future
versions of DTLS.
Appendix D. Acknowledgments
Manasi Deval, Erik Fuller, Toma Gavrichenkov, Jana Iyengar, Subodh
Iyengar, Ladislav Lhotka, Jan Lindblad, Ling Tao Nju, Ilari
Liusvaara, Kazuho Oku, Udip Pant, Ian Swett, Martin Thomson, Dmitri
Tikhonov, Victor Vasiliev, and William Zeng Ke all provided useful
input to this document.
Appendix E. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
E.1. since draft-ietf-quic-load-balancers-13
* Incorporated Connection ID length in argument of truncate function
* Added requirements for codepoint 0b11.
* Describe Distinguishing Attack in Security Considerations.
* Added non-normative language about server process demultiplexers
E.2. since draft-ietf-quic-load-balancers-12
* Separated Retry Service design into a separate draft
E.3. since draft-ietf-quic-load-balancers-11
* Fixed mistakes in test vectors
E.4. since draft-ietf-quic-load-balancers-10
* Refactored algorithm descriptions; made the 4-pass algorithm
easier to implement
* Revised test vectors
* Split YANG model into a server and middlebox version
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E.5. since draft-ietf-quic-load-balancers-09
* Renamed "Stream Cipher" and "Block Cipher" to "Encrypted Short"
and "Encrypted Long"
* Added section on per-connection state
* Changed "Encrypted Short" to a 4-pass algorithm.
* Recommended a random initial nonce when incrementing.
* Clarified what SNI LBs should do with unknown QUIC versions.
E.6. since draft-ietf-quic-load-balancers-08
* Eliminate Dynamic SID allocation
* Eliminated server use bytes
E.7. since draft-ietf-quic-load-balancers-07
* Shortened SSCID nonce minimum length to 4 bytes
* Removed RSCID from Retry token body
* Simplified CID formats
* Shrunk size of SID table
E.8. since draft-ietf-quic-load-balancers-06
* Added interoperability with DTLS
* Changed "non-compliant" to "unroutable"
* Changed "arbitrary" algorithm to "fallback"
* Revised security considerations for mistrustful tenants
* Added retry service considerations for non-Initial packets
E.9. since draft-ietf-quic-load-balancers-05
* Added low-config CID for further discussion
* Complete revision of shared-state Retry Token
* Added YANG model
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* Updated configuration limits to ensure CID entropy
* Switched to notation from quic-transport
E.10. since draft-ietf-quic-load-balancers-04
* Rearranged the shared-state retry token to simplify token
processing
* More compact timestamp in shared-state retry token
* Revised server requirements for shared-state retries
* Eliminated zero padding from the test vectors
* Added server use bytes to the test vectors
* Additional compliant DCID criteria
E.11. since-draft-ietf-quic-load-balancers-03
* Improved Config Rotation text
* Added stream cipher test vectors
* Deleted the Obfuscated CID algorithm
E.12. since-draft-ietf-quic-load-balancers-02
* Replaced stream cipher algorithm with three-pass version
* Updated Retry format to encode info for required TPs
* Added discussion of version invariance
* Cleaned up text about config rotation
* Added Reset Oracle and limited configuration considerations
* Allow dropped long-header packets for known QUIC versions
E.13. since-draft-ietf-quic-load-balancers-01
* Test vectors for load balancer decoding
* Deleted remnants of in-band protocol
* Light edit of Retry Services section
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* Discussed load balancer chains
E.14. since-draft-ietf-quic-load-balancers-00
* Removed in-band protocol from the document
E.15. Since draft-duke-quic-load-balancers-06
* Switch to IETF WG draft.
E.16. Since draft-duke-quic-load-balancers-05
* Editorial changes
* Made load balancer behavior independent of QUIC version
* Got rid of token in stream cipher encoding, because server might
not have it
* Defined "non-compliant DCID" and specified rules for handling
them.
* Added psuedocode for config schema
E.17. Since draft-duke-quic-load-balancers-04
* Added standard for retry services
E.18. Since draft-duke-quic-load-balancers-03
* Renamed Plaintext CID algorithm as Obfuscated CID
* Added new Plaintext CID algorithm
* Updated to allow 20B CIDs
* Added self-encoding of CID length
E.19. Since draft-duke-quic-load-balancers-02
* Added Config Rotation
* Added failover mode
* Tweaks to existing CID algorithms
* Added Block Cipher CID algorithm
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* Reformatted QUIC-LB packets
E.20. Since draft-duke-quic-load-balancers-01
* Complete rewrite
* Supports multiple security levels
* Lightweight messages
E.21. Since draft-duke-quic-load-balancers-00
* Converted to markdown
* Added variable length connection IDs
Authors' Addresses
Martin Duke
Google
Email: martin.h.duke@gmail.com
Nick Banks
Microsoft
Email: nibanks@microsoft.com
Christian Huitema
Private Octopus Inc.
Email: huitema@huitema.net
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