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RtlQueryRegistryValues function (wdm.h)

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The RtlQueryRegistryValues routine allows the caller to query several values from the registry subtree with a single call.

Syntax

NTSYSAPI NTSTATUS RtlQueryRegistryValues(
  [in]           ULONG                     RelativeTo,
  [in]           PCWSTR                    Path,
  [in, out]      PRTL_QUERY_REGISTRY_TABLE QueryTable,
  [in, optional] PVOID                     Context,
  [in, optional] PVOID                     Environment
);

Parameters

[in] RelativeTo

Specifies whether Path is an absolute registry path or is relative to a predefined path as one of the following.

Value Meaning
RTL_REGISTRY_ABSOLUTE Path is an absolute registry path.
RTL_REGISTRY_CONTROL Path is relative to \Registry\Machine\System\CurrentControlSet\Control.
RTL_REGISTRY_DEVICEMAP Path is relative to \Registry\Machine\Hardware\DeviceMap.
RTL_REGISTRY_SERVICES Path is relative to \Registry\Machine\System\CurrentControlSet\Services.
RTL_REGISTRY_USER Path is relative to \Registry\User\CurrentUser. (For a system process, this is \User\.Default.)
RTL_REGISTRY_WINDOWS_NT Path is relative to \Registry\Machine\Software\Microsoft\Windows NT\CurrentVersion.

The RelativeTo value can be modified by bitwise-ORing it with one of the following flags.

Flag Meaning
RTL_REGISTRY_OPTIONAL Specifies that the key referenced by this parameter and the Path parameter are optional.
RTL_REGISTRY_HANDLE Specifies that the Path parameter is actually a registry handle to use.

[in] Path

Pointer to either an absolute registry path or a path relative to the known location specified by the RelativeTo parameter. Note that the names of keys in such a path must be known to the caller, including the last key in the path. If the RTL_REGISTRY_HANDLE flag is specified, this parameter is a registry handle for an already opened key to be queried directly.

[in, out] QueryTable

Pointer to a table of one or more value names and subkey names in which the caller is interested. Each table entry contains the address of a caller-supplied QueryRoutine function that will be called for each value name that exists in the registry. The table must be terminated with a NULL table entry, which is a table entry with a NULL QueryRoutine member and a NULL Name member. The structure for query table entries is defined as follows:

typedef struct _RTL_QUERY_REGISTRY_TABLE {
    PRTL_QUERY_REGISTRY_ROUTINE QueryRoutine;
    ULONG Flags;
    PWSTR Name;
    PVOID EntryContext;
    ULONG DefaultType;
    PVOID DefaultData;
    ULONG DefaultLength;
} RTL_QUERY_REGISTRY_TABLE, *PRTL_QUERY_REGISTRY_TABLE;

If the caller allocates storage for the query table pointed to by the QueryTable parameter, the caller is responsible for releasing this storage after the RtlQueryRegistryValues call returns.

QueryRoutine

The address of a QueryRoutine function that is called with the name, type, data, and data length of a registry value. If this member and the Name member are both NULL, it marks the end of the table.

A QueryRoutine function is declared as follows:

NTSTATUS
QueryRoutine (
    IN PWSTR ValueName,
    IN ULONG ValueType,
    IN PVOID ValueData,
    IN ULONG ValueLength,
    IN PVOID Context,
    IN PVOID EntryContext
    );

For more information, see QueryRoutine.

Flags

Flags to control how the remaining members of the RTL_QUERY_REGISTRY_TABLE structure are to be interpreted. The following flag bits are defined for this member.

