Chapter 25. PAM based Distributed Authentication

John H. Terpstra

Samba Team

<jht@samba.org>

Stephen Langasek

<vorlon@netexpress.net>

May 31, 2003

Table of Contents

Features and Benefits

Technical Discussion

PAM Configuration Syntax
Example System Configurations
smb.conf PAM Configuration
Remote CIFS Authentication using winbindd.so
Password Synchronization using pam_smbpass.so

Common Errors

pam_winbind problem
Winbind is not resolving users and groups

-This chapter you should help you to deploy winbind based authentication on any PAM enabled -UNIX/Linux system. Winbind can be used to enable user level application access authentication -from any MS Windows NT Domain, MS Windows 200x Active Directory based domain, or any Samba -based domain environment. It will also help you to configure PAM based local host access +Chapter 25. PAM-Based Distributed Authentication

Chapter 25. PAM-Based Distributed Authentication
Prev	Part III. Advanced Configuration	Next

Chapter 25. PAM-Based Distributed Authentication

John H. Terpstra

Samba Team

<jht@samba.org>

Stephen Langasek

<vorlon@netexpress.net>

May 31, 2003

Table of Contents

Features and Benefits

Technical Discussion

PAM Configuration Syntax
Example System Configurations
smb.conf PAM Configuration
Remote CIFS Authentication Using winbindd.so
Password Synchronization Using pam_smbpass.so

Common Errors

pam_winbind Problem
Winbind Is Not Resolving Users and Groups

+This chapter should help you to deploy Winbind-based authentication on any PAM-enabled +UNIX/Linux system. Winbind can be used to enable User-Level application access authentication +from any MS Windows NT Domain, MS Windows 200x Active Directory-based +domain, or any Samba-based domain environment. It will also help you to configure PAM-based local host access controls that are appropriate to your Samba configuration.

-In addition to knowing how to configure winbind into PAM, you will learn generic PAM management -possibilities and in particular how to deploy tools like pam_smbpass.so to your advantage. +In addition to knowing how to configure Winbind into PAM, you will learn generic PAM management +possibilities and in particular how to deploy tools like pam_smbpass.so to your advantage.

Note

-The use of Winbind require more than PAM configuration alone. Please refer to the Winbind chapter. -

Features and Benefits

-A number of UNIX systems (eg: Sun Solaris), as well as the xxxxBSD family and Linux, +The use of Winbind requires more than PAM configuration alone. +Please refer to , for further information regarding Winbind. +

Features and Benefits

+A number of UNIX systems (e.g., Sun Solaris), as well as the xxxxBSD family and Linux, now utilize the Pluggable Authentication Modules (PAM) facility to provide all authentication, authorization and resource control services. Prior to the introduction of PAM, a decision to use an alternative to the system password database (/etc/passwd) would require the provision of alternatives for all programs that provide security services. -Such a choice would involve provision of alternatives to such programs as: login, -passwd, chown, etc. +Such a choice would involve provision of alternatives to programs such as: login, +passwd, chown, and so on.

PAM provides a mechanism that disconnects these security programs from the underlying -authentication/authorization infrastructure. PAM is configured either through one file -/etc/pam.conf (Solaris), or by editing individual files that are +authentication/authorization infrastructure. PAM is configured by making appropriate modifications to one file +/etc/pam.conf (Solaris), or by editing individual control files that are located in /etc/pam.d.

-On PAM enabled UNIX/Linux systems it is an easy matter to configure the system to use any -authentication backend, so long as the appropriate dynamically loadable library modules -are available for it. The backend may be local to the system, or may be centralised on a +On PAM-enabled UNIX/Linux systems, it is an easy matter to configure the system to use any +authentication backend so long as the appropriate dynamically loadable library modules +are available for it. The backend may be local to the system, or may be centralized on a remote server.

PAM support modules are available for: -

/etc/passwd:

