Securing Spring Boot API with API key and secret

I would like to secure the Spring Boot API so it is accessible only for the clients that has valid API key and secret. However, there is no authentication (standard login with username and password) inside the program as all data is anonymous. All I'm trying to achieve is that all API requests can be used only for specific third party front-end.

I found a lot of articles about how to secure the Spring Boot API with user authentication. But I don't need user authentication. What I am thinking of is just provide my client with API key and secret so he has access to the endpoints.

Could you please suggest me how can I achieve this? Thank you!

Create a filter that grabs what ever header(s) you're using for authentication.

import org.springframework.security.web.authentication.preauth.AbstractPreAuthenticatedProcessingFilter;

public class APIKeyAuthFilter extends AbstractPreAuthenticatedProcessingFilter {

    private String principalRequestHeader;

    public APIKeyAuthFilter(String principalRequestHeader) {
        this.principalRequestHeader = principalRequestHeader;
    }

    @Override
    protected Object getPreAuthenticatedPrincipal(HttpServletRequest request) {
        return request.getHeader(principalRequestHeader);
    }

    @Override
    protected Object getPreAuthenticatedCredentials(HttpServletRequest request) {
        return "N/A";
    }

}

Configure the filter in your Web Security config.

import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.annotation.Order;
import org.springframework.security.authentication.AuthenticationManager;
import org.springframework.security.authentication.BadCredentialsException;
import org.springframework.security.config.annotation.web.builders.HttpSecurity;
import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
import org.springframework.security.config.annotation.web.configuration.WebSecurityConfigurerAdapter;
import org.springframework.security.config.http.SessionCreationPolicy;
import org.springframework.security.core.Authentication;
import org.springframework.security.core.AuthenticationException;

@Configuration
@EnableWebSecurity
@Order(1)
public class APISecurityConfig extends WebSecurityConfigurerAdapter {

    @Value("${yourapp.http.auth-token-header-name}")
    private String principalRequestHeader;

    @Value("${yourapp.http.auth-token}")
    private String principalRequestValue;

    @Override
    protected void configure(HttpSecurity httpSecurity) throws Exception {
        APIKeyAuthFilter filter = new APIKeyAuthFilter(principalRequestHeader);
        filter.setAuthenticationManager(new AuthenticationManager() {
        
            @Override
            public Authentication authenticate(Authentication authentication) throws AuthenticationException {
                String principal = (String) authentication.getPrincipal();
                if (!principalRequestValue.equals(principal))
                {
                    throw new BadCredentialsException("The API key was not found or not the expected value.");
                }
                authentication.setAuthenticated(true);
                return authentication;
            }
        });
        httpSecurity.
            antMatcher("/api/**").
            csrf().disable().
            sessionManagement().sessionCreationPolicy(SessionCreationPolicy.STATELESS).
            and().addFilter(filter).authorizeRequests().anyRequest().authenticated();
    }

}

I realize I am a little late to the game on this one, but I also managed to get API keys working with Spring Boot in tandem with user-name/password authentication. I wasn't crazy about the idea of using AbstractPreAuthenticatedProcessingFilter because in reading the JavaDoc, it seemed like a misuse of that particular class.

I ended up creating a new ApiKeyAuthenticationToken class along with a pretty simple raw servlet filter to accomplish this:

import java.util.Collection;

import org.springframework.security.authentication.AbstractAuthenticationToken;
import org.springframework.security.core.GrantedAuthority;
import org.springframework.security.core.Transient;

@Transient
public class ApiKeyAuthenticationToken extends AbstractAuthenticationToken {

    private String apiKey;
    
    public ApiKeyAuthenticationToken(String apiKey, Collection<? extends GrantedAuthority> authorities) {
        super(authorities);
        this.apiKey = apiKey;
        setAuthenticated(true);
    }

    @Override
    public Object getCredentials() {
        return null;
    }

    @Override
    public Object getPrincipal() {
        return apiKey;
    }
}

And the filter

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.security.core.authority.AuthorityUtils;
import org.springframework.security.core.context.SecurityContextHolder;

public class ApiKeyAuthenticationFilter implements Filter {

    static final private String AUTH_METHOD = "api-key";
    
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException
    {
        if(request instanceof HttpServletRequest && response instanceof HttpServletResponse) {
            String apiKey = getApiKey((HttpServletRequest) request);
            if(apiKey != null) {
                if(apiKey.equals("my-valid-api-key")) {
                    ApiKeyAuthenticationToken apiToken = new ApiKeyAuthenticationToken(apiKey, AuthorityUtils.NO_AUTHORITIES);
                    SecurityContextHolder.getContext().setAuthentication(apiToken);
                } else {
                    HttpServletResponse httpResponse = (HttpServletResponse) response;
                    httpResponse.setStatus(401);
                    httpResponse.getWriter().write("Invalid API Key");
                    return;
                }
            }
        }
        
        chain.doFilter(request, response);
        
    }

    private String getApiKey(HttpServletRequest httpRequest) {
        String apiKey = null;
        
        String authHeader = httpRequest.getHeader("Authorization");
        if(authHeader != null) {
            authHeader = authHeader.trim();
            if(authHeader.toLowerCase().startsWith(AUTH_METHOD + " ")) {
                apiKey = authHeader.substring(AUTH_METHOD.length()).trim();
            }
        }
        
        return apiKey;
    }
}

All that is left at this point is to inject the filter at the proper location in the chain. In my case, I wanted API key authentication to be evaluated before any user-name / password authentication so that it could authenticate the request before the application tried to redirect to a login page:

@Override
protected void configure(HttpSecurity http) throws Exception {
    http
        .csrf()
            .disable()
        .addFilterBefore(new ApiKeyAuthenticationFilter(), UsernamePasswordAuthenticationFilter.class)
        .authorizeRequests()
            .anyRequest()
                .fullyAuthenticated()
                .and()
        .formLogin();
}

One other thing I will say you should watch out for is that your API key authenticated requests don't create and abandon a bunch of HttpSessions on your server.

The answer from the @MarkOfHall is correct and I just want to add a little more details. After you have the code, you will need to add the property values to the application.properties file as below:

yourapp.http.auth-token-header-name=X-API-KEY
yourapp.http.auth-token=abc123

The set the authentication value in the Postman as below:

You can use Postman but if you use cURL request will be similar provided below:

$ curl -H "X-API-KEY: abc123" "http://localhost:8080/api/v1/property/1"

Unless if provide the correct key and value, the app will not work.