Configuring Spring Oauth2 with JWT & asymmetric RSA keypair

Step 1: Generate RSA key pair.

Here are the steps I took to create my RSA key pairs with Java keytoolcommand. Although I did this to configure my spring oauth2 jwt application, of course, it is not only restricted to that.

1. Lets create our java keystore(.jks) file:
   $ keytool -genkeypair -alias mytestkey -keyalg RSA \
-dname "CN=Web Server,OU=Unit,O=Organization,L=City,S=State,C=US" \
-keypass changeme -keystore server.jks -storepass letmein
   We generated a keypair named mytestkey with an RSA algorithm. Option -keypass changeme is to access the specific keypair, which is mytestkey in our case & -storepass letmein is to access the whole keystore file.

2. Export public key certificate file.
   $ keytool -export -keystore server.jks -alias mytestkey -file example.cer
   With this certificate file we can find get our public key in the next section.

3. Using openssl to print the public key.
   openssl x509 -inform der -in example.cer -pubkey -noout
   This command will show the public key:
   -----BEGIN PUBLIC KEY-----
MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA3Kd1vQNTLHLVhyMR0JHj
Q3CxJ9Roi6aZTzUk/HDerxJ+1ey8CdX4zf8bFA9Fh21KTojw87yt76A6GpCuru6P
zxCou0GLPwFwKCS1SFcsysOMSxRAhgIssjujGnbC2Q0XPDpsGYJVavnHGZ7cI7Hn
sXqHcL0dmbgEfI7NR7wCGHoo1NxjfwOQXtCGH3w/Tg2BLA3HNyRclrCfJuS3aj0y
tr7tOWdzgguztH6E4xoqKdn7FEMMtBEsggw7Z4H8uziUy37Z7iOMTdmwZvbpMrns
IUZElqnYcRFYLPRH5xsSl1Y129fAbW03WW63agzy9DWO5HhT44ePJDrkZqsEaHKw
/QIDAQAB
-----END PUBLIC KEY-----
   Another way to achieve this using java code, which is bit more complex, is:

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KeyPair keyPair = newKeyStoreKeyFactory(

    newClassPathResource("server.jks"),"letmein".toCharArray())

    .getKeyPair("mytestkey","changeme".toCharArray());

System.out.println(newString(Base64.encode(keyPair.getPublic().getEncoded())));

This code was inspired by spring oauth2s JwtAccessTokenConverter.

Step 2: Configure Spring Oauth2

1. Authorization server:.

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@Configuration

@EnableAuthorizationServer

protectedstatic class OAuth2Config extendsAuthorizationServerConfigurerAdapter {

//other configurations are omitted.

@Bean

publicJwtAccessTokenConverter jwtAccessTokenConverter() {

    JwtAccessTokenConverter converter = newJwtAccessTokenConverter();

    KeyPair keyPair = newKeyStoreKeyFactory(

           newClassPathResource("server.jks"),"letmein".toCharArray())

        .getKeyPair("mytestkey","changeme".toCharArray());

    converter.setKeyPair(keyPair);

    returnconverter;

}

 

}

1. Resource Server:
   In your application.yml file(note that spacing is messed up below, you should have a proper spacing):

spring:
  oauth2:
    resource:
      jwt:
        keyValue: |
          —–BEGIN PUBLIC KEY—–
          MIIBIjANBgkqhkiG9…
          —–END PUBLIC KEY—–