/etc/passwd: There are several PAM modules that interact with this standard UNIX user - database. The most common are called: pam_unix.so, pam_unix2.so, pam_pwdb.so - and pam_userdb.so. -
Kerberos:: - The pam_krb5.so module allows the use of any Kerberos compliant server. + database. The most common are called: pam_unix.so, pam_unix2.so, pam_pwdb.so + and pam_userdb.so. +
Kerberos: + The pam_krb5.so module allows the use of any Kerberos compliant server. This tool is used to access MIT Kerberos, Heimdal Kerberos, and potentially Microsoft Active Directory (if enabled). -
LDAP:: - The pam_ldap.so module allows the use of any LDAP v2 or v3 compatible backend +
LDAP: + The pam_ldap.so module allows the use of any LDAP v2 or v3 compatible backend server. Commonly used LDAP backend servers include: OpenLDAP v2.0 and v2.1, Sun ONE iDentity server, Novell eDirectory server, Microsoft Active Directory. -
NetWare Bindery:: - The pam_ncp_auth.so module allows authentication off any bindery enabled - NetWare Core Protocol based server. -
SMB Password:: - This module, called pam_smbpass.so, will allow user authentication off +
NetWare Bindery: + The pam_ncp_auth.so module allows authentication off any bindery-enabled + NetWare Core Protocol-based server. +
SMB Password: + This module, called pam_smbpass.so, will allow user authentication off the passdb backend that is configured in the Samba smb.conf file. -
SMB Server:: - The pam_smb_auth.so module is the original MS Windows networking authentication +
SMB Server: + The pam_smb_auth.so module is the original MS Windows networking authentication tool. This module has been somewhat outdated by the Winbind module. -
Winbind:: - The pam_winbind.so module allows Samba to obtain authentication from any +
Winbind: + The pam_winbind.so module allows Samba to obtain authentication from any MS Windows Domain Controller. It can just as easily be used to authenticate - users for access to any PAM enabled application. -
RADIUS:: + users for access to any PAM-enabled application. +
RADIUS: There is a PAM RADIUS (Remote Access Dial-In User Service) authentication - module. In most cases the administrator will need to locate the source code + module. In most cases, administrators will need to locate the source code for this tool and compile and install it themselves. RADIUS protocols are used by many routers and terminal servers.

-Of the above, Samba provides the pam_smbpasswd.so and the pam_winbind.so modules alone. +Of the above, Samba provides the pam_smbpasswd.so and the pam_winbind.so modules alone.

Once configured, these permit a remarkable level of flexibility in the location and use -of distributed samba domain controllers that can provide wide are network bandwidth -efficient authentication services for PAM capable systems. In effect, this allows the -deployment of centrally managed and maintained distributed authentication from a single -user account database. -

Technical Discussion

+of distributed Samba Domain Controllers that can provide wide area network bandwidth +efficient authentication services for PAM-capable systems. In effect, this allows the +deployment of centrally managed and maintained distributed authentication from a +single-user account database. +

Technical Discussion

PAM is designed to provide the system administrator with a great deal of flexibility in configuration of the privilege granting applications of their system. The local configuration of system security controlled by PAM is contained in one of two places: -either the single system file, /etc/pam.conf; or the /etc/pam.d/ directory. -

PAM Configuration Syntax

+either the single system file, /etc/pam.conf, or the +/etc/pam.d/ directory. +

PAM Configuration Syntax

In this section we discuss the correct syntax of and generic options respected by entries to these files. -PAM specific tokens in the configuration file are case insensitive. The module paths, however, are case -sensitive since they indicate a file's name and reflect the case dependence of typical file-systems. +PAM-specific tokens in the configuration file are case insensitive. The module paths, however, are case +sensitive since they indicate a file's name and reflect the case +dependence of typical file systems. The case-sensitivity of the arguments to any given module is defined for each module in turn.

In addition to the lines described below, there are two special characters provided for the convenience -of the system administrator: comments are preceded by a `#' and extend to the next end-of-line; also, -module specification lines may be extended with a `\' escaped newline. +of the system administrator: comments are preceded by a “#” and extend to the next end-of-line; also, +module specification lines may be extended with a “\” escaped newline.

If the PAM authentication module (loadable link library file) is located in the -default location then it is not necessary to specify the path. In the case of +default location, then it is not necessary to specify the path. In the case of Linux, the default location is /lib/security. If the module -is located outside the default then the path must be specified as: +is located outside the default, then the path must be specified as:

 auth  required  /other_path/pam_strange_module.so

Anatomy of `/etc/pam.d` Entries

The remaining information in this subsection was taken from the documentation of the Linux-PAM project. For more information on PAM, see -The Official Linux-PAM home page +The Official Linux-PAM home page.

-A general configuration line of the /etc/pam.conf file has the following form: +A general configuration line of the /etc/pam.conf file has the following form:

 service-name   module-type   control-flag   module-path   args
@@ -104,36 +107,38 @@ service-name   module-type   control-flag   module-path   args
 Below, we explain the meaning of each of these tokens. The second (and more recently adopted)
 way of configuring Linux-PAM is via the contents of the /etc/pam.d/ directory.
 Once we have explained the meaning of the above tokens, we will describe this method.
-
service-name:

-		The name of the service associated with this entry. Frequently the service name is the conventional
-		name of the given application. For example, `ftpd', `rlogind' and `su', etc. .
+
service-name

+		The name of the service associated with this entry. Frequently, the service name is the conventional
+		name of the given application. For example, ftpd, rlogind and
+		su, and so on.
 		

