testserver/patches/server/0429-Deobfuscate-stacktraces-in-log-messages-crash-report.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Sun, 20 Jun 2021 18:19:09 -0700
Subject: [PATCH] Deobfuscate stacktraces in log messages, crash reports, and
 etc.


diff --git a/build.gradle.kts b/build.gradle.kts
index eea412347cef390555166a988058ae877afdfa4a..b35e54380cb23758a813fa24d13b888f36906c23 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -1,8 +1,12 @@
 import com.github.jengelman.gradle.plugins.shadow.transformers.Log4j2PluginsCacheFileTransformer
 import com.github.jengelman.gradle.plugins.shadow.transformers.Transformer
+import io.papermc.paperweight.tasks.BaseTask
 import io.papermc.paperweight.util.Git
+import io.papermc.paperweight.util.defaultOutput
+import io.papermc.paperweight.util.openZip
 import io.papermc.paperweight.util.path
 import shadow.org.apache.logging.log4j.core.config.plugins.processor.PluginProcessor.PLUGIN_CACHE_FILE
+import java.nio.file.Files
 import java.util.Locale
 
 plugins {
@@ -13,6 +17,14 @@ plugins {
 
 repositories {
     maven("https://libraries.minecraft.net/")
+    // Paper start
+    maven("https://maven.quiltmc.org/repository/release/") {
+        mavenContent {
+            releasesOnly()
+            includeModule("org.quiltmc", "tiny-mappings-parser")
+        }
+    }
+    // Paper end
 }
 
 dependencies {
@@ -48,6 +60,8 @@ dependencies {
     implementation("co.aikar:cleaner:1.0-SNAPSHOT") // Paper
     implementation("io.netty:netty-all:4.1.65.Final") // Paper
 
+    implementation("org.quiltmc:tiny-mappings-parser:0.3.0") // Paper - needed to read mappings for stacktrace deobfuscation
+
     testImplementation("junit:junit:4.13.1")
     testImplementation("org.hamcrest:hamcrest-library:1.3")
 }
@@ -141,6 +155,44 @@ tasks.shadowJar {
     transform(ModifiedLog4j2PluginsCacheFileTransformer::class.java)
 }
 
+// Paper start - include reobf mappings in jar for stacktrace deobfuscation
+abstract class IncludeMappings : BaseTask() {
+    @get:InputFile
+    abstract val inputJar: RegularFileProperty
+
+    @get:InputFile
+    abstract val mappings: RegularFileProperty
+
+    @get:OutputFile
+    abstract val outputJar: RegularFileProperty
+
+    override fun init() {
+        outputJar.convention(defaultOutput())
+    }
+
+    @TaskAction
+    private fun addMappings() {
+        outputJar.get().asFile.parentFile.mkdirs()
+        inputJar.get().asFile.copyTo(outputJar.get().asFile, overwrite = true)
+        outputJar.get().path.openZip().use { fs ->
+            val dir = fs.getPath("META-INF/mappings/")
+            Files.createDirectories(dir)
+            val target = dir.resolve("reobf.tiny")
+            Files.copy(mappings.path, target)
+        }
+    }
+}
+
+val includeMappings = tasks.register<IncludeMappings>("includeMappings") {
+    inputJar.set(tasks.fixJarForReobf.flatMap { it.outputJar })
+    mappings.set(tasks.reobfJar.flatMap { it.mappingsFile })
+}
+
+tasks.reobfJar {
+    inputJar.set(includeMappings.flatMap { it.outputJar })
+}
+// Paper end - include reobf mappings in jar for stacktrace deobfuscation
+
 tasks.test {
     exclude("org/bukkit/craftbukkit/inventory/ItemStack*Test.class")
 }
diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
index f1034cfb63ea37c22e67b5d4a18214774f208de2..a8740f03a7feef40490e9f5be610c2c835114f08 100644
--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
+++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
@@ -433,4 +433,9 @@ public class PaperConfig {
             log("Async Chunks: Enabled - Chunks will be loaded much faster, without lag.");
         }
     }
+
+    public static boolean deobfuscateStacktraces = true;
+    private static void loggerSettings() {
+        deobfuscateStacktraces = getBoolean("settings.loggers.deobfuscate-stacktraces", deobfuscateStacktraces);
+    }
 }
diff --git a/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java b/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java
index 0bb4aaa546939b67a5d22865190f30478a9337c1..d3e619655382e50e9ac9323ed942502d85c9599c 100644
--- a/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java
+++ b/src/main/java/com/destroystokyo/paper/io/SyncLoadFinder.java
@@ -91,7 +91,7 @@ public class SyncLoadFinder {
 
                 final JsonArray traces = new JsonArray();
 
