[JAVA] Hash passwords with Spring Boot + Spring Security (with salt, with stretching)

Spring Security's Password Encoder makes it easy to generate salted + stretched hash values. This article is a sample.

environment

JDK：1.8 Spring Boot：1.5.3.RELEASE Spring Security：4.2.2.RELEASE

Spring Security PasswordEncoder Class Diagram It may be hard to see, but the class diagram of PasswordEncoder of Spring Security 4.2.2.RELEASE is as follows.

There are six implementation classes for the PasswordEncoder interface.

In this article, I will use BCryptPasswordEncoder for hashing.

Hashing with BCryptPasswordEncoder

Add a Spring Security dependency.

pom.xml

<dependency>
	<groupId>org.springframework.security</groupId>
	<artifactId>spring-security-core</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.security</groupId>
	<artifactId>spring-security-web</artifactId>
</dependency>
<dependency>
	<groupId>org.springframework.security</groupId>
	<artifactId>spring-security-config</artifactId>
</dependency>

This time, CommandLineRunner is implemented as CLI.

SpringBootEncodeApplication.java

package com.example;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.security.crypto.password.PasswordEncoder;

@SpringBootApplication
public class SpringBootEncodeApplication implements CommandLineRunner {

	@Autowired
	PasswordEncoder passwordEncoder;

	public static void main(String[] args) {
		SpringApplication.run(SpringBootEncodeApplication.class, args);
	}

	@Bean
	PasswordEncoder passwordEncoder() {
		return new BCryptPasswordEncoder();
	}

	@Override
	public void run(String... args) {

		String password = "#fe?3d31";
		String digest = passwordEncoder.encode(password);
		System.out.println("Hash value= " + digest);

		if (passwordEncoder.matches(password, digest)) {
			System.out.println("It matched");
			return;
		}
		System.out.println("It didn't match");
	}
}

Hash the plaintext password (password) using the PasswordEncoder's encode method. The hashed result is digest. Then use PasswordEncoder's matches method to match the plaintext password (password) with the hash value (digest) obtained by the encode method.

Execution result.

Hash value= $2a$10$im98CLRwtWohvPE6wZkYk.Os.RXZVF0iROJXL8vUn7TGrfWoixTdq
It matched

How to read the hash value

The hash value generated above is as follows.

$2a$10$im98CLRwtWohvPE6wZkYk.Os.RXZVF0iROJXL8vUn7TGrfWoixTdq

The view is as follows.

• Salt values, stretching, etc. are omitted here as they are out of the scope of this article.

As mentioned above, you can use Spring Security's PasswordEncoder to generate salt + stretched hash values, and you can easily match them with plaintext passwords.

• I'm talking about bcrypt.