-		There is a special service-name, reserved for defining a default authentication mechanism. It has
-		the name `OTHER' and may be specified in either lower or upper case characters. Note, when there
-		is a module specified for a named service, the `OTHER' entries are ignored.
-		
module-type:

+		There is a special service-name reserved for defining a default authentication mechanism. It has
+		the name OTHER and may be specified in either lower- or upper-case characters.
+		Note, when there is a module specified for a named service, the OTHER
+		entries are ignored.
+		
module-type

 		One of (currently) four types of module. The four types are as follows:
 		

-			auth: this module type provides two aspects of authenticating the user.
-			Firstly, it establishes that the user is who they claim to be, by instructing the application
+			auth: This module type provides two aspects of authenticating the user.
+			It establishes that the user is who he claims to be by instructing the application
 			to prompt the user for a password or other means of identification. Secondly, the module can
 			grant group membership (independently of the /etc/groups file discussed
 			above) or other privileges through its credential granting properties.
 			

-			account: this module performs non-authentication based account management.
+			account: This module performs non-authentication-based account management.
 			It is typically used to restrict/permit access to a service based on the time of day, currently
 		 	available system resources (maximum number of users) or perhaps the location of the applicant
-			user `root' login only on the console.
+			user “root” login only on the console.
 			

-			session: primarily, this module is associated with doing things that need
-			to be done for the user before/after they can be given service. Such things include the logging
-			of information concerning the opening/closing of some data exchange with a user, mounting
-			directories, etc.
+			session: Primarily, this module is associated with doing things that need
+			to be done for the user before and after they can be given service. Such things include the logging
+			of information concerning the opening and closing of some data exchange with a user, mounting
+			directories, and so on.
 			

-			password: this last module type is required for updating the authentication
-			token associated with the user. Typically, there is one module for each `challenge/response'
-			based authentication (auth) module-type.
-			
control-flag:

+			password: This last module type is required for updating the authentication
+			token associated with the user. Typically, there is one module for each “challenge/response”
+			-based authentication (auth) module type.
+			
control-flag

 		The control-flag is used to indicate how the PAM library will react to the success or failure of the
 		module it is associated with. Since modules can be stacked (modules of the same type execute in series,
 		one after another), the control-flags determine the relative importance of each module. The application
@@ -145,129 +150,135 @@ Once we have explained the meaning of the above tokens, we will describe this me
 		

 		The simpler (and historical) syntax for the control-flag is a single keyword defined to indicate the
 		severity of concern associated with the success or failure of a specific module. There are four such
-		keywords: required, requisite, sufficient and optional.
+		keywords: required, requisite, sufficient and optional.
 		

 		The Linux-PAM library interprets these keywords in the following manner:
 		

-			required: this indicates that the success of the module is required for the
+			required: This indicates that the success of the module is required for the
 			module-type facility to succeed. Failure of this module will not be apparent to the user until all
 			of the remaining modules (of the same module-type) have been executed.
 			

-			requisite: like required, however, in the case that such a module returns a
+			requisite: Like required, however, in the case that such a module returns a
 			failure, control is directly returned to the application. The return value is that associated with
-			the first required or requisite module to fail. Note, this flag can be used to protect against the
+			the first required or requisite module to fail. This flag can be used to protect against the
 			possibility of a user getting the opportunity to enter a password over an unsafe medium. It is
 			conceivable that such behavior might inform an attacker of valid accounts on a system. This
 			possibility should be weighed against the not insignificant concerns of exposing a sensitive
 			password in a hostile environment.
 			

-                        sufficient: the success of this module is deemed `sufficient' to satisfy
+                        sufficient: The success of this module is deemed sufficient to satisfy
 			the Linux-PAM library that this module-type has succeeded in its purpose. In the event that no
-			previous required module has failed, no more `stacked' modules of this type are invoked. (Note,
-			in this case subsequent required modules are not invoked.). A failure of this module is not deemed
+			previous required module has failed, no more “stacked” modules of this type are invoked.
+			(In this case, subsequent required modules are not invoked). A failure of this module is not deemed
 			as fatal to satisfying the application that this module-type has succeeded.
 			

-                        optional: as its name suggests, this control-flag marks the module as not
+                        optional: As its name suggests, this control-flag marks the module as not
 			being critical to the success or failure of the user's application for service. In general,
 			Linux-PAM ignores such a module when determining if the module stack will succeed or fail.
 			However, in the absence of any definite successes or failures of previous or subsequent stacked
-			modules this module will determine the nature of the response to the application. One example of
+			modules, this module will determine the nature of the response to the application. One example of
 			this latter case, is when the other modules return something like PAM_IGNORE.
 			

 		The more elaborate (newer) syntax is much more specific and gives the administrator a great deal of control
 		over how the user is authenticated. This form of the control flag is delimited with square brackets and
-		consists of a series of value=action tokens:
+		consists of a series of value=action tokens:
 		
 [value1=action1 value2=action2 ...]
 

