1.1. Step 0: Read the man pages

The man pages distributed with SAMBA contain lots of useful info that will help to get you started. If you don't know how to read man pages then try something like:

$ nroff -man smbd.8 | more

Other sources of information are pointed to by the Samba web site, http://www.samba.org

1.2. Step 1: Building the Binaries

To do this, first run the program ./configure in the source directory. This should automatically configure Samba for your operating system. If you have unusual needs then you may wish to run

root# ./configure --help

first to see what special options you can enable. Then exectuting

root# make

will create the binaries. Once it's successfully compiled you can use

root# make install

to install the binaries and manual pages. You can separately install the binaries and/or man pages using

root# make installbin

and

root# make installman

Note that if you are upgrading for a previous version of Samba you might like to know that the old versions of the binaries will be renamed with a ".old" extension. You can go back to the previous version with

root# make revert

if you find this version a disaster!

1.3. Step 2: The all important step

At this stage you must fetch yourself a coffee or other drink you find stimulating. Getting the rest of the install right can sometimes be tricky, so you will probably need it.

If you have installed samba before then you can skip this step.

1.4. Step 3: Create the smb configuration file.

There are sample configuration files in the examples subdirectory in the distribution. I suggest you read them carefully so you can see how the options go together in practice. See the man page for all the options.

The simplest useful configuration file would be something like this:

[global] workgroup = MYGROUP [homes] guest ok = no read only = no

which would allow connections by anyone with an account on the server, using either their login name or "homes" as the service name. (Note that I also set the workgroup that Samba is part of. See BROWSING.txt for defails)

Note that make install will not install a smb.conf file. You need to create it yourself.

Make sure you put the smb.conf file in the same place you specified in theMakefile (the default is to look for it in /usr/local/samba/lib/).

For more information about security settings for the [homes] share please refer to the document UNIX_SECURITY.txt.

1.5. Step 4: Test your config file with testparm

It's important that you test the validity of your smb.conf file using the testparm program. If testparm runs OK then it will list the loaded services. If not it will give an error message.

Make sure it runs OK and that the services look resonable before proceeding.

1.6. Step 5: Starting the smbd and nmbd

You must choose to start smbd and nmbd either as daemons or from inetd. Don't try to do both! Either you can put them in inetd.conf and have them started on demand by inetd, or you can start them as daemons either from the command line or in /etc/rc.local. See the man pages for details on the command line options. Take particular care to read the bit about what user you need to be in order to start Samba. In many cases you must be root.

The main advantage of starting smbd and nmbd as a daemon is that they will respond slightly more quickly to an initial connection request. This is, however, unlikely to be a problem.

1.7. Step 6: Try listing the shares available on your server

$ smbclient -L yourhostname

Your should get back a list of shares available on your server. If you don't then something is incorrectly setup. Note that this method can also be used to see what shares are available on other LanManager clients (such as WfWg).

If you choose user level security then you may find that Samba requests a password before it will list the shares. See the smbclient man page for details. (you can force it to list the shares without a password by adding the option -U% to the command line. This will not work with non-Samba servers)

1.8. Step 7: Try connecting with the unix client

$ smbclient //yourhostname/aservice

Typically the yourhostname would be the name of the host where you installed smbd. The aservice is any service you have defined in the smb.conf file. Try your user name if you just have a [homes] section in smb.conf.

For example if your unix host is bambi and your login name is fred you would type:

$ smbclient //bambi/fred

1.9. Step 8: Try connecting from a DOS, WfWg, Win9x, WinNT, Win2k, OS/2, etc... client

Try mounting disks. eg:

C:\WINDOWS\> net use d: \\servername\service

Try printing. eg:

C:\WINDOWS\> net use lpt1: \\servername\spoolservice

C:\WINDOWS\> print filename

Celebrate, or send me a bug report!

1.10. What If Things Don't Work?

If nothing works and you start to think "who wrote this pile of trash" then I suggest you do step 2 again (and again) till you calm down.

Then you might read the file DIAGNOSIS.txt and the FAQ. If you are still stuck then try the mailing list or newsgroup (look in the README for details). Samba has been successfully installed at thousands of sites worldwide, so maybe someone else has hit your problem and has overcome it. You could also use the WWW site to scan back issues of the samba-digest.

When you fix the problem PLEASE send me some updates to the documentation (or source code) so that the next person will find it easier.

2.1. Introduction

With the development of LanManager and Windows NT compatible password encryption for Samba, it is now able to validate user connections in exactly the same way as a LanManager or Windows NT server.

This document describes how the SMB password encryption algorithm works and what issues there are in choosing whether you want to use it. You should read it carefully, especially the part about security and the "PROS and CONS" section.

2.2. How does it work?

LanManager encryption is somewhat similar to UNIX password encryption. The server uses a file containing a hashed value of a user's password. This is created by taking the user's plaintext password, capitalising it, and either truncating to 14 bytes or padding to 14 bytes with null bytes. This 14 byte value is used as two 56 bit DES keys to encrypt a 'magic' eight byte value, forming a 16 byte value which is stored by the server and client. Let this value be known as the "hashed password".

Windows NT encryption is a higher quality mechanism, consisting of doing an MD4 hash on a Unicode version of the user's password. This also produces a 16 byte hash value that is non-reversible.

When a client (LanManager, Windows for WorkGroups, Windows 95 or Windows NT) wishes to mount a Samba drive (or use a Samba resource), it first requests a connection and negotiates the protocol that the client and server will use. In the reply to this request the Samba server generates and appends an 8 byte, random value - this is stored in the Samba server after the reply is sent and is known as the "challenge". The challenge is different for every client connection.

The client then uses the hashed password (16 byte values described above), appended with 5 null bytes, as three 56 bit DES keys, each of which is used to encrypt the challenge 8 byte value, forming a 24 byte value known as the "response".

In the SMB call SMBsessionsetupX (when user level security is selected) or the call SMBtconX (when share level security is selected), the 24 byte response is returned by the client to the Samba server. For Windows NT protocol levels the above calculation is done on both hashes of the user's password and both responses are returned in the SMB call, giving two 24 byte values.

The Samba server then reproduces the above calculation, using its own stored value of the 16 byte hashed password (read from the smbpasswd file - described later) and the challenge value that it kept from the negotiate protocol reply. It then checks to see if the 24 byte value it calculates matches the 24 byte value returned to it from the client.

If these values match exactly, then the client knew the correct password (or the 16 byte hashed value - see security note below) and is thus allowed access. If not, then the client did not know the correct password and is denied access.

Note that the Samba server never knows or stores the cleartext of the user's password - just the 16 byte hashed values derived from it. Also note that the cleartext password or 16 byte hashed values are never transmitted over the network - thus increasing security.

2.3. Important Notes About Security

The unix and SMB password encryption techniques seem similar on the surface. This similarity is, however, only skin deep. The unix scheme typically sends clear text passwords over the nextwork when logging in. This is bad. The SMB encryption scheme never sends the cleartext password over the network but it does store the 16 byte hashed values on disk. This is also bad. Why? Because the 16 byte hashed values are a "password equivalent". You cannot derive the user's password from them, but they could potentially be used in a modified client to gain access to a server. This would require considerable technical knowledge on behalf of the attacker but is perfectly possible. You should thus treat the smbpasswd file as though it contained the cleartext passwords of all your users. Its contents must be kept secret, and the file should be protected accordingly.

Ideally we would like a password scheme which neither requires plain text passwords on the net or on disk. Unfortunately this is not available as Samba is stuck with being compatible with other SMB systems (WinNT, WfWg, Win95 etc).

