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Pull Request — master (#18)
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01:55
created

SAMLController::transformGuid()   A

Complexity

Conditions 1
Paths 1

Size

Total Lines 3
Code Lines 1

Duplication

Lines 0
Ratio 0 %

Importance

Changes 0
Metric Value
cc 1
eloc 1
nc 1
nop 1
dl 0
loc 3
rs 10
c 0
b 0
f 0
1
<?php
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namespace SilverStripe\SAML\Control;
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use Exception;
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use function gmmktime;
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use OneLogin\Saml2\Auth;
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use OneLogin\Saml2\Constants;
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use OneLogin\Saml2\Utils;
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use OneLogin\Saml2\Error;
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use Psr\Log\LoggerInterface;
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use SilverStripe\Core\Config\Config;
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use SilverStripe\ORM\ValidationResult;
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use SilverStripe\SAML\Authenticators\SAMLAuthenticator;
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use SilverStripe\SAML\Authenticators\SAMLLoginForm;
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use SilverStripe\SAML\Helpers\SAMLHelper;
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use SilverStripe\Control\Controller;
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use SilverStripe\Control\Director;
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use SilverStripe\Control\HTTPResponse;
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use SilverStripe\Core\Injector\Injector;
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use SilverStripe\SAML\Model\SAMLResponse;
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use SilverStripe\SAML\Services\SAMLConfiguration;
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use SilverStripe\Security\IdentityStore;
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use SilverStripe\Security\Member;
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use SilverStripe\Security\Security;
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use function uniqid;
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/**
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 * Class SAMLController
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 *
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 * This controller handles serving metadata requests for the identity provider (IdP), as well as handling the creation
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 * of new users and logging them into SilverStripe after being authenticated at the IdP.
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 */
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class SAMLController extends Controller
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{
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    /**
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     * @var array
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     */
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    private static $allowed_actions = [
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        'index',
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        'acs',
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        'metadata'
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    ];
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    public function index()
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    {
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        return $this->redirect('/');
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    }
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    /**
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     * Assertion Consumer Service
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     *
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     * The user gets sent back here after authenticating with the IdP, off-site.
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     * The earlier redirection to the IdP can be found in the SAMLAuthenticator::authenticate.
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     *
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     * After this handler completes, we end up with a rudimentary Member record (which will be created on-the-fly
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     * if not existent), with the user already logged in. Login triggers memberLoggedIn hooks, which allows
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     * LDAP side of this module to finish off loading Member data.
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     *
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     * @throws Error
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     * @throws \Psr\Container\NotFoundExceptionInterface
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     */
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    public function acs()
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    {
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        /** @var Auth $auth */
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        $auth = Injector::inst()->get(SAMLHelper::class)->getSAMLAuth();
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        $caughtException = null;
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        // Log both errors (reported by php-saml and thrown as exception) with a common ID for later tracking
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        $uniqueErrorId = uniqid('SAML-');
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        // Force php-saml module to use the current absolute base URL (e.g. https://www.example.com/saml). This avoids
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        // errors that we otherwise get when having a multi-directory ACS URL like /saml/acs).
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        // See https://github.com/onelogin/php-saml/issues/249
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        Utils::setBaseURL(Controller::join_links($auth->getSettings()->getSPData()['entityId'], 'saml'));
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        // Attempt to process the SAML response. If there are errors during this, log them and redirect to the generic
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        // error page. Note: This does not necessarily include all SAML errors (e.g. we still need to confirm if the
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        // user is authenticated after this block
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        try {
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            $auth->processResponse();
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            $error = $auth->getLastErrorReason();
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        } catch (Exception $e) {
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            $caughtException = $e;
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        }
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        // If there was an issue with the SAML response, if it was missing or if the SAML response indicates that they
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        // aren't authorised, then log the issue and provide a traceable error back to the user via the login form
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        $hasError = $caughtException || !empty($error);
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        if ($hasError || !$auth->isAuthenticated() || $this->checkForReplayAttack($auth, $uniqueErrorId)) {
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            if ($caughtException instanceof Exception) {
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                $this->getLogger()->error(sprintf(
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                    '[%s] [code: %s] %s (%s:%s)',
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                    $uniqueErrorId,
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                    $e->getCode(),
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                    $e->getMessage(),
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                    $e->getFile(),
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                    $e->getLine()
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                ));
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            }
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            if (!empty($error)) {
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                $this->getLogger()->error(sprintf('[%s] %s', $uniqueErrorId, $error));
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            }
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            $this->getForm()->sessionMessage(
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                _t(
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                    'SilverStripe\\SAML\\Control\\SAMLController.ERR_SAML_ACS_FAILURE',
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                    'Unfortunately we couldn\'t log you in. If this continues, please contact your I.T. department'
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                    . ' with the following reference: {ref}',