-		Here, value1 is one of the following return values: success; open_err; symbol_err; service_err;
-		system_err; buf_err; perm_denied; auth_err; cred_insufficient; authinfo_unavail; user_unknown; maxtries;
-		new_authtok_reqd; acct_expired; session_err; cred_unavail; cred_expired; cred_err; no_module_data; conv_err;
-		authtok_err; authtok_recover_err; authtok_lock_busy; authtok_disable_aging; try_again; ignore; abort;
-		authtok_expired; module_unknown; bad_item; and default. The last of these (default) can be used to set
-		the action for those return values that are not explicitly defined.
+		Here, value1 is one of the following return values:
+
+success; open_err; symbol_err; service_err; system_err; buf_err;
+perm_denied; auth_err; cred_insufficient; authinfo_unavail;
+user_unknown; maxtries; new_authtok_reqd; acct_expired; session_err;
+cred_unavail; cred_expired; cred_err; no_module_data; conv_err;
+authtok_err; authtok_recover_err; authtok_lock_busy;
+authtok_disable_aging; try_again; ignore; abort; authtok_expired;
+module_unknown; bad_item; and default.
+

+

+		The last of these (default) can be used to set the action for those return values that are not explicitly defined.
 		

-		The action1 can be a positive integer or one of the following tokens: ignore; ok; done; bad; die; and reset.
+		The action1 can be a positive integer or one of the following tokens: 
+		ignore; ok; done; bad; die; and reset.
 		A positive integer, J, when specified as the action, can be used to indicate that the next J modules of the
 		current module-type will be skipped. In this way, the administrator can develop a moderately sophisticated
 		stack of modules with a number of different paths of execution. Which path is taken can be determined by the
 		reactions of individual modules.
 		

-			ignore: when used with a stack of modules, the module's return status will not
+			ignore: When used with a stack of modules, the module's return status will not
 			contribute to the return code the application obtains.
 			

-                        bad: this action indicates that the return code should be thought of as indicative
+                        bad: This action indicates that the return code should be thought of as indicative
 			of the module failing. If this module is the first in the stack to fail, its status value will be used
 			for that of the whole stack.
 			

-                        die: equivalent to bad with the side effect of terminating the module stack and
+                        die: Equivalent to bad with the side effect of terminating the module stack and
 			PAM immediately returning to the application.
 			

-                        ok: this tells PAM that the administrator thinks this return code should
+                        ok: This tells PAM that the administrator thinks this return code should
 			contribute directly to the return code of the full stack of modules. In other words, if the former
 			state of the stack would lead to a return of PAM_SUCCESS, the module's return code will override
 			this value. Note, if the former state of the stack holds some value that is indicative of a modules
-			failure, this 'ok' value will not be used to override that value.
+			failure, this ok value will not be used to override that value.
 			

-                        done: equivalent to ok with the side effect of terminating the module stack and
+                        done: Equivalent to ok with the side effect of terminating the module stack and
 			PAM immediately returning to the application.
                         

-                        reset: clear all memory of the state of the module stack and start again with
+                        reset: Clears all memory of the state of the module stack and starts again with
 			the next stacked module.
 			

-		Each of the four keywords: required; requisite; sufficient; and optional, have an equivalent expression in
-		terms of the [...] syntax. They are as follows:
+		Each of the four keywords: required; requisite; sufficient; and optional,
+		have an equivalent expression in terms of the [...] syntax. They are as follows:
 		

 		

-			required is equivalent to [success=ok new_authtok_reqd=ok ignore=ignore default=bad]
+			required is equivalent to [success=ok new_authtok_reqd=ok ignore=ignore default=bad].
 			

-			requisite is equivalent to [success=ok new_authtok_reqd=ok ignore=ignore default=die]
+			requisite is equivalent to [success=ok new_authtok_reqd=ok ignore=ignore default=die].
 			

-			sufficient is equivalent to [success=done new_authtok_reqd=done default=ignore]
+					sufficient is equivalent to [success=done new_authtok_reqd=done default=ignore].
 			

-			optional is equivalent to [success=ok new_authtok_reqd=ok default=ignore]
+			optional is equivalent to [success=ok new_authtok_reqd=ok default=ignore].
 			

 		

 		Just to get a feel for the power of this new syntax, here is a taste of what you can do with it. With Linux-PAM-0.63,
 		the notion of client plug-in agents was introduced. This is something that makes it possible for PAM to support
 		machine-machine authentication using the transport protocol inherent to the client/server application. With the
-		[ ... value=action ... ] control syntax, it is possible for an application to be configured
+		[ ... value=action ... ] control syntax, it is possible for an application to be configured
 		to support binary prompts with compliant clients, but to gracefully fall over into an alternative authentication
-		mode for older, legacy, applications.
-		
module-path:

+		mode for older, legacy applications.
+		
module-path

 		The path-name of the dynamically loadable object file; the pluggable module itself. If the first character of the
-		module path is `/', it is assumed to be a complete path. If this is not the case, the given module path is appended
+		module path is “/”, it is assumed to be a complete path. If this is not the case, the given module path is appended
 		to the default module path: /lib/security (but see the notes above).
 		

