QUIC M. Thomson, Ed.
Internet-Draft Mozilla
Intended status: Standards Track S. Turner, Ed.
Expires: March 15, 2020 sn3rd
September 12, 2019
Using TLS to Secure QUIC
draft-ietf-quic-tls-23
Abstract
This document describes how Transport Layer Security (TLS) is used to
secure QUIC.
Note to Readers
Discussion of this draft takes place on the QUIC working group
mailing list (quic@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/search/?email_list=quic [1].
Working Group information can be found at https://github.com/quicwg
[2]; source code and issues list for this draft can be found at
https://github.com/quicwg/base-drafts/labels/-tls [3].
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/.
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 March 15, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 4
2.1. TLS Overview . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 6
4. Carrying TLS Messages . . . . . . . . . . . . . . . . . . . . 8
4.1. Interface to TLS . . . . . . . . . . . . . . . . . . . . 9
4.1.1. Handshake Complete . . . . . . . . . . . . . . . . . 10
4.1.2. Handshake Confirmed . . . . . . . . . . . . . . . . . 10
4.1.3. Sending and Receiving Handshake Messages . . . . . . 10
4.1.4. Encryption Level Changes . . . . . . . . . . . . . . 12
4.1.5. TLS Interface Summary . . . . . . . . . . . . . . . . 13
4.2. TLS Version . . . . . . . . . . . . . . . . . . . . . . . 14
4.3. ClientHello Size . . . . . . . . . . . . . . . . . . . . 14
4.4. Peer Authentication . . . . . . . . . . . . . . . . . . . 15
4.5. Enabling 0-RTT . . . . . . . . . . . . . . . . . . . . . 15
4.6. Accepting and Rejecting 0-RTT . . . . . . . . . . . . . . 16
4.7. HelloRetryRequest . . . . . . . . . . . . . . . . . . . . 16
4.8. TLS Errors . . . . . . . . . . . . . . . . . . . . . . . 16
4.9. Discarding Unused Keys . . . . . . . . . . . . . . . . . 17
4.9.1. Discarding Initial Keys . . . . . . . . . . . . . . . 17
4.9.2. Discarding Handshake Keys . . . . . . . . . . . . . . 18
4.9.3. Discarding 0-RTT Keys . . . . . . . . . . . . . . . . 18
5. Packet Protection . . . . . . . . . . . . . . . . . . . . . . 18
5.1. Packet Protection Keys . . . . . . . . . . . . . . . . . 18
5.2. Initial Secrets . . . . . . . . . . . . . . . . . . . . . 19
5.3. AEAD Usage . . . . . . . . . . . . . . . . . . . . . . . 20
5.4. Header Protection . . . . . . . . . . . . . . . . . . . . 21
5.4.1. Header Protection Application . . . . . . . . . . . . 22
5.4.2. Header Protection Sample . . . . . . . . . . . . . . 23
5.4.3. AES-Based Header Protection . . . . . . . . . . . . . 24
5.4.4. ChaCha20-Based Header Protection . . . . . . . . . . 25
5.5. Receiving Protected Packets . . . . . . . . . . . . . . . 25
5.6. Use of 0-RTT Keys . . . . . . . . . . . . . . . . . . . . 25
5.7. Receiving Out-of-Order Protected Frames . . . . . . . . . 26
6. Key Update . . . . . . . . . . . . . . . . . . . . . . . . . 27
7. Security of Initial Messages . . . . . . . . . . . . . . . . 29
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8. QUIC-Specific Additions to the TLS Handshake . . . . . . . . 30
8.1. Protocol Negotiation . . . . . . . . . . . . . . . . . . 30
8.2. QUIC Transport Parameters Extension . . . . . . . . . . . 30
8.3. Removing the EndOfEarlyData Message . . . . . . . . . . . 31
9. Security Considerations . . . . . . . . . . . . . . . . . . . 31
9.1. Replay Attacks with 0-RTT . . . . . . . . . . . . . . . . 31
9.2. Packet Reflection Attack Mitigation . . . . . . . . . . . 32
9.3. Header Protection Analysis . . . . . . . . . . . . . . . 33
9.4. Key Diversity . . . . . . . . . . . . . . . . . . . . . . 34
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
11.1. Normative References . . . . . . . . . . . . . . . . . . 34
11.2. Informative References . . . . . . . . . . . . . . . . . 36
11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Appendix A. Sample Initial Packet Protection . . . . . . . . . . 36
A.1. Keys . . . . . . . . . . . . . . . . . . . . . . . . . . 36
A.2. Client Initial . . . . . . . . . . . . . . . . . . . . . 38
A.3. Server Initial . . . . . . . . . . . . . . . . . . . . . 39
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 40
B.1. Since draft-ietf-quic-tls-22 . . . . . . . . . . . . . . 40
B.2. Since draft-ietf-quic-tls-21 . . . . . . . . . . . . . . 40
B.3. Since draft-ietf-quic-tls-20 . . . . . . . . . . . . . . 40
B.4. Since draft-ietf-quic-tls-18 . . . . . . . . . . . . . . 40
B.5. Since draft-ietf-quic-tls-17 . . . . . . . . . . . . . . 41
B.6. Since draft-ietf-quic-tls-14 . . . . . . . . . . . . . . 41
B.7. Since draft-ietf-quic-tls-13 . . . . . . . . . . . . . . 41
B.8. Since draft-ietf-quic-tls-12 . . . . . . . . . . . . . . 41
B.9. Since draft-ietf-quic-tls-11 . . . . . . . . . . . . . . 42
B.10. Since draft-ietf-quic-tls-10 . . . . . . . . . . . . . . 42
B.11. Since draft-ietf-quic-tls-09 . . . . . . . . . . . . . . 42
B.12. Since draft-ietf-quic-tls-08 . . . . . . . . . . . . . . 42
B.13. Since draft-ietf-quic-tls-07 . . . . . . . . . . . . . . 42
B.14. Since draft-ietf-quic-tls-05 . . . . . . . . . . . . . . 42
B.15. Since draft-ietf-quic-tls-04 . . . . . . . . . . . . . . 42
B.16. Since draft-ietf-quic-tls-03 . . . . . . . . . . . . . . 42
B.17. Since draft-ietf-quic-tls-02 . . . . . . . . . . . . . . 42
B.18. Since draft-ietf-quic-tls-01 . . . . . . . . . . . . . . 43
B.19. Since draft-ietf-quic-tls-00 . . . . . . . . . . . . . . 43
B.20. Since draft-thomson-quic-tls-01 . . . . . . . . . . . . . 43
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 44
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction
This document describes how QUIC [QUIC-TRANSPORT] is secured using
TLS [TLS13].
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TLS 1.3 provides critical latency improvements for connection
establishment over previous versions. Absent packet loss, most new
connections can be established and secured within a single round
trip; on subsequent connections between the same client and server,
the client can often send application data immediately, that is,
using a zero round trip setup.
This document describes how TLS acts as a security component of QUIC.
2. Notational Conventions
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 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
This document uses the terminology established in [QUIC-TRANSPORT].
For brevity, the acronym TLS is used to refer to TLS 1.3, though a
newer version could be used (see Section 4.2).
2.1. TLS Overview
TLS provides two endpoints with a way to establish a means of
communication over an untrusted medium (that is, the Internet) that
ensures that messages they exchange cannot be observed, modified, or
forged.
Internally, TLS is a layered protocol, with the structure shown
below:
+--------------+--------------+--------------+
| Handshake | Alerts | Application |
| Layer | | Data |
| | | |
+--------------+--------------+--------------+
| |
| Record Layer |
| |
+--------------------------------------------+
Each upper layer (handshake, alerts, and application data) is carried
as a series of typed TLS records. Records are individually
cryptographically protected and then transmitted over a reliable
transport (typically TCP) which provides sequencing and guaranteed
delivery.
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Change Cipher Spec records cannot be sent in QUIC.
The TLS authenticated key exchange occurs between two entities:
client and server. The client initiates the exchange and the server
responds. If the key exchange completes successfully, both client
and server will agree on a secret. TLS supports both pre-shared key
(PSK) and Diffie-Hellman (DH) key exchanges. PSK is the basis for
0-RTT; the latter provides perfect forward secrecy (PFS) when the DH
keys are destroyed.
After completing the TLS handshake, the client will have learned and
authenticated an identity for the server and the server is optionally
able to learn and authenticate an identity for the client. TLS
supports X.509 [RFC5280] certificate-based authentication for both
server and client.
The TLS key exchange is resistant to tampering by attackers and it
produces shared secrets that cannot be controlled by either
participating peer.
TLS provides two basic handshake modes of interest to QUIC:
o A full 1-RTT handshake in which the client is able to send
application data after one round trip and the server immediately
responds after receiving the first handshake message from the
client.
o A 0-RTT handshake in which the client uses information it has
previously learned about the server to send application data
immediately. This application data can be replayed by an attacker
so it MUST NOT carry a self-contained trigger for any non-
idempotent action.
A simplified TLS handshake with 0-RTT application data is shown in
Figure 1. Note that this omits the EndOfEarlyData message, which is
not used in QUIC (see Section 8.3).
