CA5361: Do not disable SChannel use of strong crypto

Property	Value
Rule ID	CA5361
Title	Do not disable SChannel use of strong crypto
Category	Security
Fix is breaking or non-breaking	Non-breaking
Enabled by default in .NET 8	No

Cause

A AppContext.SetSwitch method call sets Switch.System.Net.DontEnableSchUseStrongCrypto to true.

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

Rule description

Setting Switch.System.Net.DontEnableSchUseStrongCrypto to true weakens the cryptography used in outgoing Transport Layer Security (TLS) connections. Weaker cryptography can compromise the confidentiality of communication between your application and the server, making it easier for attackers to eavesdrop sensitive data. For more information, see Transport Layer Security (TLS) best practices with .NET Framework.

How to fix violations

• If your application targets .NET Framework v4.6 or later, you can either remove the AppContext.SetSwitch method call, or set the switch's value to false.
• If your application targets .NET Framework earlier than v4.6 and runs on .NET Framework v4.6 or later, set the switch's value to false.
• Otherwise, refer to Transport Layer Security (TLS) best practices with .NET Framework for mitigations.

When to suppress warnings

You can suppress this warning if you need to connect to a legacy service that can't be upgraded to use secure TLS configurations.

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.

#pragma warning disable CA5361
// The code that's violating the rule is on this line.
#pragma warning restore CA5361

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

[*.{cs,vb}]
dotnet_diagnostic.CA5361.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.

• 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;

public class ExampleClass
{
    public void ExampleMethod()
    {
        // CA5361 violation
        AppContext.SetSwitch("Switch.System.Net.DontEnableSchUseStrongCrypto", true);
    }
}

Imports System

Public Class ExampleClass
    Public Sub ExampleMethod()
        ' CA5361 violation
        AppContext.SetSwitch("Switch.System.Net.DontEnableSchUseStrongCrypto", true)
    End Sub
End Class

Solution

using System;

public class ExampleClass
{
    public void ExampleMethod()
    {
        AppContext.SetSwitch("Switch.System.Net.DontEnableSchUseStrongCrypto", false);
    }
}

Imports System

Public Class ExampleClass
    Public Sub ExampleMethod()
        AppContext.SetSwitch("Switch.System.Net.DontEnableSchUseStrongCrypto", false)
    End Sub
End Class