CA2321Security Enabled by default: No

Do not deserialize with JavaScriptSerializer using a SimpleTypeResolver

Description

This rule finds System.Web.Script.Serialization.JavaScriptSerializer deserialization method calls or references, after initializing the System.Web.Script.Serialization.JavaScriptSerializer with a System.Web.Script.Serialization.SimpleTypeResolver.

Cause

A System.Web.Script.Serialization.JavaScriptSerializer deserialization method was called or referenced after initializing with a System.Web.Script.Serialization.SimpleTypeResolver.

By default, this rule analyzes the entire codebase, but this is configurable.

How to fix violations

Don't initialize System.Web.Script.Serialization.JavaScriptTypeResolver with a System.Web.Script.Serialization.SimpleTypeResolver.
If your code needs to read data serialized using a System.Web.Script.Serialization.SimpleTypeResolver, restrict deserialized types to an expected list by implementing a custom System.Web.Script.Serialization.JavaScriptTypeResolver.
Make the serialized data tamper-proof. After serialization, cryptographically sign the serialized data. Before deserialization, validate the cryptographic signature. Protect the cryptographic key from being disclosed and design for key rotations.

Example

using System.Web.Script.Serialization;

public class ExampleClass
{
    public T Deserialize<T>(string str)
    {
        JavaScriptSerializer s = new JavaScriptSerializer(new SimpleTypeResolver());
        return s.Deserialize<T>(str);
    }
}

using System.Web.Script.Serialization;

public class ExampleClass
{
    public T Deserialize<T>(string str)
    {
        JavaScriptSerializer s = new JavaScriptSerializer();
        return s.Deserialize<T>(str);
    }
}

using System.Web.Script.Serialization;

public class BookRecord
{
    public string Title { get; set; }
    public string Author { get; set; }
    public int PageCount { get; set; }
    public AisleLocation Location { get; set; }
}

public class AisleLocation
{
    public char Aisle { get; set; }
    public byte Shelf { get; set; }
}

public class ExampleClass
{
    public BookRecord DeserializeBookRecord(string s)
    {
        JavaScriptSerializer serializer = new JavaScriptSerializer(new SimpleTypeResolver());
        return serializer.Deserialize<BookRecord>(s);
    }
}

using System;
using System.Web.Script.Serialization;

public class BookRecordTypeResolver : JavaScriptTypeResolver
{
    // For compatibility with data serialized with a JavaScriptSerializer initialized with SimpleTypeResolver.
    private static readonly SimpleTypeResolver Simple = new SimpleTypeResolver();

    public override Type ResolveType(string id)
    {
        // One way to discover expected types is through testing deserialization
        // of **valid** data and logging the types used.

        ////Console.WriteLine($"ResolveType('{id}')");

        if (id == typeof(BookRecord).AssemblyQualifiedName || id == typeof(AisleLocation).AssemblyQualifiedName)
        {
            return Simple.ResolveType(id);
        }
        else
        {
            throw new ArgumentException("Unexpected type ID", nameof(id));
        }
    }

    public override string ResolveTypeId(Type type)
    {
        return Simple.ResolveTypeId(type);
    }
}

public class BookRecord
{
    public string Title { get; set; }
    public string Author { get; set; }
    public int PageCount { get; set; }
    public AisleLocation Location { get; set; }
}

public class AisleLocation
{
    public char Aisle { get; set; }
    public byte Shelf { get; set; }
}

public class ExampleClass
{
    public BookRecord DeserializeBookRecord(string s)
    {
        JavaScriptSerializer serializer = new JavaScriptSerializer(new BookRecordTypeResolver());
        return serializer.Deserialize<BookRecord>(s);
    }
}

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