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Client Server
ClientHello
(0-RTT Application Data) -------->
ServerHello
{EncryptedExtensions}
{Finished}
<-------- [Application Data]
{Finished} -------->
[Application Data] <-------> [Application Data]
() Indicates messages protected by early data (0-RTT) keys
{} Indicates messages protected using handshake keys
[] Indicates messages protected using application data
(1-RTT) keys
Figure 1: TLS Handshake with 0-RTT
Data is protected using a number of encryption levels:
o Initial Keys
o Early Data (0-RTT) Keys
o Handshake Keys
o Application Data (1-RTT) Keys
Application data may appear only in the early data and application
data levels. Handshake and Alert messages may appear in any level.
The 0-RTT handshake is only possible if the client and server have
previously communicated. In the 1-RTT handshake, the client is
unable to send protected application data until it has received all
of the handshake messages sent by the server.
3. Protocol Overview
QUIC [QUIC-TRANSPORT] assumes responsibility for the confidentiality
and integrity protection of packets. For this it uses keys derived
from a TLS handshake [TLS13], but instead of carrying TLS records
over QUIC (as with TCP), TLS Handshake and Alert messages are carried
directly over the QUIC transport, which takes over the
responsibilities of the TLS record layer, as shown below.
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+--------------+--------------+ +-------------+
| TLS | TLS | | QUIC |
| Handshake | Alerts | | Applications|
| | | | (h3, etc.) |
+--------------+--------------+-+-------------+
| |
| QUIC Transport |
| (streams, reliability, congestion, etc.) |
| |
+---------------------------------------------+
| |
| QUIC Packet Protection |
| |
+---------------------------------------------+
QUIC also relies on TLS for authentication and negotiation of
parameters that are critical to security and performance.
Rather than a strict layering, these two protocols are co-dependent:
QUIC uses the TLS handshake; TLS uses the reliability, ordered
delivery, and record layer provided by QUIC.
At a high level, there are two main interactions between the TLS and
QUIC components:
o The TLS component sends and receives messages via the QUIC
component, with QUIC providing a reliable stream abstraction to
TLS.
o The TLS component provides a series of updates to the QUIC
component, including (a) new packet protection keys to install (b)
state changes such as handshake completion, the server
certificate, etc.
Figure 2 shows these interactions in more detail, with the QUIC
packet protection being called out specially.
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+------------+ +------------+
| |<- Handshake Messages ->| |
| |<---- 0-RTT Keys -------| |
| |<--- Handshake Keys-----| |
| QUIC |<---- 1-RTT Keys -------| TLS |
| |<--- Handshake Done ----| |
+------------+ +------------+
| ^
| Protect | Protected
v | Packet
+------------+
| QUIC |
| Packet |
| Protection |
+------------+
Figure 2: QUIC and TLS Interactions
Unlike TLS over TCP, QUIC applications which want to send data do not
send it through TLS "application_data" records. Rather, they send it
as QUIC STREAM frames or other frame types which are then carried in
QUIC packets.
4. Carrying TLS Messages
QUIC carries TLS handshake data in CRYPTO frames, each of which
consists of a contiguous block of handshake data identified by an
offset and length. Those frames are packaged into QUIC packets and
encrypted under the current TLS encryption level. As with TLS over
TCP, once TLS handshake data has been delivered to QUIC, it is QUIC's
responsibility to deliver it reliably. Each chunk of data that is
produced by TLS is associated with the set of keys that TLS is
currently using. If QUIC needs to retransmit that data, it MUST use
the same keys even if TLS has already updated to newer keys.
One important difference between TLS records (used with TCP) and QUIC
CRYPTO frames is that in QUIC multiple frames may appear in the same
QUIC packet as long as they are associated with the same encryption
level. For instance, an implementation might bundle a Handshake
message and an ACK for some Handshake data into the same packet.
Some frames are prohibited in different encryption levels, others
cannot be sent. The rules here generalize those of TLS, in that
frames associated with establishing the connection can usually appear
at any encryption level, whereas those associated with transferring
data can only appear in the 0-RTT and 1-RTT encryption levels:
o PADDING frames MAY appear in packets of any encryption level.
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o CRYPTO and CONNECTION_CLOSE frames MAY appear in packets of any
encryption level except 0-RTT.
o ACK frames MAY appear in packets of any encryption level other
than 0-RTT, but can only acknowledge packets which appeared in
that packet number space.
o All other frame types MUST only be sent in the 0-RTT and 1-RTT
levels.
Note that it is not possible to send the following frames in 0-RTT
for various reasons: ACK, CRYPTO, NEW_TOKEN, PATH_RESPONSE, and
RETIRE_CONNECTION_ID.
Because packets could be reordered on the wire, QUIC uses the packet
type to indicate which level a given packet was encrypted under, as
shown in Table 1. When multiple packets of different encryption
levels need to be sent, endpoints SHOULD use coalesced packets to
send them in the same UDP datagram.
+---------------------+------------------+-----------+
| Packet Type | Encryption Level | PN Space |
+---------------------+------------------+-----------+
| Initial | Initial secrets | Initial |
| | | |
| 0-RTT Protected | 0-RTT | 0/1-RTT |
| | | |
| Handshake | Handshake | Handshake |
| | | |
| Retry | N/A | N/A |
| | | |
| Version Negotiation | N/A | N/A |
| | | |
| Short Header | 1-RTT | 0/1-RTT |
+---------------------+------------------+-----------+
Table 1: Encryption Levels by Packet Type
Section 17 of [QUIC-TRANSPORT] shows how packets at the various
encryption levels fit into the handshake process.
4.1. Interface to TLS
As shown in Figure 2, the interface from QUIC to TLS consists of
three primary functions:
o Sending and receiving handshake messages
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o Rekeying (both transmit and receive)
o Handshake state updates
Additional functions might be needed to configure TLS.
4.1.1. Handshake Complete
In this document, the TLS handshake is considered complete when the
TLS stack has reported that the handshake is complete. This happens
when the TLS stack has both sent a Finished message and verified the
peer's Finished message. Verifying the peer's Finished provides the
endpoints with an assurance that previous handshake messages have not
been modified. Note that the handshake does not complete at both
endpoints simultaneously. Consequently, any requirement that is
based on the completion of the handshake depends on the perspective
of the endpoint in question.
4.1.2. Handshake Confirmed
In this document, the TLS handshake is considered confirmed at an
endpoint when the following two conditions are met: the handshake is
complete, and the endpoint has received an acknowledgment for a
packet sent with 1-RTT keys. This second condition can be
implemented by recording the lowest packet number sent with 1-RTT
keys, and the highest value of the Largest Acknowledged field in any
received 1-RTT ACK frame: once the latter is higher than or equal to
the former, the handshake is confirmed.
4.1.3. Sending and Receiving Handshake Messages
In order to drive the handshake, TLS depends on being able to send
and receive handshake messages. There are two basic functions on
this interface: one where QUIC requests handshake messages and one
where QUIC provides handshake packets.
Before starting the handshake QUIC provides TLS with the transport
parameters (see Section 8.2) that it wishes to carry.
A QUIC client starts TLS by requesting TLS handshake bytes from TLS.
The client acquires handshake bytes before sending its first packet.
A QUIC server starts the process by providing TLS with the client's
handshake bytes.
At any given time, the TLS stack at an endpoint will have a current
sending encryption level and receiving encryption level. Each
encryption level is associated with a different flow of bytes, which
is reliably transmitted to the peer in CRYPTO frames. When TLS
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provides handshake bytes to be sent, they are appended to the current
flow and any packet that includes the CRYPTO frame is protected using
keys from the corresponding encryption level.
QUIC takes the unprotected content of TLS handshake records as the
content of CRYPTO frames. TLS record protection is not used by QUIC.
QUIC assembles CRYPTO frames into QUIC packets, which are protected
using QUIC packet protection.
When an endpoint receives a QUIC packet containing a CRYPTO frame
from the network, it proceeds as follows:
o If the packet was in the TLS receiving encryption level, sequence
the data into the input flow as usual. As with STREAM frames, the
offset is used to find the proper location in the data sequence.
If the result of this process is that new data is available, then
it is delivered to TLS in order.
o If the packet is from a previously installed encryption level, it
MUST not contain data which extends past the end of previously
received data in that flow. Implementations MUST treat any
violations of this requirement as a connection error of type
PROTOCOL_VIOLATION.
o If the packet is from a new encryption level, it is saved for
later processing by TLS. Once TLS moves to receiving from this
encryption level, saved data can be provided. When providing data
from any new encryption level to TLS, if there is data from a
previous encryption level that TLS has not consumed, this MUST be
treated as a connection error of type PROTOCOL_VIOLATION.
Each time that TLS is provided with new data, new handshake bytes are
requested from TLS. TLS might not provide any bytes if the handshake
messages it has received are incomplete or it has no data to send.
Once the TLS handshake is complete, this is indicated to QUIC along
with any final handshake bytes that TLS needs to send. TLS also
provides QUIC with the transport parameters that the peer advertised
during the handshake.
Once the handshake is complete, TLS becomes passive. TLS can still
receive data from its peer and respond in kind, but it will not need
to send more data unless specifically requested - either by an
application or QUIC. One reason to send data is that the server
might wish to provide additional or updated session tickets to a
client.
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When the handshake is complete, QUIC only needs to provide TLS with
any data that arrives in CRYPTO streams. In the same way that is
done during the handshake, new data is requested from TLS after
providing received data.
