AWS S3 Download counter - php

Question

I have a file uploaded in AWS s3 bucket and set that file to public permission . i want to share that file in my Facebook .. the thing is i can just copy that public link and share it . but i also want the count of the downloads to stored .. in other way i want to host a php file in my web hosting where there will be a tab like bar in which that file name,file size, download link and total download count will be there . Please help me with the code
I tried the following code which i got from google search but no use
<?php
$aws_key = '_YOUR_AWS_KEY_000000';
$aws_secret = '_your_aws_secret_00000000000000000000000';
$aws_bucket = 'anyexample-test'; // AWS bucket
$aws_object = 'test.png'; // AWS object name (file name)
if (strlen($aws_secret) != 40) die("$aws_secret should be exactly 40 bytes long");
$dt = gmdate('r'); // GMT based timestamp
// preparing string to sign
$string2sign = "GET
{$dt}
/{$aws_bucket}/{$aws_object}";
// preparing HTTP query
$query = "GET /{$aws_bucket}/{$aws_object} HTTP/1.1
Host: s3.amazonaws.com
Connection: close
Date: {$dt}
Authorization: AWS {$aws_key}:".amazon_hmac($string2sign)."\n\n";
echo "Downloading: http://s3.amazonaws.com/{$aws_bucket}/{$aws_object}\n";
list($header, $resp) = downloadREST($fp, $query);
echo "\n\n";
if (strpos($header, '200 OK') === false) // checking for error
die($header."\r\n\r\n".$resp);
$aws_object_fs = str_replace('/', '_', $aws_object);
// AWS object may contain slashes. We're replacing them with underscores
#$fh = fopen($aws_object_fs, 'wb');
if ($fh == false)
die("Can't open file {$aws_object_fs} for writing. Fatal error!\n");
echo "Saving data to {$aws_object_fs}...\n";
fwrite($fh, $resp);
fclose($fh);
// Sending HTTP query, without keep-alive support
function downloadREST($fp, $q)
{
// opening HTTP connection to Amazon S3
// since there is no keep-alive we open new connection for each request
$fp = fsockopen("s3.amazonaws.com", 80, $errno, $errstr, 30);
if (!$fp) die("$errstr ($errno)\n"); // connection failed, pity
fwrite($fp, $q); // sending query
$r = ''; // buffer for result
$check_header = true; // header check flag
$header_end = 0;
while (!feof($fp)) {
$r .= fgets($fp, 256); // reading response
if ($check_header) // checking for header
{
$header_end = strpos($r, "\r\n\r\n"); // this is HTTP header boundary
if ($header_end !== false)
$check_header = false; // We've found it, no more checking
}
}
fclose($fp);
$header_boundary = $header_end+4; // 4 is length of "\r\n\r\n"
return array(substr($r, 0, $header_boundary), substr($r, $header_boundary));
}
// hmac-sha1 code START
// hmac-sha1 function: assuming key is global $aws_secret 40 bytes long
// http://en.wikipedia.org/wiki/HMAC
// warning: key is padded to 64 bytes with 0x0 after first function call
// hmac-sha1 function
function amazon_hmac($stringToSign)
{
if (!function_exists('binsha1'))
{ // helper function binsha1 for amazon_hmac (returns binary value of sha1 hash)
if (version_compare(phpversion(), "5.0.0", ">=")) {
function binsha1($d) { return sha1($d, true); }
} else {
function binsha1($d) { return pack('H*', sha1($d)); }
}
}
global $aws_secret;
if (strlen($aws_secret) == 40)
$aws_secret = $aws_secret.str_repeat(chr(0), 24);
$ipad = str_repeat(chr(0x36), 64);
$opad = str_repeat(chr(0x5c), 64);
$hmac = binsha1(($aws_secret^$opad).binsha1(($aws_secret^$ipad).$stringToSign));
return base64_encode($hmac);
}
// hmac-sha1 code END
?>

Answer 1

I would suggest using the official AWS SDK for PHP, because it has all of the request signing and handling logic implemented for you. Here is an article by one of the SDK's developers that is relevant to what you are doing: Streaming Amazon S3 Objects From a Web Server

Answer 2

Infact if you just need to see the number of downloads, you can achieve this without running yourown server with php.
This info is already available in the S3 bucket logs, if you enable. This will be more accurate, since the in the PHP approach there is no way to track download, if the user take the S3 link directly and share/download.
These logs are little difficult to parse though, but the services like https://qloudstat.com and http://www.s3stat.com/ help here.
Another point: Downloads will be considerably faster, if you enable CDN - Cloudfront in front of the S3 bucket.