Changes for a path proxyable webpanel

README.md

@@ -119,7 +119,7 @@ Create an `appsettings.Production.yml` file next to `appsettings.yml`. This will
 
 - `General:GitHubAccessToken`: Specify a GitHub personal access token with no scopes here to highly mitigate the possiblity of 429 response codes from GitHub requests
 
-- `General:SkipAddingByondFirewallException`: Set to false if you have Windows firewall disabled
+- `General:SkipAddingByondFirewallException`: Set to `true` if you have Windows firewall disabled
 
 - `Session:HighPriorityLiveDreamDaemon`: Boolean controlling if live DreamDaemon instances get set to above normal priority processes.
 
@@ -143,6 +143,8 @@ Create an `appsettings.Production.yml` file next to `appsettings.yml`. This will
 
 - `ControlPanel:AllowedOrigins`: Set the Access-Control-Allow-Origin headers to this list of origins for all responses (also enables all headers and methods). This is overridden by `ControlPanel:AllowAnyOrigin`
 
+- `ControlPanel:PublicPath`: URL from which the webpanel can be accessed, defaults to "/app/". Must be an absolute path (https://example.org/path/to/webpanel) or a path starting from root (/path/to/webpanel). Note that this option does not relocate the webpanel for you; you will need a reverse proxy to relocate the webpanel
+
 - `Elasticsearch`: tgstation-server also supports automatically ingesting its logs to ElasticSearch. You can set this up in the setup wizard, or with the following configuration:
   ```yml
   Elasticsearch:

build/Version.props

@@ -4,7 +4,7 @@
   <Import Project="ControlPanelVersion.props" />
   <PropertyGroup>
     <TgsCoreVersion>5.1.0</TgsCoreVersion>
-    <TgsConfigVersion>4.3.0</TgsConfigVersion>
+    <TgsConfigVersion>4.4.0</TgsConfigVersion>
     <TgsApiVersion>9.6.0</TgsApiVersion>
     <TgsApiLibraryVersion>10.0.0</TgsApiLibraryVersion>
     <TgsClientVersion>11.0.0</TgsClientVersion>

src/Tgstation.Server.Host/Configuration/ControlPanelConfiguration.cs

@@ -27,6 +27,11 @@ namespace Tgstation.Server.Host.Configuration
 		/// </summary>
 		public string Channel { get; set; }
 
+		/// <summary>
+		/// The public path to the TGS control panel from a wider network.
+		/// </summary>
+		public string PublicPath { get; set; }
+
 		/// <summary>
 		/// Origins allowed for CORS requests.
 		/// </summary>

src/Tgstation.Server.Host/Controllers/ControlPanelController.cs

@@ -1,9 +1,12 @@
 using System;
+using System.Collections.Generic;
 using System.Globalization;
 using System.Net.Mime;
+using System.Threading.Tasks;
 
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Filters;
 using Microsoft.AspNetCore.StaticFiles;
 using Microsoft.Extensions.Options;
 using Microsoft.Extensions.Primitives;
@@ -26,6 +29,11 @@ namespace Tgstation.Server.Host.Controllers
 		/// </summary>
 		public const string ControlPanelRoute = "/app";
 
+		/// <summary>
+		/// Header for forcing channel.json to be fetched.
+		/// </summary>
+		const string FetchChannelVaryHeader = "X-Webpanel-Fetch-Channel";
+
 		/// <summary>
 		/// The <see cref="IWebHostEnvironment"/> for the <see cref="ControlPanelController"/>.
 		/// </summary>
@@ -70,9 +78,28 @@ namespace Tgstation.Server.Host.Controllers
 			{
 				FormatVersion = 1,
 				Channel = controlPanelChannel,
+				controlPanelConfiguration.PublicPath,
 			});
 		}
 
+		/// <inheritdoc />
+		public override Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
+		{
+			if (context == null)
+				throw new ArgumentNullException(nameof(context));
+
+			var newValues = new List<string> { FetchChannelVaryHeader };
+			var headers = context.HttpContext.Response.Headers;
+			if (headers.TryGetValue(HeaderNames.Vary, out var oldValues))
+				headers.Remove(HeaderNames.Vary);
+
+			newValues.AddRange(oldValues);
+
+			headers.Add(HeaderNames.Vary, new StringValues(newValues.ToArray()));
+
+			return base.OnActionExecutionAsync(context, next);
+		}
+
 		/// <summary>
 		/// Handle a GET request to the control panel route. Route to static files if they exist, otherwise index.html.
 		/// </summary>
@@ -80,8 +107,11 @@ namespace Tgstation.Server.Host.Controllers
 		/// <returns>The <see cref="VirtualFileResult"/> to use.</returns>
 		[Route("{**appRoute}")]
 		[HttpGet]
-		public VirtualFileResult Get([FromRoute] string appRoute)
+		public IActionResult Get([FromRoute] string appRoute)
 		{
+			if (Request.Headers.ContainsKey(FetchChannelVaryHeader))
+				return GetChannelJson();
+
 			var fileInfo = hostEnvironment.WebRootFileProvider.GetFileInfo(appRoute);
 			if (fileInfo.Exists)
 			{

src/Tgstation.Server.Host/appsettings.yml

@@ -35,6 +35,7 @@ ControlPanel:
   Channel: https://tgstation.github.io/tgstation-server-webpanel/api/${Major}.${Minor}.${Patch}
   AllowAnyOrigin: false
   AllowedOrigins: []
+  PublicPath:
 Updates:
   GitHubRepositoryId: 92952846
   GitTagPrefix: tgstation-server-v