我有一个生成签名 Amazon S3 URL 的 PHP 函数，如下所示：
if(!function_exists('el_crypto_hmacSHA1')){
/**
* Calculate the HMAC SHA1 hash of a string.
*
* @param string $key The key to hash against
* @param string $data The data to hash
* @param int $blocksize Optional blocksize
* @return string HMAC SHA1
*/
function el_crypto_hmacSHA1($key, $data, $blocksize = 64) {
if (strlen($key) > $blocksize) $key = pack('H*', sha1($key));
$key = str_pad($key, $blocksize, chr(0x00));
$ipad = str_repeat(chr(0x36), $blocksize);
$opad = str_repeat(chr(0x5c), $blocksize);
$hmac = pack( 'H*', sha1(
($key ^ $opad) . pack( 'H*', sha1(
($key ^ $ipad) . $data
))
));
return base64_encode($hmac);
}
}
if(!function_exists('el_s3_getTemporaryLink')){
/**
* Create temporary URLs to your protected Amazon S3 files.
*
* @param string $accessKey Your Amazon S3 access key
* @param string $secretKey Your Amazon S3 secret key
* @param string $bucket The bucket (bucket.s3.amazonaws.com)
* @param string $path The target file path
* @param int $expires In minutes
* @return string Temporary Amazon S3 URL
* @see http://awsdocs.s3.amazonaws.com/S3/20060301/s3-dg-20060301.pdf
*/
function el_s3_getTemporaryLink($accessKey, $secretKey, $bucket, $path, $expires = 5) {
// Calculate expiry time
$expires = time() + intval(floatval($expires) * 60);
// Fix the path; encode and sanitize
$path = str_replace('%2F', '/', rawurlencode($path = ltrim($path, '/')));
// Path for signature starts with the bucket
$signpath = '/'. $bucket .'/'. $path;
// S3 friendly string to sign
$signsz = implode("\n", $pieces = array('GET', null, null, $expires, $signpath));
// Calculate the hash
$signature = el_crypto_hmacSHA1($secretKey, $signsz);
// Glue the URL ...
$url = sprintf('https://%s/%s', $bucket, $path);
// ... to the query string ...
$qs = http_build_query($pieces = array(
'AWSAccessKeyId' => $accessKey,
'Expires' => $expires,
'Signature' => $signature,
));
// ... and return the URL!
return $url.'?'.$qs;
}
}
我有一个带有表单按钮的页面，用于下载 zip 文件：
<?php
// Grab the file url
$file_url = get_post_meta($post->ID, 'file_url', true);
// Grab just the filename with extension
$file_name = basename($file_url);
// AWS details
$accessKey = "AKIAJJLX2F7GUDTQ23AA";
$secretKey = "<REMOVED>";
$bucket_name = "media.themixtapesite.com";
// Create new S3 Expiry URL
$download_url = el_s3_getTemporaryLink($accessKey, $secretKey, $bucket_name, $file_name);
if (is_user_logged_in()) { ?>
<div class="download_button_div">
<?php echo '<form action="'.$download_url.'" class="download_button_div">'; ?>
<!--Download counter-->
<input type="hidden" name="download_counter" value="<?php (int)$download_count = get_post_meta($post->ID, 'download_counter', true);
$download_count++;
update_post_meta($post->ID, 'download_counter', $download_count); ?>">
<button type='submit' class='download_button'>Download</button>
</form>
如您所见，我只是将表单操作设置为我要下载的文件的 URL。这工作正常。它会生成一个签名的、过期的 S3 URL 并下载文件。
在另一个页面上，我使用相同的功能，但形式略有不同，这是下载单个 mp3 文件：
<?php
// Grab the file url
$file_url = $mp3s;
// Grab just the filename with extension
$file_name = basename($file_url);
// AWS details
$accessKey = "AKIAJJLX2F7GUDTQ23AA";
$secretKey = "<REMOVED>";
$bucket_name = "mixtape2.s3.amazonaws.com";
// Create new S3 Expiry URL
$download_url = el_s3_getTemporaryLink($accessKey, $secretKey, $bucket_name, $file_name);
?>
<!--Download individual MP3 file direct from player-->
<span style="right:27px; position:absolute;">
<form action="download_file.php" method="post" name="downloadform">
<input name="file_name" value="<?php echo basename($mp3s); ?>" type="hidden">
<input name="real_file" value="<?php echo $download_url; ?>" type="hidden">
<input type="image" src="download.jpg" border="0" width="17" alt="Download the MP3" />
</form>
正如您在此表单上看到的，我使用 POST 将表单提交到另一个名为“download_file.php”的文件进行处理。“download_file.php”只是一个强制下载 mp3 文件而不是在浏览器中打开它的文件：
<?php
if(isset($_POST['file_name'])){
$player_file = $_POST['file_name'];
header('Content-type: audio/mpeg3');
header('Content-Disposition: attachment; filename="themixtapesite_'.$player_file.'"');
readfile($_POST['real_file']);
exit();
}
?>
我遇到的问题是，在第二页（我提交到“download_file.php”的地方），生成的 URL 不起作用。如果我提交表单，它只会下载一个 0kb 的文件。如果我查看源代码，然后将链接复制并粘贴到浏览器中，我会收到一条 S3 错误消息，告诉我签名不匹配。
我不明白为什么我的第一页有效，但我的第二页却没有。URL 都是使用相同的函数生成的？
任何帮助表示赞赏。