4.1.4. Encryption Level Changes
As keys for new encryption levels become available, TLS provides QUIC
with those keys. Separately, as keys at a given encryption level
become available to TLS, TLS indicates to QUIC that reading or
writing keys at that encryption level are available. These events
are not asynchronous; they always occur immediately after TLS is
provided with new handshake bytes, or after TLS produces handshake
bytes.
TLS provides QUIC with three items as a new encryption level becomes
available:
o A secret
o An Authenticated Encryption with Associated Data (AEAD) function
o A Key Derivation Function (KDF)
These values are based on the values that TLS negotiates and are used
by QUIC to generate packet and header protection keys (see Section 5
and Section 5.4).
If 0-RTT is possible, it is ready after the client sends a TLS
ClientHello message or the server receives that message. After
providing a QUIC client with the first handshake bytes, the TLS stack
might signal the change to 0-RTT keys. On the server, after
receiving handshake bytes that contain a ClientHello message, a TLS
server might signal that 0-RTT keys are available.
Although TLS only uses one encryption level at a time, QUIC may use
more than one level. For instance, after sending its Finished
message (using a CRYPTO frame at the Handshake encryption level) an
endpoint can send STREAM data (in 1-RTT encryption). If the Finished
message is lost, the endpoint uses the Handshake encryption level to
retransmit the lost message. Reordering or loss of packets can mean
that QUIC will need to handle packets at multiple encryption levels.
During the handshake, this means potentially handling packets at
higher and lower encryption levels than the current encryption level
used by TLS.
In particular, server implementations need to be able to read packets
at the Handshake encryption level at the same time as the 0-RTT
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encryption level. A client could interleave ACK frames that are
protected with Handshake keys with 0-RTT data and the server needs to
process those acknowledgments in order to detect lost Handshake
packets.
QUIC also needs access to keys that might not ordinarily be available
to a TLS implementation. For instance, a client might need to
acknowledge Handshake packets before it is ready to send CRYPTO
frames at that encryption level. TLS therefore needs to provide keys
to QUIC before it might produce them for its own use.
4.1.5. TLS Interface Summary
Figure 3 summarizes the exchange between QUIC and TLS for both client
and server. Each arrow is tagged with the encryption level used for
that transmission.
Client Server
Get Handshake
Initial ------------->
Handshake Received
Install tx 0-RTT Keys
0-RTT --------------->
Get Handshake
<------------- Initial
Handshake Received
Install Handshake keys
Install rx 0-RTT keys
Install Handshake keys
Get Handshake
<----------- Handshake
Handshake Received
Install tx 1-RTT keys
<--------------- 1-RTT
Get Handshake
Handshake Complete
Handshake ----------->
Handshake Received
Install rx 1-RTT keys
Handshake Complete
Install 1-RTT keys
1-RTT --------------->
Get Handshake
<--------------- 1-RTT
Handshake Received
Figure 3: Interaction Summary between QUIC and TLS
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Figure 3 shows the multiple packets that form a single "flight" of
messages being processed individually, to show what incoming messages
trigger different actions. New handshake messages are requested
after all incoming packets have been processed. This process might
vary depending on how QUIC implementations and the packets they
receive are structured.
4.2. TLS Version
This document describes how TLS 1.3 [TLS13] is used with QUIC.
In practice, the TLS handshake will negotiate a version of TLS to
use. This could result in a newer version of TLS than 1.3 being
negotiated if both endpoints support that version. This is
acceptable provided that the features of TLS 1.3 that are used by
QUIC are supported by the newer version.
A badly configured TLS implementation could negotiate TLS 1.2 or
another older version of TLS. An endpoint MUST terminate the
connection if a version of TLS older than 1.3 is negotiated.
4.3. ClientHello Size
QUIC requires that the first Initial packet from a client contain an
entire cryptographic handshake message, which for TLS is the
ClientHello. Though a packet larger than 1200 bytes might be
supported by the path, a client improves the likelihood that a packet
is accepted if it ensures that the first ClientHello message is small
enough to stay within this limit.
QUIC packet and framing add at least 36 bytes of overhead to the
ClientHello message. That overhead increases if the client chooses a
connection ID without zero length. Overheads also do not include the
token or a connection ID longer than 8 bytes, both of which might be
required if a server sends a Retry packet.
A typical TLS ClientHello can easily fit into a 1200 byte packet.
However, in addition to the overheads added by QUIC, there are
several variables that could cause this limit to be exceeded. Large
session tickets, multiple or large key shares, and long lists of
supported ciphers, signature algorithms, versions, QUIC transport
parameters, and other negotiable parameters and extensions could
cause this message to grow.
For servers, in addition to connection IDs and tokens, the size of
TLS session tickets can have an effect on a client's ability to
connect. Minimizing the size of these values increases the
probability that they can be successfully used by a client.
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A client is not required to fit the ClientHello that it sends in
response to a HelloRetryRequest message into a single UDP datagram.
The TLS implementation does not need to ensure that the ClientHello
is sufficiently large. QUIC PADDING frames are added to increase the
size of the packet as necessary.
4.4. Peer Authentication
The requirements for authentication depend on the application
protocol that is in use. TLS provides server authentication and
permits the server to request client authentication.
A client MUST authenticate the identity of the server. This
typically involves verification that the identity of the server is
included in a certificate and that the certificate is issued by a
trusted entity (see for example [RFC2818]).
A server MAY request that the client authenticate during the
handshake. A server MAY refuse a connection if the client is unable
to authenticate when requested. The requirements for client
authentication vary based on application protocol and deployment.
A server MUST NOT use post-handshake client authentication (see
Section 4.6.2 of [TLS13]).
4.5. Enabling 0-RTT
In order to be usable for 0-RTT, TLS MUST provide a NewSessionTicket
message that contains the "early_data" extension with a
max_early_data_size of 0xffffffff; the amount of data which the
client can send in 0-RTT is controlled by the "initial_max_data"
transport parameter supplied by the server. A client MUST treat
receipt of a NewSessionTicket that contains an "early_data" extension
with any other value as a connection error of type
PROTOCOL_VIOLATION.
A client that wishes to send 0-RTT packets uses the "early_data"
extension in the ClientHello message of a subsequent handshake (see
Section 4.2.10 of [TLS13]). It then sends the application data in
0-RTT packets.
Early data within the TLS connection MUST NOT be used. As it is for
other TLS application data, a server MUST treat receiving early data
on the TLS connection as a connection error of type
PROTOCOL_VIOLATION.
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4.6. Accepting and Rejecting 0-RTT
A server accepts 0-RTT by sending an early_data extension in the
EncryptedExtensions (see Section 4.2.10 of [TLS13]). The server then
processes and acknowledges the 0-RTT packets that it receives.
A server rejects 0-RTT by sending the EncryptedExtensions without an
early_data extension. A server will always reject 0-RTT if it sends
a TLS HelloRetryRequest. When rejecting 0-RTT, a server MUST NOT
process any 0-RTT packets, even if it could. When 0-RTT was
rejected, a client SHOULD treat receipt of an acknowledgement for a
0-RTT packet as a connection error of type PROTOCOL_VIOLATION, if it
is able to detect the condition.
When 0-RTT is rejected, all connection characteristics that the
client assumed might be incorrect. This includes the choice of
application protocol, transport parameters, and any application
configuration. The client therefore MUST reset the state of all
streams, including application state bound to those streams.
A client MAY attempt to send 0-RTT again if it receives a Retry or
Version Negotiation packet. These packets do not signify rejection
of 0-RTT.
4.7. HelloRetryRequest
In TLS over TCP, the HelloRetryRequest feature (see Section 4.1.4 of
[TLS13]) can be used to correct a client's incorrect KeyShare
extension as well as for a stateless round-trip check. From the
perspective of QUIC, this just looks like additional messages carried
in the Initial encryption level. Although it is in principle
possible to use this feature for address verification in QUIC, QUIC
implementations SHOULD instead use the Retry feature (see Section 8.1
of [QUIC-TRANSPORT]). HelloRetryRequest is still used to request key
shares.
4.8. TLS Errors
If TLS experiences an error, it generates an appropriate alert as
defined in Section 6 of [TLS13].
A TLS alert is turned into a QUIC connection error by converting the
one-byte alert description into a QUIC error code. The alert
description is added to 0x100 to produce a QUIC error code from the
range reserved for CRYPTO_ERROR. The resulting value is sent in a
QUIC CONNECTION_CLOSE frame.
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The alert level of all TLS alerts is "fatal"; a TLS stack MUST NOT
generate alerts at the "warning" level.
4.9. Discarding Unused Keys
After QUIC moves to a new encryption level, packet protection keys
for previous encryption levels can be discarded. This occurs several
times during the handshake, as well as when keys are updated; see
Section 6.
Packet protection keys are not discarded immediately when new keys
are available. If packets from a lower encryption level contain
CRYPTO frames, frames that retransmit that data MUST be sent at the
same encryption level. Similarly, an endpoint generates
acknowledgements for packets at the same encryption level as the
packet being acknowledged. Thus, it is possible that keys for a
lower encryption level are needed for a short time after keys for a
newer encryption level are available.
