Add HostCheckTransformer

bundler/src/main/java/dev/openrs2/bundler/transform/HostCheckTransformer.java

@@ -0,0 +1,90 @@
+package dev.openrs2.bundler.transform;
+
+import dev.openrs2.asm.InsnMatcher;
+import dev.openrs2.asm.classpath.ClassPath;
+import dev.openrs2.asm.transform.Transformer;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.Type;
+import org.objectweb.asm.tree.ClassNode;
+import org.objectweb.asm.tree.InsnNode;
+import org.objectweb.asm.tree.MethodInsnNode;
+import org.objectweb.asm.tree.MethodNode;
+import org.objectweb.asm.tree.analysis.AnalyzerException;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public final class HostCheckTransformer extends Transformer {
+	private static final Logger logger = LoggerFactory.getLogger(HostCheckTransformer.class);
+
+	private static final InsnMatcher GET_HOST_MATCHER = InsnMatcher.compile("INVOKEVIRTUAL INVOKEVIRTUAL INVOKEVIRTUAL");
+
+	private int hostChecks;
+
+	@Override
+	protected void preTransform(ClassPath classPath) throws AnalyzerException {
+		hostChecks = 0;
+	}
+
+	@Override
+	protected boolean transformCode(ClassNode clazz, MethodNode method) throws AnalyzerException {
+		if (Type.getReturnType(method.desc).getSort() != Type.BOOLEAN) {
+			return false;
+		}
+
+		GET_HOST_MATCHER.match(method).forEach(match -> {
+			var insn1 = (MethodInsnNode) match.get(0);
+			if (!insn1.owner.equals(clazz.name)) {
+				return;
+			}
+
+			if (!insn1.name.equals("getDocumentBase")) {
+				return;
+			}
+
+			if (!insn1.desc.equals("()Ljava/net/URL;")) {
+				return;
+			}
+
+			var insn2 = (MethodInsnNode) match.get(1);
+			if (!insn2.owner.equals("java/net/URL")) {
+				return;
+			}
+
+			if (!insn2.name.equals("getHost")) {
+				return;
+			}
+
+			if (!insn2.desc.equals("()Ljava/lang/String;")) {
+				return;
+			}
+
+			var insn3 = (MethodInsnNode) match.get(2);
+			if (!insn3.owner.equals("java/lang/String")) {
+				return;
+			}
+
+			if (!insn3.name.equals("toLowerCase")) {
+				return;
+			}
+
+			if (!insn3.desc.equals("()Ljava/lang/String;")) {
+				return;
+			}
+
+			method.instructions.clear();
+			method.tryCatchBlocks.clear();
+
+			method.instructions.add(new InsnNode(Opcodes.ICONST_1));
+			method.instructions.add(new InsnNode(Opcodes.IRETURN));
+
+			hostChecks++;
+		});
+
+		return false;
+	}
+
+	@Override
+	protected void postTransform(ClassPath classPath) throws AnalyzerException {
+		logger.info("Removed {} host checks", hostChecks);
+	}
+}

deob/src/main/java/dev/openrs2/deob/Deobfuscator.java

@@ -10,6 +10,7 @@ import com.google.common.collect.ImmutableList;
 import dev.openrs2.asm.classpath.ClassPath;
 import dev.openrs2.asm.classpath.Library;
 import dev.openrs2.asm.transform.Transformer;
+import dev.openrs2.bundler.transform.HostCheckTransformer;
 import dev.openrs2.bundler.transform.RightClickTransformer;
 import dev.openrs2.deob.remap.ClassNamePrefixer;
 import dev.openrs2.deob.remap.TypedRemapper;
@@ -31,6 +32,7 @@ public final class Deobfuscator {
 	private static final Logger logger = LoggerFactory.getLogger(Deobfuscator.class);
 
 	private static final List<Transformer> TRANSFORMERS = List.of(
+		new HostCheckTransformer(),
 		new RightClickTransformer(),
 		new OpaquePredicateTransformer(),
 		new ExceptionTracingTransformer(),