New Protocols Must Require TLS 1.3
draft-ietf-uta-require-tls13-03

Using TLS in Applications                                        R. Salz
Internet-Draft                                       Akamai Technologies
Updates: 9325 (if approved)                                    N. Aviram
Intended status: Best Current Practice                   9 December 2024
Expires: 12 June 2025

                   New Protocols Must Require TLS 1.3
                    draft-ietf-uta-require-tls13-03

Abstract

   TLS 1.2 is in use and can be configured such that it provides good
   security properties.  TLS 1.3 use is increasing, and fixes some known
   deficiencies with TLS 1.2, such as removing error-prone cryptographic
   primitives and encrypting more of the traffic so that it is not
   readable by outsiders.  For these reasons, new protocols must require
   and assume the existence of TLS 1.3 existence.  This prescription
   does not pertain to DTLS (in any DTLS version); it pertains to TLS
   only.

   This document updates [RFC9325].

About This Document

   This note is to be removed before publishing as an RFC.

   Status information for this document may be found at
   https://datatracker.ietf.org/doc/draft-ietf-uta-require-tls13/.

   Discussion of this document takes place on the Using TLS in
   Applications Working Group mailing list (mailto:uta@ietf.org), which
   is archived at https://mailarchive.ietf.org/arch/browse/uta/.
   Subscribe at https://www.ietf.org/mailman/listinfo/uta/.

   Source for this draft and an issue tracker can be found at
   https://github.com/richsalz/draft-use-tls13.

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/.

Salz & Aviram             Expires 12 June 2025                  [Page 1]
Internet-Draft               require-tls1.3                December 2024

   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 12 June 2025.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   3
   3.  Implications for post-quantum cryptography  . . . . . . . . .   3
   4.  TLS Use by Other Protocols and Applications . . . . . . . . .   4
   5.  Changes to RFC 9325 . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   TLS 1.2 [TLS12] is in use and can be configured such that it provides
   good security properties.  However, this protocol version suffers
   from several deficiencies:

   1.  While application layer traffic is always encrypted, most of the
       handshake messages are not.  Therefore, the privacy provided is
       suboptimal.  This is a protocol issue that cannot be addressed by
       configuration.

Salz & Aviram             Expires 12 June 2025                  [Page 2]
Internet-Draft               require-tls1.3                December 2024

   2.  The list of cryptographic primitives specified for the protocol,
       both in-use primitives and deprecated ones, includes several
       primitives that have been a source for vulnerabilities throughout
       the years, such as RSA key exchange, CBC cipher suites, and
       problematic finite-field Diffie-Hellman group negotiation.  These
       issues could be addressed through proper configuration; however,
       experience shows that configuration mistakes are common,
       especially when deploying cryptography.  See Section 6 for
       elaboration.

   3.  The base protocol does not provide security against some types of
       attacks (see Section 6); extensions are required to provide
       security.

   TLS 1.3 [TLS13] is also in widespread use and fixes most known
   deficiencies with TLS 1.2, such as encrypting more of the traffic so
   that it is not readable by outsiders and removing most cryptographic
   primitives considered dangerous.  Importantly, TLS 1.3 enjoys robust
   security proofs and provides excellent security without any
   additional configuration.

   This document specifies that, since TLS 1.3 use is widespread, new
   protocols must require and assume its existence.  This prescription
   does not pertain to DTLS (in any DTLS version); it pertains to TLS
   only.

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.  Implications for post-quantum cryptography

   Cryptographically-relevant quantum computers, once available, will
   have a huge impact on TLS traffic.  In 2016, the US National
   Institute of Standards and Technology (NIST) started a multi-year
   effort to standardize algorithms that will be "safe" once quantum
   computers are feasible [PQC].  The first IETF discussions happened
   around the same time [CFRGSLIDES].