-                for (StackTraceElement element : pair.getFirst().stacktrace) {
+                for (StackTraceElement element : io.papermc.paper.util.StacktraceDeobfuscator.INSTANCE.deobfuscateStacktrace(pair.getFirst().stacktrace)) {
                     traces.add(String.valueOf(element));
                 }
 
diff --git a/src/main/java/io/papermc/paper/logging/StacktraceDeobfuscatingRewritePolicy.java b/src/main/java/io/papermc/paper/logging/StacktraceDeobfuscatingRewritePolicy.java
new file mode 100644
index 0000000000000000000000000000000000000000..d019802a36dbaca4bf299a55d28381e43d6b976f
--- /dev/null
+++ b/src/main/java/io/papermc/paper/logging/StacktraceDeobfuscatingRewritePolicy.java
@@ -0,0 +1,31 @@
+package io.papermc.paper.logging;
+
+import io.papermc.paper.util.StacktraceDeobfuscator;
+import org.apache.logging.log4j.core.Core;
+import org.apache.logging.log4j.core.LogEvent;
+import org.apache.logging.log4j.core.appender.rewrite.RewritePolicy;
+import org.apache.logging.log4j.core.config.plugins.Plugin;
+import org.apache.logging.log4j.core.config.plugins.PluginFactory;
+import org.jetbrains.annotations.NotNull;
+
+@Plugin(
+    name = "StacktraceDeobfuscatingRewritePolicy",
+    category = Core.CATEGORY_NAME,
+    elementType = "rewritePolicy",
+    printObject = true
+)
+public final class StacktraceDeobfuscatingRewritePolicy implements RewritePolicy {
+    @Override
+    public @NotNull LogEvent rewrite(final @NotNull LogEvent rewrite) {
+        final Throwable thrown = rewrite.getThrown();
+        if (thrown != null) {
+            StacktraceDeobfuscator.INSTANCE.deobfuscateThrowable(thrown);
+        }
+        return rewrite;
+    }
+
+    @PluginFactory
+    public static @NotNull StacktraceDeobfuscatingRewritePolicy createPolicy() {
+        return new StacktraceDeobfuscatingRewritePolicy();
+    }
+}
diff --git a/src/main/java/io/papermc/paper/util/ObfHelper.java b/src/main/java/io/papermc/paper/util/ObfHelper.java
new file mode 100644
index 0000000000000000000000000000000000000000..5ee513c0e2436e6afa3432f9f835d4028b37aed0
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/ObfHelper.java
@@ -0,0 +1,141 @@
+package io.papermc.paper.util;
+
+import com.google.common.base.Charsets;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
+import com.mojang.datafixers.util.Pair;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.util.Map;
+import java.util.Set;
+import net.fabricmc.mapping.tree.ClassDef;
+import net.fabricmc.mapping.tree.MethodDef;
+import net.fabricmc.mapping.tree.TinyMappingFactory;
+import net.fabricmc.mapping.tree.TinyTree;
+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;
+
+    public static final String MOJANG_PLUS_YARN_NAMESPACE = "mojang+yarn";
+    public static final String SPIGOT_NAMESPACE = "spigot";
+
+    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(ImmutableMap.toImmutableMap(ClassMapping::obfName, map -> map));
+            this.mappingsByMojangName = maps.stream().collect(ImmutableMap.toImmutableMap(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 TinyTree tree = TinyMappingFactory.loadWithDetection(new BufferedReader(new InputStreamReader(mappingsInputStream, Charsets.UTF_8)));
+            final var builder = ImmutableSet.<ClassMapping>builder();
+
+            for (final ClassDef classDef : tree.getClasses()) {
+                final String obfClassName = classDef.getName(SPIGOT_NAMESPACE).replace('/', '.');
+                final var methodMappings = ImmutableMap.<Pair<String, String>, MethodMapping>builder();
+
+                for (final MethodDef methodDef : classDef.getMethods()) {
+                    final MethodMapping method = new MethodMapping(
+                        methodDef.getName(SPIGOT_NAMESPACE),
+                        methodDef.getName(MOJANG_PLUS_YARN_NAMESPACE),
+                        methodDef.getDescriptor(SPIGOT_NAMESPACE)
+                    );
+                    methodMappings.put(
+                        new Pair<>(method.obfName(), method.descriptor()),
+                        method
+                    );
+                }
+
+                final ClassMapping map = new ClassMapping(
+                    obfClassName,
+                    classDef.getName(MOJANG_PLUS_YARN_NAMESPACE).replace('/', '.'),
+                    methodMappings.build()
+                );
+                builder.add(map);
+            }
+
+            return builder.build();
+        } catch (final IOException ex) {
+            System.err.println("Failed to load mappings for stacktrace deobfuscation.");
+            ex.printStackTrace();
+            return null;
+        }
+    }
+
+    public record ClassMapping(
+        String obfName,
+        String mojangName,
+        Map<Pair<String, String>, MethodMapping> methodMappings
+    ) {}
+
+    public record MethodMapping(
+        String obfName,
+        String mojangName,
+        String descriptor
+    ) {}
+}
diff --git a/src/main/java/io/papermc/paper/util/StacktraceDeobfuscator.java b/src/main/java/io/papermc/paper/util/StacktraceDeobfuscator.java
new file mode 100644
index 0000000000000000000000000000000000000000..f3099d3cfa4ea8ad56b1abdd0e7b77aaa4465244
--- /dev/null
+++ b/src/main/java/io/papermc/paper/util/StacktraceDeobfuscator.java
@@ -0,0 +1,156 @@
+package io.papermc.paper.util;
+
+import com.destroystokyo.paper.PaperConfig;
+import com.mojang.datafixers.util.Pair;
+import it.unimi.dsi.fastutil.ints.IntArrayList;
+import it.unimi.dsi.fastutil.ints.IntList;
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.Map;
+import org.checkerframework.checker.nullness.qual.NonNull;
+import org.checkerframework.checker.nullness.qual.Nullable;
+import org.checkerframework.framework.qual.DefaultQualifier;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.Label;
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
+
+@DefaultQualifier(NonNull.class)