An endpoint cannot discard keys for a given encryption level unless
it has both received and acknowledged all CRYPTO frames for that
encryption level and when all CRYPTO frames for that encryption level
have been acknowledged by its peer. However, this does not guarantee
that no further packets will need to be received or sent at that
encryption level because a peer might not have received all the
acknowledgements necessary to reach the same state.
Though an endpoint might retain older keys, new data MUST be sent at
the highest currently-available encryption level. Only ACK frames
and retransmissions of data in CRYPTO frames are sent at a previous
encryption level. These packets MAY also include PADDING frames.
4.9.1. Discarding Initial Keys
Packets protected with Initial secrets (Section 5.2) are not
authenticated, meaning that an attacker could spoof packets with the
intent to disrupt a connection. To limit these attacks, Initial
packet protection keys can be discarded more aggressively than other
keys.
The successful use of Handshake packets indicates that no more
Initial packets need to be exchanged, as these keys can only be
produced after receiving all CRYPTO frames from Initial packets.
Thus, a client MUST discard Initial keys when it first sends a
Handshake packet and a server MUST discard Initial keys when it first
successfully processes a Handshake packet. Endpoints MUST NOT send
Initial packets after this point.
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This results in abandoning loss recovery state for the Initial
encryption level and ignoring any outstanding Initial packets.
4.9.2. Discarding Handshake Keys
An endpoint MUST NOT discard its handshake keys until the TLS
handshake is confirmed (Section 4.1.2). An endpoint SHOULD discard
its handshake keys as soon as it has confirmed the handshake. Most
application protocols will send data after the handshake, resulting
in acknowledgements that allow both endpoints to discard their
handshake keys promptly. Endpoints that do not have reason to send
immediately after completing the handshake MAY send ack-eliciting
frames, such as PING, which will cause the handshake to be confirmed
when they are acknowledged.
4.9.3. Discarding 0-RTT Keys
0-RTT and 1-RTT packets share the same packet number space, and
clients do not send 0-RTT packets after sending a 1-RTT packet
(Section 5.6).
Therefore, a client SHOULD discard 0-RTT keys as soon as it installs
1-RTT keys, since they have no use after that moment.
Additionally, a server MAY discard 0-RTT keys as soon as it receives
a 1-RTT packet. However, due to packet reordering, a 0-RTT packet
could arrive after a 1-RTT packet. Servers MAY temporarily retain
0-RTT keys to allow decrypting reordered packets without requiring
their contents to be retransmitted with 1-RTT keys. After receiving
a 1-RTT packet, servers MUST discard 0-RTT keys within a short time;
the RECOMMENDED time period is three times the Probe Timeout (PTO,
see [QUIC-RECOVERY]). A server MAY discard 0-RTT keys earlier if it
determines that it has received all 0-RTT packets, which can be done
by keeping track of missing packet numbers.
5. Packet Protection
As with TLS over TCP, QUIC protects packets with keys derived from
the TLS handshake, using the AEAD algorithm negotiated by TLS.
5.1. Packet Protection Keys
QUIC derives packet protection keys in the same way that TLS derives
record protection keys.
Each encryption level has separate secret values for protection of
packets sent in each direction. These traffic secrets are derived by
TLS (see Section 7.1 of [TLS13]) and are used by QUIC for all
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encryption levels except the Initial encryption level. The secrets
for the Initial encryption level are computed based on the client's
initial Destination Connection ID, as described in Section 5.2.
The keys used for packet protection are computed from the TLS secrets
using the KDF provided by TLS. In TLS 1.3, the HKDF-Expand-Label
function described in Section 7.1 of [TLS13] is used, using the hash
function from the negotiated cipher suite. Other versions of TLS
MUST provide a similar function in order to be used with QUIC.
The current encryption level secret and the label "quic key" are
input to the KDF to produce the AEAD key; the label "quic iv" is used
to derive the IV; see Section 5.3. The header protection key uses
the "quic hp" label; see Section 5.4. Using these labels provides
key separation between QUIC and TLS; see Section 9.4.
The KDF used for initial secrets is always the HKDF-Expand-Label
function from TLS 1.3 (see Section 5.2).
5.2. Initial Secrets
Initial packets are protected with a secret derived from the
Destination Connection ID field from the client's first Initial
packet of the connection. Specifically:
initial_salt = 0xc3eef712c72ebb5a11a7d2432bb46365bef9f502
initial_secret = HKDF-Extract(initial_salt,
client_dst_connection_id)
client_initial_secret = HKDF-Expand-Label(initial_secret,
"client in", "",
Hash.length)
server_initial_secret = HKDF-Expand-Label(initial_secret,
"server in", "",
Hash.length)
The hash function for HKDF when deriving initial secrets and keys is
SHA-256 [SHA].
The connection ID used with HKDF-Expand-Label is the Destination
Connection ID in the Initial packet sent by the client. This will be
a randomly-selected value unless the client creates the Initial
packet after receiving a Retry packet, where the Destination
Connection ID is selected by the server.
The value of initial_salt is a 20 byte sequence shown in the figure
in hexadecimal notation. Future versions of QUIC SHOULD generate a
new salt value, thus ensuring that the keys are different for each
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version of QUIC. This prevents a middlebox that only recognizes one
version of QUIC from seeing or modifying the contents of packets from
future versions.
The HKDF-Expand-Label function defined in TLS 1.3 MUST be used for
Initial packets even where the TLS versions offered do not include
TLS 1.3.
Appendix A contains test vectors for the initial packet encryption.
Note: The Destination Connection ID is of arbitrary length, and it
could be zero length if the server sends a Retry packet with a
zero-length Source Connection ID field. In this case, the Initial
keys provide no assurance to the client that the server received
its packet; the client has to rely on the exchange that included
the Retry packet for that property.
5.3. AEAD Usage
The Authentication Encryption with Associated Data (AEAD) [AEAD]
function used for QUIC packet protection is the AEAD that is
negotiated for use with the TLS connection. For example, if TLS is
using the TLS_AES_128_GCM_SHA256, the AEAD_AES_128_GCM function is
used.
Packets are protected prior to applying header protection
(Section 5.4). The unprotected packet header is part of the
associated data (A). When removing packet protection, an endpoint
first removes the header protection.
All QUIC packets other than Version Negotiation and Retry packets are
protected with an AEAD algorithm [AEAD]. Prior to establishing a
shared secret, packets are protected with AEAD_AES_128_GCM and a key
derived from the Destination Connection ID in the client's first
Initial packet (see Section 5.2). This provides protection against
off-path attackers and robustness against QUIC version unaware
middleboxes, but not against on-path attackers.
QUIC can use any of the ciphersuites defined in [TLS13] with the
exception of TLS_AES_128_CCM_8_SHA256. A ciphersuite MUST NOT be
negotiated unless a header protection scheme is defined for the
ciphersuite. This document defines a header protection scheme for
all ciphersuites defined in [TLS13] aside from
TLS_AES_128_CCM_8_SHA256. These ciphersuites have a 16-byte
authentication tag and produce an output 16 bytes larger than their
input.
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Note: An endpoint MUST NOT reject a ClientHello that offers a
ciphersuite that it does not support, or it would be impossible to
deploy a new ciphersuite. This also applies to
TLS_AES_128_CCM_8_SHA256.
The key and IV for the packet are computed as described in
Section 5.1. The nonce, N, is formed by combining the packet
protection IV with the packet number. The 62 bits of the
reconstructed QUIC packet number in network byte order are left-
padded with zeros to the size of the IV. The exclusive OR of the
padded packet number and the IV forms the AEAD nonce.
The associated data, A, for the AEAD is the contents of the QUIC
header, starting from the flags byte in either the short or long
header, up to and including the unprotected packet number.
The input plaintext, P, for the AEAD is the payload of the QUIC
packet, as described in [QUIC-TRANSPORT].
The output ciphertext, C, of the AEAD is transmitted in place of P.
Some AEAD functions have limits for how many packets can be encrypted
under the same key and IV (see for example [AEBounds]). This might
be lower than the packet number limit. An endpoint MUST initiate a
key update (Section 6) prior to exceeding any limit set for the AEAD
that is in use.
5.4. Header Protection
Parts of QUIC packet headers, in particular the Packet Number field,
are protected using a key that is derived separate to the packet
protection key and IV. The key derived using the "quic hp" label is
used to provide confidentiality protection for those fields that are
not exposed to on-path elements.
This protection applies to the least-significant bits of the first
byte, plus the Packet Number field. The four least-significant bits
of the first byte are protected for packets with long headers; the
five least significant bits of the first byte are protected for
packets with short headers. For both header forms, this covers the
reserved bits and the Packet Number Length field; the Key Phase bit
is also protected for packets with a short header.
The same header protection key is used for the duration of the
connection, with the value not changing after a key update (see
Section 6). This allows header protection to be used to protect the
key phase.
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This process does not apply to Retry or Version Negotiation packets,
which do not contain a protected payload or any of the fields that
are protected by this process.
5.4.1. Header Protection Application
Header protection is applied after packet protection is applied (see
Section 5.3). The ciphertext of the packet is sampled and used as
input to an encryption algorithm. The algorithm used depends on the
negotiated AEAD.
The output of this algorithm is a 5 byte mask which is applied to the
protected header fields using exclusive OR. The least significant
bits of the first byte of the packet are masked by the least
significant bits of the first mask byte, and the packet number is
masked with the remaining bytes. Any unused bytes of mask that might
result from a shorter packet number encoding are unused.
