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diff --git a/docs/docbook/projdoc/ServerType.xml b/docs/docbook/projdoc/ServerType.xml deleted file mode 100644 index f400cdd647..0000000000 --- a/docs/docbook/projdoc/ServerType.xml +++ /dev/null @@ -1,646 +0,0 @@ -<chapter id="ServerType"> -<chapterinfo> - &author.tridge; - &author.jelmer; - &author.jht; -</chapterinfo> - -<title>Server Types and Security Modes</title> - -<para> -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 -use Samba will want to know the meaning, within a Samba context, of terms familiar to MS Windows -administrator. This means that it is essential also to define how critical security -modes function before we get into the details of how to configure the server itself. -</para> - -<para> -The chapter provides an overview of the security modes of which Samba is capable -and how they relate to MS Windows servers and clients. -</para> - -<para> -A question often asked is, <quote>Why would I want to use Samba?</quote> Most chapters contain a section -that highlights features and benefits. We hope that the information provided will help to -answer this question. Be warned though, we want to be fair and reasonable, so not all -features are positive towards Samba. The benefit may be on the side of our competition. -</para> - -<sect1> -<title>Features and Benefits</title> - -<para> -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 befitting his anguish. The other looked at the stone and said, <quote>This is a garnet. -I can turn that into a precious gem and some day it will make a princess very happy!</quote> -</para> - -<para> -The moral of this tale: Two men, two very different perspectives regarding the same stone. -Like it or not, Samba is like that stone. Treat it the right way and it can bring great -pleasure, but if you are forced to use it and have no time for its secrets, then it can be -a source of discomfort. -</para> - -<para> -Samba started out as a project that sought to provide interoperability for MS Windows 3.x -clients with a UNIX server. It has grown up a lot since its humble beginnings and now provides -features and functionality fit for large scale deployment. It also has some warts. In sections -like this one we tell of both. -</para> - -<para> -So, what are the benefits of features mentioned in this chapter? -</para> - -<itemizedlist> - <listitem><para> - Samba-3 can replace an MS Windows NT4 Domain Controller. - </para></listitem> - - <listitem><para> - Samba-3 offers excellent interoperability with MS Windows NT4-style - domains as well as natively with Microsoft Active Directory domains. - </para></listitem> - - <listitem><para> - Samba-3 permits full NT4-style Interdomain Trusts. - </para></listitem> - - <listitem><para> - Samba has security modes that permit more flexible - authentication than is possible with MS Windows NT4 Domain Controllers. - </para></listitem> - - <listitem><para> - Samba-3 permits use of multiple account database backends. - </para></listitem> - - <listitem><para> - The account (password) database backends can be distributed - and replicated using multiple methods. This gives Samba-3 - greater flexibility than MS Windows NT4 and in many cases a - significantly higher utility than Active Directory domains - with MS Windows 200x. - </para></listitem> -</itemizedlist> - -</sect1> - -<sect1> -<title>Server Types</title> - - -<para> -<indexterm><primary>Server Type</primary></indexterm> -Administrators of Microsoft networks often refer to three -different type of servers:</para> - -<itemizedlist> - <listitem><para>Domain Controller</para> - <itemizedlist> - <listitem><para>Primary Domain Controller</para></listitem> - <listitem><para>Backup Domain Controller</para></listitem> - <listitem><para>ADS Domain Controller</para></listitem> - </itemizedlist> - </listitem> - <listitem><para>Domain Member Server</para> - <itemizedlist> - <listitem><para>Active Directory Domain Server</para></listitem> - <listitem><para>NT4 Style Domain Domain Server</para></listitem> - </itemizedlist> - </listitem> - <listitem><para>Stand-alone Server</para></listitem> -</itemizedlist> - -<para> -The chapters covering Domain Control, Backup Domain Control and Domain Membership provide -pertinent information regarding Samba configuration for each of these server roles. -The reader is strongly encouraged to become intimately familiar with the information -presented. -</para> - -</sect1> - -<sect1> -<title>Samba Security Modes</title> - - -<para> -<indexterm><primary>Security Mode</primary></indexterm> -<indexterm><primary>security</primary></indexterm> -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 -reduce user complaints and administrator heartache. -</para> - -<para> -In the SMB/CIFS networking world, there are only two types of security: <emphasis>User Level</emphasis> -and <emphasis>Share Level</emphasis>. We refer to these collectively as <emphasis>security levels</emphasis>. -In implementing these two security levels, Samba provides flexibilities -that are not available with Microsoft