patrickallaert/php-saml

PHP SAML Toolkit, forked from onelogin/php-saml

1.0.3 2021-07-15 16:41 UTC

Requires

• php: >=7.1
• ext-curl: *
• ext-dom: *
• ext-libxml: *
• ext-openssl: *
• ext-zlib: *
• robrichards/xmlseclibs: ^3.0

Requires (Dev)

• phpunit/phpunit: ^7.5||^8.0
• slevomat/coding-standard: ^5.0
• squizlabs/php_codesniffer: ^3.4

Suggests

• ext-curl: Install curl lib to be able to use the IdPMetadataParser for parsing remote XMLs
• ext-gettext: Install gettext and php5-gettext libs to handle translations
• ext-openssl: Install openssl lib in order to handle with x509 certs (require to support sign and encryption)

MIT

• saml
• SAML2

README

Add SAML support to your PHP software using this library.

Warning

This version is compatible with PHP 7.1+ and does not include xmlseclibs (you will need to install it via composer, dependency described in composer.json)

Why add SAML support to my software?

SAML is an XML-based standard for web browser single sign-on and is defined by the OASIS Security Services Technical Committee. The standard has been around since 2002, but lately it is becoming popular due its advantages:

• Usability - One-click access from portals or intranets, deep linking, password elimination and automatically renewing sessions make life easier for the user.
• Security - Based on strong digital signatures for authentication and integrity, SAML is a secure single sign-on protocol that the largest and most security conscious enterprises in the world rely on.
• Speed - SAML is fast. One browser redirect is all it takes to securely sign a user into an application.
• Phishing Prevention - If you don’t have a password for an app, you can’t be tricked into entering it on a fake login page.
• IT Friendly - SAML simplifies life for IT because it centralizes authentication, provides greater visibility and makes directory integration easier.
• Opportunity - B2B cloud vendor should support SAML to facilitate the integration of their product.

General description

SAML PHP toolkit let you build a SP (Service Provider) over your PHP application and connect it to any IdP (Identity Provider).

Supports:

• SSO and SLO (SP-Initiated and IdP-Initiated).
• Assertion and nameId encryption.
• Assertion signature.
• Message signature: AuthNRequest, LogoutRequest, LogoutResponses.
• Enable an Assertion Consumer Service endpoint.
• Enable a Single Logout Service endpoint.
• Publish the SP metadata (which can be signed).

Key features:

• saml2int - Implements the SAML 2.0 Web Browser SSO Profile.
• Session-less - Forget those common conflicts between the SP and the final app, the toolkit delegate session in the final app.
• Easy to use - Programmer will be allowed to code high-level and low-level programming, 2 easy to use APIs are available.
• Tested - Thoroughly tested.
• Popular - Many PHP SAML plugins uses it.

Installation

Dependencies

• php >= 7.1 and some core extensions like php-xml, php-date, php-zlib.
• openssl. Install the openssl library. It handles x509 certificates.
• gettext. Install that library and its php driver. It handles translations.
• curl. Install that library and its php driver if you plan to use the IdP Metadata parser.

Code

Option 1. Download from github

The toolkit is hosted on github. You can download it from:

• https://github.com/patrickallaert/php-saml/releases

Option 2. Composer

The toolkit supports composer. You can find the patrickallaert/php-saml package at https://packagist.org/packages/patrickallaert/php-saml

In order to import the saml toolkit to your current php project, execute

composer require patrickallaert/php-saml

Important In this option, the x509 certs must be stored at vendor/patrickallaert/php-saml/certs and settings file stored at vendor/patrickallaert/php-saml.

Your settings are at risk of being deleted when updating packages using composer update or similar commands. So it is highly recommended that instead of using settings files, you pass the settings as an array directly to the constructor (explained later in this document). If you do not use this approach your settings are at risk of being deleted when updating packages using composer update or similar commands.

Security warning

In production, the strict parameter MUST be set as "true" and the signatureAlgorithm and digestAlgorithm under security must be set to something other than SHA1 (see https://shattered.io/ ). Otherwise your environment is not secure and will be exposed to attacks.

In production also we highly recommended to register on the settings the IdP certificate instead of using the fingerprint method. The fingerprint, is a hash, so at the end is open to a collision attack that can end on a signature validation bypass. Other SAML toolkits deprecated that mechanism, we maintain it for compatibility and also to be used on test environment.

Getting started

Knowing the toolkit

The SAML Toolkit contains different folders (certs, endpoints, lib, demo, etc.) and some files.

Let's start describing the folders:

certs/

SAML requires a x509 cert to sign and encrypt elements like NameID, Message, Assertion, Metadata.

If our environment requires sign or encrypt support, this folder may contain the x509 cert and the private key that the SP will use:

• sp.crt - The public cert of the SP
• sp.key - The private key of the SP

Or also we can provide those data in the setting file at the $settings['sp']['x509cert'] and the $settings['sp']['privateKey'].

Sometimes we could need a signature on the metadata published by the SP, in this case we could use the x509 cert previously mentioned or use a new x.509 cert: metadata.crt and metadata.key.

Use sp_new.crt if you are in a key rollover process and you want to publish that x509 certificate on Service Provider metadata.

src/

This folder contains the heart of the toolkit, the libraries:

• Saml2 folder contains the new version of the classes and methods that are described in a later section.

doc/

This folder contains the API documentation of the toolkit.

endpoints/

The toolkit has three endpoints:

• metadata.php - Where the metadata of the SP is published.
• acs.php - Assertion Consumer Service. Processes the SAML Responses.
• sls.php - Single Logout Service. Processes Logout Requests and Logout Responses.

You can use the files provided by the toolkit or create your own endpoints files when adding SAML support to your applications. Take in mind that those endpoints files uses the setting file of the toolkit's base folder.

locale/

Locale folder contains some translations: en_US and es_ES as a proof of concept. Currently there are no translations but we will eventually localize the messages and support multiple languages.

Other important files

• settings_example.php - A template to be used in order to create a settings.php file which contains the basic configuration info of the toolkit.
• advanced_settings_example.php - A template to be used in order to create a advanced_settings.php file which contains extra configuration info related to the security, the contact person, and the organization associated to the SP.

