Fix vulnerability with whitelist-aware ObjectInputStream

Only a few specific classes are now allowed.

app/src/main/java/org/schabi/newpipe/settings/export/ImportExportManager.kt

@@ -8,7 +8,6 @@ import org.schabi.newpipe.streams.io.SharpOutputStream
 import org.schabi.newpipe.streams.io.StoredFileHelper
 import org.schabi.newpipe.util.ZipHelper
 import java.io.IOException
-import java.io.ObjectInputStream
 import java.io.ObjectOutputStream
 import java.util.zip.ZipOutputStream
 
@@ -78,7 +77,9 @@ class ImportExportManager(private val fileLocator: NewPipeFileLocator) {
         try {
             val preferenceEditor = preferences.edit()
 
-            ObjectInputStream(fileLocator.settings.inputStream()).use { input ->
+            PreferencesObjectInputStream(
+                fileLocator.settings.inputStream()
+            ).use { input ->
                 preferenceEditor.clear()
                 @Suppress("UNCHECKED_CAST")
                 val entries = input.readObject() as Map<String, *>

app/src/main/java/org/schabi/newpipe/settings/export/PreferencesObjectInputStream.java

@@ -0,0 +1,58 @@
+package org.schabi.newpipe.settings.export;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.ObjectInputStream;
+import java.io.ObjectStreamClass;
+import java.util.Set;
+
+/**
+ * An {@link ObjectInputStream} that only allows preferences-related types to be deserialized, to
+ * prevent injections. The only allowed types are: all primitive types, all boxed primitive types,
+ * null, strings. HashMap, HashSet and arrays of previously defined types are also allowed. Sources:
+ * <a href="https://wiki.sei.cmu.edu/confluence/display/java/SER00-J.+Enable+serialization+compatibility+during+class+evolution">
+ * cmu.edu
+ * </a>,
+ * <a href="https://cheatsheetseries.owasp.org/cheatsheets/Deserialization_Cheat_Sheet.html#harden-your-own-javaioobjectinputstream">
+ * OWASP cheatsheet
+ * </a>,
+ * <a href="https://commons.apache.org/proper/commons-io/apidocs/src-html/org/apache/commons/io/serialization/ValidatingObjectInputStream.html#line-118">
+ * Apache's {@code ValidatingObjectInputStream}
+ * </a>
+ */
+public class PreferencesObjectInputStream extends ObjectInputStream {
+
+    /**
+     * Primitive types, strings and other built-in types do not pass through resolveClass() but
+     * instead have a custom encoding; see
+     * <a href="https://docs.oracle.com/javase/6/docs/platform/serialization/spec/protocol.html#10152">
+     * official docs</a>.
+     */
+    private static final Set<String> CLASS_WHITELIST = Set.of(
+            "java.lang.Boolean",
+            "java.lang.Byte",
+            "java.lang.Character",
+            "java.lang.Short",
+            "java.lang.Integer",
+            "java.lang.Long",
+            "java.lang.Float",
+            "java.lang.Double",
+            "java.lang.Void",
+            "java.util.HashMap",
+            "java.util.HashSet"
+    );
+
+    public PreferencesObjectInputStream(final InputStream in) throws IOException {
+        super(in);
+    }
+
+    @Override
+    protected Class<?> resolveClass(final ObjectStreamClass desc)
+            throws ClassNotFoundException, IOException {
+        if (CLASS_WHITELIST.contains(desc.getName())) {
+            return super.resolveClass(desc);
+        } else {
+            throw new ClassNotFoundException("Class not allowed: " + desc.getName());
+        }
+    }
+}