draft-ietf-tls-ticketrequests-01.txt   draft-ietf-tls-ticketrequests-02.txt 
Network Working Group T. Pauly Network Working Group T. Pauly
Internet-Draft Apple Inc. Internet-Draft Apple Inc.
Intended status: Informational D. Schinazi Intended status: Informational D. Schinazi
Expires: December 8, 2019 Google LLC Expires: March 30, 2020 Google LLC
C. Wood C. Wood
Apple Inc. Apple Inc.
June 06, 2019 September 27, 2019
TLS Ticket Requests TLS Ticket Requests
draft-ietf-tls-ticketrequests-01 draft-ietf-tls-ticketrequests-02
Abstract Abstract
TLS session tickets enable stateless connection resumption for TLS session tickets enable stateless connection resumption for
clients without server-side, per-client state. Servers vend an clients without server-side, per-client state. Servers vend an
arbitrary number of session tickets to clients, at their discretion, arbitrary number of session tickets to clients, at their discretion,
upon connection establishment. Clients store and use tickets when upon connection establishment. Clients store and use tickets when
resuming future connections. This document describes a mechanism by resuming future connections. This document describes a mechanism by
which clients may specify the desired number of tickets needed for which clients may specify the desired number of tickets needed for
future connections. This extension aims to provide a means for future connections. This extension aims to provide a means for
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connection attempts. connection attempts.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 http://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 December 8, 2019. This Internet-Draft will expire on March 30, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Ticket Requests . . . . . . . . . . . . . . . . . . . . . . . 4 3. Ticket Requests . . . . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 7.1. Normative References . . . . . . . . . . . . . . . . . . 5
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction 1. Introduction
As per [RFC5077], and as described in [RFC8446], TLS servers send As per [RFC5077], and as described in [RFC8446], TLS servers send
clients an arbitrary number of session tickets at their own clients an arbitrary number of session tickets at their own
discretion in NewSessionTicket messages. There are two limitations discretion in NewSessionTicket messages. There are two limitations
with this design. First, servers choose some (often hard-coded) with this design. First, servers choose some (often hard-coded)
number of tickets vended per connection. Second, clients do not have number of tickets vended per connection. Second, clients do not have
a way of expressing their desired number of tickets, which may impact a way of expressing their desired number of tickets, which may impact
future connection establishment. For example, clients may open future connection establishment. For example, clients may open
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purposes: purposes:
o Parallel HTTP connections: To minimize ticket reuse while still o Parallel HTTP connections: To minimize ticket reuse while still
improving performance, it may be useful to use multiple, distinct improving performance, it may be useful to use multiple, distinct
tickets when opening parallel connections. Clients must therefore tickets when opening parallel connections. Clients must therefore
bound the number of parallel connections they initiate by the bound the number of parallel connections they initiate by the
number of tickets in their possession, or risk ticket re-use. number of tickets in their possession, or risk ticket re-use.
o Connection racing: Happy Eyeballs V2 [RFC8305] describes o Connection racing: Happy Eyeballs V2 [RFC8305] describes
techniques for performing connection racing. The Transport techniques for performing connection racing. The Transport
Services Architecture implementation from [I-D.ietf-taps-impl] Services Architecture implementation from [TAPS] also describes
also describes how connections may race across interfaces and how connections may race across interfaces and address families.
address families. In cases where clients have early data to send In cases where clients have early data to send and want to
and want to minimize or avoid ticket re-use, unique tickets for minimize or avoid ticket re-use, unique tickets for each unique
each unique connection attempt are useful. Moreover, as some connection attempt are useful. Moreover, as some servers may
servers may implement single-use tickets (and even session ticket implement single-use tickets (and even session ticket encryption
encryption keys), distinct tickets will be needed to prevent keys), distinct tickets will be needed to prevent premature ticket
premature ticket invalidation by racing. invalidation by racing.
o Connection priming: In some systems, connections may be primed or o Connection priming: In some systems, connections may be primed or
bootstrapped by a centralized service or daemon for faster bootstrapped by a centralized service or daemon for faster
connection establishment. Requesting tickets on demand allows connection establishment. Requesting tickets on demand allows
such services to vend tickets to clients to use for accelerated such services to vend tickets to clients to use for accelerated
handshakes with early data. (Note that if early data is not handshakes with early data. (Note that if early data is not
needed by these connections, this method SHOULD NOT be used. needed by these connections, this method SHOULD NOT be used.
Fresh handshakes SHOULD be performed instead.) Fresh handshakes SHOULD be performed instead.)
o Less ticket waste: Currently, TLS servers use application- o Less ticket waste: Currently, TLS servers use application-
specific, and often implementation-specific, logic to determine specific, and often implementation-specific, logic to determine
how many tickets to issue. By moving the burden of ticket count how many tickets to issue. By moving the burden of ticket count
to clients, servers do not generate wasteful tickets for clients. to clients, servers do not generate wasteful tickets for clients.
Moreover, as ticket generation may involve expensive computation, Moreover, as ticket generation may involve expensive computation,
e.g., public key cryptographic operations, avoiding waste is e.g., public key cryptographic operations, avoiding waste is
desirable. desirable.
o Decline resumption: Clients may indicate they have no intention of
resuming connections by sending a ticket request with count of
zero.
