Advapi32Util registryKeyExists() and registryValueExists() throws exception on access denied

[Daniel B. Widdis]

This looks like a similar situation to https://github.com/java-native-access/jna/issues/1036

Trying to iterate audio device drivers using this code:

private static final String REGISTRY_SOUNDCARDS = "SYSTEM\\CurrentControlSet\\Control\\Class\\{4d36e96c-e325-11ce-bfc1-08002be10318}\\";

        String[] keys = Advapi32Util.registryGetKeys(WinReg.HKEY_LOCAL_MACHINE, REGISTRY_SOUNDCARDS);
        for (String key : keys) {
            String fullKey = REGISTRY_SOUNDCARDS + key;
            if (Advapi32Util.registryValueExists(WinReg.HKEY_LOCAL_MACHINE, fullKey, "MatchingDeviceId")) {
            String id = Advapi32Util.registryGetStringValue(WinReg.HKEY_LOCAL_MACHINE, REGISTRY_SOUNDCARDS + key,
                    "MatchingDeviceId");
                System.out.println("Key: " + key + ", id:" + id);
            }
        }

A Win32 Exception "Access is Denied" is thrown on the registryValueExists() check.

Exception in thread "main" com.sun.jna.platform.win32.Win32Exception: Access is denied.
    at com.sun.jna.platform.win32.Advapi32Util.registryKeyExists(Advapi32Util.java:595)
    at com.sun.jna.platform.win32.Advapi32Util.registryKeyExists(Advapi32Util.java:569)

Unlike the other issue, checking for existence of they key first doesn't work, and throws the same exception:

Advapi32Util.registryKeyExists(WinReg.HKEY_LOCAL_MACHINE, fullKey)

The offending key is:

HKLM\SYSTEM\CurrentControlSet\Control\Class\{4d36e96c-e325-11ce-bfc1-08002be10318}\Properties

I don't see any way to check for access using Advapi32Util, so my only fallback is to catch this exception.  Should this just result in a "false" like the earlier issue?

--

Dan Widdis

[Amritanshu]

>  Should this just result in a "false" like the earlier issue?  

No, because the caller of the function doesn't have sufficient privileges to tell if the key exists or not so it shouldn't return false. I think throwing the exception is correct and expected.   

[Daniel D.]

This is indeed by design, and different than #1036 which was a bug in which a key that didn't exist resulted in an invalid handle exception from some cleanup.

On Tue, Feb 5, 2019 at 3:55 PM Amritanshu <amrit...@gmail.com> wrote:

>  Should this just result in a "false" like the earlier issue?  

No, because the caller of the function doesn't have sufficient privileges to tell if the key exists or not so it shouldn't return false. I think throwing the exception is correct and expected.   

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