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Dynamic permissions

Openchain supports an implicit permission layout through :ref:`P2PKH accounts <p2pkh-accounts>` (/p2pkh/<address>/) and :ref:`thrid party issuance accounts <third-party-issuance-accounts>` (/asset/p2pkh/<address>/). It is also possible to dynamically define permissions by submitting transactions modifying a special record: the acl record.

Access Control Lists

Permissions are applied to a specific path. To apply an access control list to a path, set the acl record under that path. It must be a DATA record. The value is a JSON file.

For example, when trying to set the permissions to the path /users/alice/, the following record must be set: /users/alice/:DATA:acl.

Schema

The schema of the JSON file that the record contains is the following:

[
    {
        "subjects": [
            {
                "addresses": [ "<string>" ],
                "required": <integer>
            }
        ],
        "recursive": <boolean>,
        "record_name": "<string>",
        "record_name_matching": "<record-matching-type>",
        "permissions": {
            "account_negative": "<permission>",
            "account_spend": "<permission>",
            "account_modify": "<permission>",
            "account_create": "<permission>",
            "data_modify": "<permission>"
        }
    }
]

The contents is an array containing all the applicable permissions. When the acl record does not exist, this is equivalent to having an empty array.

The meaning of the fields within a permission object are the following:

  • subjects: An array of subjects for which this permission object applies.

    • addresses: An array of strings representing the addresses for which signatures are expected.
    • required: The number of required signatures from the addresses array. If the addresses array contains 3 addresses, and required is set to 2, that means that for the permission to apply, at least 2 signatures from the 3 addresses specified must be present. This is known as a n-of-m multi-signature scheme.
  • recursive: (Default: true) A boolean indicating whether the permission applies recursively to the sub accounts.

    Note

    With recursion, lower level permissions overrule higher level permissions.

  • record_name: (Default: empty string) The pattern to use for record name matching.

  • record_name_matching: (Default: Prefix) The type of record name matching to use. There are two possible values:

    • Exact means that the record name must be exactly equal to the value of the record_name field for the permission to apply.
    • Prefix means that the record name must start with the value of the record_name field for the permission to apply. Using Prefix with an empty record_name means that the permission applies to all records.

    Hint

    The record name of an ACC record is the asset path.

  • permissions: Contains the permissions being applied if this permission object is a match. The meaning of the various permissions is explained in the next section. The value must be set to Permit for the permission to be granted, or Deny for the permission to be denied. If it is unset, the inherited value is used.

Permissions

account_negative

This permission indicates the right to affect the balance of ACC records, both to increase it (receive funds) and decrease it (send funds) with no restriction on the final balance. If this permission is granted, the ACC record balance can be made negative.

This permission is typically granted to the users allowed to issue an asset.

account_spend

This permission indicates the right to affect the balance of ACC records, both to increase it (receive funds) and decrease it (send funds) with the restriction that the final balance must remain positive or zero.

account_modify

This permission is required to affect the balance of ACC records that have already been modified before (the record version is non-empty).

account_create

This permission is required to affect the balance of ACC records that have never been modified before (the record version is empty).

Note

A user can only send funds from an account if she has the account_negative or account_spend rights plus the account_modify or account_create rights. Sending to an account requires account_modify or account_create on the destination account.

A closed loop ledger can be created by denying account_modify and account_create by default, and selectively granting these for some accounts. By doing this, only approved accounts can receive funds.

data_modify

This permission is required to modify a DATA record.