Edit

Share via

CA2322: Ensure JavaScriptSerializer is not initialized with SimpleTypeResolver before deserializing

  • Article
Property Value
Rule ID CA2322
Title Ensure JavaScriptSerializer is not initialized with SimpleTypeResolver before deserializing
Category Security
Fix is breaking or non-breaking Non-breaking
Enabled by default in .NET 9 No

Cause

A System.Web.Script.Serialization.JavaScriptSerializer deserialization method was called or referenced and the JavaScriptSerializer may have been initialized with a System.Web.Script.Serialization.SimpleTypeResolver.

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

Rule description

Insecure deserializers are vulnerable when deserializing untrusted data. An attacker could modify the serialized data to include unexpected types to inject objects with malicious side effects. An attack against an insecure deserializer could, for example, execute commands on the underlying operating system, communicate over the network, or delete files.

This rule finds System.Web.Script.Serialization.JavaScriptSerializer deserialization method calls or references, when the JavaScriptSerializer may have been initialized with a System.Web.Script.Serialization.SimpleTypeResolver.

How to fix violations

When to suppress warnings

It's safe to suppress a warning from this rule if:

  • You know the input is trusted. Consider that your application's trust boundary and data flows may change over time.
  • You've taken one of the precautions in How to fix violations.

Suppress a warning

If you just want to suppress a single violation, add preprocessor directives to your source file to disable and then re-enable the rule.

C# 
#pragma warning disable CA2322
// The code that's violating the rule is on this line.
#pragma warning restore CA2322

To disable the rule for a file, folder, or project, set its severity to none in the configuration file.

ini 
[*.{cs,vb}]
dotnet_diagnostic.CA2322.severity = none

For more information, see How to suppress code analysis warnings.

Configure code to analyze

Use the following options to configure which parts of your codebase to run this rule on.

You can configure these options for just this rule, for all rules they apply to, or for all rules in this category (Security) that they apply to. For more information, see Code quality rule configuration options.

Exclude specific symbols

You can exclude specific symbols, such as types and methods, from analysis by setting the excluded_symbol_names option. For example, to specify that the rule should not run on any code within types named MyType, add the following key-value pair to an .editorconfig file in your project:

ini 
dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType

Note

Replace the XXXX part of CAXXXX with the ID of the applicable rule.

Allowed symbol name formats in the option value (separated by |):

  • Symbol name only (includes all symbols with the name, regardless of the containing type or namespace).
  • Fully qualified names in the symbol's documentation ID format. Each symbol name requires a symbol-kind prefix, such as M: for methods, T: for types, and N: for namespaces.
  • .ctor for constructors and .cctor for static constructors.

Examples:

Option Value Summary
dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType Matches all symbols named MyType.
dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType1|MyType2 Matches all symbols named either MyType1 or MyType2.
dotnet_code_quality.CAXXXX.excluded_symbol_names = M:NS.MyType.MyMethod(ParamType) Matches specific method MyMethod with the specified fully qualified signature.
dotnet_code_quality.CAXXXX.excluded_symbol_names = M:NS1.MyType1.MyMethod1(ParamType)|M:NS2.MyType2.MyMethod2(ParamType) Matches specific methods MyMethod1 and MyMethod2 with the respective fully qualified signatures.

Exclude specific types and their derived types

You can exclude specific types and their derived types from analysis by setting the excluded_type_names_with_derived_types option. For example, to specify that the rule should not run on any methods within types named MyType and their derived types, add the following key-value pair to an .editorconfig file in your project:

ini 
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType

Note

Replace the XXXX part of CAXXXX with the ID of the applicable rule.

Allowed symbol name formats in the option value (separated by |):

  • Type name only (includes all types with the name, regardless of the containing type or namespace).
  • Fully qualified names in the symbol's documentation ID format, with an optional T: prefix.

Examples:

Option value Summary
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType Matches all types named MyType and all of their derived types.
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType1|MyType2 Matches all types named either MyType1 or MyType2 and all of their derived types.
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = M:NS.MyType Matches specific type MyType with given fully qualified name and all of its derived types.
dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = M:NS1.MyType1|M:NS2.MyType2 Matches specific types MyType1 and MyType2 with the respective fully qualified names, and all of their derived types.

Pseudo-code examples

Violation 1

C# 
using System.Web.Script.Serialization;

public class ExampleClass
{
    public JavaScriptSerializer Serializer { get; set; }

    public T Deserialize<T>(string str)
    {
        return this.Serializer.Deserialize<T>(str);
    }
}

Solution 1

C# 
using System.Web.Script.Serialization;

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

Violation 2

C# 
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 JavaScriptSerializer Serializer { get; set; }

    public BookRecord DeserializeBookRecord(string s)
    {
        return this.Serializer.Deserialize<BookRecord>(s);
    }
}

Solution 2

C# 
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);
    }
}

CA2321: Do not deserialize with JavaScriptSerializer using a SimpleTypeResolver