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                    ['ref' => $uniqueErrorId]
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                ),
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                ValidationResult::TYPE_ERROR
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            );
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            // Redirect the user back to the login form to display the generic error message and reference
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            $this->getRequest()->getSession()->save($this->getRequest());
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            return $this->redirect('Security/login');
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        }
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        /**
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         * If processing reaches here, then the user is authenticated - the rest of this method is just processing their
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         * legitimate information and configuring their account.
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         */
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        // If we expect the NameID to be a binary version of the GUID (ADFS), check that it actually is
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        // If we are configured not to expect a binary NameID, then we assume it is a direct GUID (Azure AD)
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        if (Config::inst()->get(SAMLConfiguration::class, 'expect_binary_nameid')) {
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            $decodedNameId = base64_decode($auth->getNameId());
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            if (ctype_print($decodedNameId)) {
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                $this->getForm()->sessionMessage('NameID from IdP is not a binary GUID.', ValidationResult::TYPE_ERROR);
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                $this->getRequest()->getSession()->save($this->getRequest());
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                return $this->getRedirect();
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            }
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            // transform the NameId to guid
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            $helper = SAMLHelper::singleton();
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            $guid = $helper->binToStrGuid($decodedNameId);
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            if (!$helper->validGuid($guid)) {
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                $errorMessage = "Not a valid GUID '{$guid}' received from server.";
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                $this->getLogger()->error($errorMessage);
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                $this->getForm()->sessionMessage($errorMessage, ValidationResult::TYPE_ERROR);
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                $this->getRequest()->getSession()->save($this->getRequest());
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                return $this->getRedirect();
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            }
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        } else {
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            $guid = $auth->getNameId();
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        }
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        $guid = $this->transformGuid($guid);
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        $attributes = $auth->getAttributes();
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        $fieldToClaimMap = array_flip(Member::config()->claims_field_mappings);
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        // Write a rudimentary member with basic fields on every login, so that we at least have something
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        // if there is no further sync (e.g. via LDAP)
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        $member = Member::get()->filter('GUID', $guid)->limit(1)->first();
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        if (!($member && $member->exists()) && Config::inst()->get(SAMLConfiguration::class, 'allow_insecure_email_linking') && isset($fieldToClaimMap['Email'])) {
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            // If there is no member found via GUID and we allow linking via email, search by email
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            $member = Member::get()->filter('Email', $attributes[$fieldToClaimMap['Email']])->limit(1)->first();
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            if (!($member && $member->exists())) {
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                $member = new Member();
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            }
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            $member->GUID = $guid;
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        } elseif (!($member && $member->exists())) {
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            // If the member doesn't exist and we don't allow linking via email, then create a new member
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            $member = new Member();
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            $member->GUID = $guid;
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        }
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        foreach ($member->config()->claims_field_mappings as $claim => $field) {
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            if (!isset($attributes[$claim][0])) {
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                $this->getLogger()->warning(
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                    sprintf(
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                        'Claim rule \'%s\' configured in SAMLMemberExtension.claims_field_mappings, ' .
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                                'but wasn\'t passed through. Please check IdP claim rules.',
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                        $claim
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                    )
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                );
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                continue;
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            }
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            $member->$field = $attributes[$claim][0];
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        }
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        $member->SAMLSessionIndex = $auth->getSessionIndex();
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        // This will trigger LDAP update through LDAPMemberExtension::memberLoggedIn, if the LDAP module is installed.
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        // The LDAP update will also write the Member record a second time, but the member *must* be written before
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        // IdentityStore->logIn() is called, otherwise the identity store throws an exception.
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        // Both SAML and LDAP identify Members by the same GUID field.
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        $member->write();
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        /** @var IdentityStore $identityStore */
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        $identityStore = Injector::inst()->get(IdentityStore::class);
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        $identityStore->logIn($member, false, $this->getRequest());
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        return $this->getRedirect();
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    }
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    /**
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     * Generate this SP's metadata. This is needed for intialising the SP-IdP relationship.
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     * IdP is instructed to call us back here to establish the relationship. IdP may also be configured
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     * to hit this endpoint periodically during normal operation, to check the SP availability.
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     */
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    public function metadata()
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    {
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        try {
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            /** @var Auth $auth */
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            $auth = Injector::inst()->get(SAMLHelper::class)->getSAMLAuth();
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            $settings = $auth->getSettings();
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            $metadata = $settings->getSPMetadata();
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            $errors = $settings->validateMetadata($metadata);
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            if (empty($errors)) {
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                header('Content-Type: text/xml');
