Secret Keys

Secret Keys Expressions

In SmallRye Config, a secret configuration may be expressed as ${handler::value}, where the handler is the name of a io.smallrye.config.SecretKeysHandler to decode or decrypt the value separated by a double colon ::.

It is possible to create a custom SecretKeysHandler and provide different ways to decode or decrypt configuration values.

A custom SecretKeysHandler requires an implementation of io.smallrye.config.SecretKeysHandler or io.smallrye.config.SecretKeysHandlerFactory. Each implementation requires registration via the ServiceLoader mechanism, either in META-INF/services/io.smallrye.config.SecretKeysHandler or META-INF/services/io.smallrye.config.SecretKeysHandlerFactory files.

Danger

It is not possible to mix Secret Keys Expressions with Property Expressions.

Crypto

The smallrye-config-crypto artifact contains a few out-of-the-box SecretKeysHandlers ready for use. It requires the following dependency:

<dependency>
    <groupId>io.smallrye.config</groupId>
    <artifactId>smallrye-config-crypto</artifactId>
    <version>3.17.3-SNAPSHOT</version>
</dependency>

AES/GCM/NoPadding ${aes-gcm-nopadding::...}

• The encoding length is 128.
• The secret and the encryption key (without padding) must be base 64 encoded.

Example

application.properties

smallrye.config.secret-handler.aes-gcm-nopadding.encryption-key=DDne5obnfH1RSeTg71xSZg

my.secret=${aes-gcm-nopadding::DLTb_9zxThxeT5iAQqswEl5Dn1ju4FdM9hIyVip35t5V}

The ${aes-gcm-nopadding::...} SecretKeyHandler requires smallrye.config.secret-handler.aes-gcm-nopadding.encryption-key configuration to state the encryption key to be used by the aes-gcm-nopaddin handler.

A lookup to my.secret will use the SecretKeysHandler name aes-gcm-nopadding to decode the value DJNrZ6LfpupFv6QbXyXhvzD8eVDnDa_kTliQBpuzTobDZxlg.

Info

It is possible to generate the encrypted secret with the following JBang script:

jbang https://raw.githubusercontent.com/smallrye/smallrye-config/main/documentation/src/main/docs/config/secret-handlers/encryptor.java -s=<secret> -k=<encryptionKey>`

Configuration

Configuration Property	Type	Default
smallrye.config.secret-handler.aes-gcm-nopadding.encryption-key The encryption key to use to decode secrets encoded by the AES/GCM/NoPadding algorithm.	String
"smallrye.config.secret-handler.aes-gcm-nopadding.encryption-key-decode" Decode the encryption key in Base64, if the plain text key was used to encrypt the secret.	boolean	false

Secret Keys Names

When configuration properties contain passwords or other kinds of secrets, Smallrye Config can hide them to prevent accidental exposure of such values.

This is no way a replacement for securing secrets. Proper security mechanisms must still be used to secure secrets. However, there is still the fundamental problem that passwords and secrets are generally encoded simply as strings. Secret Keys provides a way to “lock” the configuration so that secrets do not appear unless explicitly enabled.

To mark specific keys as secrets, register an instance of io.smallrye.config.SecretKeysConfigSourceInterceptor by using the interceptor factory as follows:

public class SecretKeysConfigInterceptorFactory implements ConfigSourceInterceptorFactory {
    @Override
    public ConfigSourceInterceptor getInterceptor(ConfigSourceInterceptorContext context) {
        return new SecretKeysConfigSourceInterceptor(Set.of("secret"));
    }
}

Register the factory so that it can be found at runtime by creating a META-INF/services/io.smallrye.config.ConfigSourceInterceptorFactory file that contains the fully qualified name of this factory class.

From this point forward, every lookup to the configuration name secret will throw a SecurityException.

Access the Secret Keys using the APIs io.smallrye.config.SecretKeys#doUnlocked(java.lang.Runnable) and io.smallrye.config.SecretKeys#doUnlocked(java.util.function.Supplier<T>).

String secretValue = SecretKeys.doUnlocked(() -> {
    config.getValue("secret", String.class);
});

Secret Keys are only unlocked in the context of doUnlocked. Once the execution completes, the secrets become locked again.