Miscellaneous

• tests/ - Contains the unit test of the toolkit.
• demo1/ - Contains an example of a simple PHP app with SAML support. Read the Readme.txt inside for more info.
• demo2/ - Contains another example.

How it works

Settings

First of all we need to configure the toolkit. The SP's info, the IdP's info, and in some cases, configure advanced security issues like signatures and encryption.

There are two ways to provide the settings information:

• Use a settings.php file that we should locate at the base folder of the toolkit.
• Use an array with the setting data and provide it directly to the constructor of the class.

There is a template file, settings_example.php, so you can make a copy of this file, rename and edit it.

<?php

$settings = array(
    // If 'strict' is True, then the PHP Toolkit will reject unsigned
    // or unencrypted messages if it expects them to be signed or encrypted.
    // Also it will reject the messages if the SAML standard is not strictly
    // followed: Destination, NameId, Conditions ... are validated too.
    'strict' => false,

    // Set a BaseURL to be used instead of try to guess
    // the BaseURL of the view that process the SAML Message.
    // Ex http://sp.example.com/
    //    http://example.com/sp/
    'baseurl' => null,

    // Service Provider Data that we are deploying.
    'sp' => array(
        // Identifier of the SP entity  (must be a URI)
        'entityId' => '',
        // Specifies info about where and how the <AuthnResponse> message MUST be
        // returned to the requester, in this case our SP.
        'assertionConsumerService' => array(
            // URL Location where the <Response> from the IdP will be returned
            'url' => '',
            // SAML protocol binding to be used when returning the <Response>
            // message. Toolkit supports this endpoint for the
            // HTTP-POST binding only.
            'binding' => 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST',
        ),
        // If you need to specify requested attributes, set a
        // attributeConsumingService. nameFormat, attributeValue and
        // friendlyName can be omitted
        "attributeConsumingService"=> array(
                "serviceName" => "SP test",
                "serviceDescription" => "Test Service",
                "requestedAttributes" => array(
                    array(
                        "name" => "",
                        "isRequired" => false,
                        "nameFormat" => "",
                        "friendlyName" => "",
                        "attributeValue" => array()
                    )
                )
        ),
        // Specifies info about where and how the <Logout Response> message MUST be
        // returned to the requester, in this case our SP.
        'singleLogoutService' => array(
            // URL Location where the <Response> from the IdP will be returned
            'url' => '',
            // SAML protocol binding to be used when returning the <Response>
            // message. Toolkit supports the HTTP-Redirect binding
            // only for this endpoint.
            'binding' => 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect',
        ),
        // Specifies the constraints on the name identifier to be used to
        // represent the requested subject.
        // Take a look on lib/Saml2/Constants.php to see the NameIdFormat supported.
        'NameIDFormat' => 'urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress',
        // Usually x509cert and privateKey of the SP are provided by files placed at
        // the certs folder. But we can also provide them with the following parameters
        'x509cert' => '',
        'privateKey' => '',

        /*
         * Key rollover
         * If you plan to update the SP x509cert and privateKey
         * you can define here the new x509cert and it will be
         * published on the SP metadata so Identity Providers can
         * read them and get ready for rollover.
         */
        // 'x509certNew' => '',
    ),

    // Identity Provider Data that we want connected with our SP.
    'idp' => array(
        // Identifier of the IdP entity  (must be a URI)
        'entityId' => '',
        // SSO endpoint info of the IdP. (Authentication Request protocol)
        'singleSignOnService' => array(
            // URL Target of the IdP where the Authentication Request Message
            // will be sent.
            'url' => '',
            // SAML protocol binding to be used when returning the <Response>
            // message. Toolkit supports the HTTP-Redirect binding
            // only for this endpoint.
            'binding' => 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect',
        ),
        // SLO endpoint info of the IdP.
        'singleLogoutService' => array(
            // URL Location of the IdP where SLO Request will be sent.
            'url' => '',
            // SAML protocol binding to be used when returning the <Response>
            // message. Toolkit supports the HTTP-Redirect binding
            // only for this endpoint.
            'binding' => 'urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect',
        ),
        // Public x509 certificate of the IdP
        'x509cert' => '',
        /*
         *  Instead of use the whole x509cert you can use a fingerprint in order to
         *  validate a SAMLResponse, but we don't recommend to use that
         *  method on production since is exploitable by a collision attack.
         *  (openssl x509 -noout -fingerprint -in "idp.crt" to generate it,
         *   or add for example the -sha256 , -sha384 or -sha512 parameter)
         *
         *  If a fingerprint is provided, then the certFingerprintAlgorithm is required in order to
         *  let the toolkit know which algorithm was used. Possible values: sha1, sha256, sha384 or sha512
         *  'sha1' is the default value.
         *
         *  Notice that if you want to validate any SAML Message sent by the HTTP-Redirect binding, you
         *  will need to provide the whole x509cert.
         */
        // 'certFingerprint' => '',
        // 'certFingerprintAlgorithm' => 'sha1',

        /* In some scenarios the IdP uses different certificates for
         * signing/encryption, or is under key rollover phase and
         * more than one certificate is published on IdP metadata.
         * In order to handle that the toolkit offers that parameter.
         * (when used, 'x509cert' and 'certFingerprint' values are
         * ignored).
         */
        // 'x509certMulti' => array(
        //      'signing' => array(
        //          0 => '<cert1-string>',
        //      ),
        //      'encryption' => array(
        //          0 => '<cert2-string>',
        //      )
        // ),
    ),
);

In addition to the required settings data (IdP, SP), there is extra information that could be defined. In the same way that a template exists for the basic info, there is a template for that advanced info located at the base folder of the toolkit and named advanced_settings_example.php that you can copy and rename it as advanced_settings.php

<?php

$advancedSettings = array(

    // Compression settings
    'compress' => array(
        'requests' => true,
        'responses' => true
    ),
    // Security settings
    'security' => array(

        /** signatures and encryptions offered */

        // Indicates that the nameID of the <samlp:logoutRequest> sent by this SP
        // will be encrypted.
        'nameIdEncrypted' => false,

