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Failed to load resource: Request header field Accept-Encoding is not allowed (Safari)

Discussion in 'WebGL' started by liortal, Apr 3, 2016.

  1. liortal

    liortal

    Joined:
    Oct 17, 2012
    Posts:
    3,555
    We are sending requests to receive FB user images in our WebGL version of our game.

    The URL we send has the following format: https://graph.facebook.com/10153195058465905/picture?redirect=true&height=60&type=normal&width=65

    (replace my id with any Facebook user id)

    The error we're seeing is something like this:
    This only happens on Safari. Is this a limitation of WebGL? has anyone else faced this issue ?
     
    liortal, Apr 3, 2016
    #1

  2. alexsuvorov

    alexsuvorov

    Unity Technologies

    Joined:
    Nov 15, 2015
    Posts:
    327
    Hello liortal.

    I have just been able to successfully download your exact image using WWW from WebGL in Safari.
    Could you provide your exact code and Unity/Safari versions?
     
    alexsuvorov, Apr 3, 2016
    #2

  3. liortal

    liortal

    Joined:
    Oct 17, 2012
    Posts:
    3,555
    The issue is that the request to FB results in a redirect. The redirected request contains headers that are not handled correctly by Safari.

    Here is roughly the code we use:
    Code (CSharp):
    1. private const string IMAGE_URL_FORMAT = @"https://graph.facebook.com/{0}/picture?redirect=true&height={1}&type=normal&width={2}";
    2.  
    3. var www = new WWW(string.Format(IMAGE_URL_FORMAT, fbId, 65, 65));
    4. yield return www;
     
    liortal, Apr 4, 2016
    #3

  4. alexsuvorov

    alexsuvorov

    Unity Technologies

    Joined:
    Nov 15, 2015
    Posts:
    327
    Thank you. I was able to reproduce the issue. Could you please create a bug report for this and post the case number here?
     
    alexsuvorov, Apr 4, 2016
    #4

  5. liortal

    liortal

    Joined:
    Oct 17, 2012
    Posts:
    3,555
    Reported a bug: (Case 785491) Failing to download FB images on WebGL in Safari
     
    liortal, Apr 4, 2016
    #5

  6. alexsuvorov

    alexsuvorov

    Unity Technologies

    Joined:
    Nov 15, 2015
    Posts:
    327
    Thank you. For now you may use the following (or similar) workaround: http://forum.unity3d.com/threads/on...trol-allow-origin-header.385628/#post-2508391
    Just add
    curl_setopt($ch, CURLOPT_FOLLOWLOCATION, TRUE);
    if you decide to use php proxy with curl.
    Or you may as well use
    $context = stream_context_create($request_headers);
    $response = file_get_contents($_GET["url"], false, $context);
    noted in other comments in that thread.
     
    Last edited: Apr 4, 2016
    alexsuvorov, Apr 4, 2016
    #6

  7. liortal

    liortal

    Joined:
    Oct 17, 2012
    Posts:
    3,555
    Our game client directly contacts Facebook, we don't have a proxy server in the middle. For the time being we worked-around the issue by avoiding the automatic redirect. We receive a JSON response from Facebook with the actual image URL and then we load that URL to get the image.
     
    liortal, Apr 4, 2016
    #7

  8. alexsuvorov

    alexsuvorov

    Unity Technologies

    Joined:
    Nov 15, 2015
    Posts:
    327
    That's great, means you don't need any additional workaround here. But just in case, you may still consider using a proxy server when you need to download a resource from a server that does not provide proper CORS headers.
     
    alexsuvorov, Apr 4, 2016
    #8

  9. alexsuvorov

    alexsuvorov

    Unity Technologies

    Joined:
    Nov 15, 2015
    Posts:
    327
    This issue is not specific to WebGL, as you can see in the console of the following example: https://jsfiddle.net/ho26kzap/

    I'm not sure if there is any trick that can make it work as you expect without any workarounds, but the actual problem is the following:
    The redirected request (from https://graph.facebook.com/10153195058465905/picture?redirect=true&height=60&type=normal&width=65 to https://scontent.xx.fbcdn.net/hprof...=58294f494cd76b395a5d3190e2e1d0a6&oe=578D7AC9) is being preflighted in Safari with OPTIONS and Access-Control-Request-Headers: accept-encoding, origin, accept-language, however, https://scontent.xx.fbcdn.net responds with Access-Control-Allow-Headers: RANGE. Had the https://scontent.xx.fbcdn.net responded with Access-Control-Allow-Headers: range, accept-encoding, origin, accept-language, the request would succeed.

    Similar issue can be seen in development builds of other browsers (i.e. in Chrome Canary, due to the usage of access-control-request-headers: x-devtools-emulate-network-conditions-client-id in preflighted request)
     
    Last edited: Apr 4, 2016
    alexsuvorov, Apr 4, 2016
    #9