What is this

If you have ever tried getting Let's Encrypt certificate for Spring Boot application, you know that it is painful as it involves using either CertBot or Docker-sidecar/Cron-job to manage certificate lifecycle, especially if it is small pet application. This library solves these problems by managing certificate lifecycle directly in Java code with the help of awesome Acme4j library.

Note: This version is for Spring Boot 3.x and Spring 6.x, for older Spring/Spring Boot versions see Release 0.2.5

Key features:

1. Obtain Let's Encrypt certificate on fresh start (or from other ACME compliant certificate provider)
2. Store generated keys and certificate into single KeyStore (server.ssl.keystore)
3. Renew Let's Encrypt certificate (it watches for certificate expiration date and updates it to new before old is expired)
4. No JVM restart needed when certificate gets updated

Application requirements

To perform HTTP-01 ACME (Automatic Certificate Management Environment) challenge, the application must listen on port 80, this library will automatically create Tomcat connector to this port, so the only thing needed on your side is to open 80 port for the application.

Servlet containers supported (embedded)

• Tomcat
• Jetty

Usage

From JitPack maven repository

1. Import this library:

For Tomcat:

Gradle:

 allprojects {
     repositories {
         ...
         maven { url 'https://jitpack.io' }
     }
 }

dependencies {
   implementation 'com.github.valb3r.letsencrypt-helper:letsencrypt-helper-tomcat:0.4.0'
}

Maven:

<repositories>
     <repository>
         <id>jitpack.io</id>
         <url>https://jitpack.io</url>
     </repository>
 </repositories>

<dependencies>
   <dependency>
      <groupId>com.github.valb3r.letsencrypt-helper</groupId>
      <artifactId>letsencrypt-helper-tomcat</artifactId>
      <version>0.4.0</version>
   </dependency>
</dependencies>

For Jetty:

Gradle:

 allprojects {
     repositories {
         ...
         maven { url 'https://jitpack.io' }
     }
 }

dependencies {
   implementation 'com.github.valb3r.letsencrypt-helper:letsencrypt-helper-jetty:0.4.0'
}

Maven:

<repositories>
     <repository>
         <id>jitpack.io</id>
         <url>https://jitpack.io</url>
     </repository>
 </repositories>

<dependencies>
   <dependency>
      <groupId>com.github.valb3r.letsencrypt-helper</groupId>
      <artifactId>letsencrypt-helper-jetty</artifactId>
      <version>0.4.0</version>
   </dependency>
</dependencies>

2. Declare on your configuration

Tomcat:

@Import(TomcatWellKnownLetsEncryptChallengeEndpointConfig.class)

Jetty:

@Import(JettyWellKnownLetsEncryptChallengeEndpointConfig.class)

3. Define following properties in your application configuration or environment:

1. lets-encrypt-helper.domain the domain to issue certificate for
2. lets-encrypt-helper.contact your contact for Let's Encrypt (i.e. your email in format mailto:john.doe@example.com)

4. Configure SSL as usual for Tomcat+TLS using server.ssl.keystore for certificate and keys storage

5. Ensure your security layer (i.e. Spring security) allows anonymous access to /.well-known/acme-challenge/* paths

Configuration

Property	Description	Default value, if any
server.ssl.key-store	Path to the KeyStore, where Let's Encrypt certificates and account key are to be stored (or are already there)
server.ssl.key-store	KeyStore type (i.e. PKCS12)
server.ssl.key-store-pasword	Password for KeyStore with Let's Encrypt certificate and account key
server.ssl.key-alias	Let's Encrypt certificate key alias in the keystore
server.port	Port (secure SSL/TLS) on which your application is deployed
lets-encrypt-helper.domain	Your applications' domain (i.e. example.com)
lets-encrypt-helper.contact	The contact of person responsible for the domain (i.e. mailto:john@example.com)
lets-encrypt-helper.account-key-alias	Account key alias	letsencrypt-user
lets-encrypt-helper.letsencrypt-server	Let's Encrypt server to use	acme://letsencrypt.org
lets-encrypt-helper.key-size	Certificate and Account key RSA key size	2048
lets-encrypt-helper.update-before-expiry	Start trying to update certificate this time before expiration	P30D (30 days)
lets-encrypt-helper.busy-wait-interval	Busy wait interval for thread that checks if the certificate is valid	PT1M (1 minute)
lets-encrypt-helper.account-cert-validity	Validity duration for Account key	P3650D (3650 days)
lets-encrypt-helper.store-cert-chain	Store entire trust chain or only domain certificate (for browsers domain ceritificate is enough)	true
lets-encrypt-helper.enabled	Is the helper enabled	true
lets-encrypt-helper.return-null-model	If challenge endpoint should return null model (i.e. true is sane default for cases with Thymeleaf rendering the page)	true
lets-encrypt-helper.development-only.http01-challenge-port	For development only, port for HTTP-01 ACME challenge	80

Example configuration

Launch your application with -Dspring.profiles.active=ssl

application-ssl.yaml:

server:
  port: 443
  ssl:
    key-store: file:/home/user/letsencrypt/application-keystore # Path to KeyStore with certificates and keys
    key-store-password: change-me # Password for KeyStore protection
    key-store-type: PKCS12
    key-alias: tomcat # Certificate name in KeyStore
    enabled: true # Important to place this explicitly
lets-encrypt-helper:
  domain: my-domain.example.com # Domain to issue certificate for
  contact: mailto:john.doe@mymail.example.com # Your contact for Let's Encrypt

Note: On your server ensure you have opened port 80 for Java (i.e. in Firewall) and Java can bind to it (i.e. follow Linux allow listening to low port without sudo to open ports 80,443 for java)

Example project with SSL and Let's Encrypt management using this library is located here

Alternative

The library is itself just 1 Java class. You can add library dependencies and:

• For Tomcat this java file to your configuration
• For Jetty this java file to your configuration

Testing locally

The library has integration tests in:

• tomcat/src/test/java
• jetty/src/test/java

directories. One can adapt these tests according to own needs, as they use Pebble - LetsEncrypt testing server.