Internet DRAFT - draft-duke-quic-load-balancers
draft-duke-quic-load-balancers
QUIC M. Duke
Internet-Draft F5 Networks, Inc.
Intended status: Standards Track N. Banks
Expires: May 7, 2020 Microsoft
November 4, 2019
QUIC-LB: Generating Routable QUIC Connection IDs
draft-duke-quic-load-balancers-06
Abstract
QUIC connection IDs allow continuation of connections across address/
port 4-tuple changes, and can store routing information for stateless
or low-state load balancers. They also can prevent linkability of
connections across deliberate address migration through the use of
protected communications between client and server. This creates
issues for load-balancing intermediaries. This specification
standardizes methods for encoding routing information and proposes an
optional protocol called QUIC-LB to exchange the parameters of that
encoding. This framework also enables offload of other QUIC
functions to trusted intermediaries, given the explicit cooperation
of the QUIC server.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 7, 2020.
Copyright Notice
Copyright (c) 2019 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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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Protocol Objectives . . . . . . . . . . . . . . . . . . . . . 5
2.1. Simplicity . . . . . . . . . . . . . . . . . . . . . . . 5
2.2. Security . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. Robustness to Middleboxes . . . . . . . . . . . . . . . . 6
2.4. Load Balancer Chains . . . . . . . . . . . . . . . . . . 6
3. First CID octet . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Config Rotation . . . . . . . . . . . . . . . . . . . . . 6
3.2. Configuration Failover . . . . . . . . . . . . . . . . . 7
3.3. Length Self-Description . . . . . . . . . . . . . . . . . 7
4. Routing Algorithms . . . . . . . . . . . . . . . . . . . . . 8
4.1. Plaintext CID Algorithm . . . . . . . . . . . . . . . . . 9
4.1.1. Load Balancer Actions . . . . . . . . . . . . . . . . 9
4.1.2. Server Actions . . . . . . . . . . . . . . . . . . . 9
4.2. Obfuscated CID Algorithm . . . . . . . . . . . . . . . . 10
4.2.1. Load Balancer Actions . . . . . . . . . . . . . . . . 10
4.2.2. Server Actions . . . . . . . . . . . . . . . . . . . 11
4.3. Stream Cipher CID Algorithm . . . . . . . . . . . . . . . 11
4.3.1. Load Balancer Actions . . . . . . . . . . . . . . . . 12
4.3.2. Server Actions . . . . . . . . . . . . . . . . . . . 12
4.4. Block Cipher CID Algorithm . . . . . . . . . . . . . . . 13
4.4.1. Load Balancer Actions . . . . . . . . . . . . . . . . 13
4.4.2. Server Actions . . . . . . . . . . . . . . . . . . . 14
5. Retry Service . . . . . . . . . . . . . . . . . . . . . . . . 14
5.1. Common Requirements . . . . . . . . . . . . . . . . . . . 15
5.2. No-Shared-State Retry Service . . . . . . . . . . . . . . 15
5.2.1. Service Requirements . . . . . . . . . . . . . . . . 15
5.2.2. Server Requirements . . . . . . . . . . . . . . . . . 17
5.3. Shared-State Retry Service . . . . . . . . . . . . . . . 17
5.3.1. Service Requirements . . . . . . . . . . . . . . . . 19
5.3.2. Server Requirements . . . . . . . . . . . . . . . . . 19
6. Configuration Requirements . . . . . . . . . . . . . . . . . 19
7. Protocol Description . . . . . . . . . . . . . . . . . . . . 22
7.1. Out of band sharing . . . . . . . . . . . . . . . . . . . 22
7.2. QUIC-LB Message Exchange . . . . . . . . . . . . . . . . 22
7.3. QUIC-LB Packet . . . . . . . . . . . . . . . . . . . . . 22
7.4. Message Types and Formats . . . . . . . . . . . . . . . . 23
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7.4.1. ACK_LB Message . . . . . . . . . . . . . . . . . . . 24
7.4.2. FAIL Message . . . . . . . . . . . . . . . . . . . . 24
7.4.3. ROUTING_INFO Message . . . . . . . . . . . . . . . . 24
7.4.4. STREAM_CID Message . . . . . . . . . . . . . . . . . 25
7.4.5. BLOCK_CID Message . . . . . . . . . . . . . . . . . . 26
7.4.6. SERVER_ID Message . . . . . . . . . . . . . . . . . . 27
7.4.7. MODULUS Message . . . . . . . . . . . . . . . . . . . 27
7.4.8. PLAINTEXT Message . . . . . . . . . . . . . . . . . . 27
7.4.9. RETRY_SERVICE_STATELESS message . . . . . . . . . . . 28
7.4.10. RETRY_SERVICE_STATEFUL message . . . . . . . . . . . 28
8. Security Considerations . . . . . . . . . . . . . . . . . . . 28
8.1. Outside attackers . . . . . . . . . . . . . . . . . . . . 29
8.2. Inside Attackers . . . . . . . . . . . . . . . . . . . . 29
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 29
10.1. Normative References . . . . . . . . . . . . . . . . . . 30
10.2. Informative References . . . . . . . . . . . . . . . . . 30
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 30
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 30
B.1. Since draft-duke-quic-load-balancers-05 . . . . . . . . . 30
B.2. Since draft-duke-quic-load-balancers-04 . . . . . . . . . 30
B.3. Since draft-duke-quic-load-balancers-03 . . . . . . . . . 30
B.4. Since draft-duke-quic-load-balancers-02 . . . . . . . . . 31
B.5. Since draft-duke-quic-load-balancers-01 . . . . . . . . . 31
B.6. Since draft-duke-quic-load-balancers-00 . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction
QUIC packets 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
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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 a method of coordination between QUIC
servers and low-state load balancers to support connection IDs that
encode routing information. It describes desirable properties of a
solution, and then specifies a protocol that provides those
properties. This protocol supports multiple encoding schemes that
increase in complexity as they address paths between load balancer
and server with weaker trust dynamics.
