Cloud Hosting

Traditionally, security has been one of the most complex parts of appdevelopment. In most applications, developers must build and run a server thathandles authentication (who a user is) and authorization (what a user can do).Authentication and authorization are hard to set up, harder to get right, andcritical to the success of your product.

Similar to how Firebase Authentication makes it easy for you to authenticate yourusers, Firebase Security Rules for Cloud Storage makes it easy for you to authorize usersand validate requests. Cloud Storage Security Rules manage the complexity for you byallowing you to specify path based permissions. In just a few lines of code, youcan write authorization rules that restrict Cloud Storage requests to acertain user or limit the size of an upload.

The Firebase Realtime Database has a similar feature, calledFirebase Realtime Database Rules

Knowing who your users are is an important part of building an application, andFirebase Authentication provides an easy to use, secure, client side only solutionto authentication. Firebase Security Rules for Cloud Storage ties in to Firebase Authenticationfor user based security. When a user is authenticated with Firebase Authentication,the request.auth variable in Cloud Storage Security Rules becomes an object thatcontains the user's unique ID (request.auth.uid) and all other userinformation in the token (request.auth.token). When the user is notauthenticated, request.auth is null. This allows you to securely controldata access on a per-user basis. You can learn more in theAuthentication section.

Identifying your user is only part of security. Once you know who they are, youneed a way to control their access to files in Cloud Storage.

Cloud Storage lets you specify per file and per path authorizationrules that live on our servers and determine access to the files in your app.For example, the default Cloud Storage Security Rules require Firebase Authentication inorder to perform any read or write operations on all files:

You can edit these rules by selecting a Firebase app in the Firebase consoleand viewing the Rules tab of the Storage section.

Firebase Security Rules for Cloud Storage can also be used for data validation, includingvalidating file name and path as well as file metadata properties such ascontentType and size.

Read more:
Understand Firebase Security Rules for Cloud Storage | Firebase Storage