Validate Bedrock URL pack responses

README.md

@@ -73,7 +73,7 @@ The SHA-1 response must contain a 40-character hexadecimal SHA-1. Both of these
 ### Bedrock Edition through GeyserMC
 
 - Preferred remote mode: set `bedrockResourcePackUrl` to a direct `.mcpack` or `.zip` download URL. RemotePackSync creates a Geyser `UrlPackCodec` and registers it through the public `SessionLoadResourcePacksEvent` API, so Geyser supplies the URL to connecting Bedrock clients.
-- The remote server must return `Content-Type: application/zip` and an exact `Content-Length`. Redirects are allowed only when they ultimately resolve to a valid direct download. The URL should be stable and should expose a changed ETag or URL when the pack changes.
+- The remote server must return `Content-Type: application/zip` and an exact `Content-Length`. RemotePackSync verifies those headers (following redirects) before registering the URL; a provider that returns `application/octet-stream` is not compatible with Bedrock URL packs. Redirects are allowed only when they ultimately resolve to a valid direct download. The URL should be stable and should expose a changed ETag or URL when the pack changes.
 - Geyser validates/downloads remote URL packs during its lifecycle. Use `/remotepacksync reload` after changing the URL or after replacing a pack at the same URL; players already connected must reconnect.
 - Local alternative: set `bedrockResourcePack` to a `.mcpack` or `.zip` file. The source is checked asynchronously at `refreshInterval`; changes receive a deterministic manifest UUID and are managed under `plugins/RemotePackSync/bedrock-managed/`.
 - The original configured local pack is never modified.

src/main/java/io/github/lf1/remotepacksync/BedrockPackManager.java

@@ -12,6 +12,10 @@ import org.geysermc.geyser.api.pack.option.ResourcePackOption;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.AtomicMoveNotSupportedException;
 import java.nio.file.Files;
@@ -33,6 +37,9 @@ import java.util.zip.ZipOutputStream;
 /** Maintains a managed Bedrock pack and registers its current version for new Geyser sessions. */
 public final class BedrockPackManager {
     private static final int MAX_MANIFEST_BYTES = 1024 * 1024;
+    private static final HttpClient HTTP_CLIENT = HttpClient.newBuilder()
+            .followRedirects(HttpClient.Redirect.NORMAL)
+            .build();
     private static final Pattern HEADER_PROPERTY = Pattern.compile("\\\"header\\\"\\s*:\\s*\\{");
     private static final Pattern UUID_PROPERTY = Pattern.compile("\\\"uuid\\\"\\s*:\\s*\\\"[^\\\"]*\\\"");
 
@@ -41,6 +48,7 @@ public final class BedrockPackManager {
 
     private volatile BedrockPackSettings settings;
     private BukkitTask refreshTask;
+    private GeyserEventRegistrar geyserEventRegistrar;
     private boolean subscribed;
 
     public BedrockPackManager(JavaPlugin plugin) {
@@ -76,6 +84,16 @@ public final class BedrockPackManager {
             refreshTask.cancel();
             refreshTask = null;
         }
+        if (geyserEventRegistrar != null) {
+            try {
+                GeyserApi.api().eventBus().unregisterAll(geyserEventRegistrar);
+            } catch (RuntimeException | LinkageError exception) {
+                plugin.getLogger().log(Level.FINE, "Could not unregister the Geyser Bedrock resource-pack handler.", exception);
+            } finally {
+                geyserEventRegistrar = null;
+                subscribed = false;
+            }
+        }
     }
 
     private void subscribeToGeyser() {
@@ -89,11 +107,13 @@ public final class BedrockPackManager {
         }
 
         try {
-            GeyserEventRegistrar registrar = new GeyserEventRegistrar();
+            geyserEventRegistrar = new GeyserEventRegistrar();
-            GeyserApi.api().eventBus().subscribe(registrar, SessionLoadResourcePacksEvent.class, this::registerForSession);
+            GeyserApi.api().eventBus().subscribe(
+                    geyserEventRegistrar, SessionLoadResourcePacksEvent.class, this::registerForSession);
             subscribed = true;
             plugin.getLogger().info("Registered Geyser Bedrock resource-pack session handler.");
         } catch (RuntimeException | LinkageError exception) {
+            geyserEventRegistrar = null;
             plugin.getLogger().log(Level.WARNING, "Could not initialize Geyser Bedrock resource-pack support: "
                     + exception.getMessage(), exception);
         }
@@ -120,6 +140,7 @@ public final class BedrockPackManager {
 
         try {
             if (activeSettings.isRemote()) {
+                validateRemotePackUrl(activeSettings.remoteUrl());
                 ResourcePack resourcePack = ResourcePack.create(PackCodec.url(activeSettings.remoteUrl()));
                 if (activeSettings != settings) {
                     return;
@@ -156,6 +177,39 @@ public final class BedrockPackManager {
         }
     }
 
