πŸŽ“ Sample: Patient can see their own data

What is this tutorial about

In this tutorial you will know how to manage user access to patient resources.

Prerequisites

To complete this tutorial you should install Postman and get access to the Aidbox Console (see here how to install your Aidbox instance) .

Once you access the Aidbox REST Console, load resources that you will need to work with policies:

POST /$import
​
id: patient_import
inputFormat: application/fhir+ndjson
contentEncoding: gzip
mode: bulk
inputs:
- resourceType: Client
url: https://storage.googleapis.com/aidbox-public/demo/client.ndjson.gz
- resourceType: User
url: https://storage.googleapis.com/aidbox-public/demo/user.ndjson.gz
- resourceType: Patient
url: https://storage.googleapis.com/aidbox-public/demo/patient.ndjson.gz
- resourceType: Encounter
url: https://storage.googleapis.com/aidbox-public/demo/encounter.ndjson.gz
- resourceType: Observation
url: https://storage.googleapis.com/aidbox-public/demo/observation.ndjson.gz
- resourceType: Practitioner
url: https://storage.googleapis.com/aidbox-public/demo/practitioner.ndjson.gz

Structure of imported resources

On previous step we have imported a client that will authenticate users, and two users with corresponding sets of related resources shown on the picture below. Overlapping outlines means relation between enclosed resources. A similar diagram applies to User-2.

User Loginβ€Œ

Now you can use Postman to login as a user. In this example we login as User-1.

Request
Response
Request
POST /auth/token
​
{
"client_id": "myapp"
"client_secret": "verysecret"
"username": "patient-user"
"password": "admin"
"grant_type": "password"
}
Response
{
"token_type": "Bearer",
"userinfo": {
"data": {
"roles": ["Patient"],
"patient_id": "new-patient"
},
"resourceType": "User",
"id": "patient-user",
"meta": {
"lastUpdated": "2020-11-06T12:18:19.530001Z",
"createdAt": "2020-11-03T14:09:03.010136Z",
"versionId": "426"
}
},
"access_token": "MjYzOTkyZDEtODg4ZC00NTBlLTgxNDEtNjIzM2Y4NWQ1M2Vk"
}

Notice the patient_id field of userinfo . This is the id of the Patient resource associated with our user. It will be used further in Access Policies to decide if access should be granted or not. In general you need to specify data.patient_id: some_patient_id in your User resource to establish a relation with a Patient resource.β€Œ

The access-token field of user-info will be needed to perform requests on behalf of our User. See here how to perform user request with a token.

At this point there are no access policies that allow the user to access any resources. So all attempts to make requests for Resources will be denied.

Patient Resource access

Let's add out first policy that will grant us access to the Patient resource, associated with our user.

Request
Response
Request
POST /AccessPolicy
​
id: patient-access
engine: matcho
matcho:
uri: '#/Patient/.*'
params:
resource/id: .user.data.patient_id
request-method: get
Response
engine: matcho
matcho:
uri: '#/Patient/.*'
params:
resource/id: .user.data.patient_id
request-method: get
id: patient-access
resourceType: AccessPolicy
meta:
lastUpdated: '2020-11-10T15:00:59.497835Z'
createdAt: '2020-11-10T15:00:59.497835Z'
versionId: '110'

Here we specified that Access Policy will grant GET access to a URI that matches #/Patient/.* regex if the request parameter named resource/id matches data.patient value of the user that makes the request.β€Œ

So now we can read our patient. The part of the URL after /Patient/ namely new-patient is parsed by Access Policy engine as the resource/id parameter of the request:

Request
Response
Request
GET /Patient/new-patient
Response
{
"name": [
{
"given": ["Luke"]
},
{
"family": "Skywalker"
}
],
"gender": "male",
"birthDate": "2145-08-12",
"id": "new-patient",
"resourceType": "Patient",
"meta": {
"lastUpdated": "2020-11-10T13:51:16.780576Z",
"createdAt": "2020-11-10T11:38:52.402256Z",
"versionId": "83"
}
}

You can check that access to any other existing Patient resource, for instance that one with id new-patient1, will be denied.