        // Indicates whether the <samlp:AuthnRequest> messages sent by this SP
        // will be signed.  [Metadata of the SP will offer this info]
        'authnRequestsSigned' => false,

        // Indicates whether the <samlp:logoutRequest> messages sent by this SP
        // will be signed.
        'logoutRequestSigned' => false,

        // Indicates whether the <samlp:logoutResponse> messages sent by this SP
        // will be signed.
        'logoutResponseSigned' => false,

        /* Sign the Metadata
         False || True (use sp certs) || array(
                                                    keyFileName => 'metadata.key',
                                                    certFileName => 'metadata.crt'
                                                )
        */
        'signMetadata' => false,

        /** signatures and encryptions required **/

        // Indicates a requirement for the <samlp:Response>, <samlp:LogoutRequest>
        // and <samlp:LogoutResponse> elements received by this SP to be signed.
        'wantMessagesSigned' => false,

        // Indicates a requirement for the <saml:Assertion> elements received by
        // this SP to be encrypted.
        'wantAssertionsEncrypted' => false,

        // Indicates a requirement for the <saml:Assertion> elements received by
        // this SP to be signed. [Metadata of the SP will offer this info]
        'wantAssertionsSigned' => false,

        // Indicates a requirement for the NameID element on the SAMLResponse
        // received by this SP to be present.
        'wantNameId' => true,

        // Indicates a requirement for the NameID received by
        // this SP to be encrypted.
        'wantNameIdEncrypted' => false,

        // Authentication context.
        // Set to false and no AuthContext will be sent in the AuthNRequest.
        // Set true or don't present this parameter and you will get an AuthContext 'exact' 'urn:oasis:names:tc:SAML:2.0:ac:classes:PasswordProtectedTransport'.
        // Set an array with the possible auth context values: array('urn:oasis:names:tc:SAML:2.0:ac:classes:Password', 'urn:oasis:names:tc:SAML:2.0:ac:classes:X509').
        'requestedAuthnContext' => true,

        // Indicates if the SP will validate all received xmls.
        // (In order to validate the xml, 'strict' and 'wantXMLValidation' must be true).
        'wantXMLValidation' => true,

        // If true, SAMLResponses with an empty value at its Destination
        // attribute will not be rejected for this fact.
        'relaxDestinationValidation' => false,

        // Algorithm that the toolkit will use on signing process. Options:
        //    'http://www.w3.org/2000/09/xmldsig#rsa-sha1'
        //    'http://www.w3.org/2000/09/xmldsig#dsa-sha1'
        //    'http://www.w3.org/2001/04/xmldsig-more#rsa-sha256'
        //    'http://www.w3.org/2001/04/xmldsig-more#rsa-sha384'
        //    'http://www.w3.org/2001/04/xmldsig-more#rsa-sha512'
        // Notice that rsa-sha1 is a deprecated algorithm and should not be used
        'signatureAlgorithm' => 'http://www.w3.org/2001/04/xmldsig-more#rsa-sha256',

        // Algorithm that the toolkit will use on digest process. Options:
        //    'http://www.w3.org/2000/09/xmldsig#sha1'
        //    'http://www.w3.org/2001/04/xmlenc#sha256'
        //    'http://www.w3.org/2001/04/xmldsig-more#sha384'
        //    'http://www.w3.org/2001/04/xmlenc#sha512'
        // Notice that sha1 is a deprecated algorithm and should not be used
        'digestAlgorithm' => 'http://www.w3.org/2001/04/xmlenc#sha256',

        // ADFS URL-Encodes SAML data as lowercase, and the toolkit by default uses
        // uppercase. Turn it True for ADFS compatibility on signature verification
        'lowercaseUrlencoding' => false,
    ),

    // Contact information template, it is recommended to supply a
    // technical and support contacts.
    'contactPerson' => array(
        'technical' => array(
            'givenName' => '',
            'emailAddress' => ''
        ),
        'support' => array(
            'givenName' => '',
            'emailAddress' => ''
        ),
    ),

    // Organization information template, the info in en_US lang is
    // recomended, add more if required.
    'organization' => array(
        'en-US' => array(
            'name' => '',
            'displayname' => '',
            'url' => ''
        ),
    ),
);

The compression settings allow you to instruct whether or not the IdP can accept data that has been compressed using gzip ('requests' and 'responses'). But if we provide a $deflate boolean parameter to the getRequest or getResponse method it will have priority over the compression settings.

In the security section, you can set the way that the SP will handle the messages and assertions. Contact the admin of the IdP and ask him what the IdP expects, and decide what validations will handle the SP and what requirements the SP will have and communicate them to the IdP's admin too.

Once we know what kind of data could be configured, let's talk about the way settings are handled within the toolkit.

The settings files described (settings.php and advanced_settings.php) are loaded by the toolkit if no other array with settings info is provided in the constructor of the toolkit. Let's see some examples.

// Initializes toolkit with settings.php & advanced_settings files.
$auth = new Saml2\Auth();
//or
$settings = new Saml2\Settings();

// Initializes toolkit with the array provided.
$auth = new Saml2\Auth($settingsInfo);
//or
$settings = new Saml2\Settings($settingsInfo);

You can declare the $settingsInfo in the file that contains the constructor execution or locate them in any file and load the file in order to get the array available as we see in the following example:

<?php

require_once 'custom_settings.php';  // The custom_settings.php contains a
                                     // $settingsInfo array.

$auth = new Saml2\Auth($settingsInfo);

How load the library

Use composer's vendor/autoload.php script if you used composer to install this library.

Otherwise, use a PSR-4 capable loader mechanism, knowing that namespace Saml2\ should be matched against the src/Saml2 folder.

Initiate SSO

In order to send an AuthNRequest to the IdP:

<?php

$auth = new Saml2\Auth(); // Constructor of the SP, loads settings.php
                                   // and advanced_settings.php
$auth->login();   // Method that sent the AuthNRequest

The AuthNRequest will be sent signed or unsigned based on the security info of the advanced_settings.php ('authnRequestsSigned').

The IdP will then return the SAML Response to the user's client. The client is then forwarded to the Attribute Consumer Service of the SP with this information. If we do not set a 'url' param in the login method and we are using the default ACS provided by the toolkit (endpoints/acs.php), then the ACS endpoint will redirect the user to the file that launched the SSO request.

