NullPointerException happens in JKS keystore if we don't set any password for key entries. This is a regression from task JDK-8208583. Previously, JDK were throwing IllegalArgumentException with proper message during this scenario, after the fix of JDK-8208583, JDK throws NullPointerException.
IllegalArgumentException were throwing from KeyProtector.java by below statement in the constructor "throw new IllegalArgumentException("password can't be null");" But now code flow is got changed by below part of code during the fix of JDK-8208583 :

- keyProtector = new KeyProtector(password);
+ passwordBytes = convertToBytes(password);
+ keyProtector = new KeyProtector(passwordBytes);

Now convertToBytes() is getting invoked before invoking KeyProtector() constructor. The convertToBytes() doesn't check the password is null, directly try to get password.length, that results in NPE.

How to reproduce:
Attached a reproducible test case.
Since pkcs12 is the default key store in JDK 9 and above execute test with "JKS" as parameter in JDK 9 and above.
Eg: java TestKeyStore JKS

Reproducibility in different JDK version:
JDK 15 build 4: Fail
JDK 14 build 30: Fail
JDK12 build 6 : Fail
JDK 12 build 5: Pass
JDK11.0.2 build b02: Fail
JDK11.0.2 build b01: Pass
JDK 8u201 b01: Fail
JDK8u191 - Pass
 
Actual Behaviour : NullPointerException
Exception in thread "main" java.lang.NullPointerException
at java.base/sun.security.provider.JavaKeyStore.convertToBytes(JavaKeyStore.java:827)
at java.base/sun.security.provider.JavaKeyStore.engineSetKeyEntry(JavaKeyStore.java:274)
at java.base/sun.security.util.KeyStoreDelegator.engineSetKeyEntry(KeyStoreDelegator.java:111)
at java.base/java.security.KeyStore.setKeyEntry(KeyStore.java:1167)
at TestKeyStore.main(TestKeyStore.java:45)


Expected Behaviour : java.lang.IllegalArgumentException: password can't be null
Exception in thread "main" java.lang.IllegalArgumentException: password can't be null
at java.base/sun.security.provider.KeyProtector.<init>(KeyProtector.java:136)
at java.base/sun.security.provider.JavaKeyStore.engineSetKeyEntry(JavaKeyStore.java:267)
at java.base/sun.security.util.KeyStoreDelegator.engineSetKeyEntry(KeyStoreDelegator.java:111)
at java.base/java.security.KeyStore.setKeyEntry(KeyStore.java:1174)
at TestKeyStore.main(TestKeyStore.java:45)