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.NET 6 Scorching 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



For those who’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. You might want to spend a while studying and you could 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 will be extra safety in the event that they got here out of a vault or had been even onerous 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 (by way of dotnet watch or from VS 2022). We are able to complain about it, or we are able to 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 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 by way of Razor Pages and altering CSS! It will positively want to speak “again dwelling” 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 atmosphere variable like this, I can see that additional 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) should you run it. You will word that operating 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 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'".
Be aware that 'connect-src' was not explicitly set,
so 'default-src' is used as a fallback.

That is lots 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 cheap, why cannot the browser join BACK to the dotnet run’ed Kestrel Internet Server? It is all localhost, proper? Nicely, 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 Growth.

Possibly like this (once more, I am utilizing NWebSpec, however these are simply HTTP Headers so you possibly can 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 do exactly wss:, solely in Growth. Now, if I am utilizing each CSPs and WebSockets (ws:, wss:) in Manufacturing, I will must be intentional about this.

What is the ethical?

For those who begin utilizing CSP Headers to tighten issues up, be aware and conscious of the headers you want for conveniences like Scorching 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 writer.

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