We can set a 'returnTo' url to change the workflow and redirect the user to the other PHP file.

$newTargetUrl = 'http://example.com/consume2.php';
$auth = new Saml2\Auth();
$auth->login($newTargetUrl);

The login method can receive other five optional parameters:

• $parameters - An array of parameters that will be added to the GET in the HTTP-Redirect.
• $forceAuthn - When true the AuthNRequest will set the ForceAuthn='true'
• $isPassive - When true the AuthNRequest will set the Ispassive='true'
• $strict - True if we want to stay (returns the url string) False to redirect
• $setNameIdPolicy - When true the AuthNRequest will set a nameIdPolicy element.

If a match on the future SAMLResponse ID and the AuthNRequest ID to be sent is required, that AuthNRequest ID must to be extracted and saved.

$ssoBuiltUrl = $auth->login(null, array(), false, false, true);
$_SESSION['AuthNRequestID'] = $auth->getLastRequestID();
header('Pragma: no-cache');
header('Cache-Control: no-cache, must-revalidate');
header('Location: ' . $ssoBuiltUrl);
exit();

The SP Endpoints

Related to the SP there are three important views: The metadata view, the ACS view and the SLS view. The toolkit provides examples of those views in the endpoints directory.

SP Metadata endpoints/metadata.php

This code will provide the XML metadata file of our SP, based on the info that we provided in the settings files.

<?php

try {
    $auth = new Saml2\Auth();
    $settings = $auth->getSettings();
    $metadata = $settings->getSPMetadata();
    $errors = $settings->validateMetadata($metadata);
    if (empty($errors)) {
        header('Content-Type: text/xml');
        echo $metadata;
    } else {
        throw new Saml2\Error(
            'Invalid SP metadata: '.implode(', ', $errors),
            Saml2\Error::METADATA_SP_INVALID
        );
    }
} catch (Exception $e) {
    echo $e->getMessage();
}

The getSPMetadata will return the metadata signed or not based on the security info of the advanced_settings.php ('signMetadata').

Before the XML metadata is exposed, a check takes place to ensure that the info to be provided is valid.

Instead of use the Auth object, you can directly use

$settings = new Saml2\Settings($settingsInfo, true);

to get the settings object and with the true parameter we will avoid the IdP Settings validation.

Attribute Consumer Service(ACS) endpoints/acs.php

This code handles the SAML response that the IdP forwards to the SP through the user's client.

<?php

session_start();  // IMPORTANT: This is required in order to be able
                  // to store the user data in the session.

$auth = new Saml2\Auth();

$auth->processResponse($_SESSION['AuthNRequestID'] ?? null);
unset($_SESSION['AuthNRequestID']);

$errors = $auth->getErrors();

if (!empty($errors)) {
    echo '<p>' . implode(', ', $errors) . '</p>';
    exit();
}

if (!$auth->isAuthenticated()) {
    echo "<p>Not authenticated</p>";
    exit();
}

$_SESSION['samlUserdata'] = $auth->getAttributes();
$_SESSION['samlNameId'] = $auth->getNameId();
$_SESSION['samlNameIdFormat'] = $auth->getNameIdFormat();
$_SESSION['samlNameidNameQualifier' = $auth->getNameIdNameQualifier();
$_SESSION['samlNameidSPNameQualifier' = $auth->getNameIdSPNameQualifier();
$_SESSION['samlSessionIndex'] = $auth->getSessionIndex();

if (isset($_POST['RelayState']) && Saml2\Utils::getSelfURL() != $_POST['RelayState']) {
    $auth->redirectTo($_POST['RelayState']);
}

$attributes = $_SESSION['samlUserdata'];
$nameId = $_SESSION['samlNameId'];

echo '<h1>Identified user: '. htmlentities($nameId) .'</h1>';

if (!empty($attributes)) {
    echo '<h2>' . _('User attributes:') . '</h2>';
    echo '<table><thead><th>' . _('Name') . '</th><th>' . _('Values') . '</th></thead><tbody>';
    foreach ($attributes as $attributeName => $attributeValues) {
        echo '<tr><td>' . htmlentities($attributeName) . '</td><td><ul>';
        foreach ($attributeValues as $attributeValue) {
            echo '<li>' . htmlentities($attributeValue) . '</li>';
        }
        echo '</ul></td></tr>';
    }
    echo '</tbody></table>';
} else {
    echo _('No attributes found.');
}

The SAML response is processed and then checked that there are no errors. It also verifies that the user is authenticated and stored the userdata in session.

At that point there are two possible alternatives:

1. If no RelayState is provided, we could show the user data in this view or however we wanted.

2. If RelayState is provided, a redirection takes place.

Notice that we saved the user data in the session before the redirection to have the user data available at the RelayState view.

The getAttributes method

In order to retrieve attributes we can use:

$attributes = $auth->getAttributes();

With this method we get all the user data provided by the IdP in the Assertion of the SAML Response.

If we execute print_r($attributes) we could get:

Array
(
    [cn] => Array
        (
            [0] => John
        )
    [sn] => Array
        (
            [0] => Doe
        )
    [mail] => Array
        (
            [0] => [e-mail]
        )
    [groups] => Array
        (
            [0] => users
            [1] => members
        )
)

Each attribute name can be used as an index into $attributes to obtain the value. Every attribute value is an array - a single-valued attribute is an array of a single element.

The following code is equivalent:

$attributes = $auth->getAttributes();
print_r($attributes['cn']);

print_r($auth->getAttribute('cn'));

Before trying to get an attribute, check that the user is authenticated. If the user isn't authenticated or if there were no attributes in the SAML assertion, an empty array will be returned. For example, if we call to getAttributes before a $auth->processResponse, the getAttributes() will return an empty array.

Single Logout Service (SLS) endpoints/sls.php

This code handles the Logout Request and the Logout Responses.

<?php

session_start();  // IMPORTANT: This is required in order to be able
                  // to close the user session.