Aside from load balancing, a QUIC server may also desire to offload
other protocol functions to trusted intermediaries. These
intermediaries might include hardware assist on the server host
itself, without access to fully decrypted QUIC packets. For example,
this document specifies a means of offloading stateless retry to
counter Denial of Service attacks. It also proposes a system for
self-encoding connection ID length in all packets, so that crypto
offload can consistently look up key information.
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.
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.
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When discussing security threats to QUIC-LB, we distinguish between
"inside observers" and "outside observers." The former lie on the
path between the load balancer and server, which often but not always
lies inside the server's data center or cloud deployment. Outside
observers are on the path between the load balancer and client.
"Off-path" attackers, though not on any data path, may also be
"inside" or "outside" depending on whether not they have network
access to the server without intermediation by the load balancer and/
or other security devices.
2. Protocol Objectives
2.1. Simplicity
QUIC is intended to provide unlinkability across connection
migration, but servers are not required to provide additional
connection IDs that effectively prevent linkability. If the
coordination scheme is too difficult to implement, servers behind
load balancers using connection IDs for routing will use trivially
linkable connection IDs. Clients will therefore be forced choose
between terminating the connection during migration or remaining
linkable, subverting a design objective of QUIC.
The solution should be both simple to implement and require little
additional infrastructure for cryptographic keys, etc.
2.2. Security
In the limit where there are very few connections to a pool of
servers, no scheme can prevent the linking of two connection IDs with
high probability. In the opposite limit, where all servers have many
connections that start and end frequently, it will be difficult to
associate two connection IDs even if they are known to map to the
same server.
QUIC-LB is relevant in the region between these extremes: when the
information that two connection IDs map to the same server is helpful
to linking two connection IDs. Obviously, any scheme that
transparently communicates this mapping to outside observers
compromises QUIC's defenses against linkability.
However, concealing this mapping from inside observers is beyond the
scope of QUIC-LB. By simply observing Link-Layer and/or Network-
Layer addresses of packets containing distinct connection IDs, it is
trivial to determine that they map to the same server, even if
connection IDs are entirely random and do not encode routing
information. Schemes that conceal these addresses (e.g., IPsec) can
also conceal QUIC-LB messages.
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Inside observers are generally able to mount Denial of Service (DoS)
attacks on QUIC connections regardless of Connection ID schemes.
However, QUIC-LB should protect against Denial of Service due to
inside off-path attackers in cases where such attackers are possible.
Though not an explicit goal of the QUIC-LB design, concealing the
server mapping also complicates attempts to focus attacks on a
specific server in the pool.
2.3. Robustness to Middleboxes
The path between load balancer and server may pass through
middleboxes that could drop the coordination messages in this
protocol. It is therefore advantageous to make messages resemble
QUIC traffic as much as possible, as any viable path must obviously
admit QUIC traffic.
2.4. Load Balancer Chains
While it is possible to construct a scheme that supports multiple
low-state load balancers in the path, by using different parts of the
connection ID to encode routing information for each load balancer,
this use case is out of scope for QUIC-LB.
3. 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."
3.1. Config Rotation
The first two bits of any connection-ID MUST encode the configuration
phase of that ID. QUIC-LB messages indicate the phase of the
algorithm and parameters that they encode.
A new configuration may change one or more parameters of the old
configuration, or change the algorithm used.
It is possible for servers to have mutually exclusive sets of
supported algorithms, or for a transition from one algorithm to
another to result in Fail Payloads. The four states encoded in these
two bits allow two mutually exclusive server pools to coexist, and
for each of them to transition to a new set of parameters.
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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.
Servers MUST NOT generate new connection IDs using an old
configuration when it has sent an Ack payload for a new
configuration.
Load balancers SHOULD NOT use a codepoint to represent a new
configuration until it takes precautions to make sure that all
connections using IDs with an old configuration at that codepoint
have closed or transitioned. They MAY drop connection IDs with the
old configuration after a reasonable interval to accelerate this
process.
