# Remember-Me Authentication
Remember-me or persistent-login authentication refers to web sites being able to remember the identity of a principal between sessions. This is typically accomplished by sending a cookie to the browser, with the cookie being detected during future sessions and causing automated login to take place. Spring Security provides the necessary hooks for these operations to take place, and has two concrete remember-me implementations. One uses hashing to preserve the security of cookie-based tokens and the other uses a database or other persistent storage mechanism to store the generated tokens.
Note that both implementations require a
If you are using an authentication provider which doesn’t use a
UserDetailsService (for example, the LDAP provider) then it won’t work unless you also have a
UserDetailsService bean in your application context.
# Simple Hash-Based Token Approach
This approach uses hashing to achieve a useful remember-me strategy. In essence a cookie is sent to the browser upon successful interactive authentication, with the cookie being composed as follows:
base64(username + ":" + expirationTime + ":" + md5Hex(username + ":" + expirationTime + ":" password + ":" + key)) username: As identifiable to the UserDetailsService password: That matches the one in the retrieved UserDetails expirationTime: The date and time when the remember-me token expires, expressed in milliseconds key: A private key to prevent modification of the remember-me token
As such the remember-me token is valid only for the period specified, and provided that the username, password and key does not change. Notably, this has a potential security issue in that a captured remember-me token will be usable from any user agent until such time as the token expires. This is the same issue as with digest authentication. If a principal is aware a token has been captured, they can easily change their password and immediately invalidate all remember-me tokens on issue. If more significant security is needed you should use the approach described in the next section. Alternatively, remember-me services should simply not be used at all.
If you are familiar with the topics discussed in the chapter on namespace configuration, you can enable remember-me authentication just by adding the
<http> ... <remember-me key="myAppKey"/> </http>
UserDetailsService will normally be selected automatically.
If you have more than one in your application context, you need to specify which one should be used with the
user-service-ref attribute, where the value is the name of your
# Persistent Token Approach
This approach is based on the article http://jaspan.com/improved_persistent_login_cookie_best_practice (opens new window) with some minor modifications . To use the this approach with namespace configuration, you would supply a datasource reference:
<http> ... <remember-me data-source-ref="someDataSource"/> </http>
The database should contain a
persistent_logins table, created using the following SQL (or equivalent):
create table persistent_logins (username varchar(64) not null, series varchar(64) primary key, token varchar(64) not null, last_used timestamp not null)
# Remember-Me Interfaces and Implementations
Remember-me is used with
UsernamePasswordAuthenticationFilter, and is implemented via hooks in the
It is also used within
The hooks will invoke a concrete
RememberMeServices at the appropriate times.
The interface looks like this:
Authentication autoLogin(HttpServletRequest request, HttpServletResponse response); void loginFail(HttpServletRequest request, HttpServletResponse response); void loginSuccess(HttpServletRequest request, HttpServletResponse response, Authentication successfulAuthentication);
Please refer to the Javadoc for a fuller discussion on what the methods do, although note at this stage that
AbstractAuthenticationProcessingFilter only calls the
autoLogin() method is called by
RememberMeAuthenticationFilter whenever the
SecurityContextHolder does not contain an
This interface therefore provides the underlying remember-me implementation with sufficient notification of authentication-related events, and delegates to the implementation whenever a candidate web request might contain a cookie and wish to be remembered.
This design allows any number of remember-me implementation strategies.
We’ve seen above that Spring Security provides two implementations.
We’ll look at these in turn.
This implementation supports the simpler approach described in Simple Hash-Based Token Approach.
TokenBasedRememberMeServices generates a
RememberMeAuthenticationToken, which is processed by
key is shared between this authentication provider and the
TokenBasedRememberMeServices requires A UserDetailsService from which it can retrieve the username and password for signature comparison purposes, and generate the
RememberMeAuthenticationToken to contain the correct
Some sort of logout command should be provided by the application that invalidates the cookie if the user requests this.
TokenBasedRememberMeServices also implements Spring Security’s
LogoutHandler interface so can be used with
LogoutFilter to have the cookie cleared automatically.
The beans required in an application context to enable remember-me services are as follows:
<bean id="rememberMeFilter" class= "org.springframework.security.web.authentication.rememberme.RememberMeAuthenticationFilter"> <property name="rememberMeServices" ref="rememberMeServices"/> <property name="authenticationManager" ref="theAuthenticationManager" /> </bean> <bean id="rememberMeServices" class= "org.springframework.security.web.authentication.rememberme.TokenBasedRememberMeServices"> <property name="userDetailsService" ref="myUserDetailsService"/> <property name="key" value="springRocks"/> </bean> <bean id="rememberMeAuthenticationProvider" class= "org.springframework.security.authentication.RememberMeAuthenticationProvider"> <property name="key" value="springRocks"/> </bean>
Don’t forget to add your
RememberMeServices implementation to your
UsernamePasswordAuthenticationFilter.setRememberMeServices() property, include the
RememberMeAuthenticationProvider in your
AuthenticationManager.setProviders() list, and add
RememberMeAuthenticationFilter into your
FilterChainProxy (typically immediately after your
This class can be used in the same way as
TokenBasedRememberMeServices, but it additionally needs to be configured with a
PersistentTokenRepository to store the tokens.
There are two standard implementations.
InMemoryTokenRepositoryImplwhich is intended for testing only.
JdbcTokenRepositoryImplwhich stores the tokens in a database.
The database schema is described above in Persistent Token Approach.
1. Essentially, the username is not included in the cookie, to prevent exposing a valid login name unecessarily. There is a discussion on this in the comments section of this article.