2.4. The smbpasswd file

In order for Samba to participate in the above protocol it must be able to look up the 16 byte hashed values given a user name. Unfortunately, as the UNIX password value is also a one way hash function (ie. it is impossible to retrieve the cleartext of the user's password given the UNIX hash of it), a separate password file containing this 16 byte value must be kept. To minimise problems with these two password files, getting out of sync, the UNIX /etc/passwd and the smbpasswd file, a utility, mksmbpasswd.sh, is provided to generate a smbpasswd file from a UNIX /etc/passwd file.

To generate the smbpasswd file from your /etc/passwd file use the following command :

$ cat /etc/passwd | mksmbpasswd.sh > /usr/local/samba/private/smbpasswd

If you are running on a system that uses NIS, use

$ ypcat passwd | mksmbpasswd.sh > /usr/local/samba/private/smbpasswd

The mksmbpasswd.sh program is found in the Samba source directory. By default, the smbpasswd file is stored in :

/usr/local/samba/private/smbpasswd

The owner of the /usr/local/samba/private/ directory should be set to root, and the permissions on it should be set to 0500 (chmod 500 /usr/local/samba/private).

Likewise, the smbpasswd file inside the private directory should be owned by root and the permissions on is should be set to 0600 (chmod 600 smbpasswd).

The format of the smbpasswd file is (The line has been wrapped here. It should appear as one entry per line in your smbpasswd file.)

username:uid:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX: [Account type]:LCT-<last-change-time>:Long name

Although only the username, uid, XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX, [Account type] and last-change-time sections are significant and are looked at in the Samba code.

It is VITALLY important that there by 32 'X' characters between the two ':' characters in the XXX sections - the smbpasswd and Samba code will fail to validate any entries that do not have 32 characters between ':' characters. The first XXX section is for the Lanman password hash, the second is for the Windows NT version.

When the password file is created all users have password entries consisting of 32 'X' characters. By default this disallows any access as this user. When a user has a password set, the 'X' characters change to 32 ascii hexadecimal digits (0-9, A-F). These are an ascii representation of the 16 byte hashed value of a user's password.

To set a user to have no password (not recommended), edit the file using vi, and replace the first 11 characters with the ascii text "NO PASSWORD" (minus the quotes).

For example, to clear the password for user bob, his smbpasswd file entry would look like :

bob:100:NO PASSWORDXXXXXXXXXXXXXXXXXXXXX:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:[U ]:LCT-00000000:Bob's full name:/bobhome:/bobshell

If you are allowing users to use the smbpasswd command to set their own passwords, you may want to give users NO PASSWORD initially so they do not have to enter a previous password when changing to their new password (not recommended). In order for you to allow this the smbpasswd program must be able to connect to the smbd daemon as that user with no password. Enable this by adding the line :

null passwords = yes

to the [global] section of the smb.conf file (this is why the above scenario is not recommended). Preferably, allocate your users a default password to begin with, so you do not have to enable this on your server.

Note : This file should be protected very carefully. Anyone with access to this file can (with enough knowledge of the protocols) gain access to your SMB server. The file is thus more sensitive than a normal unix /etc/passwd file.

2.5. The smbpasswd Command

The smbpasswd command maintains the two 32 byte password fields in the smbpasswd file. If you wish to make it similar to the unix passwd or yppasswd programs, install it in /usr/local/samba/bin/ (or your main Samba binary directory).

Note that as of Samba 1.9.18p4 this program MUST NOT BE INSTALLED setuid root (the new smbpasswd code enforces this restriction so it cannot be run this way by accident).

smbpasswd now works in a client-server mode where it contacts the local smbd to change the user's password on its behalf. This has enormous benefits - as follows.

• smbpasswd no longer has to be setuid root - an enormous range of potential security problems is eliminated.

• smbpasswd now has the capability to change passwords on Windows NT servers (this only works when the request is sent to the NT Primary Domain Controller if you are changing an NT Domain user's password).

To run smbpasswd as a normal user just type :

$ smbpasswd

Old SMB password: <type old value here - or hit return if there was no old password>

New SMB Password: <type new value>

Repeat New SMB Password: <re-type new value

If the old value does not match the current value stored for that user, or the two new values do not match each other, then the password will not be changed.

If invoked by an ordinary user it will only allow the user to change his or her own Samba password.

If run by the root user smbpasswd may take an optional argument, specifying the user name whose SMB password you wish to change. Note that when run as root smbpasswd does not prompt for or check the old password value, thus allowing root to set passwords for users who have forgotten their passwords.

smbpasswd is designed to work in the same way and be familiar to UNIX users who use the passwd or yppasswd commands.

For more details on using smbpasswd refer to the man page which will always be the definitive reference.

2.6. Setting up Samba to support LanManager Encryption

This is a very brief description on how to setup samba to support password encryption.

1. compile and install samba as usual

2. enable encrypted passwords in smb.conf by adding the line encrypt passwords = yes in the [global] section

3. create the initial smbpasswd password file in the place you specified in the Makefile (--prefix=<dir>). See the notes under the The smbpasswd File section earlier in the document for details.

Note that you can test things using smbclient.

3.1. Instructions

The Distributed File System (or Dfs) provides a means of separating the logical view of files and directories that users see from the actual physical locations of these resources on the network. It allows for higher availability, smoother storage expansion, load balancing etc. For more information about Dfs, refer to Microsoft documentation.

This document explains how to host a Dfs tree on a Unix machine (for Dfs-aware clients to browse) using Samba.

To enable SMB-based DFS for Samba, configure it with the --with-msdfs option. Once built, a Samba server can be made a Dfs server by setting the global boolean host msdfs parameter in the smb.conf file. You designate a share as a Dfs root using the share level boolean msdfs root parameter. A Dfs root directory on Samba hosts Dfs links in the form of symbolic links that point to other servers. For example, a symbolic link junction->msdfs:storage1\share1 in the share directory acts as the Dfs junction. When Dfs-aware clients attempt to access the junction link, they are redirected to the storage location (in this case, \\storage1\share1).

Dfs trees on Samba work with all Dfs-aware clients ranging from Windows 95 to 2000.

Here's an example of setting up a Dfs tree on a Samba server.

# The smb.conf file: [global] netbios name = SAMBA host msdfs = yes [dfs] path = /export/dfsroot msdfs root = yes

In the /export/dfsroot directory we set up our dfs links to other servers on the network.

root# cd /export/dfsroot

root# chown root /export/dfsroot

root# chmod 755 /export/dfsroot

root# ln -s msdfs:storageA\\shareA linka

root# ln -s msdfs:serverB\\share,serverC\\share linkb

You should set up the permissions and ownership of the directory acting as the Dfs root such that only designated users can create, delete or modify the msdfs links. Also note that symlink names should be all lowercase. This limitation exists to have Samba avoid trying all the case combinations to get at the link name. Finally set up the symbolic links to point to the network shares you want, and start Samba.

Users on Dfs-aware clients can now browse the Dfs tree on the Samba server at \\samba\dfs. Accessing links linka or linkb (which appear as directories to the client) takes users directly to the appropriate shares on the network.

4.1. Introduction

Beginning with the 2.2.0 release, Samba supports the native Windows NT printing mechanisms implemented via MS-RPC (i.e. the SPOOLSS named pipe). Previous versions of Samba only supported LanMan printing calls.

The additional functionality provided by the new SPOOLSS support includes:

• Support for downloading printer driver files to Windows 95/98/NT/2000 clients upon demand.

• Uploading of printer drivers via the Windows NT Add Printer Wizard (APW) or the Imprints tool set (refer to http://imprints.sourceforge.net).

