RFC 2595 (rfc2595) - Page 2 of 15
Using TLS with IMAP, POP3 and ACAP
Alternative Format: Original Text Document
RFC 2595 Using TLS with IMAP, POP3 and ACAP June 1999
simple passwords and a challenge/response SASL mechanism is likely to
interoperate with a wide variety of clients without resorting to
unencrypted clear-text passwords.
The STARTTLS command rectifies a number of the problems with using a
separate port for a "secure" protocol variant. Some of these are
mentioned in section 7.
1.1. Conventions Used in this Document
The key words "REQUIRED", "MUST", "MUST NOT", "SHOULD", "SHOULD NOT",
"MAY", and "OPTIONAL" in this document are to be interpreted as
described in "Key words for use in RFCs to Indicate Requirement
Levels" [KEYWORDS].
Terms related to authentication are defined in "On Internet
Authentication" [AUTH].
Formal syntax is defined using ABNF [ABNF].
In examples, "C:" and "S:" indicate lines sent by the client and
server respectively.
2. Basic Interoperability and Security Requirements
The following requirements apply to all implementations of the
STARTTLS extension for IMAP, POP3 and ACAP.
2.1. Cipher Suite Requirements
Implementation of the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA [TLS] cipher
suite is REQUIRED. This is important as it assures that any two
compliant implementations can be configured to interoperate.
All other cipher suites are OPTIONAL.
2.2. Privacy Operational Mode Security Requirements
Both clients and servers SHOULD have a privacy operational mode which
refuses authentication unless successful activation of an encryption
layer (such as that provided by TLS) occurs prior to or at the time
of authentication and which will terminate the connection if that
encryption layer is deactivated. Implementations are encouraged to
have flexability with respect to the minimal encryption strength or
cipher suites permitted. A minimalist approach to this
recommendation would be an operational mode where the
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite is mandatory prior to
permitting authentication.
Newman Standards Track