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Authorization

ACLs

  • Every object has a "security descriptor" in the NTSecurityDescriptor property, which is used to check if a user/object has access to that object.

  • A Security Descriptor contains the following Property:

    • Owner SID: Object Owner

    • Group SID: Owner's Primary Group

    • DACL: Discretionary Access Control List - Contains ACEs

    • SACL: System Access Control List

Owner  : DOCTOR\Domain Admins
Group  : DOCTOR\Domain Admins
Access : {System.DirectoryServices.ActiveDirectoryAccessRule,                                                 System.DirectoryServices.ActiveDirectoryAccessRule,                                                            System.DirectoryServices.ActiveDirectoryAccessRule,                                                            System.DirectoryServices.ActiveDirectoryAccessRule...}
audit  :

DACL

Contains ACE that determines the user/group that can can access the object.

ACE in DACL

Defines access permission on a object for a specific user or group. An ACE contains the following basic property:

  • AccessControlType: Specify if the ACE is for Allowing or Denying access

  • IsInherited: Specify if the ACE is inherited or not (True/False)

  • InheritenceType: The type of object class that can inherit the ACE from this object.

  • ActiveDirectoryRights: Indicates the type of access the ACE is applying.

  • IdentityReference: The principal (User/Group) for which the ACE is applied.

  • ObjectType: GUID that indicates an extended right, property, or child object depending on the Access Mask Flag. All 0s if not used.

ActiveDirectoryRights : ReadProperty
InheritanceType       : None
ObjectType            : 59ba2f42-79a2-11d0-9020-00c04fc2d3cf
InheritedObjectType   : 00000000-0000-0000-0000-000000000000
ObjectFlags           : ObjectAceTypePresent
AccessControlType     : Allow
IdentityReference     : NT AUTHORITY\Authenticated Users
IsInherited           : False
InheritanceFlags      : None
PropagationFlags      : None

SACL

ACEs in SACL defines the access attempt that are going to generate logs. Useful for defence.

ACE in SACL

Defines audit permission on an object for a specific user or group.

ActiveDirectoryRights

The following rights can be specified in a ACE:

  • Delete: Delete the object.

  • ReadControl: Read the security descriptor, except the SACL.

  • WriteDacl: Modify the object DACL in the security descriptor.

  • WriteOwner: Modify the object owner in the security descriptor.

  • CreateChild: Create child objects. For containers.

  • DeleteChild: Delete child object. For containers.

  • ListContents: List child objects. For containers. The object is hidden from user if this right nor ListObject are not granted.

  • ReadProperty: Read the property or property set specified in object type. If object type is zero, then all properties can be read. It does not allow to read the confidential properties.

  • WriteProperty: Modify the property specified in object type. If object type is zero, then all properties can be modified.

  • WritePropertyExtended: Execute a validated write. Maybe the most interesting validated write is the Self-Membership for groups, that allows to add your current user to the group with the ACE.

  • DeleteTree: Delete all the child objects with a delete-tree operation.

  • ListObject: List the object. The object is hidden from user if this right nor ListContents are not granted.

  • ControlAccess: Special permission that can be interpreted in many different ways, based on the object type. In case the object type is a GUID of a confidential property, it gives permission to read it. If is the GUID of an extended right registered in the database schema, then the right is given. In case the object type is null (GUID is all zeros) then all the extended rights are granted.

Generic Rights

  • GenericRead: ReadControl, ListContents, ReadProperty (all), ListObject.

  • GenericWrite: ReadControl, WriteProperty (all), WritePropertyExtended (all).

  • GenericExecute: ReadControl, ListContents.

  • GenericAll: Delete, WriteDacl, WriteOwner, CreateChild, DeleteChild, DeleteTree, ControlAccess (all), GenericAll, GenericWrite.

Extended Rights

  • User-Force-Change-Password: Change the user password without knowing the current password. For user objects.

  • DS-Replication-Get-Changes: To replicate the database data. For the domain object. Required to perform dcsync.

  • DS-Replication-Get-Changes-All: To replicate the database secret data. For the domain object. Required to perform dcsync.

Things to Remember

  • Files, directories, process, registries and services are protected by local DACLs, managed by local computer.

  • Domain Admins are added to the Local Administrator group by default. Hence they can access any local object in that windows computer.

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