   In 2024 NIST released standards for [ML-KEM], [ML-DSA], and
   [SLH-DSA].  While industry was waiting for NIST to finish
   standardization, the IETF has had several efforts underway.  A
   working group was formed in early 2023 to work on operational and
   transitional uses of PQC in IETF protocols, [PQUIPWG].  Several other

Salz & Aviram             Expires 12 June 2025                  [Page 3]
Internet-Draft               require-tls1.3                December 2024

   working groups, notably LAMPS [LAMPSWG] and TLS [TLSWG], are working
   on drafts to support hybrid algorithms and identifiers, for use
   during a transition from classic to a post-quantum world.

   For TLS it is important to note that the focus of these efforts is
   TLS 1.3 or later: TLS 1.2 WILL NOT be supported (see Section 7).
   This is one more reason for new protocols to default to TLS 1.3,
   where post-quantum cryptography is expected to be supported.

4.  TLS Use by Other Protocols and Applications

   Any new protocol that uses TLS MUST specify as its default TLS 1.3.
   For example, QUIC [QUICTLS] requires TLS 1.3 and specifies that
   endpoints MUST terminate the connection if an older version is used.

   If deployment considerations are a concern, the protocol MAY specify
   TLS 1.2 as an additional, non-default option.  As a counter example,
   the Usage Profile for DNS over TLS [DNSTLS] specifies TLS 1.2 as the
   default, while also allowing TLS 1.3.  For newer specifications that
   choose to support TLS 1.2, those preferences are to be reversed.

   The initial TLS handshake allows a client to specify which versions
   of the TLS protocol it supports and the server is intended to pick
   the highest version that it also supports.  This is known as the "TLS
   version negotiation," and many TLS libraries provide a way for
   applications to specify the range of versions.  When the API allows
   it, clients SHOULD specify just the minimum version they want.  This
   MUST be TLS 1.3 or TLS 1.2, depending on the circumstances described
   in the above paragraphs.

5.  Changes to RFC 9325

   This document makes two changes to the recommendations in [RFC9325],
   Section 3.1.1:

   *  That section says that TLS 1.3 SHOULD be supported; this document
      says that for new protocols it MUST be supported.

   *  That section says that TLS 1.2 MUST be supported; this document
      says that it MAY be supported as described above.

   Again, these changes only apply to TLS, and not DTLS.

Salz & Aviram             Expires 12 June 2025                  [Page 4]
Internet-Draft               require-tls1.3                December 2024

6.  Security Considerations

   TLS 1.2 was specified with several cryptographic primitives and
   design choices that have, over time, weakened its security.  The
   purpose of this section is to briefly survey several such prominent
   problems that have affected the protocol.  It should be noted,
   however, that TLS 1.2 can be configured securely; it is merely much
   more difficult to configure it securely as opposed to using its
   modern successor, TLS 1.3.  See [RFC9325] for a more thorough guide
   on the secure deployment of TLS 1.2.

   Firstly, the TLS 1.2 protocol, without any extension points, is
   vulnerable to renegotiation attacks (see [RENEG1] and [RENEG2]) and
   the Triple Handshake attack (see [TRIPLESHAKE]).  Broadly, these
   attacks exploit the protocol's support for renegotiation in order to
   inject a prefix chosen by the attacker into the plaintext stream.
   This is usually a devastating threat in practice, that allows e.g.
   obtaining secret cookies in a web setting.  In light of the above
   problems, [RFC5746] specifies an extension that prevents this
   category of attacks.  To securely deploy TLS 1.2, either
   renegotiation must be disabled entirely, or this extension must be
   used.  Additionally, clients must not allow servers to renegotiate
   the certificate during a connection.

   Secondly, the original key exchange methods specified for the
   protocol, namely RSA key exchange and finite field Diffie-Hellman,
   suffer from several weaknesses.  Similarly, to securely deploy the
   protocol, these key exchange methods must be disabled.  See
   [I-D.draft-ietf-tls-deprecate-obsolete-kex] for details.

