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# 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 Scope.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 LineApiClient.getProfile() method as below:

LineProfile profile = lineApiClient.getProfile().getResponseData()
Log.i(TAG, profile.getDisplayName());
Log.i(TAG, profile.getUserId());
Log.i(TAG, profile.getStatusMessage());
Log.i(TAG, profile.getPictureUrl().toString());

The getDisplayName(), getPictureURL(), and getStatusMessage() methods get the values at the time of login while users can change those values anytime in LINE. To identify users, use the getUserId() method, whose return value, user ID, doesn't change.

You can change the size of the user’s profile image by adding a suffix to the URL.

Image Size Suffix
200 x 200 /large
51 x 51 /small

# Using ID tokens to verify user identities

The OpenID Connect (opens new window) 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 LINE Developers 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 the users log in with the Scope.OPENID_CONNECT and Scope.OC_EMAIL scopes to get the user's email address from the ID token as below:

import java.util.Arrays;

private static final int REQUEST_CODE = 1;

LineAuthenticationParams params = new LineAuthenticationParams.Builder()
				        .scopes(Arrays.asList(Scope.OPENID_CONNECT, Scope.OC_EMAIL))
				        .build();

Intent loginIntent = LineLoginApi.getLoginIntent(
	            view.getContext(),
	            Constants.CHANNEL_ID,
	            params);

startActivityForResult(loginIntent, REQUEST_CODE);

An ID token is a signed JSON Web Token (opens new window). The LINE SDK validates the token by checking its signature and expiration date for you, to prevent any malformed data in it. If the validation passes, you can get a LineIdToken instance in the onActivityResult() callback as below:

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);
    if (requestCode != REQUEST_CODE) {
        Log.e("ERROR", "Unsupported Request");
        return;
    }

    LineLoginResult result = LineLoginApi.getLoginResultFromIntent(data);

    switch (result.getResponseCode()) {
        case SUCCESS:     
            // Login successful
            LineIdToken lineIdToken = result.getLineIdToken();
            Log.v("INFO", lineIdToken.getEmail());
    ...
    }
}    

# Using ID token 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 Scope.OPENID_CONNECT scope, you can assign a custom value to the nonce parameter:

private static final int REQUEST_CODE = 1;
...
LineAuthenticationParams params = new LineAuthenticationParams.Builder()
                                  ...
                                  .nonce("<a randomly-generated string>")
                                  .build();

Intent loginIntent = LineLoginApi.getLoginIntent(
                        view.getContext(),
                        Constants.CHANNEL_ID,
                        params);

startActivityForResult(loginIntent, REQUEST_CODE);

Although LINE SDK automatically assigns a value to nonce 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 (opens new window).

After a successful login with the Scope.OPENID_CONNECT scope, you can get the raw ID token string like this:

public void onActivityResult(int requestCode, int resultCode, Intent data) {
    ...
    LineLoginResult result = LineLoginApi.getLoginResultFromIntent(data);

    switch (result.getResponseCode()) {
        case SUCCESS:     
            // Login successful
            LineIdToken lineIdToken = result.getLineIdToken();
            String idTokenStr = lineIdToken.getRawString();
            if (idTokenStr != null) {
                // Send `idTokenStr` to your server.
            } else {
                // Something went wrong. You should fail the login.
            }
    ...
}

You can then send the idTokenStr 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:

LineAccessToken accessToken = lineApiClient.getCurrentAccessToken().getResponseData();

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 Scope.PROFILE scope in the login request, you can call the LineApiClient.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.

lineApiClient.logout();