The LSAPR_SR_SECURITY_DESCRIPTOR structure is used to communicate a self-relative security descriptor, as specified in [MS-DTYP] section 2.4.6.

   [range(0, 262144)] unsigned long Length;
   [size_is(Length)] unsigned char* SecurityDescriptor;

Length: The count of bytes in SecurityDescriptor.<15>

SecurityDescriptor: The contiguous buffer containing the self-relative security descriptor. This field MUST contain the Length number of bytes. If the Length field has a value other than 0, this field MUST NOT be NULL.