Classroom Exercise Instructions

Exercise 1 - Basic Authentication

Pre-requisites

• Import this repository into your own GitHub account and name it BasicAuth.
• Open the repository in Codespaces.
• Import Java Projects.
• Change the visibility of port 8080 to public after starting the application.

Step 1 - Add Spring Security

In pom.xml add the spring security dependency.

• Right click and choose “Add Starters…”
  • Search for “spring boot starter security” and choose “Spring Security”
  • Hit Enter to continue

OR copy the following in pom.xml

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>

Step 2 - Add an Approach for Security

Approach 1 - Use Default Username and Password for Authentication

• Start the application and note the generated password in the terminal

  • Copy the password
  • Open the app in the browser by copying the URL and appending /login; the login page should open
  • Enter username: user and password:{copied password} to get access to the endpoint

• This approach has some drawbacks. Hence, used only for unit testing purposes.

  • Password is regenerated every time server starts!
  • Accessible only from logs; end users do not have access to logs!

Approach 2 - Use Customized Username and Password for Authentication

Let's try a better approach of defining our own username and password.

• Enter the following properties in resources/application.properties

spring.security.user.name=${MYUSERNAME}
spring.security.user.password=${MYPASSWORD}

• First, try to set custom username and password by replacing ${MYUSERNAME} and ${MYPASSWORD}
• However, it's not safe to save username and password directly. Let's create environment variables to store the username and password and inject them in the properties:
  • Go to Repository Settings > Secrets and Variables, Codespaces
  • Click on New Repository Secrets
    • Name: myusername, Value: {your username}
    • Name: mypassword, Value: {your password}
• You will be prompted to re-build the container. If not, re-build it manually by clicking the codespace name in the left bottom corner and choosing the "Rebuild Container" command.
• Run the app and enter the configured username and password on the login page
• The drawback of this approach is that only one user can be created and roles cannot be assigned.

Approach 3 - Add Security Config

Let's secure individual endpoints by creating some roles.

• If you tried Approach 2 above, delete the username and password properties from application.properties
• Add the following two GET mappings in the MyController.java:

@GetMapping("/admin")
public ResponseEntity<String> showAdminContent(Principal principal) {
    String message = "Welcome, " + principal.getName() + "! <BR> Only an admin can view this content.";
    return new ResponseEntity<>(message, HttpStatus.OK);
}

@GetMapping("/user")
public ResponseEntity<String> showUserContent(Principal principal) {
    String message = "Welcome, " + principal.getName() + "! <BR> Only a user can view this content.";
    return new ResponseEntity<>(message, HttpStatus.OK);
}

OR let AI Copilot generate these suggestions for you 😊

Next, we need to override the default security configuration included in Spring Boot. For that, we will have to create a custom configuration class.

• Create Custom Security Config Class
  • Create a new package ch.fhnw.securitytest.security and a new class SecurityConfig.java
  • Add the following class-level annotations: @Configuration @EnableWebSecurity @EnableMethodSecurity
• Inside SecurityConfig.java, add a bean that will replace the default implementation of UserDetailsService
  • Create two custom users with roles USER and ADMIN, respectively
  • Use the custom user details to perform in-memory authentication

@Configuration
@EnableWebSecurity
@EnableMethodSecurity
public class SecurityConfig {

    @Bean
    public UserDetailsService users() {
        //Create two users with different roles and add them to the in-memory user store

        return new InMemoryUserDetailsManager(
            User.withUsername("myuser")
                .password("{noop}password")
                .authorities("READ","ROLE_USER")
                .build(), 
            User.withUsername("myadmin")
                .password("{noop}password")
                .authorities("READ","ROLE_ADMIN")
                .build());

    }
}

Now we need to add a Security Filter Chain implementation.

