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This compliant solution is based on http://www.ibm.com/developerworks/library/se-lookahead/. It inspects the class of any object being deserialized, before its readObject() method is invoked. The code consequently throws an InvalidClassException unless the class of the object (and of all sub-objects) is either a GoodClass1 or a GoodClass2. The WhitelistedObjectInputStream class here is compatible with the strategy employed by the compliant solution in SEC58-J. Deserialization methods should not perform potentially dangerous operations.
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import java.io.*;
import java.util.*;
class WhitelistedObjectInputStream extends ObjectInputStream {
public Set whitelist;
public WhitelistedObjectInputStream(InputStream inputStream, Set wl) throws IOException {
super(inputStream);
whitelist = wl;
}
@Override
protected Class<?> resolveClass(ObjectStreamClass cls) throws IOException, ClassNotFoundException {
if (!whitelist.contains(cls.getName())) {
throw new InvalidClassException("Unexpected serialized class", cls.getName());
}
return super.resolveClass(cls);
}
}
class DeserializeExample {
private static Object deserialize(byte[] buffer) throws IOException, ClassNotFoundException {
Object ret = null;
Set whitelist = new HashSet<String>(Arrays.asList(new String[]{"GoodClass1","GoodClass2"}));
try (ByteArrayInputStream bais = new ByteArrayInputStream(buffer)) {
try (WhitelistedObjectInputStream ois = new WhitelistedObjectInputStream(bais, whitelist)) {
ret = ois.readObject();
}
}
return ret;
}
} |
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