• Support for the native MS-RPC printing calls such as StartDocPrinter, EnumJobs(), etc... (See the MSDN documentation at http://msdn.microsoft.com/ for more information on the Win32 printing API)

• Support for NT Access Control Lists (ACL) on printer objects

• Improved support for printer queue manipulation through the use of an internal databases for spooled job information

There has been some initial confusion about what all this means and whether or not it is a requirement for printer drivers to be installed on a Samba host in order to support printing from Windows clients. A bug existed in Samba 2.2.0 which made Windows NT/2000 clients require that the Samba server possess a valid driver for the printer. This is fixed in Samba 2.2.1 and once again, Windows NT/2000 clients can use the local APW for installing drivers to be used with a Samba served printer. This is the same behavior exhibited by Windows 9x clients. As a side note, Samba does not use these drivers in any way to process spooled files. They are utilized entirely by the clients.

The following MS KB article, may be of some help if you are dealing with Windows 2000 clients: How to Add Printers with No User Interaction in Windows 2000

http://support.microsoft.com/support/kb/articles/Q189/1/05.ASP

4.2. Configuration

4.3. The Imprints Toolset

The Imprints tool set provides a UNIX equivalent of the Windows NT Add Printer Wizard. For complete information, please refer to the Imprints web site at http://imprints.sourceforge.net/ as well as the documentation included with the imprints source distribution. This section will only provide a brief introduction to the features of Imprints.

4.4. Migration to from Samba 2.0.x to 2.2.x

Given that printer driver management has changed (we hope improved) in 2.2 over prior releases, migration from an existing setup to 2.2 can follow several paths.

Windows clients have a tendency to remember things for quite a while. For example, if a Windows NT client has attached to a Samba 2.0 server, it will remember the server as a LanMan printer server. Upgrading the Samba host to 2.2 makes support for MSRPC printing possible, but the NT client will still remember the previous setting.

In order to give an NT client printing "amesia" (only necessary if you want to use the newer MSRPC printing functionality in Samba), delete the registry keys associated with the print server contained in [HKLM\SYSTEM\CurrentControlSet\Control\Print]. The spooler service on the client should be stopped prior to doing this:

C:\WINNT\ > net stop spooler

All the normal disclaimers about editing the registry go here. Be careful, and know what you are doing.

The spooler service should be restarted after you have finished removing the appropriate registry entries by replacing the stop command above with start.

Windows 9x clients will continue to use LanMan printing calls with a 2.2 Samba server so there is no need to perform any of these modifications on non-NT clients.

Here are the possible scenarios for supporting migration:

• If you do not desire the new Windows NT print driver support, nothing needs to be done. All existing parameters work the same.

• If you want to take advantage of NT printer driver support but do not want to migrate the 9x drivers to the new setup, the leave the existing printers.def file. When smbd attempts to locate a 9x driver for the printer in the TDB and fails it will drop down to using the printers.def (and all associated parameters). The make_printerdef tool will also remain for backwards compatibility but will be moved to the "this tool is the old way of doing it" pile.

• If you install a Windows 9x driver for a printer on your Samba host (in the printing TDB), this information will take precedence and the three old printing parameters will be ignored (including print driver location).

• If you want to migrate an existing printers.def file into the new setup, the current only solution is to use the Windows NT APW to install the NT drivers and the 9x drivers. This can be scripted using smbclient and rpcclient. See the Imprints installation client at http://imprints.sourceforge.net/ for an example.

5.1. Joining an NT Domain with Samba 2.2

In order for a Samba-2 server to join an NT domain, you must first add the NetBIOS name of the Samba server to the NT domain on the PDC using Server Manager for Domains. This creates the machine account in the domain (PDC) SAM. Note that you should add the Samba server as a "Windows NT Workstation or Server", NOT as a Primary or backup domain controller.

Assume you have a Samba-2 server with a NetBIOS name of SERV1 and are joining an NT domain called DOM, which has a PDC with a NetBIOS name of DOMPDC and two backup domain controllers with NetBIOS names DOMBDC1 and DOMBDC2 .

In order to join the domain, first stop all Samba daemons and run the command:

root# smbpasswd -j DOM -r DOMPDC

as we are joining the domain DOM and the PDC for that domain (the only machine that has write access to the domain SAM database) is DOMPDC. If this is successful you will see the message:

smbpasswd: Joined domain DOM.

in your terminal window. See the smbpasswd(8) man page for more details.

There is existing development code to join a domain without having to create the machine trust account on the PDC beforehand. This code will hopefully be available soon in release branches as well.

This command goes through the machine account password change protocol, then writes the new (random) machine account password for this Samba server into a file in the same directory in which an smbpasswd file would be stored - normally :

/usr/local/samba/private

In Samba 2.0.x, the filename looks like this:

<NT DOMAIN NAME>.<Samba Server Name>.mac

The .mac suffix stands for machine account password file. So in our example above, the file would be called:

DOM.SERV1.mac

In Samba 2.2, this file has been replaced with a TDB (Trivial Database) file named secrets.tdb.

This file is created and owned by root and is not readable by any other user. It is the key to the domain-level security for your system, and should be treated as carefully as a shadow password file.

Now, before restarting the Samba daemons you must edit your smb.conf(5) file to tell Samba it should now use domain security.

Change (or add) your security = line in the [global] section of your smb.conf to read:

security = domain

Next change the workgroup = line in the [global] section to read:

workgroup = DOM

as this is the name of the domain we are joining.

You must also have the parameter encrypt passwords set to yes in order for your users to authenticate to the NT PDC.

Finally, add (or modify) a password server = line in the [global] section to read:

password server = DOMPDC DOMBDC1 DOMBDC2

These are the primary and backup domain controllers Samba will attempt to contact in order to authenticate users. Samba will try to contact each of these servers in order, so you may want to rearrange this list in order to spread out the authentication load among domain controllers.

Alternatively, if you want smbd to automatically determine the list of Domain controllers to use for authentication, you may set this line to be :

password server = *

This method, which was introduced in Samba 2.0.6, allows Samba to use exactly the same mechanism that NT does. This method either broadcasts or uses a WINS database in order to find domain controllers to authenticate against.

Finally, restart your Samba daemons and get ready for clients to begin using domain security!

5.2. Samba and Windows 2000 Domains

Many people have asked regarding the state of Samba's ability to participate in a Windows 2000 Domain. Samba 2.2 is able to act as a member server of a Windows 2000 domain operating in mixed or native mode.

There is much confusion between the circumstances that require a "mixed" mode Win2k DC and a when this host can be switched to "native" mode. A "mixed" mode Win2k domain controller is only needed if Windows NT BDCs must exist in the same domain. By default, a Win2k DC in "native" mode will still support NetBIOS and NTLMv1 for authentication of legacy clients such as Windows 9x and NT 4.0. Samba has the same requirements as a Windows NT 4.0 member server.

The steps for adding a Samba 2.2 host to a Win2k domain are the same as those for adding a Samba server to a Windows NT 4.0 domain. The only exception is that the "Server Manager" from NT 4 has been replaced by the "Active Directory Users and Computers" MMC (Microsoft Management Console) plugin.

5.3. Why is this better than security = server?

Currently, domain security in Samba doesn't free you from having to create local Unix users to represent the users attaching to your server. This means that if domain user DOM\fred attaches to your domain security Samba server, there needs to be a local Unix user fred to represent that user in the Unix filesystem. This is very similar to the older Samba security mode security = server, where Samba would pass through the authentication request to a Windows NT server in the same way as a Windows 95 or Windows 98 server would.

Please refer to the Winbind paper for information on a system to automatically assign UNIX uids and gids to Windows NT Domain users and groups. This code is available in development branches only at the moment, but will be moved to release branches soon.

