CODEWITHSUNDEEP
fluttergoogle-cloud-firestorefirebase-security
HaKim
HaKim

Reputation: 287

firestore read permission denied, but it works in simulator with set IDs

I am trying to filter out posts that were hidden by the user. streaming is simple:

 StreamBuilderWrapper(
      shrinkWrap: true,
      stream: postRef
          .orderBy('stars', descending: true)
          .orderBy('timestamp', descending: true)
          .snapshots(),
      physics: NeverScrollableScrollPhysics(),
      itemBuilder: (_, DocumentSnapshot snapshot) {
        Review reviews= Review.fromJson(snapshot.data());
        return posts.postId != null
            ? Padding(
          padding: const EdgeInsets.only(bottom: 12.0),
          child: Reviews(review: reviews),
        )
            : Container(
          child: Center(
            child: Text('balhblahblahb'),
          ),
        );
      },
    ),

trying to use firestore rules to set the read permission, where hidingUserId is an array of users, and isHiddenBy a currentUser id:

match /reviews/{review}{
  allow read: if request.auth != null && !(request.auth.uid in 
                 request.resource.data.hidingUserId) 
              || request.resource.data.isHiddenBy == null || 
                 request.resource.data.isHiddenBy != request.auth.uid
  allow delete, update, create: if request.auth != null
}

playing with rules in simulator with IDs works fine. they deny the read when the userId in one of the conditions, and allow read if userId is not in. However, when I test the app on the android device, I get the:

[Firestore]: Listen for Query(target=Query(reviews order by stars, - 
timestamp, -__name__);limitType=LIMIT_TO_FIRST) failed: 
Status{code=PERMISSION_DENIED, description=Missing or insufficient 
permissions., cause=null}

why is the denial of permission? how to structure the rules, so it filters out the posts if the user has hidden it? thanks!

Upvotes: 1

Views: 199

Answers (1)

Frank van Puffelen
Frank van Puffelen

Reputation: 598708

Firebase's security rules are not filters; they don't inspect each individual document to see if it matches the rules. Instead they check the query/read operation you run against the rules to ensure it only requests documents that match those rules.

So you will have to replicate the condition from your rules in the query, an approach known as securely querying data. If you replicate the filter on hidingUserId in your query, the query meets that clause of the rules and that part of the rule will pass.

Unfortunately it is not possible to do an OR condition across multiple fields in Firestore, so it is not possible to replicate the entire rule in a query. If you can translate the conditions into a set of AND conditions, it should be possible to translate it into a query though - so that would be the direction I'd look.

Upvotes: 1

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