FltQuerySecurityObject function (fltkernel.h)

Article
10/21/2021

FltQuerySecurityObject retrieves a copy of an object's security descriptor.

Syntax

NTSTATUS FLTAPI FltQuerySecurityObject(
  [in]            PFLT_INSTANCE        Instance,
  [in]            PFILE_OBJECT         FileObject,
  [in]            SECURITY_INFORMATION SecurityInformation,
  [in, out]       PSECURITY_DESCRIPTOR SecurityDescriptor,
  [in]            ULONG                Length,
  [out, optional] PULONG               LengthNeeded
);

Parameters

[in] Instance

Opaque instance pointer for the caller. This parameter is required and cannot be NULL.

[in] FileObject

File object pointer for the object whose security descriptor is being queried. This parameter is required and cannot be NULL.

[in] SecurityInformation

SECURITY_INFORMATION value. This parameter is required and must be one of the following:

SecurityInformation Value	Meaning
OWNER_SECURITY_INFORMATION	The owner identifier of the object is being queried. Requires READ_CONTROL access.
GROUP_SECURITY_INFORMATION	The primary group identifier of the object is being queried. Requires READ_CONTROL access.
DACL_SECURITY_INFORMATION	The discretionary access control list (DACL) of the object is being queried. Requires READ_CONTROL access.
SACL_SECURITY_INFORMATION	The system ACL (SACL) of the object is being queried. Requires ACCESS_SYSTEM_SECURITY access.

[in, out] SecurityDescriptor

Pointer to a caller-supplied output buffer that receives a copy of the security descriptor for the specified object. The SECURITY_DESCRIPTOR structure is returned in self-relative format. This parameter is optional and can be NULL.

[in] Length

Size, in bytes, of the SecurityDescriptor buffer.

[out, optional] LengthNeeded

Pointer to a caller-allocated variable that receives the number of bytes required to store the copied security descriptor returned in the buffer pointed to by the SecurityDescriptor parameter. This parameter is optional and can be NULL.

Return value

FltQuerySecurityObject returns STATUS_SUCCESS or an appropriate NTSTATUS value such as one of the following:

Return code	Description
STATUS_ACCESS_DENIED	The caller did not have the required access. This is an error code.
STATUS_BUFFER_TOO_SMALL	The buffer is too small to contain the security descriptor. None of the security information was copied to the buffer. This is an error code.

Remarks

A security descriptor can be in absolute or self-relative form. In self-relative form, all members of the structure are located contiguously in memory. In absolute form, the structure contains only pointers to its members.

The NTFS file system imposes a 64-KB limit on the size of the security descriptor that is written to disk for a file. (The FAT file system does not support security descriptors for files.) Thus, a 64-KB buffer pointed to by the SecurityDescriptor parameter is guaranteed to be large enough to hold the returned SECURITY_DESCRIPTOR structure.

The object that the FileObject parameter points to can represent a named data stream. For more information about named data streams, see FILE_STREAM_INFORMATION.

For more information about security and access control, see the Microsoft Windows SDK documentation.

Requirements

Requirement	Value
Target Platform	Universal
Header	fltkernel.h (include Fltkernel.h)
Library	FltMgr.lib
DLL	Fltmgr.sys
IRQL	PASSIVE_LEVEL