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Tech Stuff - Survival Guide to NTLM

This page collects some information on the workings of NT LAN Manager (NTLM). We concentrate on those things which are particularly useful when configuring Samba and specifically a Samba Primary Domain Controller (PDC). It is by no means complete - reflecting our normal knowledge state - but some bits may be useful.

Contents

  1. Logon Process - local and global accounts and Groups

  2. SIDs and RIDs and other gobbledygook

  3. Standard Group Accounts

  4. Mapping NT Rights to Groups

You can get a useful little command line utility that will display all kinds of SIDs etc on a windows machine.

Logon Process - local and global accounts and groups

The process of using domains in NT LAN Manager (NTLM) and the relationship between domain accounts and groups and local accounts and groups is shown below:

NT Domain authentication

Notes:

  1. SAM = Security Accounts Manager and is maintained in the registry under \HKEY_LOCAL_MACHINE\SAM - this cannot be read normally even as Adminstrator - but there are wheezes that will allow you to inspect the entries should you be overtaken by insatiable curiosity.

  2. As soon as the PC is powered on the machine SID is used to establish a secure channel and trust relationship with the domain. The username is the machine name with an appended $ - thus if the name of the PC is MYPC then this account (the machine account - confusingly frequently termed the MAC) will be named MYPC$.

  3. When a human being finally deigns to logon the resulting sequence will depend on whether the logon is local or using the domain:

    1. Local logon: The LOCAL SAM is used exclusively to authenticate and creates a security token which contains the sum of all the rights obtained from the local account and its associated groups.

    2. Domain logon: The logon information is forwarded to the domain (PDC - using the secure channel established by the machine SID authentication process) and authentication takes place against the DOMAIN SAM. The process returns the rights from the user account and its associated groups. If the rights include log on locally (and almost all standard groups include this right) then further authentication takes place against the LOCAL SAM and the resulting security token comprises the sum of domain and local rights (for both the user and associated group(s)). If the domain rights do not include log on locally or there is no local account then only domain rights are obtained.

SID and RIDs and other earth shattering stuff

The term SID (Security ID) is applied to machine accounts, user accounts and groups. RID ( Relative ID) defines one or more subauthority elements in the SID - it appears (we could find no definitive reference or definition) that each item separated by a dash in the authority section can be called a RID. The generic layout of the SID is:

S-R-I-A[-A...]

Where:

Param Description Value(s) Notes
S Fixed Value S Identifies a SID.
R Revision 1 Currently Fixed Value = 1
I Identifier-authority 0 = Null
1 = world (Everyone)
2 = local
3 = creator
4 = non-unique ID
5 = NT authority
-
A Subauthority 0 = null
1 = dialup
2 = network
3 = batch
4 = interactive
5 = logon
6 = service
7 = anon logon
8 = proxy
21 = NT non-builtin IDs
32 = NT built-in
a.k.a. RID (Relative ID)
There may be one or more RIDs in a SID in the domain context there are 3 10 digit RIDs

Examples:

S-1-1-0 = Null (Everyone)
S-1-5-21-1017080363-1132274894-948791989-500 = Administrator
S-1-5-32-545 = Users group (local)
S-1-5-32-1017080363-1132274894-948791989-513 = domain users

The currently logged in account is maintained in the registry under \HKEY_USERS.

Standard Group Accounts

The following are standard group accounts used by Windows servers (well NT4.0 anyway). Each group has an assigned set of rights. This MS Knowledge Article 243330 provides more information.

The column Samba with yes below indicates that this account is required in a pure Samba environment - one in which Samba is being used, say, as an NFS replacement and in which no Windows systems need be present. All the others are required (and possibly others) to map existing Windows accounts into the Samba system so that an NT/Win2K workstation can continue to use its well loved Group account names.

The accounts listed below are automagically created by an non-LDAP Samba3 implementation. The tools available with Samba3 (from IDEALX) create the accounts below with the addition of Domain Computers.

Name SID Samba Notes
Replicators S-1-5-32-552
System Operators S-1-5-32-549 workstation = Power Users
Guests S-1-5-32-546
Domain Guests S-1-5-32-DOM0-DOM1-DOM2-514 yes
Domain Admins S-1-5-32-DOM0-DOM1-DOM2-512 yes
Power Users S-1-5-32-547
Print Operators S-1-5-32-550
Administrators S-1-5-32-544
Account Operators S-1-5-32-548
Backup Operators S-1-5-32-551
Users S-1-5-32-545
Domain Users S-1-5-32-DOM0-DOM1-DOM2-513 yes
Domain Computers S-1-5-32-DOM0-DOM1-DOM2-553 yes created by IDEALX LDAP smbldap-populate.pl script but not by tdbsam.

Mapping of Groups to Rights

In a Windows domain system each standard group provides a number of rights as defined below:

Right Users Administrators Backup Operators Server Operators Print Operators Account Operators Guests
Configurable Rights
Backup files - yes yes yes - - ?
restore files - yes yes yes - - ?
change system time - yes - yes - - ?
access network yes yes yes yes yes yes ?
log on locally - yes yes yes yes yes ?
manage audit security log - yes - - - - ?
shutdown-remote - yes - yes - - ?
shutdown-local - yes yes yes yes yes ?
add workstation - yes - - - - ?
add/remove drivers - yes - - - - ?
take ownership of files - yes - - - - ?
Built-in (non-configurable) Rights
create/mod user accounts - - - yes - yes ?
create/mod global groups - yes - - - yes ?
create/mod local groups - yes - - - yes ?
assign rights - yes - - - - ?
lock server - yes - yes - - ?
override server lock - - - yes - - ?
format server hard disk - yes - yes - - ?
create common groups - yes - yes - - ?
keep local profile - yes yes yes yes yes ?
share/unshare directories - yes - yes - - ?
share/unshare printers - yes - yes yes - ?

Notes:

  1. The seemingly innocuous log on locally right indicates that if there is a local account with the same credentials (username and password) then local properties (groups) are added to the domain properties. If this right is not present then the user has only domain rights and generally can only access anything with the Everyone group property on the local machine. You can, effectively, lock yourself out of your local machine with this right.

Samba Net Commands

The following are some of the new net commands in Samba 3.x. (see man net for full details).

Cmd Params Notes
net getlocalsid [PDC Name] Displays the SID of the domain in format:
S-1-5-21-AUTH0-AUTH1-AUTH2
net groupmap list Displays the name and SID of the groups available for the domain.

Local SID

To obtain the SID of a local machine (for the current logged in user) use:

# use regedit 
\HKEY_USERS
# the final RID will indicate the user

To obtain the SID of a local machine (for the current logged in user) use:

# use regedit 
\HKEY_USERS
# the final RID will indicate the user

More to Come - Under Construction

Under Construction



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