Developers are increasingly turning to Kotlin for web development. Kotlin is a concise, safe, interoperable, and tool-friendly language that runs on the Java Virtual Machine.
Spring Security is a powerful and highly customizable authentication and access-control framework. It is the de-facto standard for securing Spring-based applications.
In this article, we'll explore how to use Kotlin and Spring Security to secure a web application. We'll look at how to configure Spring Security and write Kotlin code to implement common security features such as authentication, authorization, and password encryption.
Spring Security can be configured using Java or Kotlin code. In this section, we'll look at how to configure Spring Security using Kotlin.
To add Spring Security to your project, add the following dependencies to your build.gradle.kts
file:
implementation("org.springframework.boot:spring-boot-starter-security")
implementation("org.springframework.security.oauth.boot:spring-security-oauth2-autoconfigure")
Next, we'll create a SecurityConfig
class to configure Spring Security. This class will extend WebSecurityConfigurerAdapter
and override its configure
method:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
// ...
}
}
In the configure
method, we can configure various aspects of Spring Security such as authentication, authorization, and session management.
Spring Security supports a wide range of authentication mechanisms, from simple username/password authentication to more sophisticated mechanisms such as OAuth2 and LDAP.
In this example, we'll configure Spring Security to use username/password authentication. We'll store the username and password in a database using the UserDetailsService
interface:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
http.authorizeRequests()
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic()
.and()
.logout()
}
@Autowired
fun configureGlobal(auth: AuthenticationManagerBuilder) {
auth.inMemoryAuthentication()
.withUser("user").password("{noop}password").roles("USER")
}
}
In the code above, we've configured Spring Security to use username/password authentication. We've also configured a UserDetailsService
to store the username and password in memory.
Once a user has been authenticated, we need to configure authorization to control what they can do within the application.
Spring Security supports two types of authorization:
In this example, we'll configure role-based authorization. We'll configure two roles: USER
and ADMIN
. Users with the USER
role will be able to access the /user
endpoint, while users with the ADMIN
role will be able to access the /admin
endpoint:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
http.authorizeRequests()
.antMatchers("/user").hasRole("USER")
.antMatchers("/admin").hasRole("ADMIN")
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic()
.and()
.logout()
}
@Autowired
fun configureGlobal(auth: AuthenticationManagerBuilder) {
auth.inMemoryAuthentication()
.withUser("user").password("{noop}password").roles("USER")
.and()
.withUser("admin").password("{noop}password").roles("ADMIN")
}
}
In the code above, we've configured role-based authorization using the hasRole
method. We've also configured a UserDetailsService
to store the username and password in memory.
Spring Security supports a wide range of password encryption algorithms. In this example, we'll configure Spring Security to use the bcrypt
algorithm:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
http.authorizeRequests()
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic()
.and()
.logout()
.and()
.apply {
passwordEncoder(BCryptPasswordEncoder())
}
}
@Autowired
fun configureGlobal(auth: AuthenticationManagerBuilder) {
auth.inMemoryAuthentication()
.withUser("user").password("{noop}password").roles("USER")
.and()
.withUser("admin").password("{noop}password").roles("ADMIN")
}
}
In the code above, we've configured Spring Security to use the BCryptPasswordEncoder
to encrypt passwords. We've also configured a UserDetailsService
to store the username and password in memory.
In this section, we'll look at how to write Kotlin code to implement common security features such as authentication, authorization, and password encryption.
To authenticate a user, we'll use the authenticationManager.authenticate
method:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
http.authorizeRequests()
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic()
.and()
.logout()
}
@Autowired
fun configureGlobal(auth: AuthenticationManagerBuilder) {
auth.inMemoryAuthentication()
.withUser("user").password("{noop}password").roles("USER")
.and()
.withUser("admin").password("{noop}password").roles("ADMIN")
}
@Autowired
fun authenticationManager(): AuthenticationManager {
return authenticationManager()
}
}
In the code above, we've injected the AuthenticationManager
into our SecurityConfig
class. We can then use the authenticationManager.authenticate
method to authenticate a user.
To authorize a user, we'll use the hasRole
method:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
http.authorizeRequests()
.antMatchers("/user").hasRole("USER")
.antMatchers("/admin").hasRole("ADMIN")
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic()
.and()
.logout()
}
@Autowired
fun configureGlobal(auth: AuthenticationManagerBuilder) {
auth.inMemoryAuthentication()
.withUser("user").password("{noop}password").roles("USER")
.and()
.withUser("admin").password("{noop}password").roles("ADMIN")
}
}
In the code above, we've used the hasRole
method to authorize users. We've also configured a UserDetailsService
to store the username and password in memory.
To encrypt passwords, we'll use the passwordEncoder
method:
@Configuration
@EnableWebSecurity
class SecurityConfig : WebSecurityConfigurerAdapter() {
override fun configure(http: HttpSecurity) {
http.authorizeRequests()
.anyRequest().authenticated()
.and()
.formLogin()
.and()
.httpBasic()
.and()
.logout()
.and()
.apply {
passwordEncoder(BCryptPasswordEncoder())
}
}
@Autowired
fun configureGlobal(auth: AuthenticationManagerBuilder) {
auth.inMemoryAuthentication()
.withUser("user").password("{noop}password").roles("USER")
.and()
.withUser("admin").password("{noop}password").roles("ADMIN")
}
}
In the code above, we've used the passwordEncoder
method to encrypt passwords. We've also configured a UserDetailsService
to store the username and password in memory.
In this article, we've explored how to use Kotlin and Spring Security to secure a web application. We've looked at how to configure Spring Security and write Kotlin code to implement common security features such as authentication, authorization, and password encryption.