如何通过Firebase规则按应用版本拦截低版本用户

Hey there! Let's break down how to fix your excessive data usage issue by targeting those old app versions. First off—yes, you can use Firebase Security Rules to restrict access to only app versions 15 and above, but you'll need to pass the app version number with every Firebase request. Let's walk through the details, plus backup methods if you hit snags.

1. Implementing Version Checks in Firebase Rules #

To make this work, your app needs to send its version number to Firebase, and the rules will validate it. Here are two reliable ways to do this:

Option A: Pass Version as a Query Parameter (Great for Anonymous Users) #

If your app lets users chat without logging in, add the app version as a query parameter whenever you fetch or write chat data:

// Android/Kotlin example: Attach version to your database query
val db = FirebaseDatabase.getInstance()
val chatRef = db.getReference("chats")
    .orderByKey()
    .limitToLast(100)
    .queryEqualToValue(BuildConfig.VERSION_CODE, "appVersion")

Then update your Firebase Security Rules to check this parameter:

{
  "rules": {
    "chats": {
      ".read": "queryParam.appVersion > 14",
      ".write": "queryParam.appVersion > 14"
    }
  }
}

Option B: Use Firebase Auth Custom Claims (Best for Authenticated/Anonymous Users) #

If you use Firebase Auth (even anonymous auth), set a custom claim on the user's session to store their app version. This is more secure because parameters can be tampered with, but claims are verified server-side:

// Set custom claim after anonymous login
Firebase.auth.currentUser?.let { user ->
    val claims = hashMapOf("appVersion" to BuildConfig.VERSION_CODE)
    Firebase.auth.setCustomUserClaims(user.uid, claims)
}

Then adjust your rules to check the auth token's claim:

{
  "rules": {
    "chats": {
      ".read": "auth.token.appVersion > 14",
      ".write": "auth.token.appVersion > 14"
    }
  }
}

Note: If your chat data lives at the root instead of a chats node, apply the rules directly to the root .read/.write fields.

2. Backup Solutions If Rules Aren't Enough #

If old versions of your app can't be modified to send the version number (or if third-party APKs bypass the parameter), try these alternatives:

• Force App Updates: Add a version check on app startup. Use Firebase Remote Config to host the minimum allowed version (15). If the user's version is older, block access to the chat and show a mandatory upgrade prompt.
• Migrate to a New Database Node: Move all new chat traffic to a new node (e.g., chats_v2) in Firebase. Keep the old node active temporarily, then gradually revoke read/write access to it once most users have upgraded.
• Firebase App Check: Configure App Check to only allow requests from your official, signed app builds. This blocks unauthorized third-party APKs, though you'll still need to combine it with version checks to block old official builds.

Key Notes #

• Make sure all v15+ apps correctly send the version parameter/claim—otherwise, they'll get blocked too!
• For custom claims, anonymous users will lose their claim if they log out and back in, so re-set it on every app launch.

内容的提问来源于stack exchange，提问作者user119949