-		The args are a list of tokens that are passed to the module when it is invoked. Much like arguments to a typical
+		The arguments are a list of tokens that are passed to the module when it is invoked, much like arguments to a typical
 		Linux shell command. Generally, valid arguments are optional and are specific to any given module. Invalid arguments
 		are ignored by a module, however, when encountering an invalid argument, the module is required to write an error
-		to syslog(3). For a list of generic options see the next section.
+		to syslog(3). For a list of generic options, see the next section.
 		

-		Note, if you wish to include spaces in an argument, you should surround that argument with square brackets. For example:
+		If you wish to include spaces in an argument, you should surround that argument with square brackets. For example:
 		
 squid auth required pam_mysql.so user=passwd_query passwd=mada \
-        db=eminence [query=select user_name from internet_service where \
-                     user_name='%u' and password=PASSWORD('%p') and \
-                     service='web_proxy']
+db=eminence [query=select user_name from internet_service where \
+user_name=“%u” and password=PASSWORD(“%p”) and service=“web_proxy”]
 

-		Note, when using this convention, you can include `[' characters inside the string, and if you wish to include a `]'
-		character inside the string that will survive the argument parsing, you should use `\['. In other words:
+		When using this convention, you can include “[” characters inside the string, and if you wish to have a “]”
+		character inside the string that will survive the argument parsing, you should use “\[”. In other words:
 		
 [..[..\]..]    -->   ..[..]..
 

-		Any line in (one of) the configuration file(s), that is not formatted correctly, will generally tend (erring on the
+		Any line in one of the configuration files that is not formatted correctly will generally tend (erring on the
 		side of caution) to make the authentication process fail. A corresponding error is written to the system log files
 		with a call to syslog(3). 
-

Example System Configurations

The following is an example /etc/pam.d/login configuration file. -This example had all options been uncommented is probably not usable -as it stacks many conditions before allowing successful completion +This example had all options uncommented and is probably not usable +because it stacks many conditions before allowing successful completion of the login process. Essentially all conditions can be disabled -by commenting them out except the calls to pam_pwdb.so. -

PAM: original login config

+by commenting them out, except the calls to pam_pwdb.so.
+
PAM: Original Login Config
 #%PAM-1.0
-# The PAM configuration file for the `login' service
+# The PAM configuration file for the “login” service
 #
 auth         required    pam_securetty.so
 auth         required    pam_nologin.so
@@ -280,7 +291,7 @@ session      required    pam_pwdb.so
 # session    optional    pam_lastlog.so
 # password   required    pam_cracklib.so retry=3
 password     required    pam_pwdb.so shadow md5
-
PAM: login using pam_smbpass

+

PAM: Login Using `pam_smbpass`

PAM allows use of replaceable modules. Those available on a sample system include:

$/bin/ls /lib/security

@@ -291,17 +302,17 @@ pam_nologin.so   pam_rootok.so       pam_tally.so
 pam_deny.so      pam_issue.so        pam_mail.so       
 pam_permit.so    pam_securetty.so    pam_time.so       
 pam_dialup.so    pam_lastlog.so      pam_mkhomedir.so  
-pam_pwdb.so      pam_shells.so       pam_unix.so       
+pam_pwdb.so      pam_shells.so       pam_UNIX.so       
 pam_env.so       pam_ldap.so         pam_motd.so       
-pam_radius.so    pam_smbpass.so      pam_unix_acct.so  
-pam_wheel.so     pam_unix_auth.so    pam_unix_passwd.so
-pam_userdb.so    pam_warn.so         pam_unix_session.so
+pam_radius.so    pam_smbpass.so      pam_UNIX_acct.so  
+pam_wheel.so     pam_UNIX_auth.so    pam_UNIX_passwd.so
+pam_userdb.so    pam_warn.so         pam_UNIX_session.so

The following example for the login program replaces the use of -the pam_pwdb.so module which uses the system +the pam_pwdb.so module that uses the system password database (/etc/passwd, /etc/shadow, /etc/group) with -the module pam_smbpass.so which uses the Samba +the module pam_smbpass.so, which uses the Samba database which contains the Microsoft MD4 encrypted password hashes. This database is stored in either /usr/local/samba/private/smbpasswd, @@ -311,13 +322,13 @@ Samba implementation for your UNIX/Linux system. The pam_smbpass.so module is provided by Samba version 2.2.1 or later. It can be compiled by specifying the --with-pam_smbpass options when running Samba's -configure script. For more information +configure script. For more information on the pam_smbpass module, see the documentation in the source/pam_smbpass directory of the Samba source distribution.

