[Note: _dot_ and _colon_ are used below to circumvent the ⧼abusefilter-warning-linkspam⧽]
It is not related to the images being accessible by any non-private wiki viewer. As I mention above:
"Cloudfront, ironically, has no 'public permissions' despite effectively making the entire bucket publicly readable via serving all of its contents through a subdomain..."
Why is the fact that any visitor can view/download the images not conflicting with the S3 buckets not being considered "public"? Because of the following configuration:
- set $wgAWSBucketDomain = 'img_dot_mysite_dot_com'; as indicated in the extension's readme
- set Cloudfront to serve the images from my bucket to 'img_dot_mysite_dot_com'
- set a Bucket Policy in the S3 bucket to allow Cloudfront to serve the images as follows:
Here the buckets are not considered public with regards to the "4 public access blocks" for S3 but Cloudfront is granted access through the bucket policy. That read access is very well isolated from any other S3 type access, e.g. Put. Additionally it adds the extra layer of security of having the 4 public blocks enabled. This is our desired security setting.
And if I use the extension with "4 public access blocks", viewing the images in the wiki is not a problem. Any non-private wiki viewer can view the images given they are being served by AWS Cloudfront.
The problem comes when the EC2 server tries to write to the bucket. Why? it seems to me because the IAM policy is "considered public" by S3, and therefore I get an error such as the following:
Warning: doCreateInternal: S3Exception: Error executing "PutObject" on "https_colon_//s3_dot_amazonaws_dot_com/XXXXXXXXXX/thumb/XXXXXXXXXXXXXXXXX.jpg/120px-XXXXXXXXXXXXXXXXX.jpg"; AWS HTTP error: Client error: `PUT https_colon_//s3_dot_amazonaws_dot_com/XXXXXXXXXXXXXXXXX/thumb/XXXXXXXXXXXXXXXXX.jpg/120px-XXXXXXXXXXXXXXXXX.jpg` resulted in a `403 Forbidden` response:
AccessDeniedAccess DeniedXXXXXX (truncated...) AccessDenied (client): Access Denied -
AccessDeniedAccess Denied XXXXXXXXXXXXXXXXX/XXXXXXXXXXXXXXXXX/XXXXXXXXXXXXXXXXX/seo= in /var/www/html/w/extensions/AWS/s3/AmazonS3FileBackend.php on line 1117