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An implementation of the Security Assertion Markup Language (SAML) in Erlang. So far this supports enough of the standard to act as a Service Provider (SP) to perform authentication with SAML. It has been tested extensively against the SimpleSAMLphp IdP and can be used in production.

Supported protocols

The SAML standard refers to a flow of request/responses that make up one concrete action as a "protocol". Currently all of the basic Single-Sign-On and Single-Logout protocols are supported. There is no support at present for the optional Artifact Resolution, NameID Management, or NameID Mapping protocols.

Future work may add support for the Assertion Query protocol (which is useful to check if SSO is already available for a user without demanding they authenticate immediately).

Single sign-on protocols:

  • SP: send AuthnRequest (REDIRECT or POST) -> receive Response + Assertion (POST)

Single log-out protocols:

  • SP: send LogoutRequest (REDIRECT) -> receive LogoutResponse (REDIRECT or POST)
  • SP: receive LogoutRequest (REDIRECT OR POST) -> send LogoutResponse (REDIRECT)

esaml supports RSA+SHA1/SHA256 signing of all SP payloads, and validates signatures on all IdP responses. Compatibility flags are available to disable verification where IdP implementations lack support (see the esaml_sp record, and members such as idp_signs_logout_requests).

Assertion Encryption

The following algorithms are supported:

Encryption Algorithms
Key Encryption http://www.w3.org/2001/04/xmlenc#rsa-oaep-mgf1p
http://www.w3.org/2001/04/xmlenc#rsa-1_5
Data Encryption http://www.w3.org/2009/xmlenc11#aes128-gcm
http://www.w3.org/2001/04/xmlenc#aes128-cbc
http://www.w3.org/2001/04/xmlenc#aes256-cbc

API documentation

Edoc documentation for the whole API is available at:

https://hexdocs.pm/esaml

Licensing

2-clause BSD

Getting started

The simplest way to use esaml in your app is with the esaml_cowboy module. There are two SAML Server Provider (SP) applications included in the repo under examples directory.

The application in examples/sp directory shows how you can use esaml to enabled Single-Sign-On (SSO) in your application. This application enables an endpoint that supports Server Provider metadata request, SAML authentication request as well as the ability to consume the response from IdP.

The second application in example/sp_with_logout shows how Single Logout can be enabled. It also shows how you can build a bridge from esaml to local application session storage, by generating session cookies for each user that logs in (and storing them in ETS).

More advanced usage

You can also tap straight into lower-level APIs in esaml if esaml_cowboy doesn't meet your needs. The esaml_binding and esaml_sp modules are the interface used by esaml_cowboy itself, and contain all the basic primitives to generate and parse SAML payloads.

This is particularly useful if you want to implement SOAP endpoints using SAML.

The Elixir library Samly is one such implementation. It dose not use esaml_cowboy. Instead it relies on the lower-level APIs and uses Elixir Plug and Cowboy directly for endpoints/routing.

Contributions

Pull requests are always welcome for bug fixes and improvements. Fixes that enable compatibility with different IdP implementations are usually welcome, but please ensure they do not come at the expense of compatibility with another IdP. esaml prefers to follow as closely to the SAML standards as possible.

Bugs/issues opened without patches are also welcome, but might take a lot longer to be looked at. ;)