Use Files.createTempFile(...) to ensure the file is created with proper permissions

Motivation:

File.createTempFile(String, String)` will create a temporary file in the system temporary directory if the 'java.io.tmpdir'. The permissions on that file utilize the umask. In a majority of cases, this means that the file that java creates has the permissions: `-rw-r--r--`, thus, any other local user on that system can read the contents of that file.
This can be a security concern if any sensitive data is stored in this file.

This was reported by Jonathan Leitschuh <jonathan.leitschuh@gmail.com> as a security problem.

Modifications:

Use Files.createTempFile(...) which will use safe-defaults when running on java 7 and later. If running on java 6 there isnt much we can do, which is fair enough as java 6 shouldnt be considered "safe" anyway.

Result:

Create temporary files with sane permissions by default.

buffer/src/test/java/io/netty/buffer/AbstractByteBufTest.java

@@ -18,6 +18,7 @@ package io.netty.buffer;
 import io.netty.util.ByteProcessor;
 import io.netty.util.CharsetUtil;
 import io.netty.util.IllegalReferenceCountException;
+import io.netty.util.internal.PlatformDependent;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
@@ -4534,7 +4535,7 @@ public abstract class AbstractByteBufTest {
 
     @Test
     public void testReadBytesAndWriteBytesWithFileChannel() throws IOException {
-        File file = File.createTempFile("file-channel", ".tmp");
+        File file = PlatformDependent.createTempFile("file-channel", ".tmp", null);
         RandomAccessFile randomAccessFile = null;
         try {
             randomAccessFile = new RandomAccessFile(file, "rw");
@@ -4573,7 +4574,7 @@ public abstract class AbstractByteBufTest {
 
     @Test
     public void testGetBytesAndSetBytesWithFileChannel() throws IOException {
-        File file = File.createTempFile("file-channel", ".tmp");
+        File file = PlatformDependent.createTempFile("file-channel", ".tmp", null);
         RandomAccessFile randomAccessFile = null;
         try {
             randomAccessFile = new RandomAccessFile(file, "rw");

buffer/src/test/java/io/netty/buffer/ReadOnlyDirectByteBufferBufTest.java

@@ -15,6 +15,7 @@
  */
 package io.netty.buffer;
 
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -306,7 +307,7 @@ public class ReadOnlyDirectByteBufferBufTest {
 
     @Test
     public void testWrapMemoryMapped() throws Exception {
-        File file = File.createTempFile("netty-test", "tmp");
+        File file = PlatformDependent.createTempFile("netty-test", "tmp", null);
         FileChannel output = null;
         FileChannel input = null;
         ByteBuf b1 = null;

codec-http/src/main/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpData.java

@@ -18,6 +18,7 @@ package io.netty.handler.codec.http.multipart;
 import io.netty.buffer.ByteBuf;
 import io.netty.handler.codec.http.HttpConstants;
 import io.netty.util.internal.EmptyArrays;
+import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
 
@@ -89,9 +90,9 @@ public abstract class AbstractDiskHttpData extends AbstractHttpData {
         File tmpFile;
         if (getBaseDirectory() == null) {
             // create a temporary file
-            tmpFile = File.createTempFile(getPrefix(), newpostfix);
+            tmpFile = PlatformDependent.createTempFile(getPrefix(), newpostfix, null);
         } else {
-            tmpFile = File.createTempFile(getPrefix(), newpostfix, new File(
+            tmpFile = PlatformDependent.createTempFile(getPrefix(), newpostfix, new File(
                     getBaseDirectory()));
         }
         if (deleteOnExit()) {

codec-http/src/test/java/io/netty/handler/codec/http/HttpChunkedInputTest.java

@@ -25,6 +25,7 @@ import io.netty.handler.stream.ChunkedNioFile;
 import io.netty.handler.stream.ChunkedNioStream;
 import io.netty.handler.stream.ChunkedStream;
 import io.netty.handler.stream.ChunkedWriteHandler;
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Test;
 
 import java.io.ByteArrayInputStream;
@@ -46,7 +47,7 @@ public class HttpChunkedInputTest {
 
         FileOutputStream out = null;
         try {
-            TMP = File.createTempFile("netty-chunk-", ".tmp");
+            TMP = PlatformDependent.createTempFile("netty-chunk-", ".tmp", null);
             TMP.deleteOnExit();
             out = new FileOutputStream(TMP);
             out.write(BYTES);

codec-http/src/test/java/io/netty/handler/codec/http/multipart/AbstractDiskHttpDataTest.java

@@ -17,6 +17,7 @@ package io.netty.handler.codec.http.multipart;
 
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufUtil;
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Test;
 
 import java.io.File;
@@ -39,7 +40,7 @@ public class AbstractDiskHttpDataTest {
     public void testGetChunk() throws Exception {
         TestHttpData test = new TestHttpData("test", UTF_8, 0);
         try {
-            File tmpFile = File.createTempFile(UUID.randomUUID().toString(), ".tmp");
+            File tmpFile = PlatformDependent.createTempFile(UUID.randomUUID().toString(), ".tmp", null);
             tmpFile.deleteOnExit();
             FileOutputStream fos = new FileOutputStream(tmpFile);
             byte[] bytes = new byte[4096];

codec-http/src/test/java/io/netty/handler/codec/http/multipart/AbstractMemoryHttpDataTest.java

