Using TFS Rest API works from curl but not from client dotnet library

Question

I'm using the following code from the library Microsoft.VisualStudio.Services.Client:

var credential = new VssBasicCredential("", "<PAT>");
var url = "<url>"";
using var vssConnection = new VssConnection(new Uri(url), credential);
await vssConnection.ConnectAsync();

It fails with the following exception, which I assume has to do with server not allowing basic auth:

System.ComponentModel.Win32Exception (0x80090020): GSSAPI operation failed with error - Unspecified GSS failure.  Minor code may provide more information (SPNEGO cannot find mechanisms to negotiate).
   at System.Net.NTAuthentication.GetOutgoingBlob(Byte[] incomingBlob, Boolean throwOnError, SecurityStatusPal& statusCode)
   at System.Net.NTAuthentication.GetOutgoingBlob(String incomingBlob)
   at System.Net.Http.AuthenticationHelper.SendWithNtAuthAsync(HttpRequestMessage request, Uri authUri, ICredentials credentials, Boolean isProxyAuth, HttpConnection connection, HttpConnectionPool connectionPool, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithNtConnectionAuthAsync(HttpConnection connection, HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithRetryAsync(HttpRequestMessage request, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.AuthenticationHelper.SendWithAuthAsync(HttpRequestMessage request, Uri authUri, ICredentials credentials, Boolean preAuthenticate, Boolean isProxyAuth, Boolean doRequestAuth, HttpConnectionPool pool, CancellationToken cancellationToken)
   at System.Net.Http.DecompressionHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.DiagnosticsHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.Services.Common.VssHttpMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.Services.Common.VssHttpRetryMessageHandler.SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.FinishSendAsyncBuffered(Task`1 sendTask, HttpRequestMessage request, CancellationTokenSource cts, Boolean disposeCts)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.SendAsync(HttpRequestMessage message, HttpCompletionOption completionOption, Object userState, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.SendAsync[T](HttpRequestMessage message, Object userState, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.Services.Location.Client.LocationHttpClient.GetConnectionDataAsync(ConnectOptions connectOptions, Int64 lastChangeId, CancellationToken cancellationToken, Object userState)
   at Microsoft.VisualStudio.Services.WebApi.Location.VssServerDataProvider.GetConnectionDataAsync(ConnectOptions connectOptions, Int32 lastChangeId, CancellationToken cancellationToken)
   at Microsoft.VisualStudio.Services.WebApi.Location.VssServerDataProvider.ConnectAsync(ConnectOptions connectOptions, CancellationToken cancellationToken)

However, I manage to execute REST command successfully from command line

curl <url>/_apis/projects -u :<PAT>

I'm using Azure Devops Server 2019 for which I cannot modify any configurations. I'm running the code from dotnet-core Alpine docker image.

Is it a limitation of the dotnet library or am I using it wrong?

Why do you use the method ConnectAsync? which rest api do you want to use? — Shayki Abramczyk
– Shayki Abramczyk, Commented Jan 22, 2020 at 16:24
That's what I saw in the examples. You say I should skip it? I'm trying to use apis under GitHttpClient - get projects, get repositories etc — Mugen
– Mugen, Commented Jan 22, 2020 at 16:32
I'm not using it, just vssConnection.GetClient<GitHttpClient>(); — Shayki Abramczyk
– Shayki Abramczyk, Commented Jan 22, 2020 at 16:35

LunicLynx · Accepted Answer · 2021-10-15 11:40:23Z

1

I got this error with an expired AccessToken.

Verified this with curl.

After creating a new Token it worked.

answered Oct 15, 2021 at 11:40

LunicLynx

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Frank · Accepted Answer · 2021-10-15 14:53:45Z

1

I had the same error in a program that ran in a Docker container. The cause was an expired PAT. This was not very clear from the error message ("SPNEGO cannot find mechanisms to negotiate"). In addition, the expired PAT still worked on my development machine. That's why I didn't even think that the PAT could have expired.

Newly generated PAT: Everything is running.

answered Oct 15, 2021 at 14:53

Frank

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1 Comment

Community Over a year ago

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

Levi Lu-MSFT · Accepted Answer · 2020-01-23 06:51:37Z

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If you want to use GitHttpClient, As @Shayki Abramczyk pointed out you should use vssConnection.GetClient<GitHttpClient>() to get GitHttpClient connection.

var credential = new VssBasicCredential("", "<PAT>");
var url = "<url>"";
using var vssConnection = new VssConnection(new Uri(url), credential);
GitHttpClient gitClient = vssConnection.GetClient<GitHttpClient>();

You can follow the examples in the QuickStarts and Samples from Microsoft documents

answered Jan 23, 2020 at 6:51

Levi Lu-MSFT

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2 Comments

Levi Lu-MSFT Over a year ago

Can you try install gss-ntlmssp and set AppContext.SetSwitch("System.Net.Http.UseSocketsHttpHandler", false) as describe in this hread

Mugen Over a year ago

Thanks, I found the issue when trying to install gss-ntlmssp

Mugen · Accepted Answer · 2020-01-23 10:26:44Z

0

The issue was with the Alpine distribution of dotnet Docker image, it does not yet support gss-ntlmssp. Switching to the standard image (Ubuntu based - mcr.microsoft.com/dotnet/core/aspnet:3.1) solved the issue.

answered Jan 23, 2020 at 10:26

Mugen

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