Figure 4 shows a sample algorithm for applying header protection.
Removing header protection only differs in the order in which the
packet number length (pn_length) is determined.
mask = header_protection(hp_key, sample)
pn_length = (packet[0] & 0x03) + 1
if (packet[0] & 0x80) == 0x80:
# Long header: 4 bits masked
packet[0] ^= mask[0] & 0x0f
else:
# Short header: 5 bits masked
packet[0] ^= mask[0] & 0x1f
# pn_offset is the start of the Packet Number field.
packet[pn_offset:pn_offset+pn_length] ^= mask[1:1+pn_length]
Figure 4: Header Protection Pseudocode
Figure 5 shows the protected fields of long and short headers marked
with an E. Figure 5 also shows the sampled fields.
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Long Header:
+-+-+-+-+-+-+-+-+
|1|1|T T|E E E E|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version -> Length Fields ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Short Header:
+-+-+-+-+-+-+-+-+
|0|1|S|E E E E E|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Connection ID (0/32..144) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Common Fields:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|E E E E E E E E E Packet Number (8/16/24/32) E E E E E E E E...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| [Protected Payload (8/16/24)] ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sampled part of Protected Payload (128) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protected Payload Remainder (*) ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Header Protection and Ciphertext Sample
Before a TLS ciphersuite can be used with QUIC, a header protection
algorithm MUST be specified for the AEAD used with that ciphersuite.
This document defines algorithms for AEAD_AES_128_GCM,
AEAD_AES_128_CCM, AEAD_AES_256_GCM (all AES AEADs are defined in
[AEAD]), and AEAD_CHACHA20_POLY1305 [CHACHA]. Prior to TLS selecting
a ciphersuite, AES header protection is used (Section 5.4.3),
matching the AEAD_AES_128_GCM packet protection.
5.4.2. Header Protection Sample
The header protection algorithm uses both the header protection key
and a sample of the ciphertext from the packet Payload field.
The same number of bytes are always sampled, but an allowance needs
to be made for the endpoint removing protection, which will not know
the length of the Packet Number field. In sampling the packet
ciphertext, the Packet Number field is assumed to be 4 bytes long
(its maximum possible encoded length).
An endpoint MUST discard packets that are not long enough to contain
a complete sample.
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To ensure that sufficient data is available for sampling, packets are
padded so that the combined lengths of the encoded packet number and
protected payload is at least 4 bytes longer than the sample required
for header protection. The ciphersuites defined in [TLS13] - other
than TLS_AES_128_CCM_8_SHA256, for which a header protection scheme
is not defined in this document - have 16-byte expansions and 16-byte
header protection samples. This results in needing at least 3 bytes
of frames in the unprotected payload if the packet number is encoded
on a single byte, or 2 bytes of frames for a 2-byte packet number
encoding.
The sampled ciphertext for a packet with a short header can be
determined by the following pseudocode:
sample_offset = 1 + len(connection_id) + 4
sample = packet[sample_offset..sample_offset+sample_length]
For example, for a packet with a short header, an 8 byte connection
ID, and protected with AEAD_AES_128_GCM, the sample takes bytes 13 to
28 inclusive (using zero-based indexing).
A packet with a long header is sampled in the same way, noting that
multiple QUIC packets might be included in the same UDP datagram and
that each one is handled separately.
sample_offset = 7 + len(destination_connection_id) +
len(source_connection_id) +
len(payload_length) + 4
if packet_type == Initial:
sample_offset += len(token_length) +
len(token)
sample = packet[sample_offset..sample_offset+sample_length]
5.4.3. AES-Based Header Protection
This section defines the packet protection algorithm for
AEAD_AES_128_GCM, AEAD_AES_128_CCM, and AEAD_AES_256_GCM.
AEAD_AES_128_GCM and AEAD_AES_128_CCM use 128-bit AES [AES] in
electronic code-book (ECB) mode. AEAD_AES_256_GCM uses 256-bit AES
in ECB mode.
This algorithm samples 16 bytes from the packet ciphertext. This
value is used as the input to AES-ECB. In pseudocode:
mask = AES-ECB(hp_key, sample)
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5.4.4. ChaCha20-Based Header Protection
When AEAD_CHACHA20_POLY1305 is in use, header protection uses the raw
ChaCha20 function as defined in Section 2.4 of [CHACHA]. This uses a
256-bit key and 16 bytes sampled from the packet protection output.
The first 4 bytes of the sampled ciphertext are the block counter. A
ChaCha20 implementation could take a 32-bit integer in place of a
byte sequence, in which case the byte sequence is interpreted as a
little-endian value.
The remaining 12 bytes are used as the nonce. A ChaCha20
implementation might take an array of three 32-bit integers in place
of a byte sequence, in which case the nonce bytes are interpreted as
a sequence of 32-bit little-endian integers.
The encryption mask is produced by invoking ChaCha20 to protect 5
zero bytes. In pseudocode:
counter = sample[0..3]
nonce = sample[4..15]
mask = ChaCha20(hp_key, counter, nonce, {0,0,0,0,0})
5.5. Receiving Protected Packets
Once an endpoint successfully receives a packet with a given packet
number, it MUST discard all packets in the same packet number space
with higher packet numbers if they cannot be successfully unprotected
with either the same key, or - if there is a key update - the next
packet protection key (see Section 6). Similarly, a packet that
appears to trigger a key update, but cannot be unprotected
successfully MUST be discarded.
Failure to unprotect a packet does not necessarily indicate the
existence of a protocol error in a peer or an attack. The truncated
packet number encoding used in QUIC can cause packet numbers to be
decoded incorrectly if they are delayed significantly.
5.6. Use of 0-RTT Keys
If 0-RTT keys are available (see Section 4.5), the lack of replay
protection means that restrictions on their use are necessary to
avoid replay attacks on the protocol.
A client MUST only use 0-RTT keys to protect data that is idempotent.
A client MAY wish to apply additional restrictions on what data it
sends prior to the completion of the TLS handshake. A client
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otherwise treats 0-RTT keys as equivalent to 1-RTT keys, except that
it MUST NOT send ACKs with 0-RTT keys.
A client that receives an indication that its 0-RTT data has been
accepted by a server can send 0-RTT data until it receives all of the
server's handshake messages. A client SHOULD stop sending 0-RTT data
if it receives an indication that 0-RTT data has been rejected.
A server MUST NOT use 0-RTT keys to protect packets; it uses 1-RTT
keys to protect acknowledgements of 0-RTT packets. A client MUST NOT
attempt to decrypt 0-RTT packets it receives and instead MUST discard
them.
Once a client has installed 1-RTT keys, it MUST NOT send any more
0-RTT packets.
Note: 0-RTT data can be acknowledged by the server as it receives
it, but any packets containing acknowledgments of 0-RTT data
cannot have packet protection removed by the client until the TLS
handshake is complete. The 1-RTT keys necessary to remove packet
protection cannot be derived until the client receives all server
handshake messages.
5.7. Receiving Out-of-Order Protected Frames
Due to reordering and loss, protected packets might be received by an
endpoint before the final TLS handshake messages are received. A
client will be unable to decrypt 1-RTT packets from the server,
whereas a server will be able to decrypt 1-RTT packets from the
client.
Even though 1-RTT keys are available to a server after receiving the
first handshake messages from a client, it is missing assurances on
the client state:
o The client is not authenticated, unless the server has chosen to
use a pre-shared key and validated the client's pre-shared key
binder; see Section 4.2.11 of [TLS13].
o The client has not demonstrated liveness, unless a RETRY packet
was used.
o Any received 0-RTT data that the server responds to might be due
to a replay attack.
Therefore, the server's use of 1-RTT keys is limited before the
handshake is complete. A server MUST NOT process data from incoming
1-RTT protected packets before the TLS handshake is complete.
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Because sending acknowledgments indicates that all frames in a packet
have been processed, a server cannot send acknowledgments for 1-RTT
packets until the TLS handshake is complete. Received packets
protected with 1-RTT keys MAY be stored and later decrypted and used
once the handshake is complete.
The requirement for the server to wait for the client Finished
message creates a dependency on that message being delivered. A
client can avoid the potential for head-of-line blocking that this
implies by sending its 1-RTT packets coalesced with a handshake
packet containing a copy of the CRYPTO frame that carries the
Finished message, until one of the handshake packets is acknowledged.
This enables immediate server processing for those packets.
A server could receive packets protected with 0-RTT keys prior to
receiving a TLS ClientHello. The server MAY retain these packets for
later decryption in anticipation of receiving a ClientHello.
6. Key Update
Once the handshake is confirmed, it is possible to update the keys.
The KEY_PHASE bit in the short header is used to indicate whether key
updates have occurred. The KEY_PHASE bit is initially set to 0 and
then inverted with each key update.
The KEY_PHASE bit allows a recipient to detect a change in keying
material without necessarily needing to receive the first packet that
triggered the change. An endpoint that notices a changed KEY_PHASE
bit can update keys and decrypt the packet that contains the changed
bit.
This mechanism replaces the TLS KeyUpdate message. Endpoints MUST
NOT send a TLS KeyUpdate message. Endpoints MUST treat the receipt
of a TLS KeyUpdate message as a connection error of type 0x10a,
equivalent to a fatal TLS alert of unexpected_message (see
Section 4.8).