Value Meaning
RTL_QUERY_REGISTRY_SUBKEY The Name of this table entry is another path to a registry key, and all following table entries are for that key rather than the key specified by the Path parameter. This change in focus lasts until the end of the table or until another RTL_REGISTRY_SUBKEY or RTL_QUERY_REGISTRY_TOPKEY entry is seen. Each such entry must specify a path that is relative to the Path specified in the call to RtlQueryRegistryValues.
RTL_QUERY_REGISTRY_TOPKEY Resets the current registry key handle to the original one specified by the RelativeTo and Path parameters. This is useful for getting back to the original node after descending into subkeys with the RTL_QUERY_REGISTRY_SUBKEY flag.
RTL_QUERY_REGISTRY_REQUIRED Specifies that this registry value must exist if DefaultType = REG_NONE; otherwise, if it is not found, RtlQueryRegistryValues immediately exits with a status code of STATUS_OBJECT_NAME_NOT_FOUND. This exit occurs if the Name member is NULL and the current key has no subkeys, or if Name specifies a nonexistent subkey. (If this flag is not specified, then when no match is found for a non-NULL Name, the routine uses the DefaultValue member as the value. When Name is NULL and the current key has no subkeys, the routine simply skips that table entry.)
RTL_QUERY_REGISTRY_NOVALUE Specifies that even though there is no Name for this table entry, all the caller wants is a callback: that is, the caller does not want to enumerate all the values under the current key. QueryRoutine is called with NULL for ValueData, REG_NONE for ValueType, and zero for ValueLength.
RTL_QUERY_REGISTRY_NOEXPAND For a registry value of type REG_EXPAND_SZ or REG_MULTI_SZ, this flag overrides the default behavior, which is to preprocess the registry value before calling the QueryRoutine routine. By default, RtlQueryRegistryValues expands environment variable references in REG_EXPAND_SZ values, and enumerates each null-terminated string in a REG_MULTI_SZ value in a separate QueryRoutine call, so that the strings are presented as REG_SZ values that have the same ValueName. If this flag is set, QueryRoutine receives the raw REG_EXPAND_SZ or REG_MULTI_SZ value from the registry. For more information about the data formats for these values, see KEY_VALUE_BASIC_INFORMATION.
RTL_QUERY_REGISTRY_DIRECT The QueryRoutine member is not used (and must be NULL), and the EntryContext points to the buffer to store the value. If the caller sets this flag, the caller should additionally set the RTL_QUERY_REGISTRY_TYPECHECK flag to guard against buffer overflow. For more information, see the Remarks section.
RTL_QUERY_REGISTRY_TYPECHECK Use this flag with the RTL_QUERY_REGISTRY_DIRECT flag to verify that the REG_XXX type of the stored registry value matches the type expected by the caller. If the types do not match, the call fails. For more information, see the Remarks section.
RTL_QUERY_REGISTRY_DELETE This flag is used to delete value keys after they have been queried.

Starting with Windows 2000, inbox support is provided for all flag bits in the preceding table, with the exception of RTL_QUERY_REGISTRY_TYPECHECK. Inbox support for RTL_QUERY_REGISTRY_TYPECHECK is available starting with Windows 8. For earlier versions of Windows, support for RTL_QUERY_REGISTRY_TYPECHECK is provided through Windows Update. For more information, see Remarks.

Name

This is the name of a Value that the caller queried. If Name is NULL, the QueryRoutine function specified for this table entry is called for all values associated with the current registry key. If the RTL_QUERY_REGISTRY_DIRECT flag is set, a non-NULL value for Name must be provided.

EntryContext

If the RTL_QUERY_REGISTRY_DIRECT flag is set, this is a pointer to the buffer to store the result of the query operation for this key. Otherwise, this value is passed as the EntryContext parameter of QueryRoutine.

DefaultType

The least significant byte of this member specifies the REG_XXX type of the data to be returned, if no matching key is found and the RTL_QUERY_REGISTRY_REQUIRED flag is not specified. Specify REG_NONE for no default type. If the RTL_QUERY_REGISTRY_TYPECHECK flag is set, the most significant byte of this member specifies the REG_XXX type of the stored registry value that the caller expects. Bits 8 to 23 of this member are reserved and should be zero.

DefaultData

A pointer to the default value to be returned if no matching key is found and the RTL_QUERY_REGISTRY_REQUIRED flag is not specified. This member is ignored if DefaultType = REG_NONE. Otherwise, the type of data pointed to by DefaultData should conform to the registry value type specified by the DefaultType member. For more information registry value types, see the definition of the Type parameter in KEY_VALUE_BASIC_INFORMATION.

