Firebase data structure and security rules - firebase

Question

Im having trouble with the security rules for firebase and Im not 100% where I am going wrong. I am thinking that maybe I have my data structure wrong:
{
"users": {
"uid": {
"displayName": "Name";
}
},
"modules": {
"id": {
"title": "buttons",
"uid": "(user id string)"
},
"id": {
"title": "navbars",
"uid": "(user id string)"
}
},
"snippets": {
"id = moduleID": {
"id (of snippet)": "(id string)" {
"uid (user ID)": "(string)",
"body": {
"css": "(some code)",
"html": "(Some code)",
"name": "(string)",
"description": "(string)"
}
}
}
}
Everything in the app works fine, but when I started to add security rules I got access denied errors. Im just wondering if I have the data structure correct in the first place or is the security rules completely wrong?
Security rules:
{
"rules": {
"users": {
"$uid": {
// grants write and read access to the owner of this user account whose uid must exactly match the key ($uid)
".write": "auth != null && auth.uid == $uid",
".read": "auth != null && auth.uid == $uid"
}
},
"snippets": {
"$uid": {
// grants write and read access to the owner of this user account whose uid must exactly match the key ($uid)
".write": "auth != null && auth.uid == $uid",
".read": "auth != null && auth.uid == $uid"
}
},
"modules": {
"$uid": {
// grants write and read access to the owner of this user account whose uid must exactly match the key ($uid)
".write": "auth != null && auth.uid == $uid",
".read": "auth != null && auth.uid == $uid"
}
}
}
Any advice would be greatly appreciated.

Answer 1

It seems the rules are malformed based on the data structure.
The rules have $uid's in each node but your data doesn't match that. Users has uid but modules has id and snippets has id = moduleID.
$uid is a variable that holds the node name so it can be referenced inside { } so you should (for readability) rename that variable in the other two nodes to something that makes more sense inside each {}. Like in modules, have it $module_id.
However. I think the jest of this is you want to limit reading snippets and modules to authenticated users. To do that, you can reference the users node.
a .read rule would be something like this
"modules": {
"$module_id": {
".read": "auth != null && root.child('users/' + auth.id).exists()
}
So your modules node can be read by a user that is auth'd and their uid also appears in the users/ node

Answer 2

Are you using the Firebase Bolt compiler for rules? I had to write some complex rules and doing it by hand gets confusing very quickly.
Below is what it would looks like. Very easy to make changes, compile and try them out.
//current logged in user
isUser(uid) = auth != null && auth.uid == uid;
//does this module id exist
hasValidModule(module_id) = root['modules'][module_id] != null;
//dont let anyone read or write to top node
path / {
read() = false;
write() = false;
}
path /users/$user_id
{
write() = isUser($user_id);
read() = isUser($user_id);
}
path /snippets/$module_id/$snipit_id/$user_id
{
write() = isUser($user_id) && hasValidModule($module_id);
read() = isUser($user_id);
}
path /modules/$user_id
{
write() = isUser($user_id);
read() = isUser($user_id);
}
Here's the json it spits out:
{
"rules": {
"users": {
"$user_id": {
".read": "auth != null && auth.uid == $user_id",
".write": "auth != null && auth.uid == $user_id"
}
},
"snippets": {
"$module_id": {
"$snipit_id": {
"$user_id": {
".read": "auth != null && auth.uid == $user_id",
".write": "auth != null && auth.uid == $user_id && newData.parent().parent().parent().parent().child('modules').child($module_id).val() != null"
}
}
}
},
"modules": {
"$user_id": {
".read": "auth != null && auth.uid == $user_id",
".write": "auth != null && auth.uid == $user_id"
}
}
}
}
There's some info on the Firebase blog but the doc that really helped me is this
https://github.com/firebase/bolt/blob/master/docs/language.md