VPN causes editor to crash and documentation website to fail

Hi folks,

A little while ago I reported a bug, which as the title says; causes the editor itself (2020 LTS) to crash at the splash screen - making it impossible to launch.

This only occurs while connected to some VPN servers. And, while this issue is occurring, the website docs.unity.com fails to load too (in any browser), only responding with a 403 “Forbidden” response code. Other websites, that aren’t hosted on Unity servers, load just fine.

Looking at the Unity Launcher logfiles, the final log before the crash shows a failed API call to a subdomain of internal.unity3d.com. It dumps out the entire HTML string of a 403 response, straight into the logfile, which likely means the response isn’t being handled correctly at all, and is resulting in an uncaught exception.

Switching VPN server has proven to resolve these issues. docs.unity.com will load AND the editor will open, after basically just changing your IP address.

It’s likely that these Unity web and API servers are running some form of denial-of-service attack protection (such as Apache’s “mod_evasive”), that is temporarily blacklisting IP addresses from which it receives an unusual amount of traffic. This could explain the 403 responses, to both the API calls and the docs website requests, and explains why the issue resolves itself when just hopping VPN server. This is clearly affecting legitimate users too, who use popular VPNs.

I had a conversation with support about this, and I sent a great deal of this information to help diagnose the precise cause of the crashes. I asked that they raise this as a bug - at the very least to add an exception handler in the editor code, to catch failed API requests and alert the user, instead of just flat out crashing.

VPN use should not stop the Unity Editor from opening.

I was told this “wasn’t a Unity problem” and the bug report (and all the time lost to it) basically came to nothing.

Today, after having to literally hop VPN server about six times just to get the Unity Editor to open, I’ve decided it might be worthwhile to share the details of this issue with the wider community - in case others run into it too.

If the editor is crashing for you, when you try to open it, your IP address might be blacklisted by Unity’s API servers. If you are using a VPN and have the luxury of being able to safely disable it, try that. Otherwise, just change server and try again.

It’s very unfortunate that Unity has chosen to see this as “not a Unity problem” when the Unity Editor itself is crashing on launch - and likely due to something as simple as a missing exception handler, for an invalid API response, from their own API server! Especially when the VPN here is actually doing it’s job just fine, faithfully relaying the 403 response, that the Unity API server has chosen to send. But, well, here we are.

Oh, and all of this is overlooking the fact that I haven’t been able to successfully complete a transaction on the unity store, over any VPN server, for years now. At least the editor isn’t crashing that “reliably”, thankfully.

Anyway, sorry for the poor tone / rant here. It’s been a frustrating experience for sure.

I hope this info is useful / helpful someone else out there anyway.

That’s all.

@Josun FYI, we don’t “blacklist” your IP. It’s actually the other way around, your VPN is blocking our addresses. You will need to configure your VPN to allow .unity.com: and unity3d.com:*

The requests being sent your web server are not hanging or timing out.

There’s a valid response to these requests.

One from the logfile states “Your client does not have permission to get URL X from this server.” and it provides a relative URL (a directory path), not an absolute URL. This is most likely your server responding.

To the best of my knowledge, this behaviour is consistent with web-server based auto-blacklisting modules, designed for denial-of-service attack protection.

It’s also logical that these modules might activate against VPN users, if too many people are connecting to you through one server.

I also find it really difficult to believe that a commercial VPN provider would be specifically blocking only your domains, considering all other domains appear to work fine. I.e. google.com loads, docs.unity.com doesn’t. Though I will pose the question to my VPN provider, the next time I find myself on a problematic server.

But, regardless of all this, the Unity Editor is crashing on start up, without any prompt or warning.

It shouldn’t be crashing at all.

That’s a bug.

Agreed! A Charles Proxy capture may help us pinpoint what is going on. If your VPN is changing IP addresses between requests, it may indeed appear to be a DOS. https://support.unity.com/hc/en-us/articles/115002917683-Using-Charles-Proxy-with-Unity