Use C++ to configure a bucket policy to grant or deny user access to OSS - Object Storage Service

A bucket policy is an authorization policy that Object Storage Service (OSS) provides for buckets. You can use a bucket policy to grant or deny fine-grained access to specified OSS resources for authenticated users, such as Alibaba Cloud accounts, Resource Access Management (RAM) users, and RAM roles, or for anonymous visitors. For example, you can grant read-only permissions on specified OSS resources to a RAM user that belongs to another Alibaba Cloud account.

Usage notes

Make sure you understand bucket policies before you configure one. For more information, see Bucket Policy.

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 by using custom domain names or Security Token Service (STS), see Create an OSSClient instance.
To set a bucket policy, you must have the oss:PutBucketPolicy permission. To get a bucket policy, you must have the oss:GetBucketPolicy permission. To delete a bucket policy, you must have the oss:DeleteBucketPolicy permission. For more information, see Attach a custom policy to a RAM user.

Set a bucket policy

Below is the sample code for setting a bucket policy:

#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

int main(void)
{
    /* Initialize OSS account information. */
            
    /* Set yourEndpoint to the Endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set yourRegion to the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Region to cn-hangzhou. */
    std::string Region = "yourRegion";
    /* Specify the bucket name. For example, examplebucket. */
    std::string BucketName = "examplebucket";

    /* Initialize network resources. */
    InitializeSdk();

    ClientConfiguration conf;
    conf.signatureVersion = SignatureVersionType::V4;
    /* Obtain access credentials from environment variables. Before you run this sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set. */
    auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
    OssClient client(Endpoint, credentialsProvider, conf);
    client.SetRegion(Region);

    /* The following example shows how a resource owner (the owner of the bucket with UID 174649585760xxxx) uses a bucket policy to grant a specified user (a RAM user with UID 20214760404935xxxx) the permissions to list all files in the examplebucket. */
    std::string policy = 
        R"(
        {
            "Statement": [
            {
                "Action": [
                    "oss:GetObject",
                    "oss:ListObjects"
                ],
                "Principal": [
                    "20214760404935xxxx"           
                ],
                "Effect" : "Allow",
                "Resource" : ["acs:oss:*:174649585760xxxx:examplebucket/*"]
            }
            ],
                "Version": "1"
        }
        )";
    SetBucketPolicyRequest request(BucketName);
    request.setPolicy(policy);
    auto outcome = client.SetBucketPolicy(request);

    if (!outcome.isSuccess()) {
        /* Handle the exception. */
        std::cout << "Set Bucket Policy fail" <<
            ",code:" << outcome.error().Code() <<
            ",message:" << outcome.error().Message() <<
            ",requestId:" << outcome.error().RequestId() << std::endl;
    }

    /* Release network resources. */
    ShutdownSdk();
    return 0;
}

Get a bucket policy

Below is the sample code for getting a bucket policy:

#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

int main(void)
{
    /* Initialize OSS account information. */
            
    /* Set yourEndpoint to the Endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set yourRegion to the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Region to cn-hangzhou. */
    std::string Region = "yourRegion";
    /* Specify the bucket name. For example, examplebucket. */
    std::string BucketName = "examplebucket";

    /* Initialize network resources. */
    InitializeSdk();

    ClientConfiguration conf;
    conf.signatureVersion = SignatureVersionType::V4;
    /* Obtain access credentials from environment variables. Before you run this sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set. */
    auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
    OssClient client(Endpoint, credentialsProvider, conf);
    client.SetRegion(Region);

    /* Get the bucket policy configuration. */
    GetBucketPolicyRequest request(BucketName);
    auto outcome = client.GetBucketPolicy(request);

    if (!outcome.isSuccess()) {
        /* Handle the exception. */
        std::cout << "Get Bucket Policy fail" <<
            ",code:" << outcome.error().Code() <<
            ",message:" << outcome.error().Message() <<
            ",requestId:" << outcome.error().RequestId() << std::endl;
            return -1;
    }

    /* Print the configuration information. */
    std::cout << outcome.result().Policy() << std::endl;

    /* Release network resources. */
    ShutdownSdk();
    return 0;
}

Delete a bucket policy

Below is the sample code for deleting a bucket policy:

#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;

int main(void)
{
    /* Initialize OSS account information. */
            
    /* Set yourEndpoint to the Endpoint of the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
    std::string Endpoint = "yourEndpoint";
    /* Set yourRegion to the region where the bucket is located. For example, if the bucket is in the China (Hangzhou) region, set the Region to cn-hangzhou. */
    std::string Region = "yourRegion";
    /* Specify the bucket name. For example, examplebucket. */
    std::string BucketName = "examplebucket";

    /* Initialize network resources. */
    InitializeSdk();

    ClientConfiguration conf;
    conf.signatureVersion = SignatureVersionType::V4;
    /* Obtain access credentials from environment variables. Before you run this sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are set. */
    auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
    OssClient client(Endpoint, credentialsProvider, conf);
    client.SetRegion(Region);

    /* Delete the bucket policy. */
    DeleteBucketPolicyRequest request(BucketName);
    auto outcome = client.DeleteBucketPolicy(request);

    if (!outcome.isSuccess()) {
        /* Handle the exception. */
        std::cout << "Delete Bucket Policy fail" <<
            ",code:" << outcome.error().Code() <<
            ",message:" << outcome.error().Message() <<
            ",requestId:" << outcome.error().RequestId() << std::endl;
    }

    /* Release network resources. */
    ShutdownSdk();
    return 0;
}

References

For more information about the API operation to set a bucket policy, see PutBucketPolicy.
For more information about the API operation to retrieve a bucket policy, see GetBucketPolicy.
For more information about the API operation to delete a bucket policy, see DeleteBucketPolicy.