Does Spring Security use Basic Auth or Form Based Authentication by default?

Question

I'm learning about Spring Security in Spring Boot app and I try to understand what authentication way uses Spring Security by default. I know that Spring Security uses form-based authentication by default, but I made a test from Postman using basic authentication and it's working.

I have a very simple Spring Boot app.

Rest Controller:

package com.dgs.demsec.api;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello World!";
    }
}

I added the spring-security dependency in the pom.xml:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.dgs</groupId>
    <artifactId>dem-sec</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>dem-sec</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
    </properties>

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

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>org.springframework.security</groupId>
            <artifactId>spring-security-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

And I don't have any configuration class for Spring Security. It is using the default configuration. I start the app then I try to access the endpoint: http://localhost:8080/hello after that I use the default username which is user and the password generated by Spring Security and it's working, the response is "Hello World!". In the Google Chrome developer tools, for /login endpoint there is no Authorization header, so it doesn't use the basic authentication. And I can see this in Form Data for /login endpoint:

So Spring Security uses form-based authentication by default. Then I made 2 request from Postman, the first with form-based authentication and the second with basic-authentication and both of them are working. So the request it's working also if I send the credentials in the Authorization header. Can someone explain why it's working to make a request using basic authentication if it's a form-based authentication? Thank you!

Answer 1

I have checked this in WebSecurityConfigurerAdapter.class and seems like by default it was using http.formLogin() and http.httpBasic() as initial configuration to authenticate any request.

    protected void configure(HttpSecurity http) throws Exception {
    this.logger.debug("Using default configure(HttpSecurity). If subclassed this will potentially override subclass configure(HttpSecurity).");
    http.authorizeRequests((requests) -> {
        ((AuthorizedUrl)requests.anyRequest()).authenticated();
    });
    http.formLogin();
    http.httpBasic();
}