<?php

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);
}

function create_stream_name($stream, $policy, $signature, $key_pair_id, $expires) {
    $result = $stream;
    // if the stream already contains query parameters, attach the new query parameters to the end
    // otherwise, add the query parameters
    $separator = strpos($stream, '?') == FALSE ? '?' : '&';
    // the presence of an expires time means we're using a canned policy
    if($expires) {
        $result .= $path . $separator . "Expires=" . $expires . "&Signature=" . $signature . "&Key-Pair-Id=" . $key_pair_id;
    } 
    // not using a canned policy, include the policy itself in the stream name
    else {
        $result .= $path . $separator . "Policy=" . $policy . "&Signature=" . $signature . "&Key-Pair-Id=" . $key_pair_id;
    }

    // new lines would break us, so remove them
    return str_replace('\n', '', $result);
}

function encode_query_params($stream_name) {
    // the adobe flash player has trouble with query parameters being passed into it, 
    // so replace the bad characters with their url-encoded forms
    return str_replace(
        array('?', '=', '&'),
        array('%3F', '%3D', '%26'),
        $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 . '}}}]}';
    // the policy contains characters that cannot be part of a URL, so we base64 encode it
    $encoded_policy = url_safe_base64_encode($canned_policy);
    // sign the original policy, not the encoded version
    $signature = rsa_sha1_sign($canned_policy, $private_key_filename);
    // make the signature safe to be included in a url
    $encoded_signature = url_safe_base64_encode($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 get_custom_policy_stream_name($video_path, $private_key_filename, $key_pair_id, $policy) {
    // the policy contains characters that cannot be part of a URL, so we base64 encode it
    $encoded_policy = url_safe_base64_encode($policy);
    // sign the original policy, not the encoded version
    $signature = rsa_sha1_sign($policy, $private_key_filename);
    // make the signature safe to be included in a url
    $encoded_signature = url_safe_base64_encode($signature);

    // combine the above into a stream name
    $stream_name = create_stream_name($video_path, $encoded_policy, $encoded_signature, $key_pair_id, null);
    // url-encode the query string characters to work around a flash player bug
    return encode_query_params($stream_name);
}


// Path to your private key.  Be very careful that this file is not accessible
// from the web!

$private_key_filename = '/home/test/public_html/test-pvk.pem';
$key_pair_id = 'APKRV7T95DYOCZDK8FTA';

$video_path = 'example.mp4';

$expires = time() + 300; // 5 min from now
$canned_policy_stream_name = get_canned_policy_stream_name($video_path, $private_key_filename, $key_pair_id, $expires);

$client_ip = $_SERVER['REMOTE_ADDR'];
$policy = 
'{'.
    '"Statement":['.
        '{'.
            '"Resource":"'. $video_path . '",'.
            '"Condition":{'.
                '"IpAddress":{"AWS:SourceIp":"' . $client_ip . '/32"},'.
                '"DateLessThan":{"AWS:EpochTime":' . $expires . '}'.
            '}'.
        '}'.
    ']' .
'}';
$custom_policy_stream_name = get_custom_policy_stream_name($video_path, $private_key_filename, $key_pair_id, $policy);

?>

<html>
<head>
<title>CloudFront</title>
<script type='text/javascript' src='http://dpl7es807iygy.cloudfront.net/player/swfobject.js'></script>
</head>
<body>
<h1>Amazon CloudFront</h1>
<h2>Canned Policy</h2>
<h3>Expires at <?= gmdate('Y-m-d H:i:s T', $expires) ?></h3>
<br />
 
<div id='canned'>The canned policy video will be here</div>

<h2>Canned Policy</h2>
<h3>Expires at <?= gmdate('Y-m-d H:i:s T', $expires) ?> only viewable by IP <?= $client_ip ?></h3>
<div id='custom'>The custom policy video will be here</div>

<!-- ************** Have to update the player.swf path to a real JWPlayer instance.  
The fake one means that external people can't watch the video right now -->
<script type='text/javascript'>
  var so_canned = new SWFObject('http://location.domname.com/~jvngkhow/player.swf','mpl','640','360','9');
  so_canned.addParam('allowfullscreen','true');
  so_canned.addParam('allowscriptaccess','always');
  so_canned.addParam('wmode','opaque');
  so_canned.addVariable('file','<?= $canned_policy_stream_name ?>');
  so_canned.addVariable('streamer','rtmp://s3nzfm0poyjpct.cloudfront.net/cfx/st');
  so_canned.write('canned');

  var so_custom = new SWFObject('http://location.domname.com/~jvngkwrg/player.swf','mpl','640','360','9');
  so_custom.addParam('allowfullscreen','true');
  so_custom.addParam('allowscriptaccess','always');
  so_custom.addParam('wmode','opaque');
  so_custom.addVariable('file','<?= $custom_policy_stream_name ?>');
  so_custom.addVariable('streamer','rtmp://s3nzfm0poyjpct.cloudfront.net/cfx/st');
  so_custom.write('custom');
</script>
</body>
</html>