rspec/rules/S4212/csharp/rule.adoc

Because serialization constructors allocate and initialize objects, security checks that are present on regular constructors must also be present on a serialization constructor. Failure to do so would allow callers that could not otherwise create an instance to use the serialization constructor to do this.


This rule raises an issue when a type implements the ``++System.Runtime.Serialization.ISerializable++`` interface, is not a delegate or interface, is declared in an assembly that allows partially trusted callers and has a constructor that takes a ``++System.Runtime.Serialization.SerializationInfo++`` object and a ``++System.Runtime.Serialization.StreamingContext++`` object which is not secured by a security check, but one or more of the regular constructors in the type is secured.


== Noncompliant Code Example

[source,csharp]
----
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Security;
using System.Security.Permissions;

[assembly: AllowPartiallyTrustedCallersAttribute()]
namespace MyLibrary
{
    [Serializable]
    public class Foo : ISerializable
    {
        private int n;

        [FileIOPermissionAttribute(SecurityAction.Demand, Unrestricted = true)]
        public Foo()
        {
           n = -1;
        }

        protected Foo(SerializationInfo info, StreamingContext context) // Noncompliant
        {
           n = (int)info.GetValue("n", typeof(int));
        }

        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
        {
           info.AddValue("n", n);
        }
    }
}
----


== Compliant Solution

[source,csharp]
----
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Security;
using System.Security.Permissions;

[assembly: AllowPartiallyTrustedCallersAttribute()]
namespace MyLibrary
{
    [Serializable]
    public class Foo : ISerializable
    {
        private int n;

        [FileIOPermissionAttribute(SecurityAction.Demand, Unrestricted = true)]
        public Foo()
        {
           n = -1;
        }

        [FileIOPermissionAttribute(SecurityAction.Demand, Unrestricted = true)]
        protected Foo(SerializationInfo info, StreamingContext context)
        {
           n = (int)info.GetValue("n", typeof(int));
        }

        void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context)
        {
           info.AddValue("n", n);
        }
    }
}
----


== See

* https://owasp.org/Top10/A08_2021-Software_and_Data_Integrity_Failures/[OWASP Top 10 2021 Category A8] - Software and Data Integrity Failures
* https://owasp.org/www-project-top-ten/2017/A8_2017-Insecure_Deserialization[OWASP Top 10 2017 Category A8] - Insecure Deserialization 


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