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I have a Cerbos setup now that I quite like :ok_ha...
# help
m
I have a Cerbos setup now that I quite like đź‘Ś My next step is to get the Query Criteria to work. I couldn't find an explanation on how it works in the documentation. Could you point me to the correct documentation, an article or a YouTube video that shows how it works? I'm using Node/React/Next. But I don't use Prisma. Technically, what I need it just an policy yaml example, and how to call it from the Cerbos JavaScript SDK.
d
The Query Plan API is used in a relatively advanced use case. The API returns an abstract syntax tree (AST) of the relevant policy. Cerbos partially evaluates the policy because the principal is known, but the resource(s) are not, then returns the AST in the result. The AST looks like this:
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{
  "expression": {
    "operator": "eq",
    "operands": [
      {
        "variable": "request.resource.attr.status"
      },
      {
        "value": "PENDING_APPROVAL"
      }
    ]
  }
}
It’s straightforward to translate this particular AST to SQL. Unless you’re using an ORM for which we have an adapter, you must write a translation layer yourself.
m
This is what I wrote:
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const planResources = await cerbos.planResources({ principal: user, action: "view", resource: { kind: "settings" } })
console.log("planResources:", planResources);
This is my output:
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planResources: {
  cerbosCallId: '01JSBF155R27JZ7H3N7KZJ7XBE',
  requestId: 'bce23d54-84ac-496e-b085-e03872e2f43d',
  validationErrors: [],
  metadata: undefined,
  kind: 'KIND_ALWAYS_ALLOWED'
}
And this is my policy:
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apiVersion: api.cerbos.dev/v1
resourcePolicy:
  resource: settings
  version: default
  rules:
    - actions:
        - view
      roles:
        - admin
      effect: EFFECT_ALLOW
How do I get the AST, and how do I update the policy so it works with the AST?
d
KIND_ALWAYS_ALLOWED
means that this principal can view all resources, so no authorization filter is required.
m
That makes sense! Then how do I update the policy so it works with this?
A more real life example could be:
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apiVersion: api.cerbos.dev/v1
resourcePolicy:
  resource: report
  version: default
  rules:
    - actions:
        - create
      roles:
        - admin
      effect: EFFECT_ALLOW

    - actions:
        - delete
      roles:
        - admin
      effect: EFFECT_ALLOW

    - actions:
        - update
      roles:
        - admin
      effect: EFFECT_ALLOW

    - actions:
        - view
      roles:
        - admin
        - partner
      effect: EFFECT_ALLOW
The partner may only see reports that are draft and active, but not inactive.
d
I’ve created a playground project.
The relevant part of the policy:
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- actions:
        - view
      roles:
        - admin
      effect: EFFECT_ALLOW

    - actions:
        - view
      roles:
        - partner
      effect: EFFECT_ALLOW
      condition:
        match:
          expr: request.resource.attr.status in ["DRAFT", "ACTIVE"]
The query plan for the partner:
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{
  "requestId": "query-plan",
  "action": "view",
  "resourceKind": "report",
  "filter": {
    "kind": "KIND_CONDITIONAL",
    "condition": {
      "expression": {
        "operator": "in",
        "operands": [
          {
            "variable": "request.resource.attr.status"
          },
          {
            "value": [
              "DRAFT",
              "ACTIVE"
            ]
          }
        ]
      }
    }
  }
}
m
Now we are getting closer 🤩 This is what I got now.
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planResources: {
  cerbosCallId: '01JSBGF546XKTK419CW20CMQGW',
  requestId: '89e753f8-0212-4888-9dfb-a28c46872aca',
  validationErrors: [],
  metadata: undefined,
  kind: 'KIND_CONDITIONAL',
  condition: PlanExpression {
    operator: 'in',
    operands: [ [PlanExpressionVariable], [PlanExpressionValue] ]
  }
}
I am not sure I'm using the SDK correctly:
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const planResources: PlanResourcesResponse = await cerbos.planResources({ principal: user, action: "view", resource: { kind: "settings" } })

console.log("planResources:", planResources);
d
Try converting planResources to a string (JSON.stringify()) before logging.
kind: “settings”
I assume you renamed 
report
to 
settings
in the policy file.
m
I just copied the some of your code in to mine.
It works now 🤩🙏🥳
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{
  "cerbosCallId": "01JSBGY422BSRMN04MHC483499",
  "requestId": "bfd8b6f0-ab5b-41c2-a05b-36fc55f57663",
  "validationErrors": [],
  "kind": "KIND_CONDITIONAL",
  "condition": {
    "operator": "in",
    "operands": [
      {
        "name": "request.resource.attr.status"
      },
      {
        "value": [
          "DRAFT",
          "ACTIVE"
        ]
      }
    ]
  }
}
🎉 1
d
Please feel free to book a call with an engineer if you believe it might speed things up for you. We are happy to help.
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