ZwQueryKey function (wdm.h)
The ZwQueryKey routine provides information about the class of a registry key, and the number and sizes of its subkeys.
Syntax
NTSYSAPI NTSTATUS ZwQueryKey(
[in] HANDLE KeyHandle,
[in] KEY_INFORMATION_CLASS KeyInformationClass,
[out, optional] PVOID KeyInformation,
[in] ULONG Length,
[out] PULONG ResultLength
);
Parameters
[in] KeyHandle
Handle to the registry key to obtain information about. This handle is created by a successful call to ZwCreateKey or ZwOpenKey.
[in] KeyInformationClass
Specifies a KEY_INFORMATION_CLASS value that determines the type of information returned in the KeyInformation buffer.
[out, optional] KeyInformation
Pointer to a caller-allocated buffer that receives the requested information.
[in] Length
Specifies the size, in bytes, of the KeyInformation buffer.
[out] ResultLength
Pointer to a variable that receives the size, in bytes, of the requested key information. If ZwQueryKey returns STATUS_SUCCESS, the variable contains the amount of data returned. If ZwQueryKey returns STATUS_BUFFER_OVERFLOW or STATUS_BUFFER_TOO_SMALL, you can use the value of the variable to determine the required buffer size.
Return value
ZwQueryKey returns STATUS_SUCCESS on success, or the appropriate error code on failure. Possible error code values include:
| Return code | Description |
|---|---|
| STATUS_BUFFER_OVERFLOW | The buffer supplied is too small, and only partial data has been written to the buffer. *ResultLength is set to the minimum size required to hold the requested information. |
| STATUS_BUFFER_TOO_SMALL | The buffer supplied is too small, and no data has been written to the buffer. *ResultLength is set to the minimum size required to hold the requested information. |
| STATUS_INVALID_PARAMETER | The KeyInformationClass parameter is not a valid KEY_INFORMATION_CLASS value. |
Remarks
The KeyHandle passed to ZwQueryKey must have been opened with KEY_QUERY_VALUE access. This is accomplished by passing KEY_QUERY_VALUE, KEY_READ, or KEY_ALL_ACCESS as the DesiredAccess parameter to ZwCreateKey or ZwOpenKey.
If KeyInformationClass is KeyNameInformation or KeyHandleTagsInformation, the KEY_QUERY_VALUE requirement does not apply.
ZwQueryKey can be used to obtain information that you can use to allocate buffers to hold registry data, such as the maximum size of a key's value entries or subkey names, or the number of subkeys. For example, you can call ZwQueryKey, use the returned information to allocate a buffer for a subkey, call ZwEnumerateKey to get the name of the subkey, and pass that name to an RtlXxxRegistry routine.
For more information about working with registry keys, see Using the Registry in a Driver.
If the call to this function occurs in user mode, you should use the name "NtQueryKey" instead of "ZwQueryKey".
For calls from kernel-mode drivers, the NtXxx and ZwXxx versions of a Windows Native System Services routine can behave differently in the way that they handle and interpret input parameters. For more information about the relationship between the NtXxx and ZwXxx versions of a routine, see Using Nt and Zw Versions of the Native System Services Routines.
Requirements
| Requirement | Value |
|---|---|
| Target Platform | Universal |
| Header | wdm.h (include Wdm.h, Ntddk.h, Ntifs.h) |
| Library | NtosKrnl.lib |
| DLL | NtosKrnl.exe |
| IRQL | PASSIVE_LEVEL |
| DDI compliance rules | HwStorPortProhibitedDDIs(storport), IrqlZwPassive(wdm), PowerIrpDDis(wdm), ZwRegistryCreate(storport), ZwRegistryCreate(storport), ZwRegistryCreate(wdm), ZwRegistryOpen(storport), ZwRegistryOpen(storport), ZwRegistryOpen(wdm) |
See also
KEY_VIRTUALIZATION_INFORMATION
Using Nt and Zw Versions of the Native System Services Routines