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. It’s essential to spend a while studying and you might find yourself with a considerably subtle listing 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 have been even onerous coded.
DasBlog is a pretty big and funky app and we observed 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 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 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 by way of Razor Pages and altering CSS! It could 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 by way of launch.json, launchsettings, or an surroundings variable like this, I can see that further 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 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) for those who run it. You may word that operating the precise EXE is all the time WAY sooner as properly! 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 aspect of Improvement-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'".
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 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’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 Improvement. Now, if I am utilizing each CSPs and WebSockets (ws:, wss:) in Manufacturing, I am going to have to be intentional about this.
What is the ethical?
For those who begin utilizing CSP Headers to tighten issues up, be acutely aware and conscious of the headers you want for conveniences like Scorching Reload in Improvement versus no matter issues you might 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 guide creator.
