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Editing: PasswordDatabase.PAM.txt
PAM - Pluggable Authentication Modules ====================================== This is the most common way to authenticate system users nowadays. PAM is not itself a password database, but rather its configuration tells the system how exactly to do the authentication. Usually this means using the 'pam_unix.so' module, which authenticates user from the system's shadow password file. Because PAM is not an actual database, only plaintext authentication mechanisms can be used with PAM. PAM cannot be used as a user database either (although static user templates could be used to provide the same effect). Usually PAM is used with <passwd> [AuthDatabase.Passwd.txt] (NSS) or <static> [UserDatabase.Static.txt] user databases. Dovecot should work with Linux PAM, Solaris PAM, OpenPAM (FreeBSD) and ApplePAM (Mac OS X). Service name ------------ The PAM configuration is usually in the '/etc/pam.d/' directory, but some systems may use a single file,'/etc/pam.conf'. By default Dovecot uses 'dovecot' as the PAM service name, so the configuration is read from '/etc/pam.d/dovecot'. You can change this by giving the wanted service name in the 'args' parameter. You can also set the service to '%s' in which case Dovecot automatically uses either 'imap' or 'pop3' as the service, depending on the actual service the user is logging in to. Here are a few examples: * Use '/etc/pam.d/imap' and '/etc/pam.d/pop3': ---%<---------------------------------------------------------------------- passdb { driver = pam args = %s } ---%<---------------------------------------------------------------------- * Use '/etc/pam.d/mail': ---%<---------------------------------------------------------------------- passdb { driver = pam args = mail } ---%<---------------------------------------------------------------------- PAM sessions ------------ By giving a 'session=yes' parameter, you can make Dovecot open a PAM session and close it immediately. Some PAM plugins need this, for instance 'pam_mkhomedir'. With this parameter, 'dovecot.conf' might look something like this: ---%<------------------------------------------------------------------------- passdb { driver = pam args = session=yes dovecot } ---%<------------------------------------------------------------------------- PAM credentials --------------- By giving a 'setcred=yes' parameter, you can make Dovecot create PAM credentials. Some PAM plugins need this. The credentials are never deleted however, so using this might cause problems with other PAM plugins. Limiting the number of PAM lookups ---------------------------------- Usually in other software PAM is used to do only a single lookup in a process, so PAM plugin writers haven't done much testing on what happens when multiple lookups are done. Because of this, many PAM plugins leak memory and possibly have some other problems when doing multiple lookups. If you notice that PAM authentication stops working after some time, you can limit the number of lookups done by the auth worker process before it dies: ---%<------------------------------------------------------------------------- passdb { driver = pam args = max_requests=100 } ---%<------------------------------------------------------------------------- The default max_requests value is 100. Username changing ----------------- A PAM module can change the username. Making PAM plugin failure messages visible ------------------------------------------ You can replace the default "Authentication failed" reply with PAM's failure reply by setting: ---%<------------------------------------------------------------------------- passdb { driver = pam args = failure_show_msg=yes } ---%<------------------------------------------------------------------------- This can be useful with e.g. pam_opie to find out which one time password you're supposed to give: ---%<------------------------------------------------------------------------- 1 LOGIN username otp 1 NO otp-md5 324 0x1578 ext, Response: ---%<------------------------------------------------------------------------- Restrict IP-Addresses allowed to connect via PAM ------------------------------------------------ You can restrict the IP-Addresses allowed to connect via PAM: ---%<------------------------------------------------------------------------- passdb { driver = pam override_fields = allow_nets=10.1.100.0/23,2001:db8:a0b:12f0::/64 } ---%<------------------------------------------------------------------------- Caching ------- Dovecot supports caching password lookups by setting 'auth_cache_size' to non-zero value. For this to work with PAM, you'll also have to give 'cache_key' parameter. Usually the user is authenticated only based on the username and password, but PAM plugins may do all kinds of other checks as well, so this can't be relied on. For this reason the 'cache_key' must contain all the <variables> [Variables.txt] that may affect authentication. The commonly used variables are: * '%u' - Username. You'll most likely want to use this. * '%s' - Service. If you use '*' as the service name you'll most likely want to use this. * '%r' - Remote IP address. Use this if you do any IP related checks. * '%l' - Local IP address. Use this if you do any checks based on the local IP address that was connected to. Examples: ---%<------------------------------------------------------------------------- # 1MB auth cache size auth_cache_size = 1024 passdb { driver = pam # username and service args = cache_key=%u%s * } ---%<------------------------------------------------------------------------- ---%<------------------------------------------------------------------------- # 1MB auth cache size auth_cache_size = 1024 passdb { driver = pam # username, remote IP and local IP args = cache_key=%u%r%l dovecot } ---%<------------------------------------------------------------------------- Examples -------- Linux ----- Here is an example '/etc/pam.d/dovecot' configuration file which uses standard UNIX authentication: ---%<------------------------------------------------------------------------- auth required pam_unix.so nullok account required pam_unix.so ---%<------------------------------------------------------------------------- Solaris ------- For Solaris you will have to edit '/etc/pam.conf'. Here is a working Solaris example (using 'args = *' instead of the default 'dovecot' service): ---%<------------------------------------------------------------------------- imap auth requisite pam_authtok_get.so.1 imap auth required pam_unix_auth.so.1 imap account requisite pam_roles.so.1 imap account required pam_unix_account.so.1 imap session required pam_unix_session.so.1 pop3 auth requisite pam_authtok_get.so.1 pop3 auth required pam_unix_auth.so.1 pop3 account requisite pam_roles.so.1 pop3 account required pam_unix_account.so.1 pop3 session required pam_unix_session.so.1 ---%<------------------------------------------------------------------------- Mac OS X -------- On Mac OS X, the '/etc/pam.d/dovecot' file might look like this: ---%<------------------------------------------------------------------------- auth required pam_opendirectory.so try_first_pass account required pam_nologin.so account required pam_opendirectory.so password required pam_opendirectory.so ---%<------------------------------------------------------------------------- ...which, as the equivalent of '/etc/pam.d/login' on OS X 10.9. For very old versions of OS X (e.g. 10.4), can be represented (where?) as the following in the on that OS: ---%<------------------------------------------------------------------------- passdb { driver = pam args = login } ---%<------------------------------------------------------------------------- On older versions of Mac OS X, "passwd" can be used as a userdb to fill in UID, GID, and homedir information after PAM was used as a passdb, even though Directory Services prevents "passdb passwd" from working as a username/password authenticator. This will provide full system user authentication with true homedir mail storage, without resorting to a single virtual mail user or LDAP: ---%<------------------------------------------------------------------------- userdb { driver = passwd } ---%<------------------------------------------------------------------------- (This file was created from the wiki on 2019-06-19 12:42)
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