• Add another bean inside SecurityConfig.java that will customize SecurityFilterChain implementation in Spring Boot

  • Disable csrf. We are not using cookies as we are developing a REST API. Hence, it is safe to disable CSRF.
  • Add role-based access to the /securitytest/admin and /securitytest/user endpoints
  • Add a form login to use Spring Security’s default login form
  • Use HTTP Basic Authentication on the two users created: myuser and myadmin

  @Bean
  public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
      return http
              .csrf(csrf -> csrf.disable())
              .authorizeHttpRequests( auth -> auth
                      .requestMatchers("/securitytest/admin").hasRole("ADMIN") //note that the role need not be prefixed with "ROLE_"
                      .requestMatchers("/securitytest/user").hasRole("USER") //note that the role need not be prefixed with "ROLE_"
                      .requestMatchers("/securitytest/**").permitAll()            
              )       
              .formLogin(withDefaults()) //need to include a static import for withDefaults, see the imports at the top of the file
              .httpBasic(withDefaults())
              .build(); 
  } 

• Test the endpoints on a browser or using Postman.

Exercise 2 - Token-based Authentication

Pre-requisites

• Import this repository into your own GitHub account and name it JWT_OAuth.
• Open the repository in Codespaces.
• Import Java Projects.
• Change the visibility of port 8080 to public after starting the application.

Step 1 - Add Spring Security

• In pom.xml add the spring security dependency.
• Right click and choose “Add Starters…”
  • Search for “spring boot starter security” and choose “Spring Security”
  • Hit Enter to continue

OR copy the following in pom.xml

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-security</artifactId>
</dependency>

• Add another dependency for OAuth2 Resource Server:
  • Right click and choose “Add Starters…”
  • Search for “oauth2” and choose “OAuth2 Resource Server”
  • Hit Enter to continue OR copy the following in pom.xml

<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-oauth2-resource-server</artifactId>
</dependency>

• Add individual endpoints
  • Add the following GET mapping in MyController.java:

  @GetMapping("/safe")
  public ResponseEntity<String> showSafeContent() {
      return new ResponseEntity<>("Only a token bearer can view this content.", HttpStatus.OK);
  }

OR let AI Copilot generate these suggestions for you 😊

• Define a JWT Key
  • We need to define a JWT Key which will be used to encode the token
  • Add it in application.properties

  # should be at least 64 characters
  jwt.key=mysecret-which-needs-to-be-of-at-least-512bit-long!please-change

• Create Custom Security Config Class
  • Create a new package ch.fhnw.securitytest.security and a new class SecurityConfig.java
  • Add the following class-level annotations: @Configuration @EnableWebSecurity @EnableMethodSecurity
• Inside SecurityConfig.java:
  • Inject the value of JWT Key
  • Add a bean that will replace the default implementation of UserDetailsService
  • Create one custom user with the role USER
  • Use the custom user details to perform in-memory authentication

@Configuration
@EnableWebSecurity
@EnableMethodSecurity
public class SecurityConfig {

    @Value("${jwt.key}")
    private String jwtKey;

    @Bean
    public UserDetailsService userDetailsService() {
        return new InMemoryUserDetailsManager(
            User.withUsername("myuser")
                    .password("{noop}password")
                    .authorities("READ","ROLE_USER")
                    .build());
        
    }
}

Now we need to add a Security Filter Chain implementation.

• Add another bean inside SecurityConfig.java that will customize SecurityFilterChain implementation in Spring Boot

  • Disable csrf. We are not using cookies as we are developing a REST API. Hence, it is safe to disable CSRF.
  • Add role-based access to the /securitytest/safe endpoint
  • Set SessionManagement to STATELESS
  • Use HTTP Basic Authentication on the custome user: myuser

  @Bean
  public SecurityFilterChain securityFilterChain(HttpSecurity http) throws Exception {
      return http
              .csrf(csrf -> csrf.disable())
              .authorizeHttpRequests( auth -> auth
                      .requestMatchers("/securitytest/token").hasRole("USER") //only custom users with role USER can request a token
                      .anyRequest().hasAuthority("SCOPE_READ") // only requests with scope inside the JWT token can access the endpoints        
              )
              .sessionManagement(session -> session.sessionCreationPolicy(SessionCreationPolicy.STATELESS))
              .oauth2ResourceServer(oAuth -> oAuth.jwt(Customizer.withDefaults()))
              .httpBasic(withDefaults())
              .build(); 
  }

