Test patchwork user agent with regex instead

Author: FeTetra

ProjectLighthouse.Servers.GameServer/Controllers/Login/LoginController.cs

@@ -215,7 +215,7 @@ public async Task<IActionResult> Login()
 
         if (ServerConfiguration.Instance.Authentication.RequirePatchworkUserAgent)
         {
-            if (!PatchworkHelper.UserHasValidPatchworkUserAgent(this.Request.Headers.UserAgent.ToString()))
+            if (!PatchworkHelper.IsValidPatchworkUserAgent(this.Request.Headers.UserAgent.ToString()))
             {
                 return this.Forbid();
             }

ProjectLighthouse.Servers.GameServer/Helpers/PatchworkHelper.cs

@@ -1,31 +1,21 @@
 using LBPUnion.ProjectLighthouse.Configuration;
+using System.Text.RegularExpressions;
 
 namespace LBPUnion.ProjectLighthouse.Servers.GameServer.Helpers;
 
 public static class PatchworkHelper
 {
-    static int patchworkMajorVer = ServerConfiguration.Instance.Authentication.PatchworkMajorVersionMinimum;
-    static int patchworkMinorVer = ServerConfiguration.Instance.Authentication.PatchworkMinorVersionMinimum;
-    public static bool UserHasValidPatchworkUserAgent(string userAgent)
+    static int requiredMajor = ServerConfiguration.Instance.Authentication.PatchworkMajorVersionMinimum;
+    static int requiredMinor = ServerConfiguration.Instance.Authentication.PatchworkMinorVersionMinimum;
+    public static bool IsValidPatchworkUserAgent(string userAgent)
     {
-        string userAgentPrefix = "PatchworkLBP";
-        char gameVersion = userAgent[userAgentPrefix.Length];
+        Match result = Regex.Match(userAgent, @"^PatchworkLBP[123V] (\d{1,5})\.(\d{1,5})$");
+        if (!result.Success) return false;
 
-        if (!userAgent.StartsWith(userAgentPrefix))
+        if (!int.TryParse(result.Groups[1].Value, out int major) || !int.TryParse(result.Groups[2].Value, out int minor))
             return false;
 
-        switch (gameVersion) {
-            case '1':
-            case '2':
-            case '3':
-            case 'V':
-                break;
-            default:
-                return false;
-        }
-
-        string[] patchworkVer = userAgent.Split(' ')[1].Split('.');
-        if (int.Parse(patchworkVer[0]) !>= patchworkMajorVer || int.Parse(patchworkVer[1]) !>= patchworkMinorVer)
+        if (major < requiredMajor || minor < requiredMinor)
             return false;
 
         return true;

ProjectLighthouse.Tests.GameApiTests/Unit/Helpers/PatchworkUserAgentTests.cs

@@ -0,0 +1,45 @@
+using System;
+using LBPUnion.ProjectLighthouse.Servers.GameServer.Helpers;
+using Xunit;
+
+namespace ProjectLighthouse.Tests.GameApiTests.Unit.Helpers;
+
+[Trait("Category", "Unit")]
+public class PatchworkUserAgentTests
+{
+    [Fact]
+    public void CanValidatePatchworkUserAgents()
+    {
+        string[] validUserAgents = {
+            "PatchworkLBP1 1.0",
+            "PatchworkLBP2 2.0",
+            "PatchworkLBP3 3.0",
+            "PatchworkLBPV 4.0",
+            "PatchworkLBP1 1.5",
+        };
+
+        string[] invalidUserAgents = {
+            // Matching
+            "patchworklbp1 1.0", // Case sensitive
+            "ptchwrklbp1 1.0", // Misspelled
+            "PatchworkLBP1 1", // Missing major/minor
+            "PatchworkLBP1 1.000001", // Major/minor too long
+
+            // Data
+            "PatchworkLBP1 0.5", // Version number too low
+            "PatchworkLBP1 A.0" // Int cannot be parsed
+        };
+
+        bool result;
+        for (int i = 0; i < validUserAgents.Length; i++)
+        {
+            result = PatchworkHelper.IsValidPatchworkUserAgent(validUserAgents[i]);
+            Assert.True(result, $"Valid user agent: \"{validUserAgents[i]}\" was evaluated as {result}.");
+        }
+        for (int i = 0; i < invalidUserAgents.Length; i++)
+        {
+            result = PatchworkHelper.IsValidPatchworkUserAgent(invalidUserAgents[i]);
+            Assert.False(result, $"Invalid user agent: \"{invalidUserAgents[i]}\" was evaluated as {result}.");
+        }
+    }
+}