Add online mode fix for legacy versions; minor refactors in legacy

Signed-off-by: TheKodeToad <TheKodeToad@proton.me>

libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/Handler.java

@@ -53,11 +53,16 @@ final class Handler extends URLStreamHandler {
     protected URLConnection openConnection(URL address, Proxy proxy) throws IOException {
         URLConnection result;
 
-        // try skin fix
+        // try various fixes...
         result = SkinFix.openConnection(address, proxy);
         if (result != null)
             return result;
 
+        result = OnlineModeFix.openConnection(address, proxy);
+        if (result != null)
+            return result;
+
+        // ...then give up and make the request directly
         return UrlUtils.openConnection(address, proxy);
     }
 }

libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/OnlineFixes.java

@@ -46,6 +46,8 @@ import java.net.URLStreamHandlerFactory;
 
 /**
  * Fixes skins by redirecting to other URLs.
+ * Thanks to MineOnline for the implementation from which this was inspired!
+ * See https://github.com/ahnewark/MineOnline/tree/main/src/main/java/gg/codie/mineonline/protocol.
  *
  * @see {@link Handler}
  * @see {@link UrlUtils}

libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/OnlineModeFix.java

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-3.0-only
+/*
+ *  Prism Launcher - Minecraft Launcher
+ *  Copyright (C) 2023 TheKodeToad <TheKodeToad@proton.me>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, version 3.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  Linking this library statically or dynamically with other modules is
+ *  making a combined work based on this library. Thus, the terms and
+ *  conditions of the GNU General Public License cover the whole
+ *  combination.
+ *
+ *  As a special exception, the copyright holders of this library give
+ *  you permission to link this library with independent modules to
+ *  produce an executable, regardless of the license terms of these
+ *  independent modules, and to copy and distribute the resulting
+ *  executable under terms of your choice, provided that you also meet,
+ *  for each linked independent module, the terms and conditions of the
+ *  license of that module. An independent module is a module which is
+ *  not derived from or based on this library. If you modify this
+ *  library, you may extend this exception to your version of the
+ *  library, but you are not obliged to do so. If you do not wish to do
+ *  so, delete this exception statement from your version.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package org.prismlauncher.legacy.fix.online;
+
+import java.io.IOException;
+import java.net.MalformedURLException;
+import java.net.Proxy;
+import java.net.URL;
+import java.net.URLConnection;
+
+public final class OnlineModeFix {
+    public static URLConnection openConnection(URL address, Proxy proxy) throws IOException {
+        // we start with "http://www.minecraft.net/game/joinserver.jsp?user=..."
+        if (!(address.getHost().equals("www.minecraft.net") && address.getPath().equals("/game/joinserver.jsp")))
+            return null;
+
+        // change it to "https://session.minecraft.net/game/joinserver.jsp?user=..."
+        // this seems to be the modern version of the same endpoint...
+        // maybe Mojang planned to patch old versions of the game to use it
+        // if it ever disappears this should be changed to use sessionserver.mojang.com/session/minecraft/join
+        // which of course has a different usage requiring JSON serialisation...
+        URL url;
+        try {
+            url = new URL("https", "session.minecraft.net", address.getPort(), address.getFile());
+        } catch (MalformedURLException e) {
+            throw new AssertionError("url should be valid", e);
+        }
+
+        return url.openConnection();
+    }
+}

libraries/launcher/legacy/org/prismlauncher/legacy/fix/online/SkinFix.java

@@ -54,7 +54,7 @@ package org.prismlauncher.legacy.fix.online;
 
 import org.prismlauncher.legacy.utils.api.MojangApi;
 import org.prismlauncher.legacy.utils.api.Texture;
-import org.prismlauncher.legacy.utils.url.CustomUrlConnection;
+import org.prismlauncher.legacy.utils.url.ByteArrayUrlConnection;
 import org.prismlauncher.legacy.utils.url.UrlUtils;
 
 import java.awt.AlphaComposite;
@@ -97,9 +97,9 @@ final class SkinFix {
 
         URLConnection connection = UrlUtils.openConnection(texture.getUrl(), proxy);
         try (InputStream in = connection.getInputStream()) {
-            // thank you craftycodie!
+            // thank you ahnewark!
             // this is heavily based on
-            // https://github.com/craftycodie/MineOnline/blob/4f4f86f9d051e0a6fd7ff0b95b2a05f7437683d7/src/main/java/gg/codie/mineonline/gui/textures/TextureHelper.java#L17
+            // https://github.com/ahnewark/MineOnline/blob/4f4f86f9d051e0a6fd7ff0b95b2a05f7437683d7/src/main/java/gg/codie/mineonline/gui/textures/TextureHelper.java#L17
             BufferedImage image = ImageIO.read(in);
             Graphics2D graphics = image.createGraphics();
             graphics.setComposite(AlphaComposite.getInstance(AlphaComposite.SRC_OVER));
@@ -131,7 +131,7 @@ final class SkinFix {
             image = image.getSubimage(0, 0, 64, 32);
             ImageIO.write(image, "png", out);
 
-            return new CustomUrlConnection(out.toByteArray());
+            return new ByteArrayUrlConnection(out.toByteArray());
         }
     }
 

libraries/launcher/legacy/org/prismlauncher/legacy/utils/url/ByteArrayUrlConnection.java

@@ -40,16 +40,12 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.net.HttpURLConnection;
 
-public final class CustomUrlConnection extends HttpURLConnection {
+public final class ByteArrayUrlConnection extends HttpURLConnection {
     private final InputStream in;
 
-    public CustomUrlConnection(byte[] data) {
-        this(new ByteArrayInputStream(data));
-    }
-
-    public CustomUrlConnection(InputStream in) {
+    public ByteArrayUrlConnection(byte[] data) {
         super(null);
-        this.in = in;
+        this.in = new ByteArrayInputStream(data);
     }
 
     @Override
@@ -58,12 +54,7 @@ public final class CustomUrlConnection extends HttpURLConnection {
     }
 
     @Override
-    public void disconnect() {
-        try {
-            in.close();
-        } catch (IOException e) {
-        }
-    }
+    public void disconnect() {}
 
     @Override
     public InputStream getInputStream() throws IOException {

libraries/launcher/legacy/org/prismlauncher/legacy/utils/url/UrlUtils.java

@@ -101,7 +101,7 @@ public final class UrlUtils {
         } catch (IOException | Error | RuntimeException e) {
             throw e; // rethrow if possible
         } catch (Throwable e) {
-            throw new AssertionError(e); // oh dear! this isn't meant to happen
+            throw new AssertionError("openConnection should not throw", e); // oh dear! this isn't meant to happen
         }
     }
 }