# Managing users

This topic explains how to perform the following user management tasks:

Creating a secure login process

For general recommendations on how to securely handle user registration and login, see Creating a secure login process between your app and server.

# Getting user profiles

If the login request is sent with the .profile scope, you can get the user's LINE profile information. The user profile includes the user ID, display name, profile media (image or video), and status message.

Call the API.getProfile method as below:

API.getProfile { result in
    switch result {
    case .success(let profile):
        print("User ID: \(profile.userID)")
        print("User Display Name: \(profile.displayName)")
        print("User Status Message: \(profile.statusMessage)")
        print("User Icon: \(String(describing: profile.pictureURL))")
    case .failure(let error):
        print(error)
    }
}

The API.getProfile method gets the values at the time of login while users can change their display name, profile media, and status message anytime in LINE. To identify users, use the value of the userID property that doesn't change.

# Using ID tokens to verify user identities

The OpenID Connect 1.0 specification is an identity layer on top of the OAuth 2.0 protocol. With OpenID Connect, you can securely exchange information with the LINE Platform. Currently, you can get the user profile and email address from the LINE Platform by issuing ID tokens that conform to the OpenID Connect specification.

# Applying for email permission

You can request users who log in using LINE Login to grant your app the permission to get their email address. To do so, apply for the permission in the console. For more information, see Applying for email permission in the LINE Login guide.

# Login with the OpenID and email scopes

Once your channel has the email permission, you can let users log in with the .openID and .email scopes to get the user's email address from the ID token as below:

LoginManager.shared.login(permissions: [.openID, .email], in: self) {
    result in
    switch result {
    case .success(let loginResult):
        if let email = loginResult.accessToken.IDToken?.payload.email {
            print("User Email: \(email)")
        }
    case .failure(let error):
        print(error)
    }
}

An ID token is a signed JSON Web Token. The LINE SDK validates the token by checking its signature and expiration date for you, to prevent any malformed data in it.

# Using ID tokens on your server

User impersonation

Do not trust user IDs or other information sent by a client to your backend server. A malicious client can send an arbitrary user ID or malformed information to your server to impersonate a user.

Instead, the client should send the raw ID token string to your server. After verifying the token against the ID token verification API, the server can retrieve the user ID or any other information.

# Sending raw ID token string

When logging in with the .openID permission, you can assign a custom value to the IDTokenNonce parameter:

var parameters = LoginManager.Parameters()
parameters.IDTokenNonce = "<a randomly-generated string>"
LoginManager.shared.login(permissions: [.profile, .openID], parameters: parameters) {
    result in
    // ...
}

Although LINE SDK automatically assigns a value to IDTokenNonce if no value is specified, we recommend randomly generating a nonce value on your server and also storing it there. You can later use the original nonce to verify the ID token using the Social API. Verifying ID tokens helps prevent replay attacks.

After a successful login with the .openID permission, you can get the raw ID token string like this:

LoginManager.shared.login(permissions: [.profile, .openID], parameters: parameters) {
    result in
    switch result {
    case .success(let loginResult):
        if let idToken = loginResult.accessToken.IDTokenRaw {
            // Send `idToken` to your server.
        } else {
            // Something went wrong. You should fail the login.
        }
        
    case .failure(let error):
        print(error)

You can then send the idToken to your server to be verified.

# Verify ID token on your server

After receiving the ID token, your server should send both the token and the corresponding nonce value to LINE's ID token verification endpoint. If the token is valid, the API returns a JSON-formatted object containing ID token claims.

Learn more about what APIs to call from your backend on these pages:

# Treating user data carefully

Do not save any sensitive user data in plain text in your app or server, or transfer them through non-secure HTTP communication. Such data includes the access token, user ID, username, and any information in the ID token. The LINE SDK will store the user's access token for you. If needed, you can access it after authorization with the code below:

if let token = AccessTokenStore.shared.current {
    print(token.value)
}

ID tokens are issued only at the time of login. To update the ID token, you need to have the user log in again. However, if you set the .profile scope in the login request, you can call the API.getProfile method to get the user's profile information.

# Logging out users

You can log out users from your app. To create a better user experience, we recommend providing a way for users to log out of your app.

To invalidate the access token and log out the user from your app, call the logout method. The user is logged out of your app when you invalidate the access token. After logging out, the user must go through the login process again to log in.

LoginManager.shared.logout { result in
    switch result {
    case .success:
        print("Logout from LINE")
    case .failure(let error):
        print(error)
    }
}