A System.Runtime.Serialization.Formatters.Binary.BinaryFormatter deserialization method was called or referenced without the Binder property set.
By default, this rule analyzes the entire codebase, but this is configurable.
Rule descriptionInsecure 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.Formatters.Binary.BinaryFormatter deserialization method calls or references, when BinaryFormatter doesn't have its Binder set. If you want to disallow any deserialization with BinaryFormatter regardless of the Binder property, disable this rule and CA2302, and enable rule CA2300.
How to fix violationsBinder
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.BinaryFormatter
is insecure and can't be made secure.
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 symbolsYou 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:
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 |
):
M:
for methods, T:
for types, and N:
for namespaces..ctor
for constructors and .cctor
for static constructors.Examples:
Option Value Summarydotnet_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:
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 |
):
T:
prefix.Examples:
Option value Summarydotnet_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.Formatters.Binary;
[Serializable]
public class BookRecord
{
public string Title { get; set; }
public AisleLocation Location { get; set; }
}
[Serializable]
public class AisleLocation
{
public char Aisle { get; set; }
public byte Shelf { get; set; }
}
public class ExampleClass
{
public BookRecord DeserializeBookRecord(byte[] bytes)
{
BinaryFormatter formatter = new BinaryFormatter();
using (MemoryStream ms = new MemoryStream(bytes))
{
return (BookRecord) formatter.Deserialize(ms);
}
}
}
Imports System
Imports System.IO
Imports System.Runtime.Serialization.Formatters.Binary
<Serializable()>
Public Class BookRecord
Public Property Title As String
Public Property Location As AisleLocation
End Class
<Serializable()>
Public Class AisleLocation
Public Property Aisle As Char
Public Property Shelf As Byte
End Class
Public Class ExampleClass
Public Function DeserializeBookRecord(bytes As Byte()) As BookRecord
Dim formatter As BinaryFormatter = New BinaryFormatter()
Using ms As MemoryStream = New MemoryStream(bytes)
Return CType(formatter.Deserialize(ms), BookRecord)
End Using
End Function
End Class
Solution
using System;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
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($"BindToType('{assemblyName}', '{typeName}')");
if (typeName == "BookRecord")
{
return typeof(BookRecord);
}
else if (typeName == "AisleLocation")
{
return typeof(AisleLocation);
}
else
{
throw new ArgumentException("Unexpected type", nameof(typeName));
}
}
}
[Serializable]
public class BookRecord
{
public string Title { get; set; }
public AisleLocation Location { get; set; }
}
[Serializable]
public class AisleLocation
{
public char Aisle { get; set; }
public byte Shelf { get; set; }
}
public class ExampleClass
{
public BookRecord DeserializeBookRecord(byte[] bytes)
{
BinaryFormatter formatter = new BinaryFormatter();
formatter.Binder = new BookRecordSerializationBinder();
using (MemoryStream ms = new MemoryStream(bytes))
{
return (BookRecord) formatter.Deserialize(ms);
}
}
}
Imports System
Imports System.IO
Imports System.Runtime.Serialization
Imports System.Runtime.Serialization.Formatters.Binary
Public Class BookRecordSerializationBinder
Inherits SerializationBinder
Public Overrides Function BindToType(assemblyName As String, typeName As String) As Type
' One way to discover expected types is through testing deserialization
' of **valid** data and logging the types used.
'Console.WriteLine($"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
<Serializable()>
Public Class BookRecord
Public Property Title As String
Public Property Location As AisleLocation
End Class
<Serializable()>
Public Class AisleLocation
Public Property Aisle As Char
Public Property Shelf As Byte
End Class
Public Class ExampleClass
Public Function DeserializeBookRecord(bytes As Byte()) As BookRecord
Dim formatter As BinaryFormatter = New BinaryFormatter()
formatter.Binder = New BookRecordSerializationBinder()
Using ms As MemoryStream = New MemoryStream(bytes)
Return CType(formatter.Deserialize(ms), BookRecord)
End Using
End Function
End Class
CA2300: Do not use insecure deserializer BinaryFormatter
CA2302: Ensure BinaryFormatter.Binder is set before calling BinaryFormatter.Deserialize
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