The advantage to domain-level security is that the authentication in domain-level security is passed down the authenticated RPC channel in exactly the same way that an NT server would do it. This means Samba servers now participate in domain trust relationships in exactly the same way NT servers do (i.e., you can add Samba servers into a resource domain and have the authentication passed on from a resource domain PDC to an account domain PDC.

In addition, with security = server every Samba daemon on a server has to keep a connection open to the authenticating server for as long as that daemon lasts. This can drain the connection resources on a Microsoft NT server and cause it to run out of available connections. With security = domain, however, the Samba daemons connect to the PDC/BDC only for as long as is necessary to authenticate the user, and then drop the connection, thus conserving PDC connection resources.

And finally, acting in the same manner as an NT server authenticating to a PDC means that as part of the authentication reply, the Samba server gets the user identification information such as the user SID, the list of NT groups the user belongs to, etc. All this information will allow Samba to be extended in the future into a mode the developers currently call appliance mode. In this mode, no local Unix users will be necessary, and Samba will generate Unix uids and gids from the information passed back from the PDC when a user is authenticated, making a Samba server truly plug and play in an NT domain environment. Watch for this code soon.

NOTE: Much of the text of this document was first published in the Web magazine LinuxWorld as the article Doing the NIS/NT Samba.

6.1. Prerequisite Reading

Before you continue readingin this chapter, please make sure that you are comfortable with configuring basic files services in smb.conf and how to enable and administrate password encryption in Samba. Theses two topics are covered in the smb.conf(5) manpage and the Encryption chapter of this HOWTO Collection.

6.2. Background

Version of Samba prior to release 2.2 had marginal capabilities to act as a Windows NT 4.0 Primary Domain Controller (PDC). Beginning with Samba 2.2.0, we are proud to announce official support for Windows NT 4.0 style domain logons from Windows NT 4.0 (through SP6) and Windows 2000 (through SP1) clients. This article outlines the steps necessary for configuring Samba as a PDC. It is necessary to have a working Samba server prior to implementing the PDC functionality. If you have not followed the steps outlined in UNIX_INSTALL.html, please make sure that your server is configured correctly before proceeding. Another good resource in the smb.conf(5) man page. The following functionality should work in 2.2:

• domain logons for Windows NT 4.0/2000 clients.

• placing a Windows 9x client in user level security

• retrieving a list of users and groups from a Samba PDC to Windows 9x/NT/2000 clients

• roving (roaming) user profiles

• Windows NT 4.0 style system policies

The following pieces of functionality are not included in the 2.2 release:

• Windows NT 4 domain trusts

• SAM replication with Windows NT 4.0 Domain Controllers (i.e. a Samba PDC and a Windows NT BDC or vice versa)

• Adding users via the User Manager for Domains

• Acting as a Windows 2000 Domain Controller (i.e. Kerberos and Active Directory)

Please note that Windows 9x clients are not true members of a domain for reasons outlined in this article. Therefore the protocol for support Windows 9x style domain logons is completely different from NT4 domain logons and has been officially supported for some time.

Implementing a Samba PDC can basically be divided into 2 broad steps.

1. Configuring the Samba PDC

2. Creating machine trust accounts and joining clients to the domain

There are other minor details such as user profiles, system policies, etc... However, these are not necessarily specific to a Samba PDC as much as they are related to Windows NT networking concepts. They will be mentioned only briefly here.

6.3. Configuring the Samba Domain Controller

The first step in creating a working Samba PDC is to understand the parameters necessary in smb.conf. I will not attempt to re-explain the parameters here as they are more that adequately covered in the smb.conf man page. For convenience, the parameters have been linked with the actual smb.conf description.

Here is an example smb.conf for acting as a PDC:

[global] ; Basic server settings netbios name = POGO workgroup = NARNIA ; we should act as the domain and local master browser os level = 64 preferred master = yes domain master = yes local master = yes ; security settings (must user security = user) security = user ; encrypted passwords are a requirement for a PDC encrypt passwords = yes ; support domain logons domain logons = yes ; where to store user profiles? logon path = \\%N\profiles\%u ; where is a user's home directory and where should it ; be mounted at? logon drive = H: logon home = \\homeserver\%u ; specify a generic logon script for all users ; this is a relative **DOS** path to the [netlogon] share logon script = logon.cmd ; necessary share for domain controller [netlogon] path = /usr/local/samba/lib/netlogon writeable = no write list = ntadmin ; share for storing user profiles [profiles] path = /export/smb/ntprofile writeable = yes create mask = 0600 directory mask = 0700

There are a couple of points to emphasize in the above configuration.

• Encrypted passwords must be enabled. For more details on how to do this, refer to ENCRYPTION.html.

• The server must support domain logons and a [netlogon] share

• The server must be the domain master browser in order for Windows client to locate the server as a DC. Please refer to the various Network Browsing documentation included with this distribution for details.

As Samba 2.2 does not offer a complete implementation of group mapping between Windows NT groups and UNIX groups (this is really quite complicated to explain in a short space), you should refer to the domain admin users and domain admin group smb.conf parameters for information of creating a Domain Admins style accounts.

6.4. Creating Machine Trust Accounts and Joining Clients to the Domain

A machine trust account is a samba user account owned by a computer. The account password acts as the shared secret for secure communication with the Domain Controller. This is a security feature to prevent an unauthorized machine with the same netbios name from joining the domain and gaining access to domain user/group accounts. Hence a Windows 9x host is never a true member of a domain because it does not posses a machine trust account, and thus has no shared secret with the DC.

On a Windows NT PDC, these machine trust account passwords are stored in the registry. A Samba PDC stores these accounts in the same location as user LanMan and NT password hashes (currently smbpasswd). However, machine trust accounts only possess and use the NT password hash.

Because Samba requires machine accounts to possess a UNIX uid from which an Windows NT SID can be generated, all of these accounts must have an entry in /etc/passwd and smbpasswd. Future releases will alleviate the need to create /etc/passwd entries.

There are two means of creating machine trust accounts.

• Manual creation before joining the client to the domain. In this case, the password is set to a known value -- the lower case of the machine's netbios name.

• Creation of the account at the time of joining the domain. In this case, the session key of the administrative account used to join the client to the domain acts as an encryption key for setting the password to a random value (This is the recommended method).

6.5. Common Problems and Errors

• I cannot include a '$' in a machine name.

  A 'machine name' in (typically) /etc/passwd of the machine name with a '$' appended. FreeBSD (and other BSD systems ?) won't create a user with a '$' in their name.

  The problem is only in the program used to make the entry, once made, it works perfectly. So create a user without the '$' and use vipw to edit the entry, adding the '$'. Or create the whole entry with vipw if you like, make sure you use a unique uid !

• I get told "You already have a connection to the Domain...." or "Cannot join domain, the credentials supplied conflict with an existing set.." when creating a machine account.

  This happens if you try to create a machine account from the machine itself and already have a connection (e.g. mapped drive) to a share (or IPC$) on the Samba PDC. The following command will remove all network drive connections:

  C:\WINNT\> net use * /d

  Further, if the machine is a already a 'member of a workgroup' that is the same name as the domain you are joining (bad idea) you will get this message. Change the workgroup name to something else, it does not matter what, reboot, and try again.

• The system can not log you on (C000019B)....

  I joined the domain successfully but after upgrading to a newer version of the Samba code I get the message, "The system can not log you on (C000019B), Please try a gain or consult your system administrator" when attempting to logon.

  This occurs when the domain SID stored in private/WORKGROUP.SID is changed. For example, you remove the file and smbd automatically creates a new one. Or you are swapping back and forth between versions 2.0.7, TNG and the HEAD branch code (not recommended). The only way to correct the problem is to restore the original domain SID or remove the domain client from the domain and rejoin.

