Amazon S3 CORS (Cross-Origin Resource Sharing) and Firefox cross-domain font loading

Question

Update September 10, 2014:

You shouldn't need to do any of the query string hacks below anymore since Cloudfront properly supports CORS now. See http://aws.amazon.com/blogs/aws/enhanced-cloudfront-customization/ and this answer for more info: https://stackoverflow.com/a/25305915/308315

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OK, I finally got the fonts working using the config below with a little tweak from examples in the documentation.

My fonts are hosted on S3, but fronted by cloudfront.

I'm not sure why it works, my guess is probably that the <AllowedMethod> GET and <AllowedHeader> Content-* is needed.

If anyone proficient with Amazon S3 CORS config can shed some lights on this, it'll be greatly appreciated.

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>https://mydomain.com</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Content-*</AllowedHeader>
        <AllowedHeader>Host</AllowedHeader>
    </CORSRule>
    <CORSRule>
        <AllowedOrigin>https://*.mydomain.com</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Content-*</AllowedHeader>
        <AllowedHeader>Host</AllowedHeader>
    </CORSRule>
</CORSConfiguration>

edit:

Some developers are facing issues of Cloudfront caching the Access-Control-Allow-Origin header. This issue has been addressed by the AWS staff in the link (https://forums.aws.amazon.com/thread.jspa?threadID=114646) below, commented by @Jeff-Atwood.

From the linked thread, it is advised, as a workaround, to use a Query String for differentiating between calls from different domains. I'll reproduce the shortened example here.

Using curl to check response headers:

Domain A: a.domain.com

curl -i -H "Origin: https://a.domain.com" http://hashhashhash.cloudfront.net/font.woff?https_a.domain.com

Response headers from Domain A:

Access-Control-Allow-Origin: https://a.domain.com
Access-Control-Allow-Methods: GET
Access-Control-Max-Age: 3000
Access-Control-Allow-Credentials: true
X-Cache: Miss from Cloudfront

Domain B: b.domain.com

curl -i -H "Origin: http://b.domain.com" http://hashhashhash.cloudfront.net/font.woff?http_b.domain.com

Response headers from Domain B:

Access-Control-Allow-Origin: http://b.domain.com
Access-Control-Allow-Methods: GET
Access-Control-Max-Age: 3000
Access-Control-Allow-Credentials: true
X-Cache: Miss from Cloudfront

You will notice the Access-Control-Allow-Origin has returned different values, which got past the Cloudfront caching.

After some tweaking I seem to have got this to work without the query string hack. More info here: http://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/RequestAndResponseBehaviorS3Origin.html#RequestS3-cors

I'm going to go through my entire setup so that it's easy to see what I've done, hopefully this helps others.

Background Information: I'm using a Rails app that has the asset_sync gem to put assets onto S3. This includes fonts.

Within S3 console, I clicked on my bucket, properties and 'edit cors configuration', here:

Inside the textarea I have something like:

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
    <CORSRule>
        <AllowedOrigin>https://*.example.com</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>*</AllowedHeader>
    </CORSRule>
</CORSConfiguration>

Then within Cloudfront panel (https://console.aws.amazon.com/cloudfront/home) I created a distribution, added an Origin that pointed to my S3 bucket

Then added a behavior for a default path to point to the S3 based origin I setup. What I also did was click on Whitelist headers and added Origin:

What happens now is the following, which I believe is right:

1) Check that S3 headers are being set correctly

curl -i -H "Origin: https://example.com" https://s3.amazonaws.com/xxxxxxxxx/assets/fonts/my-cool-font.ttf
HTTP/1.1 200 OK
x-amz-id-2: Ay63Qb5uR98ag47SRJ91+YALtc4onRu1JUJgMTU98Es/pzQ3ckmuWhzzbTgDTCt+
x-amz-request-id: F1FFE275C0FBE500
Date: Thu, 14 Aug 2014 09:39:40 GMT
Access-Control-Allow-Origin: https://example.com
Access-Control-Allow-Methods: GET
Access-Control-Max-Age: 3000
Access-Control-Allow-Credentials: true
Vary: Origin, Access-Control-Request-Headers, Access-Control-Request-Method
Cache-Control: public, must-revalidate, proxy-revalidate, max-age=180
Last-Modified: Mon, 09 Dec 2013 14:29:04 GMT
ETag: "98918ee7f339c7534c34b9f5a448c3e2"
Accept-Ranges: bytes
Content-Type: application/x-font-ttf
Content-Length: 12156
Server: AmazonS3

