identity: add proxy controller

Foxchat.Identity/Controllers/Proxy/GuildsProxyController.cs

@@ -0,0 +1,21 @@
+using Foxchat.Core.Federation;
+using Foxchat.Core.Models;
+using Foxchat.Core.Models.Http;
+using Foxchat.Identity.Middleware;
+using Foxchat.Identity.Services;
+using Microsoft.AspNetCore.Mvc;
+
+namespace Foxchat.Identity.Controllers.Proxy;
+
+[Route("/_fox/proxy/guilds")]
+public class GuildsProxyController(
+    ILogger logger,
+    ChatInstanceResolverService chatInstanceResolverService,
+    RequestSigningService requestSigningService)
+    : ProxyControllerBase(logger, chatInstanceResolverService, requestSigningService)
+{
+    [Authorize("chat_client")]
+    [HttpPost]
+    public Task<IActionResult> CreateGuild([FromBody] GuildsApi.CreateGuildRequest req) =>
+        Proxy<Guilds.Guild>(HttpMethod.Post, req);
+}

Foxchat.Identity/Controllers/Proxy/ProxyControllerBase.cs

@@ -0,0 +1,38 @@
+using Foxchat.Core;
+using Foxchat.Core.Federation;
+using Foxchat.Identity.Middleware;
+using Foxchat.Identity.Services;
+using Microsoft.AspNetCore.Mvc;
+
+namespace Foxchat.Identity.Controllers.Proxy;
+
+[ApiController]
+[ClientAuthenticate]
+public class ProxyControllerBase(
+    ILogger logger,
+    ChatInstanceResolverService chatInstanceResolverService,
+    RequestSigningService requestSigningService) : ControllerBase
+{
+    internal async Task<IActionResult> Proxy<TResponse>(HttpMethod method, object? body = null) where TResponse : class
+    {
+        var acct = HttpContext.GetAccountOrThrow();
+
+        var path = HttpContext.Request.Path.ToString();
+        if (!path.StartsWith("/_fox/proxy"))
+            throw new FoxchatError("Proxy<T> used for endpoint that does not start with /_fox/proxy");
+        path = $"/_fox/chat/{path[12..]}";
+
+        if (!HttpContext.Request.Headers.TryGetValue(RequestSigningService.SERVER_HEADER, out var serverHeader))
+            throw new ApiError.BadRequest($"Invalid or missing {RequestSigningService.SERVER_HEADER} header.");
+        var server = serverHeader.ToString();
+
+        logger.Debug("Proxying {Method} request to {Domain}{Path}", method, server, path);
+
+        // Identity instances always initiate federation, so we have to make sure the instance knows about us.
+        // This also serves as a way to make sure the instance being requested actually exists.
+        await chatInstanceResolverService.ResolveChatInstanceAsync(serverHeader.ToString());
+
+        var resp = await requestSigningService.RequestAsync<TResponse>(method, server, path, acct.Id.ToString(), body);
+        return Ok(resp);
+    }
+}