REST API - Amazon S3 file upload confirmation problems?

[geckojsc]

Hi, hope this is the correct place to ask for help! I've been trying for the last couple of days to upload a file with C# using the Canvas API. After some time battling with REST libraries and such, I'm now fairly certain that what I'm doing is correct, following these steps: Uploading Files - Canvas LMS REST API Documentation

"Step 1: Telling Canvas about the file upload and getting a token"

This works fine, I send a request to Canvas and get the following response:

{   "upload_url": "https://instructure-uploads-eu.s3-eu-west-1.amazonaws.com/",   "upload_params": {     "AWSAccessKeyId": ".......................",     "Filename": "TEST.pdf",     "key": "account_18480000000000001/attachments/2991455/TEST.pdf",     "acl": "private",     "Policy": "..........................",     "Signature": "...........................",     "success_action_redirect": "https://.....canvas url....../api/v1/files/2991455/create_success?quota_exemption=1a9a1bb7a6&uuid=.............................",     "content-type": "application/pdf"   },   "file_param": "file" }

"Step 2: Upload the file data to the URL given in the previous response"

This is where things get a bit weird.

I'm using the multipart form code as given in this tutorial: Multipart Form Post in C#  - Brian Grinstead

I replaced the Dictionary with a List so that the parameters are guaranteed to be added in the correct order.

However, when I send my request to Amazon web services, instead of getting a response like

HTTP/1.1 301 Moved Permanently
Location: https://<canvas>/api/v1/s3_success/1234?uuid=ABCDE

I get status code 200 'OK', with the following headers:

Access-Control-Allow-Headers: Origin, X-Requested-With, Content-Type, Accept, Authorization, Accept-Encoding Access-Control-Allow-Methods: POST, PUT, DELETE, GET, OPTIONS Access-Control-Allow-Origin: * Access-Control-Request-Method: * Status: 200 OK Vary: Accept-Encoding X-Canvas-Meta: q=1139;a=1;g=5Ttwclj1ab2PNhMTWIZMMiylCPoOoff99sh8cXVY;s=1848;c=cluster15;z=eu-west-1a;o=files;n=api_create_success;b=1005488;m=1005488;u=0.12;y=0.00;d=0.04; X-Content-Type-Options: nosniff X-Frame-Options: SAMEORIGIN X-Request-Context-Id: ea77d70b-5671-4cd0-ada9-1c957e8e2a73 X-Request-Processor: a2666ab X-Runtime: 0.221079 X-UA-Compatible: IE=Edge,chrome=1 X-XSS-Protection: 1; mode=block Connection: keep-alive Content-Length: 562 Cache-Control: max-age=0, private, must-revalidate Content-Type: application/json; charset=utf-8 Date: Thu, 28 Jul 2016 03:52:09 GMT ETag: "d4a2e9ce67f15244e424ae9a594909fe" P3P: CP="None, see http://www.instructure.com/privacy-policy" Set-Cookie: _csrf_token=.................; path=/; secure Server: Apache

and the following JSON content:

{"id":2991455,"folder_id":218826,"display_name":"TEST.pdf","filename":"TEST.pdf","content-type":"application/pdf","url":"https://......canvas url....../files/2991455/download?download_frd=1\u0026verifier=..............","size":410908,"created_at":"2016-07-28T03:52:08Z","updated_at":"2016-07-28T03:52:09Z","unlock_at":null,"locked":false,"hidden":false,"lock_at":null,"hidden_for_user":false,"thumbnail_url":null,"modified_at":"2016-07-28T03:52:08Z","locked_for_user":false,"preview_url":"/users/71907/files/2991455/file_preview?annotate=0"}

This doesn't seem to be any kind of error, but it is not the same result as given by the API documentation. I don't know how to proceed to "Step 3: Confirm the upload's success" when I have not been given a location header. I guessed that the success_action_redirect URL from Step 1 might have been able to help, but submitting there just gives a Bad Request error.

Any help would be hugely appreciated, thank you!