   Thirdly, symmetric ciphers which were widely-used in the protocol,
   namely RC4 and CBC cipher suites, suffer from several weaknesses.
   RC4 suffers from exploitable biases in its key stream; see [RFC7465].
   CBC cipher suites have been a source of vulnerabilities throughout
   the years.  A straightforward implementation of these cipher suites
   inherently suffers from the Lucky13 timing attack [LUCKY13].  The
   first attempt to implement the cipher suites in constant time
   introduced an even more severe vulnerability [LUCKY13FIX].  There
   have been further similar vulnerabilities throughout the years
   exploiting CBC cipher suites; refer to e.g.  [CBCSCANNING] for an
   example and a survey of similar works.

   And lastly, historically the protocol was affected by several other
   attacks that TLS 1.3 is immune to: BEAST [BEAST], Logjam [WEAKDH],
   FREAK [FREAK], and SLOTH [SLOTH].

Salz & Aviram             Expires 12 June 2025                  [Page 5]
Internet-Draft               require-tls1.3                December 2024

7.  IANA Considerations

   This document makes no requests to IANA.

8.  References

8.1.  Normative References

   [I-D.draft-ietf-tls-deprecate-obsolete-kex]
              Bartle, C. and N. Aviram, "Deprecating Obsolete Key
              Exchange Methods in TLS 1.2", Work in Progress, Internet-
              Draft, draft-ietf-tls-deprecate-obsolete-kex-05, 3
              September 2024, <https://datatracker.ietf.org/doc/html/
              draft-ietf-tls-deprecate-obsolete-kex-05>.

   [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>.

   [RFC5746]  Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
              "Transport Layer Security (TLS) Renegotiation Indication
              Extension", RFC 5746, DOI 10.17487/RFC5746, February 2010,
              <https://www.rfc-editor.org/rfc/rfc5746>.

   [RFC7465]  Popov, A., "Prohibiting RC4 Cipher Suites", RFC 7465,
              DOI 10.17487/RFC7465, February 2015,
              <https://www.rfc-editor.org/rfc/rfc7465>.

   [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>.

   [RFC9325]  Sheffer, Y., Saint-Andre, P., and T. Fossati,
              "Recommendations for Secure Use of Transport Layer
              Security (TLS) and Datagram Transport Layer Security
              (DTLS)", BCP 195, RFC 9325, DOI 10.17487/RFC9325, November
              2022, <https://www.rfc-editor.org/rfc/rfc9325>.

   [TLS12]    Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/rfc/rfc5246>.

   [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/rfc/rfc8446>.

Salz & Aviram             Expires 12 June 2025                  [Page 6]
Internet-Draft               require-tls1.3                December 2024

8.2.  Informative References

   [BEAST]    Duong, T. and J. Rizzo, "Here come the xor ninjas", n.d.,
              <http://www.hpcc.ecs.soton.ac.uk/dan/talks/bullrun/
              Beast.pdf>.

   [CBCSCANNING]
              Merget, R., Somorovsky, J., Aviram, N., Young, C.,
              Fliegenschmidt, J., Schwenk, J., and Y. Shavitt, "Scalable
              Scanning and Automatic Classification of TLS Padding
              Oracle Vulnerabilities", n.d.,
              <https://www.usenix.org/system/files/sec19-merget.pdf>.

   [CFRGSLIDES]
              McGrew, D., "Post Quantum Secure Cryptography Discussion",
              n.d., <https://www.ietf.org/proceedings/95/slides/slides-
              95-cfrg-4.pdf>.

   [DNSTLS]   Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
              for DNS over TLS and DNS over DTLS", RFC 8310,
              DOI 10.17487/RFC8310, March 2018,
              <https://www.rfc-editor.org/rfc/rfc8310>.

   [FREAK]    Beurdouche, B., Bhargavan, K., Delignat-Lavaud, A.,
              Fournet, C., Kohlweiss, M., Pironti, A., Strub, P.-Y., and
              J. K. Zinzindohoue, "A messy state of the union: Taming
              the composite state machines of TLS", n.d.,
              <https://inria.hal.science/hal-01114250/file/messy-state-
              of-the-union-oakland15.pdf>.