3.2. Configuration Failover
If a server is configured to expect QUIC-LB messages, and it has not
received these, it MUST generate connection IDs with the config
rotation bits set to '11' and MUST use the "disable_migration"
transport parameter in all new QUIC connections. It MUST NOT send
NEW_CONNECTION_ID frames with new values.
A load balancer that sees a connection ID with config rotation bits
set to '11' MUST revert to 5-tuple routing.
3.3. 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.
Note that this is a function of particular server devices and is
irrelevant to load balancers. As such, it is not negotiated between
servers and load balancers. 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.
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4. Routing Algorithms
In QUIC-LB, load balancers do not generate individual connection IDs
to 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.
As clients sometimes generate the DCIDs in long headers, these might
not conform to the expectations of the routing algorithm. These are
called "non-compliant DCIDs":
o The DCID might not be long enough for the routing algorithm to
process.
o The extracted server mapping might not correspond to an active
server.
o A field that should be all zeroes after decryption may not be so.
Load balancers MUST forward packets with long headers with non-
compliant DCIDs to an active server using an algorithm of its own
choosing. It need not coordinate this algorithm with the servers.
The algorithm SHOULD be deterministic over short time scales so that
related packets go to the same server. For example, a non-compliant
DCID might be converted 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.
Load balancers SHOULD drop packets with non-compliant DCIDs in a
short header.
Load balancers MUST forward packets with compliant DCIDs to a server
in accordance with the chosen routing algorithm.
The load balancer 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 build their design on
version-specific templates.
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.
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This section describes two participants: the load balancer and the
server. The load balancer, in this description, generates
configuration parameters. Note that in practice a third party
configuration agent MAY assume this responsibility.
4.1. Plaintext CID Algorithm
The Plaintext CID Algorithm makes no attempt to obscure the mapping
of connections to servers, significantly increasing linkability. The
format is depicted in the figure below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First octet | Server ID (X=8..152) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Any (0..152-X) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Plaintext CID Format
4.1.1. Load Balancer Actions
The load balancer selects a number of bytes of the server connection
ID (SCID) that it will use to route to a given server, called the
"routing bytes". The number of bytes MUST have enough entropy to
have a different code point for each server.
The load balancer shares this value with servers, as explained in
Section 7, along with the value that represents that server.
On each incoming packet, the load balancer extracts consecutive
octets, beginning with the second byte. These bytes represent the
server ID.
4.1.2. Server Actions
The server chooses a connection ID length. This MUST be at least one
byte longer than the routing bytes.
When a server needs a new connection ID, it encodes its assigned
server ID in consecutive octets beginning with the second. All other
bits in the connection ID, except for the first octet, MAY be set to
any other value. These other bits SHOULD appear random to observers.
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4.2. Obfuscated CID Algorithm
The Obfuscated CID Algorithm makes an attempt to obscure the mapping
of connections to servers to reduce linkability, while not requiring
true encryption and decryption. The format is depicted in the figure
below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First octet | Mixed routing and non-routing bits (64..152) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Obfuscated CID Format
4.2.1. Load Balancer Actions
The load balancer selects an arbitrary set of bits of the server
connection ID (SCID) that it will use to route to a given server,
called the "routing bits". The number of bits MUST have enough
entropy to have a different code point for each server, and SHOULD
have enough entropy so that there are many codepoints for each
server.
The load balancer MUST NOT select a routing mask with more than 136
routing bits set to 1, which allows for the first octet and up to 2
octets for server purposes in a maximum-length connection ID.
The load balancer selects a divisor that MUST be larger than the
number of servers. It SHOULD be large enough to accommodate
reasonable increases in the number of servers. The divisor MUST be
an odd integer so certain addition operations do not always produce
an even number.
The load balancer also assigns each server a "modulus", an integer
between 0 and the divisor minus 1. These MUST be unique for each
server, and SHOULD be distributed across the entire number space
between zero and the divisor.
The load balancer shares these three values with servers, as
explained in Section 7.
Upon receipt of a QUIC packet, the load balancer extracts the
selected bits of the SCID and expresses them as an unsigned integer
of that length. The load balancer then divides the result by the
chosen divisor. The modulus of this operation maps to the modulus
for the destination server.
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Note that any SCID that contains a server's modulus, plus an
arbitrary integer multiple of the divisor, in the routing bits is
routable to that server regardless of the contents of the non-routing
bits. Outside observers that do not know the divisor or the routing
bits will therefore have difficulty identifying that two SCIDs route
to the same server.
Note also that not all Connection IDs are necessarily routable, as
the computed modulus may not match one assigned to any server. These
DCIDs are non-compliant as described above.
4.2.2. Server Actions
The server chooses a connection ID length. This MUST contain all of
the routing bits and MUST be at least 9 octets to provide adequate
entropy.
When a server needs a new connection ID, it adds an arbitrary
nonnegative integer multiple of the divisor to its modulus, without
exceeding the maximum integer value implied by the number of routing
bits. The choice of multiple should appear random within these
constraints.
