<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <HTML ><HEAD ><TITLE >Configuring PAM for distributed but centrally managed authentication</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.77+"><LINK REL="HOME" TITLE="SAMBA Project Documentation" HREF="samba-howto-collection.html"><LINK REL="UP" TITLE="Optional configuration" HREF="optional.html"><LINK REL="PREVIOUS" TITLE="UNIX Permission Bits and Windows NT Access Control Lists" HREF="unix-permissions.html"><LINK REL="NEXT" TITLE="Hosting a Microsoft Distributed File System tree on Samba" HREF="msdfs.html"></HEAD ><BODY CLASS="CHAPTER" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >SAMBA Project Documentation</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="unix-permissions.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="msdfs.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="PAM" ></A >Chapter 11. Configuring PAM for distributed but centrally managed authentication</H1 ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN1922" ></A >11.1. Samba and PAM</H1 ><P >A number of Unix systems (eg: 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 (<TT CLASS="FILENAME" >/etc/passwd</TT >) 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: <B CLASS="COMMAND" >login</B >, <B CLASS="COMMAND" >passwd</B >, <B CLASS="COMMAND" >chown</B >, etc.</P ><P >PAM provides a mechanism that disconnects these security programs from the underlying authentication/authorization infrastructure. PAM is configured either through one file <TT CLASS="FILENAME" >/etc/pam.conf</TT > (Solaris), or by editing individual files that are located in <TT CLASS="FILENAME" >/etc/pam.d</TT >.</P ><P >The following is an example <TT CLASS="FILENAME" >/etc/pam.d/login</TT > configuration file. This example had all options been uncommented is probably not usable as 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 <TT CLASS="FILENAME" >pam_pwdb.so</TT >.</P ><P ><PRE CLASS="PROGRAMLISTING" >#%PAM-1.0 # The PAM configuration file for the `login' service # auth required pam_securetty.so auth required pam_nologin.so # auth required pam_dialup.so # auth optional pam_mail.so auth required pam_pwdb.so shadow md5 # account requisite pam_time.so account required pam_pwdb.so session required pam_pwdb.so # session optional pam_lastlog.so # password required pam_cracklib.so retry=3 password required pam_pwdb.so shadow md5</PRE ></P ><P >PAM allows use of replacable modules. Those available on a sample system include:</P ><P ><PRE CLASS="PROGRAMLISTING" >$ /bin/ls /lib/security pam_access.so pam_ftp.so pam_limits.so pam_ncp_auth.so pam_rhosts_auth.so pam_stress.so pam_cracklib.so pam_group.so pam_listfile.so 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_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</PRE ></P ><P >The following example for the login program replaces the use of the <TT CLASS="FILENAME" >pam_pwdb.so</TT > module which uses the system password database (<TT CLASS="FILENAME" >/etc/passwd</TT >, <TT CLASS="FILENAME" >/etc/shadow</TT >, <TT CLASS="FILENAME" >/etc/group</TT >) with the module <TT CLASS="FILENAME" >pam_smbpass.so</TT > which uses the Samba database which contains the Microsoft MD4 encrypted password hashes. This database is stored in either <TT CLASS="FILENAME" >/usr/local/samba/private/smbpasswd</TT >, <TT CLASS="FILENAME" >/etc/samba/smbpasswd</TT >, or in <TT CLASS="FILENAME" >/etc/samba.d/smbpasswd</TT >, depending on the Samba implementation for your Unix/Linux system. The <TT CLASS="FILENAME" >pam_smbpass.so</TT > module is provided by Samba version 2.2.1 or later. It can be compiled by specifying the <B CLASS="COMMAND" >--with-pam_smbpass</B > options when running Samba's <TT CLASS="FILENAME" >configure</TT > script. For more information on the <TT CLASS="FILENAME" >pam_smbpass</TT > module, see the documentation in the <TT CLASS="FILENAME" >source/pam_smbpass</TT > directory of the Samba source distribution.</P ><P ><PRE CLASS="PROGRAMLISTING" >#%PAM-1.0 # The PAM configuration file for the `login' service # auth required pam_smbpass.so nodelay account required pam_smbpass.so nodelay session required pam_smbpass.so nodelay password required pam_smbpass.so nodelay</PRE ></P ><P >The following is the PAM configuration file for a particular Linux system. The default condition uses <TT CLASS="FILENAME" >pam_pwdb.so</TT >.</P ><P ><PRE CLASS="PROGRAMLISTING" >#%PAM-1.0 # The PAM configuration file for the `samba' service # auth required /lib/security/pam_pwdb.so nullok nodelay shadow audit account required /lib/security/pam_pwdb.so audit nodelay session required /lib/security/pam_pwdb.so nodelay password required /lib/security/pam_pwdb.so shadow md5</PRE ></P ><P >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.</P ><P ><PRE CLASS="PROGRAMLISTING" >#%PAM-1.0 # The PAM configuration file for the `samba' service # auth required /lib/security/pam_smbpass.so nodelay account required /lib/security/pam_pwdb.so audit nodelay session required /lib/security/pam_pwdb.so nodelay password required /lib/security/pam_smbpass.so nodelay smbconf=/etc/samba.d/smb.conf</PRE ></P ><P >Note: PAM allows stacking of authentication mechanisms. It is also possible to pass information obtained within one PAM module through to the next module in the PAM stack. Please refer to the documentation for your particular system implementation for details regarding the specific capabilities of PAM in this environment. Some Linux implmentations also provide the <TT CLASS="FILENAME" >pam_stack.so</TT > module that allows all authentication to be configured in a single central file. The <TT CLASS="FILENAME" >pam_stack.so</TT > method has some very 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 PAM documentation for further helpful information.</P ></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN1966" ></A >11.2. Distributed Authentication</H1 ><P >The astute administrator will realize from this that the combination of <TT CLASS="FILENAME" >pam_smbpass.so</TT >, <B CLASS="COMMAND" >winbindd</B >, and <B CLASS="COMMAND" >rsync</B > (see <A HREF="http://rsync.samba.org/" TARGET="_top" >http://rsync.samba.org/</A >) 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.</P ></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN1973" ></A >11.3. PAM Configuration in smb.conf</H1 ><P >There is an option in smb.conf called <A HREF="smb.conf.5.html#OBEYPAMRESTRICTIONS" TARGET="_top" >obey pam restrictions</A >. The following is from the on-line help for this option in SWAT;</P ><P >When Samba 2.2 is configure to enable PAM support (i.e. <TT CLASS="CONSTANT" >--with-pam</TT >), 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 <A HREF="smb.conf.5.html#ENCRYPTPASSWORDS" TARGET="_top" >encrypt passwords = yes</A >. The reason is that PAM modules cannot support the challenge/response authentication mechanism needed in the presence of SMB password encryption. </P ><P >Default: <B CLASS="COMMAND" >obey pam restrictions = no</B ></P ></DIV ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="unix-permissions.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="samba-howto-collection.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="msdfs.html" ACCESSKEY="N" >Next</A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >UNIX Permission Bits and Windows NT Access Control Lists</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="optional.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Hosting a Microsoft Distributed File System tree on Samba</TD ></TR ></TABLE ></DIV ></BODY ></HTML >