Object Storage Service:Use the SDK for .NET to configure Referer-based hotlink protection to prevent unauthorized reference to OSS objects

Usage notes

• Before you configure hotlink protection, make sure that you familiarize yourself with this feature. For more information, see Hotlink protection.

• In this topic, the public endpoint of the China (Hangzhou) region is used. If you want to access OSS from other Alibaba Cloud services in the same region as OSS, use an internal endpoint. For more information about OSS regions and endpoints, see Regions and endpoints.

• In this topic, an OSSClient instance is created by using an OSS endpoint. If you want to create an OSSClient instance by using custom domain names or Security Token Service (STS), see Initialization.

• To configure hotlink protection, you must have the oss:PutBucketReferer permission. To query hotlink protection configurations, you must have the oss:GetBucketReferer permission. For more information, see Attach a custom policy to a RAM user.

Configure hotlink protection for a bucket

The following sample code provides an example on how to configure hotlink protection for a bucket:

using Aliyun.OSS;
using Aliyun.OSS.Common;
// Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. 
var endpoint = "yourEndpoint";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. 
var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
// Specify the name of the bucket. 
var bucketName = "examplebucket";
// Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou.
const string region = "cn-hangzhou";

// Create a ClientConfiguration instance and modify the default parameters based on your requirements.
var conf = new ClientConfiguration();

// Use the signature algorithm V4.
conf.SignatureVersion = SignatureVersion.V4;

// Create an OSSClient instance.
var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
c.SetRegion(region);
try
{
    var refererList = new List<string>();
    // Add a Referer whitelist. You can use asterisks (*) and question marks (?) as wildcard characters in Referers. 
    refererList.Add("http://www.aliyun.com");
    refererList.Add("https://www.aliyun.com");
    // refererList.Add("http://www.help.alibabacloud.com");
    // refererList.Add("http://www.?.aliyuncs.com");
    var srq = new SetBucketRefererRequest(bucketName, refererList);
    // Configure hotlink protection. 
    client.SetBucketReferer(srq);
    Console.WriteLine("Set bucket:{0} Referer succeeded ", bucketName);
}
catch (OssException ex)
{
    Console.WriteLine("Failed with error code: {0}; Error info: {1}. \nRequestID:{2}\tHostID:{3}",
        ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId);
}
catch (Exception ex)
{
    Console.WriteLine("Failed with error info: {0}", ex.Message);
}

Query hotlink protection configurations

The following sample code provides an example on how to query the hotlink configurations of a bucket:

using Aliyun.OSS;
using Aliyun.OSS.Common;
// Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. 
var endpoint = "yourEndpoint";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. 
var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
// Specify the name of the bucket. 
var bucketName = "examplebucket";
// Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou.
const string region = "cn-hangzhou";

// Create a ClientConfiguration instance and modify the default parameters based on your requirements.
var conf = new ClientConfiguration();

// Use the signature algorithm V4.
conf.SignatureVersion = SignatureVersion.V4;

// Create an OSSClient instance.
var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
c.SetRegion(region);
try
{
    // Query the hotlink protection configurations of the bucket. 
    var rc = client.GetBucketReferer(bucketName);
    Console.WriteLine("Get bucket:{0} Referer succeeded ", bucketName);
    Console.WriteLine("allow?" + (rc.AllowEmptyReferer ? "yes" : "no"));
    if (rc.RefererList.Referers != null)
    {
        for (var i = 0; i < rc.RefererList.Referers.Length; i++)
            Console.WriteLine(rc.RefererList.Referers[i]);
    }
    else
    {
        Console.WriteLine("Empty Referer List");
    }
}
catch (OssException ex)
{
    Console.WriteLine("Failed with error code: {0}; Error info: {1}. \nRequestID:{2}\tHostID:{3}",
        ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId);
}
catch (Exception ex)
{
    Console.WriteLine("Failed with error info: {0}", ex.Message);
}
finally
{
    client.SetBucketReferer(new SetBucketRefererRequest(bucketName));
}

Clear the hotlink protection configurations of a bucket

The following sample code provides an example on how to delete the hotlink protection configurations of a bucket:

using Aliyun.OSS;
using Aliyun.OSS.Common;
// Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. 
var endpoint = "yourEndpoint";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. 
var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
// Specify the name of the bucket. 
var bucketName = "examplebucket";
// Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou.
const string region = "cn-hangzhou";

// Create a ClientConfiguration instance and modify the default parameters based on your requirements.
var conf = new ClientConfiguration();

// Use the signature algorithm V4.
conf.SignatureVersion = SignatureVersion.V4;

// Create an OSSClient instance.
var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
c.SetRegion(region);
try
{
    // The hotlink protection configurations of a bucket cannot be directly cleared. To overwrite the existing hotlink protection configurations, you must configure a new hotlink protection rule that allows requests with an empty Referer header. 
    var srq = new SetBucketRefererRequest(bucketName);
    client.SetBucketReferer(srq);
    Console.WriteLine("Set bucket:{0} Referer succeeded ", bucketName);
}
catch (OssException ex)
{
    Console.WriteLine("Failed with error code: {0}; Error info: {1}. \nRequestID:{2}\tHostID:{3}",
        ex.ErrorCode, ex.Message, ex.RequestId, ex.HostId);
}
catch (Exception ex)
{
    Console.WriteLine("Failed with error info: {0}", ex.Message);
}

References

• For the complete sample code of hotlink protection, visit GitHub.

• For more information about the API operation that you can call to configure hotlink protection for a bucket, see PutBucketReferer.

• For more information about the API operation that you can call to query the hotlink protection configurations of a bucket, see GetBucketReferer.