Bucket policy

Object Storage incorporates multiple mechanisms for managing access to resources. To learn how these mechanisms interact, see Access management methods in Object Storage: Overview.

Bucket policies set permissions for actions with buckets, objects, and object groups.

A policy is triggered when a user makes a request to a resource. As a result, the request is either executed or rejected.

Enabling public access to bucket operations does not override the restrictions set in the access policies.

You can set up a bucket policy in the management console or describe it in JSON format using a special scheme to provide the settings through one of the software tools: the Yandex Cloud CLI, AWS CLI, Terraform, or API. To learn more about policy management, see this guide.

If you want to assign an access policy to a bucket and connect to it from a Hive Metastore or Yandex Managed Service for Apache Airflow™ cluster, you will need some additional infrastructure setup. For more information, see these guides for Metastore and Managed Service for Apache Airflow™.

Policy componentsPolicy components

A bucket policy consists of rules, a rule consisting of the following basic elements:

Resource

Bucket, object in a bucket (<bucket_name>/some/key), or prefix (<bucket_name>/some/path/*), including an empty prefix to indicate all bucket objects (<bucket_name>/*). You can specify multiple resources in a rule.

Note

A bucket resource does not include resources of all its objects. To make sure a bucket policy rule refers to the bucket and all objects, specify them as separate resources, such as samplebucket and samplebucket/*.

If you describe a policy in JSON format, a resource must have the arn:aws:s3::: prefix, e.g., arn:aws:s3:::<bucket_name>.

If the resource name contains ?, *, or $, enclose each one of these characters in curly braces ({}) preceded with $. For example, a record mapped to a bucket named my?bucket will read my${?}bucket.

Action

Operations with a resource that will be either denied or allowed by the rule. For more information, see Actions.

Result

Denies or allows the requested action. First, the request is checked against the Deny action filter. If there is a match, the request is rejected and no further checks are performed. If it meets the Allow action filter criteria, the request is allowed. If the request does not trigger any of the filters, it is rejected.

Principal

Grantee of the requested permission. It can be an IAM user, federated user, service account, anonymous user, or user group. You can specify a user group in the policy using the Yandex Cloud CLI, AWS CLI, Terraform, and the API.

Condition

Establishes the cases in which the rule will apply.

Note

The aws:sourceip condition supports a special procedure for verifying reverse proxy server IP addresses.

If multiple conditions are specified simultaneously for a rule or multiple keys are specified simultaneously within a single condition, then such conditions and keys will apply with the AND logic.

If multiple values are specified simultaneously for one condition key, such values will apply with the OR logic.

For more information, see Conditions.

Bucket access via the management consoleBucket access via the management console

If a bucket has an access policy configured, access to the bucket via the Yandex Cloud management console is disabled by default. To enable bucket access, you need to add a rule in the Statement section to allow any requests to <bucket_name>/* or <bucket_name> from the management console.

Example of a rule for a specific Yandex Cloud user:

{
  "Effect": "Allow",
  "Principal": {
    "CanonicalUser": "<user_ID>"
  },
  "Action": "*",
  "Resource": [
    "arn:aws:s3:::<bucket_name>/*",
    "arn:aws:s3:::<bucket_name>"
  ],
  "Condition": {
    "StringLike": {
      "aws:referer": "https://console.yandex.cloud/folders/*/storage/buckets/your-bucket-name*"
    }
  }
}

{
  "Effect": "Allow",
  "Principal": {
    "CanonicalUser": "<user_ID>"
  },
  "Action": "*",
  "Resource": [
    "arn:aws:s3:::<bucket_name>/*",
    "arn:aws:s3:::<bucket_name>"
  ],
  "Condition": {
    "StringLike": {
      "aws:referer": [
        "https://console.cloud.yandex.*/folders/*/storage/buckets/your-bucket-name*",
        "https://console.yandex.cloud/folders/*/storage/buckets/your-bucket-name*"
      ]
    }
  }
}

You can retrieve the user ID by following this guide in the Yandex Identity and Access Management documentation.

Bucket access via a chain of reverse proxy serversBucket access via a chain of reverse proxy servers

For Object Storage to work with requests sent over a series of reverse proxy servers, the aws:sourceip condition checks both the IP address the request came from and the IP addresses of reverse proxy servers, e.g., those provided in the X-Forwarded-For header.

First a request is checked against the Deny access policy rules. If at least one IP address meets the Deny rule criteria, the request is denied. No further checks are performed.

