draft-ietf-tls-certificate-compression-02.txt   draft-ietf-tls-certificate-compression-03.txt 
TLS A. Ghedini TLS A. Ghedini
Internet-Draft Cloudflare, Inc. Internet-Draft Cloudflare, Inc.
Intended status: Standards Track V. Vasiliev Intended status: Standards Track V. Vasiliev
Expires: July 30, 2018 Google Expires: October 25, 2018 Google
January 26, 2018 April 23, 2018
Transport Layer Security (TLS) Certificate Compression Transport Layer Security (TLS) Certificate Compression
draft-ietf-tls-certificate-compression-02 draft-ietf-tls-certificate-compression-03
Abstract Abstract
In Transport Layer Security (TLS) handshakes, certificate chains In Transport Layer Security (TLS) handshakes, certificate chains
often take up the majority of the bytes transmitted. often take up the majority of the bytes transmitted.
This document describes how certificate chains can be compressed to This document describes how certificate chains can be compressed to
reduce the amount of data transmitted and avoid some round trips. reduce the amount of data transmitted and avoid some round trips.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 30, 2018. This Internet-Draft will expire on October 25, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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avoid transmitting certificates already shared in an earlier avoid transmitting certificates already shared in an earlier
handshake, but it doesn't help when the client connects to a server handshake, but it doesn't help when the client connects to a server
for the first time and doesn't already have knowledge of the server's for the first time and doesn't already have knowledge of the server's
certificate chain. certificate chain.
This document describes a mechanism that would allow certificates to This document describes a mechanism that would allow certificates to
be compressed during full handshakes. be compressed during full handshakes.
2. Notational Conventions 2. Notational Conventions
The words "MUST", "MUST NOT", "SHALL", "SHOULD", and "MAY" are used The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
in this document. It's not shouting; when they are capitalized, they "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
have the special meaning defined in [RFC2119]. "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. Negotiating Certificate Compression 3. Negotiating Certificate Compression
This extension is only supported with TLS 1.3 and newer; if TLS 1.2 This extension is only supported with TLS 1.3 and newer; if TLS 1.2
or earlier is negotiated, the peers MUST ignore this extension. or earlier is negotiated, the peers MUST ignore this extension.
This document defines a new extension type This document defines a new extension type
(compress_certificate(TBD)), which can be used to signal the (compress_certificate(TBD)), which can be used to signal the
supported compression formats for the Certificate message to the supported compression formats for the Certificate message to the
peer. Whenever it is sent by the client as a ClientHello message peer. Whenever it is sent by the client as a ClientHello message
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the server as a CertificateRequest extension ([I-D.ietf-tls-tls13], the server as a CertificateRequest extension ([I-D.ietf-tls-tls13],
Section 4.3.2), it indicates the support for compressed client Section 4.3.2), it indicates the support for compressed client
certificates. certificates.
By sending a compress_certificate extension, the sender indicates to By sending a compress_certificate extension, the sender indicates to
the peer the certificate compression algorithms it is willing to use the peer the certificate compression algorithms it is willing to use
for decompression. The "extension_data" field of this extension for decompression. The "extension_data" field of this extension
SHALL contain a CertificateCompressionAlgorithms value: SHALL contain a CertificateCompressionAlgorithms value:
enum { enum {
zlib(0), zlib(1),
brotli(1), brotli(2),
(255) (65535)
} CertificateCompressionAlgorithm; } CertificateCompressionAlgorithm;
struct { struct {
CertificateCompressionAlgorithm algorithms<1..2^8-1>; CertificateCompressionAlgorithm algorithms<1..2^8-1>;
} CertificateCompressionAlgorithms; } CertificateCompressionAlgorithms;
There is no ServerHello extension that the server is required to echo There is no ServerHello extension that the server is required to echo
back. back.
4. Compressed Certificate Message 4. Compressed Certificate Message
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If the specified compression algorithm is zlib, then the Certificate If the specified compression algorithm is zlib, then the Certificate
message MUST be compressed with the ZLIB compression algorithm, as message MUST be compressed with the ZLIB compression algorithm, as
defined in [RFC1950]. If the specified compression algorithm is defined in [RFC1950]. If the specified compression algorithm is
brotli, the Certificate message MUST be compressed with the Brotli brotli, the Certificate message MUST be compressed with the Brotli
compression algorithm as defined in [RFC7932]. compression algorithm as defined in [RFC7932].
If the received CompressedCertificate message cannot be decompressed, If the received CompressedCertificate message cannot be decompressed,
the connection MUST be torn down with the "bad_certificate" alert. the connection MUST be torn down with the "bad_certificate" alert.
If the format of the Certificate message is altered using the If the format of the Certificate message is altered using the
server_certificate_type extension [RFC7250], the resulting altered server_certificate_type or client_certificate_type extensions
message is compressed instead. [RFC7250], the resulting altered message is compressed instead.