DefaultLength

Specifies the length, in bytes, of the DefaultData member. If DefaultType is REG_SZ, REG_EXPAND_SZ, or REG_MULTI_SZ, callers can optionally specify zero to indicate RtlQueryRegistryValues should compute the length based on the default data value. If DefaultType = REG_NONE, this member is ignored.

[in, optional] Context

Specifies the value passed as the Context parameter of a QueryRoutine function each time it is called.

[in, optional] Environment

Pointer to the environment used when expanding variable values in REG_EXPAND_SZ registry values, or a NULL pointer (optional).

Return value

RtlQueryRegistryValues returns an NTSTATUS code. The possible return values include:

Return code Description
STATUS_SUCCESS The entire query table was processed successfully.
STATUS_INVALID_PARAMETER Processing of the query table terminated with an invalid table entry. A table entry can be invalid if the specified flags require the QueryRoutine or Name member to be non-NULL, but a NULL value was provided.
STATUS_OBJECT_NAME_NOT_FOUND The Path parameter does not match a valid key, or processing of the query table terminated with an entry with the RTL_QUERY_REGISTRY_REQUIRED flag set and no matching key is found. This occurs if the Name member is NULL and the current key has no subkeys, or if Name specifies a nonexistent subkey.
STATUS_BUFFER_TOO_SMALL The RTL_QUERY_REGISTRY_DIRECT flag is set, and the buffer specified by EntryContext is too small to hold the key value data.
STATUS_OBJECT_TYPE_MISMATCH The RTL_QUERY_REGISTRY_TYPECHECK flag is set and the type of the stored registry value does not match the type expected by the caller.

RtlQueryRegistryValues also terminates processing of the table if the QueryRoutine function for a table entry returns an NTSTATUS error code, and returns that error code as its result. (With one exception: If QueryRoutine returns STATUS_BUFFER_TOO_SMALL, the error code is ignored.)

Remarks

The caller specifies an initial key path and a table. The table contains one or more entries that describe the key values and subkey names in which the caller is interested. The table is terminated by an entry with a NULL QueryRoutine member and a NULL Name member. The table must be allocated from nonpaged pool.

Kernel-mode drivers must specify the RTL_QUERY_REGISTRY_NOEXPAND flag to prevent calling environment variable routines. These routines are unsafe, so kernel-mode drivers should not use them.

Caution

If you use the RTL_QUERY_REGISTRY_DIRECT flag, an untrusted user-mode application may be able to cause a buffer overflow. A buffer overflow can occur if a driver uses this flag to read a registry value to which the wrong type is assigned. In all cases, a driver that uses the RTL_QUERY_REGISTRY_DIRECT flag should additionally use the RTL_QUERY_REGISTRY_TYPECHECK flag to prevent such overflows.

If the RTL_QUERY_REGISTRY_TYPECHECK flag is set in a table entry, the caller must specify the expected REG_XXX type in the 8 most significant bits (MSBs) of the 32-bit DefaultType member of the table entry. As shown in the following code example, the RTL_QUERY_REGISTRY_TYPECHECK_SHIFT constant, which is defined to be 24, can be used as the shift count required to place the expected REG_XXX type in the 8 MSBs of the DefaultType member.

RTL_QUERY_REGISTRY_TABLE QueryRegTable[2];    
...
QueryRegTable[0].DefaultType = (REG_SZ << RTL_QUERY_REGISTRY_TYPECHECK_SHIFT) | REG_NONE;
...
QueryRegTable[1].DefaultType = (REG_DWORD << RTL_QUERY_REGISTRY_TYPECHECK_SHIFT) | REG_NONE;
...

Starting with Windows 8, if an RtlQueryRegistryValues call accesses an untrusted hive, and the caller sets the RTL_QUERY_REGISTRY_DIRECT flag for this call, the caller must additionally set the RTL_QUERY_REGISTRY_TYPECHECK flag. A violation of this rule by a call from user mode causes an exception. A violation of this rule by a call from kernel mode causes a 0x139 bug check (KERNEL_SECURITY_CHECK_FAILURE).

