Deprecation of TLS 1.1 for Email
Submission and Access
cyberstorm.mu
88 Avenue De Plevitz Roches Brunes
Rose Hill
71259
Mauritius
+230 59762817
logan@cyberstorm.mu
Trinity College Dublin
Dublin
2
Ireland
+353-1-896-2354
stephen.farrell@cs.tcd.ie
Internet
This specification updates the current recommendation for the use of
the 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 RFC 8314.
Introduction
defines the minimum
recommended version of TLS as version 1.1. Due to the deprecation of
TLS 1.1 in , this recommendation is no longer valid. Therefore,
this document updates so that
the minimum version for TLS is TLS 1.2.
Conventions Used in This Document
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
when, and only when, they appear in all capitals, as shown here.
Updates to RFC 8314
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.
In , the
text should be revised from:
OLD:
One way is for the server to
refuse a ClientHello message from any client sending a
ClientHello.version field corresponding to any version of SSL or
TLS 1.0.
NEW:
One way is for the server to
refuse a ClientHello message from any client sending a
ClientHello.version field corresponding to any version of SSL or
TLS earlier than TLS 1.2.
OLD:
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 or later. Earlier TLS and
SSL versions MAY also be supported, so long as the MUA requires at
least TLS 1.1 when accessing accounts that are
configured to impose minimum confidentiality requirements.
NEW:
MUAs MUST implement TLS 1.2 or later, e.g., TLS 1.3 . Earlier TLS and
SSL versions MAY also be supported, so long as the MUA requires at
least TLS 1.2 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.)
IANA Considerations
This document has no IANA actions.
Security Considerations
The purpose of this document is to document updated recommendations
for using TLS with email services. Those recommendations are based on
.
References
Normative References
Deprecating TLS 1.0 and TLS 1.1
Dell EMC
Trinity College Dublin
Informative References
Acknowledgements
The authors would like to thank and for their
feedback.