@@ -20,6 +20,7 @@ import io.netty.buffer.ByteBufInputStream;
 import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Test;
 
 import java.io.ByteArrayInputStream;
@@ -43,7 +44,7 @@ public class AbstractMemoryHttpDataTest {
     public void testSetContentFromFile() throws Exception {
         TestHttpData test = new TestHttpData("test", UTF_8, 0);
         try {
-            File tmpFile = File.createTempFile(UUID.randomUUID().toString(), ".tmp");
+            File tmpFile = PlatformDependent.createTempFile(UUID.randomUUID().toString(), ".tmp", null);
             tmpFile.deleteOnExit();
             FileOutputStream fos = new FileOutputStream(tmpFile);
             byte[] bytes = new byte[4096];
@@ -70,7 +71,7 @@ public class AbstractMemoryHttpDataTest {
     public void testRenameTo() throws Exception {
         TestHttpData test = new TestHttpData("test", UTF_8, 0);
         try {
-            File tmpFile = File.createTempFile(UUID.randomUUID().toString(), ".tmp");
+            File tmpFile = PlatformDependent.createTempFile(UUID.randomUUID().toString(), ".tmp", null);
             tmpFile.deleteOnExit();
             final int totalByteCount = 4096;
             byte[] bytes = new byte[totalByteCount];

codec-http/src/test/java/io/netty/handler/codec/http/multipart/DiskFileUploadTest.java

@@ -21,6 +21,7 @@ import io.netty.buffer.ByteBufUtil;
 import io.netty.buffer.Unpooled;
 import io.netty.util.CharsetUtil;
 
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Test;
 
 import java.io.File;
@@ -272,8 +273,9 @@ public class DiskFileUploadTest {
             assertEquals(maxSize, originalFile.length());
             assertEquals(maxSize, f1.length());
             byte[] bytes = new byte[8];
+
             ThreadLocalRandom.current().nextBytes(bytes);
-            File tmpFile = File.createTempFile(UUID.randomUUID().toString(), ".tmp");
+            File tmpFile = PlatformDependent.createTempFile(UUID.randomUUID().toString(), ".tmp", null);
             tmpFile.deleteOnExit();
             FileOutputStream fos = new FileOutputStream(tmpFile);
             try {

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

@@ -178,7 +178,7 @@ public final class NativeLibraryLoader {
             String prefix = libname.substring(0, index);
             String suffix = libname.substring(index);
 
-            tmpFile = File.createTempFile(prefix, suffix, WORKDIR);
+            tmpFile = PlatformDependent.createTempFile(prefix, suffix, WORKDIR);
             in = url.openStream();
             out = new FileOutputStream(tmpFile);
 

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

@@ -38,6 +38,7 @@ import java.lang.reflect.Field;
 import java.lang.reflect.Method;
 import java.nio.ByteBuffer;
 import java.nio.ByteOrder;
+import java.nio.file.Files;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.util.Arrays;
@@ -1288,6 +1289,24 @@ public final class PlatformDependent {
         return LINUX_OS_CLASSIFIERS;
     }
 
+    @SuppressJava6Requirement(reason = "Guarded by version check")
+    public static File createTempFile(String prefix, String suffix, File directory) throws IOException {
+        if (javaVersion() >= 7) {
+            if (directory == null) {
+                return Files.createTempFile(prefix, suffix).toFile();
+            }
+            return Files.createTempFile(directory.toPath(), prefix, suffix).toFile();
+        }
+        if (directory == null) {
+            return File.createTempFile(prefix, suffix);
+        }
+        File file = File.createTempFile(prefix, suffix, directory);
+        // Try to adjust the perms, if this fails there is not much else we can do...
+        file.setReadable(false, false);
+        file.setReadable(true, true);
+        return file;
+    }
+
     /**
      * Adds only those classifier strings to <tt>dest</tt> which are present in <tt>allowed</tt>.
      *

handler/src/main/java/io/netty/handler/ssl/util/SelfSignedCertificate.java

@@ -20,6 +20,7 @@ import io.netty.buffer.ByteBuf;
 import io.netty.buffer.Unpooled;
 import io.netty.handler.codec.base64.Base64;
 import io.netty.util.CharsetUtil;
+import io.netty.util.internal.PlatformDependent;
 import io.netty.util.internal.SystemPropertyUtil;
 import io.netty.util.internal.logging.InternalLogger;
 import io.netty.util.internal.logging.InternalLoggerFactory;
@@ -29,6 +30,7 @@ import java.io.FileInputStream;
 import java.io.FileOutputStream;
 import java.io.IOException;
 import java.io.OutputStream;
+import java.nio.file.Files;
 import java.security.KeyPair;
 import java.security.KeyPairGenerator;
 import java.security.NoSuchAlgorithmException;
@@ -320,7 +322,7 @@ public final class SelfSignedCertificate {
             wrappedBuf.release();
         }
 