• The machine account for this computer either does not exist or is not accessible.

  When I try to join the domain I get the message "The machine account for this computer either does not exist or is not accessible". Whats wrong?

  This problem is caused by the PDC not having a suitable machine account. If you are using the add user script method to create accounts then this would indicate that it has not worked. Ensure the domain admin user system is working.

  Alternatively if you are creating account entries manually then they have not been created correctly. Make sure that you have the entry correct for the machine account in smbpasswd file on the Samba PDC. If you added the account using an editor rather than using the smbpasswd utility, make sure that the account name is the machine netbios name with a '$' appended to it ( ie. computer_name$ ). There must be an entry in both /etc/passwd and the smbpasswd file. Some people have reported that inconsistent subnet masks between the Samba server and the NT client have caused this problem. Make sure that these are consistent for both client and server.

• When I attempt to login to a Samba Domain from a NT4/W2K workstation, I get a message about my account being disabled.

  This problem is caused by a PAM related bug in Samba 2.2.0. This bug is fixed in 2.2.1. Other symptoms could be unaccessible shares on NT/W2K member servers in the domain or the following error in your smbd.log: passdb/pampass.c:pam_account(268) PAM: UNKNOWN ERROR for User: %user%

  At first be ensure to enable the useraccounts with smbpasswd -e %user%, this is normaly done, when you create an account.

  In order to work around this problem in 2.2.0, configure the account control flag in /etc/pam.d/samba file as follows:

  account required pam_permit.so

  If you want to remain backward compatibility to samba 2.0.x use pam_permit.so, it's also possible to use pam_pwdb.so. There are some bugs if you try to use pam_unix.so, if you need this, be ensure to use the most recent version of this file.

6.6. System Policies and Profiles

Much of the information necessary to implement System Policies and Roving User Profiles in a Samba domain is the same as that for implementing these same items in a Windows NT 4.0 domain. You should read the white paper Implementing Profiles and Policies in Windows NT 4.0 available from Microsoft.

Here are some additional details:

• What about Windows NT Policy Editor ?

  To create or edit ntconfig.pol you must use the NT Server Policy Editor, poledit.exe which is included with NT Server but not NT Workstation. There is a Policy Editor on a NTws but it is not suitable for creating Domain Policies. Further, although the Windows 95 Policy Editor can be installed on an NT Workstation/Server, it will not work with NT policies because the registry key that are set by the policy templates. However, the files from the NT Server will run happily enough on an NTws. You need poledit.exe, common.adm and winnt.adm. It is convenient to put the two *.adm files in c:\winnt\inf which is where the binary will look for them unless told otherwise. Note also that that directory is 'hidden'.

  The Windows NT policy editor is also included with the Service Pack 3 (and later) for Windows NT 4.0. Extract the files using servicepackname /x, ie thats Nt4sp6ai.exe /x for service pack 6a. The policy editor, poledit.exe and the associated template files (*.adm) should be extracted as well. It is also possible to downloaded the policy template files for Office97 and get a copy of the policy editor. Another possible location is with the Zero Administration Kit available for download from Microsoft.

• Can Win95 do Policies ?

  Install the group policy handler for Win9x to pick up group policies. Look on the Win98 CD in \tools\reskit\netadmin\poledit. Install group policies on a Win9x client by double-clicking grouppol.inf. Log off and on again a couple of times and see if Win98 picks up group policies. Unfortunately this needs to be done on every Win9x machine that uses group policies....

  If group policies don't work one reports suggests getting the updated (read: working) grouppol.dll for Windows 9x. The group list is grabbed from /etc/group.

• How do I get 'User Manager' and 'Server Manager'

  Since I don't need to buy an NT Server CD now, how do I get the 'User Manager for Domains', the 'Server Manager' ?

  Microsoft distributes a version of these tools called nexus for installation on Windows 95 systems. The tools set includes

  • Server Manager

  • User Manager for Domains

  • Event Viewer

  Click here to download the archived file ftp://ftp.microsoft.com/Softlib/MSLFILES/NEXUS.EXE

  The Windows NT 4.0 version of the 'User Manager for Domains' and 'Server Manager' are available from Microsoft via ftp from ftp://ftp.microsoft.com/Softlib/MSLFILES/SRVTOOLS.EXE

6.7. What other help can I get ?

There are many sources of information available in the form of mailing lists, RFC's and documentation. The docs that come with the samba distribution contain very good explanations of general SMB topics such as browsing.

• What are some diagnostics tools I can use to debug the domain logon process and where can I find them?

  One of the best diagnostic tools for debugging problems is Samba itself. You can use the -d option for both smbd and nmbd to specifiy what 'debug level' at which to run. See the man pages on smbd, nmbd and smb.conf for more information on debugging options. The debug level can range from 1 (the default) to 10 (100 for debugging passwords).

  Another helpful method of debugging is to compile samba using the gcc -g flag. This will include debug information in the binaries and allow you to attach gdb to the running smbd / nmbd process. In order to attach gdb to an smbd process for an NT workstation, first get the workstation to make the connection. Pressing ctrl-alt-delete and going down to the domain box is sufficient (at least, on the first time you join the domain) to generate a 'LsaEnumTrustedDomains'. Thereafter, the workstation maintains an open connection, and therefore there will be an smbd process running (assuming that you haven't set a really short smbd idle timeout) So, in between pressing ctrl alt delete, and actually typing in your password, you can gdb attach and continue.

  Some useful samba commands worth investigating:

  • testparam | more

  • smbclient -L //{netbios name of server}

  An SMB enabled version of tcpdump is available from http://www.tcpdup.org/. Ethereal, another good packet sniffer for UNIX and Win32 hosts, can be downloaded from http://www.ethereal.com.

  For tracing things on the Microsoft Windows NT, Network Monitor (aka. netmon) is available on the Microsoft Developer Network CD's, the Windows NT Server install CD and the SMS CD's. The version of netmon that ships with SMS allows for dumping packets between any two computers (ie. placing the network interface in promiscuous mode). The version on the NT Server install CD will only allow monitoring of network traffic directed to the local NT box and broadcasts on the local subnet. Be aware that Ethereal can read and write netmon formatted files.

• How do I install 'Network Monitor' on an NT Workstation or a Windows 9x box?

  Installing netmon on an NT workstation requires a couple of steps. The following are for installing Netmon V4.00.349, which comes with Microsoft Windows NT Server 4.0, on Microsoft Windows NT Workstation 4.0. The process should be similar for other version of Windows NT / Netmon. You will need both the Microsoft Windows NT Server 4.0 Install CD and the Workstation 4.0 Install CD.

  Initially you will need to install 'Network Monitor Tools and Agent' on the NT Server. To do this

  • Goto Start - Settings - Control Panel - Network - Services - Add

  • Select the 'Network Monitor Tools and Agent' and click on 'OK'.

  • Click 'OK' on the Network Control Panel.

  • Insert the Windows NT Server 4.0 install CD when prompted.

  At this point the Netmon files should exist in %SYSTEMROOT%\System32\netmon\*.*. Two subdirectories exist as well, parsers\ which contains the necessary DLL's for parsing the netmon packet dump, and captures\.

  In order to install the Netmon tools on an NT Workstation, you will first need to install the 'Network Monitor Agent' from the Workstation install CD.

  • Goto Start - Settings - Control Panel - Network - Services - Add

  • Select the 'Network Monitor Agent' and click on 'OK'.

  • Click 'OK' on the Network Control Panel.

  • Insert the Windows NT Workstation 4.0 install CD when prompted.

