<?php
/*
 * Name: SAML SSO and SLO
 * Description: replace login and registration with a SAML identity provider.
 * Version: 0.0
 * Author: Ryan <https://friendica.verya.pe/profile/ryan>
 */
use Friendica\Content\Text\BBCode;
use Friendica\Core\Hook;
use Friendica\Core\Logger;
use Friendica\Core\Renderer;
use Friendica\Core\Session;
use Friendica\Database\DBA;
use Friendica\DI;
use Friendica\Model\User;
use Friendica\Util\Strings;
use OneLogin\Saml2\Auth;

require_once(__DIR__ . '/vendor/autoload.php');

define("PW_LEN", 32); // number of characters to use for random passwords

function saml_module($a) {}

function saml_init($a) {
    if ($a->argc < 2) return;

    switch ($a->argv[1]) {
        case "metadata.xml":
            saml_metadata();
            break;
        case "sso":
            saml_sso_reply($a);
            break;
        case "slo":
            saml_slo_reply();
            break;
	case "moo":
	    echo DI::baseUrl();
	    echo $_SERVER['REQUEST_URI'];
	    break;
    }
    exit();
}

function saml_metadata() {
    try {
        $settings = new \OneLogin\Saml2\Settings(saml_settings());
        $metadata = $settings->getSPMetadata();
        $errors = $settings->validateMetadata($metadata);

        if (empty($errors)) {
            header('Content-Type: text/xml');
            echo $metadata;
        } else {
            throw new \OneLogin\Saml2\Error(
                'Invalid SP metadata: '.implode(', ', $errors),
                \OneLogin\Saml2\Error::METADATA_SP_INVALID
            );
        }
    } catch (Exception $e) {
	Logger::error($e->getMessage());
    }
}

function saml_install() {
    Hook::register('login_hook', __FILE__, 'saml_sso_initiate');
    Hook::register('logging_out', __FILE__, 'saml_slo_initiate');
    Hook::register('head', __FILE__, 'saml_head');
    Hook::register('footer', __FILE__, 'saml_footer');
}

function saml_head(&$a, &$b) {
    DI::page()->registerStylesheet(__DIR__ . '/saml.css');
}

function saml_footer(&$a, &$b) {
    $fragment = addslashes(BBCode::convert(DI::config()->get('saml', 'settings_statement')));
    $b .= <<<EOL
<script>
var target=$("#settings-nickname-desc");
if (target.length) { target.append("<p>$fragment</p>"); }
</script>
EOL;
}

function saml_is_configured() {
    return
        DI::config()->get('saml', 'idp_id') &&
        DI::config()->get('saml', 'client_id') &&
        DI::config()->get('saml', 'sso_url') &&
        DI::config()->get('saml', 'slo_request_url') &&
        DI::config()->get('saml', 'slo_response_url') &&
        DI::config()->get('saml', 'sp_key') &&
        DI::config()->get('saml', 'sp_cert') &&
        DI::config()->get('saml', 'idp_cert');

}

function saml_sso_initiate(&$a, &$b) {
    if (!saml_is_configured()) return;

    $auth = new \OneLogin\Saml2\Auth(saml_settings());
    $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();
}

function saml_sso_reply($a) {
    $auth = new \OneLogin\Saml2\Auth(saml_settings());
    $requestID = null;

    if (isset($_SESSION) && isset($_SESSION['AuthNRequestID'])) {
        $requestID = $_SESSION['AuthNRequestID'];
    }

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

    $errors = $auth->getErrors();

    if (!empty($errors)) {
	echo "Errors encountered.";
        Logger::error(implode(', ', $errors));
        exit();
    }

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

    $username = $auth->getNameId();
    $email = $auth->getAttributeWithFriendlyName('email')[0];
    $name = $auth->getAttributeWithFriendlyName('givenName')[0];
    $last_name = $auth->getAttributeWithFriendlyName('surname')[0];

    if (strlen($last_name)) {
        $name .= " $last_name";
    }

    if (!DBA::exists('user', ['nickname' => $username])) {
        $user = saml_create_user($username, $email, $name);
    } else {
        $user = User::getByNickname($username);
    }

    if (!empty($user['uid'])) {
        DI::auth()->setForUser($a, $user);
    }

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

function saml_slo_initiate(&$a, &$b) {
    $auth = new \OneLogin\Saml2\Auth(saml_settings());

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

function saml_slo_reply() {
    $auth = new \OneLogin\Saml2\Auth(saml_settings());

    if (isset($_SESSION) && isset($_SESSION['LogoutRequestID'])) {
        $requestID = $_SESSION['LogoutRequestID'];
    } else {
        $requestID = null;
    }

    $auth->processSLO(false, $requestID);