 #%PAM-1.0
-# The PAM configuration file for the `login' service
+# The PAM configuration file for the “login” service
 #
 auth        required    pam_smbpass.so nodelay
 account     required    pam_smbpass.so nodelay
@@ -328,21 +339,21 @@ The following is the PAM configuration file for a particular
 Linux system. The default condition uses pam_pwdb.so.
 
 #%PAM-1.0
-# The PAM configuration file for the `samba' service
+# The PAM configuration file for the “samba” service
 #
 auth       required     pam_pwdb.so nullok nodelay shadow audit
 account    required     pam_pwdb.so audit nodelay
 session    required     pam_pwdb.so nodelay
 password   required     pam_pwdb.so shadow md5
 

-In the following example the decision has been made to use the 
-smbpasswd database even for basic samba authentication. Such a 
-decision could also be made for the passwd program and would 
-thus allow the smbpasswd passwords to be changed using the passwd 
-program.
+In the following example, the decision has been made to use the 
+smbpasswd database even for basic Samba authentication. Such a 
+decision could also be made for the passwd program and would 
+thus allow the smbpasswd passwords to be changed using the
+passwd program:
 
 #%PAM-1.0
-# The PAM configuration file for the `samba' service
+# The PAM configuration file for the “samba” service
 #
 auth       required     pam_smbpass.so nodelay
 account    required     pam_pwdb.so audit nodelay
@@ -355,128 +366,118 @@ your particular system implementation for details regarding the specific
 capabilities of PAM in this environment. Some Linux implementations also 
 provide the pam_stack.so module that allows all 
 authentication to be configured in a single central file. The 
-pam_stack.so method has some very devoted followers 
+pam_stack.so method has some devoted followers 
 on the basis that it allows for easier administration. As with all issues in 
-life though, every decision makes trade-offs, so you may want examine the 
+life though, every decision makes trade-offs, so you may want to examine the 
 PAM documentation for further helpful information.
-

smb.conf PAM Configuration

- There is an option in smb.conf called obey pam restrictions. -The following is from the on-line help for this option in SWAT; +

`smb.conf` PAM Configuration

+ There is an option in smb.conf called obey pam restrictions. +The following is from the online help for this option in SWAT;

-When Samba is configured to enable PAM support (i.e. ---with-pam), this parameter will -control whether or not Samba should obey PAM's account -and session management directives. The default behavior -is to use PAM for clear text authentication only and to -ignore any account or session management. Note that Samba always -ignores PAM for authentication in the case of -encrypt passwords = yes. -The reason is that PAM modules cannot support the challenge/response -authentication mechanism needed in the presence of SMB +When Samba is configured to enable PAM support (i.e., --with-pam), this parameter will +control whether or not Samba should obey PAM's account and session management directives. The default behavior +is to use PAM for cleartext authentication only and to ignore any account or session management. Samba always +ignores PAM for authentication in the case of encrypt passwords = yes. +The reason is that PAM modules cannot support the challenge/response authentication mechanism needed in the presence of SMB password encryption. -

Default: obey pam restrictions = no

Remote CIFS Authentication using winbindd.so

Default: obey pam restrictions = no

Remote CIFS Authentication Using `winbindd.so`

All operating systems depend on the provision of users credentials acceptable to the platform. UNIX requires the provision of a user identifier (UID) as well as a group identifier (GID). These are both simple integer type numbers that are obtained from a password backend such as /etc/passwd.

-Users and groups on a Windows NT server are assigned a relative id (rid) which is unique for +Users and groups on a Windows NT server are assigned a relative ID (RID) which is unique for the domain when the user or group is created. To convert the Windows NT user or group into -a unix user or group, a mapping between rids and unix user and group ids is required. This +a UNIX user or group, a mapping between RIDs and UNIX user and group IDs is required. This is one of the jobs that winbind performs.

-As winbind users and groups are resolved from a server, user and group ids are allocated +As Winbind users and groups are resolved from a server, user and group IDs are allocated from a specified range. This is done on a first come, first served basis, although all existing users and groups will be mapped as soon as a client performs a user or group -enumeration command. The allocated unix ids are stored in a database file under the Samba +enumeration command. The allocated UNIX IDs are stored in a database file under the Samba lock directory and will be remembered.

The astute administrator will realize from this that the combination of pam_smbpass.so, -winbindd, and a distributed passdb backend, such as ldap, will allow the establishment of a -centrally managed, distributed user/password database that can also be used by all PAM (eg: Linux) aware -programs and applications. This arrangement can have particularly potent advantages compared with the use of -Microsoft Active Directory Service (ADS) in so far as reduction of wide area network authentication traffic. +winbindd and a distributed passdb backend, +such as ldap, will allow the establishment of a centrally managed, distributed user/password +database that can also be used by all PAM-aware (e.g., Linux) programs and applications. This arrangement can have +particularly potent advantages compared with the use of Microsoft Active Directory Service (ADS) in so far as +the reduction of wide area network authentication traffic.