-        File keyFile = File.createTempFile("keyutil_" + fqdn + '_', ".key");
+        File keyFile = PlatformDependent.createTempFile("keyutil_" + fqdn + '_', ".key", null);
         keyFile.deleteOnExit();
 
         OutputStream keyOut = new FileOutputStream(keyFile);
@@ -351,7 +353,7 @@ public final class SelfSignedCertificate {
             wrappedBuf.release();
         }
 
-        File certFile = File.createTempFile("keyutil_" + fqdn + '_', ".crt");
+        File certFile = PlatformDependent.createTempFile("keyutil_" + fqdn + '_', ".crt", null);
         certFile.deleteOnExit();
 
         OutputStream certOut = new FileOutputStream(certFile);

handler/src/test/java/io/netty/handler/stream/ChunkedWriteHandlerTest.java

@@ -26,6 +26,7 @@ import io.netty.channel.ChannelPromise;
 import io.netty.channel.embedded.EmbeddedChannel;
 import io.netty.util.CharsetUtil;
 import io.netty.util.ReferenceCountUtil;
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Assert;
 import org.junit.Test;
 
@@ -55,7 +56,7 @@ public class ChunkedWriteHandlerTest {
 
         FileOutputStream out = null;
         try {
-            TMP = File.createTempFile("netty-chunk-", ".tmp");
+            TMP = PlatformDependent.createTempFile("netty-chunk-", ".tmp", null);
             TMP.deleteOnExit();
             out = new FileOutputStream(TMP);
             out.write(BYTES);

handler/src/test/java/io/netty/handler/traffic/FileRegionThrottleTest.java

@@ -33,6 +33,7 @@ import io.netty.channel.socket.nio.NioServerSocketChannel;
 import io.netty.channel.socket.nio.NioSocketChannel;
 import io.netty.handler.codec.LineBasedFrameDecoder;
 import io.netty.util.CharsetUtil;
+import io.netty.util.internal.PlatformDependent;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.BeforeClass;
@@ -62,7 +63,7 @@ public class FileRegionThrottleTest {
             BYTES[i] = (byte) r.nextInt(255);
         }
 
-        tmp = File.createTempFile("netty-traffic", ".tmp");
+        tmp = PlatformDependent.createTempFile("netty-traffic", ".tmp", null);
         tmp.deleteOnExit();
         try (FileOutputStream out = new FileOutputStream(tmp)) {
             out.write(BYTES);

testsuite/src/main/java/io/netty/testsuite/transport/socket/SocketFileRegionTest.java

@@ -26,6 +26,7 @@ import io.netty.channel.ChannelOption;
 import io.netty.channel.DefaultFileRegion;
 import io.netty.channel.FileRegion;
 import io.netty.channel.SimpleChannelInboundHandler;
+import io.netty.util.internal.PlatformDependent;
 import org.hamcrest.CoreMatchers;
 import org.junit.Test;
 
@@ -101,7 +102,7 @@ public class SocketFileRegionTest extends AbstractSocketTest {
     }
 
     public void testFileRegionCountLargerThenFile(ServerBootstrap sb, Bootstrap cb) throws Throwable {
-        File file = File.createTempFile("netty-", ".tmp");
+        File file = PlatformDependent.createTempFile("netty-", ".tmp", null);
         file.deleteOnExit();
 
         final FileOutputStream out = new FileOutputStream(file);
@@ -135,7 +136,7 @@ public class SocketFileRegionTest extends AbstractSocketTest {
         cb.option(ChannelOption.AUTO_READ, autoRead);
 
         final int bufferSize = 1024;
-        final File file = File.createTempFile("netty-", ".tmp");
+        final File file = PlatformDependent.createTempFile("netty-", ".tmp", null);
         file.deleteOnExit();
 
         final FileOutputStream out = new FileOutputStream(file);

transport-native-unix-common-tests/src/main/java/io/netty/channel/unix/tests/UnixTestUtils.java

@@ -17,6 +17,7 @@ package io.netty.channel.unix.tests;
 
 import io.netty.channel.unix.DomainSocketAddress;
 import io.netty.channel.unix.Socket;
+import io.netty.util.internal.PlatformDependent;
 
 import java.io.File;
 import java.io.IOException;
@@ -26,7 +27,7 @@ public final class UnixTestUtils {
         try {
             File file;
             do {
-                file = File.createTempFile("NETTY", "UDS");
+                file = PlatformDependent.createTempFile("NETTY", "UDS", null);
                 if (!file.delete()) {
                     throw new IOException("failed to delete: " + file);
                 }

transport/src/test/java/io/netty/channel/DefaultFileRegionTest.java

@@ -15,6 +15,7 @@
  */
 package io.netty.channel;
 
+import io.netty.util.internal.PlatformDependent;
 import org.junit.Test;
 
 import java.io.ByteArrayOutputStream;
@@ -39,7 +40,7 @@ public class DefaultFileRegionTest {
     }
 
     private static File newFile() throws IOException {
-        File file = File.createTempFile("netty-", ".tmp");
+        File file = PlatformDependent.createTempFile("netty-", ".tmp", null);
         file.deleteOnExit();
 
         final FileOutputStream out = new FileOutputStream(file);