Default Proxy in .NET Core 3.1

Question

I need some help with .NET Core 3.1 for code that needs to get out of the corporate proxy. The code works in .NET 4.7.2 by putting the following in the app.config. This, I learned on this site (Thank you!), allows one to get through the corporate proxy server.

 <system.net>
    <defaultProxy useDefaultCredentials="true">
    </defaultProxy>
  </system.net>

The following code snippet works in .NET 4.7.2, and can get out past the proxy. The proxy is stored as an env variable named ALL_PROXY with a value of http:// our internal proxy:port (see [https://github.com/dotnet/corefx/pull/37238/commits/9ba8879ea104afac9dea9a78d3009b5bc700b7c3][1]). This is an Azure Cognitive service, so you will need a key vault, and a Cognitive Service.

  var keyVaultName = Environment.GetEnvironmentVariable("KEY_VAULT_NAME");
  var kvUri = string.Format("{0}{1}{2}", 
                "https://", 
                keyVaultName, 
                ".vault.azure.net");
  var secretClient = new SecretClient(new Uri(kvUri), 
                new DefaultAzureCredential());
  KeyVaultSecret secret = secretClient.GetSecret("FacesSubscription");
  var subscriptionKey = secret.Value;

  var credentials = new ApiKeyServiceClientCredentials(subscriptionKey);
  var textClient = new TextAnalyticsClient(credentials)
  {
      Endpoint = endpoint
   };

On .Net core, I get an http 407 exception. Azure.RequestFailedException: 'Service request failed. Status: 407 (ADAuth-AuthenticationFailed) This exception occurs on the KeyVaultSecret line.

I have researched the issue @

[https://github.com/dotnet/corefx/pull/37238/commits/9ba8879ea104afac9dea9a78d3009b5bc700b7c3][1]
https://github.com/dotnet/corefx/pull/37238
https://github.com/dotnet/corefx/pull/37333
https://github.com/dotnet/runtime/issues/29147

and tried adding code such as

var handler = new HttpClientHandler();
handler.DefaultProxyCredentials = CredentialCache.DefaultCredentials;
var httpClient = new HttpClient(handler);

I looked through the unit tests for the check-ins, but they all seemed to be about web proxies. The links above provide details of how the proxy is implemented.

Does anyone have idea around getting through a work proxy in NET Core with Azure services?

Not yet- the project is on hold and the proxy team is making changes internally. — Tom
– Tom, Commented Jul 15, 2020 at 11:21
this is how I managed to get it working in my case stackoverflow.com/questions/64931470/… @Tom — Ali Hussain
– Ali Hussain, Commented Nov 21, 2020 at 13:32

Sasi Parnandi · Accepted Answer · 2021-01-27 17:13:27Z

3

I have had a similar issue and this fixed it:

IWebProxy proxy = WebRequest.GetSystemWebProxy();
proxy.Credentials = CredentialCache.DefaultCredentials;
HttpClient.DefaultProxy = proxy;

answered Jan 27, 2021 at 17:13

Sasi Parnandi

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1 Comment

ajw170 Over a year ago

Where did you put this in your code? I am assuming it would be best practice to put it in the startup / configuration before any requests go out?

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