Moodle in English: Hosting - Azure App Service

Hosting - Azure App Service

by Mark Barnett - Sunday, January 24, 2021, 1:43 AM

Hey,

I have recently been trying to deploy Moodle to an Azure App service. The deployment is successful but unfortunately when I hit the app service domain the attached error appears. The domain in the attached image is exactly the same as what I have defined in the config.php.

I believe that this issue is occurring because Azure app services for Linux utilise containers to host deployed applications. This might be confusing the application as connections are being proxied.

Has anyone managed to successfully deploy moodle to an Azure App Service for Linux?

Thanks in advance

Re: Hosting - Azure App Service

by Howard Miller - Sunday, January 24, 2021, 2:07 AM

I don't know anything about Azure but your problem is thet the $CFG->www setting in config.php differs from the URL that you are attempting to access Moodle with. They *have* to be the same - regardless of forwarding, rewrites etc. etc.

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Re: Hosting - Azure App Service

by Leon Stringer - Sunday, January 24, 2021, 2:08 AM

Try adding $CFG->reverseproxy = true to config.php. There's a bit of information about this setting in the sample config-dist.php:

// Enable when setting up advanced reverse proxy load balancing configurations,
// it may be also necessary to enable this when using port forwarding.
$CFG->reverseproxy = true;

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Re: Hosting - Azure App Service

by Howard Miller - Sunday, January 24, 2021, 2:10 AM

What does that actually *do*?

I've never been in the position of having to use it?

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Re: Hosting - Azure App Service

by Leon Stringer - Sunday, January 24, 2021, 3:43 AM

Moodle insists it is accessed using $CFG->wwwroot. It enforces this by checking the request by inspecting $_SERVER[]. In a standard configuration the browser connects directly to the web server (assuming $CFG->wwwroot is "https://moodle.example.com"):

Browser's request to web server	$_SERVER['HTTP_HOST'] that Moodle sees
GET https://moodle.example.com/	"moodle.example.com"

They match so Moodle is happy. But if the web server is behind a reverse proxy (e.g. load balancer):

Browser's request to reverse proxy	Reverse proxy's request to web server	$_SERVER['HTTP_HOST'] that Moodle sees
GET https://moodle.example.com/	GET https://webnode1.internal.test/	"webnode1.internal.test"

and you get "Incorrect access detected…" because $CFG->wwwroot and the $_SERVER[] values don't match.

Enabling $CFG->reverseproxy turns off this check. With this enabled you now cannot access the web server directly using $CFG->wwwroot, only via the reverse proxy. Direct access results in "Reverse proxy enabled, server can not be accessed directly".

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Re: Hosting - Azure App Service

by Howard Miller - Sunday, January 24, 2021, 4:27 PM

Ahh..... ok. I've used load balancers for years but this has never come up. They've always passed through the request URL.

As you note, as long as it's not being used to cover up a misconfiguration of some sort.

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Hosting - Azure App Service