An endpoint MUST NOT initiate the first key update until the
handshake is confirmed (Section 4.1.2). An endpoint MUST NOT
initiate a subsequent key update until it has received an
acknowledgment for a packet sent at the current KEY_PHASE. This can
be implemented by tracking the lowest packet number sent with each
KEY_PHASE, and the highest acknowledged packet number in the 1-RTT
space: once the latter is higher than or equal to the former, another
key update can be initiated.
Endpoints MAY limit the number of keys they retain to two sets for
removing packet protection and one set for protecting packets. Older
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keys can be discarded. Updating keys multiple times rapidly can
cause packets to be effectively lost if packets are significantly
reordered. Therefore, an endpoint SHOULD NOT initiate a key update
for some time after it has last updated keys; the RECOMMENDED time
period is three times the PTO. This avoids valid reordered packets
being dropped by the peer as a result of the peer discarding older
keys.
A receiving endpoint detects an update when the KEY_PHASE bit does
not match what it is expecting. It creates a new secret (see
Section 7.2 of [TLS13]) and the corresponding read key and IV using
the KDF function provided by TLS. The header protection key is not
updated.
If the packet can be decrypted and authenticated using the updated
key and IV, then the keys the endpoint uses for packet protection are
also updated. The next packet sent by the endpoint MUST then use the
new keys. Once an endpoint has sent a packet encrypted with a given
key phase, it MUST NOT send a packet encrypted with an older key
phase.
An endpoint does not always need to send packets when it detects that
its peer has updated keys. The next packet that it sends will simply
use the new keys. If an endpoint detects a second update before it
has sent any packets with updated keys, it indicates that its peer
has updated keys twice without awaiting a reciprocal update. An
endpoint MUST treat consecutive key updates as a fatal error and
abort the connection.
An endpoint SHOULD retain old keys for a period of no more than three
times the PTO. After this period, old keys and their corresponding
secrets SHOULD be discarded. Retaining keys allow endpoints to
process packets that were sent with old keys and delayed in the
network. Packets with higher packet numbers always use the updated
keys and MUST NOT be decrypted with old keys.
This ensures that once the handshake is complete, packets with the
same KEY_PHASE will have the same packet protection keys, unless
there are multiple key updates in a short time frame succession and
significant packet reordering.
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Initiating Peer Responding Peer
@M QUIC Frames
New Keys -> @N
@N QUIC Frames
-------->
QUIC Frames @M
New Keys -> @N
QUIC Frames @N
<--------
Figure 6: Key Update
A packet that triggers a key update could arrive after the receiving
endpoint successfully processed a packet with a higher packet number.
This is only possible if there is a key compromise and an attack, or
if the peer is incorrectly reverting to use of old keys. Because the
latter cannot be differentiated from an attack, an endpoint MUST
immediately terminate the connection if it detects this condition.
In deciding when to update keys, endpoints MUST NOT exceed the limits
for use of specific keys, as described in Section 5.5 of [TLS13].
7. Security of Initial Messages
Initial packets are not protected with a secret key, so they are
subject to potential tampering by an attacker. QUIC provides
protection against attackers that cannot read packets, but does not
attempt to provide additional protection against attacks where the
attacker can observe and inject packets. Some forms of tampering -
such as modifying the TLS messages themselves - are detectable, but
some - such as modifying ACKs - are not.
For example, an attacker could inject a packet containing an ACK
frame that makes it appear that a packet had not been received or to
create a false impression of the state of the connection (e.g., by
modifying the ACK Delay). Note that such a packet could cause a
legitimate packet to be dropped as a duplicate. Implementations
SHOULD use caution in relying on any data which is contained in
Initial packets that is not otherwise authenticated.
It is also possible for the attacker to tamper with data that is
carried in Handshake packets, but because that tampering requires
modifying TLS handshake messages, that tampering will cause the TLS
handshake to fail.
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8. QUIC-Specific Additions to the TLS Handshake
QUIC uses the TLS handshake for more than just negotiation of
cryptographic parameters. The TLS handshake provides preliminary
values for QUIC transport parameters and allows a server to perform
return routability checks on clients.
8.1. Protocol Negotiation
QUIC requires that the cryptographic handshake provide authenticated
protocol negotiation. TLS uses Application Layer Protocol
Negotiation (ALPN) [RFC7301] to select an application protocol.
Unless another mechanism is used for agreeing on an application
protocol, endpoints MUST use ALPN for this purpose. When using ALPN,
endpoints MUST immediately close a connection (see Section 10.3 in
[QUIC-TRANSPORT]) if an application protocol is not negotiated with a
no_application_protocol TLS alert (QUIC error code 0x178, see
Section 4.8). While [RFC7301] only specifies that servers use this
alert, QUIC clients MUST also use it to terminate a connection when
ALPN negotiation fails.
An application-layer protocol MAY restrict the QUIC versions that it
can operate over. Servers MUST select an application protocol
compatible with the QUIC version that the client has selected. If
the server cannot select a compatible combination of application
protocol and QUIC version, it MUST abort the connection. A client
MUST abort a connection if the server picks an application protocol
incompatible with the protocol version being used.
8.2. QUIC Transport Parameters Extension
QUIC transport parameters are carried in a TLS extension. Different
versions of QUIC might define a different format for this struct.
Including transport parameters in the TLS handshake provides
integrity protection for these values.
enum {
quic_transport_parameters(0xffa5), (65535)
} ExtensionType;
The "extension_data" field of the quic_transport_parameters extension
contains a value that is defined by the version of QUIC that is in
use. The quic_transport_parameters extension carries a
TransportParameters struct when the version of QUIC defined in
[QUIC-TRANSPORT] is used.
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The quic_transport_parameters extension is carried in the ClientHello
and the EncryptedExtensions messages during the handshake. Endpoints
MUST send the quic_transport_parameters extension; endpoints that
receive ClientHello or EncryptedExtensions messages without the
quic_transport_parameters extension MUST close the connection with an
error of type 0x16d (equivalent to a fatal TLS missing_extension
alert, see Section 4.8).
While the transport parameters are technically available prior to the
completion of the handshake, they cannot be fully trusted until the
handshake completes, and reliance on them should be minimized.
However, any tampering with the parameters will cause the handshake
to fail.
Endpoints MUST NOT send this extension in a TLS connection that does
not use QUIC (such as the use of TLS with TCP defined in [TLS13]). A
fatal unsupported_extension alert MUST be sent by an implementation
that supports this extension if the extension is received when the
transport is not QUIC.
8.3. Removing the EndOfEarlyData Message
The TLS EndOfEarlyData message is not used with QUIC. QUIC does not
rely on this message to mark the end of 0-RTT data or to signal the
change to Handshake keys.
Clients MUST NOT send the EndOfEarlyData message. A server MUST
treat receipt of a CRYPTO frame in a 0-RTT packet as a connection
error of type PROTOCOL_VIOLATION.
As a result, EndOfEarlyData does not appear in the TLS handshake
transcript.
9. Security Considerations
There are likely to be some real clangers here eventually, but the
current set of issues is well captured in the relevant sections of
the main text.
Never assume that because it isn't in the security considerations
section it doesn't affect security. Most of this document does.
9.1. Replay Attacks with 0-RTT
As described in Section 8 of [TLS13], use of TLS early data comes
with an exposure to replay attack. The use of 0-RTT in QUIC is
similarly vulnerable to replay attack.
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Endpoints MUST implement and use the replay protections described in
[TLS13], however it is recognized that these protections are
imperfect. Therefore, additional consideration of the risk of replay
is needed.
QUIC is not vulnerable to replay attack, except via the application
protocol information it might carry. The management of QUIC protocol
state based on the frame types defined in [QUIC-TRANSPORT] is not
vulnerable to replay. Processing of QUIC frames is idempotent and
cannot result in invalid connection states if frames are replayed,
reordered or lost. QUIC connections do not produce effects that last
beyond the lifetime of the connection, except for those produced by
the application protocol that QUIC serves.
Note: TLS session tickets and address validation tokens are used to
carry QUIC configuration information between connections. These
MUST NOT be used to carry application semantics. The potential
for reuse of these tokens means that they require stronger
protections against replay.
A server that accepts 0-RTT on a connection incurs a higher cost than
accepting a connection without 0-RTT. This includes higher
processing and computation costs. Servers need to consider the
probability of replay and all associated costs when accepting 0-RTT.
Ultimately, the responsibility for managing the risks of replay
attacks with 0-RTT lies with an application protocol. An application
protocol that uses QUIC MUST describe how the protocol uses 0-RTT and
the measures that are employed to protect against replay attack. An
analysis of replay risk needs to consider all QUIC protocol features
that carry application semantics.
Disabling 0-RTT entirely is the most effective defense against replay
attack.
QUIC extensions MUST describe how replay attacks affect their
operation, or prohibit their use in 0-RTT. Application protocols
MUST either prohibit the use of extensions that carry application
semantics in 0-RTT or provide replay mitigation strategies.
9.2. Packet Reflection Attack Mitigation
A small ClientHello that results in a large block of handshake
messages from a server can be used in packet reflection attacks to
amplify the traffic generated by an attacker.
