RFR: 8284910: Buffer clean in PasswordCallback [v2]

[Roger Riggs]

On Mon, 18 Apr 2022 17:27:04 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>> src/java.base/share/classes/javax/security/auth/callback/PasswordCallback.java line 123:
>> 
>>> 121:             cleanable = CleanerFactory.cleaner().register(
>>> 122:                     this, cleanerFor(inputPassword));
>>> 123:         }
>> 
>> If `setPassword` is called twice in succession, should the previous password be cleaned before the new one is assigned and registered?
>
> I can see why that might be a good idea. Would require a specification change though. I also think it is fine to keep the behavior the same, and place the responsibility on the application to call `clearPassword` before setting a new one. We could add a warning though, something like: "Note: `clearPassword` should be called to clear any prior password before calling `setPassword` multiple times on the same `PasswordCallback` instance."

setPassword can/should always clear the previous password.  It is an internal copy that no one else has a reference to and is being replaced.
It will need to either explicitly call cleanable.clean() or fill/erase the array itself.
Overwriting the cleanable will prevent the existing cleanable from being processed.
It don't think it needs a spec change, the internal value is implementation only.

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PR: https://git.openjdk.java.net/jdk/pull/8272