Encounter access

Now let's give our user the ability to retrieve all encounters where they are referred to as a subject:

Request
Response
Request
POST /AccessPolicy
​
id: search-patient-encounter
engine: matcho
matcho:
uri: /Encounter
params:
patient: .user.data.patient_id
request-method: get
Response
engine: matcho
matcho:
uri: /Encounter
params:
patient: .user.data.patient_id
resourceType: AccessPolicy
id: search-patient-encounter
meta:
lastUpdated: '2020-11-05T15:28:58.054136Z'
createdAt: '2020-11-05T15:28:58.054136Z'
versionId: '0'

And this policy works a bit trickier. The allowed URI is /Encounter and it doesn't contain any additional parts that could be identified as request parameters as in the previous case. So, in order to provide the required request parameter patient to the Access Policy matching engine, we have to specify it as the query parameter of our request. And after the Access Policy engine allows such a request, the Search Engine comes into play. It filters out encounters that do not match the condition of patient = our-patient-id. To know more about how the AidBox Search works, see the Search section. To know more about the available search parameters, refer to the Search Parameters section of the FHIR documentation for the resource of interest.

Finally, we can make a request for the list of patient encounters.

Request
Response
Request
GET /Encounter?patient=new-patient
Response
{
"query-time": 7,
"meta": {
"versionId": "155"
},
"type": "searchset",
"resourceType": "Bundle",
"total": 1,
"link": [
{
"relation": "first",
"url": "/Encounter?patient=new-patient&page=1"
},
{
"relation": "self",
"url": "/Encounter?patient=new-patient&page=1"
}
],
"query-timeout": 60000,
"entry": [
{
"resource": {
"class": {
"code": "AMB"
},
"status": "planned",
"subject": {
"id": "new-patient",
"resourceType": "Patient"
},
"participant": [
{
"individual": {
"id": "practitioner-1",
"resourceType": "Practitioner"
}
}
],
"id": "enc1",
"resourceType": "Encounter",
"meta": {
"lastUpdated": "2020-11-10T11:11:39.464261Z",
"createdAt": "2020-11-06T19:14:46.247628Z",
"versionId": "150"
}
},
"fullUrl": "/Encounter/enc1",
"link": [
{
"relation": "self",
"url": "/Encounter/enc1"
}
]
}
],
"query-sql": [
"SELECT \"encounter\".* FROM \"encounter\" WHERE \"encounter\".resource @> ? LIMIT ? OFFSET ? ",
"{\"subject\":{\"id\":\"new-patient\",\"resourceType\":\"Patient\"}}",
100,
0
]
}

Observation access

Read access

Granting access to observations is similar to the previous case. We just add another policy, that looks just like the previous one, but matches against another URI. It is so similar, that we should stop there and think a little what happens if we want to grant read access to more resources β€” we end up with a bunch of almost indistinguishable policies. A better approach in this case is to use the CompartmentDefinition resource.

Request
Request
POST /fhir/CompartmentDefinition
​
id: patient
url: http://hl7.org/fhir/CompartmentDefinition/patient
code: Patient
search: true
status: draft
resource:
- code: Encounter
param:
- patient
- code: Observation
param:
- subject
- performer

Now, when we've created CompartmentDefinition resource, we can access patient related resources with such requests: GET /Patient/{patient-id}/{resource}. To know in detail about how compartments work see the Compartments tutorial.

And that's it! We don't even need to add more policies, since we already have the policy that allows user to access URIs that match /Patient/.* regex.

