Firebase Storage Custom metadata security rule for uids list

Question

I am developing an iOS messaging application where a user can send the same message to several people. The message is stored in the firebase repository. I only want to include the users who sent the message in order to read it from the repository. I already implement this rule structure in my firebase database.

To implement this for storage, I add a list of uids to the customMetadata file of the message file, including the fromUid key for the person who composed the message. In my iOS app, I do the following:

var metadataValues = [String:String]() for friendUid in friendsSelected.keys { metadataValues.updateValue(friendUid, forKey: friendUid) // how do I access these values in my security rules } metadataValues.updateValue(senderUid, forKey: "fromUid") // how do I access this in security rules let messageMetadata = FIRStorageMetadata() messageMetadata.customMetadata = metadataValues 

It was my attempt for the rules for reading and writing rules for node messages in Firebase Storage, but this does not work, and the documentation does not help.

  match /messages/{messageId} { allow read: if request.auth.uid == resource.metadata.request.auth.uid; // I want all friend uids to be able to read file allow write: if request.auth.uid == resource.metadata.fromUid; // only the person who create the message can access it } 

My attempt does not work. How to access customMetadata variable using fromUid keys and uids friends "request.auth.uid" in my security rules?

As a side element, I assume that there is no limit to the number of keys that I add to customMetadata?

Answer 1

So I managed to solve it. The problem was that I was not familiar with Javascript, and therefore I misunderstood the syntax. After learning Javascript, I was soon able to process it.

Hope my answer helps someone else, but will recommend learning the basics of Javascript if you are in a similar position for me.

It is also worth noting that to access the metadata of the files that you use request.resource.metadata before writing, and resource.metadata to access after loading.

  match /messages/{messageId} { allow write: if request.resource.metadata['fromUid'] == request.auth.uid; allow read: if resource.metadata[request.auth.uid] == request.auth.uid; }