Creating and applying a bucket policy

A bucket policy is a resource-based policy option. It allows you to grant more granular access to Object Storage resources.

By default, all Object Storage resources in a Project are private and can be accessed only by users or applications with IAM permissions. Adding a bucket policy to a bucket allows you to specify who can perform which actions on a bucket and the objects it contains. You can combine the different elements of a bucket policy to tailor your permissions according to your use case.

To create and apply a bucket policy from the Scaleway console, refer to the dedicated documentation.

Before you start

To complete the actions presented below, you must have:

• A Scaleway account logged into the console
• Owner status or IAM permissions allowing you to perform actions in the intended Organization
• An Object Storage bucket
• Installed the AWS CLI
• An IAM policy to grant access to your users and applications

How to create a bucket policy

1. Create a bucket-policy.json file.

2. Open it in a code editor and paste the code below inside. This sample bucket policy contains a statement that only allows the specified user to see the bucket and the objects it contains.

   {
       "Version": "2023-04-17",
       "Id": "MyBucketPolicy",
       "Statement": [
           {
               "Sid": "DelegateAccess",
               "Effect": "Allow",
               "Principal": {
                   "SCW": "user_id:<USER_ID>"
               },
               "Action": [
                   "s3:ListBucket",
                   "s3:GetObject"
               ],
               "Resource": [
                   "<BUCKET_NAME>",
                   "<BUCKET_NAME>/*"
               ]
           }
       ]
   }
   

3. Replace the <USER_ID> placeholder with the ID of the user to which you want to grant access. You can also grant access to an application.

4. Replace the <BUCKET_NAME> placeholders with the name of the concerned bucket. Refer to the resource documentation for more information.

How to apply a bucket policy

Make sure that you have installed the AWS CLI before proceeding.

1. Open a terminal and access the folder containing the previously created bucket-policy.json file.

2. Run the command below to apply the policy. Make sure to replace <BUCKET_NAME> with the name of your bucket.

   aws s3api put-bucket-policy --bucket <BUCKET_NAME> --policy file://bucket-policy.json
   

   Important

   • You will lose access to your bucket if you are not the owner of the Organization, and if you are not explicitly allowed by the bucket policy.
   • The owner of the Organization always has the right to put and delete bucket policies, even if he is not allowed to perform other bucket operations by the bucket policy.
   • Each bucket can have only one bucket policy.
   • Pushing a new bucket policy to a bucket overwrites any existing bucket policy.

3. Run the command below to display the bucket policy applied to your bucket.

   aws s3api get-bucket-policy --bucket <BUCKET_NAME> --query Policy --output text | jq
   

   An output similar to the following displays:

   {
     "Version": "2023-04-17",
     "Id": "MyBucketPolicy",
     "Statement": [
       {
         "Sid": "DelegateAccess",
         "Effect": "Allow",
         "Action": [
           "s3:ListBucket",
           "s3:GetObject"
         ],
         "Principal": {
           "SCW": "user_id:f3e2-example-8e51-0fd3299d5d70"
         },
         "Resource": [
           "my-bucket",
           "my-bucket/*"
         ]
       }
     ]
   }
   

How to delete a bucket policy

Run the command below to delete the policy of a specific bucket. Replace <BUCKET_NAME> with the name of your bucket.

aws s3api delete-bucket-policy --bucket <BUCKET_NAME>