CA2311: Do not deserialize without first setting NetDataContractSerializer.Binder

Article
11/14/2023

Property	Value
Rule ID	CA2311
Title	Do not deserialize without first setting NetDataContractSerializer.Binder
Category	Security
Fix is breaking or non-breaking	Non-breaking
Enabled by default in .NET 8	No

Cause

A System.Runtime.Serialization.NetDataContractSerializer deserialization method was called or referenced without the Binder property set.

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

Warning

Restricting types with a SerializationBinder can't prevent all attacks. For more information, see the BinaryFormatter security guide.

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.Runtime.Serialization.NetDataContractSerializer deserialization method calls or references, when NetDataContractSerializer doesn't have its Binder set. If you want to disallow any deserialization with NetDataContractSerializer regardless of the Binder property, disable this rule and CA2312, and enable rule CA2310.

How to fix violations

Use a secure serializer instead, and don't allow an attacker to specify an arbitrary type to deserialize. For more information see the Preferred alternatives.
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.
This option makes code vulnerable to denial of service attacks and possible remote code execution attacks in the future. For more information, see the BinaryFormatter security guide. Restrict deserialized types. Implement a custom System.Runtime.Serialization.SerializationBinder. Before deserializing, set the Binder property to an instance of your custom SerializationBinder in all code paths. In the overridden BindToType method, if the type is unexpected, throw an exception to stop deserialization.

When to suppress warnings

NetDataContractSerializer is insecure and can't be made secure.

Configure code to analyze

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

Exclude specific symbols
Exclude specific types and their derived types

You can configure these options for just this rule, for all rules it applies to, or for all rules in this category (Security) that it applies 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. 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:

dotnet_code_quality.CAXXXX.excluded_symbol_names = MyType

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. 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:

dotnet_code_quality.CAXXXX.excluded_type_names_with_derived_types = MyType

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

using System;
using System.IO;
using System.Runtime.Serialization;

[DataContract]
public class BookRecord
{
    [DataMember]
    public string Title { get; set; }

    [DataMember]
    public AisleLocation Location { get; set; }
}

[DataContract]
public class AisleLocation
{
    [DataMember]
    public char Aisle { get; set; }

    [DataMember]
    public byte Shelf { get; set; }
}

public class ExampleClass
{
    public BookRecord DeserializeBookRecord(byte[] bytes)
    {
        NetDataContractSerializer serializer = new NetDataContractSerializer();
        using (MemoryStream ms = new MemoryStream(bytes))
        {
            return (BookRecord) serializer.Deserialize(ms);    // CA2311 violation
        }
    }
}

Imports System
Imports System.IO
Imports System.Runtime.Serialization

<DataContract()>
Public Class BookRecord
    <DataMember()>
    Public Property Title As String

    <DataMember()>
    Public Property Location As AisleLocation
End Class

<DataContract()>
Public Class AisleLocation
    <DataMember()>
    Public Property Aisle As Char

    <DataMember()>
    Public Property Shelf As Byte
End Class

Public Class ExampleClass
    Public Function DeserializeBookRecord(bytes As Byte()) As BookRecord
        Dim serializer As NetDataContractSerializer = New NetDataContractSerializer()
        Using ms As MemoryStream = New MemoryStream(bytes)
            Return CType(serializer.Deserialize(ms), BookRecord)    ' CA2311 violation
        End Using
    End Function
End Class

Solution

using System;
using System.IO;
using System.Runtime.Serialization;

public class BookRecordSerializationBinder : SerializationBinder
{
    public override Type BindToType(string assemblyName, string typeName)
    {
        // One way to discover expected types is through testing deserialization
        // of **valid** data and logging the types used.

        ////Console.WriteLine($"BindToType('{assemblyName}', '{typeName}')");

        if (typeName == "BookRecord")
        {
            return typeof(BookRecord);
        }
        else if (typeName == "AisleLocation")
        {
            return typeof(AisleLocation);
        }
        else
        {
            throw new ArgumentException("Unexpected type", nameof(typeName));
        }
    }
}

[DataContract]
public class BookRecord
{
    [DataMember]
    public string Title { get; set; }

    [DataMember]
    public AisleLocation Location { get; set; }
}

[DataContract]
public class AisleLocation
{
    [DataMember]
    public char Aisle { get; set; }

    [DataMember]
    public byte Shelf { get; set; }
}

public class ExampleClass
{
    public BookRecord DeserializeBookRecord(byte[] bytes)
    {
        NetDataContractSerializer serializer = new NetDataContractSerializer();
        serializer.Binder = new BookRecordSerializationBinder();
        using (MemoryStream ms = new MemoryStream(bytes))
        {
            return (BookRecord) serializer.Deserialize(ms);
        }
    }
}

Imports System
Imports System.IO
Imports System.Runtime.Serialization

Public Class BookRecordSerializationBinder
    Inherits SerializationBinder

    Public Overrides Function BindToType(assemblyName As String, typeName As String) As Type
        ' One way to discover expected types is through testing deserialization
        ' of **valid** data and logging the types used.

        'Console.WriteLine($"BindToType('{assemblyName}', '{typeName}')")

        If typeName = "BinaryFormatterVB.BookRecord" Then
            Return GetType(BookRecord)
        Else If typeName = "BinaryFormatterVB.AisleLocation" Then
            Return GetType(AisleLocation)
        Else
            Throw New ArgumentException("Unexpected type", NameOf(typeName))
        End If
    End Function
End Class

<DataContract()>
Public Class BookRecord
    <DataMember()>
    Public Property Title As String

    <DataMember()>
    Public Property Location As AisleLocation
End Class

<DataContract()>
Public Class AisleLocation
    <DataMember()>
    Public Property Aisle As Char

    <DataMember()>
    Public Property Shelf As Byte
End Class

Public Class ExampleClass
    Public Function DeserializeBookRecord(bytes As Byte()) As BookRecord
        Dim serializer As NetDataContractSerializer = New NetDataContractSerializer()
        serializer.Binder = New BookRecordSerializationBinder()
        Using ms As MemoryStream = New MemoryStream(bytes)
            Return CType(serializer.Deserialize(ms), BookRecord)
        End Using
    End Function
End Class

CA2310: Do not use insecure deserializer NetDataContractSerializer

CA2312: Ensure NetDataContractSerializer.Binder is set before deserializing

CA2311: Do not deserialize without first setting NetDataContractSerializer.Binder

Cause

Rule description

How to fix violations

When to suppress warnings

Configure code to analyze

Exclude specific symbols

Exclude specific types and their derived types

Pseudo-code examples

Violation

Solution

Feedback

Additional resources

CA2311: Do not deserialize without first setting NetDataContractSerializer.Binder

Cause

Rule description

How to fix violations

When to suppress warnings

Configure code to analyze

Exclude specific symbols

Exclude specific types and their derived types

Pseudo-code examples

Violation

Solution

Related rules

Feedback

Additional resources