CA5400: Ensure HttpClient certificate revocation list check is not disabled

#Cause

Using System.Net.Http.HttpClient while providing a platform specific handler (System.Net.Http.WinHttpHandler or System.Net.Http.HttpClientHandler) whose CheckCertificateRevocationList property is possibly set to false will allow revoked certificates to be accepted by the System.Net.Http.HttpClient as valid.

This rule is similar to CA5399, but analysis can't determine that the CheckCertificateRevocationList property is definitely false or not set.

#Rule description

A revoked certificate isn't trusted anymore. It could be used by attackers passing some malicious data or stealing sensitive data in HTTPS communication.

#How to fix violations

Set the System.Net.Http.HttpClientHandler.CheckCertificateRevocationList property to true explicitly. If the System.Net.Http.HttpClientHandler.CheckCertificateRevocationList property is unavailable, you need to upgrade your target framework.

#When to suppress warnings

It's safe to suppress this rule if you're sure that the CheckCertificateRevocationList property is set correctly.

#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 CA5400
// The code that's violating the rule is on this line.
#pragma warning restore CA5400

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

[*.{cs,vb}]
dotnet_diagnostic.CA5400.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 this option 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 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

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:

#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

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:

#Pseudo-code examples

using System;
using System.Net.Http;

class ExampleClass
{
    void ExampleMethod(bool checkCertificateRevocationList)
    {
        WinHttpHandler winHttpHandler = new WinHttpHandler();
        winHttpHandler.CheckCertificateRevocationList = checkCertificateRevocationList;
        Random r = new Random();

        if (r.Next(6) == 4)
        {
            winHttpHandler.CheckCertificateRevocationList = true;
        }

        HttpClient httpClient = new HttpClient(winHttpHandler);
    }
}

#Solution

using System.Net.Http;

class ExampleClass
{
    void ExampleMethod()
    {
        WinHttpHandler winHttpHandler = new WinHttpHandler();
        winHttpHandler.CheckCertificateRevocationList = true;
        HttpClient httpClient = new HttpClient(winHttpHandler);
    }
}