Next, we need to define an encoder and decoder for our access tokens using the defined jwt.key

• Inside SecurityConfig.java, define a bean that uses an implementation JWT encoder
• Define another bean that uses the same algorithm that was used to sign the token to decode it

@Bean
    JwtEncoder jwtEncoder() {
        return new NimbusJwtEncoder(new ImmutableSecret<>(jwtKey.getBytes()));
    }

    @Bean
    public JwtDecoder jwtDecoder() {
        byte[] bytes = jwtKey.getBytes();
        SecretKeySpec originalKey = new SecretKeySpec(bytes, 0, bytes.length,"RSA");
        return NimbusJwtDecoder.withSecretKey(originalKey).macAlgorithm(MacAlgorithm.HS512).build();
    }

Defining an encoder and decoder bean is not enough. Next, we need to actually generate a token and issue it. For this, we need to create another service class.

• Add a new package ch.fhnw.securitytest.security and a new class TokenService.java
• Add the class level annotation @Service
• Add a JWT encoder and a constructor

@Service
public class TokenService {

    //use the encoder bean from SecurityConfig
    private final JwtEncoder encoder;

    //Inject into the constructor
    public TokenService(JwtEncoder encoder) {
        this.encoder = encoder;
    }
}

• Add a method to generate a new token

public String generateToken(Authentication authentication) {
        // note the current time to determine the issuedAt and expiresAt
        Instant now = Instant.now(); 

        // the scope is the JWT scope SCOPE_READ which is checked in SecurityConfig during authentication, this is not the role-based scope
        String scope = authentication.getAuthorities().stream()
                .map(GrantedAuthority::getAuthority)
                .filter(authority -> !authority.startsWith("ROLE"))
                .collect(Collectors.joining(" "));

        // create the JWT claims - name/value pairs
        JwtClaimsSet claims = JwtClaimsSet.builder()
                .issuer("self") //issuer by this application
                .issuedAt(now) //issued now
                .expiresAt(now.plus(1, ChronoUnit.HOURS)) //expires in 1 hour
                .subject(authentication.getName()) //subject is the username
                .claim("scope", scope) //scope is the scope created above
                .build();

        // create the JWT encoder parameters
        var encoderParameters = JwtEncoderParameters.from(JwsHeader.with(MacAlgorithm.HS512).build(), claims); //use the symmetric key algorithm HS512 for signing the JWT
        return this.encoder.encode(encoderParameters).getTokenValue(); //encode the JWT and return the token value
    }

Let's add an endpoint in our controller to generate the token for authentication.

• Add an endpoint to retrieve the JWT token
  • Inject the TokenService in MyController.java

  private final TokenService tokenService;
  
  public MyController(TokenService tokenService) {
      this.tokenService = tokenService;
  }

  • Add the following POST mapping in MyController.java

  @PostMapping("/token")
  public String token(Authentication authentication) {
      if (authentication.isAuthenticated()) { //requires a valid user (created in SecurityConfig.java)
          return tokenService.generateToken(authentication);
      } else {
          throw new UsernameNotFoundException("invalid user request !");
      }
  }

Let's test the endpoints using Postman.

• Start the application
• Change the port visibility to “public” otherwise you will not see the response in Postman
• Copy the local address ({baseURL}) of the running application
• Create a new request in Postman
  • Method: POST
  • URL: {baseURL}/securitytest/token
  • In the Authorization tab, choose/enter the following:
    • Basic Auth
    • Username: myser
    • Password: password
• Send the request
• In the response, you should receive the encoded JWT

Using this token, now you can access the secured endpoint.

• Copy the token from the previous response
• Create a new request in Postman
  • Method: GET
  • URL: {baseURL}/securitytest/safe
  • In the Authorizatio tab
    • Choose Bearer Token
    • Paste the token
• Send the request
• In the response, you should see the appropriate content sent by the server.