產生 SAS 存取非公開的 Blob 資料

dl.php

# 轉換時間
function isoDate($timestamp = null) {
  $tz = @date_default_timezone_get();
  @date_default_timezone_set('UTC');
  
  if (is_null($timestamp)) {
      $timestamp = time();
  }
      
  $returnValue = str_replace('+00:00', '.0000000Z', @date('c', $timestamp));
  @date_default_timezone_set($tz);
  return $returnValue;
}

# 產生 SAS
function createSignature($accountName, $accountKey, $path, $start, $expires) {
  $res = "/$accountName$path";
  
  $strToSign = array();
  $strToSign[] = 'r'; // 權限, 純讀取
  $strToSign[] = $start;
  $strToSign[] = $expires;
  $strToSign[] = $res;

  $sig = base64_encode(
    hash_hmac('sha256',
              implode('\n', $strToSign),
              $accountKey,
              true));

  return $sig;
}

# ....

$baseUrl = "https://ericishandsome.blob.core.windows.net/dl";
$resourceName = "/foo.pdf";

# 設定 SAS 的時效
$start = isoDate(time());
$expires = isoDate(time() + 3600); # 1小時後

# 產生 SAS
$sig = createSignature($accountName, $accountKey, $path, $start, $expires);

# 產生可存取 URL 的 query string
$params = array();
$params[] = 'st=' . urlencode($start);
$params[] = 'se=' . urlencode($expires);
$params[] = 'sr=b'; // 'b' for blob
$params[] = 'sp=r'; // read
$params[] = 'sig=' . urlencode($sig);

# 組合成可存取的 URL
# 大概會長成 https://ericishandsome.blob.core.windows.net/dl/foo.pdf?st=....&se=....&sr=b&sp=r&sig=...... 這樣
$url = "$baseUrl$resourceName?" . implode('&', $params);