# Structure of delegation evidence *This part of the iSHARE Trust Framework is considered normative and is therefore compliant with RFC 2119.* This page describes (and prescribes) how, in data spaces/iSHARE network, delegation is communicated between different parties. In data spaces/iSHARE network, delegation evidence expresses the delegation of rights from a delegator (the party that delegates rights; the `policyIssuer`) to the delegate (the party that receives the delegated rights; i.e. the `accessSubject`). Rights are expressed in `rules` in terms of allowed `actions` to be performed on resources, under the `license(s)` as defined in `policySets`. Delegation evidence is modelled as a JSON object inspired by the XACML 3.0 specifications and structured as follows:
The JSON object consists of a root `delegationEvidence` element (modeled after an XACML `PolicySet` element) containing one or more `policySet` objects in the `policySets` array. The root element is only meant as a container element and extends the XACML specifications to cater for some iSHARE required metadata such as timestamps. Each of the second level `policySet` elements only acts as a container for actual `policy` elements with an indication of the rights in this `policySet` can be further delegated (with `maxDelegationDepth`) and what `license`(s) do apply. No other delegation logic is conveyed a second level `policySet`. Each `policy` element is used to express the actual rights being delegated. \\ The root `delegationEvidence` element contains the following parameters. | Parameter | Contained in | Type | Required | Description | | -------------------- | -------------------- | ------ | ---------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `delegationEvidence` |


| { } | Yes | The root of any delegation evidence | | `notBefore` | `delegationEvidence` | int | Yes | Unix timestamp in UTC indicating the start of validity period of this delegation evidence. SHOULD equal the time of issuing of the evidence unless historic evidence is requested. | | `notOnOrAfter` | `delegationEvidence` | int | Yes | Unix timestamp in UTC indicating the end of validity period of this delegation evidence. It is up to the issuer off the evidence to set this time. Note that a reasonable amount of time SHOULD be allowed for processing of longer delegation paths. Also note that evidence cannot be revoked, so setting very long validity periods SHOULD be avoided. | | `policyIssuer` | `delegationEvidence` | string | Yes | iSHARE identifier of the delegator (the delegating entity) | | `target` | `delegationEvidence` | { } | Yes | MUST for the root level contain an `accessSubject`. No other elements are allowed. It makes the entire delegation evidence applicable only to this `accessSubject`. | | `accessSubject` | `target` | string | Yes | iSHARE identifier of the delegate (the entity that receives the delegated rights) | | `policySets` | `delegationEvidence` | \[ ] | Yes (1..n) | Container for one or more objects containing `policy` elements with an indication for further delegation. Note that `policySet` elements within one `delegationEvidence` MUST not restrict each other, but rather offer a mechanism to express additional rights. They MUST be evaluated in a "permit-override" manner, allowing a "Permit" if only one of the `policySet` elements evaluates to "Permit". | The second level objects in `policySets` each contain the following parameters. Other parameters are not allowed. Note that XACML spec is heavily restricted, a.o. for the reason to prevent redundancy (and resulting possible conflicts) with the root `policySet` element. | Parameter | Contained in | Type | Required | Description | | -------------------- | ------------- | ---- | ---------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `maxDelegationDepth` | `policySets` | int | No | Optional element that, if present, indicates that further delegation of the rights, conveyed in the `policy` elements that are part of this `PolicySet`, is allowed. The value indicates the delegation steps that are allowed after this step in order to evaluate the entire delegation path to "Permit" | | `target` | `policySet` | { } | Yes |


| | `environment` | `target` | { } | Yes |


| | `licenses` | `environment` | \[ ] | Yes | Array which describes which iSHARE licenses apply to this `policySet`. | | `policies` | `policySets` | \[ ] | Yes (1..n) | Used to express the actual rights being delegated. Note that `policies` within one `policySets` object MUST not restrict each other, but rather offer a mechanism to express additional rights. They MUST be evaluated in a "permit-override" manner, allowing a "Permit" if only one of the `policy` elements evaluates to "Permit". | A `Policy` element contains the following parameters. | Parameter | Contained in | Type | Required | Description | | ------------------ | ------------- | ------ | ---------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `target` | `policies` | string | Yes | Describes the target, in terms of resource and action, this policy applies to. It is also the scope that is permitted through the default Rule. Additional Rule elements can be described to exclude Resources and Actions from the default `policy` rights | | `resource` | `target` | { } | Yes |


| | `type` | `resource` | string | Yes | String which describes the type of resource to which the rules apply. | | `identifiers` | `resource` | \[ ] | Yes | Array of strings containing one or more resource identifiers. Depending on the `Type` an `identifier` SHOULD be a urn. | | `attributes` | `resource` | \[ ] | No | Optional array of attributes of the resources the delegated rights apply to. If omitted defaults to all attributes. Depending on the `Type` an `attribute` SHOULD be a urn. | | `actions` | `target` | \[ ] | Yes |