    $errors = $auth->getErrors();

    if (empty($errors)) {
        $auth->redirectTo(DI::baseUrl());
    } else {
        Logger::error(implode(', ', $errors));
    }
}

function saml_input($key, $label, $description) {
    return [
        '$' . $key => [
            $key,
            DI::l10n()->t($label),
            DI::config()->get('saml', $key),
            DI::l10n()->t($description),
        true, // all the fields are required
        ]
    ];
}

function saml_addon_admin (&$a, &$o) {
    $form = 
        saml_input(
            'settings_statement',
            'Settings statement',
            'A statement on the settings page explaining where the user should go to change their e-mail and password. BBCode allowed.'
        ) +
        saml_input(
            'idp_id',
            'IdP ID',
            'Identity provider (IdP) entity URI (e.g., https://example.com/auth/realms/user).'
        ) +
        saml_input(
            'client_id',
            'Client ID',
            'Identifier assigned to client by the identity provider (IdP).'
        ) +
        saml_input(
            'sso_url',
            'IdP SSO URL',
            'The URL for your identity provider\'s SSO endpoint.'
        ) +
        saml_input(
            'slo_request_url',
            'IdP SLO request URL',
            'The URL for your identity provider\'s SLO request endpoint.'
        ) +
        saml_input(
            'slo_response_url',
            'IdP SLO response URL',
            'The URL for your identity provider\'s SLO response endpoint.'
        ) +
        saml_input(
            'sp_key',
            'SP private key',
            'The private key the addon should use to authenticate.'
        ) +
        saml_input(
            'sp_cert',
            'SP certificate',
            'The certficate for the addon\'s private key.'
        ) +
        saml_input(
            'idp_cert',
            'IdP certificate',
            'The x509 certficate for your identity provider.'
        ) +
        [
            '$submit'  => DI::l10n()->t('Save Settings'),
        ];
    $t = Renderer::getMarkupTemplate( "admin.tpl", "addon/saml/" );
    $o = Renderer::replaceMacros( $t, $form);
}

function saml_addon_admin_post (&$a) {
    $safeset = function ($key) {
        $val = (!empty($_POST[$key]) ? Strings::escapeTags(trim($_POST[$key])) : '');
        DI::config()->set('saml', $key, $val);
    };
    $safeset('idp_id');
    $safeset('client_id');
    $safeset('sso_url');
    $safeset('slo_request_url');
    $safeset('slo_response_url');
    $safeset('sp_key');
    $safeset('sp_cert');
    $safeset('idp_cert');

    // Not using safeset here since settings_statement is *meant* to include HTML tags.
    DI::config()->set('saml', 'settings_statement', $_POST['settings_statement']);
}

function saml_create_user($username, $email, $name) {
    if (!strlen($email) || !strlen($name)) {
        Logger::error('Could not create user: no email or username given.');
        return false;
    }

    try {
        $strong = false;
        $bytes = openssl_random_pseudo_bytes(intval(ceil(PW_LEN * 0.75)), $strong);

        if (!$strong) {
            throw new Exception('Strong algorithm not available for PRNG.');
        }

        $user = User::create([
            'username' => $name,
            'nickname' => $username,
            'email'    => $email,
            'password' => base64_encode($bytes), // should be at least PW_LEN long
	    'verified' => true
        ]);

	return $user;

    } catch (Exception $e) {
        Logger::error(
            'Exception while creating user',
            [
                'username'  => $username,
                'email'     => $email,
                'name'      => $name,
                'exception' => $e->getMessage(),
                'trace'     => $e->getTraceAsString()
            ]);

        return false;
    }
}

function saml_settings() {
    return 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.
        // Should never be set to anything else in production!
        'strict' => true,

        // Enable debug mode (to print errors).
        'debug' => 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' => DI::baseUrl() . "/saml",

        // Service Provider Data that we are deploying.
        'sp' => array(
            // Identifier of the SP entity  (must be a URI)
            'entityId' => DI::config()->get('saml','client_id'),
            // 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' => DI::baseUrl() . "/saml/sso",
                // SAML protocol binding to be used when returning the <Response>
                // message. OneLogin 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" => "Friendica SAML SSO and SLO Addon",
                "serviceDescription" => "SLO and SSO support for Friendica",
                "requestedAttributes" => array(
                    array(
                    "uid" => "",
                    "isRequired" => false,
                    )
                )
            ),
            // 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' => DI::baseUrl() . "/saml/slo",
                // SAML protocol binding to be used when returning the <Response>
                // message. OneLogin 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:unspecified',
            // 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' => DI::config()->get('saml','sp_cert'),
            'privateKey' => DI::config()->get('saml','sp_key'),
        ),

        // Identity Provider Data that we want connected with our SP.
        'idp' => array(
            // Identifier of the IdP entity  (must be a URI)
            'entityId' => DI::config()->get('saml','idp_id'),
            // 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' => DI::config()->get('saml','sso_url'),
                // SAML protocol binding to be used when returning the <Response>
                // message. OneLogin 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' => DI::config()->get('saml','slo_request_url'),
                // URL location of the IdP where SLO Response will be sent (ResponseLocation)
                // if not set, url for the SLO Request will be used
                'responseUrl' => DI::config()->get('saml','slo_response_url'),
                // SAML protocol binding to be used when returning the <Response>
                // message. OneLogin 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' => DI::config()->get('saml','idp_cert'),
       ),
       'security' => array (
	       'wantXMLValidation' => false,

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

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

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

       /* Sign the Metadata */
       'signMetadata' => true,
       )
    );
}
?>