Firebase Realtime Database Rules Permission Denied

I have an app where I am using a custom authentication method. First, on the user login into the app, I generate the JWT Token on the server and send it back to the app.

function generateJWT($con,$userID,$cretedTime) {
	$secret_Key  = "-----BEGIN PRIVATE KEY-----\HCPW\nAtY9K1/19yScEhdmhw8Ozek=\n-----END PRIVATE KEY-----\n";
	$date   = time();
	//$expire_at     = $date->modify('+3 minutes')->getTimestamp(); // Add 60 seconds
	$domainName = "firebase-adminsdk-XXXXXXXX.iam.gserviceaccount.com";

	$request_data = [
	'iss'  => $domainName, 
	'sub' => $domainName,
	'aud' => "https://identitytoolkit.googleapis.com/google.identity.identitytoolkit.v1.IdentityToolkit",
	'iat'  => $date,         // Issued at: time when the token was generated
		                      // Issuer
	//'exp' => $date+(60*60),  // Maximum expiration time six month in seconds //15778476 
	'uid' => $userID,                     // User name
	'created' => $cretedTime,                     // User name
	];
     $newToken = JWT::encode($request_data,$secret_Key,'RS256');	 	
	 return $newToken; 
	
}

Then In the app send on receiving this token I am start the login process.my app using custom firebase auth

firebaseAuth = FirebaseAuth.getInstance();
firebaseAuth.signInWithCustomToken(Session.getJWT())
        .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
            @Override
            public void onComplete(@NonNull Task<AuthResult> task) {
                if (task.isComplete()){
                    if(getActivity()!=null){
                     //User Logged In Successfully 
                    }else{
                        // Failed
                    }

                }
            }
        });

So after days of googling, I got the Firebase rules for the structure of my database to look like this

{
  "Chat": {
    "206-4": "",
    "311-158": "",
    "215-112": "",
    "734-115": "",
    "734-55": "",
    "734-468": "",
    "34-32": "",
    "534-179": "",
    "734-345": {
      "-NI7hqW3YTFKpnSZU422": {
        "Message": "Test",
        "Message_From": "Support ",
        "Message_From_ID": "4",   
        "Message_To": "Demo",
        
      },
      "-NMVOwlAqmyIA52QU9F-": {
        "Message": "Hi",
        "Message_From": "Support ",
        "Message_From_ID": "4",
        "Message_To": "Demo",
        
      }
    },    
    "347-234": {
      "-NI7hXybU02Mg6vYqdKp": {
        "Message": "Ohio",
        "Message_From": "Elaxer  Support ",
        "Message_From_ID": "4",
        "Message_To": "Demo 2",
        
      }
    },
    "281-69": "",
    "317-34": ""
  },
  "Users": {
    "4": {
      "Online": false,
      "lastSeen": "1675785660782"
    },    
    "284": {
      "Online": false,
      "lastSeen": "1673611185873"
    }
  },
  "UsersLocations": {
    "4-210": {
      "-1": {
        "Latitude": "22.605",
        "Longitude": "88.375"
      }
    },
	"25-21": {
      "-1": {
        "Latitude": "22.605",
        "Longitude": "88.375"
      }
    }
  }
}

Firebase Rules

{
  "rules": {
    "Chat": {
      "$room_id": {
        ".read": "auth.uid === $room_id && $room_id.beginsWith(auth.uid + '-') || auth.uid === $room_id && $room_id.endsWith('-' + auth.uid)",
        ".write": "auth.uid === $room_id && $room_id.beginsWith(auth.uid + '-') || auth.uid === $room_id && $room_id.endsWith('-' + auth.uid)"
      }
    },
    "Users": {
      "$uid": {
        ".write": "$uid === auth.uid"
      }
    },
    "UsersLocations": {
      "$user_location_id": {
        ".read": "auth.uid === $user_location_id && $user_location_id.endsWith('-location')",
        ".write": "auth.uid === $user_location_id && $user_location_id.endsWith('-location')"
      }
    }
  }
}

So when ever i tried to create or get the Chat node (Chatroom).

DatabaseReference db = FirebaseDatabase.getInstance().getReference().child("Chat");
db.addListenerForSingleValueEvent(new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        
    }

    @Override
    public void onCancelled(DatabaseError databaseError) {           
    }
});

It gives me error

> Listen at /Chat failed: DatabaseError: Permission denied

I am not able to understand why i am getting this error when i am only checking the user id exist in room name and my jwt token on generation time having user id of one user. Please help me out, what's wrong i am doing with my rules

As Alex also answered: you're not granting anyone read access to /Chat, so any code trying to read from there will be rejected. I would not recommend his answer though, as the rule on /Chat makes the more strict rules on /Chat/$room_id meaningless.

I recommend reading the documentation on rules don't filter data (which explains why your current code don't work and on the fact that permissions cascade (which explains why the rules in Alex' answer make the ones you already have meaningless).

The data structure you have look like what I described in my answer to: https://stackoverflow.com/questions/33540479/best-way-to-manage-chat-channels-in-firebase. In my answer there I also showed how to model security rules to allow read access and how to get a list of the chat room for the user, so I recommend checking that out.

As I tried explaining in the comments, the way you handle the sign-in result is wrong:

// ❌ THIS IS WRONG ❌ 
firebaseAuth = FirebaseAuth.getInstance();
firebaseAuth.signInWithCustomToken(Session.getJWT())
    .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> task) {
            if (task.isComplete()){
                if(getActivity()!=null){
                 //User Logged In Successfully 
                }else{
                    // Failed
                }
            }
        }
    });

Instead, when a Task completes you should check whether it succeeded or failed, as shown in the documentation on handling tas results. In your case that'd be:

// ✅ Handling success and failure correctly 👍
firebaseAuth = FirebaseAuth.getInstance();
firebaseAuth.signInWithCustomToken(Session.getJWT())
    .addOnCompleteListener(new OnCompleteListener<AuthResult>() {
        @Override
        public void onComplete(@NonNull Task<AuthResult> task) {
            if (task.isSuccessful()!=null) {
                // User signed in
                // TODO: access database
            } else {
                // Sign in failed
                throw task.getException();
            }
        }
    });