.NET 6 Scorching Reload and “Refused to connect with ws: as a result of it violates the Content material Safety Coverage directive” as a result of Internet Sockets



In the event you’re enthusiastic about Scorching Reload like me AND you additionally need an “A” grade from SecurityHeaders.com (actually, go do this now) then you’ll study in a short time about Content material-Safety-Coverage headers. You want to spend a while studying and you might find yourself with a considerably refined checklist of allowed issues, scripts, stylesheets, and many others.

In DasBlog Core (the cross platform weblog engine that runs this weblog) Mark Downie makes these configurable and makes use of the NWebSpec ASP.NET Middleware library so as to add the wanted headers.

if (SecurityStyleSources != null && SecurityScriptSources != null && DefaultSources != null)
{
app.UseCsp(choices => choices
.DefaultSources(s => s.Self()
.CustomSources(DefaultSources)
)
.StyleSources(s => s.Self()
.CustomSources(SecurityStyleSources)
.UnsafeInline()
)
.ScriptSources(s => s.Self()
.CustomSources(SecurityScriptSources)
.UnsafeInline()
.UnsafeEval()
)
);
}

Every of these variables comes out of a config file. Sure, it will be extra safety in the event that they got here out of a vault or had been even laborious coded.

DasBlog is a pretty big and funky app and we observed instantly upon Mark upgrading it to .NET 6 that we had been unable to make use of Scorching Reload (by way of dotnet watch or from VS 2022). We will complain about it, or we will study the way it works and why it isn’t working for us!

Keep in mind: Nothing in your laptop is hidden from you.

Beginning with a easy “View Supply” we will see a JavaScript embrace on the very backside that’s undoubtedly not mine!

<script src="http://feeds.hanselman.com/_framework/aspnetcore-browser-refresh.js"></script>

Okay, this is sensible as we all know not solely does HotReload help C# (code behinds) but in addition Markup by way of Razor Pages and altering CSS! It could undoubtedly want to speak “again dwelling” to the runner which is both “dotnet watch” or VS2022.

If I alter the ASPNETCORE_ENVIRONMENT to “Manufacturing” (both by way of launch.json, launchsettings, or an surroundings variable like this, I can see that additional HotReload helper script is not there:

C:githubwshotreloadtest>dotnet run --environment="Manufacturing"
Constructing...
information: Microsoft.Internet hosting.Lifetime[14]
Now listening on: https://localhost:7216
information: Microsoft.Internet hosting.Lifetime[14]
Now listening on: http://localhost:5216

Keep in mind: You by no means need to use dotnet run in manufacturing! It is an SDK constructing command! You may need to use dotnet exec your.dll, dotnet your.dll, or better of all, in .NET 6 simply name the EXE straight! .binDebugnet6.0wshotreloadtest.exe in my instance. Why? dotnet run will at all times assume it is in Improvement (you actually inform it to revive, construct, and exec in a single run command) if you happen to run it. You may notice that working the precise EXE is at all times WAY sooner as properly! Do not ship your .NET SDK to your webserver and do not recompile the entire thing on startup in manufacturing!

We will see that that aspnnetcore-browser-refresh.js is the consumer aspect of Improvement-time HotReload. our browser console we see :

Refused to Connect because it violates a CSP Directive

Refused to connect with 'wss://localhost:62486/' 
as a result of it violates the next Content material Safety Coverage
directive: "default-src 'self'".
Observe that 'connect-src' was not explicitly set,
so 'default-src' is used as a fallback.

That is quite a bit to consider. I began out my ASP.NET Internet App’s center ware saying it was OK to speak “again to myself” however nowhere else.

app.UseCsp(choices => choices.DefaultSources(s => s.Self())); 

Hm, self appears affordable, why cannot the browser join BACK to the dotnet run’ed Kestrel Internet Server? It is all localhost, proper? Effectively, particularly it is http://localhost not ws://localhost, and even wss://localhost (that additional s is for safe) so I have to explicitly permit ws: or wss: or each, however solely in Improvement.

Perhaps like this (once more, I am utilizing NWebSpec, however these are simply HTTP Headers so you may actually simply add them in order for you, hardcoded.)

app.UseCsp(choices => choices.DefaultSources(s => s.Self())
.ConnectSources(s => s.CustomSources("wss://localhost:62895")));

However port numbers change, proper? Let’s just do wss:, solely in Improvement. Now, if I am utilizing each CSPs and WebSockets (ws:, wss:) in Manufacturing, I am going to have to be intentional about this.

What is the ethical?

In the event you begin utilizing CSP Headers to tighten issues up, be acutely aware and conscious of the headers you want for conveniences like Scorching Reload in Improvement versus no matter issues you might want in Manufacturing.

Hope this helps prevent a while!


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About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, advisor, father, diabetic, and Microsoft worker. He’s a failed stand-up comedian, a cornrower, and a ebook creator.

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