Windows NT4/200x servers. In actual fact, Samba implements -<emphasis>Share Level</emphasis> security only one way, but has four ways of implementing -<emphasis>User Level</emphasis> security. Collectively, we call the Samba implementations -<emphasis>Security Modes</emphasis>. They are known as: <emphasis>SHARE</emphasis>, <emphasis>USER</emphasis>, -<emphasis>DOMAIN</emphasis>, <emphasis>ADS</emphasis>, and <emphasis>SERVER</emphasis> modes. -They are documented in this chapter. -</para> - -<para> -An SMB server tells the client at startup what security level it is running. There are two options: -Share Level and User Level. Which of these two the client receives affects the way the client then -tries to authenticate itself. It does not directly affect (to any great extent) the way the Samba -server does security. This may sound strange, 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. -</para> - -<sect2> -<title>User Level Security</title> - -<para> -We will describe User Level Security first, as its simpler. -In User Level Security, the client will send a -session setup request directly following protocol negotiation. -This request provides a username and password. The server can either accept or reject that -username/password combination. At this stage the server has no idea what -share the client will eventually try to connect to, so it can't base the -<emphasis>accept/reject</emphasis> on anything other than: -</para> - -<orderedlist> -<listitem><para>the username/password.</para></listitem> -<listitem><para>the name of the client machine.</para></listitem> -</orderedlist> - -<para> -If the server accepts the username/password then the client expects to be able to -mount shares (using a <emphasis>tree connection</emphasis>) without specifying a -password. It expects that all access rights will be as the username/password -specified in the <emphasis>session setup</emphasis>. -</para> - -<para> -It is also possible for a client to send multiple <emphasis>session setup</emphasis> -requests. When the server responds, it gives the client a <emphasis>uid</emphasis> 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). -</para> - -<sect3> -<title>Example Configuration</title> - -<para> -The &smb.conf; parameter that sets user level security is: -</para> - -<para><smbconfblock> -<smbconfoption><name>security</name><value>user</value></smbconfoption> -</smbconfblock></para> - -<para> -This is the default setting since Samba-2.2.x. -</para> - -</sect3> - -</sect2> -<sect2> -<title>Share Level Security</title> - -<para> -In Share Level security, the client authenticates -itself separately for each share. It sends a password along with each -tree connection (share mount). It does not explicitly send a -username with this operation. The client expects a password to be associated -with each share, independent of the user. This means that Samba has to work out what -username the client probably wants to use. It is never explicitly sent the username. -Some commercial SMB servers such as NT actually associate passwords directly with -shares in Share Level security, but Samba always uses the UNIX authentication scheme -where it is a username/password pair that is authenticated, not a share/password pair. -</para> - -<para> -To understand the MS Windows networking parallels, one should think -in terms of MS Windows 9x/Me where one can create a shared folder that provides read-only -or full access, with or without a password. -</para> - -<para> -Many clients send a session setup even if the server is in Share Level security. They -normally send a valid username but no password. Samba records this username in a list -of possible usernames. When the client then does a tree connection it also adds to this list the name -of the share they try to connect to (useful for home directories) and any users -listed in the <smbconfoption><name>user</name></smbconfoption> parameter in the &smb.conf; file. -The password is then checked in turn against these possible usernames. If a match is found -then the client is authenticated as that user. -</para> - -<sect3> -<title>Example Configuration</title> - -<para> -The &smb.conf; parameter that sets Share Level security is: -</para> - -<para><smbconfblock> -<smbconfoption><name>security</name><value>share</value></smbconfoption> -</smbconfblock></para> - -<para> -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. -</para> - -</sect3> -</sect2> - -<sect2> -<title>Domain Security Mode (User Level Security)</title> - -<para> -<indexterm><primary>Domain Member</primary></indexterm> -When Samba is operating in <smbconfoption><name>security</name><value>domain</value></smbconfoption> mode, -the Samba server has a domain security trust account (a machine account) and causes -all authentication requests to be passed through to the Domain Controllers. -In other words, this configuration makes the Samba server a Domain Member server. -</para> - -<sect3> -<title>Example Configuration</title> -<para><emphasis> -Samba as a Domain Member Server -</emphasis></para> - - -<para> -<indexterm><primary>Server