Improved class entry validation (#1260)

* Improved class entry validation

* Fixes and tests

gradle/test.libs.versions.toml

@@ -6,7 +6,7 @@ mockito = "5.14.2"
 java-debug = "0.52.0"
 mixin = "0.15.3+mixin.0.8.7"
 
-gradle-nightly = "8.13-20250125001926+0000"
+gradle-nightly = "8.14-20250208001853+0000"
 fabric-loader = "0.16.9"
 
 [libraries]

src/main/java/net/fabricmc/loom/decompilers/cache/ClassEntry.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2024 FabricMC
+ * Copyright (c) 2024-2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -45,6 +45,34 @@ import net.fabricmc.loom.util.Checksum;
 public record ClassEntry(String name, List<String> innerClasses, List<String> superClasses) {
 	private static final Logger LOGGER = LoggerFactory.getLogger(ClassEntry.class);
 
+	public ClassEntry {
+		if (!name.endsWith(".class")) {
+			throw new IllegalArgumentException("Class name must end with '.class': " + name);
+		}
+
+		if (!name.contains("/")) {
+			throw new IllegalArgumentException("Class name must be in a package: " + name);
+		}
+
+		String className = name.replace(".class", "");
+
+		for (String innerClass : innerClasses) {
+			if (!innerClass.endsWith(".class")) {
+				throw new IllegalArgumentException("Inner class name must end with '.class': " + name);
+			}
+
+			if (!innerClass.startsWith(className)) {
+				throw new IllegalArgumentException("Inner class (" + innerClass + ") does not have the parent class name as a prefix: " + name);
+			}
+		}
+
+		for (String superClass : superClasses) {
+			if (!superClass.endsWith(".class")) {
+				throw new IllegalArgumentException("Super class name must end with '.class': " + superClass);
+			}
+		}
+	}
+
 	/**
 	 * Copy the class and its inner classes to the target root.
 	 * @param sourceRoot The root of the source jar
@@ -55,13 +83,18 @@ public record ClassEntry(String name, List<String> innerClasses, List<String> su
 	public void copyTo(Path sourceRoot, Path targetRoot) throws IOException {
 		Path targetPath = targetRoot.resolve(name);
 		Files.createDirectories(targetPath.getParent());
-		Files.copy(sourceRoot.resolve(name), targetPath);
+		copy(sourceRoot.resolve(name), targetPath);
 
 		for (String innerClass : innerClasses) {
-			Files.copy(sourceRoot.resolve(innerClass), targetRoot.resolve(innerClass));
+			copy(sourceRoot.resolve(innerClass), targetRoot.resolve(innerClass));
 		}
 	}
 
+	private void copy(Path source, Path target) throws IOException {
+		LOGGER.debug("Copying class entry `{}` from `{}` to `{}`", name, source, target);
+		Files.copy(source, target);
+	}
+
 	/**
 	 * Hash the class and its inner classes using sha256.
 	 * @param root The root of the jar
@@ -95,7 +128,7 @@ public record ClassEntry(String name, List<String> innerClasses, List<String> su
 		joiner.add(selfHash);
 
 		for (String superClass : superClasses) {
-			final String superHash = hashes.get(superClass + ".class");
+			final String superHash = hashes.get(superClass);
 
 			if (superHash != null) {
 				joiner.add(superHash);

src/main/java/net/fabricmc/loom/decompilers/cache/JarWalker.java

@@ -1,7 +1,7 @@
 /*
  * This file is part of fabric-loom, licensed under the MIT License (MIT).
  *
- * Copyright (c) 2024 FabricMC
+ * Copyright (c) 2024-2025 FabricMC
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -194,11 +194,14 @@ public final class JarWalker {
 			List<String> parentClasses = new ArrayList<>();
 			String superName = reader.getSuperName();
 
-			if (superName != null) {
-				parentClasses.add(superName);
+			if (superName != null && !superName.equals("java/lang/Object")) {
+				parentClasses.add(superName + ".class");
+			}
+
+			for (String iface : reader.getInterfaces()) {
+				parentClasses.add(iface + ".class");
 			}
 
-			Collections.addAll(parentClasses, reader.getInterfaces());
 			return Collections.unmodifiableList(parentClasses);
 		} catch (IOException e) {
 			throw new UncheckedIOException("Failed to read class file: " + classFile, e);

src/test/groovy/net/fabricmc/loom/test/unit/cache/ClassEntryTest.groovy

@@ -0,0 +1,63 @@
+/*
+ * This file is part of fabric-loom, licensed under the MIT License (MIT).
+ *
+ * Copyright (c) 2025 FabricMC
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+package net.fabricmc.loom.test.unit.cache
+
+import spock.lang.Specification
+
+import net.fabricmc.loom.decompilers.cache.ClassEntry
+
+class ClassEntryTest extends Specification {
+	def "valid class entry"() {
+		when:
+		def classEntry = new ClassEntry(name, innerClasses, superClasses)
+		then:
+		// Just make sure the constructor doesn't throw an exception
+		classEntry != null
+		where:
+		name | innerClasses | superClasses
+		"net/fabricmc/Test.class" | [] | []
+		"net/fabricmc/Test.class" | [
+			"net/fabricmc/Test\$Inner.class"
+		] | ["java/lang/List.class"]
+	}
+
+	def "invalid class entry"() {
+		when:
+		new ClassEntry(name, innerClasses, superClasses)
+		then:
+		thrown IllegalArgumentException
+		where:
+		name | innerClasses | superClasses
+		"net/fabricmc/Test" | [] | []
+		"net/fabricmc/Test.class" | ["net/fabricmc/Test\$Inner"] | ["java/lang/List.class"]
+		"net/fabricmc/Test.class" | [
+			"net/fabricmc/Test\$Inner.class"
+		] | ["java/lang/List"]
+		"net/fabricmc/Test.class" | ["net/Test\$Inner.class"] | ["java/lang/List.class"]
+		"net/fabricmc/Test.class" | [
+			"net/fabricmc/Bar\$Inner.class"
+		] | []
+	}
+}

src/test/groovy/net/fabricmc/loom/test/unit/cache/JarWalkerTest.groovy

@@ -123,7 +123,7 @@ class JarWalkerTest extends Specification {
 		classes.size() == 1
 		classes[0].name() == "net/fabricmc/Example.class"
 		classes[0].innerClasses() == []
-		classes[0].superClasses() == ["java/lang/Runnable"]
+		classes[0].superClasses() == ["java/lang/Runnable.class"]
 	}
 
 	def "inner classes"() {
@@ -146,8 +146,8 @@ class JarWalkerTest extends Specification {
 			"net/fabricmc/other/Test\$Inner.class"
 		]
 		classes[0].superClasses() == [
-			"java/lang/Runnable",
-			"net/fabricmc/other/Super"
+			"java/lang/Runnable.class",
+			"net/fabricmc/other/Super.class"
 		]
 	}