The server encodes the result in the routing bits. It MAY put any
other value into bits that used neither for routing nor config
rotation. These bits SHOULD appear random to observers.
4.3. Stream Cipher CID Algorithm
The Stream Cipher CID algorithm provides true cryptographic
protection, rather than mere obfuscation, at the cost of additional
per-packet processing at the load balancer to decrypt every incoming
connection ID. The CID format is depicted below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First Octet | Nonce (X=64..144) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encrypted Server ID (Y=8..152-X) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| For server use (0..152-X-Y) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Stream Cipher CID Format
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4.3.1. Load Balancer Actions
The load balancer assigns a server ID to every server in its pool,
and determines a server ID length (in octets) sufficiently large to
encode all server IDs, including potential future servers.
The load balancer also selects a nonce length and an 16-octet AES-ECB
key to use for connection ID decryption. The nonce length MUST be at
least 8 octets and no more than 16 octets. The nonce length and
server ID length MUST sum to 19 or fewer octets.
The load balancer shares these three values with servers, as
explained in Section 7.
Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer extracts as many of the earliest octets from the
destination connection ID as necessary to match the nonce length.
The server ID immediately follows.
The load balancer decrypts the server ID using 128-bit AES Electronic
Codebook (ECB) mode, much like QUIC header protection. The nonce
octets are zero-padded to 16 octets. AES-ECB encrypts this nonce
using its key to generate a mask which it applies to the encrypted
server id.
server_id = encrypted_server_id ^ AES-ECB(key, padded-nonce)
For example, if the nonce length is 10 octets and the server ID
length is 2 octets, the connection ID can be as small as 13 octets.
The load balancer uses the the second through eleventh of the
connection ID for the nonce, zero-pads it to 16 octets using the
first 6 octets of the token, and uses this to decrypt the server ID
in the twelfth and thirteenth octet.
The output of the decryption is the server ID that the load balancer
uses for routing.
4.3.2. Server Actions
When generating a routable connection ID, the server writes arbitrary
bits into its nonce octets, and its provided server ID into the
server ID octets. Servers MAY opt to have a longer connection ID
beyond the nonce and server ID. The nonce and additional bits MAY
encode additional information, but SHOULD appear essentially random
to observers.
The server decrypts the server ID using 128-bit AES Electronic
Codebook (ECB) mode, much like QUIC header protection. The nonce
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octets are zero-padded to 16 octets using the as many of the first
octets of the token as necessary. AES-ECB encrypts this nonce using
its key to generate a mask which it applies to the server id.
encrypted_server_id = server_id ^ AES-ECB(key, padded-nonce)
4.4. Block Cipher CID Algorithm
The Block Cipher CID Algorithm, by using a full 16 octets of
plaintext and a 128-bit cipher, provides higher cryptographic
protection and detection of non-compliant connection IDs. However,
it also requires connection IDs of at least 17 octets, increasing
overhead of client-to-server packets.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| First octet | Encrypted server ID (X=8..144) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encrypted Zero Padding (Y=0..144-X) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Encrypted bits for server use (144-X-Y) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Unencrypted bits for server use (0..24) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Block Cipher CID Format
4.4.1. Load Balancer Actions
The load balancer assigns a server ID to every server in its pool,
and determines a server ID length (in octets) sufficiently large to
encode all server IDs, including potential future servers. The
server ID will start in the second octet of the decrypted connection
ID and occupy continuous octets beyond that.
The load balancer selects a zero-padding length. This SHOULD be at
least four octets to allow detection of non-compliant DCIDs. The
server ID and zero- padding length MUST sum to no more than 16
octets. They SHOULD sum to no more than 12 octets, to provide
servers adequate space to encode their own opaque data.
The load balancer also selects an 16-octet AES-ECB key to use for
connection ID decryption.
The load balancer shares these four values with servers, as explained
in Section 7.
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Upon receipt of a QUIC packet that is not of type Initial or 0-RTT,
the load balancer reads the first octet to obtain the config rotation
bits. It then decrypts the subsequent 16 octets using AES-ECB
decryption and the chosen key.
The decrypted plaintext contains the server id, zero padding, and
opaque server data in that order. The load balancer uses the server
ID octets for routing.
4.4.2. Server Actions
When generating a routable connection ID, the server MUST choose a
connection ID length between 17 and 20 octets. The server writes its
provided server ID into the server ID octets, zeroes into the zero-
padding octets, and arbitrary bits into the remaining bits. These
arbitrary bits MAY encode additional information. Bits in the first,
eighteenth, nineteenth, and twentieth octets SHOULD appear
essentially random to observers. The first octet is reserved as
described in Section 3.
The server then encrypts the second through seventeenth octets using
the 128-bit AES-ECB cipher.
5. Retry Service
When a server is under load, QUICv1 allows it to defer storage of
connection state until the client proves it can receive packets at
its advertised IP address. Through the use of a Retry packet, a
token in subsequent client Initial packets, and the
original_connection_id transport parameter, servers verify address
ownership and clients verify that there is no "man in the middle"
generating Retry packets.