  Now copy the files from the NT Server in %SYSTEMROOT%\System32\netmon\*.* to %SYSTEMROOT%\System32\netmon\*.* on the Workstation and set permissions as you deem appropriate for your site. You will need administrative rights on the NT box to run netmon.

  To install Netmon on a Windows 9x box install the network monitor agent from the Windows 9x CD (\admin\nettools\netmon). There is a readme file located with the netmon driver files on the CD if you need information on how to do this. Copy the files from a working Netmon installation.

• The following is a list if helpful URLs and other links:

  • Home of Samba site http://samba.org. We have a mirror near you !

  • The Development document on the Samba mirrors might mention your problem. If so, it might mean that the developers are working on it.

  • See how Scott Merrill simulates a BDC behavior at http://www.skippy.net/linux/smb-howto.html.

  • Although 2.0.7 has almost had its day as a PDC, David Bannon will keep the 2.0.7 PDC pages at http://bioserve.latrobe.edu.au/samba going for a while yet.

  • Misc links to CIFS information http://samba.org/cifs/

  • NT Domains for Unix http://mailhost.cb1.com/~lkcl/ntdom/

  • FTP site for older SMB specs: ftp://ftp.microsoft.com/developr/drg/CIFS/

• How do I get help from the mailing lists ?

  There are a number of Samba related mailing lists. Go to http://samba.org, click on your nearest mirror and then click on Support and then click on Samba related mailing lists.

  For questions relating to Samba TNG go to http://www.samba-tng.org/ It has been requested that you don't post questions about Samba-TNG to the main stream Samba lists.

  If you post a message to one of the lists please observe the following guide lines :

  • Always remember that the developers are volunteers, they are not paid and they never guarantee to produce a particular feature at a particular time. Any time lines are 'best guess' and nothing more.

  • Always mention what version of samba you are using and what operating system its running under. You should probably list the relevant sections of your smb.conf file, at least the options in [global] that affect PDC support.

  • In addition to the version, if you obtained Samba via CVS mention the date when you last checked it out.

  • Try and make your question clear and brief, lots of long, convoluted questions get deleted before they are completely read ! Don't post html encoded messages (if you can select colour or font size its html).

  • If you run one of those nifty 'I'm on holidays' things when you are away, make sure its configured to not answer mailing lists.

  • Don't cross post. Work out which is the best list to post to and see what happens, ie don't post to both samba-ntdom and samba-technical. Many people active on the lists subscribe to more than one list and get annoyed to see the same message two or more times. Often someone will see a message and thinking it would be better dealt with on another, will forward it on for you.

  • You might include partial log files written at a debug level set to as much as 20. Please don't send the entire log but enough to give the context of the error messages.

  • (Possibly) If you have a complete netmon trace ( from the opening of the pipe to the error ) you can send the *.CAP file as well.

  • Please think carefully before attaching a document to an email. Consider pasting the relevant parts into the body of the message. The samba mailing lists go to a huge number of people, do they all need a copy of your smb.conf in their attach directory ?

• How do I get off the mailing lists ?

  To have your name removed from a samba mailing list, go to the same place you went to to get on it. Go to http://lists.samba.org, click on your nearest mirror and then click on Support and then click on Samba related mailing lists. Or perhaps see here

  Please don't post messages to the list asking to be removed, you will just be referred to the above address (unless that process failed in some way...)

6.8. Domain Control for Windows 9x/ME

A domain and a workgroup are exactly the same thing in terms of network browsing. The difference is that a distributable authentication database is associated with a domain, for secure login access to a network. Also, different access rights can be granted to users if they successfully authenticate against a domain logon server (NT server and other systems based on NT server support this, as does at least Samba TNG now).

The SMB client logging on to a domain has an expectation that every other server in the domain should accept the same authentication information. Network browsing functionality of domains and workgroups is identical and is explained in BROWSING.txt. It should be noted, that browsing is total orthogonal to logon support.

Issues related to the single-logon network model are discussed in this document. Samba supports domain logons, network logon scripts, and user profiles for MS Windows for workgroups and MS Windows 9X clients.

When an SMB client in a domain wishes to logon it broadcast requests for a logon server. The first one to reply gets the job, and validates its password using whatever mechanism the Samba administrator has installed. It is possible (but very stupid) to create a domain where the user database is not shared between servers, ie they are effectively workgroup servers advertising themselves as participating in a domain. This demonstrates how authentication is quite different from but closely involved with domains.

Another thing commonly associated with single-logon domains is remote administration over the SMB protocol. Again, there is no reason why this cannot be implemented with an underlying username database which is different from the Windows NT SAM. Support for the Remote Administration Protocol is planned for a future release of Samba.

Network logon support as discussed in this section is aimed at Window for Workgroups, and Windows 9X clients.

Support for profiles is confirmed as working for Win95, NT 4.0 and NT 3.51. It is possible to specify: the profile location; script file to be loaded on login; the user's home directory; and for NT a kick-off time could also now easily be supported. However, there are some differences between Win9X profile support and WinNT profile support. These are discussed below.

With NT Workstations, all this does not require the use or intervention of an NT 4.0 or NT 3.51 server: Samba can now replace the logon services provided by an NT server, to a limited and experimental degree (for example, running "User Manager for Domains" will not provide you with access to a domain created by a Samba Server).

With Win95, the help of an NT server can be enlisted, both for profile storage and for user authentication. For details on user authentication, see security_level.txt. For details on profile storage, see below.

Using these features you can make your clients verify their logon via the Samba server; make clients run a batch file when they logon to the network and download their preferences, desktop and start menu.

Before launching into the configuration instructions, it is worthwhile looking at how a Win9X client performs a logon:

1. The client broadcasts (to the IP broadcast address of the subnet it is in) a NetLogon request. This is sent to the NetBIOS address DOMAIN<00> at the NetBIOS layer. The client chooses the first response it receives, which contains the NetBIOS name of the logon server to use in the format of \\SERVER.

2. The client then connects to that server, logs on (does an SMBsessetupX) and then connects to the IPC$ share (using an SMBtconX).

3. The client then does a NetWkstaUserLogon request, which retrieves the name of the user's logon script.

4. The client then connects to the NetLogon share and searches for this and if it is found and can be read, is retrieved and executed by the client. After this, the client disconnects from the NetLogon share.

5. The client then sends a NetUserGetInfo request to the server, to retrieve the user's home share, which is used to search for profiles. Since the response to the NetUserGetInfo request does not contain much more the user's home share, profiles for Win9X clients MUST reside in the user home directory.

6. The client then connects to the user's home share and searches for the user's profile. As it turns out, you can specify the users home share as a sharename and path. For example, \\server\fred\.profile. If the profiles are found, they are implemented.

7. The client then disconnects from the user's home share, and reconnects to the NetLogon share and looks for CONFIG.POL, the policies file. If this is found, it is read and implemented.

6.9. DOMAIN_CONTROL.txt : Windows NT Domain Control & Samba

NOTE : The term "Domain Controller" and those related to it refer to one specific method of authentication that can underly an SMB domain. Domain Controllers prior to Windows NT Server 3.1 were sold by various companies and based on private extensions to the LAN Manager 2.1 protocol. Windows NT introduced Microsoft-specific ways of distributing the user authentication database. See DOMAIN.txt for examples of how Samba can participate in or create SMB domains based on shared authentication database schemes other than the Windows NT SAM.

Windows NT Server can be installed as either a plain file and print server (WORKGROUP workstation or server) or as a server that participates in Domain Control (DOMAIN member, Primary Domain controller or Backup Domain controller). The same is true for OS/2 Warp Server, Digital Pathworks and other similar products, all of which can participate in Domain Control along with Windows NT.

