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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 this now) then you’ll be taught in a short time about Content material-Safety-Coverage headers. You 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 could be extra safety in the event that they got here out of a vault or had been even onerous coded.

DasBlog is a fairly large 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 (through dotnet watch or from VS 2022). We are able to complain about it, or we will study 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 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 smart as we all know not solely does HotReload help C# (code behinds) but in addition Markup through Razor Pages and altering CSS! It will undoubtedly want to speak “again house” 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 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 immediately! .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) if you happen to run it. You may word that working the precise EXE is all the time WAY quicker as effectively! 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 consumer 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'".
Notice 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 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? Effectively, particularly it is http://localhost not ws://localhost, and even wss://localhost (that additional s is for safe) so I must explicitly permit 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 if you would like, 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 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, advisor, father, diabetic, and Microsoft worker. He’s a failed stand-up comedian, a cornrower, and a ebook creator.

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