Issues generating CloudFront signed URLs; always Access Denied - amazon-web-services

Question

I’m having issues generating signed URLs with CloudFront. Whatever I try, I just get an “Access Denied” response.
I’ve created a distribution in CloudFront, and a CloudFront key pair ID. I’ve downloaded the private and public keys for that key pair ID.
In a simple PHP script, I’m trying the following:
use Aws\CloudFront\CloudFrontClient;
$cloudfront = new CloudFrontClient([
'credentials' => [
'key' => '[redacted]', // Access key ID of IAM user with Administrator policy
'secret' => '[redacted]', // Secret access key of same IAM user
],
'debug' => true,
'region' => 'eu-west-1',
'version' => 'latest',
]);
$expires = strtotime('+6 hours');
$resource = 'https://[redacted].cloudfront.net/mp4/bunny-trailer.mp4';
$url = $cloudfront->getSignedUrl([
'url' => $resource,
'policy' => json_encode([
'Statement' => [
[
'Resource' => $resource,
'Condition' => [
'DateLessThan' => [
'AWS:EpochTime' => $expires,
],
],
],
],
]),
'expires' => $expires,
'key_pair_id' => '[redacted]', // Access key ID of CloudFront key pair
'private_key' => '[redacted]', // Relative path to pk-[redacted].pem file
]);
But when visiting the generated URL, it just always gives me an error in the browser with a code of “AccessDenied”.
What am I doing wrong?

Answer 1

Discovered what the issue was. The objects in my S3 bucket weren’t publicly-accessible, and I hadn’t added an Origin Access Identity, so CloudFront couldn’t pull the objects from my origin (my S3 bucket) to cache them.
As soon as I added an Origin Access Identity and added it to my S3 bucket’s policy, my objects immediately became accessible through my CloudFront distribution via signed URLs.
Relevant documentation: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/private-content-restricting-access-to-s3.html#private-content-creating-oai