To many people these terms can be confusing, so let's try to clear the air.

Every Windows NT system (workstation or server) has a registry database. The registry contains entries that describe the initialization information for all services (the equivalent of Unix Daemons) that run within the Windows NT environment. The registry also contains entries that tell application software where to find dynamically loadable libraries that they depend upon. In fact, the registry contains entries that describes everything that anything may need to know to interact with the rest of the system.

The registry files can be located on any Windows NT machine by opening a command prompt and typing:

C:\WINNT\> dir %SystemRoot%\System32\config

The environment variable %SystemRoot% value can be obtained by typing:

C:\WINNT>echo %SystemRoot%

The active parts of the registry that you may want to be familiar with are the files called: default, system, software, sam and security.

In a domain environment, Microsoft Windows NT domain controllers participate in replication of the SAM and SECURITY files so that all controllers within the domain have an exactly identical copy of each.

The Microsoft Windows NT system is structured within a security model that says that all applications and services must authenticate themselves before they can obtain permission from the security manager to do what they set out to do.

The Windows NT User database also resides within the registry. This part of the registry contains the user's security identifier, home directory, group memberships, desktop profile, and so on.

Every Windows NT system (workstation as well as server) will have its own registry. Windows NT Servers that participate in Domain Security control have a database that they share in common - thus they do NOT own an independent full registry database of their own, as do Workstations and plain Servers.

The User database is called the SAM (Security Access Manager) database and is used for all user authentication as well as for authentication of inter- process authentication (ie: to ensure that the service action a user has requested is permitted within the limits of that user's privileges).

The Samba team have produced a utility that can dump the Windows NT SAM into smbpasswd format: see ENCRYPTION.txt for information on smbpasswd and /pub/samba/pwdump on your nearest Samba mirror for the utility. This facility is useful but cannot be easily used to implement SAM replication to Samba systems.

Windows for Workgroups, Windows 95, and Windows NT Workstations and Servers can participate in a Domain security system that is controlled by Windows NT servers that have been correctly configured. At most every domain will have ONE Primary Domain Controller (PDC). It is desirable that each domain will have at least one Backup Domain Controller (BDC).

The PDC and BDCs then participate in replication of the SAM database so that each Domain Controlling participant will have an up to date SAM component within its registry.

7.1. Abstract

Integration of UNIX and Microsoft Windows NT through a unified logon has been considered a "holy grail" in heterogeneous computing environments for a long time. We present winbind , a component of the Samba suite of programs as a solution to the unied logon problem. Winbind uses a UNIX implementation of Microsoft RPC calls, Pluggable Authentication Modules, and the Name Service Switch to allow Windows NT domain users to appear and operate as UNIX users on a UNIX machine. This paper describes the winbind system, explaining the functionality it provides, how it is configured, and how it works internally.

7.2. Introduction

It is well known that UNIX and Microsoft Windows NT have different models for representing user and group information and use different technologies for implementing them. This fact has made it difficult to integrate the two systems in a satisfactory manner.

One common solution in use today has been to create identically named user accounts on both the UNIX and Windows systems and use the Samba suite of programs to provide file and print services between the two. This solution is far from perfect however, as adding and deleting users on both sets of machines becomes a chore and two sets of passwords are required both of which which can lead to synchronization problems between the UNIX and Windows systems and confusion for users.

We divide the unifed logon problem for UNIX machines into three smaller problems:

• Obtaining Windows NT user and group information

• Authenticating Windows NT users

• Password changing for Windows NT users

Ideally, a prospective solution to the unified logon problem would satisfy all the above components without duplication of information on the UNIX machines and without creating additional tasks for the system administrator when maintaining users and groups on either system. The winbind system provides a simple and elegant solution to all three components of the unifed logon problem.

7.3. What Winbind Provides

Winbind unifies UNIX and Windows NT account management by allowing a UNIX box to become a full member of a NT domain. Once this is done the UNIX box will see NT users and groups as if they were native UNIX users and groups, allowing the NT domain to be used in much the same manner that NIS+ is used within UNIX-only environments.

The end result is that whenever any program on the UNIX machine asks the operating system to lookup a user or group name, the query will be resolved by asking the NT domain controller for the specied domain to do the lookup. Because Winbind hooks into the operating system at a low level (via the NSS name resolution modules in the C library) this redirection to the NT domain controller is completely transparent.

Users on the UNIX machine can then use NT user and group names as they would use "native" UNIX names. They can chown files so that they are owned by NT domain users or even login to the UNIX machine and run a UNIX X-Window session as a domain user.

The only obvious indication that Winbind is being used is that user and group names take the form DOMAIN\user and DOMAIN\group. This is necessary as it allows Winbind to determine that redirection to a domain controller is wanted for a particular lookup and which trusted domain is being referenced.

Additionally, Winbind provides a authentication service that hooks into the Pluggable Authentication Modules (PAM) system to provide authentication via a NT domain to any PAM enabled applications. This capability solves the problem of synchronizing passwords between systems as all passwords are stored in a single location (on the domain controller).

7.4. How Winbind Works

The winbind system is designed around a client/server architecture. A long running winbindd daemon listens on a UNIX domain socket waiting for requests to arrive. These requests are generated by the NSS and PAM clients and processed sequentially.

The technologies used to implement winbind are described in detail below.

7.5. Installation and Configuration

The easiest way to install winbind is by using the packages provided in the pub/samba/appliance/ directory on your nearest Samba mirror. These packages provide snapshots of the Samba source code and binaries already setup to provide the full functionality of winbind. This setup is a little more complex than a normal Samba build as winbind needs a small amount of functionality from a development code branch called SAMBA_TNG.

Once you have installed the packages you should read the winbindd(8) man page which will provide you with conguration information and give you sample conguration files. You may also wish to update the main Samba daemons smbd and nmbd) with a more recent development release, such as the recently announced Samba 2.2 alpha release.

7.6. Limitations

Winbind has a number of limitations in its current released version which we hope to overcome in future releases:

• Winbind is currently only available for the Linux operating system, although ports to other operating systems are certainly possible. For such ports to be feasible, we require the C library of the target operating system to support the Name Service Switch and Pluggable Authentication Modules systems. This is becoming more common as NSS and PAM gain support among UNIX vendors.

• The mappings of Windows NT RIDs to UNIX ids is not made algorithmically and depends on the order in which unmapped users or groups are seen by winbind. It may be difficult to recover the mappings of rid to UNIX id mapping if the file containing this information is corrupted or destroyed.

• Currently the winbind PAM module does not take into account possible workstation and logon time restrictions that may be been set for Windows NT users.

• Building winbind from source is currently quite tedious as it requires combining source code from two Samba branches. Work is underway to solve this by providing all the necessary functionality in the main Samba code branch.

7.7. Conclusion

The winbind system, through the use of the Name Service Switch, Pluggable Authentication Modules, and appropriate Microsoft RPC calls have allowed us to provide seamless integration of Microsoft Windows NT domain users on a UNIX system. The result is a great reduction in the administrative cost of running a mixed UNIX and NT network.

8.1. Viewing and changing UNIX permissions using the NT security dialogs

New in the Samba 2.0.4 release is the ability for Windows NT clients to use their native security settings dialog box to view and modify the underlying UNIX permissions.

Note that this ability is careful not to compromise the security of the UNIX host Samba is running on, and still obeys all the file permission rules that a Samba administrator can set.

In Samba 2.0.4 and above the default value of the parameter nt acl support has been changed from false to true, so manipulation of permissions is turned on by default.