| | `environment` | `target` | { } | No |


| | `serviceProviders` | `environment` | \[ ] | Yes | Array which lists the iSHARE client ID's of `serviceProviders` which are allowed to provide services to the `accessSubject` as described within this `policy`. | | `rules` | `policies` | \[ ] | Yes (1..n) | The first `rule` element is the default `rule` that applies to the `target` at `policies` level. Note that additional `rule` elements within one `policies` object are intended to restrict each the default `rule`. All `rule` elements in a Policy MUST be evaluated in a "deny-override" manner, allowing a "Permit" only if all of the `rule` elements evaluate to "Permit". | The default `Rule` element contains the following parameters. | Parameter | Contained in | Type | Required | Description | | --------- | ------------ | ------ | -------- | --------------------- | | `effect` | `rules` | string | Yes | MUST contain 'Permit' | Additional `Rule` elements contains the following parameters. | Parameter | Contained in | Type | Required | Description | | ------------- | ------------ | ------ | -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | `effect` | `rules` | string | Yes | MUST contain 'Deny' | | `target` | `rules` | { } | Yes | Describe the target, in terms of resource and action, this additional `rule` applies to. Additional `rule` elements are limitations of the default `rule` and `resource` scope. | | `resource` | `target` | { } | Yes |


| | `type` | `resource` | string | No\* | Optional string which describes the type of resource to which the rule applies. Defaults to none if not specified. | | `identifiers` | `resource` | \[ ] | No\* | Optional array of strings containing one or more resource identifiers. Depending on the `type` an `identifier` SHOULD be a urn. | | `attributes` | `resource` | \[ ] | No\* | Optional array of attributes of the resources the delegated rights apply to. If omitted defaults to all attributes. Depending on the `type` an `attribute` SHOULD be a urn. | | `actions` | `target` | \[ ] | No | Optional array of `actions`, the additional `rule` applies to the `actions` listed. If no `actions` are listed then the default is to all iSHARE actions defined within the `policy`. | \* Note: Although not individually required, at least one of the parameters within the `resource` object needs to be specified to which the additional `rules` apply. Example delegation JSON: ```json //Organisation A delegates rights to organisation B. A allows B READ and CREATE access to all ETA and WEIGHT of A's containers of which the data is located at service provider C and can only be accessed with service provider C. However, A does not allow B to CREATE to ETA information and completely denies access to data regarding container ID.00000000000001. Furthermore, all rights of B are allowed under iSHARE licenses 1 and 3, and B has the right to delegate it's right two more times. { "delegationEvidence": { "notBefore": 1509633681, "notOnOrAfter": 1509633741, "policyIssuer": "EU.EORI.NL123456789", "target": { "accessSubject": "EU.EORI.NL012345678" }, "policySets": [ { "maxDelegationDepth": 2, "target": { "environment": { "licenses": ["ISHARE.0001", "ISHARE.0003"] } }, "policies": [ { "target": { "resource": { "type": "GS1.CONTAINER", "identifiers": ["*"], "attributes": ["GS1.CONTAINER.ATTRIBUTE.ETA", "GS1.CONTAINER.ATTRIBUTE.WEIGHT"] }, "actions": ["ISHARE.READ", "ISHARE.CREATE"], "environment": { "serviceProviders": ["EU.EORI.NL123412345"] } }, "rules": [ { "effect": "Permit" }, { "effect": "Deny", "target": { "resource": { "attributes": ["GS1.CONTAINER.ATTRIBUTE.ETA"] }, "actions": ["ISHARE.CREATE"] } }, { "effect": "Deny", "target": { "resource": { "identifiers": ["GS1.CONTAINER.ID.00000000001"] } } } ] } ] } ] } } ``` example code - for copying purposes ```json {"delegationEvidence":{"notBefore":1509633681,"notOnOrAfter":1509633741,"policyIssuer":"EU.EORI.NL123456789","target":{"accessSubject":"EU.EORI.NL012345678"},"policySets":[{"maxDelegationDepth":2,"target":{"environment":{"licenses":["ISHARE.0001","ISHARE.0003"]}},"policies":[{"target":{"resource":{"type":"GS1.CONTAINER","identifiers":["*"],"attributes":["GS1.CONTAINER.ATTRIBUTE.ETA","GS1.CONTAINER.ATTRIBUTE.WEIGHT"]},"actions":["ISHARE.READ","ISHARE.CREATE"],"environment":{"serviceProviders":["EU.EORI.NL123412345"]}},"rules":[{"effect":"Permit"},{"effect":"Deny","target":{"resource":{"attributes":["GS1.CONTAINER.ATTRIBUTE.ETA"]},"actions":["ISHARE.CREATE"]}},{"effect":"Deny","target":{"resource":{"identifiers":["GS1.CONTAINER.ID.00000000001"]}}}]}]}]}} ``` Please note that although in XACML the attributes PolicySetId, Version and PolicyCombiningAlgId are mandatory in XACML they are not ported to the iSHARE JSON structure. iSHARE Trust Framework follows the "**deny-override"** Policy Combining Algorithm. This implies that if at least one policy is evaluated as “deny”, the integrated output must also be “deny”.