Type</primary><secondary>Domain Member</secondary></indexterm> -This method involves addition of the following parameters in the &smb.conf; file: -</para> - -<para><smbconfblock> -<smbconfoption><name>security</name><value>domain</value></smbconfoption> -<smbconfoption><name>workgroup</name><value>&example.workgroup;</value></smbconfoption> -</smbconfblock></para> - -<para> -In order for this method to work, the Samba server needs to join the MS Windows NT -security domain. This is done as follows: -<indexterm><primary>net</primary><secondary>rpc</secondary></indexterm> -<indexterm><primary>Domain Member</primary><secondary>joining</secondary></indexterm> -</para> - - -<procedure> - <step><para>On the MS Windows NT Domain Controller, using - the Server Manager, add a machine account for the Samba server. - </para></step> - - <step><para>On the UNIX/Linux system execute:</para> - - <para><screen>&rootprompt;<userinput>net rpc join -U administrator%password</userinput></screen></para> - </step> -</procedure> - -<note><para> -Samba-2.2.4 and later can auto-join a Windows NT4-style Domain just by executing: -<screen> -&rootprompt;<userinput>smbpasswd -j <replaceable>DOMAIN_NAME</replaceable> -r <replaceable>PDC_NAME</replaceable> \ - -U Administrator%<replaceable>password</replaceable></userinput> -</screen> - -Samba-3 can do the same by executing: -<screen> -&rootprompt;<userinput>net rpc join -U Administrator%<replaceable>password</replaceable></userinput> -</screen> -It is not necessary with Samba-3 to specify the <replaceable>DOMAIN_NAME</replaceable> or the -<replaceable>PDC_NAME</replaceable> as it figures this out from the &smb.conf; file settings. -</para></note> - -<para> -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 -the remote Windows DC. This account can be blocked to prevent logons by clients other than -MS Windows through means such as setting an invalid shell in the -<filename>/etc/passwd</filename> entry. -</para> - -<para> -An alternative to assigning UIDs to Windows users on a Samba member server is -presented in <link linkend="winbind"></link>. -</para> - -<para> -For more information regarding Domain Membership, see <link linkend="domain-member"></link>. -</para> - -</sect3> -</sect2> - -<sect2> -<title>ADS Security Mode (User Level Security)</title> - -<para> -Both Samba-2.2, and Samba-3 can join an Active Directory domain. This is -possible if the domain is run in native mode. Active Directory in -native mode perfectly allows NT4-style Domain Members. This is contrary to -popular belief. Active Directory in native mode prohibits only the use of -Backup Domain Controllers running MS Windows NT4. -</para> - -<para> -If you are using Active Directory, starting with Samba-3 you can -join as a native AD member. Why would you want to do that? -Your security policy might prohibit the use of NT-compatible -authentication protocols. All your machines are running Windows 2000 -and above and all use Kerberos. In this case Samba as an NT4-style -domain would still require NT-compatible authentication data. Samba in -AD-member mode can accept Kerberos tickets. -</para> - -<sect3> -<title>Example Configuration</title> - -<para><smbconfblock> -<smbconfoption><name>realm</name><value>your.kerberos.REALM</value></smbconfoption> -<smbconfoption><name>security</name><value>ADS</value></smbconfoption> -</smbconfblock></para> - -<para> -The following parameter may be required: -</para> - -<para><smbconfblock> -<smbconfoption><name>password server</name><value>your.kerberos.server</value></smbconfoption> -</smbconfblock></para> - -<para> -Please refer to <link linkend="domain-member"></link> and <link linkend="ads-member"></link> -for more information regarding this configuration option. -</para> - -</sect3> -</sect2> - -<sect2> -<title>Server Security (User Level Security)</title> - -<para> -Server Security Mode is 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 drawbacks that include: -</para> - -<itemizedlist> - <listitem><para>Potential Account Lockout on MS Windows NT4/200x password servers.</para></listitem> - <listitem><para>Lack of assurance that the password server is the one specified.</para></listitem> - <listitem><para>Does not work with Winbind, which is particularly needed when storing profiles remotely.</para></listitem> - <listitem><para>This mode may open connections to the password server, and keep them open for extended periods.</para></listitem> - <listitem><para>Security on the Samba server breaks badly when the remote password server suddenly shuts down.</para></listitem> - <listitem><para>With this mode there is NO security account in the domain that the password server belongs to for the Samba server.