Object Storage - Managing object immutability with Object Lock (WORM)

Objective

Object Lock is a feature that allows you to store objects using a Write Once, Read Many (WORM) model and can be used for scenarios where it is imperative that data is not changed or deleted after it has been written.

This guide explains how to manage Object Lock

Concept

Object Lock provides two ways to manage object retention. The first is retention periods and the second is Legal hold.

How does Object Lock work?

To understand how Object Lock works, you first need to understand how deletion of objects and versioning work together. When a delete object operation is performed on an object in a versioning-enabled bucket, it does not delete the object permanently but it creates a delete marker on the object. This delete marker becomes the latest and current version of the object with a new version ID.

A delete marker has the following properties:

• A key and version ID like any other object.
• It does not have data associated with it, thus it does not retrieve anything from a GET request (you get a 404 error).
• By default, it is not displayed in the Control Panel UI anymore.
• The only operation you can use on a delete marker is DELETE, and only the bucket owner can issue such a request.

To permanently delete an object, you have to specify the version-id in your delete object request:

aws s3api delete-object --bucket <bucket_name> --key <object_key> --version-id <version_id>

The Object Lock feature prevents objects, for a fixed amount of time (retention mode) or indefinitely (legal hold), from being:

• deleted even if you specify the version ID (you get an Access Denied error);
• overwritten by using versioning.

Retention periods

A retention period specifies a fixed period of time during which an object remains locked. During this period, your object is protected and can’t be overwritten or deleted. You apply a retention period either in number of days or number of years with the minimum being 1-day and no maximum limit.

When setting a retention period for your objects or buckets, you can choose the retention mode you wish to apply to your objects. You can choose either the Governance mode or the Compliance mode for your objects.

Governance mode

You should use the Governance mode if you want to protect objects from being deleted by most users during a pre-defined retention period, while authorising some users with special permissions to have the flexibility to alter the retention settings or delete the objects. Users with the s3:BypassGovernanceRetention permission can override or remove governance-mode retention settings.

Compliance mode

You should use the Compliance mode if you have a requirement to store compliant data. When this mode is set, an object version cannot be overwritten or deleted by any user. If this mode is configured for an object, then its retention mode cannot be changed, and its retention period can’t be shortened.

Legal hold

Designed for any situation where you are not sure for how long you want your objects to stay immutable, Legal hold is an ON/OFF switch that can be applied to every object in a locked bucket, independently from the lock configuration, the object retention or the object age. It can be applied to objects which are locked.

Legal hold provides the same protection as a retention period, but it has no expiration date. Instead, a Legal hold remains in place until you explicitly remove it.

Requirements

• Your Object Storage credentials (access_key and secret_access_key)
• AWS CLI installed and configured

See our Getting started with Object Storage guide for more information.

Instructions

Permissions

Read this guide to learn more about IAM.

Object Lock configuration

To use Object Lock, you have to create a bucket that supports the feature with the --object-lock-enabled-for-bucket flag. If a bucket is created without --object-lock-enabled-for-bucket, the flag cannot be added later.

aws s3api create-bucket \
  --bucket <bucket_name> \
  --object-lock-enabled-for-bucket

How to configure Object Lock on bucket

The lock configuration enables you to set a lock configuration on a specified bucket. Once set, the rule specified in the Object Lock configuration is applied by default to every new object placed in the specified bucket.

aws s3api put-object-lock-configuration \
  --bucket <bucket_name> \
    --object-lock-configuration '{ "ObjectLockEnabled": "Enabled", "Rule": { "DefaultRetention": { "Mode": "GOVERNANCE", "Days": 60 }}}'

To view the Object Lock configuration of a bucket, run:

aws s3api get-object-lock-configuration \
  --bucket <bucket_name>

The result should look like this:

{
  "ObjectLockConfiguration": {
    "ObjectLockEnabled": "Enabled",
    "Rule": {
      "DefaultRetention": {
        "Mode": "GOVERNANCE",
        "Days": 60
      }
    }
  }
}

How to configure an Object Lock retention period on an object

To set an object retention configuration on an object:

aws s3api put-object-retention \
  --bucket <bucket_name> \
  --key <object_key> \
  --retention '{"Mode":"COMPLIANCE","RetainUntilDate":"2023-01-01T12:00:00.00Z"}'

To view the Object Lock retention configuration of an object, run:

aws s3api get-object-retention \
  --bucket <bucket_name> \
  --key <object_key>

The result should look like this:

{
  "Retention": {
  "Mode": "COMPLIANCE",
  "RetainUntilDate": "2023-01-01T12:00:00Z"
  }
}

Bypassing Governance mode

To bypass governance mode, you must explicitly indicate in your request that you want to bypass this mode. To do this, include the --bypass-governance-retention header with your request:

aws s3api delete-object \
  --bucket <bucket_name> \
  --key <object_key> \
  --bypass-governance-retention

How to configure an Object Lock Legal hold on an object

To set a Legal hold configuration to the specified object:

aws s3api put-object-legal-hold \
  --bucket <bucket_name> \
  --key <object_key> \
  --legal-hold Status=ON

To view the Object Lock Legal hold configuration of an object, run:

aws s3api get-object-legal-hold \
  --bucket <bucket_name> \
  --key <object_key>

The result should look like this:

{
  "LegalHold": {
    "Status": "ON"
  }
}

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