QUIC includes three defenses against this attack. First, the packet
containing a ClientHello MUST be padded to a minimum size. Second,
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if responding to an unverified source address, the server is
forbidden to send more than three UDP datagrams in its first flight
(see Section 8.1 of [QUIC-TRANSPORT]). Finally, because
acknowledgements of Handshake packets are authenticated, a blind
attacker cannot forge them. Put together, these defenses limit the
level of amplification.
9.3. Header Protection Analysis
Header protection relies on the packet protection AEAD being a
pseudorandom function (PRF), which is not a property that AEAD
algorithms guarantee. Therefore, no strong assurances about the
general security of this mechanism can be shown in the general case.
The AEAD algorithms described in this document are assumed to be
PRFs.
The header protection algorithms defined in this document take the
form:
protected_field = field XOR PRF(hp_key, sample)
This construction is secure against chosen plaintext attacks (IND-
CPA) [IMC].
Use of the same key and ciphertext sample more than once risks
compromising header protection. Protecting two different headers
with the same key and ciphertext sample reveals the exclusive OR of
the protected fields. Assuming that the AEAD acts as a PRF, if L
bits are sampled, the odds of two ciphertext samples being identical
approach 2^(-L/2), that is, the birthday bound. For the algorithms
described in this document, that probability is one in 2^64.
Note: In some cases, inputs shorter than the full size required by
the packet protection algorithm might be used.
To prevent an attacker from modifying packet headers, the header is
transitively authenticated using packet protection; the entire packet
header is part of the authenticated additional data. Protected
fields that are falsified or modified can only be detected once the
packet protection is removed.
An attacker could guess values for packet numbers and have an
endpoint confirm guesses through timing side channels. Similarly,
guesses for the packet number length can be trialed and exposed. If
the recipient of a packet discards packets with duplicate packet
numbers without attempting to remove packet protection they could
reveal through timing side-channels that the packet number matches a
received packet. For authentication to be free from side-channels,
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the entire process of header protection removal, packet number
recovery, and packet protection removal MUST be applied together
without timing and other side-channels.
For the sending of packets, construction and protection of packet
payloads and packet numbers MUST be free from side-channels that
would reveal the packet number or its encoded size.
9.4. Key Diversity
In using TLS, the central key schedule of TLS is used. As a result
of the TLS handshake messages being integrated into the calculation
of secrets, the inclusion of the QUIC transport parameters extension
ensures that handshake and 1-RTT keys are not the same as those that
might be produced by a server running TLS over TCP. To avoid the
possibility of cross-protocol key synchronization, additional
measures are provided to improve key separation.
The QUIC packet protection keys and IVs are derived using a different
label than the equivalent keys in TLS.
To preserve this separation, a new version of QUIC SHOULD define new
labels for key derivation for packet protection key and IV, plus the
header protection keys. This version of QUIC uses the string "quic".
Other versions can use a version-specific label in place of that
string.
The initial secrets use a key that is specific to the negotiated QUIC
version. New QUIC versions SHOULD define a new salt value used in
calculating initial secrets.
10. IANA Considerations
This document does not create any new IANA registries, but it
registers the values in the following registries:
o TLS ExtensionsType Registry [TLS-REGISTRIES] - IANA is to register
the quic_transport_parameters extension found in Section 8.2. The
Recommended column is to be marked Yes. The TLS 1.3 Column is to
include CH and EE.
11. References
11.1. Normative References
[AEAD] McGrew, D., "An Interface and Algorithms for Authenticated
Encryption", RFC 5116, DOI 10.17487/RFC5116, January 2008,
<https://www.rfc-editor.org/info/rfc5116>.
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[AES] "Advanced encryption standard (AES)", National Institute
of Standards and Technology report,
DOI 10.6028/nist.fips.197, November 2001.
[CHACHA] Nir, Y. and A. Langley, "ChaCha20 and Poly1305 for IETF
Protocols", RFC 8439, DOI 10.17487/RFC8439, June 2018,
<https://www.rfc-editor.org/info/rfc8439>.
[QUIC-RECOVERY]
Iyengar, J., Ed. and I. Swett, Ed., "QUIC Loss Detection
and Congestion Control", draft-ietf-quic-recovery-23 (work
in progress), September 2019.
[QUIC-TRANSPORT]
Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", draft-ietf-quic-
transport-23 (work in progress), September 2019.
[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>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[SHA] Dang, Q., "Secure Hash Standard", National Institute of
Standards and Technology report,
DOI 10.6028/nist.fips.180-4, July 2015.
[TLS-REGISTRIES]
Salowey, J. and S. Turner, "IANA Registry Updates for TLS
and DTLS", RFC 8447, DOI 10.17487/RFC8447, August 2018,
<https://www.rfc-editor.org/info/rfc8447>.
[TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
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11.2. Informative References
[AEBounds]
Luykx, A. and K. Paterson, "Limits on Authenticated
Encryption Use in TLS", March 2016,
<http://www.isg.rhul.ac.uk/~kp/TLS-AEbounds.pdf>.
[IMC] Katz, J. and Y. Lindell, "Introduction to Modern
Cryptography, Second Edition", ISBN 978-1466570269,
November 2014.
[QUIC-HTTP]
Bishop, M., Ed., "Hypertext Transfer Protocol (HTTP) over
QUIC", draft-ietf-quic-http-23 (work in progress),
September 2019.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
11.3. URIs
[1] https://mailarchive.ietf.org/arch/search/?email_list=quic
[2] https://github.com/quicwg
[3] https://github.com/quicwg/base-drafts/labels/-tls
Appendix A. Sample Initial Packet Protection
This section shows examples of packet protection for Initial packets
so that implementations can be verified incrementally. These packets
use an 8-byte client-chosen Destination Connection ID of
0x8394c8f03e515708. Values for both server and client packet
protection are shown together with values in hexadecimal.
A.1. Keys
The labels generated by the HKDF-Expand-Label function are:
client in: 00200f746c73313320636c69656e7420696e00
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server in: 00200f746c7331332073657276657220696e00
quic key: 00100e746c7331332071756963206b657900
quic iv: 000c0d746c733133207175696320697600
quic hp: 00100d746c733133207175696320687000
The initial secret is common:
initial_secret = HKDF-Extract(initial_salt, cid)
= 524e374c6da8cf8b496f4bcb69678350
7aafee6198b202b4bc823ebf7514a423
The secrets for protecting client packets are:
client_initial_secret
= HKDF-Expand-Label(initial_secret, "client in", _, 32)
= fda3953aecc040e48b34e27ef87de3a6
098ecf0e38b7e032c5c57bcbd5975b84
key = HKDF-Expand-Label(client_initial_secret, "quic key", _, 16)
= af7fd7efebd21878ff66811248983694
iv = HKDF-Expand-Label(client_initial_secret, "quic iv", _, 12)
= 8681359410a70bb9c92f0420
hp = HKDF-Expand-Label(client_initial_secret, "quic hp", _, 16)
= a980b8b4fb7d9fbc13e814c23164253d
The secrets for protecting server packets are:
server_initial_secret
= HKDF-Expand-Label(initial_secret, "server in", _, 32)
= 554366b81912ff90be41f17e80222130
90ab17d8149179bcadf222f29ff2ddd5
key = HKDF-Expand-Label(server_initial_secret, "quic key", _, 16)
= 5d51da9ee897a21b2659ccc7e5bfa577
iv = HKDF-Expand-Label(server_initial_secret, "quic iv", _, 12)
= 5e5ae651fd1e8495af13508b
hp = HKDF-Expand-Label(server_initial_secret, "quic hp", _, 16)
= a8ed82e6664f865aedf6106943f95fb8
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A.2. Client Initial
The client sends an Initial packet. The unprotected payload of this
packet contains the following CRYPTO frame, plus enough PADDING
frames to make an 1163 byte payload:
060040c4010000c003036660261ff947 cea49cce6cfad687f457cf1b14531ba1
4131a0e8f309a1d0b9c4000006130113 031302010000910000000b0009000006
736572766572ff01000100000a001400 12001d00170018001901000101010201
03010400230000003300260024001d00 204cfdfcd178b784bf328cae793b136f
2aedce005ff183d7bb14952072366470 37002b0003020304000d0020001e0403
05030603020308040805080604010501 060102010402050206020202002d0002
