Deprecation of use of TLS 1.1 for Email Submission and Access
draft-ietf-uta-tls-for-email-04

Abstract

This specification updates current recommendation for the use of Transport Layer Security (TLS) protocol to provide confidentiality of email between a Mail User Agent (MUA) and a Mail Submission Server or Mail Access Server. This document updates RFC8314.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on July 26, 2020.

Copyright Notice

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Table of Contents

• 1. Introduction
• 2. Conventions Used in This Document
• 3. Updates to RFC8314
• 4. IANA Considerations
• 5. Security Considerations
• 6. Acknowledgement
• 7. References
• 7.1. Informative References
• 7.2. Normative References
• Authors' Addresses

1. Introduction

[RFC8314] defines the minimum recommended version for TLS as version 1.1. Due to the deprecation of TLS 1.1 in [I-D.ietf-tls-oldversions-deprecate], this recommendation is no longer valid. Therefore this document updates [RFC8314] so that the minimum version for TLS is TLS 1.2.

2. Conventions Used in This Document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] when they appear in ALL CAPS. These words may also appear in this document in lower case as plain English words, absent their normative meanings.

3. Updates to RFC8314

OLD:

"4.1. Deprecation of Services Using Cleartext and TLS Versions Less Than 1.1"

NEW:

"4.1. Deprecation of Services Using Cleartext and TLS Versions Less Than 1.2"

OLD

"As soon as practicable, MSPs currently supporting Secure Sockets Layer (SSL) 2.x, SSL 3.0, or TLS 1.0 SHOULD transition their users to TLS 1.1 or later and discontinue support for those earlier versions of SSL and TLS."

NEW:

"As soon as practicable, MSPs currently supporting Secure Sockets Layer (SSL) 2.x, SSL 3.0, TLS 1.0 or TLS 1.1 SHOULD transition their users to TLS 1.2 or later and discontinue support for those earlier versions of SSL and TLS."

OLD:

In Section 4.1, the text should be revised from: "It is RECOMMENDED that new users be required to use TLS version 1.1 or greater from the start. However, an MSP may find it necessary to make exceptions to accommodate some legacy systems that support only earlier versions of TLS or only cleartext."

NEW:

"It is RECOMMENDED that new users be required to use TLS version 1.2 or greater from the start. However, an MSP may find it necessary to make exceptions to accommodate some legacy systems that support only earlier versions of TLS or only cleartext."

OLD:

" If, however, an MUA provides such an indication, it MUST NOT indicate confidentiality for any connection that does not at least use TLS 1.1 with certificate verification and also meet the minimum confidentiality requirements associated with that account. "

NEW:

" If, however, an MUA provides such an indication, it MUST NOT indicate confidentiality for any connection that does not at least use TLS 1.2 with certificate verification and also meet the minimum confidentiality requirements associated with that account. "

OLD

" MUAs MUST implement TLS 1.2 [RFC5246] or later. Earlier TLS and SSL versions MAY also be supported, so long as the MUA requires at least TLS 1.1 [RFC4346] when accessing accounts that are configured to impose minimum confidentiality requirements. "

NEW:

" MUAs MUST implement TLS 1.2 [RFC5246] or later e.g TLS 1.3 [RFC8446]. Earlier TLS and SSL versions MAY also be supported, so long as the MUA requires at least TLS 1.2 [RFC5246] when accessing accounts that are configured to impose minimum confidentiality requirements. "

OLD:

" The default minimum expected level of confidentiality for all new accounts MUST require successful validation of the server's certificate and SHOULD require negotiation of TLS version 1.1 or greater. (Future revisions to this specification may raise these requirements or impose additional requirements to address newly discovered weaknesses in protocols or cryptographic algorithms. "

NEW:

" The default minimum expected level of confidentiality for all new accounts MUST require successful validation of the server's certificate and SHOULD require negotiation of TLS version 1.2 or greater. (Future revisions to this specification may raise these requirements or impose additional requirements to address newly discovered weaknesses in protocols or cryptographic algorithms. "

4. IANA Considerations

None of the proposed measures have an impact on IANA.

5. Security Considerations

The purpose of this document is to document updated recommendations for using TLS with Email services. Those recommendations are based on [I-D.ietf-tls-oldversions-deprecate].

6. Acknowledgement

The authors would like to thank Vittorio Bertola and Viktor Dukhovni for their feedback.

7. References

7.1. Informative References

7.2. Normative References

Authors' Addresses