2) Check Cloudfront works with the headers

curl -i -H "Origin: https://example.com" https://xxxxx.cloudfront.net/assets/fonts/my-cool-font.ttf
HTTP/1.1 200 OK
Content-Type: application/x-font-ttf
Content-Length: 12156
Connection: keep-alive
Date: Thu, 14 Aug 2014 09:35:26 GMT
Access-Control-Allow-Origin: https://example.com
Access-Control-Allow-Methods: GET
Access-Control-Max-Age: 3000
Access-Control-Allow-Credentials: true
Cache-Control: public, must-revalidate, proxy-revalidate, max-age=180
Last-Modified: Mon, 09 Dec 2013 14:29:04 GMT
ETag: "98918ee7f339c7534c34b9f5a448c3e2"
Accept-Ranges: bytes
Server: AmazonS3
Vary: Origin
X-Cache: Miss from cloudfront
Via: 1.1 77bdacfea247b6cbe84dffa61da5a554.cloudfront.net (CloudFront)
X-Amz-Cf-Id: cmCxaUcFf3bT48zpPw0Q-vDDza0nZoWm9-_3qY5pJBhj64iTpkgMlg==

(Note the above was a miss from cloudfront because these files are cached for 180 seconds, but the same was working on hits)

3) Hit cloudfront with a different origin (but one that is allowed on CORS for the S3 bucket) - the Access-Control-Allow-Origin is not cached! yay!

curl -i -H "Origin: https://www2.example.com" https://xxxxx.cloudfront.net/assets/fonts/my-cool-font.ttf
HTTP/1.1 200 OK
Content-Type: application/x-font-ttf
Content-Length: 12156
Connection: keep-alive
Date: Thu, 14 Aug 2014 10:02:33 GMT
Access-Control-Allow-Origin: https://www2.example.com
Access-Control-Allow-Methods: GET
Access-Control-Max-Age: 3000
Access-Control-Allow-Credentials: true
Cache-Control: public, must-revalidate, proxy-revalidate, max-age=180
Last-Modified: Mon, 09 Dec 2013 14:29:04 GMT
ETag: "98918ee7f339c7534c34b9f5a448c3e2"
Accept-Ranges: bytes
Server: AmazonS3
Vary: Origin
X-Cache: Miss from cloudfront
Via: 1.1 ba7014bad8e9bf2ed075d09443dcc4f1.cloudfront.net (CloudFront)
X-Amz-Cf-Id: vy-UccJ094cjdbdT0tcKuil22XYwWdIECdBZ_5hqoTjr0tNH80NQPg==

Note above that the domain has successfully changed without a query string hack.

When I change the Origin header, there seems to always be a X-Cache: Miss from cloudfront on the first request then afterwards I get the expected X-Cache: Hit from cloudfront

P.S. It is worth noting that when doing curl -I (capital I) will NOT show the Access-Control-Allow-Origin headers as it only a HEAD, I do -i to make it a GET and scroll up.

My fonts were served correctly until the last push to Heroku... I don't know why, but the wildcard in the CORS allowed origin stopped working. I added all of my prepro and pro domains to the CORS policy in the bucket setting so now it looks like this:

<CORSConfiguration>
    <CORSRule>
        <AllowedOrigin>http://prepro.examle.com</AllowedOrigin>
        <AllowedOrigin>https://prepro.examle.com</AllowedOrigin>
        <AllowedOrigin>http://examle.com</AllowedOrigin>
        <AllowedOrigin>https://examle.com</AllowedOrigin>
        <AllowedMethod>GET</AllowedMethod>
        <MaxAgeSeconds>3000</MaxAgeSeconds>
        <AllowedHeader>Authorization</AllowedHeader>
    </CORSRule>

</CORSConfiguration>

UPDATE: add your http://localhost:PORT too

Well, the documentation states that you can stick the configuration as "the cors subresource in your bucket." I took this to mean I would create a file called "cors" at the root of my bucket with the configuration, but this would not work. In the end I had to login to the Amazon S3 administration area and add the configuration within the properties dialog of my bucket.

S3 could use some better documentation...

In Amazon S3 CORS configuration (S3 Bucket / Permissions / CORS) if you use this:

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
<CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>

CORS works well for Javascript and CSS files, but It does not work for Font files.

You have to specify the domain to allow CORS using the pattern expressed in the @VKen answer: https://stackoverflow.com/a/25305915/618464

So, use this:

<?xml version="1.0" encoding="UTF-8"?>
<CORSConfiguration xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
<CORSRule>
    <AllowedOrigin>*</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>
<CORSRule>
    <AllowedOrigin>https://*.mydomain.com</AllowedOrigin>
    <AllowedMethod>GET</AllowedMethod>
    <MaxAgeSeconds>3000</MaxAgeSeconds>
    <AllowedHeader>*</AllowedHeader>
</CORSRule>
</CORSConfiguration>

Remember to replace "mydomain.com" for your domain.

After this, invalidate the CloudFront cache (CloudFront / Invalidations / Create Invalidation) and It will work.