As a trusted Retry Service is literally a "man in the middle," the
service must communicate the original_connection_id back to the
server so that in can pass client verification. It also must either
verify the address itself (with the server trusting this
verification) or make sure there is common context for the server to
verify the address using a service-generated token.
There are two different mechanisms to allow offload of DoS mitigation
to a trusted network service. One requires no shared state; the
server need only be configured to trust a retry service, though this
imposes other operational constraints. The other requires shared
key, but has no such constraints.
Retry services MUST forward all non-Initial QUIC packets, as well as
Initial packets from the server.
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5.1. Common Requirements
Regardless of mechanism, a retry service has an active mode, where it
is generating Retry packets, and an inactive mode, where it is not,
based on its assessment of server load and the likelihood an attack
is underway. The choice of mode MAY be made on a per-packet basis,
through a stochastic process or based on client address.
A retry service MUST forward all packets for a QUIC version it does
not understand. Note that if servers support versions the retry
service does not, this may unacceptably increase loads on the
servers. However, dropping these packets would introduce chokepoints
to block deployment of new QUIC versions. Note that future versions
of QUIC might not have Retry packets, or require different
information.
5.2. No-Shared-State Retry Service
The no-shared-state retry service requires no coordination, except
that the server must be configured to accept this service. The
scheme uses the first bit of the token to distinguish between tokens
from Retry packets (codepoint '0') and tokens from NEW_TOKEN frames
(codepoint '1').
5.2.1. Service Requirements
A no-shared-state retry service MUST be present on all paths from
potential clients to the server. These paths MUST fail to pass QUIC
traffic should the service fail for any reason. That is, if the
service is not operational, the server MUST NOT be exposed to client
traffic. Otherwise, servers that have already disabled their Retry
capability would be vulnerable to attack.
The path between service and server MUST be free of any potential
attackers. Note that this and other requirements above severely
restrict the operational conditions in which a no-shared-state retry
service can safely operate.
Retry tokens generated by the service MUST have the format below.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| ODCIL (7) | Original Destination Connection ID (0..160) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Original Destination Connection ID (...) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Data (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Format of non-shared-state retry service tokens
The first bit of retry tokens generated by the service must be zero.
The token has the following additional fields:
ODCIL: The length of the original destination connection ID from the
triggering Initial packet. This is in cleartext to be readable for
the server, but authenticated later in the token.
Original Destination Connection ID: This also in cleartext and
authenticated later.
Opaque Data: This data MUST contain encrypted information that allows
the retry service to validate the client's IP address, in accordance
with the QUIC specification. It MUST also encode a secure hash of
the original destination connection ID field to verify that this
field has not been edited.
Upon receipt of an Initial packet with a token that begins with '0',
the retry service MUST validate the token in accordance with the QUIC
specification. It must also verify that the secure hash of the
Connect ID is correct. If incorrect, the token is invalid.
In active mode, the service MUST issue Retry packets for all Client
initial packets that contain no token, or a token that has the first
bit set to '1'. It MUST NOT forward the packet to the server. The
service MUST validate all tokens with the first bit set to '0'. If
successful, the service MUST forward the packet with the token
intact. If unsuccessful, it MUST drop the packet.
Note that this scheme has a performance drawback. When the retry
service is in active mode, clients with a token from a NEW_TOKEN
frame will suffer a 1-RTT penalty even though it has proof of address
with its token.
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In inactive mode, the service MUST forward all packets that have no
token or a token with the first bit set to '1'. It MUST validate all
tokens with the first bit set to '0'. If successful, the service
MUST forward the packet with the token intact. If unsuccessful, it
MUST either drop the packet or forward it with the token removed.
The latter requires decryption and re-encryption of the entire
Initial packet to avoid authentication failure. Forwarding the
packet causes the server to respond without the
original_connection_id transport parameter, which preserves the
normal QUIC signal to the client that there is an unauthorized man in
the middle.
5.2.2. Server Requirements
A server behind a non-shared-state retry service MUST NOT send Retry
packets.
Tokens sent in NEW_TOKEN frames MUST have the first bit be set to
'1'.
If a server receives an Initial Packet with the first bit set to '1',
it could be from a server-generated NEW_TOKEN frame and should be
processed in accordance with the QUIC specification. If a server
receives an Initial Packet with the first bit to '0', it is a Retry
token and the server MUST NOT attempt to validate it. Instead, it
MUST assume the address is validated and MUST extract the Original
Destination Connection ID, assuming the format described in
Section 5.2.1.
5.3. Shared-State Retry Service
A shared-state retry service uses a shared key, so that the server
can decode the service's retry tokens. It does not require that all
traffic pass through the Retry service, so servers MAY send Retry
packets in response to Initial packets that don't include a valid
token.
Both server and service must have access to Universal time, though
tight synchronization is not necessary.
