Simple Authentication and Security Layer

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Simple Authentication and Security Layer (SASL) is a framework for authentication and data security in Internet protocols. It decouples authentication mechanisms from application protocols, in theory allowing any authentication mechanism supported by SASL to be used in any application protocol that uses SASL. Authentication mechanisms can also support proxy authorization, a facility allowing one user to assume the identity of another. They can also provide a data security layer offering data integrity and data confidentiality services. DIGEST-MD5 provides an example of mechanisms which can provide a data-security layer. Application protocols that support SASL typically also support Transport Layer Security (TLS) to complement the services offered by SASL.

John Gardiner Myers wrote the original SASL specification (RFC 2222) in 1997. In 2006, that document was replaced by RFC 4422 authored by Alexey Melnikov and Kurt D. Zeilenga. SASL, as defined by RFC 4422 is an IETF Standard Track protocol and is, as of 2006, a Proposed Standard.

SASL mechanisms[edit]

A SASL mechanism implements a series of challenges and responses. Defined SASL mechanisms[1] include:

where authentication is implicit in the context (e.g., for protocols already using IPsec or TLS)
for unauthenticated guest access
a simple cleartext password mechanism, defined in RFC 4616
a one-time password mechanism. Obsoletes the SKEY mechanism.
an S/KEY mechanism.
a simple challenge-response scheme based on HMAC-MD5.
(historic[2]), partially HTTP Digest compatible challenge-response scheme based upon MD5. DIGEST-MD5 offered a data security layer.
(RFC 5802), modern challenge-response scheme based mechanism with channel binding support
an NT LAN Manager authentication mechanism
family of mechanisms supports arbitrary GSS-API mechanisms in SASL.[3] It is now standardized as RFC 5801.
for Kerberos V5 authentication via the GSSAPI. GSSAPI offers a data-security layer.
for Mozilla Persona authentication[4]
for GSS EAP authentication[5]
GateKeeper (& GateKeeperPassport)
a challenge-response mechanism developed by Microsoft for MSN Chat
OAuth 2.0 bearer tokens (RFC 6750), communicated through TLS[6]
OAuth 1.0a message-authentication-code tokens (RFC 5849, Section 3.4.2)[6]

SASL-aware application protocols[edit]

Application protocols define their representation of SASL exchanges with a profile. A protocol has a service name such as "ldap" in a registry shared with GSSAPI and Kerberos.[7]

As of 2012 protocols currently supporting SASL include:

See also[edit]


  1. ^ "Simple Authentication and Security Layer (SASL) Mechanisms".
  2. ^ RFC 6331
  3. ^ Simon Josefsson. "Using GSS-API Mechanisms in SASL: The GS2 Mechanism Family".
  4. ^ Luke Howard. "A SASL and GSS-API Mechanism for the BrowserID Authentication Protocol".
  5. ^ Sam Hartman. "A GSS-API Mechanism for the Extensible Authentication Protocol".
  6. ^ a b A Set of Simple Authentication and Security Layer (SASL) Mechanisms for OAuth. IETF. August 2015. doi:10.17487/RFC7628. RFC 7628. Retrieved October 7, 2016.
  7. ^ "Generic Security Service Application Program Interface (GSSAPI)/Kerberos/Simple Authentication and Security Layer (SASL) Service Names".
  8. ^ "Request for allocation of new security type code for SASL auth".

External links[edit]

  • RFC 4422 - Simple Authentication and Security Layer (SASL) - obsoletes RFC 2222
  • RFC 4505 - Anonymous Simple Authentication and Security Layer (SASL) Mechanism - obsoletes RFC 2245
  • RFC 4616 - The PLAIN Simple Authentication and Security Layer (SASL) Mechanism - updates RFC 2595
  • The IETF SASL Working Group, chartered to revise existing SASL specifications, as well as to develop a family of GSSAPI mechanisms
  • Cyrus SASL, a free and portable SASL library providing generic security for various applications
  • GNU SASL, a free and portable SASL command-line utility and library, distributed under the GNU GPLv3 and LGPLv2.1, respectively
  • Dovecot SASL, an SASL implementation
  • RFC 2831 (historic) - Using Digest Authentication as a SASL Mechanism, obsoleted in RFC 6331
  • Java SASL API Programming and Deployment Guide