8.2. How to view file security on a Samba share

From an NT 4.0 client, single-click with the right mouse button on any file or directory in a Samba mounted drive letter or UNC path. When the menu pops-up, click on the Properties entry at the bottom of the menu. This brings up the normal file properties dialog box, but with Samba 2.0.4 this will have a new tab along the top marked Security. Click on this tab and you will see three buttons, Permissions, Auditing, and Ownership. The Auditing button will cause either an error message A requested privilege is not held by the client to appear if the user is not the NT Administrator, or a dialog which is intended to allow an Administrator to add auditing requirements to a file if the user is logged on as the NT Administrator. This dialog is non-functional with a Samba share at this time, as the only useful button, the Add button will not currently allow a list of users to be seen.

8.3. Viewing file ownership

Clicking on the "Ownership" button brings up a dialog box telling you who owns the given file. The owner name will be of the form :

"SERVER\user (Long name)"

Where SERVER is the NetBIOS name of the Samba server, user is the user name of the UNIX user who owns the file, and (Long name) is the discriptive string identifying the user (normally found in the GECOS field of the UNIX password database). Click on the Close button to remove this dialog.

If the parameter nt acl support is set to false then the file owner will be shown as the NT user "Everyone".

The Take Ownership button will not allow you to change the ownership of this file to yourself (clicking on it will display a dialog box complaining that the user you are currently logged onto the NT client cannot be found). The reason for this is that changing the ownership of a file is a privilaged operation in UNIX, available only to the root user. As clicking on this button causes NT to attempt to change the ownership of a file to the current user logged into the NT client this will not work with Samba at this time.

There is an NT chown command that will work with Samba and allow a user with Administrator privillage connected to a Samba 2.0.4 server as root to change the ownership of files on both a local NTFS filesystem or remote mounted NTFS or Samba drive. This is available as part of the Seclib NT security library written by Jeremy Allison of the Samba Team, available from the main Samba ftp site.

8.4. Viewing file or directory permissions

The third button is the "Permissions" button. Clicking on this brings up a dialog box that shows both the permissions and the UNIX owner of the file or directory. The owner is displayed in the form :

"SERVER\user (Long name)"

Where SERVER is the NetBIOS name of the Samba server, user is the user name of the UNIX user who owns the file, and (Long name) is the discriptive string identifying the user (normally found in the GECOS field of the UNIX password database).

If the parameter nt acl support is set to false then the file owner will be shown as the NT user "Everyone" and the permissions will be shown as NT "Full Control".

The permissions field is displayed differently for files and directories, so I'll describe the way file permissions are displayed first.

8.5. Modifying file or directory permissions

Modifying file and directory permissions is as simple as changing the displayed permissions in the dialog box, and clicking the OK button. However, there are limitations that a user needs to be aware of, and also interactions with the standard Samba permission masks and mapping of DOS attributes that need to also be taken into account.

If the parameter nt acl support is set to false then any attempt to set security permissions will fail with an "Access Denied" message.

The first thing to note is that the "Add" button will not return a list of users in Samba 2.0.4 (it will give an error message of "The remote proceedure call failed and did not execute"). This means that you can only manipulate the current user/group/world permissions listed in the dialog box. This actually works quite well as these are the only permissions that UNIX actually has.

If a permission triple (either user, group, or world) is removed from the list of permissions in the NT dialog box, then when the "OK" button is pressed it will be applied as "no permissions" on the UNIX side. If you then view the permissions again the "no permissions" entry will appear as the NT "O" flag, as described above. This allows you to add permissions back to a file or directory once you have removed them from a triple component.

As UNIX supports only the "r", "w" and "x" bits of an NT ACL then if other NT security attributes such as "Delete access" are selected then they will be ignored when applied on the Samba server.

When setting permissions on a directory the second set of permissions (in the second set of parentheses) is by default applied to all files within that directory. If this is not what you want you must uncheck the "Replace permissions on existing files" checkbox in the NT dialog before clicking "OK".

If you wish to remove all permissions from a user/group/world component then you may either highlight the component and click the "Remove" button, or set the component to only have the special "Take Ownership" permission (dsplayed as "O" ) highlighted.

8.6. Interaction with the standard Samba create mask parameters

Note that with Samba 2.0.5 there are four new parameters to control this interaction. These are :

security mask

force security mode

directory security mask

force directory security mode

Once a user clicks "OK" to apply the permissions Samba maps the given permissions into a user/group/world r/w/x triple set, and then will check the changed permissions for a file against the bits set in the security mask parameter. Any bits that were changed that are not set to '1' in this parameter are left alone in the file permissions.

Essentially, zero bits in the security mask mask may be treated as a set of bits the user is not allowed to change, and one bits are those the user is allowed to change.

If not set explicitly this parameter is set to the same value as the create mask parameter to provide compatibility with Samba 2.0.4 where this permission change facility was introduced. To allow a user to modify all the user/group/world permissions on a file, set this parameter to 0777.

Next Samba checks the changed permissions for a file against the bits set in the force security mode parameter. Any bits that were changed that correspond to bits set to '1' in this parameter are forced to be set.

Essentially, bits set in the force security mode parameter may be treated as a set of bits that, when modifying security on a file, the user has always set to be 'on'.

If not set explicitly this parameter is set to the same value as the force create mode parameter to provide compatibility with Samba 2.0.4 where the permission change facility was introduced. To allow a user to modify all the user/group/world permissions on a file, with no restrictions set this parameter to 000.

The security mask and force security mode parameters are applied to the change request in that order.

For a directory Samba will perform the same operations as described above for a file except using the parameter directory security mask instead of security mask, and force directory security mode parameter instead of force security mode .

The directory security mask parameter by default is set to the same value as the directory mask parameter and the force directory security mode parameter by default is set to the same value as the force directory mode parameter to provide compatibility with Samba 2.0.4 where the permission change facility was introduced.

In this way Samba enforces the permission restrictions that an administrator can set on a Samba share, whilst still allowing users to modify the permission bits within that restriction.

If you want to set up a share that allows users full control in modifying the permission bits on their files and directories and doesn't force any particular bits to be set 'on', then set the following parameters in the smb.conf(5) file in that share specific section :

security mask = 0777

force security mode = 0

directory security mask = 0777

force directory security mode = 0

As described, in Samba 2.0.4 the parameters :

create mask

force create mode

directory mask

force directory mode

were used instead of the parameters discussed here.

8.7. Interaction with the standard Samba file attribute mapping

Samba maps some of the DOS attribute bits (such as "read only") into the UNIX permissions of a file. This means there can be a conflict between the permission bits set via the security dialog and the permission bits set by the file attribute mapping.

One way this can show up is if a file has no UNIX read access for the owner it will show up as "read only" in the standard file attributes tabbed dialog. Unfortunately this dialog is the same one that contains the security info in another tab.

What this can mean is that if the owner changes the permissions to allow themselves read access using the security dialog, clicks "OK" to get back to the standard attributes tab dialog, and then clicks "OK" on that dialog, then NT will set the file permissions back to read-only (as that is what the attributes still say in the dialog). This means that after setting permissions and clicking "OK" to get back to the attributes dialog you should always hit "Cancel" rather than "OK" to ensure that your changes are not overridden.

9.1. FAQs

10.1. Introduction

Samba is developed in an open environnment. Developers use CVS (Concurrent Versioning System) to "checkin" (also known as "commit") new source code. Samba's various CVS branches can be accessed via anonymouns CVS using the instructions detailed in this chapter.

This document is a modified version of the instructions found at http://samba.org/samba/cvs.html

10.2. CVS Access to samba.org

The machine samba.org runs a publicly accessible CVS repository for access to the source code of several packages, including samba, rsync and jitterbug. There are two main ways of accessing the CVS server on this host.