Request
Response
Request
GET /Patient/new-patient/Observation
Response
{
"query-time": 7,
"meta": {
"versionId": "171"
},
"type": "searchset",
"resourceType": "Bundle",
"total": 2,
"link": [
{
"relation": "first",
"url": "/Observation?_filter=subject eq 'new-patient' or performer eq 'new-patient'&page=1"
},
{
"relation": "self",
"url": "/Observation?_filter=subject eq 'new-patient' or performer eq 'new-patient'&page=1"
}
],
"query-timeout": 60000,
"entry": [
{
"resource": {
"class": {
"coding": [
{
"code": "11557-6"
}
]
},
"status": "registered",
"subject": {
"id": "new-patient",
"resourceType": "Patient"
},
"performer": [
{
"id": "practitioner-1",
"resourceType": "Practitioner"
}
],
"resourceType": "Observation",
"id": "observation-1",
"meta": {
"lastUpdated": "2020-11-06T19:14:46.078643Z",
"createdAt": "2020-11-06T19:14:46.078643Z",
"versionId": "0"
}
},
"fullUrl": "/Observation/observation-1",
"link": [
{
"relation": "self",
"url": "/Observation/observation-1"
}
]
},
{
"resource": {
"class": {
"coding": [
{
"code": "11557-6"
}
]
},
"status": "registered",
"subject": {
"id": "new-patient",
"resourceType": "Patient"
},
"performer": [
{
"id": "new-patient",
"resourceType": "Patient"
}
],
"resourceType": "Observation",
"id": "observation-3",
"meta": {
"lastUpdated": "2020-11-06T19:14:46.078643Z",
"createdAt": "2020-11-06T19:14:46.078643Z",
"versionId": "0"
}
},
"fullUrl": "/Observation/observation-3",
"link": [
{
"relation": "self",
"url": "/Observation/observation-3"
}
]
}
],
"query-sql": [
"SELECT \"observation\".* FROM \"observation\" WHERE (\"observation\".resource @> ? OR \"observation\".resource @> ?) LIMIT ? OFFSET ? ",
"{\"subject\":{\"id\":\"new-patient\"}}",
"{\"performer\":[{\"id\":\"new-patient\"}]}",
100,
0
]
}

If we want to grant access to some other resource we just need to add it to the CompartmentDefinition resource that we've created. See FHIR documentation to know what resources can be added to a patient compartment. And we can get rid of the Access Policy that was previously created for encounters.

Write access

User should be able to create their own observation, e.g. to report blood sugar level. The following policy manages this case:

Request
Request
POST /AccessPolicy
​
id: create-patient-observation
engine: matcho
matcho:
uri: '/Observation'
body:
subject:
id: .user.data.patient_id
resourceType: Patient
performer:
$contains:
id: .user.data.patient_id
resourceType: Patient
request-method: post

With this policy we can only create observations where subject and performer must be the user's patient.

Request
Request
POST /Observation
​
{
"id": "observation-3",
"code": {
"coding": [
{
"code": "11557-6"
}
]
},
"status": "registered",
"subject": {
"id": "new-patient",
"resourceType": "Patient"
},
"performer": [
{
"id": "new-patient",
"resourceType": "Patient"
}
]
}

Now it's time to make an important note. In general It is not possible to use some kind of CompartmentDefinition approach to grant write access to many resources at once, as we did it previously for read access. That's because resources may require sophisticated logic to define which part of a resource could have write access and which not. Such logic may even lie beyond the abilities of the Access Control mechanism and in this case custom API is the only resort. But in quite simple scenario like the creation of observation Access Policies are helpful.

Let's create a new policy that allows our user to update their observations through the PATCH method. Matcho engine is no longer enough to make a rule for this kind of request since it only relies on the request and the user parameters. Now we need to peek into the requested resource to understand if it is related to our user and could be patched.

TODO: describe the necessity and benefits of the json-schema engine.

Request
Request
POST /AccessPolicy
​
id: patch-observation
link:
- id: Patch
resourceType: Operation
engine: complex
and:
- engine: sql
sql:
query: >
select true from observation
where resource#>>'{subject,id}' = {{user.data.patient_id}}
and id = {{params.resource/id}}
and resource->'performer' @> jsonb_build_array(jsonb_build_object('resourceType', 'Patient', 'id', {{user.data.patient_id}}::text))
- engine: json-schema
schema:
properties:
body:
properties:
subject:
optional: true
properties:
id:
constant:
$data: '#/user/data/patient_id’

Now we can try to update our patient and the patient related to the User-2 and observe the difference in the responses.

Access to the next of kin records

Access policies depend a lot on how we model our resources. FHIR doesn't provide convenient facilities to make relations between patients. The easiest way to add such relations is to enhance a User resource with the list of related patients. Let's define that Patient-2 is related to User-1.

Request
Request
PATCH /User/patient-user
​
data:
related_patients:
- new-patient1

To grant User-1 access to related patients we should simply update patient-access policy.

Request
Request
PUT /AccessPolicy/patient-access
​
engine: matcho
matcho:
uri: '#/Patient/.*'
user:
data:
$one-of:
- related_patients:
$contains: .params.resource/id
- patient_id: .params.resource/id
request-method: get