$auth = new Saml2\Auth();

$auth->processSLO(false, $_SESSION['LogoutRequestID'] ?? null);

$errors = $auth->getErrors();

if (empty($errors)) {
    echo 'Sucessfully logged out';
} else {
    echo implode(', ', $errors);
}

If the SLS endpoints receives a Logout Response, the response is validated and the session could be closed

// part of the processSLO method

$logoutResponse = new Saml2\LogoutResponse($this->_settings, $_GET['SAMLResponse']);
if (!$logoutResponse->isValid($requestId)) {
    $this->_errors[] = 'invalid_logout_response';
} else if ($logoutResponse->getStatus() !== Saml2\Constants::STATUS_SUCCESS) {
    $this->_errors[] = 'logout_not_success';
} else {
    if (!$keepLocalSession) {
        Saml2\Utils::deleteLocalSession();
    }
}

If the SLS endpoints receives an Logout Request, the request is validated, the session is closed and a Logout Response is sent to the SLS endpoint of the IdP.

// part of the processSLO method

$request = gzinflate(base64_decode($_GET['SAMLRequest']));
if (!Saml2\LogoutRequest::isValid($this->_settings, $request)) {
    $this->_errors[] = 'invalid_logout_request';
} else {
    if (!$keepLocalSession) {
        Saml2\Utils::deleteLocalSession();
    }

    $inResponseTo = $request->id;
    $responseBuilder = new Saml2\LogoutResponse($this->_settings);
    $responseBuilder->build($inResponseTo);
    $logoutResponse = $responseBuilder->getResponse();

    $parameters = array('SAMLResponse' => $logoutResponse);
    if (isset($_GET['RelayState'])) {
        $parameters['RelayState'] = $_GET['RelayState'];
    }

    $security = $this->_settings->getSecurityData();
    if (isset($security['logoutResponseSigned']) && $security['logoutResponseSigned']) {
        $signature = $this->buildResponseSignature($logoutResponse, $parameters['RelayState'], $security['signatureAlgorithm']);
        $parameters['SigAlg'] = $security['signatureAlgorithm'];
        $parameters['Signature'] = $signature;
    }

    $this->redirectTo($this->getSLOurl(), $parameters);
}

If you aren't using the default PHP session, or otherwise need a manual way to destroy the session, you can pass a callback method to the processSLO method as the fourth parameter

$keepLocalSession = False;
$callback = function () {
    // Destroy user session
};

$auth->processSLO($keepLocalSession, null, false, $callback);

If we don't want that processSLO to destroy the session, pass a true parameter to the processSLO method

$keepLocalSession = True;
$auth->processSLO($keepLocalSession);

Initiate SLO

In order to send a Logout Request to the IdP:

<?php

$auth = new Saml2\Auth();

$auth->logout();   // Method that sent the Logout Request.

Also there are eight optional parameters that can be set:

• $returnTo - The target URL the user should be returned to after logout.
• $parameters - Extra parameters to be added to the GET.
• $name_id - That will be used to build the LogoutRequest. If name_id parameter is not set and the auth object processed a SAML Response with a NameId, then this NameId will be used.
• $session_index - SessionIndex that identifies the session of the user.
• $stay - True if we want to stay (returns the url string) False to redirect.
• $nameIdFormat - The NameID Format will be set in the LogoutRequest.
• $nameIdNameQualifier - The NameID NameQualifier will be set in the LogoutRequest.
• $nameIdSPNameQualifier - The NameID SP NameQualifier will be set in the LogoutRequest.

The Logout Request will be sent signed or unsigned based on the security info of the advanced_settings.php ('logoutRequestSigned').

The IdP will return the Logout Response through the user's client to the Single Logout Service of the SP. If we do not set a 'url' param in the logout method and are using the default SLS provided by the toolkit (endpoints/sls.php), then the SLS endpoint will redirect the user to the file that launched the SLO request.

We can set an 'returnTo' url to change the workflow and redirect the user to other php file.

$newTargetUrl = 'http://example.com/loggedOut.php';
$auth = new Saml2\Auth();
$auth->logout($newTargetUrl);

A more complex logout with all the parameters:

$auth = new Saml2\Auth();

$auth->logout(
    null,
    [],
    $_SESSION['samlNameId'] ?? null,
    $_SESSION['samlSessionIndex'] ?? null,
    false,
    $_SESSION['samlNameIdFormat'] ?? null,
    $_SESSION['samlNameIdNameQualifier'] ?? null,
    $_SESSION['samlNameIdSPNameQualifier'] ?? null
);

If a match on the future LogoutResponse ID and the LogoutRequest ID to be sent is required, that LogoutRequest ID must to be extracted and stored.

$sloBuiltUrl = $auth->logout(null, [], $nameId, $sessionIndex, true);
$_SESSION['LogoutRequestID'] = $auth->getLastRequestID();
header('Pragma: no-cache');
header('Cache-Control: no-cache, must-revalidate');
header('Location: ' . $sloBuiltUrl);
exit();

Example of a view that initiates the SSO request and handles the response (is the acs target)

We can code a unique file that initiates the SSO process, handle the response, get the attributes, initiate the SLO and processes the logout response.

Note: Review the demo1 folder that contains that use case; in a later section we explain the demo1 use case further in detail.

<?php

session_start();    // Initialize the session, we do that because
                    // Note that processResponse and processSLO
                    // methods could manipulate/close that session

require_once __DIR__ . "/../vendor/autoload.php";
require_once 'settings.php';    // Load the setting info as an Array

$auth = new Saml2\Auth($settingsInfo);  // Initialize the SP SAML instance

if (isset($_GET['sso'])) {    // SSO action.  Will send an AuthNRequest to the IdP
    $auth->login();
} else if (isset($_GET['sso2'])) {              // Another SSO action
    $returnTo = $spBaseUrl.'/demo1/attrs.php';  // but set a custom RelayState URL
    $auth->login($returnTo);
} else if (isset($_GET['slo'])) {  // SLO action. Will sent a Logout Request to IdP
    $auth->logout();
} else if (isset($_GET['acs'])) {  // Assertion Consumer Service
    $auth->processResponse();      // Process the Response of the IdP, get the
                                   // attributes and put then at
                                   // $_SESSION['samlUserdata']