3. Ticket Requests 3. Ticket Requests
Clients may indicate to servers their desired number of tickets via Clients may indicate to servers their desired number of tickets for a
the following "ticket_request" extension: single connection via the following "ticket_request" extension:
enum { enum {
ticket_request(TBD), (65535) ticket_request(TBD), (65535)
} ExtensionType; } ExtensionType;
Clients may send this extension in ClientHello. It contains the Clients may send this extension in ClientHello. It contains the
following structure: following structure:
struct { struct {
uint8 count; uint8 count;
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A supporting server MAY vend TicketRequestContents.count A supporting server MAY vend TicketRequestContents.count
NewSessionTicket messages to a requesting client, and SHOULD NOT send NewSessionTicket messages to a requesting client, and SHOULD NOT send
more than TicketRequestContents.count NewSessionTicket messages to a more than TicketRequestContents.count NewSessionTicket messages to a
requesting client. Servers SHOULD place a limit on the number of requesting client. Servers SHOULD place a limit on the number of
tickets they are willing to vend to clients. Thus, the number of tickets they are willing to vend to clients. Thus, the number of
NewSessionTicket messages sent should be the minimum of the server's NewSessionTicket messages sent should be the minimum of the server's
self-imposed limit and TicketRequestContents.count. Servers MUST NOT self-imposed limit and TicketRequestContents.count. Servers MUST NOT
send more than 255 tickets to clients. send more than 255 tickets to clients.
Servers that support ticket requests MUST NOT echo "ticket_request" Servers that support ticket requests MUST NOT echo "ticket_request"
in the EncryptedExtensions. in the EncryptedExtensions message. A client MUST abort the
connection with an "illegal_parameter" alert if the "ticket_request"
extension is present in the EncryptedExtensions message.
Clients MUST NOT change the value of TicketRequestContents.count in
second ClientHello messages sent in response to a HelloRetryRequest.
4. IANA Considerations 4. IANA Considerations
IANA is requested to Create an entry, ticket_request(TBD), in the IANA is requested to Create an entry, ticket_request(TBD), in the
existing registry for ExtensionType (defined in [RFC8446]), with "TLS existing registry for ExtensionType (defined in [RFC8446]), with "TLS
1.3" column values being set to "CH", and "Recommended" column being 1.3" column values being set to "CH", and "Recommended" column being
set to "Yes". set to "Yes".
5. Security Considerations 5. Security Considerations
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Despite ticket lifetime hints provided by servers, clients SHOULD Despite ticket lifetime hints provided by servers, clients SHOULD
dispose of pooled tickets after some reasonable amount of time that dispose of pooled tickets after some reasonable amount of time that
mimics the ticket rotation period. mimics the ticket rotation period.
6. Acknowledgments 6. Acknowledgments
The authors would like to thank David Benjamin, Eric Rescorla, Nick The authors would like to thank David Benjamin, Eric Rescorla, Nick
Sullivan, Martin Thomson, and other members of the TLS Working Group Sullivan, Martin Thomson, and other members of the TLS Working Group
for discussions on earlier versions of this draft. for discussions on earlier versions of this draft.
7. Normative References 7. References
[I-D.ietf-taps-impl] 7.1. Normative References
Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K.,
Jones, T., Tiesel, P., Perkins, C., and M. Welzl,
"Implementing Interfaces to Transport Services", draft-
ietf-taps-impl-03 (work in progress), March 2019.
[I-D.ietf-tls-dtls13] [I-D.ietf-tls-dtls13]
Rescorla, E., Tschofenig, H., and N. Modadugu, "The Rescorla, E., Tschofenig, H., and N. Modadugu, "The
Datagram Transport Layer Security (DTLS) Protocol Version Datagram Transport Layer Security (DTLS) Protocol Version
1.3", draft-ietf-tls-dtls13-31 (work in progress), March 1.3", draft-ietf-tls-dtls13-32 (work in progress), July
2019. 2019.
[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, <https://www.rfc- DOI 10.17487/RFC2119, March 1997,
editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without "Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077, Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>. January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 8305,
DOI 10.17487/RFC8305, December 2017, <https://www.rfc-
editor.org/info/rfc8305>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>. <https://www.rfc-editor.org/info/rfc8446>.
7.2. Informative References
[RFC8305] Schinazi, D. and T. Pauly, "Happy Eyeballs Version 2:
Better Connectivity Using Concurrency", RFC 8305,
DOI 10.17487/RFC8305, December 2017,
<https://www.rfc-editor.org/info/rfc8305>.
[TAPS] Brunstrom, A., Pauly, T., Enghardt, T., Grinnemo, K.,
Jones, T., Tiesel, P., Perkins, C., and M. Welzl,
"Implementing Interfaces to Transport Services", draft-
ietf-taps-impl-04 (work in progress), July 2019.
Authors' Addresses Authors' Addresses
Tommy Pauly Tommy Pauly
Apple Inc. Apple Inc.
One Apple Park Way One Apple Park Way
Cupertino, California 95014 Cupertino, California 95014
United States of America United States of America
Email: tpauly@apple.com Email: tpauly@apple.com
David Schinazi David Schinazi
Google LLC Google LLC
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