# 使用 PHP 创建 URL 签名
<a name="CreateURL_PHP"></a>

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。您可以从 [demo-php.zip](samples/demo-php.zip) 文件下载完整示例。

**备注**  
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](private-content-signed-urls.md)。
还可以通过使用 适用于 PHP 的 AWS SDK 中的 `UrlSigner` 类来创建签名 URL。有关更多信息，请参阅 *适用于 PHP 的 AWS SDKAPI 参考*中的 [Class UrlSigner](https://docs.aws.amazon.com/aws-sdk-php/v3/api/class-Aws.CloudFront.UrlSigner.html)。
在 `openssl_sign` 调用中，请注意，将 `OPENSSL_ALGO_SHA256` 作为第四个参数传递会切换到 SHA-256。（有关完整示例，另请参阅[使用 PHP 创建签名 Cookie](signed-cookies-PHP.md)）。

**Topics**
+ [创建 RSA SHA-1 签名](#sample-rsa-sign)
+ [创建标准策略](#sample-canned-policy)
+ [创建自定义策略](#sample-custom-policy)
+ [完整代码示例](#full-example)

以下部分将代码示例细分到各个单独的部分。您可在下方找到[完整代码示例](#full-example)。

## 创建 RSA SHA-1 签名
<a name="sample-rsa-sign"></a>

本代码示例执行以下操作：
+ 函数 `rsa_sha1_sign` 执行哈希操作并签署策略声明。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);
}
```

以下代码段使用函数 `get_canned_policy_stream_name()` 和 `get_custom_policy_stream_name()` 来创建标准策略和自定义策略。CloudFront 使用这些策略来创建用于流式传输视频的 URL，包括指定过期时间。

然后，您可以使用标准策略或自定义策略来确定如何管理对内容的访问。有关选择哪一项的更多信息，请参阅[决定为签名 URL 使用标准策略还是自定义策略](private-content-signed-urls.md#private-content-choosing-canned-custom-policy)部分。

## 创建标准策略
<a name="sample-canned-policy"></a>

以下代码示例构建了签名的*标准*策略声明。

**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 . '}}}]}';
    // 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
    return $stream_name;
}
```

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](private-content-creating-signed-url-canned-policy.md)。

## 创建自定义策略
<a name="sample-custom-policy"></a>

以下代码示例构建了签名的*自定义* 策略声明。

```
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
    return $stream_name;
}
```

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](private-content-creating-signed-url-custom-policy.md)。

## 完整代码示例
<a name="full-example"></a>

以下代码示例完整演示了使用 PHP 创建 CloudFront 签名 URL。您可以从 [demo-php.zip](samples/demo-php.zip) 文件下载完整示例。

在下面的示例中，您可以修改 `$policy` `Condition` 元素，以同时允许 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](https://docs.aws.amazon.com/AmazonS3/latest/userguide/ipv6-access.html#ipv6-access-iam)。

```
<?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 .= $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 .= $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 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
    return $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
    return $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';

// Make sure you have "Restrict viewer access" enabled on this path behaviour and using the above Trusted key groups (recommended).
$video_path = 'https://example.com/secure/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);

// Get the viewer real IP from the x-forward-for header as $_SERVER['REMOTE_ADDR'] will return viewer facing IP. An alternative option is to use CloudFront-Viewer-Address header. Note that this header is a trusted CloudFront immutable header. Example format: IP:PORT ("CloudFront-Viewer-Address": "1.2.3.4:12345")
$client_ip = $_SERVER['HTTP_X_FORWARDED_FOR'];
$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>
</head>

<body>
    <h1>Amazon CloudFront</h1>
    <h2>Canned Policy</h2>
    <h3>Expires at <?php echo gmdate('Y-m-d H:i:s T', $expires); ?></h3>
    <br />

    <div id='canned'>The canned policy video will be here: <br>
    
        <video width="640" height="360" autoplay muted controls>
        <source src="<?php echo $canned_policy_stream_name; ?>" type="video/mp4">
        Your browser does not support the video tag.
        </video>
    </div>

    <h2>Custom Policy</h2>
    <h3>Expires at <?php echo gmdate('Y-m-d H:i:s T', $expires); ?> only viewable by IP <?php echo $client_ip; ?></h3>
    <div id='custom'>The custom policy video will be here: <br>

         <video width="640" height="360" autoplay muted controls>
         <source src="<?php echo $custom_policy_stream_name; ?>" type="video/mp4">
         Your browser does not support the video tag.
        </video>
    </div> 

</body>

</html>
```

有关更多 URL 签名示例，请参阅以下主题：
+ [使用 Perl 创建 URL 签名](CreateURLPerl.md)
+ [使用 C\$1 和 .NET Framework 创建 URL 签名](CreateSignatureInCSharp.md)
+ [使用 Java 创建 URL 签名](CFPrivateDistJavaDevelopment.md)

您可以不使用签名 URL 来创建签名，而是使用签名 Cookie。有关更多信息，请参阅 [使用 PHP 创建签名 Cookie](signed-cookies-PHP.md)。