+public enum StacktraceDeobfuscator {
+    INSTANCE;
+
+    private final Map<Class<?>, Map<Pair<String, String>, IntList>> lineMapCache = Collections.synchronizedMap(new LinkedHashMap<>(128, 0.75f, true) {
+        @Override
+        protected boolean removeEldestEntry(final Map.Entry<Class<?>, Map<Pair<String, String>, IntList>> eldest) {
+            return this.size() > 127;
+        }
+    });
+
+    public void deobfuscateThrowable(final Throwable throwable) {
+        if (!PaperConfig.deobfuscateStacktraces) {
+            return;
+        }
+
+        throwable.setStackTrace(this.deobfuscateStacktrace(throwable.getStackTrace()));
+        final Throwable cause = throwable.getCause();
+        if (cause != null) {
+            this.deobfuscateThrowable(cause);
+        }
+        for (final Throwable suppressed : throwable.getSuppressed()) {
+            this.deobfuscateThrowable(suppressed);
+        }
+    }
+
+    public StackTraceElement[] deobfuscateStacktrace(final StackTraceElement[] traceElements) {
+        if (!PaperConfig.deobfuscateStacktraces) {
+            return traceElements;
+        }
+
+        final @Nullable Map<String, ObfHelper.ClassMapping> mappings = ObfHelper.INSTANCE.mappingsByObfName();
+        if (mappings == null || traceElements.length == 0) {
+            return traceElements;
+        }
+        final StackTraceElement[] result = new StackTraceElement[traceElements.length];
+        for (int i = 0; i < traceElements.length; i++) {
+            final StackTraceElement element = traceElements[i];
+
+            final String className = element.getClassName();
+            final String methodName = element.getMethodName();
+
+            final ObfHelper.ClassMapping classMapping = mappings.get(className);
+            if (classMapping == null) {
+                result[i] = element;
+                continue;
+            }
+
+            final Class<?> clazz;
+            try {
+                clazz = Class.forName(className);
+            } catch (final ClassNotFoundException ex) {
+                throw new RuntimeException(ex);
+            }
+            final @Nullable Pair<String, String> nameDescriptorPair = this.determineMethodForLine(clazz, element.getLineNumber());
+            final ObfHelper.@Nullable MethodMapping methodMapping = nameDescriptorPair == null
+                ? null
+                : classMapping.methodMappings().get(nameDescriptorPair);
+
+            result[i] = new StackTraceElement(
+                element.getClassLoaderName(),
+                element.getModuleName(),
+                element.getModuleVersion(),
+                classMapping.mojangName(),
+                methodMapping != null ? methodMapping.mojangName() : methodName,
+                sourceFileName(classMapping.mojangName()),
+                element.getLineNumber()
+            );
+        }
+        return result;
+    }
+
+    private @Nullable Pair<String, String> determineMethodForLine(final Class<?> clazz, final int lineNumber) {
+        final Map<Pair<String, String>, IntList> lineMap = this.lineMapCache.computeIfAbsent(clazz, StacktraceDeobfuscator::buildLineMap);
+        for (final var entry : lineMap.entrySet()) {
+            final Pair<String, String> pair = entry.getKey();
+            final IntList lines = entry.getValue();
+            for (int i = 0, linesSize = lines.size(); i < linesSize; i++) {
+                final int num = lines.getInt(i);
+                if (num == lineNumber) {
+                    return pair;
+                }
+            }
+        }
+        return null;
+    }
+
+    private static String sourceFileName(final String fullClassName) {
+        final int dot = fullClassName.lastIndexOf('.');
+        final String className = dot == -1
+            ? fullClassName
+            : fullClassName.substring(dot + 1);
+        final String rootClassName = className.split("\\$")[0];
+        return rootClassName + ".java";
+    }
+
+    private static Map<Pair<String, String>, IntList> buildLineMap(final Class<?> key) {
+        final Map<Pair<String, String>, IntList> lineMap = new HashMap<>();
+        final class LineCollectingMethodVisitor extends MethodVisitor {
+            private final IntList lines = new IntArrayList();
+            private final String name;
+            private final String descriptor;
+
+            LineCollectingMethodVisitor(String name, String descriptor) {
+                super(Opcodes.ASM9);
+                this.name = name;
+                this.descriptor = descriptor;
+            }
+
+            @Override
+            public void visitLineNumber(int line, Label start) {
+                super.visitLineNumber(line, start);
+                this.lines.add(line);
+            }
+
+            @Override
+            public void visitEnd() {
+                super.visitEnd();
+                lineMap.put(new Pair<>(this.name, this.descriptor), this.lines);
+            }
+        }
+        final ClassVisitor classVisitor = new ClassVisitor(Opcodes.ASM9) {
+            @Override
+            public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+                return new LineCollectingMethodVisitor(name, descriptor);
+            }
+        };
+        try {
+            final ClassReader reader = new ClassReader(key.getName());
+            reader.accept(classVisitor, 0);
+        } catch (final IOException ex) {
+            throw new RuntimeException(ex);
+        }
+        return lineMap;
+    }
+}
diff --git a/src/main/java/io/papermc/paper/util/TraceUtil.java b/src/main/java/io/papermc/paper/util/TraceUtil.java
index 2d5494d2813b773e60ddba6790b750a9a08f21f8..7695bf44503f161523ea612ef8a884ae574a2e21 100644
--- a/src/main/java/io/papermc/paper/util/TraceUtil.java
+++ b/src/main/java/io/papermc/paper/util/TraceUtil.java
@@ -6,13 +6,15 @@ public final class TraceUtil {
 
