===========================================================================
 README file for mod_auth_mellon
===========================================================================

mod_auth_mellon is a authentication module for apache. It authenticates
the user against a SAML 2.0 IdP, and and grants access to directories
depending on attributes received from the IdP.


===========================================================================
 Dependencies
===========================================================================

mod_auth_mellon has four dependencies:
 * pkg-config
 * Apache (>=2.0)
 * OpenSSL
 * lasso (>=2.1)

You will also require developement headers and tools for all of the
dependencies.

If OpenSSL or lasso are installed in a "strange" directory, then you may
have to specify the directory containing "lasso.pc" and/or "openssl.pc" in
the PKG_CONFIG_PATH environment variable. For example, if openssl is
installed in /usr/local/openssl (with openssl.pc in
/usr/local/openssl/lib/pkgconfig/) and lasso is installed in /opt/lasso
(lasso.pc in /opt/lasso/lib/pkgconfig/), then you can set PKG_CONFIG_PATH
before running configure like this:

PKG_CONFIG_PATH=/usr/local/openssl/lib/pkgconfig:/opt/lasso/lib/pkgconfig
export PKG_CONFIG_PATH


If Apache is installed in a "strange" directory, then you may have to
specify the path to apxs2 using the --with-apxs2=/full/path/to/apxs2
option to configure. If, for example, Apache is installed in /opt/apache,
with apxs2 in /opt/apache/bin, then you run

./configure --with-apxs2=/opt/apache2/bin/apxs2

Note that, depending on your distribution,  apxs2 may be named apxs.


===========================================================================
 Installing mod_auth_mellon
===========================================================================

mod_auth_mellon uses autoconf, and can be installed by running the
following commands:

./configure
make
make install


===========================================================================
 Configuring mod_auth_mellon
===========================================================================

Here we are going to assume that your web servers hostname is
'example.com', and that the directory you are going to protect is
'http://example.com/secret/'. We are also going to assume that you have
configured your web site to use SSL.

You need to edit the configuration file for your web server. Depending on
your distribution, it may be named '/etc/apache/httpd.conf' or something
different.


You need to add a LoadModule directove for mod_auth_mellon. This will
look similar to this:

LoadModule auth_mellon_module /usr/lib/apache2/modules/mod_auth_mellon.so

To find the full path to mod_auth_mellon.so, you may run:

apxs2 -q LIBEXECDIR

This will print the path where Apache stores modules. mod_auth_mellon.so
will be stored in that directory.


After you have added the LoadModule directive, you must add configuration
for mod_auth_mellon. The following is an example configuration:


###########################################################################
# Global configuration for mod_auth_mellon. This configuration is shared by
# every virtual server and location in this instance of apache.
###########################################################################

# MellonCacheSize sets the maximum number of sessions which can be active
# at once. When mod_auth_mellon reaches this limit, it will begin removing
# the least recently used sessions. The server must be restarted before any
# changes to this option takes effect.
# Default: MellonCacheSize 100
MellonCacheSize 100

# MellonLockFile is the full path to a file used for synchronizing access
# to the session data. The path should only be used by one instance of
# apache at a time. The server must be restarted before any changes to this
# option takes effect.
# Default: MellonLockFile "/tmp/mellonLock"
MellonLockFile "/tmp/mellonLock"

###########################################################################
# End of global configuration for mod_auth_mellon.
###########################################################################


# This defines a directory where mod_auth_mellon should do access control.
<Location /secret>

        # These are standard Apache apache configuration directives.
        # See http://httpd.apache.org/docs/2.2/mod/core.html for information
        # about them.
        Require valid-user
        AuthType "Mellon"


        # MellonEnable is used to enable auth_mellon on a location.
        # It has three possible values: "off", "info" and "auth".
        # They have the following meanings:
        #   "off":  mod_auth_mellon will not do anything in this location.
        #           This is the default state.
        #   "info": If the user is authorized to access the resource, then
        #           we will populate the environment with information about
        #           the user. If the user isn't authorized, then we won't
        #           populate the environment, but we won't deny the user
        #           access either.
        #   "auth": We will populate the environment with information about
        #           the user if he is authorized. If he is authenticated
        #           (logged in), but not authorized (according to the
        #           MellonRequire directives, then we will return a 403
        #           Forbidden error. If he isn't authenticated then we will
        #           redirect him to the login page of the IdP.
        #
        # Default: MellonEnable "off"
        MellonEnable "auth"

        # MellonDecoder is used to select which decoder mod_auth_mellon
        # will use when decoding attribute values.
        # There are two possible values: "none" and "feide". "none" is the
        # default.
        # They have the following meanings:
        #   "none":  mod_auth_mellon will store the attribute as it is
        #            received from the IdP. This is the default behaviour.
        #   "feide": FEIDE currently stores several values in a single
        #            AttributeValue element. The values are base64 encoded
        #            and separated by a underscore. This decoder reverses
        #            this encoding.
        # Default: MellonDecoder "none"
        MellonDecoder "none"

        # MellonVariable is used to select the name of the cookie which
        # mod_auth_mellon should use to remember the session id. If you
        # want to have different sites running on the same host, then
        # you will have to choose a different name for the cookie for each
        # site.
        # Default: "cookie"
	MellonVariable "cookie"

        # MellonUser selects which attribute we should use for the username.
        # The username is passed on to other apache modules and to the web
        # page the user visits. NAME_ID is an attribute which we set to
        # the id we get from the IdP.
        # Default: MellonUser "NAME_ID"
	MellonUser "NAME_ID"

        # MellonSetEnv configuration directives allows you to map
        # attribute names received from the IdP to names you choose
        # yourself. The syntax is 'MellonSetEnv <local name> <IdP name>'.
        # You can list multiple MellonSetEnv directives.
        # Default. None set.
	MellonSetEnv "e-mail" "mail"