   [LAMPSWG]  "Limited Additional Mechanisms for PXIK and SMIME", n.d.,
              <https://datatracker.ietf.org/wg/lamps/about/>.

   [LUCKY13]  Al Fardan, N. J. and K. G. Paterson, "Lucky Thirteen:
              Breaking the TLS and DTLS record protocols", n.d.,
              <http://www.isg.rhul.ac.uk/tls/TLStiming.pdf>.

   [LUCKY13FIX]
              Somorovsky, J., "Systematic fuzzing and testing of TLS
              libraries", n.d., <https://nds.rub.de/media/nds/
              veroeffentlichungen/2016/10/19/tls-attacker-ccs16.pdf>.

   [ML-DSA]   "Module-Lattice-Based Key Digital Signature Standard",
              August 2024, <https://csrc.nist.gov/pubs/fips/204/final>.

   [ML-KEM]   "Module-Lattice-Based Key-Encapsulation Mechanism
              Standard", August 2024,
              <https://csrc.nist.gov/pubs/fips/203/final>.

Salz & Aviram             Expires 12 June 2025                  [Page 7]
Internet-Draft               require-tls1.3                December 2024

   [PQC]      "Post=Quantum Cryptography", January 2017,
              <https://csrc.nist.gov/projects/post-quantum-
              cryptography>.

   [PQUIPWG]  "Post-Quantum Use in Protocols", n.d.,
              <https://datatracker.ietf.org/wg/pquip/about/>.

   [QUICTLS]  Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure
              QUIC", RFC 9001, DOI 10.17487/RFC9001, May 2021,
              <https://www.rfc-editor.org/rfc/rfc9001>.

   [RENEG1]   Rescorla, E., "Understanding the TLS Renegotiation
              Attack", n.d.,
              <https://web.archive.org/web/20091231034700/
              http://www.educatedguesswork.org/2009/11/
              understanding_the_tls_renegoti.html>.

   [RENEG2]   Ray, M., "Authentication Gap in TLS Renegotiation", n.d.,
              <https://web.archive.org/web/20091228061844/
              http://extendedsubset.com/?p=8>.

   [SLH-DSA]  "Stateless Hash-Based Key-Digital Signature Standard",
              August 2024, <https://csrc.nist.gov/pubs/fips/205/final>.

   [SLOTH]    Bhargavan, K. and G. Leurent, "Transcript collision
              attacks: Breaking authentication in TLS, IKE, and SSH",
              n.d., <https://inria.hal.science/hal-01244855/file/
              SLOTH_NDSS16.pdf>.

   [TLSWG]    "Transport Layer Security", n.d.,
              <https://datatracker.ietf.org/wg/tls/about/>.

   [TRIPLESHAKE]
              "Triple Handshakes Considered Harmful Breaking and Fixing
              Authentication over TLS", n.d.,
              <https://mitls.org/pages/attacks/3SHAKE>.

   [WEAKDH]   Adrian, D., Bhargavan, K., Durumeric, Z., Gaudry, P.,
              Green, M., Halderman, J. A., Heninger, N., Springall, D.,
              Thomé, E., Valenta, L., and B. VanderSloot, "Imperfect
              forward secrecy: How Diffie-Hellman fails in practice",
              n.d.,
              <https://dl.acm.org/doi/pdf/10.1145/2810103.2813707>.

Authors' Addresses

   Rich Salz
   Akamai Technologies

Salz & Aviram             Expires 12 June 2025                  [Page 8]
Internet-Draft               require-tls1.3                December 2024

   Email: rsalz@akamai.com

   Nimrod Aviram
   Email: nimrod.aviram@gmail.com

Salz & Aviram             Expires 12 June 2025                  [Page 9]