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.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



If you happen to’re enthusiastic about Scorching Reload like me AND you additionally need an “A” grade from SecurityHeaders.com (actually, go do that now) then you’ll be taught in a short time about Content material-Safety-Coverage headers. It’s essential to spend a while studying and chances are you’ll find yourself with a considerably subtle listing 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 seen instantly upon Mark upgrading it to .NET 6 that we had been unable to make use of Scorching Reload (through dotnet watch or from VS 2022). We are able to complain about it, or we are able to find out about the way it works and why it is not working for us!

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

Beginning with a easy “View Supply” we are able to see a JavaScript embrace on the very backside that’s positively 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 through Razor Pages and altering CSS! It will positively want to speak “again residence” to the runner which is both “dotnet watch” or VS2022.

If I alter the ASPNETCORE_ENVIRONMENT to “Manufacturing” (both through launch.json, launchsettings, or an setting variable like this, I can see that further HotReload helper script is not there:

C:githubwshotreloadtest>dotnet run --environment="Manufacturing"
Constructing...
data: Microsoft.Internet hosting.Lifetime[14]
Now listening on: https://localhost:7216
data: 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) if you happen to run it. You will notice 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 are able to see that that aspnnetcore-browser-refresh.js is the shopper 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'".
Be aware that 'connect-src' was not explicitly set,
so 'default-src' is used as a fallback.

That is loads 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 further 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 possibly can actually simply add them if you need, 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 aware and conscious of the headers you want for conveniences like Scorching Reload in Improvement versus no matter issues chances are you’ll 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 e book creator.

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