How to combine stream name in AWS cloudfront? - php

Question

Amazon Cloudfront SDK and example code - how do I combine the stream name? All the other functions are spelled out, but I can't see any definition or example for create_stream_name().
Below is the complete code from the example as described in the documentation here : https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/CreateURL_PHP.html
As you can see, the function create_stream_name() does not appear anywhere but is called in line 12, which will result in a "call to undefined function" error. How should I define create_stream_name()?
function get_canned_policy_stream_name($video_path, $private_key_filename, $key_pair_id, $expires) {
// this policy is well known by CloudFront, but you still need to sign it,
// since it contains your parameters
$canned_policy = '{"Statement":[{"Resource":"' . $video_path . '","Condition":{"DateLessThan":{"AWS:EpochTime":'. $expires . '}}}]}';
// sign the canned policy
$signature = $this->rsa_sha1_sign($canned_policy, $private_key_filename);
// make the signature safe to be included in a url
$encoded_signature = $this->url_safe_base64_encode($signature);
// combine the above into a stream name
$stream_name = create_stream_name($video_path, null, $encoded_signature, $key_pair_id, $expires);
// url-encode the query string characters to work around a flash player bug
return encode_query_params($stream_name);
}
function rsa_sha1_sign($policy, $private_key_filename) {
$signature = "";
// load the private key
$fp = fopen($private_key_filename, "r");
$priv_key = fread($fp, 8192);
fclose($fp);
$pkeyid = openssl_get_privatekey($priv_key);
// compute signature
openssl_sign($policy, $signature, $pkeyid);
// free the key from memory
openssl_free_key($pkeyid);
return $signature;
}
function url_safe_base64_encode($value) {
$encoded = base64_encode($value);
// replace unsafe characters +, = and / with
// the safe characters -, _ and ~
return str_replace(
array('+', '=', '/'),
array('-', '_', '~'),
$encoded);
}

Answer 1

The function create_stream_name() is defined in the full example (demo.php) which you can download at https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/samples/demo-php.zip. The full example is linked to at the top of the documentation page, though it's somewhat obscured behind the text "Signature Code for Video Streaming in PHP." [Update: It's no longer obscured, see below.]
Full disclosure: I'm the person responsible for that documentation page, so I'll do a couple of things to make it better:
Make the link to the full sample more discoverable. [Update: The download URL for the full example is now more prominent at the top of the documentation page.]
Add the full example to the page, so you can see and copy it right off the page, rather than having to download a zip file. [Update: The full example is now published at the bottom of the documentation page.]