Command "git credential-manager-core diagnose" fails Networking diagnostic when used with NTLM proxy

[cjquintero]

Which version of GCM are you using?

From a terminal, run git credential-manager-core --version and paste the output.

2.0.785+6074e4e3d3

Problem description

I am on a Windows 10 corporate computer behind a proxy that uses NTLM authentication.

My .gitconfig file has a configuration like this, that is, with empty credentials:

[http]
	proxy = http://:@myproxy.mycompany.com:80

Commands such as the following work as expected showing the browser window to authenticate:

git clone https://[email protected]/myorg/myteamproject/_git/myrepo

So far so good. That works (as expected) because credential-manager-core, when gitconfig has empty credentials internally creates an instance of WebProxy with UseDefaultCredentials = true. See:

https://github.com/GitCredentialManager/git-credential-manager/blob/main/src/shared/Core/HttpClientFactory.cs#L240-L243

However, when I run this command:

git credential-manager-core diagnose

Expected behavior

No exception, all (seven) diagnostics should pass.

Actual behavior

The Networking diagnostic fails because it requests proxy authentication (message translated to English):

[FAIL] Networking

    [!] Encountered an exception [!]
    System.Net.Http.HttpRequestException: An error occurred while sending the request. ---> System.Net.WebException: The remote server returned an error: (407) Proxy Authentication Required.

Root cause

The root cause is that the Networking diagnostic creates a rawHttpClient = new HttpClient() without proxy, whose call fails and returns:

https://github.com/GitCredentialManager/git-credential-manager/blob/main/src/shared/Core/Diagnostics/NetworkingDiagnostic.cs#L30-L33

and there is another bug a few lines later: the contextHttpClient = _httpFactory.CreateClient(), who is created with proxy and that would succeed, is never used, the code of the call uses rawHttpClient again:

https://github.com/GitCredentialManager/git-credential-manager/blob/main/src/shared/Core/Diagnostics/NetworkingDiagnostic.cs#L37-L40