POST Submission via API result in 401 Unauthorized

[d_tan]

I am trying to develop a C# program that will post files as student assignment submissions into Canvas via Canvas API.

• The documentation I am following is here
  Uploading Files - Canvas LMS REST API Documentation
• The issue I am having is on the step 1 in that documentation.
  POST /v1/courses/{course_id}/assignments/{assignment_id}/submissions/{user_id}/files
• The error I am getting is 401 Unauthorized.

Details:

• The token is from an account admin.
• The course is published and so is the assignment.
• The assignment is not due yet.
• Fail on both production Canvas and Test Canvas instance.
• The same code works for other POST method like create a new assignment.
• Form data is
       var formData = new Dictionary<string, string>()

            {

                {"name", "sampleFile.pdf"},

                {"size", fileInfo.Length.ToString()},

                {"content_type", "application/pdf"}

            };

• Same error (401) returns from the live api page, but I guess that was not suppose to work there since the form data about the file are missing.
• In addition to token, I also set the following headers
       httpWebRequest.Method = "POST";

            httpWebRequest.Host = CanvasHost;

            httpWebRequest.ContentType = "application/x-www-form-urlencoded";

            httpWebRequest.Accept = "application/json";

            httpWebRequest.ContentLength = byteArray.Length;

• the form data is write to the request in bytes that are in UTF8 encoding.

Any suggestions?

Doug

[cmoore2 · Accepted solution]

I'm assuming that you're trying to post assignments on behalf of another user.  If so, you should read the masquerading docs.