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                echo $metadata;
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            } else {
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                throw new Error(
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                    'Invalid SP metadata: ' . implode(', ', $errors),
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                    Error::METADATA_SP_INVALID
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                );
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            }
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        } catch (Exception $e) {
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            $this->getLogger()->error($e->getMessage());
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            echo $e->getMessage();
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        }
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    }
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    /**
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     * @return HTTPResponse
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     */
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    protected function getRedirect()
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    {
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        // Absolute redirection URLs may cause spoofing
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        if ($this->getRequest()->getSession()->get('BackURL')
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            && Director::is_site_url($this->getRequest()->getSession()->get('BackURL'))) {
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            return $this->redirect($this->getRequest()->getSession()->get('BackURL'));
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        }
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        // Spoofing attack, redirect to homepage instead of spoofing url
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        if ($this->getRequest()->getSession()->get('BackURL')
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            && !Director::is_site_url($this->getRequest()->getSession()->get('BackURL'))) {
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            return $this->redirect(Director::absoluteBaseURL());
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        }
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        // If a default login dest has been set, redirect to that.
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        if (Security::config()->default_login_dest) {
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            return $this->redirect(Director::absoluteBaseURL() . Security::config()->default_login_dest);
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        }
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        // fallback to redirect back to home page
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        return $this->redirect(Director::absoluteBaseURL());
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    }
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    /**
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     * If processing reaches here, then the user is authenticated but potentially not valid. We first need to confirm
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     * that they are not an attacker performing a SAML replay attack (capturing the raw traffic from a compromised
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     * device and then re-submitting the same SAML response).
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     *
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     * To combat this, we store SAML response IDs for the amount of time they're valid for (plus a configurable offset
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     * to account for potential time skew), and if the ID has been seen before we log an error message and return true
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     * (which indicates that this specific request is a replay attack).
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     *
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     * If no replay attack is detected, then the SAML response is logged so that future requests can be blocked.
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     *
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     * @param Auth $auth The Auth object that includes the processed response
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     * @param string $uniqueErrorId The error code to use when logging error messages for this given error
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     * @return bool true if this response is a replay attack, false if it's the first time we've seen the ID
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     */
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    protected function checkForReplayAttack(Auth $auth, $uniqueErrorId = '')
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    {
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        $responseId = $auth->getLastMessageId();
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        $expiry = $auth->getLastAssertionNotOnOrAfter(); // Note: Expiry will always be stored and returned in UTC
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        // Search for any SAMLResponse objects where the response ID is the same and the expiry is within the range
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        $count = SAMLResponse::get()->filter(['ResponseID' => $responseId])->count();
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        if ($count > 0) {
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            // Response found, therefore this is a replay attack - log the error and return false so the user is denied
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            $this->getLogger()->error(sprintf(
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                '[%s] SAML replay attack detected! Response ID "%s", expires "%s", client IP "%s"',
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                $uniqueErrorId,
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                $responseId,
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                $expiry,
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                $this->getRequest()->getIP()
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            ));
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            return true;
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        } else {
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            // No attack detected, log the SAML response
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            $response = new SAMLResponse([
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                'ResponseID' => $responseId,
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                'Expiry' => $expiry
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            ]);
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            $response->write();
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            return false;
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        }
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    }
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    /**
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     * Get a logger
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     *
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     * @return LoggerInterface
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     */
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    public function getLogger()
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    {
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        return Injector::inst()->get(LoggerInterface::class);
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    }
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    /**
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     * Gets the login form
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     *
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     * @return SAMLLoginForm
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     */
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    public function getForm()
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    {
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        return Injector::inst()->get(SAMLLoginForm::class, true, [$this, SAMLAuthenticator::class, 'LoginForm']);
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    }
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    /**
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     * Transform or normalize received GUID
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     *
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     * @param string|mixed $guid
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     * @return mixed
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     */
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    protected function transformGuid($guid)
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    {
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        return $guid;
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    }
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}
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