create pop3 and mbox message cache files with owner-only permissions

providers/mbox/src/main/java/org/eclipse/angus/mail/mbox/TempFile.java

@@ -23,6 +23,9 @@
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.io.RandomAccessFile;
+import java.nio.file.Files;
+import java.nio.file.attribute.FileAttribute;
+import java.nio.file.attribute.PosixFilePermissions;
 
 /**
  * A temporary file used to cache messages.
@@ -37,12 +40,34 @@ class TempFile {
      * The file will be deleted when the JVM exits.
      */
     public TempFile(File dir) throws IOException {
-        file = File.createTempFile("mbox.", ".mbox", dir);
-        // XXX - need JDK 6 to set permissions on the file to owner-only
+        file = createTempFile("mbox.", ".mbox", dir);
         file.deleteOnExit();
         sf = new WritableSharedFile(file);
     }
 
+    /**
+     * Create the cache file with owner-only permissions so that the
+     * cached message content isn't readable by other local users.  On
+     * file systems without POSIX permissions the platform default is
+     * used.
+     */
+    private static File createTempFile(String prefix, String suffix, File dir)
+            throws IOException {
+        try {
+            FileAttribute<?> attr = PosixFilePermissions.asFileAttribute(
+                    PosixFilePermissions.fromString("rw-------"));
+            if (dir != null)
+                return Files.createTempFile(
+                        dir.toPath(), prefix, suffix, attr).toFile();
+            return Files.createTempFile(prefix, suffix, attr).toFile();
+        } catch (UnsupportedOperationException ex) {
+            if (dir != null)
+                return Files.createTempFile(
+                        dir.toPath(), prefix, suffix).toFile();
+            return Files.createTempFile(prefix, suffix).toFile();
+        }
+    }
+
     /**
      * Return a stream for appending to the temp file.
      */

providers/mbox/src/test/java/org/eclipse/angus/mail/mbox/TempFileTest.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (c) 2009, 2024 Oracle and/or its affiliates. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0, which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * This Source Code may also be made available under the following Secondary
+ * Licenses when the conditions for such availability set forth in the
+ * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
+ * version 2 with the GNU Classpath Exception, which is available at
+ * https://www.gnu.org/software/classpath/license.html.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
+ */
+
+package org.eclipse.angus.mail.mbox;
+
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.TemporaryFolder;
+
+import java.io.File;
+import java.nio.file.FileSystems;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.attribute.PosixFilePermission;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assume.assumeTrue;
+
+/**
+ * Test that the message cache temp file is created owner-only.
+ */
+public final class TempFileTest {
+
+    @Rule
+    public final TemporaryFolder folder = new TemporaryFolder();
+
+    @Test
+    public void testCacheFileIsOwnerOnly() throws Exception {
+        assumeTrue("requires a POSIX file system",
+                FileSystems.getDefault().supportedFileAttributeViews()
+                        .contains("posix"));
+
+        File dir = folder.newFolder();
+        TempFile tf = new TempFile(dir);
+        try {
+            File[] created = dir.listFiles((d, n) ->
+                    n.startsWith("mbox.") && n.endsWith(".mbox"));
+            assertEquals(1, created.length);
+            Path p = created[0].toPath();
+            Set<PosixFilePermission> perms = Files.getPosixFilePermissions(p);
+            assertEquals("cache file must not be readable by group or others",
+                    Set.of(PosixFilePermission.OWNER_READ,
+                            PosixFilePermission.OWNER_WRITE),
+                    perms);
+        } finally {
+            tf.close();
+        }
+    }
+}

providers/pop3/src/main/java/org/eclipse/angus/mail/pop3/TempFile.java

@@ -18,6 +18,9 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.attribute.FileAttribute;
+import java.nio.file.attribute.PosixFilePermissions;
 
 /**
  * A temporary file used to cache POP3 messages.
@@ -32,12 +35,34 @@ class TempFile {
      * The file will be deleted when the JVM exits.
      */
     public TempFile(File dir) throws IOException {
-        file = File.createTempFile("pop3.", ".mbox", dir);
-        // XXX - need JDK 6 to set permissions on the file to owner-only
+        file = createTempFile("pop3.", ".mbox", dir);
         file.deleteOnExit();
         sf = new WritableSharedFile(file);
     }
 
+    /**
+     * Create the cache file with owner-only permissions so that the
+     * cached message content isn't readable by other local users.  On
+     * file systems without POSIX permissions the platform default is
+     * used.
+     */
+    private static File createTempFile(String prefix, String suffix, File dir)
+            throws IOException {
+        try {
+            FileAttribute<?> attr = PosixFilePermissions.asFileAttribute(
+                    PosixFilePermissions.fromString("rw-------"));
+            if (dir != null)
+                return Files.createTempFile(
+                        dir.toPath(), prefix, suffix, attr).toFile();
+            return Files.createTempFile(prefix, suffix, attr).toFile();
+        } catch (UnsupportedOperationException ex) {
+            if (dir != null)
+                return Files.createTempFile(
+                        dir.toPath(), prefix, suffix).toFile();
+            return Files.createTempFile(prefix, suffix).toFile();
+        }
+    }
+
     /**
      * Return a stream for appending to the temp file.
      */