Spring Security 之"记住我"功能

1. Overview

This article will show how to set up the Remember Me functionality in Spring Security – using not the standard cookie only approach but a more secure solution, using persistence.

As a quick intro – Spring can be configured to remember login details between browser sessions. This allows you to login to a website and then have it automatically log you back in the next time you visit the site (even if you have closed the browser in the meantime).

2. Two “Remember Me” Solutions

Spring provides two slightly different implementations to solve the problem. Both use the UsernamePasswordAuthenticationFilter, using hooks to invoke a RememberMeServices implementation.

We already covered the standard Remember Me solution, using only a cookie, in a previous article. This solution used a cookie called remember-me – containing the username, expiration time and MD5 hash containing the password. Because it contains a hash of the password, this solution is potentially vulnerable if the cookie is captured.

With that in mind – let's take a look at the second approach – using PersistentTokenBasedRememberMeServices to store the persisted login information in a database table between sessions.

3. Prerequisites – Create the Database Table

First – we need to have the login information in the database – we need a table creating to hold the data:

create table if not exists persistent_logins ( 
  username varchar_ignorecase(100) not null, 
  series varchar(64) primary key, 
  token varchar(64) not null, 
  last_used timestamp not null 
);

This is created automatically on startup via the following XML configuration (using an in-memory H2 db):

<!-- create H2 embedded database table on startup -->
<jdbc:embedded-database id="dataSource" type="H2">
    <jdbc:script location="classpath:/persisted_logins_create_table.sql"/> 
</jdbc:embedded-database>

And for the sake of completeness, here is the way persistence is set up:

@Configuration
@EnableTransactionManagement
@PropertySource({ "classpath:persistence-h2.properties" })
public class DatabaseConfig {

    @Autowired private Environment env;

    @Bean
    public DataSource dataSource() {
        DriverManagerDataSource dataSource = new DriverManagerDataSource();
        dataSource.setDriverClassName(env.getProperty("jdbc.driverClassName"));
        dataSource.setUrl(env.getProperty("jdbc.url"));
        dataSource.setUsername(env.getProperty("jdbc.user"));
        dataSource.setPassword(env.getProperty("jdbc.pass"));
        return dataSource;
    }
}

4. The Spring Security Configuration

The first key configuration is the Remember-Me Http Configuration (notice the dataSource property):

<http use-expressions="true">
    ...
    <remember-me data-source-ref="dataSource" token-validity-seconds="86400"/>
<http">

Next – we need to configure the actual RememberMeService and the JdbcTokenRepository (which also makes use of the dataSource):

<!-- Persistent Remember Me Service -->
<beans:bean id="rememberMeAuthenticationProvider" class=
  "org.springframework.security.web.authentication.rememberme.PersistentTokenBasedRememberMeServices">
    <beans:constructor-arg value="myAppKey" />
    <beans:constructor-arg ref="jdbcTokenRepository" />
    <beans:constructor-arg ref="myUserDetailsService" />
</beans:bean>
 
<!-- Uses a database table to maintain a set of persistent login data -->
<beans:bean id="jdbcTokenRepository" 
  class="org.springframework.security.web.authentication.rememberme.JdbcTokenRepositoryImpl"> 
    <beans:property name="createTableOnStartup" value="false" /> 
    <beans:property name="dataSource" ref="dataSource" /> 
</beans:bean>

<!-- Authentication Manager (uses same UserDetailsService as RememberMeService)--> 
<authentication-manager alias="authenticationManager"> 
    <authentication-provider user-service-ref="myUserDetailsService"/> 
    </authentication-provider> 
</authentication-manager>

As we mentioned, the standard TokenBasedRememberMeServices was storing the hashed user password in the cookie.

This solution – the PersistentTokenBasedRememberMeServices uses a unique series identifier for the user. This identifies the initial login of the user and remains constant each time the user gets logged in automatically during that persistent session. It also contains a random token that is regenerated each time a user logs in via the persisted remember-me functions.

This combination of randomly generated series and token are persisted, making a brute force attack very unlikely.

6. In Practice

To see the remember me mechanism working in a browser, you can:

Login with Remember Me active
Close the browser
Re-open the browser and return to the same page. Refresh.
You will still be logged in

Without Remember Me active, after the cookie expires the user should be redirected back to the login page. With remember me, the user now stays logged in with the help of the new token/cookie.

You can also view the cookies in the browser, and the persisted data in the database (note – you may want to switch from the embedded H2 implementation for this).

7. Conclusion

This tutorial illustrated how to set up and configure a database persisted Remember Me Token functionality. It is also a follow-up to the previous article which discussed the standard Cookie Token-based functionality. The Database approach is more secure as password details are not persisted in the cookie – but it does involve slightly more configuration.

The implementation of this Spring Security REST Tutorial can be found in the GitHub project – this is an Eclipse-based project, so it should be easy to import and run as it is.

Persistence

REST

Security