All tokens, generated by either the server or retry service, MUST use
the following format. This format is the cleartext version. On the
wire, these fields are encrypted using an AES-ECB cipher and the
token key. If the token is not a multiple of 16 octets, the last
block is padded with zeroes.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ODCIL | Original Destination Connection ID (0..160) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Client IP Address (128) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ +
| date-time (160) |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Data (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Cleartext format of shared-state retry tokens
The tokens have the following fields:
ODCIL: The original destination connection ID length. Tokens in
NEW_TOKEN frames SHOULD set this field to zero.
Original Destination Connection ID: This is copied from the field in
the client Initial packet.
Client IP Address: The source IP address from the triggering Initial
packet. The client IP address is 16 octets. If an IPv4 address, the
last 12 octets are zeroes.
date-time: The date-time string is a total of 20 octets and encodes
the time the token was generated. The format of date-time is
described in Section 5.6 of [RFC3339]. This ASCII field MUST use the
"Z" character for time-offset.
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Opaque Data: The server may use this field to encode additional
information, such as congestion window, RTT, or MTU. Opaque data
SHOULD also allow servers to distinguish between retry tokens (which
trigger use of the original_connection_id transport parameter) and
NEW_TOKEN frame tokens.
5.3.1. Service Requirements
The service MUST share a "token key" with all supported servers.
When in active mode, the service MUST generate Retry tokens with the
format described above when it receives a client Initial packet with
no token.
In active mode, the service SHOULD decrypt incoming tokens. The
service SHOULD drop packets with an IP address that does not match,
and SHOULD forward packets that do, regardless of the other fields.
In inactive mode, the service SHOULD forward all packets to the
server so that the server can issue an up-to-date token to the
client.
5.3.2. Server Requirements
The server MUST validate all tokens that arrive in Initial packets,
as they may have bypassed the Retry service. It SHOULD use the date-
time field to apply its expiration limits for tokens. This need not
be synchronized with the retry service. However, servers MAY allow
retry tokens marked as being a few seconds in the future, due to
possible clock synchronization issues.
A server MUST NOT send a Retry packet in response to an Initial
packet that contains a retry token.
6. Configuration Requirements
QUIC-LB strives to minimize the configuration load to enable, as much
as possible, a "plug-and-play" model. However, there are some
configuration requirements based on algorithm and protocol choices
above.
If there is any in-band communication, servers MUST be explicitly
configured with the token of the load balancer they expect to
interface with.
The load balancer and server MUST agree on a routing algorithm and
the relevant parameters for that algorithm.
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For Plaintext CID Routing, this consists of the Server ID and the
routing bytes. The Server ID is unique to each server, and the
routing bytes are global.
For Obfuscated CID Routing, this consists of the Routing Bits,
Divisor, and Modulus. The Modulus is unique to each server, but the
others MUST be global.
For Stream Cipher CID Routing, this consists of the Server ID, Server
ID Length, Key, and Nonce Length. The Server ID is unique to each
server, but the others MUST be global. The authentication token MUST
be distributed out of band for this algorithm to operate.
For Block Cipher CID Routing, this consists of the Server ID, Server
ID Length, Key, and Zero-Padding Length. The Server ID is unique to
each server, but the others MUST be global.
A full QUIC-LB configuration MUST also specify the information
content of the first CID octet and the presence and mode of any Retry
Service.
The following pseudocode depicts the data items necessary to store a
full QUIC-LB configuration at the server. It is meant to describe
the conceptual range and not specify the presentation of such
configuration in an internet packet. The comments signify the range
of acceptable values where applicable.
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uint2 config_rotation_bits;
enum { in_band_config, out_of_band_config } config_method;
select (config_method) {
case in_band_config: uint64 config_token;
case out_of_band_config: null;
} config-method
boolean first_octet_encodes_cid_length;
enum { none, non_shared_state, shared_state } retry_service;
select (retry_service) {
case none: null;
case non_shared_state: null;
case shared_state: uint8 key[16];
} retry_service_config;
enum { none, plaintext, obfuscated, stream_cipher, block_cipher }
routing_algorithm;
select (routing_algorithm) {
case none: null;
case plaintext: struct {
uint8 server_id_length; /* 1..19 */
uint8 server_id[server_id_length];
} plaintext_config;
case obfuscated: struct {
uint8 routing_bit_mask[19];
uint16 divisor; /* Must be odd */
uint16 modulus; /* 0..(divisor - 1) */
} obfuscated_config;
case stream_cipher: struct {
uint8 nonce_length; /* 8..16 */
uint8 server_id_length; /* 1..(19 - nonce_length) */
uint8 server_id[server_id_length];
uint8 key[16];
} stream_cipher_config;
case block_cipher: struct {
uint8 server_id_length;
uint8 zero_padding_length; /* 0..(16 - server_id_length) */
uint8 server_id[server_id_length];
uint8 key[16];
} block_cipher_config;
} routing_algorithm_config;
This specification allows for out-of-band dissemination of this
configuration items, but also provides an in-band method for
deployment models that need it.
