I have been wasting time on a small issue adding Authorization header into HttpClient.
The code was plain and simple:
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using (var httpClient = new HttpClient { DefaultRequestHeaders = { Authorization = new AuthenticationHeaderValue("Basic", Convert.ToBase64String(Encoding.ASCII.GetBytes(username + ":" + password))) }) { var response = await httpClient.GetAsync(url); } |
Specifically, I was writing a .NET Core console app, following this wiki page https://github.com/projectkudu/kudu/wiki/Accessing-the-kudu-service and trying to access http://mysite.scm.azurewebsites.net/basicauth. However, I kept getting 401 Unauthorize response and response.RequestMessage.Headers was completely empty.
After having spent some time searching for solution on the Internet but to no avail, I opened Fiddler to see the actual HTTP requests. Turns out, this was what happened behind the scene:
There were actually 2 requests. The first one has the Authorization header and returns a 302 Found. Automatic redirection of HttpClient triggers the second request, and this one didn’t have any Authorization header.
Normally I can just stop there, accept that how things work in .NET and find a workaround. But since .NET Core is open source on GitHub, I decided to dig a bit deeper to understand the reason of this implementation. A quick search about redirection on the corefx repo in GitHub gave me the exact commit that I need: https://github.com/dotnet/corefx/commit/e8a17715fba4ba6cfce4043a2cd117474dfcee05. And voila, I could see the line in RedirectHandler.cs that causing the issue:
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request.Headers.Authorization = null; |
and I could also see the reason in SocketsHttpHandler.cs:
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// Just as with WinHttpHandler and CurlHandler, for security reasons, we do not support authentication on redirects // if the credential is anything other than a CredentialCache. // We allow credentials in a CredentialCache since they are specifically tied to URIs. |
I finally solved my curious case, and I hope this post is useful to you. Feel free to leave me a comment and let me know if you have any suggestion on securely implement the redirection with Authorization header.