+    /**
+     * Geyser gives URL packs to Bedrock clients as URLs. Unlike Geyser's server-side
+     * download, the Bedrock client requires a direct response with application/zip
+     * and a real Content-Length, so catch bad hosting before registering the pack.
+     */
+    private static void validateRemotePackUrl(String url) throws IOException, InterruptedException {
+        HttpRequest request = HttpRequest.newBuilder(URI.create(url))
+                .method("HEAD", HttpRequest.BodyPublishers.noBody())
+                .header("Accept", "application/zip")
+                .build();
+        HttpResponse<Void> response = HTTP_CLIENT.send(request, HttpResponse.BodyHandlers.discarding());
+        if (response.statusCode() < 200 || response.statusCode() >= 300) {
+            throw new IOException("Remote Bedrock pack returned HTTP " + response.statusCode() + ".");
+        }
+        validateRemotePackHeaders(
+                response.headers().firstValue("Content-Type").orElse(null),
+                response.headers().firstValue("Content-Length").orElse(null));
+    }
+
+    static void validateRemotePackHeaders(String contentType, String contentLength) throws IOException {
+        if (contentType == null || !contentType.toLowerCase(java.util.Locale.ROOT).startsWith("application/zip")) {
+            throw new IOException("Remote Bedrock pack must return Content-Type: application/zip, but returned "
+                    + (contentType == null ? "no Content-Type header" : contentType) + ".");
+        }
+        try {
+            if (contentLength == null || Long.parseLong(contentLength) <= 0) {
+                throw new NumberFormatException();
+            }
+        } catch (NumberFormatException exception) {
+            throw new IOException("Remote Bedrock pack must return a positive, exact Content-Length header.");
+        }
+    }
+
     private Path writeManagedPack(Path source, byte[] sourceSha256) throws IOException {
         String sourceName = source.getFileName().toString().toLowerCase(java.util.Locale.ROOT);
         String extension = sourceName.endsWith(".mcpack") ? ".mcpack" : ".zip";

src/main/java/io/github/lf1/remotepacksync/RemotePackSyncPlugin.java

@@ -108,6 +108,9 @@ public final class RemotePackSyncPlugin extends JavaPlugin implements Listener,
             return;
         }
         if (getServer().getPluginManager().getPlugin("Geyser-Spigot") == null) {
+            if (bedrockPackManager != null) {
+                bedrockPackManager.configure(null);
+            }
             getLogger().warning("bedrockResourcePack is configured, but Geyser-Spigot is not installed; Bedrock delivery is disabled.");
             return;
         }

src/test/java/io/github/lf1/remotepacksync/BedrockPackManagerTest.java

@@ -5,6 +5,7 @@ import org.junit.jupiter.api.Test;
 import java.io.IOException;
 import java.util.UUID;
 
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
@@ -34,6 +35,22 @@ final class BedrockPackManagerTest {
         assertEquals(1, occurrences(updated, "module-uuid-must-not-change"));
     }
 
+    @Test
+    void acceptsBedrockClientCompatibleRemoteHeaders() {
+        assertDoesNotThrow(() -> BedrockPackManager.validateRemotePackHeaders("application/zip", "10406764"));
+        assertDoesNotThrow(() -> BedrockPackManager.validateRemotePackHeaders("application/zip; charset=binary", "1"));
+    }
+
+    @Test
+    void rejectsRemoteHeadersThatBedrockClientsCannotUse() {
+        IOException contentType = assertThrows(IOException.class,
+                () -> BedrockPackManager.validateRemotePackHeaders("application/octet-stream", "10406764"));
+        assertEquals("Remote Bedrock pack must return Content-Type: application/zip, but returned application/octet-stream.",
+                contentType.getMessage());
+        assertThrows(IOException.class, () -> BedrockPackManager.validateRemotePackHeaders("application/zip", null));
+        assertThrows(IOException.class, () -> BedrockPackManager.validateRemotePackHeaders("application/zip", "0"));
+    }
+
     @Test
     void rejectsManifestWithoutHeaderUuid() {
         assertThrows(IOException.class, () -> BedrockPackManager.replaceHeaderUuid(