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7. Protocol Description
There are multiple means of configuration that correspond to
differing deployment models and increasing levels of concern about
the security of the load balancer-server path.
7.1. Out of band sharing
When there are concerns about the integrity of the path between load
balancer and server, operators MAY share routing information using an
out-of-band technique, which is out of the scope of this
specification.
To simplify configuration, the global parameters can be shared out-
of-band, while the load balancer sends the unique server IDs via the
truncated message formats presented below.
7.2. QUIC-LB Message Exchange
QUIC-LB load balancers and servers exchange messages via the QUIC-
LBv1 protocol, which uses the QUIC invariants with version number
0xF1000000. The QUIC-LB load balancers send the encoding parameters
to servers and periodically retransmit until that server responds
with an acknowledgement. Specifics of this retransmission are
implementation-dependent.
7.3. QUIC-LB Packet
A QUIC-LB packet uses a long header. It carries configuration
information from the load balancer and acknowledgements from the
servers. They are sent when a load balancer boots up, detects a new
server in the pool or needs to update the server configuration.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+
|1|C R| Reserved|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version (32) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x00 | 0x00 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Authentication Token (64) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type |
+-+-+-+-+-+-+-+-+
Figure 7: QUIC-LB Packet Format
The Version field allows QUIC-LB to use the Version Negotiation
mechanism. All messages in this specification are specific to QUIC-
LBv1. It should be set to 0xF1000000.
Load balancers MUST cease sending QUIC-LB packets of this version to
a server when that server sends a Version Negotiation packet that
does not advertise the version.
The length of the DCIL and SCIL fields are 0x00.
CR The 2-bit CR field indicates the Config Rotation described in
Section 3.1.
Authentication Token The Authentication Token is an 8-byte field
that both entities obtain at configuration time. It is used to
verify that the sender is not an inside off-path attacker.
Servers and load balancers SHOULD silently discard QUIC-LB packets
with an incorrect token.
Message Type The Message Type indicates the type of message payload
that follows the QUIC-LB header.
7.4. Message Types and Formats
As described in Section 7.3, QUIC-LB packets contain a single
message. This section describes the format and semantics of the
QUIC-LB message types.
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7.4.1. ACK_LB Message
A server uses the ACK_LB message (type=0x00) to acknowledge a QUIC-LB
packet received from the load balancer. The ACK-LB message has no
additional payload beyond the QUIC-LB packet header.
Load balancers SHOULD continue to retransmit a QUIC-LB packet until a
valid ACK_LB message, FAIL message or Version Negotiation Packet is
received from the server.
7.4.2. FAIL Message
A server uses the FAIL message (type=0x01) to indicate the
configuration received from the load balancer is unsupported.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Supp. Type | Supp. Type | ...
+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Servers MUST send a FAIL message upon receipt of a message type which
they do not support, or if they do not possess all of the implied
out-of-band configuration to support a particular message type.
The payload of the FAIL message consists of a list of all the message
types supported by the server.
Upon receipt of a FAIL message, Load Balancers MUST either send a
QUIC-LB message the server supports or remove the server from the
server pool.
7.4.3. ROUTING_INFO Message
A load balancer uses the ROUTING_INFO message (type=0x02) to exchange
all the parameters for the Obfuscated CID algorithm.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Routing Bit Mask (152) +
| |
+ +
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Modulus (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Divisor (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Routing Bit Mask The Routing Bit Mask encodes a '1' at every bit
position in the server connection ID that will encode routing
information.
These bits, along with the Modulus and Divisor, are chosen by the
load balancer as described in Section 4.2.
7.4.4. STREAM_CID Message
A load balancer uses the STREAM_CID message (type=0x03) to exchange
all the parameters for using Stream Cipher CIDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nonce Len (8) | SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Key (128) +
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Stream CID Payload
Nonce Len The Nonce Len field is a one-octet unsigned integer that
describes the nonce length necessary to use this routing
algorithm, in octets.
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SIDL The SIDL field is a one-octet unsigned integer that describes
the server ID length necessary to use this routing algorithm, in
octets.
Server ID The Server ID is the unique value assigned to the
receiving server. Its length is determined by the SIDL field.
Key The Key is an 16-octet field that contains the key that the load
balancer will use to decrypt server IDs on QUIC packets. See
Section 8 to understand why sending keys in plaintext may be a
safe strategy.
7.4.5. BLOCK_CID Message
A load balancer uses the BLOCK_CID message (type=0x04) to exchange
all the parameters for using Stream Cipher CIDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ZP Len (8) | SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Key (128) +
| |
+ +
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Block CID Payload
ZP Len The ZP Len field is a one-octet unsigned integer that
describes the zero-padding length necessary to use this routing
algorithm, in octets.
SIDL The SIDL field is a one-octet unsigned integer that describes
the server ID length necessary to use this routing algorithm, in
octets.
Server ID The Server ID is the unique value assigned to the
receiving server. Its length is determined by the SIDL field.
Key The Key is an 16-octet field that contains the key that the load
balancer will use to decrypt server IDs on QUIC packets. See
Section 8 to understand why sending keys in plaintext may be a
safe strategy.
