lpSecurityDescriptor

lpSecurityDescriptor is a Windows API parameter that provides a pointer to a SECURITY_DESCRIPTOR structure. A security descriptor defines the security attributes of a securable object, including its owner, primary group, a discretionary access control list (DACL), and a system access control list (SACL). The DACL governs access permissions granted or denied to users or groups, while the SACL governs auditing.

Security descriptors can be in absolute or self-relative format. Many APIs expect a self-relative descriptor, which is self-contained and suitable for transfer between processes, while others may work with absolute forms. Builders typically use functions such as InitializeSecurityDescriptor, SetSecurityDescriptorOwner, SetSecurityDescriptorGroup, SetSecurityDescriptorDacl, and SetSecurityDescriptorSacl to populate the descriptor before passing it via lpSecurityDescriptor. Some functions return a security descriptor to the caller, while others consume one supplied by the caller; the exact behavior depends on the function and the SECURITY_INFORMATION flags provided.

Memory management is an important consideration. When an API allocates and returns a SECURITY_DESCRIPTOR, the caller is responsible for freeing it, commonly with LocalFree. If the caller supplies a security descriptor from its own buffer, the descriptor must remain valid for the duration of the API call.

Notes on usage guidelines: passing NULL for lpSecurityDescriptor may indicate that the current object security should be used or that defaults apply, depending on the function. Always consult the specific API documentation to understand whether the parameter is input, output, or both, and whether a self-relative or absolute descriptor is required. lpSecurityDescriptor plays a central role in configuring and inspecting the security posture of Windows objects.