     public static void dumpTraceForThread(Thread thread, String reason) {
         Bukkit.getLogger().warning(thread.getName() + ": " + reason);
-        StackTraceElement[] trace = thread.getStackTrace();
+        StackTraceElement[] trace = StacktraceDeobfuscator.INSTANCE.deobfuscateStacktrace(thread.getStackTrace());
         for (StackTraceElement traceElement : trace) {
             Bukkit.getLogger().warning("\tat " + traceElement);
         }
     }
 
     public static void dumpTraceForThread(String reason) {
-        new Throwable(reason).printStackTrace();
+        final Throwable throwable = new Throwable(reason);
+        StacktraceDeobfuscator.INSTANCE.deobfuscateThrowable(throwable);
+        throwable.printStackTrace();
     }
 }
diff --git a/src/main/java/net/minecraft/CrashReport.java b/src/main/java/net/minecraft/CrashReport.java
index 62c3c597732e6fb30ed5367d902ea8763507a6b8..b9a618eba86656289e20d051c3f0023ec93bb733 100644
--- a/src/main/java/net/minecraft/CrashReport.java
+++ b/src/main/java/net/minecraft/CrashReport.java
@@ -30,6 +30,7 @@ public class CrashReport {
     private final SystemReport systemReport = new SystemReport();
 
