feat: добавил prometheus экспортер

backend/UniVerse.Api/Middleware/LocalNetworksOnlyMiddleware.cs

@@ -0,0 +1,71 @@
+using System.Net;
+using System.Net.Sockets;
+
+namespace UniVerse.Api.Middleware;
+
+public sealed class LocalNetworksOnlyMiddleware
+{
+    private readonly RequestDelegate _next;
+    private readonly ILogger<LocalNetworksOnlyMiddleware> _logger;
+
+    public LocalNetworksOnlyMiddleware(RequestDelegate next, ILogger<LocalNetworksOnlyMiddleware> logger)
+    {
+        _next = next;
+        _logger = logger;
+    }
+
+    public async Task InvokeAsync(HttpContext context)
+    {
+        var remoteIpAddress = context.Connection.RemoteIpAddress;
+
+        if (remoteIpAddress is null || !IsLocalNetwork(remoteIpAddress))
+        {
+            _logger.LogWarning("Blocked metrics request from non-local address {RemoteIpAddress}", remoteIpAddress);
+            context.Response.StatusCode = StatusCodes.Status403Forbidden;
+            await context.Response.WriteAsync("Metrics endpoint is available only from local networks.");
+            return;
+        }
+
+        await _next(context);
+    }
+
+    private static bool IsLocalNetwork(IPAddress ipAddress)
+    {
+        if (IPAddress.IsLoopback(ipAddress))
+        {
+            return true;
+        }
+
+        if (ipAddress.IsIPv4MappedToIPv6)
+        {
+            ipAddress = ipAddress.MapToIPv4();
+        }
+
+        return ipAddress.AddressFamily switch
+        {
+            AddressFamily.InterNetwork => IsPrivateOrLinkLocalIPv4(ipAddress),
+            AddressFamily.InterNetworkV6 => IsPrivateOrLinkLocalIPv6(ipAddress),
+            _ => false
+        };
+    }
+
+    private static bool IsPrivateOrLinkLocalIPv4(IPAddress ipAddress)
+    {
+        var bytes = ipAddress.GetAddressBytes();
+
+        return bytes[0] == 10
+               || bytes[0] == 127
+               || (bytes[0] == 192 && bytes[1] == 168)
+               || (bytes[0] == 172 && bytes[1] is >= 16 and <= 31)
+               || (bytes[0] == 169 && bytes[1] == 254);
+    }
+
+    private static bool IsPrivateOrLinkLocalIPv6(IPAddress ipAddress)
+    {
+        var bytes = ipAddress.GetAddressBytes();
+
+        return ipAddress.IsIPv6LinkLocal
+               || ipAddress.IsIPv6SiteLocal
+               || (bytes[0] & 0xfe) == 0xfc;
+    }
+}