stack_include does not appear to use Moodle proxy settings

[yositomi-opu]

Description

We are unable to use stack_include on our university's Moodle installation because access to external URLs times out.

Our Moodle server must use an HTTP proxy to access external websites. The proxy is configured in Moodle, and other Moodle functions can access external resources through it. However, the HTTP requests made by stack_include do not appear to fully respect Moodle's proxy settings.

This is not reported as an explicit Moodle or STACK error. Rather, the request to the external resource times out, and consequently stack_include cannot retrieve the requested content.

Environment

• Moodle version: 4.5.4+ (20250530)
• STACK version: 4.9.1 for Moodle 4.0+ (2025040100)
• PHP version: 8.2.30
• Operating system: RHEL 8.10

Relevant code

Our university's IT staff identified the following section of vle_specific.php as the likely source of the problem:

if ($good) {
    if (!isset($cache[$translated])) {
        // Feel free to apply any proxying here if you want.
        // Just remember that $islocalfile might be true and you might do
        // something else then.
        if ($islocalfile) {
            $cache[$translated] = file_get_contents($translated);
        } else {
            $translated = clean_param($translated, PARAM_URL);
            $headers = get_headers($translated);
            if (strpos($headers[0], '404') === false) {
                $cache[$translated] = download_file_content($translated);
            } else {
                $cache[$translated] = false;
            }
        }
    }
    return $cache[$translated];
}
$cache[$translated] = false;
return false;

In particular, the call

$headers = get_headers($translated);

appears to access the external URL directly, without using Moodle's configured HTTP proxy. In an environment where direct outbound HTTP access is not permitted, this request times out before the content can be retrieved.

The comment in this section also seems to indicate that proxy handling has not yet been implemented here:

// Feel free to apply any proxying here if you want.

Expected behaviour

All HTTP requests made by stack_include, including the request used to check the response headers, should respect Moodle's standard proxy configuration.

Actual behaviour

The request to the external URL times out because it appears to bypass the HTTP proxy configured in Moodle. As a result, stack_include cannot be used on our Moodle installation.

Request

Would it be possible to replace the direct HTTP access in this section with Moodle's standard HTTP client or another method that respects Moodle's proxy settings?

Please let us know if any additional configuration details or diagnostic information would be helpful.

[EJMFarrow]

Sorry about that, @yositomi-opu . Thanks for letting us know. I'm not sure that the get_headers() check is actually achieving anything as download_file_content returns false if the file is unavailable anyway. I'll investigate further.

[aharjula]

Well, that is an interesting situation... I do recall that there were people who just had to have that proxy feature some years ago, and that the file_get_contents was changed to download_file_content, for remote files, so that things would go through the Moodle proxy. But apparently none of the people wishing for that tested that capability. As you state, getting those headers without using the Moodle proxy is obviously going to block things, as that is a PHP-level function ignoring Moodle proxies.

The header check could be done inside that download_file_content call with the optional argument $fullresponse = true and then populating the cache based on the headers in the result. Naturally, someone could remove that comment, as that was there originally to mark the general region that needs to be worked on if one wanted proxy support, and we might soon have that support...

[EJMFarrow]

I've tried replicating this locally and it seems there may be an environment aspect as well. For me, blocking internet access except via proxy causes get_headers() to fail rather than timeout, returning false. Bizarrely strpos($headers[0], '404') === false is then true, causing download_file_content() to be called and everything to carry on fine(!).

Happily download_file_content() reliably returns false if there's a problem.