Unlike recent past, it is more important to store information safely ,not distributing information as much as possible (As I tried to project in the cover photo). In this case data security is one of the most important problems today. .

Firestore is a document orianted NoSQL database that very useful and scalable. And it has a fairly easy security infrastructure.

You can use Firebase auth services in Firestore security rules infrastructure. So it’s easy to create user-based security rules.

Unfortunately, I didn’t get enough documentation on this subject, so I felt the need to write this article.

After this information, which is already known to everyone, I will give a quick example.

Table of Contents

1. Understanding Firestore Security Rules

How it works?

2. Syntax

How write rules?

3. Document Based Rules

How do protect documents?

4. Document Rules with Firebase Auth

How protect document according to different users?

5. Field Based Rules

How protect document according to different users?

6. Optimization

How to protect your wallet ?

7. Complex Field Based Rules

How to protect document field when document is public?

1) Understanding Firestore Security Rules

Cloud Firestore Security Rules work explained on the picture. There are 4 king of operation and each rules have 2 condition.

Each rules have ;

A ) match /path conditon. You can write rules for each document or collection.

B) Operations list to be allowed.There are 4+1 kind of operations ; Read , Delete , Update , Create (or “ write ” valid for delet , update , create ). You can write if condition each opearetion seperate.

C) If condition . where the first condition is satisfied, the requested operation shall be permitted.

2) Syntax

If you use document name include “ {} ” you can use parameter that column. Also this match condition it applies to all documents at that level. (for example “match all users” in picture second match).

Operators

&& and

|| or

== is equal

!= is not equal



request request side informations

resource database side informations



request.auth request side auth informations

request.resource request side parameters

request.resource.data change request data

resource.data resource(in firestore) data

You can get data with .fieldName both side data.

3) Document Basis Rules

match /{document=**} {

allow read, write: if false;

}

All files are closed to all operations unless there are exceptions. It is recommended that you add this column at the beginning of the rules and write a rule for each permission.

match /infos/about {

allow read : if true;

}

Everyone read about document but not delete, create or update.

match /books/{bookId} {

allow read , create: if true;

}

Everyone read , and create , but anyone doesnt update , delete any document in a books collections.

4) Document Rules with Firebase Auth

match /users/{userId} {

allow read ,delete , update : if request.auth.uid == userId;

allow create : if true;

}

Everyone create document in a users collection but only users whose userId is equal to the documentID can do other operations

match /users/{userId}/publishedPosts/{postId} {

allow read : true;

allow create : if request.auth.uid == userId;

allow delete : if false;

}

Everyone read this user’s all published posts. But only this user create own post and anyone does not delete post.

In this case, no one is allowed to update .

5) Field Based Rules

match /posts/{postID}{

allow read : true;

allow write: if request.resource.data.ownerId == request.auth.uid;

}

Everyone can read post but only this user can update , delete and create . This example only “ user132 ” can write operations.

Other example :

match /users/{userId} {

allow read ,delete , update : if request.auth.uid == userId;

allow create : if request.resource.data.age > 18;

}

We have added another condition to the example in the fourth article : Everyone can create document if field of “age” is geater than 18 .

6) Optimization

We need to optimize our database architecture according to rules. Firestore’s recommendations include information that we need to store confidential information in sub-collections and process it with cloud functions. This is a good solution. But not cheap everytime.

We may store the information of the owner of an anonymous post in sub-collections.This information is written once and is often unreadable. (Because it is anonymous.)

But for example we have a promotion. A document for each promotional code. Suppose the promotion has a number of uses and a quota. Certainly, malicious people will want to change these numbers. So we have a document that everyone can read but not everyone can change. According to Firestore’s suggestion, write your promotional uses elsewhere and process with functions. This is mean cost for +2 read +2 write operatins. But it will often be costly to do this for every small data.

For these reasons, I will pass the rules on a field basis.

My Solution;

7) Complex Field Based Rules

This is my promotion document.

match /promotions/{id} {

allow read : if true;

allow update : if resource.data.useCount < request.resource.data.useCount

&& resource.data.max == request.resource.data.max;

}

match /users/{userId}/promotions/{proId} {

allow read : if request.auth.uid == userId;

allow create : if request.auth.uid == userId;

allow delete : if false;

}

In this case. Everyone can read promotion document in a promotions collections. Anyone cant delete and create .

Also IF useCount field value in incoming data is greater than in value of original data (only increment) and max is equal to original data (not permission update max field)people can update document.

Please read green highlighted.

Permission denied. Because max is different than original data.

Other Example:

match /posts/{postID} {

allow read: if true;

allow create: if true;

allow update: if request.resource.data.vote is number

|| request.resource.data.randomNumber is number

&& request.resource.data.anonymous == resource.data.anonymous

&& request.resource.data.content== resource.data.content

&& request.resource.data.userName == resource.data.userName

&& request.resource.data.owner == resource.data.owner && request.auth.uid != null;

}

vote and randomNumber fields are updatable.

anonymous , content , userName , owner fields are not updatable.

Hopefully this article will solve your problems. Good work!