0101001c00024001
The unprotected header includes the connection ID and a 4 byte packet
number encoding for a packet number of 2:
c3ff000017088394c8f03e5157080000449e00000002
Protecting the payload produces output that is sampled for header
protection. Because the header uses a 4 byte packet number encoding,
the first 16 bytes of the protected payload is sampled, then applied
to the header:
sample = 535064a4268a0d9d7b1c9d250ae35516
mask = AES-ECB(hp, sample)[0..4]
= 833b343aaa
header[0] ^= mask[0] & 0x0f
= c0
header[17..20] ^= mask[1..4]
= 3b343aa8
header = c0ff000017088394c8f03e5157080000449e3b343aa8
The resulting protected packet is:
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c0ff000017088394c8f03e5157080000 449e3b343aa8535064a4268a0d9d7b1c
9d250ae355162276e9b1e3011ef6bbc0 ab48ad5bcc2681e953857ca62becd752
4daac473e68d7405fbba4e9ee616c870 38bdbe908c06d9605d9ac49030359eec
b1d05a14e117db8cede2bb09d0dbbfee 271cb374d8f10abec82d0f59a1dee29f
e95638ed8dd41da07487468791b719c5 5c46968eb3b54680037102a28e53dc1d
12903db0af5821794b41c4a93357fa59 ce69cfe7f6bdfa629eef78616447e1d6
11c4baf71bf33febcb03137c2c75d253 17d3e13b684370f668411c0f00304b50
1c8fd422bd9b9ad81d643b20da89ca05 25d24d2b142041cae0af205092e43008
0cd8559ea4c5c6e4fa3f66082b7d303e 52ce0162baa958532b0bbc2bc785681f
cf37485dff6595e01e739c8ac9efba31 b985d5f656cc092432d781db95221724
87641c4d3ab8ece01e39bc85b1543661 4775a98ba8fa12d46f9b35e2a55eb72d
7f85181a366663387ddc20551807e007 673bd7e26bf9b29b5ab10a1ca87cbb7a
d97e99eb66959c2a9bc3cbde4707ff77 20b110fa95354674e395812e47a0ae53
b464dcb2d1f345df360dc227270c7506 76f6724eb479f0d2fbb6124429990457
ac6c9167f40aab739998f38b9eccb24f d47c8410131bf65a52af841275d5b3d1
880b197df2b5dea3e6de56ebce3ffb6e 9277a82082f8d9677a6767089b671ebd
244c214f0bde95c2beb02cd1172d58bd f39dce56ff68eb35ab39b49b4eac7c81
5ea60451d6e6ab82119118df02a58684 4a9ffe162ba006d0669ef57668cab38b
62f71a2523a084852cd1d079b3658dc2 f3e87949b550bab3e177cfc49ed190df
f0630e43077c30de8f6ae081537f1e83 da537da980afa668e7b7fb25301cf741
524be3c49884b42821f17552fbd1931a 813017b6b6590a41ea18b6ba49cd48a4
40bd9a3346a7623fb4ba34a3ee571e3c 731f35a7a3cf25b551a680fa68763507
b7fde3aaf023c50b9d22da6876ba337e b5e9dd9ec3daf970242b6c5aab3aa4b2
96ad8b9f6832f686ef70fa938b31b4e5 ddd7364442d3ea72e73d668fb0937796
f462923a81a47e1cee7426ff6d922126 9b5a62ec03d6ec94d12606cb485560ba
b574816009e96504249385bb61a819be 04f62c2066214d8360a2022beb316240
b6c7d78bbe56c13082e0ca272661210a bf020bf3b5783f1426436cf9ff418405
93a5d0638d32fc51c5c65ff291a3a7a5 2fd6775e623a4439cc08dd25582febc9
44ef92d8dbd329c91de3e9c9582e41f1 7f3d186f104ad3f90995116c682a2a14
a3b4b1f547c335f0be710fc9fc03e0e5 87b8cda31ce65b969878a4ad4283e6d5
b0373f43da86e9e0ffe1ae0fddd35162 55bd74566f36a38703d5f34249ded1f6
6b3d9b45b9af2ccfefe984e13376b1b2 c6404aa48c8026132343da3f3a33659e
c1b3e95080540b28b7f3fcd35fa5d843 b579a84c089121a60d8c1754915c344e
eaf45a9bf27dc0c1e784161691220913 13eb0e87555abd706626e557fc36a04f
cd191a58829104d6075c5594f627ca50 6bf181daec940f4a4f3af0074eee89da
acde6758312622d4fa675b39f728e062 d2bee680d8f41a597c262648bb18bcfc
13c8b3d97b1a77b2ac3af745d61a34cc 4709865bac824a94bb19058015e4e42d
c9be6c7803567321829dd85853396269
A.3. Server Initial
The server sends the following payload in response, including an ACK
frame, a CRYPTO frame, and no PADDING frames:
0d0000000018410a020000560303eefc e7f7b37ba1d1632e96677825ddf73988
cfc79825df566dc5430b9a045a120013 0100002e00330024001d00209d3c940d
89690b84d08a60993c144eca684d1081 287c834d5311bcf32bb9da1a002b0002
0304
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The header from the server includes a new connection ID and a 2-byte
packet number encoding for a packet number of 1:
c1ff0000170008f067a5502a4262b50040740001
As a result, after protection, the header protection sample is taken
starting from the third protected octet:
sample = 7002596f99ae67abf65a5852f54f58c3
mask = 38168a0c25
header = c1ff0000170008f067a5502a4262b5004074168b
The final protected packet is then:
c9ff0000170008f067a5502a4262b500 4074168bf22b7002596f99ae67abf65a
5852f54f58c37c808682e2e40492d8a3 899fb04fc0afe9aabc8767b18a0aa493
537426373b48d502214dd856d63b78ce e37bc664b3fe86d487ac7a77c53038a3
cd32f0b5004d9f5754c4f7f2d1f35cf3 f7116351c92b9cf9bb6d091ddfc8b32d
432348a2c413
Appendix B. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
Issue and pull request numbers are listed with a leading octothorp.
B.1. Since draft-ietf-quic-tls-22
o Update the salt used for Initial secrets (#2887, #2980)
B.2. Since draft-ietf-quic-tls-21
o No changes
B.3. Since draft-ietf-quic-tls-20
o Mandate the use of the QUIC transport parameters extension (#2528,
#2560)
o Define handshake completion and confirmation; define clearer rules
when it encryption keys should be discarded (#2214, #2267, #2673)
B.4. Since draft-ietf-quic-tls-18
o Increased the set of permissible frames in 0-RTT (#2344, #2355)
o Transport parameter extension is mandatory (#2528, #2560)
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B.5. Since draft-ietf-quic-tls-17
o Endpoints discard initial keys as soon as handshake keys are
available (#1951, #2045)
o Use of ALPN or equivalent is mandatory (#2263, #2284)
B.6. Since draft-ietf-quic-tls-14
o Update the salt used for Initial secrets (#1970)
o Clarify that TLS_AES_128_CCM_8_SHA256 isn't supported (#2019)
o Change header protection
* Sample from a fixed offset (#1575, #2030)
* Cover part of the first byte, including the key phase (#1322,
#2006)
o TLS provides an AEAD and KDF function (#2046)
* Clarify that the TLS KDF is used with TLS (#1997)
* Change the labels for calculation of QUIC keys (#1845, #1971,
#1991)
o Initial keys are discarded once Handshake are avaialble (#1951,
#2045)
B.7. Since draft-ietf-quic-tls-13
o Updated to TLS 1.3 final (#1660)
B.8. Since draft-ietf-quic-tls-12
o Changes to integration of the TLS handshake (#829, #1018, #1094,
#1165, #1190, #1233, #1242, #1252, #1450)
* The cryptographic handshake uses CRYPTO frames, not stream 0
* QUIC packet protection is used in place of TLS record
protection
* Separate QUIC packet number spaces are used for the handshake
* Changed Retry to be independent of the cryptographic handshake
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* Limit the use of HelloRetryRequest to address TLS needs (like
key shares)
o Changed codepoint of TLS extension (#1395, #1402)
B.9. Since draft-ietf-quic-tls-11
o Encrypted packet numbers.
B.10. Since draft-ietf-quic-tls-10
o No significant changes.
B.11. Since draft-ietf-quic-tls-09
o Cleaned up key schedule and updated the salt used for handshake
packet protection (#1077)
B.12. Since draft-ietf-quic-tls-08
o Specify value for max_early_data_size to enable 0-RTT (#942)
o Update key derivation function (#1003, #1004)
B.13. Since draft-ietf-quic-tls-07
o Handshake errors can be reported with CONNECTION_CLOSE (#608,
#891)
B.14. Since draft-ietf-quic-tls-05
No significant changes.
B.15. Since draft-ietf-quic-tls-04
o Update labels used in HKDF-Expand-Label to match TLS 1.3 (#642)
B.16. Since draft-ietf-quic-tls-03
No significant changes.
B.17. Since draft-ietf-quic-tls-02
o Updates to match changes in transport draft
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B.18. Since draft-ietf-quic-tls-01
o Use TLS alerts to signal TLS errors (#272, #374)
o Require ClientHello to fit in a single packet (#338)
o The second client handshake flight is now sent in the clear (#262,
#337)
o The QUIC header is included as AEAD Associated Data (#226, #243,
#302)
o Add interface necessary for client address validation (#275)
o Define peer authentication (#140)
o Require at least TLS 1.3 (#138)
o Define transport parameters as a TLS extension (#122)
o Define handling for protected packets before the handshake
completes (#39)
o Decouple QUIC version and ALPN (#12)
B.19. Since draft-ietf-quic-tls-00
o Changed bit used to signal key phase
o Updated key phase markings during the handshake
o Added TLS interface requirements section
o Moved to use of TLS exporters for key derivation
o Moved TLS error code definitions into this document
B.20. Since draft-thomson-quic-tls-01
o Adopted as base for draft-ietf-quic-tls
o Updated authors/editors list
o Added status note
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Acknowledgments
This document has benefited from input from Dragana Damjanovic,
Christian Huitema, Jana Iyengar, Adam Langley, Roberto Peon, Eric
Rescorla, Ian Swett, and many others.
Contributors
Ryan Hamilton was originally an author of this specification.
Authors' Addresses
Martin Thomson (editor)
Mozilla
Email: mt@lowentropy.net
Sean Turner (editor)
sn3rd
Email: sean@sn3rd.com
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