</para></listitem> -</itemizedlist> - -<para> -In Server Security Mode the Samba server reports to the client that it is in User Level -security. The client then does a session setup as described earlier. -The Samba server takes the username/password that the client sends and attempts to login to the -<smbconfoption><name>password server</name></smbconfoption> by sending exactly the same username/password that -it got from the client. If that server is in User Level Security and accepts the password, -then Samba accepts the client's connection. This allows the Samba server to use another SMB -server as the <smbconfoption><name>password server</name></smbconfoption>. -</para> - -<para> -You should also note that at the start of all this where the server tells the client -what security level it is in, it also tells the client if it supports encryption. If it -does, it supplies the client with a random cryptkey. The client will then send all -passwords in encrypted form. Samba supports this type of encryption by default. -</para> - -<para> -The parameter <smbconfoption><name>security</name><value>server</value></smbconfoption> means that Samba reports to clients that -it is running in <emphasis>user mode</emphasis> but actually passes off all authentication -requests to another <emphasis>user mode</emphasis> server. This requires an additional -parameter <smbconfoption><name>password server</name></smbconfoption> that points to the real authentication server. -The real authentication server can be another Samba server, or it can be a Windows NT server, -the latter being natively capable of encrypted password support. -</para> - -<note><para> -When Samba is running in <emphasis>Server Security Mode</emphasis> it is essential that -the parameter <emphasis>password server</emphasis> is set to the precise NetBIOS machine -name of the target authentication server. Samba cannot determine this from NetBIOS name -lookups because the choice of the target authentication server is arbitrary and cannot -be determined from a domain name. In essence, a Samba server that is in -<emphasis>Server Security Mode</emphasis> is operating in what used to be known as -workgroup mode. -</para></note> - -<sect3> -<title>Example Configuration</title> -<para><emphasis> -Using MS Windows NT as an Authentication Server -</emphasis></para> - -<para> -This method involves the additions of the following parameters in the &smb.conf; file: -</para> - -<para><smbconfblock> -<smbconfoption><name>encrypt passwords</name><value>Yes</value></smbconfoption> -<smbconfoption><name>security</name><value>server</value></smbconfoption> -<smbconfoption><name>password server</name><value>"NetBIOS_name_of_a_DC"</value></smbconfoption> -</smbconfblock></para> - - -<para> -There are two ways of identifying whether or not a username and password pair is valid. -One uses the reply information provided as part of the authentication messaging -process, the other uses just an error code. -</para> - -<para> -The downside of this mode of configuration is the fact that for security reasons Samba -will send the password server a bogus username and a bogus password and if the remote -server fails to reject the username and password pair then an alternative mode of -identification of validation is used. Where a site uses password lock out after a -certain number of failed authentication attempts this will result in user lockouts. -</para> - -<para> -Use of this mode of authentication requires a standard UNIX account for the user. -This account can be blocked to prevent logons by non-SMB/CIFS clients. -</para> - -</sect3> -</sect2> - -</sect1> - -<sect1> -<title>Password Checking</title> - -<para> -MS Windows clients may use encrypted passwords as part of a challenge/response -authentication model (a.k.a. NTLMv1 and NTLMv2) or alone, or cleartext strings for simple -password-based authentication. It should be realized that with the SMB protocol, -the password is passed over the network either in plain-text or encrypted, but -not both in the same authentication request. -</para> - -<para> -When encrypted passwords are used, a password that has been entered by the user -is encrypted in two ways: -</para> - -<itemizedlist> - <listitem><para>An MD4 hash of the unicode of the password - string. This is known as the NT hash. - </para></listitem> - - <listitem><para>The password is converted to upper case, - and then padded or truncated to 14 bytes. This string is - then appended with 5 bytes of NULL characters and split to - form two 56-bit DES keys to encrypt a <quote>magic</quote> 8-byte value. - The resulting 16 bytes form the LanMan hash. - </para></listitem> -</itemizedlist> - -<para> -MS Windows 95 pre-service pack 1, MS Windows NT versions 3.x and version 4.0 -pre-service pack 3 will use either mode of password authentication. All -versions of MS Windows that follow these versions no longer support plain -text passwords by default. -</para> - -<para> -MS Windows clients have a habit of dropping network mappings that have been idle -for 10 minutes or longer. When the user attempts to use the mapped drive -connection that has been dropped, the client re-establishes the connection using -a cached copy of the password. -</para> - -<para> -When Microsoft changed the default password mode, support was dropped for caching -of the plain-text password. This means that when the registry parameter is changed -to