    $errors = $auth->getErrors();  // This method receives an array with the errors
                                   // that could took place during the process

    if (!empty($errors)) {
        echo '<p>' . implode(', ', $errors) . '</p>';
    }
                                          // This check if the response was
    if (!$auth->isAuthenticated()) {      // sucessfully validated and the user
        echo '<p>Not authenticated</p>';  // data retrieved or not
        exit();
    }

    $_SESSION['samlUserdata'] = $auth->getAttributes(); // Retrieves user data
    if (isset($_POST['RelayState']) && Saml2\Utils::getSelfURL() != $_POST['RelayState']) {
        $auth->redirectTo($_POST['RelayState']);  // Redirect if there is a
    }                                             // relayState set
} else if (isset($_GET['sls'])) {   // Single Logout Service
    $auth->processSLO();            // Process the Logout Request & Logout Response
    $errors = $auth->getErrors(); // Retrieves possible validation errors
    if (empty($errors)) {
        echo '<p>Sucessfully logged out</p>';
    } else {
        echo '<p>' . implode(', ', $errors) . '</p>';
    }
}

if (isset($_SESSION['samlUserdata'])) {   // If there is user data we print it.
    if (!empty($_SESSION['samlUserdata'])) {
        $attributes = $_SESSION['samlUserdata'];
        echo 'You have the following attributes:<br>';
        echo '<table><thead><th>Name</th><th>Values</th></thead><tbody>';
        foreach ($attributes as $attributeName => $attributeValues) {
            echo '<tr><td>' . htmlentities($attributeName) . '</td><td><ul>';
            foreach ($attributeValues as $attributeValue) {
                echo '<li>' . htmlentities($attributeValue) . '</li>';
            }
            echo '</ul></td></tr>';
        }
        echo '</tbody></table>';
    } else {                             // If there is not user data, we notify
        echo "<p>You don't have any attribute</p>";
    }

    echo '<p><a href="?slo" >Logout</a></p>'; // Print some links with possible
} else {                                      // actions
    echo '<p><a href="?sso" >Login</a></p>';
    echo '<p><a href="?sso2" >Login and access to attrs.php page</a></p>';
}

URL-guessing methods

php-saml toolkit uses a bunch of methods in Saml2\Utils that try to guess the URL where the SAML messages are processed.

• getSelfHost Returns the current host.
• getSelfPort Return the port number used for the request
• isHTTPS Checks if the protocol is https or http.
• getSelfURLhost Returns the protocol + the current host + the port (if different than common ports).
• getSelfURL Returns the URL of the current host + current view + query.
• getSelfURLNoQuery Returns the URL of the current host + current view.
• getSelfRoutedURLNoQuery Returns the routed URL of the current host + current view.

getSelfURLNoQuery and getSelfRoutedURLNoQuery are used to calculate the currentURL in order to valdate SAML elements like Destination or Recipient.

When the PHP application is behind a proxy or a load balancer we can execute setProxyVars(true) and setSelfPort and isHTTPS will take care of the $_SERVER["HTTP_X_FORWARDED_PORT"] and $_SERVER['HTTP_X_FORWARDED_PROTO'] vars (otherwise they are ignored).

Also a developer can use setSelfProtocol, setSelfHost, setSelfPort and getBaseURLPath to define a specific value to be returned by isHTTPS, getSelfHost, getSelfPort and getBaseURLPath. And define a setBasePath to be used on the getSelfURL and getSelfRoutedURLNoQuery to replace the data extracted from $_SERVER["REQUEST_URI"].

At the settings the developer will be able to set a 'baseurl' parameter that automatically will use setBaseURL to set values for setSelfProtocol, setSelfHost, setSelfPort and setBaseURLPath.

Working behind load balancer

Is possible that asserting request URL and Destination attribute of SAML response fails when working behind load balancer with SSL offload.

You should be able to workaround this by configuring your server so that it is aware of the proxy and returns the original url when requested.

Or by using the method described on the previous section.

SP Key rollover

If you plan to update the SP x509cert and privateKey you can define the new x509cert as $settings['sp']['x509certNew'] and it will be published on the SP metadata so Identity Providers can read them and get ready for rollover.

IdP with multiple certificates

In some scenarios the IdP uses different certificates for signing/encryption, or is under key rollover phase and more than one certificate is published on IdP metadata.

In order to handle that the toolkit offers the $settings['idp']['x509certMulti'] parameter.

When that parameter is used, 'x509cert' and 'certFingerprint' values will be ignored by the toolkit.

The x509certMulti is an array with 2 keys:

• signing. An array of certs that will be used to validate IdP signature
• encryption An array with one unique cert that will be used to encrypt data to be sent to the IdP

Replay attacks

In order to avoid replay attacks, you can store the ID of the SAML messages already processed, to avoid processing them twice. Since the Messages expires and will be invalidated due that fact, you don't need to store those IDs longer than the time frame that you currently accepting.

Get the ID of the last processed message/assertion with the getLastMessageId/getLastAssertionId methods of the Auth object.

Main classes and methods

Described below are the main classes and methods that can be invoked.

Saml2 library

Lets describe now the classes and methods of the SAML2 library.

Saml2\Auth - Auth.php

Main class of PHP Toolkit

• Auth - Initializes the SP SAML instance
• login - Initiates the SSO process.
• logout - Initiates the SLO process.
• processResponse - Process the SAML Response sent by the IdP.
• processSLO - Process the SAML Logout Response / Logout Request sent by the IdP.
• redirectTo - Redirects the user to the url past by parameter or to the url that we defined in our SSO Request.
• isAuthenticated - Checks if the user is authenticated or not.
• getAttributes - Returns the set of SAML attributes.
• getAttribute - Returns the requested SAML attribute
• getNameId - Returns the nameID
• getNameIdFormat - Gets the NameID Format provided by the SAML response from the IdP.
• getNameIdNameQualifier - Gets the NameID NameQualifier provided from the SAML Response String.
• getNameIdNameSPQualifier - Gets the NameID SP NameQualifier provided from the SAML Response String.
• getSessionIndex - Gets the SessionIndex from the AuthnStatement.
• getErrors - Returns if there were any error
• getLastRequestID - The ID of the last Request SAML message generated.
• buildRequestSignature - Generates the Signature for a SAML Request
• buildResponseSignature - Generates the Signature for a SAML Response
• getSettings - Returns the settings info
• setStrict - Set the strict mode active/disable
• getLastRequestID - Gets the ID of the last AuthNRequest or LogoutRequest generated by the Service Provider.

