SMTP Service Extension for Client Identity
draft-storey-smtp-client-id-03

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INTERNET-DRAFT                                                 W. Storey
<draft-storey-smtp-client-id-03.txt>                          LinuxMagic
Intended Status: Standards Track
Expires August 1, 2017                                  February 1, 2017

               SMTP Service Extension for Client Identity
                  <draft-storey-smtp-client-id-03.txt>

Abstract

   This document defines an extension for the Simple Mail Transfer
   Protocol (SMTP) called "CID" to provide a method for clients to
   indicate an identity to the server.

   This identity is an additional token that may be used for security
   and/or informational purposes, and with it a server may optionally
   apply heuristics using this token.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
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Copyright Notice

   Copyright (c) 2016 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
   (http://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

Storey, William          Expires August 1, 2017                 [Page 1]
INTERNET-DRAFT            SMTP Client Identity          February 1, 2017

   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Storey, William          Expires August 1, 2017                 [Page 2]
INTERNET-DRAFT            SMTP Client Identity          February 1, 2017

Table of Contents

   1. Introduction ....................................................3
   2. The CID Service Extension .......................................4
   3. The CID Keyword of the EHLO Command .............................4
   4. The CID Command .................................................4
   5. Formal Syntax ...................................................6
   6. Discussion ......................................................6
   6.1 Utility ........................................................6
   6.2 Use Cases ......................................................7
   6.3 Other SMTP Identities ..........................................7
   7. Client Identity Types ...........................................8
   8. Examples ........................................................8
   8.1 MAC Address as Client Identity .................................8
   8.2 Client Identity Without a TLS/SSL Session ......................9
   8.3 Client Identity Leading to Rejection ...........................9
   8.4 Malformed CID Command .........................................10
   9. Security Considerations ........................................10
   10. IANA Considerations ...........................................11
   10.1 SMTP Extension Registration ..................................11
   11. References ....................................................11
   11.1 Normative References .........................................11

1. Introduction

   The [SMTP] protocol and its extensions describe methods whereby an
   SMTP client may provide identity information to an SMTP server.  This
   document defines an additional such method to provide an identity.

   Each existing identity mechanism available is subject to limitations,
   and none offer a way to identify the SMTP client with absolute
   confidence.

   Typically SMTP clients are identified through the establishment of an
   authorized identity using the [AUTH] SMTP extension.  SMTP servers
   are often subject to malicious clients attempting to use authorized
   identities not intended for their use (often referred to as a brute-
   force attack).  If such an attack is successful, then the SMTP server
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