Warning

-The rid to unix id database is the only location where the user and group mappings are -stored by winbindd. If this file is deleted or corrupted, there is no way for winbindd -to determine which user and group ids correspond to Windows NT user and group rids. -

Password Synchronization using pam_smbpass.so

-pam_smbpass is a PAM module which can be used on conforming systems to -keep the smbpasswd (Samba password) database in sync with the unix +The RID to UNIX ID database is the only location where the user and group mappings are +stored by winbindd. If this file is deleted or corrupted, there is no way for winbindd +to determine which user and group IDs correspond to Windows NT user and group RIDs. +

Password Synchronization Using `pam_smbpass.so`

+pam_smbpass is a PAM module that can be used on conforming systems to +keep the smbpasswd (Samba password) database in sync with the UNIX password file. PAM (Pluggable Authentication Modules) is an API supported -under some Unices, such as Solaris, HPUX and Linux, that provides a +under some UNIX operating systems, such as Solaris, HPUX and Linux, that provides a generic interface to authentication mechanisms.

-This module authenticates a local smbpasswd user database. If you require -support for authenticating against a remote SMB server, or if you're -concerned about the presence of suid root binaries on your system, it is -recommended that you use pam_winbind instead. -

-Options recognized by this module are as follows: -

Table 25.1. Options recognized by pam_smbpass

debug	log more debugging info
audit	like debug, but also logs unknown usernames
use_first_pass	don't prompt the user for passwords; take them from PAM_ items instead
try_first_pass	try to get the password from a previous PAM module, fall back to prompting the user
use_authtok	like try_first_pass, but fail if the new PAM_AUTHTOK has not been previously set. (intended for stacking password modules only)
not_set_pass	don't make passwords used by this module available to other modules.
nodelay	don't insert ~1 second delays on authentication failure.
nullok	null passwords are allowed.
nonull	null passwords are not allowed. Used to override the Samba configuration.
migrate	only meaningful in an "auth" context; used to update smbpasswd file with a password used for successful authentication.
smbconf=`file`	specify an alternate path to the `smb.conf` file.

+This module authenticates a local smbpasswd user database. If you require +support for authenticating against a remote SMB server, or if you are +concerned about the presence of SUID root binaries on your system, it is +recommended that you use pam_winbind instead.

Andrew Morgan, for providing the Linux-PAM - framework, without which none of this would have happened
Christian Gafton and Andrew Morgan again, for the - pam_pwdb module upon which pam_smbpass was originally based
Luke Leighton for being receptive to the idea, - and for the occasional good-natured complaint about the project's status - that keep me working on it :)

. +Options recognized by this module are shown in . +

Table 25.1. Options recognized by pam_smbpass

debug	log more debugging info.
audit	like debug, but also logs unknown usernames.
use_first_pass	do not prompt the user for passwords; take them from PAM_ items instead.
try_first_pass	try to get the password from a previous PAM module fall back to prompting the user.
use_authtok	like try_first_pass, but fail if the new PAM_AUTHTOK has not been previously set (intended for stacking password modules only).
not_set_pass	do not make passwords used by this module available to other modules.
nodelay	do not insert ~1 second delays on authentication failure.
nullok	null passwords are allowed.
nonull	null passwords are not allowed. Used to override the Samba configuration.
migrate	only meaningful in an “auth” context; used to update smbpasswd file with a password used for successful authentication.
smbconf=`file`	specify an alternate path to the `smb.conf` file.

-The following are examples of the use of pam_smbpass.so in the format of Linux +The following are examples of the use of pam_smbpass.so in the format of Linux /etc/pam.d/ files structure. Those wishing to implement this tool on other platforms will need to adapt this appropriately. -

Password Synchronisation Configuration

Password Synchronization Configuration

A sample PAM configuration that shows the use of pam_smbpass to make -sure private/smbpasswd is kept in sync when /etc/passwd (/etc/shadow) -is changed. Useful when an expired password might be changed by an -application (such as ssh). +sure private/smbpasswd is kept in sync when /etc/passwd (/etc/shadow) +is changed. Useful when an expired password might be changed by an +application (such as ssh).

 #%PAM-1.0
 # password-sync
 #
 auth       requisite    pam_nologin.so
-auth       required     pam_unix.so
-account    required     pam_unix.so
+auth       required     pam_UNIX.so
+account    required     pam_UNIX.so
 password   requisite    pam_cracklib.so retry=3
-password   requisite    pam_unix.so shadow md5 use_authtok try_first_pass
+password   requisite    pam_UNIX.so shadow md5 use_authtok try_first_pass
 password   required     pam_smbpass.so nullok use_authtok try_first_pass
-session    required     pam_unix.so
-

Password Migration Configuration

-A sample PAM configuration that shows the use of pam_smbpass to migrate -from plaintext to encrypted passwords for Samba. Unlike other methods, +session required pam_UNIX.so +

Password Migration Configuration

+A sample PAM configuration that shows the use of pam_smbpass to migrate +from plaintext to encrypted passwords for Samba. Unlike other methods, this can be used for users who have never connected to Samba shares: -password migration takes place when users ftp in, login using ssh, pop -their mail, etc. +password migration takes place when users ftp in, login using ssh, pop +their mail, and so on.