Saml2\AuthnRequest - AuthnRequest.php

SAML 2 Authentication Request class

• AuthnRequest - Constructs the AuthnRequest object.
• getRequest - Returns deflated, base64 encoded, unsigned AuthnRequest.
• getId - Returns the AuthNRequest ID.

Saml2\Response - Response.php

SAML 2 Authentication Response class

• Response - Constructs the SAML Response object.
• isValid - Determines if the SAML Response is valid using the certificate.
• checkStatus - Checks if the Status is success.
• getAudiences - Gets the audiences.
• getIssuers - Gets the Issuers (from Response and Assertion)
• getNameIdData - Gets the NameID Data provided by the SAML response from the IdP.
• getNameId - Gets the NameID provided by the SAML response from the IdP.
• getNameIdFormat - Gets the NameID Format provided by the SAML response from the IdP.
• getNameIdNameQualifier - Gets the NameID NameQualifier provided from the SAML Response String.
• getNameIdNameSPQualifier - Gets the NameID SP NameQualifier provided from the SAML Response String.
• getSessionNotOnOrAfter - Gets the SessionNotOnOrAfter from the AuthnStatement
• getSessionIndex - Gets the SessionIndex from the AuthnStatement.
• getAttributes - Gets the Attributes from the AttributeStatement element.
• validateNumAssertions - Verifies that the document only contains a single Assertion (encrypted or not).
• validateTimestamps - Verifies that the document is still valid according Conditions Element.
• getErrorException - After executing a validation process, if it fails, this method returns the exception triggered.

Saml2\LogoutRequest - LogoutRequest.php

SAML 2 Logout Request class

• LogoutRequest - Constructs the Logout Request object.
• getRequest - Returns the Logout Request defated, base64encoded, unsigned
• getID - Returns the ID of the Logout Request. (If you have the object you can access to the id attribute)
• getNameIdData - Gets the NameID Data of the the Logout Request.
• getNameId - Gets the NameID of the Logout Request.
• getIssuer - Gets the Issuer of the Logout Request.
• getSessionIndexes - Gets the SessionIndexes from the Logout Request.
• isValid - Checks if the Logout Request received is valid.
• getErrorException - After executing a validation process, if it fails, this method returns the exception triggered.
• getXML - Returns the XML that will be sent as part of the request or that was received at the SP.

Saml2\LogoutResponse - LogoutResponse.php

SAML 2 Logout Response class

• LogoutResponse - Constructs a Logout Response object (Initialize params from settings and if provided load the Logout Response)
• getIssuer - Gets the Issuer of the Logout Response.
• getStatus - Gets the Status of the Logout Response.
• isValid - Determines if the SAML LogoutResponse is valid
• build - Generates a Logout Response object.
• getResponse - Returns a Logout Response object.
• getErrorException - After executing a validation process, if it fails, this method returns the exception triggered.

Saml2\Settings - Settings.php

Configuration of the SAML PHP Toolkit

• Settings - Initializes the settings: Sets the paths of the different folders and Loads settings info from settings file or array/object provided
• checkSettings - Checks the settings info.
• getExtLibPath - Returns external lib path.
• checkSPCerts - Checks if the x509 certs of the SP exists and are valid.
• getSPkey - Returns the x509 private key of the SP.
• getSPcert - Returns the x509 public cert of the SP.
• getSPcertNew - Returns the future x509 public cert of the SP.
• getIdPData - Gets the IdP data.
• getSPDataGets the SP data.
• getSecurityData - Gets security data.
• getContacts - Gets contact data.
• getOrganization - Gets organization data.
• getSPMetadata - Gets the SP metadata. The XML representation.
• validateMetadata - Validates an XML SP Metadata.
• getErrors - Returns an array with the errors, the array is empty when the settings is ok.
• getLastErrorException - Returns the exception related to the last error
• getBaseURL - Returns the baseurl set on the settings if any.
• setStrict - Activates or deactivates the strict mode.
• isStrict - Returns if the 'strict' mode is active.

Saml2\Metadata - Metadata.php

A class that contains functionality related to the metadata of the SP

• builder - Generates the metadata of the SP based on the settings.
• signmetadata - Signs the metadata with the key/cert provided
• addX509KeyDescriptors - Adds the x509 descriptors (sign/encriptation) to the metadata

Saml2\Utils - Utils.php

Auxiliary class that contains several methods

• validateXML - This function attempts to validate an XML string against the specified schema.
• formatCert - Returns a x509 cert (adding header & footer if required).
• formatPrivateKey - returns a RSA private key (adding header & footer if required).
• redirect - Executes a redirection to the provided url (or return the target url).
• isHTTPS - Checks if https or http.
• getSelfHost - Returns the current host.
• getSelfURLhost - Returns the protocol + the current host + the port (if different than common ports).
• getSelfURLNoQuery - Returns the URL of the current host + current view.
• getSelfURL - Returns the URL of the current host + current view + query.
• generateUniqueID - Generates a unique string (used for example as ID for assertions).
• parseTime2SAML - Converts a UNIX timestamp to SAML2 timestamp on the form yyyy-mm-ddThh:mm:ss(\.s+)?Z.
• parseSAML2Time - Converts a SAML2 timestamp on the form yyyy-mm-ddThh:mm:ss(\.s+)?Z to a UNIX timestamp. The sub-second part is ignored.
• parseDuration - Interprets a ISO8601 duration value relative to a given timestamp.
• getExpireTime - Compares two dates and returns the earliest.
• query - Extracts nodes from the DOMDocument.
• isSessionStarted - Checks if the session is started or not.
• deleteLocalSession - Deletes the local session.
• calculateX509Fingerprint - Calculates the fingerprint of a x509cert.
• formatFingerPrint - Formats a fingerprint.
• generateNameId - Generates a nameID.
• getStatus - Gets Status from a Response.
• decryptElement - Decrypts an encrypted element.
• castKey - Converts a XMLSecurityKey to the correct algorithm.
• addSign - Adds signature key and senders certificate to an element (Message or Assertion).
• validateSign - Validates a signature (Message or Assertion).