5. Security Considerations 5. Security Considerations
After decompression, the Certificate message MUST be processed as if After decompression, the Certificate message MUST be processed as if
it were encoded without being compressed. This way, the parsing and it were encoded without being compressed. This way, the parsing and
the verification have the same security properties as they would have the verification have the same security properties as they would have
in TLS normally. in TLS normally.
Since certificate chains are typically presented on a per-server name Since certificate chains are typically presented on a per-server name
or per-user basis, the attacker does not have control over any or per-user basis, the attacker does not have control over any
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7.3. Registry for Compression Algorithms 7.3. Registry for Compression Algorithms
This document establishes a registry of compression algorithms This document establishes a registry of compression algorithms
supported for compressing the Certificate message, titled supported for compressing the Certificate message, titled
"Certificate Compression Algorithm IDs", under the existing "Certificate Compression Algorithm IDs", under the existing
"Transport Layer Security (TLS) Extensions" heading. "Transport Layer Security (TLS) Extensions" heading.
The entries in the registry are: The entries in the registry are:
+------------------+--------------------------+ +------------------+-------------------------------+
| Algorithm Number | Description | | Algorithm Number | Description |
+------------------+--------------------------+ +------------------+-------------------------------+
| 0 | zlib | | 0 | Reserved |
| | | | | |
| 1 | brotli | | 1 | zlib |
| | | | | |
| 224 to 255 | Reserved for Private Use | | 2 | brotli |
+------------------+--------------------------+ | | |
| 16384 to 65535 | Reserved for Experimental Use |
+------------------+-------------------------------+
The values in this registry shall be allocated under "IETF Review" The values in this registry shall be allocated under "IETF Review"
policy for values strictly smaller than 64, and under "Specification policy for values strictly smaller than 256, under "Specification
Required" policy otherwise (see [RFC8126] for the definition of Required" policy for values 256-16383, and under "Experimental Use"
relevant policies). otherwise (see [RFC8126] for the definition of relevant policies).
Experimental Use extensions can be used both on private networks and
over the open Internet.
The procedures for requesting values in the Specification Required
space are specified in [I-D.ietf-tls-iana-registry-updates].
8. Normative References 8. Normative References
[I-D.ietf-tls-iana-registry-updates]
Salowey, J. and S. Turner, "IANA Registry Updates for TLS
and DTLS", draft-ietf-tls-iana-registry-updates-04 (work
in progress), February 2018.
[I-D.ietf-tls-tls13] [I-D.ietf-tls-tls13]
Rescorla, E., "The Transport Layer Security (TLS) Protocol Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", draft-ietf-tls-tls13-23 (work in progress), Version 1.3", draft-ietf-tls-tls13-28 (work in progress),
January 2018. March 2018.
[RFC1950] Deutsch, P. and J-L. Gailly, "ZLIB Compressed Data Format [RFC1950] Deutsch, P. and J-L. Gailly, "ZLIB Compressed Data Format
Specification version 3.3", RFC 1950, Specification version 3.3", RFC 1950,
DOI 10.17487/RFC1950, May 1996, DOI 10.17487/RFC1950, May 1996,
<https://www.rfc-editor.org/info/rfc1950>. <https://www.rfc-editor.org/info/rfc1950>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4366] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J.,
and T. Wright, "Transport Layer Security (TLS)
Extensions", RFC 4366, DOI 10.17487/RFC4366, April 2006,
<https://www.rfc-editor.org/info/rfc4366>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J.,
Weiler, S., and T. Kivinen, "Using Raw Public Keys in Weiler, S., and T. Kivinen, "Using Raw Public Keys in
Transport Layer Security (TLS) and Datagram Transport Transport Layer Security (TLS) and Datagram Transport
Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250,
June 2014, <https://www.rfc-editor.org/info/rfc7250>. June 2014, <https://www.rfc-editor.org/info/rfc7250>.
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[RFC7932] Alakuijala, J. and Z. Szabadka, "Brotli Compressed Data [RFC7932] Alakuijala, J. and Z. Szabadka, "Brotli Compressed Data
Format", RFC 7932, DOI 10.17487/RFC7932, July 2016, Format", RFC 7932, DOI 10.17487/RFC7932, July 2016,
<https://www.rfc-editor.org/info/rfc7932>. <https://www.rfc-editor.org/info/rfc7932>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[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>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Certificate compression was originally introduced in the QUIC Crypto Certificate compression was originally introduced in the QUIC Crypto
protocol, designed by Adam Langley and Wan-Teh Chang. protocol, designed by Adam Langley and Wan-Teh Chang.
This document has benefited from contributions and suggestions from This document has benefited from contributions and suggestions from
David Benjamin, Ryan Hamilton, Ilari Liusvaara, Piotr Sikora, Ian David Benjamin, Ryan Hamilton, Ilari Liusvaara, Piotr Sikora, Ian
Swett, Martin Thomson, Sean Turner and many others. Swett, Martin Thomson, Sean Turner and many others.
Authors' Addresses Authors' Addresses
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