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Implement discovery service patch for 26.3 #83

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JuniorWolfgamingDE wants to merge 1 commit into from
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Implement discovery service patch for 26.3 #83

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59 changes: 58 additions & 1 deletion Agent/src/main/java/net/lenni0451/authhook/UrlRedirector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,17 +21,25 @@
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.tree.AbstractInsnNode;
import org.objectweb.asm.tree.ClassNode;
import org.objectweb.asm.tree.InsnList;
import org.objectweb.asm.tree.LdcInsnNode;
import org.objectweb.asm.tree.MethodInsnNode;
import org.objectweb.asm.tree.MethodNode;

import java.lang.instrument.ClassFileTransformer;
import java.security.ProtectionDomain;
import java.util.Map;

import static org.objectweb.asm.Opcodes.ARETURN;
import static org.objectweb.asm.Opcodes.INVOKEVIRTUAL;

public class UrlRedirector implements ClassFileTransformer {

private static final String URL = "https://sessionserver.mojang.com";

private static final String DISCOVERY_SERVICE_CLASS = "MinecraftServicesDiscoveryService";
private static final String GET_URL_METHOD = "getUrl";

private final String targetAddress;
private final String secretKey;

Expand All @@ -52,9 +60,11 @@ private String formatUrl(String url) {

@Override
public byte[] transform(final ClassLoader loader, final String className, final Class<?> classBeingRedefined, final ProtectionDomain protectionDomain, final byte[] classfileBuffer) {
final boolean isDiscoveryService = className != null && className.endsWith(DISCOVERY_SERVICE_CLASS);
try {
final ClassNode node = this.read(classfileBuffer);
boolean modified = false;

for (MethodNode method : node.methods) {
for (AbstractInsnNode insn : method.instructions) {
if (insn instanceof LdcInsnNode && ((LdcInsnNode) insn).cst instanceof String) {
Expand All @@ -71,12 +81,59 @@ public byte[] transform(final ClassLoader loader, final String className, final
}
}
}

if (isDiscoveryService) {
modified |= this.patchDiscoveryService(node);
}

return modified ? this.write(node) : null;
} catch (final Throwable ignored) {
} catch (final Throwable t) {
if (isDiscoveryService) {
System.err.println("Failed to transform '" + className + "'");
t.printStackTrace();
}
}
return null;
}

private boolean patchDiscoveryService(final ClassNode node) {
final String replacement = this.targetAddress + "/" + this.secretKey;
boolean modified = false;

for (MethodNode method : node.methods) {
if (!GET_URL_METHOD.equals(method.name)) {
continue;
}
if (!method.desc.endsWith(")Ljava/lang/String;")) {
continue;
}

boolean methodModified = false;
for (AbstractInsnNode insn : method.instructions) {
if (insn.getOpcode() == ARETURN) {
final InsnList inject = new InsnList();
inject.add(new LdcInsnNode(URL));
inject.add(new LdcInsnNode(replacement));
inject.add(new MethodInsnNode(
INVOKEVIRTUAL,
"java/lang/String",
"replace",
"(Ljava/lang/CharSequence;Ljava/lang/CharSequence;)Ljava/lang/String;",
false
));
method.instructions.insertBefore(insn, inject);
methodModified = true;
}
}

if (methodModified) {
modified = true;
System.out.println("Patched discovery getUrl in class '" + node.name + "' method '" + method.name + method.desc + "'");
}
}
return modified;
}

private ClassNode read(final byte[] bytes) {
final ClassNode node = new ClassNode();
final ClassReader reader = new ClassReader(bytes);
Expand Down