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diff --git a/docs/docbook/projdoc/PAM-Authentication-And-Samba.sgml b/docs/docbook/projdoc/PAM-Authentication-And-Samba.sgml new file mode 100644 index 0000000000..6c866acecd --- /dev/null +++ b/docs/docbook/projdoc/PAM-Authentication-And-Samba.sgml @@ -0,0 +1,212 @@ +<chapter id="pam"> + + +<chapterinfo> + <author> + <firstname>John</firstname><surname>Terpstra</surname> + <affiliation> + <orgname>Samba Team</orgname> + <address> + <email>jht@samba.org</email> + </address> + </affiliation> + </author> + + + <pubdate> (Jun 21 2001) </pubdate> +</chapterinfo> + +<title>Configuring PAM for distributed but centrally +managed authentication</title> + +<sect1> +<title>Samba and PAM</title> + +<para> +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 (<filename>/etc/passwd</filename>) +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: <command>login</command>, +<command>passwd</command>, <command>chown</command>, etc. +</para> + +<para> +PAM provides a mechanism that disconnects these security programs +from the underlying authentication/authorization infrastructure. +PAM is configured either through one file <filename>/etc/pam.conf</filename> (Solaris), +or by editing individual files that are located in <filename>/etc/pam.d</filename>. +</para> + +<para> +The following is an example <filename>/etc/pam.d/login</filename> 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 <filename>pam_pwdb.so</filename>. +</para> + +<para><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 +</programlisting></para> + +<para> +PAM allows use of replacable modules. Those available on a +sample system include: +</para> + +<para><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 +</programlisting></para> + +<para> +The following example for the login program replaces the use of +the <filename>pam_pwdb.so</filename> module which uses the system +password database (<filename>/etc/passwd</filename>, +<filename>/etc/shadow</filename>, <filename>/etc/group</filename>) with +the module <filename>pam_smbpass.so</filename> which uses the Samba +database which contains the Microsoft MD4 encrypted password +hashes. This database is stored in either +<filename>/usr/local/samba/private/smbpasswd</filename>, +<filename>/etc/samba/smbpasswd</filename>, or in +<filename>/etc/samba.d/smbpasswd</filename>, depending on the +Samba implementation for your Unix/Linux system. The +<filename>pam_smbpass.so</filename> module is provided by +Samba version 2.2.1 or later. It can be compiled only if the +<constant>--with-pam --with-pam_smbpass</constant> options are both +provided to the Samba <command>configure</command> program. +</para> + +<para><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 +</programlisting></para> + +<para> +The following is the PAM configuration file for a particular +Linux system. The default condition uses <filename>pam_pwdb.so</filename>. +</para> + +<para><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 +</programlisting></para> + +<para> +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. +</para> + +<para><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 +</programlisting></para> + +<para> +Note: PAM allows stacking of authentication mechanisms. It is +also possible to pass information obtained within on 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 <filename>pam_stack.so</filename> module that allows all +authentication to be configured in a single central file. The +<filename>pam_stack.so</filename> 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. +</para> + +</sect1> + +<sect1> +<title>Distributed Authentication</title> + +<para> +The astute administrator will realize from this that the +combination of <filename>pam_smbpass.so</filename>, +<command>winbindd</command>, and <command>rsync</command> (see +<ulink url="http://rsync.samba.org/">http://rsync.samba.org/</ulink>) +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. +</para> + +</sect1> + +<sect1> +<title>PAM Configuration in smb.conf</title> + +<para> +There is an option in smb.conf called <ulink +url="smb.conf.5.html#OBEYPAMRESTRICTIONS">obey pam restrictions</ulink>. +The following is from the on-line help for this option in SWAT; +</para> + +<para> +When Samba 2.2 is configure to enable PAM support (i.e. +<constant>--with-pam</constant>), 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 +<ulink url="smb.conf.5.html#ENCRYPTPASSWORDS">encrypt passwords = yes</ulink>. +The reason is that PAM modules cannot support the challenge/response +authentication mechanism needed in the presence of SMB +password encryption. +</para> + +<para>Default: <command>obey pam restrictions = no</command></para> + +</sect1> +</chapter> |