Deobfuscate stacktraces in log messages, crash reports, and etc.

paper-server/src/main/java/io/papermc/paper/util/ObfHelper.java

@@ -0,0 +1,156 @@
+package io.papermc.paper.util;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.stream.Collectors;
+import net.neoforged.srgutils.IMappingFile;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+
+@DefaultQualifier(NonNull.class)
+public enum ObfHelper {
+    INSTANCE;
+
+    private final @Nullable Map<String, ClassMapping> mappingsByObfName;
+    private final @Nullable Map<String, ClassMapping> mappingsByMojangName;
+
+    ObfHelper() {
+        final @Nullable Set<ClassMapping> maps = loadMappingsIfPresent();
+        if (maps != null) {
+            this.mappingsByObfName = maps.stream().collect(Collectors.toUnmodifiableMap(ClassMapping::obfName, map -> map));
+            this.mappingsByMojangName = maps.stream().collect(Collectors.toUnmodifiableMap(ClassMapping::mojangName, map -> map));
+        } else {
+            this.mappingsByObfName = null;
+            this.mappingsByMojangName = null;
+        }
+    }
+
+    public @Nullable Map<String, ClassMapping> mappingsByObfName() {
+        return this.mappingsByObfName;
+    }
+
+    public @Nullable Map<String, ClassMapping> mappingsByMojangName() {
+        return this.mappingsByMojangName;
+    }
+
+    /**
+     * Attempts to get the obf name for a given class by its Mojang name. Will
+     * return the input string if mappings are not present.
+     *
+     * @param fullyQualifiedMojangName fully qualified class name (dotted)
+     * @return mapped or original fully qualified (dotted) class name
+     */
+    public String reobfClassName(final String fullyQualifiedMojangName) {
+        if (this.mappingsByMojangName == null) {
+            return fullyQualifiedMojangName;
+        }
+
+        final ClassMapping map = this.mappingsByMojangName.get(fullyQualifiedMojangName);
+        if (map == null) {
+            return fullyQualifiedMojangName;
+        }
+
+        return map.obfName();
+    }
+
+    /**
+     * Attempts to get the Mojang name for a given class by its obf name. Will
+     * return the input string if mappings are not present.
+     *
+     * @param fullyQualifiedObfName fully qualified class name (dotted)
+     * @return mapped or original fully qualified (dotted) class name
+     */
+    public String deobfClassName(final String fullyQualifiedObfName) {
+        if (this.mappingsByObfName == null) {
+            return fullyQualifiedObfName;
+        }
+
+        final ClassMapping map = this.mappingsByObfName.get(fullyQualifiedObfName);
+        if (map == null) {
+            return fullyQualifiedObfName;
+        }
+
+        return map.mojangName();
+    }
+
+    private static @Nullable Set<ClassMapping> loadMappingsIfPresent() {
+        try (final @Nullable InputStream mappingsInputStream = ObfHelper.class.getClassLoader().getResourceAsStream("META-INF/mappings/reobf.tiny")) {
+            if (mappingsInputStream == null) {
+                return null;
+            }
+            final IMappingFile mappings = IMappingFile.load(mappingsInputStream); // Mappings are mojang->spigot
+            final Set<ClassMapping> classes = new HashSet<>();
+
+            final StringPool pool = new StringPool();
+            for (final IMappingFile.IClass cls : mappings.getClasses()) {
+                final Map<String, String> methods = new HashMap<>();
+                final Map<String, String> fields = new HashMap<>();
+                final Map<String, String> strippedMethods = new HashMap<>();
+
+                for (final IMappingFile.IMethod methodMapping : cls.getMethods()) {
+                    methods.put(
+                            pool.string(methodKey(
+                                    Objects.requireNonNull(methodMapping.getMapped()),
+                                    Objects.requireNonNull(methodMapping.getMappedDescriptor())
+                            )),
+                            pool.string(Objects.requireNonNull(methodMapping.getOriginal()))
+                    );
+
+                    strippedMethods.put(
+                            pool.string(pool.string(strippedMethodKey(
+                                    methodMapping.getMapped(),
+                                    methodMapping.getDescriptor()
+                            ))),
+                            pool.string(methodMapping.getOriginal())
+                    );
+                }
+                for (final IMappingFile.IField field : cls.getFields()) {
+                    fields.put(
+                            pool.string(field.getMapped()),
+                            pool.string(field.getOriginal())
+                    );
+                }
+
+                final ClassMapping map = new ClassMapping(
+                        Objects.requireNonNull(cls.getMapped()).replace('/', '.'),
+                        Objects.requireNonNull(cls.getOriginal()).replace('/', '.'),
+                        Map.copyOf(methods),
+                        Map.copyOf(fields),
+                        Map.copyOf(strippedMethods)
+                );
+                classes.add(map);
+            }
+
+            return Set.copyOf(classes);
+        } catch (final IOException ex) {
+            System.err.println("Failed to load mappings.");
+            ex.printStackTrace();
+            return null;
+        }
+    }
+
+    public static String strippedMethodKey(final String methodName, final String methodDescriptor) {
+        final String methodKey = methodKey(methodName, methodDescriptor);
+        final int returnDescriptorEnd = methodKey.indexOf(')');
+        return methodKey.substring(0, returnDescriptorEnd + 1);
+    }
+
+    public static String methodKey(final String methodName, final String methodDescriptor) {
+        return methodName + methodDescriptor;
+    }
+
+    public record ClassMapping(
+            String obfName,
+            String mojangName,
+            Map<String, String> methodsByObf,
+            Map<String, String> fieldsByObf,
+            // obf name with mapped desc to mapped name. return value is excluded from desc as reflection doesn't use it
+            Map<String, String> strippedMethods
+    ) {}
+}