path: root/lib/libpam/modules/pam_unix/pam_unix.8

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.Dd April 3, 2020
.Dt PAM_UNIX 8
.Os
.Sh NAME
.Nm pam_unix
.Nd UNIX PAM module
.Sh SYNOPSIS
.Op Ar service-name
.Ar module-type
.Ar control-flag
.Pa pam_unix
.Op Ar options
.Sh DESCRIPTION
The
.Ux
authentication service module for PAM,
.Nm
provides functionality for three PAM categories:
authentication, account management, and password management.
In terms of the
.Ar module-type
parameter, they are the
.Dq Li auth ,
.Dq Li account ,
and
.Dq Li password
features.
It also provides a null function for session management.
.Ss Ux Ss Authentication Module
The
.Ux
authentication component provides functions to verify the identity of
a user
.Pq Fn pam_sm_authenticate ,
which obtains the relevant
.Xr passwd 5
entry.
It prompts the user for a password and verifies that this is correct with
.Xr crypt 3 .
.Pp
The following options may be passed to the authentication module:
.Bl -tag -width ".Cm use_first_pass"
.It Cm debug
.Xr syslog 3
debugging information at
.Dv LOG_DEBUG
level.
.It Cm use_first_pass
If the authentication module is not the first in the stack, and a
previous module obtained the user's password, that password is used to
authenticate the user.
If this fails, the authentication module returns failure without
prompting the user for a password.
This option has no effect if the authentication module is the first in
the stack, or if no previous modules obtained the user's password.
.It Cm try_first_pass
This option is similar to the
.Cm use_first_pass
option, except that if the previously obtained password fails, the
user is prompted for another password.
.It Cm auth_as_self
This option will require the user to authenticate themselves as
themselves, not as the account they are attempting to access.
This is primarily for services like
.Xr su 1 ,
where the user's ability to retype their own password might be deemed
sufficient.
.It Cm nullok
If the password database has no password for the entity being
authenticated, then this option will forgo password prompting, and
silently allow authentication to succeed.
.Pp
.Sy NOTE:
If
.Nm
is invoked by a process that does not have the privileges required to
access the password database (in most cases, this means root
privileges), the
.Cm nullok
option may cause
.Nm
to allow any user to log in with any password.
.It Cm emptyok
If the password database contains the password for the entity being
authenticated, but the password matches an empty string,
then this option will forgo password prompting, and
silently allow authentication to succeed.
.Pp
The difference between this and
.Cm nullok
is that it avoids prompting for password when the password is set
to an empty string, as opposed to not being set.
.It Cm local_pass
Use only the local password database, even if NIS is in use.
This will cause an authentication failure if the system is configured
to only use NIS.
.It Cm nis_pass
Use only the NIS password database.
This will cause an authentication failure if the system is not
configured to use NIS.
.El
.Ss Ux Ss Account Management Module
The
.Ux
account management component provides a function to perform account
management,
.Fn pam_sm_acct_mgmt .
The function verifies that the authenticated user is allowed to log
into the local user account by checking the following criteria:
.Bl -dash -offset indent
.It
locked status of the account compatible with
.Xr pw 8
.Cm lock ;
.It
the password expiry date from
.Xr passwd 5 ;
.It
.Xr login.conf 5
restrictions on the remote host, login time, and tty.
.El
.Pp
The following options may be passed to the management module:
.Bl -tag -width ".Cm use_first_pass"
.It Cm debug
.Xr syslog 3
debugging information at
.Dv LOG_DEBUG
level.
.El
.Ss Ux Ss Password Management Module
The
.Ux
password management component provides a function to perform password
management,
.Fn pam_sm_chauthtok .
The function changes
the user's password.
.Pp
The following options may be passed to the password module:
.Bl -tag -width ".Cm use_first_pass"
.It Cm debug
.Xr syslog 3
debugging information at
.Dv LOG_DEBUG
level.
.It Cm no_warn
suppress warning messages to the user.
These messages include reasons why the user's authentication attempt
was declined.
.It Cm local_pass
forces the password module to change a local password in favour of a
NIS one.
.It Cm nis_pass
forces the password module to change a NIS password in favour of a
local one.
.El
.Sh FILES
.Bl -tag -width ".Pa /etc/master.passwd" -compact
.It Pa /etc/master.passwd
default
.Ux
password database.
.El
.Sh SEE ALSO
.Xr passwd 1 ,
.Xr getlogin 2 ,
.Xr crypt 3 ,
.Xr getpwent 3 ,
.Xr syslog 3 ,
.Xr nsswitch.conf 5 ,
.Xr passwd 5 ,
.Xr pam 3 ,
.Xr pw 8 ,
.Xr yp 8
.Sh BUGS
The
.Nm
module ignores the
.Dv PAM_CHANGE_EXPIRED_AUTHTOK
flag.