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The SAMPR_SR_SECURITY_DESCRIPTOR structure holds a formatted security descriptor.

 typedef struct _SAMPR_SR_SECURITY_DESCRIPTOR {
   [range(0, 256 * 1024)] unsigned long Length;
   [size_is(Length)] unsigned char* SecurityDescriptor;
 } SAMPR_SR_SECURITY_DESCRIPTOR,
  *PSAMPR_SR_SECURITY_DESCRIPTOR;

Length: The size, in bytes, of SecurityDescriptor. If zero, SecurityDescriptor MUST be ignored. The maximum size of 256 * 1024 is an arbitrary value chosen to limit the amount of memory a client can force the server to allocate.

SecurityDescriptor: A binary format per the SECURITY_DESCRIPTOR format in [MS-DTYP] section 2.4.6.