re-enable use of plain-text passwords it appears to work, but when a dropped -service connection mapping attempts to revalidate, this will fail if the remote -authentication server does not support encrypted passwords. It is definitely not -a good idea to re-enable plain-text password support in such clients. -</para> - -<para> -The following parameters can be used to work around the issue of Windows 9x/Me clients -upper-casing usernames and passwords before transmitting them to the SMB server -when using cleartext authentication: -</para> - -<para><smbconfblock> -<smbconfoption><name>password level</name><value><replaceable>integer</replaceable></value></smbconfoption> -<smbconfoption><name>username level</name><value><replaceable>integer</replaceable></value></smbconfoption> -</smbconfblock></para> - -<para> -By default Samba will convert to lower case the username before attempting to lookup the user -in the database of local system accounts. Because UNIX usernames conventionally -only contain lower-case characters, the <smbconfoption><name>username level</name></smbconfoption> parameter -is rarely needed. -</para> - -<para> -However, passwords on UNIX systems often make use of mixed-case characters. -This means that in order for a user on a Windows 9x/Me client to connect to a Samba -server using cleartext authentication, the <smbconfoption><name>password level</name></smbconfoption> -must be set to the maximum number of upper case letters that <emphasis>could</emphasis> -appear in a password. Note that if the server OS uses the traditional DES version -of crypt(), a <smbconfoption><name>password level</name></smbconfoption> of 8 will result in case -insensitive passwords as seen from Windows users. This will also result in longer -login times as Samba has to compute the permutations of the password string and -try them one by one until a match is located (or all combinations fail). -</para> - -<para> -The best option to adopt is to enable support for encrypted passwords wherever -Samba is used. Most attempts to apply the registry change to re-enable plain-text -passwords will eventually lead to user complaints and unhappiness. -</para> - -</sect1> - -<sect1> -<title>Common Errors</title> - -<para> -We all make mistakes. It is okay to make mistakes, as long as they are made in the right places -and at the right time. A mistake that causes lost productivity is seldom tolerated, however a mistake -made in a developmental test lab is expected. -</para> - -<para> -Here we look at common mistakes and misapprehensions that have been the subject of discussions -on the Samba mailing lists. Many of these are avoidable by doing your homework before attempting -a Samba implementation. Some are the result of a misunderstanding of the English language. The -English language, which has many phrases that are potentially vague and may be highly confusing -to those for whom English is not their native tongue. -</para> - -<sect2> -<title>What Makes Samba a Server?</title> - -<para> -To some the nature of the Samba <emphasis>security</emphasis> mode is obvious, but entirely -wrong all the same. It is assumed that <smbconfoption><name>security</name><value>server</value></smbconfoption> means that Samba -will act as a server. Not so! This setting means that Samba will <emphasis>try</emphasis> -to use another SMB server as its source for user authentication alone. -</para> - -</sect2> - -<sect2> -<title>What Makes Samba a Domain Controller?</title> - -<para> -The &smb.conf; parameter <smbconfoption><name>security</name><value>domain</value></smbconfoption> does not really make Samba behave -as a Domain Controller. This setting means we want Samba to be a Domain Member. -</para> - -</sect2> - -<sect2> -<title>What Makes Samba a Domain Member?</title> - -<para> -Guess! So many others do. But whatever you do, do not think that <smbconfoption><name>security</name><value>user</value></smbconfoption> -makes Samba act as a Domain Member. Read the manufacturer's manual before the warranty expires. See -<link linkend="domain-member"></link> for more information. -</para> - -</sect2> - - -<sect2> -<title>Constantly Losing Connections to Password Server</title> - -<para> - <quote> -Why does server_validate() simply give up rather than re-establish its connection to the -password server? Though I am not fluent in the SMB protocol, perhaps the cluster server -process passes along to its client workstation the session key it receives from the password -server, which means the password hashes submitted by the client would not work on a subsequent -connection whose session key would be different. So server_validate() must give up.</quote> -</para> - -<para> -Indeed. That's why <smbconfoption><name>security</name><value>server</value></smbconfoption> -is at best a nasty hack. Please use <smbconfoption><name>security</name><value>domain</value></smbconfoption>; -<smbconfoption><name>security</name><value>server</value></smbconfoption> mode is also known as pass-through authentication. -</para> - -</sect2> - -</sect1> - -</chapter> |