SAML2 metadata page does not load if IDP metadata page is unavailable

[pillbox1234567]

Describe the bug
SAML2 metadata page does not load if IdP metadata page is unavailable and SAML2_AUTOLOAD_METADATA=true. This is an issue if the IdP is configured to load metadata from BookStack because it creates a dependency loop.

Steps To Reproduce
Steps to reproduce the behavior:

1. Configure SAML2 authentication where the SAML2_IDP_ENTITYID points to a URL which returns a 504 error and set SAML2_AUTOLOAD_METADATA=true
2. Attempt to load the (bookstack_url/saml2/metadata) page
3. See error

Expected behavior
The metadata URL (bookstack_url/saml2/metadata) should load correctly regardless of whether the IdP metadata URL is available

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): v0.31.3
• PHP Version: 7.4
• Hosting Method (Nginx/Apache/Docker): nginx
• IdP: ClassLink

Additional context
Stack trace from laravel.log

[2021-01-12 15:28:06] production.ERROR: Error on parseRemoteXML. The requested URL returned error: 504  {"exception":"[object] (Exception(code: 0): Error on parseRemoteXML. The requested URL returned error: 504  at /var/www/apps/BookStack/vendor/onelogin/php-saml/src/Saml2/IdPMetadataParser.php:59)
[stacktrace]
#0 /var/www/apps/BookStack/app/Auth/Access/Saml2Service.php(174): OneLogin\\Saml2\\IdPMetadataParser::parseRemoteXML('https://idp.cla...')
#1 /var/www/apps/BookStack/app/Auth/Access/Saml2Service.php(143): BookStack\\Auth\\Access\\Saml2Service->getToolkit()
#2 /var/www/apps/BookStack/app/Http/Controllers/Auth/Saml2Controller.php(52): BookStack\\Auth\\Access\\Saml2Service->metadata()
#3 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Controller.php(54): BookStack\\Http\\Controllers\\Auth\\Saml2Controller->metadata()
#4 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/ControllerDispatcher.php(45): Illuminate\\Routing\\Controller->callAction('metadata', Array)
#5 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Route.php(219): Illuminate\\Routing\\ControllerDispatcher->dispatch(Object(Illuminate\\Routing\\Route), Object(BookStack\\Http\\Controllers\\Auth\\Saml2Controller), 'metadata')
#6 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Route.php(176): Illuminate\\Routing\\Route->runController()
#7 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Router.php(681): Illuminate\\Routing\\Route->run()
#8 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(130): Illuminate\\Routing\\Router->Illuminate\\Routing\\{closure}(Object(BookStack\\Http\\Request))
#9 /var/www/apps/BookStack/app/Http/Middleware/CheckGuard.php(25): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#10 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): BookStack\\Http\\Middleware\\CheckGuard->handle(Object(BookStack\\Http\\Request), Object(Closure), 'saml2')
#11 /var/www/apps/BookStack/app/Http/Middleware/GlobalViewData.php(25): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#12 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): BookStack\\Http\\Middleware\\GlobalViewData->handle(Object(BookStack\\Http\\Request), Object(Closure))
#13 /var/www/apps/BookStack/app/Http/Middleware/Localization.php(76): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#14 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): BookStack\\Http\\Middleware\\Localization->handle(Object(BookStack\\Http\\Request), Object(Closure))
#15 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/VerifyCsrfToken.php(77): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#16 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\VerifyCsrfToken->handle(Object(BookStack\\Http\\Request), Object(Closure))
#17 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/View/Middleware/ShareErrorsFromSession.php(49): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#18 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\View\\Middleware\\ShareErrorsFromSession->handle(Object(BookStack\\Http\\Request), Object(Closure))
#19 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Session/Middleware/StartSession.php(56): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#20 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Session\\Middleware\\StartSession->handle(Object(BookStack\\Http\\Request), Object(Closure))
#21 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/AddQueuedCookiesToResponse.php(37): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#22 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Cookie\\Middleware\\AddQueuedCookiesToResponse->handle(Object(BookStack\\Http\\Request), Object(Closure))
#23 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Cookie/Middleware/EncryptCookies.php(67): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#24 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Cookie\\Middleware\\EncryptCookies->handle(Object(BookStack\\Http\\Request), Object(Closure))
#25 /var/www/apps/BookStack/app/Http/Middleware/ControlIframeSecurity.php(31): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#26 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): BookStack\\Http\\Middleware\\ControlIframeSecurity->handle(Object(BookStack\\Http\\Request), Object(Closure))
#27 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(105): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#28 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Router.php(683): Illuminate\\Pipeline\\Pipeline->then(Object(Closure))
#29 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Router.php(658): Illuminate\\Routing\\Router->runRouteWithinStack(Object(Illuminate\\Routing\\Route), Object(BookStack\\Http\\Request))
#30 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Router.php(624): Illuminate\\Routing\\Router->runRoute(Object(BookStack\\Http\\Request), Object(Illuminate\\Routing\\Route))
#31 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Routing/Router.php(613): Illuminate\\Routing\\Router->dispatchToRoute(Object(BookStack\\Http\\Request))
#32 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(170): Illuminate\\Routing\\Router->dispatch(Object(BookStack\\Http\\Request))
#33 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(130): Illuminate\\Foundation\\Http\\Kernel->Illuminate\\Foundation\\Http\\{closure}(Object(BookStack\\Http\\Request))
#34 /var/www/apps/BookStack/vendor/fideloper/proxy/src/TrustProxies.php(57): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#35 /var/www/apps/BookStack/app/Http/Middleware/TrustProxies.php(39): Fideloper\\Proxy\\TrustProxies->handle(Object(BookStack\\Http\\Request), Object(Closure))
#36 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): BookStack\\Http\\Middleware\\TrustProxies->handle(Object(BookStack\\Http\\Request), Object(Closure))
#37 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/TransformsRequest.php(21): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#38 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\TransformsRequest->handle(Object(BookStack\\Http\\Request), Object(Closure))
#39 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/ValidatePostSize.php(27): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#40 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\ValidatePostSize->handle(Object(BookStack\\Http\\Request), Object(Closure))
#41 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Middleware/CheckForMaintenanceMode.php(63): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#42 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(171): Illuminate\\Foundation\\Http\\Middleware\\CheckForMaintenanceMode->handle(Object(BookStack\\Http\\Request), Object(Closure))
#43 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Pipeline/Pipeline.php(105): Illuminate\\Pipeline\\Pipeline->Illuminate\\Pipeline\\{closure}(Object(BookStack\\Http\\Request))
#44 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(145): Illuminate\\Pipeline\\Pipeline->then(Object(Closure))
#45 /var/www/apps/BookStack/vendor/laravel/framework/src/Illuminate/Foundation/Http/Kernel.php(110): Illuminate\\Foundation\\Http\\Kernel->sendRequestThroughRouter(Object(BookStack\\Http\\Request))
#46 /var/www/apps/BookStack/public/index.php(56): Illuminate\\Foundation\\Http\\Kernel->handle(Object(BookStack\\Http\\Request))
#47 {main}
"} 

[ssddanbrown]

Thanks for raising @pillbox1234567 and sorry for the delayed response.

Has now been addressed within f0ac454, Will be part of the next feature release.