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.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 Net Sockets



Should you’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 be taught in a short time about Content material-Safety-Coverage headers. It is advisable to spend a while studying and you could find yourself with a considerably subtle checklist of allowed issues, scripts, stylesheets, and so on.

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 had been even exhausting coded.

DasBlog is a fairly large and funky app and we seen instantly upon Mark upgrading it to .NET 6 that we had been unable to make use of Sizzling Reload (through dotnet watch or from VS 2022). We will complain about it, or we are able to find out about the way it works and why it is not working for us!

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

Beginning with a easy “View Supply” we are able to 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 help C# (code behinds) but additionally Markup through Razor Pages and altering CSS! It will 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 through launch.json, launchsettings, or an atmosphere 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

Keep in mind: You by no means wish to use dotnet run in manufacturing! It is an SDK constructing command! You will wish 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 Growth (you actually inform it to revive, construct, and exec in a single run command) in the event you run it. You will be aware that working the precise EXE is all the time WAY sooner as effectively! 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 facet of Growth-time HotReload. our browser console we see :

Refused to Connect because it violates a CSP Directive

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 rather a lot to consider. I began out my ASP.NET Net 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 Net 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 must explicitly permit ws: or wss: or each, however solely in Growth.

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 if you’d like, hardcoded.)

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

However port numbers change, proper? Let’s do exactly wss:, solely in Growth. Now, if I am utilizing each CSPs and WebSockets (ws:, wss:) in Manufacturing, I will should be intentional about this.

What is the ethical?

Should you begin utilizing CSP Headers to tighten issues up, be acutely aware and conscious of the headers you want for conveniences like Sizzling Reload in Growth versus no matter issues you could 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.

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