Serialization and deserialization features can be exploited to bypass security manager checks. A serializable class may contain security manager checks in its constructors for various reasons, including preventing untrusted code from modifying the internal state of the class. Such security manager checks must be replicated wherever a class instance can be constructed. For example, if a class enables a caller to retrieve sensitive internal state contingent upon security checks, those checks must be replicated during deserialization to ensure that an attacker cannot extract sensitive information by deserializing the object.
Noncompliant Code Example
In this noncompliant code example, security manager checks are used within the constructor but are omitted from the
readObject() methods that are used in the serialization-deserialization process. This omission allows untrusted code to maliciously create instances of the class.
(Although there are security manager checks, the data in this example is not sensitive. Serializing unencrypted sensitive data violates SER03-J. Do not serialize unencrypted sensitive data.)
InvalidInputException are both security exceptions that can be thrown by any method without requiring a
This compliant solution implements the required security manager checks in all constructors and methods that can either modify or retrieve internal state. Consequently, an attacker cannot create a modified instance of the object (using deserialization) or read the serialized byte stream to reveal serialized data.
Refer to SEC04-J. Protect sensitive operations with security manager checks for information about implementing the
performSecurityManagerCheck() method, which is important for protection against finalizer attacks.
ObjectInputStream.defaultReadObject() fills the object's fields with data from the input stream. Because each field is deserialized recursively, it is possible for the
this reference to escape from control of the deserialization routines. This can happen if a referenced object publishes the
this reference in its constructors or field initializers (see TSM01-J. Do not let the this reference escape during object construction for more information). To be compliant, recursively deserialized subobjects must not publish the
this object reference.
Allowing serialization or deserialization to bypass the security manager may result in classes being constructed without required security checks.
|Enforce 'SecurityManager' checks in methods of 'Serializable' classes
Guideline 8-4 / SERIAL-4: Duplicate the SecurityManager checks enforced in a class during serialization and deserialization
Android Implementation Details
java.security package exists on Android for compatibility purposes only, and it should not be used.
Section 2.4, "Serialization"