     public CrashReport(String message, Throwable cause) {
+        io.papermc.paper.util.StacktraceDeobfuscator.INSTANCE.deobfuscateThrowable(cause); // Paper
         this.title = message;
         this.exception = cause;
         this.systemReport.setDetail("CraftBukkit Information", new org.bukkit.craftbukkit.CraftCrashReport()); // CraftBukkit
diff --git a/src/main/java/net/minecraft/CrashReportCategory.java b/src/main/java/net/minecraft/CrashReportCategory.java
index 3941e14d1c3e6e688e28904948039c8b2200de5f..a4fda4a3bae9ce600e778b44cd3ef432a8b65667 100644
--- a/src/main/java/net/minecraft/CrashReportCategory.java
+++ b/src/main/java/net/minecraft/CrashReportCategory.java
@@ -104,6 +104,7 @@ public class CrashReportCategory {
         } else {
             this.stackTrace = new StackTraceElement[stackTraceElements.length - 3 - ignoredCallCount];
             System.arraycopy(stackTraceElements, 3 + ignoredCallCount, this.stackTrace, 0, this.stackTrace.length);
+            this.stackTrace = io.papermc.paper.util.StacktraceDeobfuscator.INSTANCE.deobfuscateStacktrace(this.stackTrace); // Paper
             return this.stackTrace.length;
         }
     }
diff --git a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
index a335d48467d1730bfed25eb5fd9046e115f23ed0..8098875a5c4146dec81f5daed0e34ddfe17a26c6 100644
--- a/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
+++ b/src/main/java/net/minecraft/server/dedicated/DedicatedServer.java
@@ -214,6 +214,7 @@ public class DedicatedServer extends MinecraftServer implements ServerInterface
         }
         com.destroystokyo.paper.PaperConfig.registerCommands();
         com.destroystokyo.paper.VersionHistoryManager.INSTANCE.getClass(); // load version history now
+        io.papermc.paper.util.ObfHelper.INSTANCE.getClass(); // load mappings for stacktrace deobf and etc.
         // Paper end
 
         this.setPvpAllowed(dedicatedserverproperties.pvp);
diff --git a/src/main/java/org/spigotmc/WatchdogThread.java b/src/main/java/org/spigotmc/WatchdogThread.java
index 4d271cae88c16ed2419f896c728fdff612540500..dcfbe77bdb25d9c58ffb7b75c48bdb580bc0de47 100644
--- a/src/main/java/org/spigotmc/WatchdogThread.java
+++ b/src/main/java/org/spigotmc/WatchdogThread.java
@@ -106,7 +106,7 @@ public class WatchdogThread extends Thread
                     log.log( Level.SEVERE, "During the run of the server, a plugin set an excessive velocity on an entity" );
                     log.log( Level.SEVERE, "This may be the cause of the issue, or it may be entirely unrelated" );
                     log.log( Level.SEVERE, org.bukkit.craftbukkit.CraftServer.excessiveVelEx.getMessage());
-                    for ( StackTraceElement stack : org.bukkit.craftbukkit.CraftServer.excessiveVelEx.getStackTrace() )
+                    for ( StackTraceElement stack : io.papermc.paper.util.StacktraceDeobfuscator.INSTANCE.deobfuscateStacktrace(org.bukkit.craftbukkit.CraftServer.excessiveVelEx.getStackTrace()) ) // Paper
                     {
                         log.log( Level.SEVERE, "\t\t" + stack );
                     }
@@ -194,7 +194,7 @@ public class WatchdogThread extends Thread
         }
         log.log( Level.SEVERE, "\tStack:" );
         //
-        for ( StackTraceElement stack : thread.getStackTrace() )
+        for ( StackTraceElement stack : io.papermc.paper.util.StacktraceDeobfuscator.INSTANCE.deobfuscateStacktrace(thread.getStackTrace()) ) // Paper
         {
             log.log( Level.SEVERE, "\t\t" + stack );
         }
diff --git a/src/main/resources/log4j2.xml b/src/main/resources/log4j2.xml
index d285dbec16272db6b8a71865e05924ad66087407..1a05d23ff886b015fb9396f119822c678a47ec6f 100644
--- a/src/main/resources/log4j2.xml
+++ b/src/main/resources/log4j2.xml
@@ -30,10 +30,14 @@
             <DefaultRolloverStrategy max="1000"/>
         </RollingRandomAccessFile>
         <Async name="Async">
+            <AppenderRef ref="rewrite"/>
+        </Async>
+        <Rewrite name="rewrite">
+            <StacktraceDeobfuscatingRewritePolicy />
             <AppenderRef ref="File"/>
             <AppenderRef ref="TerminalConsole" level="info"/>
             <AppenderRef ref="ServerGuiConsole" level="info"/>
-        </Async>
+        </Rewrite>
     </Appenders>
     <Loggers>
         <Root level="info">