duplicati/Duplicati/Library/Utility/HttpClientHelper.cs

// Copyright (C) 2024, The Duplicati Team
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using System;
using System.Collections.Generic;
using System.Net.Http;
using Duplicati.Library.Interface;

namespace Duplicati.Library.Utility;

/// <summary>
/// This class was created as a proxy to access the HttpClientFactory
/// in places where dependency injection is not yet implemented or
/// desirable.
/// </summary>
public static class HttpClientHelper
{
    
    /// <summary>
    /// Globally configured certificate validator to be used across the application.
    /// Each backend can choose when creating the httpclient/requesthandler if it will
    /// use this or the default (null) validator.
    /// </summary>
    public static SslCertificateValidator CertificateValidator { get; set; }

    /// <summary>
    /// Central HttpClient singleton instance to be used across the application as 
    /// per the HttpClientFactory recommended pattern.
    /// </summary>
    public static HttpClient DefaultClient { get; private set; }

    /// <summary>
    /// Reference to the HttpClientFactory instance so we can create specific clients
    /// when the singleton pattnern is not desirable.
    /// </summary>
    private static IHttpClientFactory _factory { get; set; }

    /// <summary>
    /// Sets the factory reference.
    /// </summary>
    /// <param name="factory">IHttpClientFactory instance</param>
    public static void Configure(IHttpClientFactory factory)
    {
        _factory = factory;
        DefaultClient = factory.CreateClient();
    }

    /// <summary>
    /// Creates a new HttpClient instance, to be used in places where the singleton
    /// pattern is not desirable.
    /// </summary>
    /// <returns></returns>
    public static HttpClient CreateClient()
    {
        return _factory?.CreateClient() ?? new HttpClient();
    }

    /// <summary>
    /// Creates a new HttpClient instance with a specific handler, wherever its needed.
    /// </summary>
    /// <param name="handler">HttpClientHandler configured with authentication parameters</param>
    /// <returns></returns>
    public static HttpClient CreateClient(HttpClientHandler handler)
    {
        return new HttpClient(handler);
    }
    
    /// <summary>
    /// Configures the httphandler with the certificate validator, if needed.
    ///
    /// The parameters indicate if it should accept all certificates or only the ones specified in the
    /// hashes array.
    /// </summary>
    /// <param name="handler">The HttpClientHandler to be configured</param>
    /// <param name="acceptAllCertificates">If all certificates will be considered valid</param>
    /// <param name="acceptSpecificCertificateHashes">List of hashes of certificates that will be accepted</param>
    public static void ConfigureHandlerCertificateValidator(HttpClientHandler handler, bool acceptAllCertificates, string[] acceptSpecificCertificateHashes)
    {
        var validator = new SslCertificateValidator(acceptAllCertificates, acceptSpecificCertificateHashes);
        handler.ServerCertificateCustomValidationCallback = validator.ValidateServerCertificate;
    }
}