Internet DRAFT - draft-pismenny-tls-dtls-plaintext-sequence-number
draft-pismenny-tls-dtls-plaintext-sequence-number
TLS Working Group B. Pismenny
Internet-Draft NVIDIA
Intended status: Standards Track 19 October 2023
Expires: 21 April 2024
Plaintext Sequence Numbers for Datagram Transport Security Layer 1.3
draft-pismenny-tls-dtls-plaintext-sequence-number-02
Abstract
This document specifies a TLS 1.3 extension that enables DTLS 1.3 to
negotiate the use of plaintext sequence numbers instead of protected
sequence numbers. Plaintext sequence numbers are advantageous in
closed networks where the benefits of lower latency outweigh the risk
of ossification and reduced privacy.
Status of This Memo
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This Internet-Draft will expire on 21 April 2024.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 2
3. Sequence Number Encryption Extension . . . . . . . . . . . . 2
4. Security Considerations . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. Normative References . . . . . . . . . . . . . . . . . . . . 4
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 4
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 4
1. Introduction
Datagram Transport Layer Security (DTLS) 1.3 [RFC9147] packet
encryption protects not only record data, but also the record
header's sequence number. The sequence number is encrypted by XORing
it with a mask which is generated by encrypting the leading 16 bytes
of the record's ciphertext with a sequence number key.
For high performance networking, sequence number encryption is a
trade-off between ossification and privacy on the one hand and
latency and complexity for hardware acceleration on the other hand.
Sequence number encryption improves privacy by hiding the real
ordering of packets from on-path observers. Sequence number
encryption also prevents protocol ossification, when middleboxes
manipulate packet delivery based on the sequence number. Sequence
number encryption however adds latency to packet processing on both
sender and receiver. Sequence number encryption also increases the
complexity and cost of NIC encryption accelerators, which are crucial
for enabling encryption in high performance computing systems that
seek to maximize performance and lowest penalty possible for
encryption.
2. Conventions and Definitions
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.
3. Sequence Number Encryption Extension
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enum {
default_cipher (0),
plaintext (1),
(65536)
} SeqNumEncAlgs;
struct {
select (Handshake.msg_type) {
case CH:
SeqNumEncAlgs supported_algs<1..255>;
case SH:
SeqNumEncAlgs selected_alg;
};
} SupportedSequenceNumberEncryptionAlgorithms;
The "sequence_number_encryption_algorithms" extension is used by the
client to specify the record sequence number encryption algorithms it
supports and by the server to select the algorithm it prefers. The
ClientHello message lists algorithms by the order of their
preference, starting from the most preferred algorithm.
If this extension is not present, in either ClientHello or
EncryptedExtensions, then both parties MUST fallback to the default
record sequence number encryption algorithm.
4. Security Considerations
This document allows endpoints to disable the record sequence number
encryption algorithm, which retracts the on-path tracking anti-
ossification protection established in [RFC9147] record sequence
number encryption. It is therefore RECOMMENDED that users limit the
deployment of this extension to closed environments, such as data
centers, where the risk of on-path observers is negligible.
5. IANA Considerations
IANA is requested to assign a new value from the TLS ExtensionType
values registry:
* The Extension Name should be sequence_number_encryption_algorithms
* The TLS 1.3 value should be CH,HRR,SH
* The DTLS-Only value should be Y
* The Recommended value should be N
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* The Reference should be this document
6. Normative References
[I-D.draft-ietf-tls-tlsflags]
Nir, Y., "A Flags Extension for TLS 1.3", Work in
Progress, Internet-Draft, draft-ietf-tls-tlsflags-12, 23
July 2023, <https://datatracker.ietf.org/doc/html/draft-
ietf-tls-tlsflags-12>.
[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/rfc/rfc2119>.
[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/rfc/rfc8174>.
[RFC9147] Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version
1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
<https://www.rfc-editor.org/rfc/rfc9147>.
Acknowledgments
TODO acknowledge.
Author's Address
Boris Pismenny
NVIDIA
Email: boris.pismenny@gmail.com
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