Adding sun.jdk module to Wildfly to resolve "Invalid secret key format" and "Vault Reader Exception"

In Java 8 Update 171 and newer, starting a Wildfly JVM will display the following error messages:

... WFLYCTL0013: Operation ("add") failed ...
... WFLYSRV0076: Error initializing vault ...
... WFLYSRV0227: Vault Reader Exception ...
...
Caused by: java.io.IOException: Invalid secret key format

A sample stack trace can be seen at the bottom of this article. 

This can be worked around by manually adding the sun.jdk module into Wildfly's module.xml:

1. Turn off the Wildfly JVM
2. Go to the following directory:
   

   <install home>\wildfly\modules\system\layers\base\org\picketbox\main\module.xml

3. Find the "dependencies" section (see screenshot below as a reference)
4.  Add the following line to the beginning:
   

   <module name="sun.jdk"/>

5. Turn on the Wildfly JVM

After the change, the error will stop occurring.

Module.xml after the change:

Sample stack trace of the original error:

13:36:42,010 ERROR [org.jboss.as.controller.management-operation] (Controller Boot Thread) WFLYCTL0013: Operation ("add") failed - address: ([("core-service" => "vault")]): java.lang.RuntimeException: WFLYSRV0076: Error initializing vault --  org.jboss.as.server.services.security.VaultReaderException: WFLYSRV0227: Vault Reader Exception:
        at org.jboss.as.server.services.security.VaultAddHandler.performRuntime(VaultAddHandler.java:86)
        at org.jboss.as.controller.AbstractAddStepHandler.performRuntime(AbstractAddStepHandler.java:337)
        at org.jboss.as.controller.AbstractAddStepHandler$1.execute(AbstractAddStepHandler.java:151)
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:890)
        at org.jboss.as.controller.AbstractOperationContext.processStages(AbstractOperationContext.java:659)
        at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:370)
        at org.jboss.as.controller.OperationContextImpl.executeOperation(OperationContextImpl.java:1329)
        at org.jboss.as.controller.ModelControllerImpl.boot(ModelControllerImpl.java:493)
        at org.jboss.as.controller.AbstractControllerService.boot(AbstractControllerService.java:387)
        at org.jboss.as.controller.AbstractControllerService.boot(AbstractControllerService.java:349)
        at org.jboss.as.server.ServerService.boot(ServerService.java:397)
        at org.jboss.as.server.ServerService.boot(ServerService.java:366)
        at org.jboss.as.controller.AbstractControllerService$1.run(AbstractControllerService.java:299)
        at java.lang.Thread.run(Unknown Source)
Caused by: org.jboss.as.server.services.security.VaultReaderException: WFLYSRV0227: Vault Reader Exception:
        at org.jboss.as.server.services.security.RuntimeVaultReader.createVault(RuntimeVaultReader.java:98)
        at org.jboss.as.server.services.security.VaultAddHandler.performRuntime(VaultAddHandler.java:84)
        ... 13 more
Caused by: org.jboss.security.vault.SecurityVaultException: java.lang.RuntimeException: PBOX00140: Unable to get keystore (D:/Infogix/v9.2/Infogix/wildfly/ER/configuration/vault.store)
        at org.picketbox.plugins.vault.PicketBoxSecurityVault.init(PicketBoxSecurityVault.java:210)
        at org.jboss.as.server.services.security.RuntimeVaultReader.createVault(RuntimeVaultReader.java:96)
        ... 14 more
Caused by: java.lang.RuntimeException: PBOX00140: Unable to get keystore (D:/Infogix/v9.2/Infogix/wildfly/ER/configuration/vault.store)
        at org.picketbox.plugins.vault.PicketBoxSecurityVault.getKeyStore(PicketBoxSecurityVault.java:691)
        at org.picketbox.plugins.vault.PicketBoxSecurityVault.init(PicketBoxSecurityVault.java:205)
        ... 15 more
Caused by: java.io.IOException: Invalid secret key format
        at com.sun.crypto.provider.JceKeyStore.engineLoad(JceKeyStore.java:856)
        at java.security.KeyStore.load(Unknown Source)
        at org.picketbox.util.KeyStoreUtil.getKeyStore(KeyStoreUtil.java:201)
        at org.picketbox.util.KeyStoreUtil.getKeyStore(KeyStoreUtil.java:151)
        at org.picketbox.plugins.vault.PicketBoxSecurityVault.getKeyStore(PicketBoxSecurityVault.java:688)
        ... 16 more