Do not allow third parties to provide Netty's native libraries (netty…

…#11856)

Throw an exception when there are multiple netty-tcnative-** libraries with the same path in the classpath

Motivation:

Currently Netty loads the first resource in the classpath with a given name.
It seems there are [libraries](netty/netty-tcnative#681 (comment)) which provide Netty's native libraries themselves.

Modification:

From now on Netty will look for all resources with the given name and throw an exception if there are more than one.
The user application needs to make sure that there is at most one provider of Netty's native libraties (netty-tcnative-**)

Result:

Fixes netty/netty-tcnative#681.

common/src/main/java/io/netty/util/internal/NativeLibraryLoader.java

@@ -33,7 +33,9 @@
 import java.security.PrivilegedAction;
 import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.EnumSet;
+import java.util.Enumeration;
 import java.util.List;
 import java.util.Set;
 
@@ -94,6 +96,7 @@ public static void loadFirstAvailable(ClassLoader loader, String... names) {
         for (String name : names) {
             try {
                 load(name, loader);
+                logger.debug("Loaded library with name '{}'", name);
                 return;
             } catch (Throwable t) {
                 suppressed.add(t);
@@ -145,22 +148,13 @@ public static void load(String originalName, ClassLoader loader) {
         InputStream in = null;
         OutputStream out = null;
         File tmpFile = null;
-        URL url;
-        if (loader == null) {
-            url = ClassLoader.getSystemResource(path);
-        } else {
-            url = loader.getResource(path);
-        }
+        URL url = getResource(path, loader);
         try {
             if (url == null) {
                 if (PlatformDependent.isOsx()) {
                     String fileName = path.endsWith(".jnilib") ? NATIVE_RESOURCE_HOME + "lib" + name + ".dynlib" :
                             NATIVE_RESOURCE_HOME + "lib" + name + ".jnilib";
-                    if (loader == null) {
-                        url = ClassLoader.getSystemResource(fileName);
-                    } else {
-                        url = loader.getResource(fileName);
-                    }
+                    url = getResource(fileName, loader);
                     if (url == null) {
                         FileNotFoundException fnf = new FileNotFoundException(fileName);
                         ThrowableUtil.addSuppressedAndClear(fnf, suppressed);
@@ -236,6 +230,30 @@ public static void load(String originalName, ClassLoader loader) {
         }
     }
 
+    private static URL getResource(String path, ClassLoader loader) {
+        final Enumeration<URL> urls;
+        try {
+            if (loader == null) {
+                urls = ClassLoader.getSystemResources(path);
+            } else {
+                urls = loader.getResources(path);
+            }
+        } catch (IOException iox) {
+            throw new RuntimeException("An error occurred while getting the resources for " + path, iox);
+        }
+
+        List<URL> urlsList = Collections.list(urls);
+        int size = urlsList.size();
+        switch (size) {
+            case 0:
+                return null;
+            case 1:
+                return urlsList.get(0);
+            default:
+                throw new IllegalStateException("Multiple resources found for '" + path + "': " + urlsList);
+        }
+    }
+
     static void tryPatchShadedLibraryIdAndSign(File libraryFile, String originalName) {
         String newId = new String(generateUniqueId(originalName.length()), CharsetUtil.UTF_8);
         if (!tryExec("install_name_tool -id " + newId + " " + libraryFile.getAbsolutePath())) {
@@ -288,7 +306,7 @@ private static void loadLibrary(final ClassLoader loader, final String name, fin
         Throwable suppressed = null;
         try {
             try {
-                // Make sure the helper is belong to the target ClassLoader.
+                // Make sure the helper belongs to the target ClassLoader.
                 final Class<?> newHelper = tryToLoadClass(loader, NativeLibraryUtil.class);
                 loadLibraryByHelper(newHelper, name, absolute);
                 logger.debug("Successfully loaded the library {}", name);

common/src/test/java/io/netty/util/internal/NativeLibraryLoaderTest.java

@@ -16,17 +16,31 @@
 package io.netty.util.internal;
 
 import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.condition.EnabledIf;
+import org.junit.jupiter.api.condition.EnabledOnOs;
+import org.junit.jupiter.api.function.Executable;
 
+import java.io.File;
 import java.io.FileNotFoundException;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLClassLoader;
 import java.util.UUID;
 
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
+import static org.junit.jupiter.api.condition.OS.LINUX;
 
-public class NativeLibraryLoaderTest {
+class NativeLibraryLoaderTest {
+
+    private static final String OS_ARCH = System.getProperty("os.arch");
+    private boolean is_x86_64() {
+        return "x86_64".equals(OS_ARCH) || "amd64".equals(OS_ARCH);
+    }
 
     @Test
-    public void testFileNotFound() {
+    void testFileNotFound() {
         try {
             NativeLibraryLoader.load(UUID.randomUUID().toString(), NativeLibraryLoaderTest.class.getClassLoader());
             fail();
@@ -39,7 +53,7 @@ public void testFileNotFound() {
     }
 
     @Test
-    public void testFileNotFoundWithNullClassLoader() {
+    void testFileNotFoundWithNullClassLoader() {
         try {
             NativeLibraryLoader.load(UUID.randomUUID().toString(), null);
             fail();
@@ -51,6 +65,38 @@ public void testFileNotFoundWithNullClassLoader() {
         }
     }
 
+    @Test
+    @EnabledOnOs(LINUX)
+    @EnabledIf("is_x86_64")
+    void testMultipleResourcesInTheClassLoader() throws MalformedURLException {
+        URL url1 = new File("src/test/data/NativeLibraryLoader/1").toURI().toURL();
+        URL url2 = new File("src/test/data/NativeLibraryLoader/2").toURI().toURL();
+        final URLClassLoader loader = new URLClassLoader(new URL[] {url1, url2});
+        final String resourceName = "test1";
+
+        Exception ise = assertThrows(IllegalStateException.class, new Executable() {
+            @Override
+            public void execute() {
+                NativeLibraryLoader.load(resourceName, loader);
+            }
+        });
+        assertTrue(ise.getMessage()
+                    .contains("Multiple resources found for 'META-INF/native/lib" + resourceName + ".so'"));
+    }
+
+    @Test
+    @EnabledOnOs(LINUX)
+    @EnabledIf("is_x86_64")
+    void testSingleResourceInTheClassLoader() throws MalformedURLException {
+        URL url1 = new File("src/test/data/NativeLibraryLoader/1").toURI().toURL();
+        URL url2 = new File("src/test/data/NativeLibraryLoader/2").toURI().toURL();
+        URLClassLoader loader = new URLClassLoader(new URL[] {url1, url2});
+        String resourceName = "test2";
+
+        NativeLibraryLoader.load(resourceName, loader);
+        assertTrue(true);
+    }
+
     @SuppressJava6Requirement(reason = "uses Java 7+ Throwable#getSuppressed but is guarded by version checks")
     private static void verifySuppressedException(UnsatisfiedLinkError error,
             Class<?> expectedSuppressedExceptionClass) {