When you’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 study in a short time about Content material-Safety-Coverage headers. It’s essential spend a while studying and chances are you’ll find yourself with a considerably subtle checklist 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 might be extra safety in the event that they got here out of a vault or have 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 have been unable to make use of Scorching Reload (by way of dotnet watch or from VS 2022). We will complain about it, or we will find out about the way it works and why it isn’t working for us!
Keep in mind: Nothing in your pc 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 assist C# (code behinds) but additionally Markup by way of Razor Pages and altering CSS! It might undoubtedly 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 surroundings 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 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 at all times assume it is in Growth (you actually inform it to revive, construct, and exec in a single run command) when you run it. You will notice that operating the precise EXE is at all times WAY sooner 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 consumer facet of Growth-time HotReload. our browser console we see :
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 quite a bit 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? Nicely, particularly it is http://localhost not ws://localhost, and even wss://localhost (that additional s is for safe) so I have to 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 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 do exactly wss:, solely in Growth. Now, if I am utilizing each CSPs and WebSockets (ws:, wss:) in Manufacturing, I will have to be intentional about this.
What is the ethical?
When you 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 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, guide, father, diabetic, and Microsoft worker. He’s a failed stand-up comedian, a cornrower, and a e book creator.
