abstract |
 |
This is an example of non-interactive PHP script which downloads file from Amazon S3 (Simple Storage Service). Additional libraries like HMAC-SHA1 are not required.
compatible |
 |
PHP 4.1.0 or higherPHP 5
Amazon S3 (Simple Storage Service) is a commercial storage web service offered by Amazon Web Services. It is inexpensive, scalable, responsive, and highly reliable. It has no minimum fee, and no start-up cost.
This code uses standard PHP sockets to send REST (HTTP 1.1) queries to Amazon S3 server. It does not support 'keep-alive' connections, so each call to downloadREST() function opens new connection to 's3.amazonaws.com'.
You should set following variables:
- $aws_key — Your AWS Access Key ID
- $aws_secret — Your AWS Secret Access Key
- $aws_bucket — AWS bucket (directory) name. You must specify existing AWS bucket.
- $aws_object — AWS object (file) name. You must specify existing AWS object.
See Amazon S3 Developer Guide for REST protocol details.
You may also download following code as a plain text file.
<?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); // response code is not 200 OK -- failure
$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 queyr
$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));
// returning HTTP response header and retrieved data
}
// hmac-sha1 code START
// hmac-sha1 function: assuming key is global $aws_secret 40 bytes long
// read more at http://en.wikipedia.org/wiki/HMAC
// warning: key($aws_secret) is padded to 64 bytes with 0x0 after first function call
function amazon_hmac($stringToSign)
{
// helper function binsha1 for amazon_hmac (returns binary value of sha1 hash)
if (!function_exists('binsha1'))
{
if (version_compare(phpversion(), "5.0.0", ">=")) {
function binsha1($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
?>
Note, that using this code makes sense for objects uploaded with 'private' or 'authenticated-read' Amazon S3 ACL.
You may download objects with other ACLs(public-read, public-read-write) by simply downloading file from URL:
http://s3.amazonaws.com/bucket_name/object_name
Where 'bucket_name' is AWS bucket name, and 'object_name' is AWS object name.
warning |
 |
This script uses RAM to retrieve files. It will work inefficiently with very large files.Keep your AWS Secret Access Key in secret.
tested |
 |
Windows XP :: PHP 5.2.1Mac OS X 10.4.8 :: PHP 4.4.4