Only system hives are trusted. An RtlQueryRegistryValues call that accesses a system hive does not cause an exception or a bug check if the RTL_QUERY_REGISTRY_DIRECT flag is set and the RTL_QUERY_REGISTRY_TYPECHECK flag is not set. However, as a best practice, the RTL_QUERY_REGISTRY_TYPECHECK flag should always be set if the RTL_QUERY_REGISTRY_DIRECT flag is set.

Similarly, in versions of Windows before Windows 8, as a best practice, an RtlQueryRegistryValues call that sets the RTL_QUERY_REGISTRY_DIRECT flag should additionally set the RTL_QUERY_REGISTRY_TYPECHECK flag. However, failure to follow this recommendation does not cause an exception or a bug check.

The following is a list of system hives:

  • \REGISTRY\MACHINE\HARDWARE

  • \REGISTRY\MACHINE\SOFTWARE

  • \REGISTRY\MACHINE\SYSTEM

  • \REGISTRY\MACHINE\SECURITY

  • \REGISTRY\MACHINE\SAM

Support for the RTL_QUERY_REGISTRY_TYPECHECK flag is available through Windows Update for Windows 7, Windows Vista, Windows Server 2003, and Windows XP. For more information about this update, see Vulnerabilities in Windows Kernel Could Allow Elevation of Privilege (2393802). In versions of these operating systems that do not have this update, the caller can use the RTL_QUERY_REGISTRY_TYPECHECK flag. However, this flag is ignored by the RtlQueryRegistryValues routine.

Starting with Windows Driver Kit (WDK) 8, the RTL_QUERY_REGISTRY_TYPECHECK flag is defined in the Wdm.h header file as follows:

#define RTL_QUERY_REGISTRY_TYPECHECK 0x00000100

If an entry does not specify the RTL_QUERY_REGISTRY_DIRECT flag, RtlQueryRegistryValues uses the specified QueryRoutine function to report the value name, type, data, and data length, in bytes, to the caller. If the Name member of the entry is NULL, RtlQueryRegistryValues reports every direct subkey of the key. If the key type is REG_MULTI_SZ and the RTL_QUERY_REGISTRY_NOEXPAND flag not is specified, the routine calls QueryRoutine separately for each individual string; otherwise the routine reports it as a single value. If an entry specifies the RTL_QUERY_REGISTRY_DIRECT flag, RtlQueryRegistryValues stores the value of the key in the buffer pointed to by the entry's EntryContext member. The format of the returned data is as follows.

Key data type How data is returned
A null-terminated Unicode string (such as REG_SZ, REG_EXPAND_SZ). EntryContext must point to an initialized UNICODE_STRING structure. If the Buffer member of UNICODE_STRING is NULL, the routine allocates storage for the string data. Otherwise, it stores the string data in the buffer that Buffer points to.
REG_MULTI_SZ You must specify the RTL_QUERY_REGISTRY_NOEXPAND flag for this key data type. EntryContext points to an initialized UNICODE_STRING structure. The routine stores the key value as a single string value. Each individual component within the string is terminated by a zero. If the Buffer member of UNICODE_STRING is NULL, the routine allocates storage for the string data. Otherwise, it stores the string data in the buffer that Buffer points to.
Nonstring data with size, in bytes, <= sizeof(ULONG) The value is stored in the memory location specified by EntryContext.
Nonstring data with size, in bytes, > sizeof(ULONG) The buffer pointed to by EntryContext must begin with a signed LONG value. The magnitude of the value must specify the size, in bytes, of the buffer. If the sign of the value is negative, RtlQueryRegistryValues will only store the data of the key value. Otherwise, it will use the first ULONG in the buffer to record the value length, in bytes, the second ULONG to record the value type, and the rest of the buffer to store the value data.

If an error occurs at any stage of processing of the query table, RtlQueryRegistryValues stops processing the table and returns the error status.

See ZwSetValueKey for a description of the possible REG_XXX values.

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

See also

QueryRoutine

RtlZeroMemory

UNICODE_STRING

ZwEnumerateKey

ZwEnumerateValueKey

ZwSetValueKey