Extensions to Salted Challenge Response (SCRAM) for 2 factor authentication
draft-melnikov-scram-2fa-01

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Network Working Group                                        A. Melnikov
Internet-Draft                                                 Isode Ltd
Intended status: Standards Track                           July 13, 2020
Expires: January 14, 2021

      Extensions to Salted Challenge Response (SCRAM) for 2 factor
                             authentication
                      draft-melnikov-scram-2fa-01

Abstract

   This specification describes an extension to family of Simple
   Authentication and Security Layer (SASL; RFC 4422) authentication
   mechanisms called the Salted Challenge Response Authentication
   Mechanism (SCRAM), which provides support for 2 factor
   authentication.

   This specification also gives an example how TOTP (RFC 6238) can be
   used as the second factor.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on January 14, 2021.

Copyright Notice

   Copyright (c) 2020 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
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   carefully, as they describe your rights and restrictions with respect

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   to this document.  Code Components extracted from this document must
   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.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions Used in This Document . . . . . . . . . . . . . .   2
   2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.2.  Notation  . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SCRAM Extension for 2FA . . . . . . . . . . . . . . . . . . .   3
   4.  Formal Syntax . . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Use of TOTP with SCRAM  . . . . . . . . . . . . . . . . . . .   4
   6.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Open Issues . . . . . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   5
   11. Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   SCRAM [RFC5802] is a password based SASL [RFC4422] authentication
   mechanism that provides (among other things) mutual authentication
   and binding to an external security layer such as TLS.

   Two-factor authentication (2FA) is a way to add additional security
   to an authentication exchange.  The first "factor" is a password.
   The second "factor" is a verification code retrieved from an
   application on a mobile device or computer.  2FA is conceptually
   similar to a security token device that banks in some countries
   require for online banking.  Other names for 2FA systems include OTP
   (one-time password) and TOTP (Time-based One-time Password algorithm,
   such as [RFC6238]).

   This specification describes an extension to SCRAM to provide 2
   factor authentication.  SCRAM already relies on passwords for
   authentication.  This document specifies how second "factors" can be
   incorporated into SCRAM authentication.

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].

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   Formal syntax is defined by [RFC5234] including the core rules
   defined in Appendix B of [RFC5234].

   Example lines prefaced by "C:" are sent by the client and ones
   prefaced by "S:" by the server.  If a single "C:" or "S:" label