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 defines the length of time an object remains locked. During this period, the object is protected and cannot be modified or deleted. Retention can be defined in days or years, with a minimum of one day and no maximum limit.

When defining a retention period for a bucket or its objects, you must choose the retention mode to apply: Governance or Compliance.

Governance mode

Governance mode prevents most users from deleting or modifying objects during the retention period, while allowing certain users with specific rights to manage retention or delete objects.

Authorized users with s3:BypassGovernanceRetention can thus replace or delete objects in Governance mode.

Compliance mode

Compliance mode ensures that objects cannot be modified or deleted by any user, including administrators, during the entire retention period.

Once this mode is enabled for an object, its retention mode and duration cannot be changed.

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

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

aws s3api create-bucket \
  --bucket object-lock-bucket \
  --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 }}}'

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

{
  "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"
  }
}

Object Lock and Object Deletion

When versioning is enabled, deleting an object does not delete the object immediately but creates a delete marker. This marker becomes the current version of the object with a new ID.

A delete marker:

• Has a key and version ID like any other object.
• Does not contain data (GET returns 404).
• Is not displayed by default in the Control Panel.
• Can only be manipulated by DELETE, by the bucket owner.

The Object Lock feature prevents objects from being:

• deleted even with a version ID (returns Access Denied).
• overwritten by versioning.

How deletions work with Object Lock

When Object Lock is enabled and an object is protected by a retention period or legal hold, deletion attempts behave differently depending on the type of request:

aws s3api delete-object --bucket my-bucket --key an-object --version-id 123456huijw0

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