Saml2\IdPMetadataParser - IdPMetadataParser.php

Auxiliary class that contains several methods to retrieve and process IdP metadata

• parseRemoteXML - Get IdP Metadata Info from URL.
• parseFileXML - Get IdP Metadata Info from File.
• parseXML - Get IdP Metadata Info from XML.
• injectIntoSettings - Inject metadata info into php-saml settings array.

For more info, look at the source code; each method is documented and details about what it does and how to use it are provided. Make sure to also check the doc folder where HTML documentation about the classes and methods is provided for SAML and SAML2.

Demos included in the toolkit

The toolkit includes three demo apps to teach how use the toolkit, take a look on it.

Demos require that SP and IdP are well configured before test it.

Demo1

SP setup

The SAML PHP Toolkit allows you to provide the settings info in two ways:

• Use a settings.php file that we should locate at the base folder of the toolkit.
• Use an array with the setting data.

In this demo we provide the data in the second way, using a setting array named $settingsInfo. This array users the settings_example.php included as a template to create the settings.php settings and store it in the demo1/ folder. Configure the SP part and later review the metadata of the IdP and complete the IdP info.

If you check the code of the index.php file you will see that the settings.php file is loaded in order to get the $settingsInfo var to be used in order to initialize the Setting class.

Notice that in this demo, the setting.php file that could be defined at the base folder of the toolkit is ignored.

IdP setup

Once the SP is configured, the metadata of the SP is published at the metadata.php file. Configure the IdP based on that information.

How it works

1. First time you access to index.php view, you can select to login and return to the same view or login and be redirected to the attrs.php view.

2. When you click:

   2.1 in the first link, we access to (index.php?sso) an AuthNRequest is sent to the IdP, we authenticate at the IdP and then a Response is sent through the user's client to the SP, specifically the Assertion Consumer Service view: index.php?acs. Notice that a RelayState parameter is set to the url that initiated the process, the index.php view.

   2.2 in the second link we access to (attrs.php) have the same process described at 2.1 with the diference that as RelayState is set the attrs.php.

3. The SAML Response is processed in the ACS (index.php?acs), if the Response is not valid, the process stops here and a message is shown. Otherwise we are redirected to the RelayState view. a) index.php or b) attrs.php.

4. We are logged in the app and the user attributes are showed. At this point, we can test the single log out functionality.

5. The single log out functionality could be tested by two ways.

   5.1 SLO Initiated by SP. Click on the "logout" link at the SP, after that a Logout Request is sent to the IdP, the session at the IdP is closed and replies through the client to the SP with a Logout Response (sent to the Single Logout Service endpoint). The SLS endpoint (index.php?sls) of the SP process the Logout Response and if is valid, close the user session of the local app. Notice that the SLO Workflow starts and ends at the SP.

   5.2 SLO Initiated by IdP. In this case, the action takes place on the IdP side, the logout process is initiated at the idP, sends a Logout Request to the SP (SLS endpoint, index.php?sls). The SLS endpoint of the SP process the Logout Request and if is valid, close the session of the user at the local app and send a Logout Response to the IdP (to the SLS endpoint of the IdP). The IdP receives the Logout Response, process it and close the session at of the IdP. Notice that the SLO Workflow starts and ends at the IdP.

Notice that all the SAML Requests and Responses are handled by a unique file, the index.php file and how GET paramters are used to know the action that must be done.

Demo2

SP setup

The SAML PHP Toolkit allows you to provide the settings info in two ways:

• Use a settings.php file that we should locate at the base folder of the toolkit.
• Use an array with the setting data.

The first is the case of the demo2 app. The setting.php file and the setting_extended.php file should be defined at the base folder of the toolkit. Review the setting_example.php and the advanced_settings_example.php to learn how to build them.

In this case as Attribute Consume Service and Single Logout Service we are going to use the files located in the endpoint folder (acs.php and sls.php).

IdP setup

Once the SP is configured, the metadata of the SP is published at the metadata.php file. Based on that info, configure the IdP.

How it works

At demo1, we saw how all the SAML Request and Responses were handler at an unique file, the index.php file. This demo1 uses high-level programming.

At demo2, we have several views: index.php, sso.php, slo.php, consume.php and metadata.php. As we said, we will use the endpoints that are defined in the toolkit (acs.php, sls.php of the endpoints folder). This demo2 uses low-level programming.

Notice that the SSO action can be initiated at index.php or sso.php.

The SAML workflow that take place is similar that the workflow defined in the demo1, only changes the targets.

1. When you access index.php or sso.php for the first time, an AuthNRequest is sent to the IdP automatically, (as RelayState is sent the origin url). We authenticate at the IdP and then a Response is sent to the SP, to the ACS endpoint, in this case acs.php of the endpoints folder.

2. The SAML Response is processed in the ACS, if the Response is not valid, the process stops here and a message is shown. Otherwise we are redirected to the RelayState view (sso.php or index.php). The sso.php detects if the user is logged and redirects to index.php, so we will be in the index.php at the end.

3. We are logged into the app and the user attributes (if any) are shown. At this point, we can test the single log out functionality.

4. The single log out functionality could be tested by two ways.

   4.1 SLO Initiated by SP. Click on the "logout" link at the SP, after that we are redirected to the slo.php view and there a Logout Request is sent to the IdP, the session at the IdP is closed and replies to the SP a Logout Response (sent to the Single Logout Service endpoint). In this case The SLS endpoint of the SP process the Logout Response and if is valid, close the user session of the local app. Notice that the SLO Workflow starts and ends at the SP.

   4.2 SLO Initiated by IdP. In this case, the action takes place on the IdP side, the logout process is initiated at the idP, sends a Logout Request to the SP (SLS endpoint sls.php of the endpoint folder). The SLS endpoint of the SP process the Logout Request and if is valid, close the session of the user at the local app and sends a Logout Response to the IdP (to the SLS endpoint of the IdP).The IdP receives the Logout Response, process it and close the session at of the IdP. Notice that the SLO Workflow starts and ends at the IdP.