 #%PAM-1.0
 # password-migration
 #
 auth       requisite   pam_nologin.so
-# pam_smbpass is called IF pam_unix succeeds.
-auth       requisite   pam_unix.so
+# pam_smbpass is called IF pam_UNIX succeeds.
+auth       requisite   pam_UNIX.so
 auth       optional    pam_smbpass.so migrate
-account    required    pam_unix.so
+account    required    pam_UNIX.so
 password   requisite   pam_cracklib.so retry=3
-password   requisite   pam_unix.so shadow md5 use_authtok try_first_pass
+password   requisite   pam_UNIX.so shadow md5 use_authtok try_first_pass
 password   optional    pam_smbpass.so nullok use_authtok try_first_pass
-session    required    pam_unix.so
-

Mature Password Configuration

-A sample PAM configuration for a 'mature' smbpasswd installation. -private/smbpasswd is fully populated, and we consider it an error if -the smbpasswd doesn't exist or doesn't match the UNIX password. +session required pam_UNIX.so +

Mature Password Configuration

+A sample PAM configuration for a mature smbpasswd installation. +private/smbpasswd is fully populated, and we consider it an error if +the SMB password does not exist or does not match the UNIX password.

 #%PAM-1.0
 # password-mature
 #
 auth       requisite    pam_nologin.so
-auth       required     pam_unix.so
-account    required     pam_unix.so
+auth       required     pam_UNIX.so
+account    required     pam_UNIX.so
 password   requisite    pam_cracklib.so retry=3
-password   requisite    pam_unix.so shadow md5 use_authtok try_first_pass
+password   requisite    pam_UNIX.so shadow md5 use_authtok try_first_pass
 password   required     pam_smbpass.so use_authtok use_first_pass
-session    required     pam_unix.so
-

Kerberos Password Integration Configuration

-A sample PAM configuration that shows pam_smbpass used together with -pam_krb5. This could be useful on a Samba PDC that is also a member of +session required pam_UNIX.so +

Kerberos Password Integration Configuration

+A sample PAM configuration that shows pam_smbpass used together with +pam_krb5. This could be useful on a Samba PDC that is also a member of a Kerberos realm.

 #%PAM-1.0
@@ -490,44 +491,40 @@ password   requisite   pam_cracklib.so retry=3
 password   optional    pam_smbpass.so nullok use_authtok try_first_pass
 password   required    pam_krb5.so use_authtok try_first_pass
 session    required    pam_krb5.so
-

Prev	Up	Next
Chapter 24. Desktop Profile Management	Home	Chapter 26. Integrating MS Windows networks with Samba

Prev	Up	Next
Chapter 24. Desktop Profile Management	Home	Chapter 26. Integrating MS Windows Networks with Samba

Chapter 25. PAM based Distributed Authentication

John H. Terpstra

Stephen Langasek

Chapter 25. PAM-Based Distributed Authentication

John H. Terpstra

Stephen Langasek

Note

Features and Benefits

Features and Benefits

Technical Discussion

Technical Discussion

PAM Configuration Syntax

PAM Configuration Syntax

Anatomy of /etc/pam.d Entries

Anatomy of /etc/pam.d Entries

Example System Configurations

Example System Configurations

PAM: original login config

PAM: Original Login Config

PAM: login using pam_smbpass

PAM: Login Using pam_smbpass

smb.conf PAM Configuration

smb.conf PAM Configuration

Remote CIFS Authentication using winbindd.so

Remote CIFS Authentication Using winbindd.so

Warning

Password Synchronization using pam_smbpass.so

Password Synchronization Using pam_smbpass.so

Password Synchronisation Configuration

Password Synchronization Configuration

Password Migration Configuration

Password Migration Configuration

Mature Password Configuration

Mature Password Configuration

Kerberos Password Integration Configuration

Kerberos Password Integration Configuration

Common Errors

Common Errors

pam_winbind problem

pam_winbind Problem

Winbind is not resolving users and groups

Winbind Is Not Resolving Users and Groups

Anatomy of `/etc/pam.d` Entries

Anatomy of `/etc/pam.d` Entries

PAM: Login Using `pam_smbpass`

`smb.conf` PAM Configuration

Remote CIFS Authentication Using `winbindd.so`

Password Synchronization Using `pam_smbpass.so`

`Winbind is not resolving users and groups`

`Winbind Is Not Resolving Users and Groups`