使用 PHP 创建 URL 签名 - Amazon CloudFront
示例：RSA SHA-1 签名示例：创建标准策略示例：创建自定义策略完整代码示例
Amazon Web Services 文档中描述的 Amazon Web Services 服务或功能可能因区域而异。要查看适用于中国区域的差异，请参阅 中国的 Amazon Web Services 服务入门 (PDF)。

使用 PHP 创建 URL 签名

运行 PHP 的任何 Web 服务器可使用此 PHP 代码示例，来为私有的 CloudFront 分配创建策略声明和签名。该完整示例使用签名 URL 链接创建一个正常运作的网页，这些链接使用 CloudFront 流播放视频流。您可以在下面下载完整示例：https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/samples/demo-php.zip。

还可以通过使用 Amazon SDK for PHP 中的 UrlSigner 类来创建签名 URL。有关更多信息，请参阅 Amazon SDK for PHPAPI 参考中的 Class UrlSigner。

注意

创建 URL 签名只是使用签名 URL 提供私有内容过程的一部分。有关整个过程的更多信息，请参阅使用签名 URL。

示例：RSA SHA-1 签名

在以下代码示例中，函数 rsa_sha1_sign 哈希并签署策略声明。所需的参数是策略语句和私有密钥，该私有密钥对应于分配的可信密钥组中的公有密钥。接下来，url_safe_base64_encode 函数创建签名 URL 安全版本。

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);
}

示例：创建标准策略

以下代码示例构建了签名的标准策略声明。更多有关标准策略的信息，请参阅 使用标准策略创建签名 URL。

注意

$expires 变量是一个日期/时间戳，必须为整数，而不是字符串。

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 . '}}}]}';

    // sign the canned policy
    $signature = rsa_sha1_sign($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);
}

示例：创建自定义策略

以下代码示例构建了签名的自定义 策略声明。更多有关自定义策略的信息，请参阅 使用自定义策略创建签名 URL。

function get_custom_policy_stream_name($video_path, $private_key_filename, $key_pair_id, $policy) {
    // sign the policy
    $signature = rsa_sha1_sign($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);
}

完整代码示例

以下代码示例完整演示了使用 PHP 创建 CloudFront 签名 URL。您可以在下面下载此完整示例：https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/samples/demo-php.zip。

在下面的示例中，您可以修改 $policy Condition 元素以允许 IPv4 和 IPv6 地址范围。有关示例，请参阅《Amazon Simple Storage Service 用户指南》中的在 IAM 策略中使用 IPv6 地址。

<?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) {
    // 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, $expires);
    // URL-encode the query string characters to support Flash Player
    return encode_query_params($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, $key_pair_id, null);
    // URL-encode the query string characters to support Flash Player
    return encode_query_params($stream_name);
}


// Path to your private key.  Be very careful that this file is not accessible
// from the web!

$private_key_filename = '/home/test/secure/example-priv-key.pem';
$key_pair_id = 'K2JCJMDEHXQW5F';

$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='https://example.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>Custom 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 cannot watch the video right now -->
    <script type='text/javascript'>
  var so_canned = new SWFObject('https://files.example.com/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://example.cloudfront.net/cfx/st');
        so_canned.write('canned');

  var so_custom = new SWFObject('https://files.example.com/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://example.cloudfront.net/cfx/st');
  so_custom.write('custom');
    </script>
</body>

</html>

另请参阅：