gcp_proxy dotnet with basic sample (https://github.com/salrashid123/gcpsamples/tree/master/proxy)

Main.cs

using System;

using Google.Cloud.Storage.V1;
using Google.Cloud.PubSub.V1;

using Google.Apis.Auth.OAuth2;
using System.Net;
using System.Net.Http;
using System.Threading.Tasks;
using Google.Apis.Http;
using Google.Apis.Services;
using Google.Apis.Storage.v1;

using Google.Api.Gax.ResourceNames;


namespace main
{
    class Program
    {

        const string projectID = "your-project";

        [STAThread]
        static void Main(string[] args)
        {
            new Program().Run().Wait();
        }

        private async Task Run()
        {

// 1. basic auth, with usercredentials
// need export http_proxy=http://user1:user1@localhost:3128 for pubsub
// configure ProxySupportedHttpClientFactory with auth for gcs, oauth2

//  auth Y
//  gcs Y
//  pubsub Y

// 1638363563.445      0 192.168.9.1 TCP_DENIED/407 3999 CONNECT oauth2.googleapis.com:443 - HIER_NONE/- text/html
// 1638363563.662      0 192.168.9.1 TCP_DENIED/407 4068 CONNECT storage.googleapis.com:443 - HIER_NONE/- text/html
// 1638363564.438    776 192.168.9.1 TCP_TUNNEL/200 45147 CONNECT storage.googleapis.com:443 user1 HIER_DIRECT/142.250.73.208 -
// 1638363564.438    345 192.168.9.1 TCP_TUNNEL/200 7877 CONNECT pubsub.googleapis.com:443 user1 HIER_DIRECT/142.250.73.202 -
// 1638363564.438    987 192.168.9.1 TCP_TUNNEL/200 7348 CONNECT oauth2.googleapis.com:443 user1 HIER_DIRECT/142.250.73.234 -

// NOTE, see deny first

// 2. no basic auth, with service account credentials
// export GOOGLE_APPLICATION_CREDENTIALS=/path/to/svc_account.json
// Invalid Credentials [401]
// Errors [
// 	Message[Invalid Credentials] Location[Authorization - header] Reason[authError] Domain[global]
// ]

// 1638363615.081      0 192.168.9.1 TCP_DENIED/407 4068 CONNECT storage.googleapis.com:443 - HIER_NONE/- text/html
// 1638363615.287    201 192.168.9.1 TCP_TUNNEL/200 8242 CONNECT storage.googleapis.com:443 user1 HIER_DIRECT/142.250.73.208 -

// 3. no basicauth, with ServiceAccountCredential
            //var stream = new FileStream("/path/to/svc_account.json", FileMode.Open, FileAccess.Read);
            //ServiceAccountCredential sacredential = ServiceAccountCredential.FromServiceAccountData(stream);
            GoogleCredential credential = await GoogleCredential.GetApplicationDefaultAsync();
            credential = credential.CreateWithHttpClientFactory(new ProxySupportedHttpClientFactory());

            StorageService service = new StorageService(new BaseClientService.Initializer
            {
                HttpClientInitializer = credential,
                ApplicationName = StorageClientImpl.ApplicationName,
                HttpClientFactory = new ProxySupportedHttpClientFactory(),
            });
           var client = new StorageClientImpl(service, null);

            foreach (var b in client.ListBuckets(projectID))
                Console.WriteLine(b.Name);

            PublisherServiceApiClient publisher = PublisherServiceApiClient.Create();
            ProjectName projectName = ProjectName.FromProject(projectID);
            foreach (Topic t in publisher.ListTopics(projectName))
                Console.WriteLine(t.Name);
        }

    }

    public class ProxySupportedHttpClientFactory : HttpClientFactory
    {
        protected override HttpMessageHandler CreateHandler(CreateHttpClientArgs args)
        {
            ICredentials credentials = new NetworkCredential("user1", "user1");
            var proxy = new WebProxy("http://127.0.0.1:3128", true, null, credentials);            
            //var proxy = new WebProxy("http://127.0.0.1:3128", true, null, null);
            var webRequestHandler = new HttpClientHandler()
            {
                UseProxy = true,
                Proxy = proxy,
                UseCookies = false
            };
            return webRequestHandler;
        }
    }

}