Loopback $owner doesn't works for findById

I would like to get some informations about my user with loopback. For that I created a "user" model related with "accessToken" model until now a POST on /user, a POST on /user/login and a POST on /user/logout is working.

I added on /common/models/user.json

{
  "name": "user",
  "base": "User",
  "idInjection": true,
  "options": {
    "validateUpsert": true
  },
  "properties": {},
  "validations": [],
  "relations": {
    "accessTokens": {
      "type": "hasMany",
      "model": "accessToken",
      "foreignKey": "userId"
    }
  },
  "acls": [
    {
      "accessType": "EXECUTE",
      "principalType": "ROLE",
      "principalId": "$authenticated",
      "permission": "ALLOW",
      "property": "logout"
    },
    {
      "accessType": "EXECUTE",
      "principalType": "ROLE",
      "principalId": "$owner",
      "permission": "ALLOW",
      "property": "findById"
    }
  ],
  "methods": {}
}

And when I do a GET on /user/{id} I got :

{
  "error": {
    "statusCode": 401,
    "name": "Error",
    "message": "Autorisation requise",
    "code": "AUTHORIZATION_REQUIRED",
    "stack": "Error: Autorisation requise\n    at..."
  }
}

I guess I didn't understand acl/relation very well

from Loopback $owner doesn't works for findById