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Access Control: topaz

Gautier DI FOLCO January 10, 2024 [dev] #access control #security #draft concepts

In the last log, we have studied Open Policy Agent which introduced Policy-as-code, sadly, we cannot easily represent ReBAC with it.

That's where topaz kicks-in.

Note: at the time of writing, topaz is a bit older than one-years-old, has less than 300 commits done by less than 20 people, I won't recommend to use it in production (I don't recommend not running it in production, but if I have the decision to take, it won't be my go-to choice).

Let's draft a simple file access policy:

allowed {
  ds.check_permission({
    "object": {
      "key": input.resource.file,
      "type": "file"
    },
    "permission": {"name": "read"},
    "subject": {
      "key": input.user.key,
      "type": "user"
    }
  })
}

Note: topaz use OPA's policy language

We can define our objects:

{
 "objects": [
   {
     "type": "user",
     "id": "alice",
     "properties": {
       "verified": true
     }
   },
   {
     "type": "user",
     "id": "bob",
     "properties": {
       "verified": true
     }
   },
   {
     "type": "file",
     "id": "/etc/alice/diary.txt",
     "properties": {
       "sensitive": true
     }
   }
 ]
}

Then the relations:

{
 "relations": [
   {
     "object_type": "user",
     "object_id": "alice",
     "relation": "owns",
     "subject_type": "file",
     "subject_id": "/etc/alice/diary.txt"
   }
 ]
}

Finally we can query them with the inputs:

{
 "subject": {
   "type": "user",
   "key": "bob"
 },
 "relation": {
   "name": "owns",
   "objectType": "file"
 },
 "object": {
   "type": "file",
   "key": "/etc/alice/diary.txt"
 }
}