Then the request is checked against the Allow access policy rules. If at least one IP address meets the Allow rule criteria, the request is allowed.

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "the-allowing-rule",
      "Effect": "Allow",
      "Principal": "*",
      "Action": "*",
      "Resource": "arn:aws:s3:::sample-bucket/*",
      "Condition": {
        "IpAddress": {
          "aws:sourceip": [
            "192.168.1.1",
            "192.168.1.2"
          ]
        }
      }
    },
    {
      "Sid": "the-denying-rule",
      "Effect": "Deny",
      "Principal": "*",
      "Action": "*",
      "Resource": "arn:aws:s3:::sample-bucket/*",
      "Condition": {
        "IpAddress": {
          "aws:sourceip": [
            "192.168.1.11",
            "192.168.1.12"
          ]
        }
      }
    }
  ]
}

Configuration examplesConfiguration examples

• Rule that allows an anonymous user to read objects in the bucket over an encrypted connection:

  {
    "Id": "epd4limdp3dg********",
    "Version": "2012-10-17",
    "Statement": [
      {
        "Sid": "f1qqoehl1q53********",
        "Effect": "Allow",
        "Principal": "*",
        "Action": "s3:GetObject",
        "Resource": "arn:aws:s3:::<bucket_name>/*",
        "Condition": {
          "Bool": {
            "aws:SecureTransport": "true"
          }
        }
      }
    ]
  }
  

• Rule that allows downloading objects only from a specified range of IP addresses:

  {
    "Version": "2012-10-17",
    "Statement": [
      {
        "Effect": "Allow",
        "Principal": "*",
        "Action": "s3:GetObject",
        "Resource": "arn:aws:s3:::<bucket_name>/*",
        "Condition": {
          "IpAddress": {
            "aws:SourceIp": "100.101.102.128/30"
          }
        }
      }
    ]
  }
  

• Rule that prohibits downloading objects from the specified IP address:

  {
    "Version": "2012-10-17",
    "Statement": [
      {
        "Effect": "Allow",
        "Principal": "*",
        "Action": "*",
        "Resource": "arn:aws:s3:::<bucket_name>/*"
      },
      {
        "Effect": "Deny",
        "Principal": "*",
        "Action": "s3:GetObject",
        "Resource": "arn:aws:s3:::<bucket_name>/*",
        "Condition": {
          "IpAddress": {
            "aws:SourceIp": "100.101.102.103"
          }
        }
      }
    ]
  }
  

• Rule that provides different users with full access only to specific folders – each user to their own:

  {
    "Version":"2012-10-17",
    "Statement":[
      {
        "Sid":"User1PermissionsResource",
        "Effect":"Allow",
        "Principal": {
          "CanonicalUser": "<user_ID>"
        },
        "Action": "*",
        "Resource":["arn:aws:s3:::<bucket_name>/user1path/*"]
      },
      {
        "Sid":"User1PermissionsPrefix",
        "Effect":"Allow",
        "Principal": {
            "CanonicalUser": "<user_ID>"
        },
        "Action": "s3:ListBucket",
        "Resource":["arn:aws:s3:::<bucket_name>"],
        "Condition": {
          "StringLike": {
            "s3:prefix": "user1path/*"
          }
        }
      },
      {
        "Sid":"User2PermissionsResource",
        "Effect":"Allow",
        "Principal": {
          "CanonicalUser": "<user_ID>"
        },
        "Action": "*",
        "Resource":["arn:aws:s3:::<bucket_name>/user2path/*"]
      },
      {
        "Sid":"User2PermissionsPrefix",
        "Effect":"Allow",
        "Principal": {
          "CanonicalUser": "<user_ID>"
        },
        "Action": "s3:ListBucket",
        "Resource":["arn:aws:s3:::<bucket_name>"],
        "Condition": {
          "StringLike": {
            "s3:prefix": "user2path/*"
          }
        }
      }
    ]
  }
  

• Rule that provides each user and service account with full access to a folder with the name matching the user ID or service account ID:

  {
    "Version":"2012-10-17",
    "Statement":[
      {
        "Sid": "OwnDirPermissions",
        "Effect": "Allow",
        "Principal": "*",
        "Action": "*",
        "Resource": ["arn:aws:s3:::<bucket_name>/${aws:userid}/*"]
      }
    ]
  }
  

See alsoSee also

• Bucket policy management