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7.4.6. SERVER_ID Message
A load balancer uses the SERVER_ID message (type=0x05) to exchange
explicit server IDs.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIDL (8) | Server ID (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Load balancers send the SERVER_ID message when all global values for
Stream or Block CIDs are sent out-of-band, so that only the server-
unique values must be sent in-band. It also provides all necessary
paramters for Plaintext CIDs. The fields are identical to their
counterparts in the Section 7.4.4 payload.
7.4.7. MODULUS Message
A load balancer uses the MODULUS message (type=0x06) to exchange just
the modulus used in the Obfuscated CID algorithm.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Modulus (16) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Load balancers send the MODULUS when all global values for Obfuscated
CIDs are sent out-of-band, so that only the server-unique values must
be sent in-band. The Modulus field is identical to its counterpart
in the ROUTING_INFO message.
7.4.8. PLAINTEXT Message
A load balancer uses the PLAINTEXT message (type=0x07) to exchange
all parameters needed for the Plaintext CID algorithm.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SIDL (8) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Server ID (variable) +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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The SIDL field indicates the length of the server ID field. The
Server ID field indicates the encoding that represents the
destination server.
7.4.9. RETRY_SERVICE_STATELESS message
A no-shared-state retry service uses this message (type=0x08) to
notify the server of the existence of this service. This message has
no fields.
7.4.10. RETRY_SERVICE_STATEFUL message
A shared-state retry service uses this message (type=0x09) to tell
the server about its existence, and share the key needed to decrypt
server-generated retry tokens.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Key (128) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8. Security Considerations
QUIC-LB is intended to preserve routability and prevent linkability.
Attacks on the protocol would compromise at least one of these
objectives.
Note that the Plaintext CID algorithm makes no attempt to obscure the
server mapping, and therefore does not address these concerns. It
exists to allow consistent CID encoding for compatibility across a
network infrastructure. Servers that are running the Plaintext CID
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. Doing so might falsely suggest to the client that said CIDs
were generated in a secure fashion.
A routability attack would inject QUIC-LB messages so that load
balancers incorrectly route QUIC connections.
A linkability attack would find some means of determining that two
connection IDs route to the same server. As described above, there
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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. Outside attackers
For an outside attacker to break routability, it must inject packets
that correctly guess the 64-bit token, and servers must be reachable
from these outside hosts. Load balancers SHOULD drop QUIC-LB packets
that arrive on its external interface.
Off-path outside attackers cannot observe connection IDs, and will
therefore struggle to link them.
On-path outside attackers might try to link connection IDs to the
same QUIC connection. The Encrypted CID algorithm provides robust
entropy to making any sort of linkage. The Obfuscated CID obscures
the mapping and prevents trivial brute-force attacks to determine the
routing parameters, but does not provide robust protection against
sophisticated attacks.
8.2. Inside Attackers
As described above, on-path inside attackers 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.
On-path inside attackers can break routability for new and migrating
connections by copying the token from QUIC-LB messages. From this
privileged position, however, there are many other attacks that can
break QUIC connections to the server during the handshake.
Off-path inside attackers cannot observe connection IDs to link them.
To successfully break routability, they must correctly guess the
token.
9. IANA Considerations
There are no IANA requirements.
10. References
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10.1. Normative References
[QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic-
transport (work in progress).
[RFC3339] Klyne, G. and C. Newman, "Date and Time on the Internet:
Timestamps", RFC 3339, DOI 10.17487/RFC3339, July 2002,
<https://www.rfc-editor.org/info/rfc3339>.
10.2. Informative References
[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>.
Appendix A. Acknowledgments
Appendix B. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
B.1. Since draft-duke-quic-load-balancers-05
o Editorial changes
o Made load balancer behavior independent of QUIC version
o Got rid of token in stream cipher encoding, because server might
not have it
o Defined "non-compliant DCID" and specified rules for handling
them.
o Added psuedocode for config schema
B.2. Since draft-duke-quic-load-balancers-04
o Added standard for retry services
B.3. Since draft-duke-quic-load-balancers-03
o Renamed Plaintext CID algorithm as Obfuscated CID
o Added new Plaintext CID algorithm
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Internet-Draft QUIC-LB November 2019
o Updated to allow 20B CIDs
o Added self-encoding of CID length
B.4. Since draft-duke-quic-load-balancers-02
o Added Config Rotation
o Added failover mode
o Tweaks to existing CID algorithms
o Added Block Cipher CID algorithm
o Reformatted QUIC-LB packets
B.5. Since draft-duke-quic-load-balancers-01
o Complete rewrite
o Supports multiple security levels
o Lightweight messages
B.6. Since draft-duke-quic-load-balancers-00
o Converted to markdown
o Added variable length connection IDs
Authors' Addresses
Martin Duke
F5 Networks, Inc.
Email: martin.h.duke@gmail.com
Nick Banks
Microsoft
Email: nibanks@microsoft.com
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