firebase security permission not working

Question

I have below data stored in my firebase:

firebaseRoot
    admins
        simplelogin:1: 
    users
        simplelogin:1
            email: [email protected]
            picture: csd
            provider: password
            uid: simplelogin:1
        simplelogin:2
            email: [email protected]
            picture: zsd
            provider: password
            uid: simplelogin:1

and following security rules:

{
  "rules": {
    "admins": {
      ".read": "root.child('admins').child(auth.uid).val() === true",
      ".write": "root.child('admins').child(auth.uid).val() === true"
    },
    "users": {
      "$user":{
        ".read": "$user === auth.id || root.child('admins').child(auth.uid).val() === true",
        ".write": "$user === auth.id"
      }
    }
  }
}

My authorization requirements are as below.

1. admins can be read and added only by the existing admin only. This works.
2. All users can be read by the admin but should not be able to write user data.
3. a user can read and update his own user data.

Currently with above rules, I am not able read users data both for admins and logged in users. I get below error message. Please provide your help. Thanks.

var rootRef = new Firebase('https://xxxxx.firebaseio.com/');
var users = rootRef.child('users');
users.on('value', function(snap) {
console.log(snap.key(), snap.val());
}, function(error) {
console.log(error);
});

Error:

Error: permission_denied: Client doesn't have permission to access the desired data.

Answer 1

There are two pitfalls when it comes to Firebase security rules:

1. rules cascade

   This means that once you give somebody (read or write) access on a certain level in the JSON structure, you cannot take that right away anymore on a lower level

2. rules are not filters

   This means that you can only read a node if you have read access to all data in that node. If you only have read access to part of the data, a read operation for the complete data will fail.

In your security rules, you only give permission to read (some of) the children under users. So trying to read the entire users.on('value' will fail.

You can solve this by giving the administrator .read access to the users node.

    "users": {
      ".read": "root.child('admins').child(auth.uid).val() === true",
      "$user":{
        ".read": "$user === auth.id",
        ".write": "$user === auth.id"
      }
    }

Answer 2

Here is my working example:

ajsecuretest
    roles
        simplelogin:1
            role: 'admin'
        simplelogin:2
            role: 'editor'
    users
        simplelogin:1
             email: '[email protected]'
             picture: 'a.jpg'
             provider: 'password'
             uid: 'simplelogin:1'
        simplelogin:2
             email: '[email protected]'
             picture: 'b.jpg'
             provider: 'password'
             uid: 'simplelogin:2'

Rules:

{
  "rules": {
    "roles":{
      ".read": "root.child('roles').child(auth.uid).child('role').val() === 'admin'",
      ".write": "root.child('roles').child(auth.uid).child('role').val() === 'admin'",
      "$id" : {
        ".read" : "$id === auth.uid"
      }
    },
    "users": {
      ".read" :  "root.child('roles').child(auth.uid).child('role').val() === 'admin'",
      "$user":{        
        ".read": "$user === auth.uid",
        ".write": "$user === auth.uid"
      }
    }
  }
}