        # MellonRequire allows you to limit access to those with specific
        # attributes. The syntax is
        # 'MellonRequire <attribute name> <list of valid values>'.
        # Note that the attribute name is the name we received from the
        # IdP.
        #
        # If you don't list any MellonRequire directives, then any user
        # authenticated by the IdP will have access to this service. If
        # you list several MellonRequire directives, then all of them
        # will have to match.
        #
        # Default: None set.
	MellonRequire "eduPersonAffiliation" "student" "employee"

        # MellonEndpointPath selects which directory mod_auth_mellon
        # should assume contains the SAML 2.0 endpoints. Any request to
        # this directory will be handled by mod_auth_mellon.
        #
        # The path is the full path (from the root of the web server) to
        # the directory. The directory must be a sub-directory of this
        # <Location ...>.
        # Default: MellonEndpointPath "/mellon"
	MellonEndpointPath "/secret/endpoint"

        # MellonSessionLength sets the maximum lifetime of a session, in
        # seconds. The actual lifetime may be shorter, depending on the
        # conditions received from the IdP. The default length is 86400
        # seconds, which is one day.
        # Default: MellonSessionLength 86400
        MellonSessionLength 86400

        # MellonNoCookieErrorPage is the full path to a page which
        # mod_auth_mellon will redirect the user to if he returns from the
        # IdP without a cookie with a session id.
        # Note that the user may also get this error if he for some reason
        # loses the cookie between being redirected to the IdPs login page
        # and returning from it.
        # If this option is unset, then mod_auth_mellon will return a
        # 400 Bad Request error if the cookie is missing.
        # Default: unset
        MellonNoCookieErrorPage "https://example.com/no_cookie.html"

        # MellonSPMetadataFile is the full path to the file containing
        # the metadata for this service provider. You must configure this
        # before you can use this module.
        # Default: None set.
	MellonSPMetadataFile /etc/apache2/mellon/sp-metadata.xml

        # MellonSPPrivateKeyFile is a .pem file which contains the private
        # key of the service provider. The .pem-file cannot be encrypted
        # with a password. This directive is optional.
        # Default: None set.
	MellonSPPrivateKeyFile /etc/apache2/mellon/sp-private-key.pem

        # MellonIdPMetadataFile is the full path to the file which contains
        # metadata for the IdP you are authenticating against. This
        # directive is required.
        # Default: None set.
	MellonIdPMetadataFile /etc/apache2/mellon/idp-metadata.xml

        # MellonIdpPublicKeyFile is the full path of the public key of the
        # IdP. This parameter is optional if the public key is embedded
        # in the IdP's metadata file.
        # Default: None set.
	MellonIdPPublicKeyFile /etc/apache2/mellon/idp-public-key.pem
</Location>


===========================================================================
 Service provider metadata
===========================================================================

The contents of the metadata will depend on your hostname and on what path
you selected with the MellonEndpointPath configuration directive.

The following is an example of metadata for the example configuration:

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<EntityDescriptor
    entityID="examlpe.com"
    xmlns="urn:oasis:names:tc:SAML:2.0:metadata">
  <SPSSODescriptor
      AuthnRequestsSigned="false"
      WantAssertionsSigned="false"
      protocolSupportEnumeration="urn:oasis:names:tc:SAML:2.0:protocol">
    <SingleLogoutService
        Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect"
        Location="https://example.com/secret/endpoint/logout" />
    <NameIDFormat>
      urn:oasis:names:tc:SAML:2.0:nameid-format:transient
    </NameIDFormat>
    <AssertionConsumerService
        index="0"
        isDefault="true"
        Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST"
        Location="https://example.com/secret/endpoint/postResponse" />
  </SPSSODescriptor>
</EntityDescriptor>


You should update entityID="example.com" and the two Location attributes.
Note that '/secret/endpoint' in the two Location attributes matches the
path set in MellonEndpointPath.

To use HTTP-Artifact binding instead of the HTTP-POST binding, change
the AssertionConsumerService-element to something like this:

    <AssertionConsumerService
        index="0"
        isDefault="true"
        Binding="urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Artifact"
        Location="https://example.com/secret/endpoint/artifactResponse" />


===========================================================================
 Using mod_auth_mellon
===========================================================================

After you have set up mod_auth_mellon, you should be able to visit (in our
example) https://example.com/secret/, and be redirected to the IdP's login
page. After logging in you should be returned to
https://example.com/secret/, and get the contents of that page.

When authenticating a user, mod_auth_mellon will set some environment
variables to the attributes it received from the IdP. The name of the
variables will be MELLON_<attribute name>. If you have specified a
different name with the MellonSetEnv configuration directive, then that
name will be used instead. The name will still be prefixed by 'MELLON_'.

The value of the attribute will be base64 decoded.

mod_auth_mellon supports multivalued attributes with the following format:
<base64 encoded value>_<base64 encoded value>_<base 64 encoded value>...

If an attribute has multiple values, then they will be stored as
MELLON_<name>_0, MELLON_<name>_1, MELLON_<name>_2, ...

Since mod_auth_mellon doesn't know which attributes may have multiple
values, it will store every attribute at least twice. Once named
MELLON_<name>, and once named <MELLON_<name>_0.

In the case of multivalued attributes MELLON_<name> will contain the first
value.


The following code is a simple php-script which prints out all the
variables:

<?php
header('Content-Type: text/plain');

foreach($_SERVER as $key=>$value) {
  if(substr($key, 0, 7) == 'MELLON_') {
    echo($key . '=' . $value . "\r\n");
  }
}
?>