.NET 6 Sizzling Reload and "Refused to hook up with ws: as a result of it violates the Content material Safety Coverage directive" as a result of Internet Sockets

If you happen to’re enthusiastic about Sizzling Reload like me AND you additionally need an “A” grade from SecurityHeaders.com (actually, go do that now) then you’ll study in a short time about Content material-Safety-Coverage headers. It’s worthwhile to spend a while studying and you might find yourself with a considerably refined checklist of allowed issues, scripts, stylesheets, and so forth.

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 might be extra safety in the event that they got here out of a vault or have been even exhausting coded.

DasBlog is a pretty big and funky app and we seen instantly upon Mark upgrading it to .NET 6 that we have been unable to make use of Sizzling 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 is not working for us!

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

Beginning with a easy “View Supply” we will see a JavaScript embody 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 assist C# (code behinds) but in addition Markup by way of Razor Pages and altering CSS! It might undoubtedly want to speak “again residence” to the runner which is both “dotnet watch” or VS2022.

If I modify 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

Bear in mind: You by no means need to use dotnet run in manufacturing! It is an SDK constructing command! You will need to use dotnet exec your.dll, dotnet your.dll, or better of all, in .NET 6 simply name the EXE instantly! .binDebugnet6.0wshotreloadtest.exe in my instance. Why? dotnet run will all the time assume it is in Improvement (you actually inform it to revive, construct, and exec in a single run command) in case you run it. You will observe that working the precise EXE is all the time WAY quicker as nicely! 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 shopper aspect of Improvement-time HotReload. Taking a look at our browser console we see :

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

That is so much 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? Properly, particularly it is http://localhost not ws://localhost, and even wss://localhost (that additional s is for safe) so I have to explicitly enable 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’ll be able to 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 must be intentional about this.

What is the ethical?

If you happen to begin utilizing CSP Headers to tighten issues up, be acutely aware and conscious of the headers you want for conveniences like Sizzling 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, marketing consultant, father, diabetic, and Microsoft worker. He’s a failed stand-up comedian, a cornrower, and a e book creator.