Chapter 4. Server Types and Security Modes

This chapter provides information regarding the types of server that Samba may be configured to be. A Microsoft network administrator who wishes to migrate to or to use Samba will want to know what, within a Samba context, terms familiar to MS Windows @@ -11,7 +12,7 @@ and how these relate to MS Windows servers and clients. Firstly we should recognise the question so often asked, "Why would I want to use Samba?" So, in those chapters where the answer may be important you will see a section that highlights features and benefits. These may be for or against Samba. -

Features and Benefits

Two men were walking down a dusty road, when one suddenly kicked up a small red stone. It hurt his toe and lodged in his sandal. He took the stone out and cursed it with a passion and fury fitting his anguish. The other looked at the stone and said, that is a garnet - I @@ -47,13 +48,13 @@ So now, what are the benefits of features mentioned in this chapter? greater flexibility than MS Windows NT4 and in many cases a significantly higher utility than Active Directory domains with MS Windows 200x. -

Server Types

Administrators of Microsoft networks often refer to three +

Server Types

Administrators of Microsoft networks often refer to three different type of servers:

Domain Controller
Primary Domain Controller
Backup Domain Controller
ADS Domain Controller
Domain Member Server
Active Directory Member Server
NT4 Style Domain Member Server
Stand Alone Server

The chapters covering Domain Control, Backup Domain Control and Domain Membership provide pertinent information regarding Samba-3 configuration for each of these server roles. The reader is strongly encouraged to become intimately familiar with the information presented. -

Samba Security Modes

In this section the function and purpose of Samba's security modes are described. An accurate understanding of how Samba implements each security mode as well as how to configure MS Windows clients for each mode will significantly @@ -77,7 +78,7 @@ the way the client then tries to authenticate itself. It does not directly affec but it fits in with the client/server approach of SMB. In SMB everything is initiated and controlled by the client, and the server can only tell the client what is available and whether an action is allowed. -

User Level Security

We will describe user level security first, as it's simpler. In user level security, the client will send a session setup command directly after the protocol negotiation. @@ -95,13 +96,13 @@ It is also possible for a client to send multiple ses requests. When the server responds, it gives the client a uid to use as an authentication tag for that username/password. The client can maintain multiple authentication contexts in this way (WinDD is an example of an application that does this). -

Example Configuration

The smb.conf parameter that sets User Level Security is:

 	security = user

This is the default setting since samba-2.2.x. -

Share Level Security

Ok, now for share level security. In share level security, the client authenticates itself separately for each share. It will send a password along with each tree connection (share mount). It does not explicitly send a @@ -124,18 +125,18 @@ of the share they try to connect to (useful for home directories) and any users listed in the user = smb.conf line. The password is then checked in turn against these possible usernames. If a match is found then the client is authenticated as that user. -

Example Configuration

The smb.conf parameter that sets Share Level Security is:

 	security = share

Please note that there are reports that recent MS Windows clients do not like to work with share mode security servers. You are strongly discouraged from using share level security. -

Domain Security Mode (User Level Security)

When Samba is operating in security = domain mode, the Samba server has a domain security trust account (a machine account) and will cause all authentication requests to be passed through to the domain controllers. -

Example Configuration

Samba as a Domain Member Server

This method involves addition of the following parameters in the smb.conf file: @@ -147,24 +148,24 @@ In order for this method to work, the Samba server needs to join the MS Windows security domain. This is done as follows:

On the MS Windows NT domain controller, using the Server Manager, add a machine account for the Samba server. -
Next, on the Unix/Linux system execute:
root# smbpasswd -j DOMAIN_NAME -r PDC_NAME (samba-2.x)
root# net join -U administrator%password (samba-3)

Note

Next, on the Unix/Linux system execute:

root# smbpasswd -j DOMAIN_NAME -r PDC_NAME (samba-2.x)

root# net join -U administrator%password (samba-3)

Note

As of Samba-2.2.4 the Samba 2.2.x series can auto-join a Windows NT4 style Domain just by executing: -
+
root# smbpasswd -j DOMAIN_NAME -r PDC_NAME -U Administrator%password -
+
As of Samba-3 the same can be done by executing: -
+
root# net join -U Administrator%password -
+
It is not necessary with Samba-3 to specify the DOMAIN_NAME or the PDC_NAME as it figures this out from the smb.conf file settings. -

Use of this mode of authentication does require there to be a standard Unix account -for each user in order to assign a uid once the account has been authenticated by +for each user in order to assign a UID once the account has been authenticated by the remote Windows DC. This account can be blocked to prevent logons by clients other than -MS Windows through things such as setting an invalid shell in the +MS Windows through means such as setting an invalid shell in the /etc/passwd entry.

An alternative to assigning UIDs to Windows users on a Samba member server is @@ -173,7 +174,7 @@ in this HOWTO collection.

For more information of being a domain member, see the Domain Member section of this Howto. -

ADS Security Mode (User Level Security)

Both Samba 2.2 and 3.0 can join an Active Directory domain. This is possible even if the domain is run in native mode. Active Directory in native mode perfectly allows NT4-style domain members, contrary to @@ -187,7 +188,7 @@ authentication protocols. All your machines are running Windows 2000 and above and all use full Kerberos. In this case Samba as a NT4-style domain would still require NT-compatible authentication data. Samba in AD-member mode can accept Kerberos. -

Example Configuration

+
Example Configuration
 	realm = your.kerberos.REALM
 	security = ADS
 

@@ -197,7 +198,7 @@ AD-member mode can accept Kerberos.

Please refer to the Domain Membership and Active Directory Membership sections for more information regarding this configuration option. -

Server Security (User Level Security)

Server security mode is a left over from the time when Samba was not capable of acting as a domain member server. It is highly recommended NOT to use this feature. Server security mode has many draw backs. The draw backs include: @@ -229,7 +230,7 @@ lookups because the choice of the target authentication server is arbitrary and be determined from a domain name. In essence, a Samba server that is in server security mode is operating in what used to be known as workgroup mode. -

Example Configuration

Using MS Windows NT as an authentication server

This method involves the additions of the following parameters in the smb.conf file: @@ -238,8 +239,8 @@ This method involves the additions of the following parameters in the

-There are two ways of identifying whether or not a username and password pair was valid -or not. One uses the reply information provided as part of the authentication messaging +There are two ways of identifying whether or not a username and password pair was valid. +One uses the reply information provided as part of the authentication messaging process, the other uses just an error code.

The down-side of this mode of configuration is the fact that for security reasons Samba @@ -250,7 +251,7 @@ certain number of failed authentication attempts this will result in user lockou

Use of this mode of authentication does require there to be a standard Unix account for the user, though this account can be blocked to prevent logons by non-SMB/CIFS clients. -