shadow/man/login.defs.5

.\" Copyright 1991 - 1993, Julianne Frances Haugh and Chip Rosenthal
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.\"	$Id: login.defs.5,v 1.6 1998/12/28 20:35:13 marekm Exp $
.\"
.TH LOGIN 5
.SH NAME
/etc/login.defs \- Login configuration
.SH DESCRIPTION
The
.I /etc/login.defs
file defines the site-specific configuration for the shadow login
suite.  This file is required.  Absence of this file will not prevent
system operation, but will probably result in undesirable operation.
.PP
This file is a readable text file, each line of the file describing
one configuration parameter.  The lines consist of a configuration
name and value, seperated by whitespace.  Blank lines and comment
lines are ignored.  Comments are introduced with a `#' pound sign and
the pound sign must be the first non-white character of the line.
.PP
Parameter values may be of four types:  strings, booleans, numbers,
and long numbers.  A string is comprised of any printable characters.
A boolean should be either the value ``yes'' or ``no''.  An undefined
boolean parameter or one with a value other than these will be given
a ``no'' value.  Numbers (both regular and long) may be either decimal
values, octal values (precede the value with ``0'') or hexadecimal
values (precede the value with ``0x'').  The maximum value of the
regular and long numeric parameters is machine-dependant.
.PP
The following configuration items are provided:
.\"
.IP "CHFN_AUTH (boolean)"
If
.IR yes ,
the
.B chfn
and
.B chsh
programs will ask for password before making any changes, unless
run by the superuser.
.\"
.IP "CHFN_RESTRICT (string)"
This parameter specifies which values in the
.I gecos
field of the
.I passwd
file may be changed by regular users using the
.B chfn
program.  It can be any combination of letters
.IR f ,
.IR r ,
.IR w ,
.IR h ,
for Full name, Room number, Work phone, and Home phone, respectively.
If not specified, only the superuser can make any changes.
.\"
.IP "CONSOLE (string)"
If specified, this definition provides for a restricted set of lines
on which root logins will be allowed.  An attempted root login which
does not meet the criteria established here will be rejected.  The
value of this field may be one of two forms, either a fully-rooted
pathname such as
.sp
.ft I
	CONSOLE /etc/consoles
.ft R
.sp
or a colon-delimited list of terminal lines such as:
.sp
.ft I
	CONSOLE console:tty01:tty02:tty03:tty04
.ft R
.sp
If a pathname is given, each line of the file should specify one
terminal line.  If this parameter is not defined or the specified file
does not exist, then root logins will be allowed from any terminal
line.  Because the removal of this file, or its truncation, could
result in unauthorized root logins, this file must be protected.
Where security is critical, the colon-separated form should be used
to prevent this potential method of attack.
.\"
.IP "CONSOLE_GROUPS (string)"
XXX needs to be documented.
.\"
.IP "CRACKLIB_DICTPATH (string)"
XXX needs to be documented.
.\"
.IP "DEFAULT_HOME (boolean)"
XXX needs to be documented.
.\"
.IP "DIALUPS_CHECK_ENAB (boolean)"
If
.I yes
and an
.I /etc/dialups
file exists, then secondary passwords are enabled upon the dialup
lines specified in this file.  This file should contain a list of
dialups, one per line, for example:
.nf
.sp
.ft I
	ttyfm01
	ttyfm02
	\0\0.
	\0\0.
	\0\0.
.ft R
.sp
.fi
.\"
.IP "ENVIRON_FILE (string)"
XXX needs to be documented.
.\"
.IP "ENV_HZ (string)"
This parameter specifies a value for an HZ environment parameter.
Example usage is:
.sp
	\fIENV_HZ     HZ=50\fR
.sp
If this parameter is not defined then no HZ value will be established.
.\"
.IP "ENV_PATH (string)"
This parameter must be defined as the search path for regular users.
When a login with UID other than zero occurs, the PATH environment
parameter is initialized to this value.  This parameter is required;
if undefined a possibly incorrect default value will be provided.
.\"
.IP "ENV_SUPATH (string)"
This parameter must be defined as the search path for the superuser.
When a login with UID zero occurs, the PATH environment parameter is
initialized to this value.  This parameter is required; if undefined
a possibly incorrect default value will be provided.
.\"
.IP "ENV_TZ (string)"
This parameter specifies information for generating a TZ environment
parameter.  The value must either be the desired contents of TZ, or
the full pathname of a file which contains this information.  Example
usage is:
.sp
	\fIENV_TZ\0\0\0\0TZ=CST6CDT\fP
.sp
or
.sp
	\fIENV_TZ\0\0\0\0/etc/tzname\fP
.sp
If a nonexistent file is named, then TZ will be initialized to some
default value.  If this parameter is not defined then no TZ value will
be established.
.\"
.IP "ERASECHAR (number)"
The terminal
.I erase
character is initialized to this value.  This is supported only on
systems with the
.I termio
interface, e.g. System V.  If not specified, the erase character will
be initialized to a backspace.  See KILLCHAR for related information.
.\"
.IP "FAILLOG_ENAB (boolean)"
If
.I yes
then login failures will be accumulated in
.I /var/log/faillog
in a
.BR faillog (8)
format.
.\"
.IP "FAIL_DELAY (number)"
Delay time in seconds after each failed login attempt.
.\"
.IP "FAKE_SHELL (string)"
Instead of the real user shell, the program specified by this
parameter will be launched, although its visible name (argv[0]) will
be the shell's. The program may do whatever it wants (logging,
additional authentification, banner, ...) before running the actual
shell.
.\"
.IP "FTMP_FILE (string)"
This parameter specifies the full pathname to a file to which login
failures are recorded.  When a login failure occurs, a
.I utmp
format record will be appended to this file.  Note that this differs
from the
.I /var/log/faillog
failure logging in that this facility logs every failure whereas the
``faillog'' facility accumulates failure information per user.  If
this parameter is not specified then logging will be inhibited.  See
FAILLOG_ENAB and LOG_UNKFAIL_ENAB for related information.
.\"
.IP "GID_MAX (number)"
.IP "GID_MIN (number)"
Range of group IDs to choose from for the
.B groupadd
program.
.\"
.IP "HUSHLOGIN_FILE (string)"
This parameter is used to establish ``hushlogin'' conditions.  There
are two possible ways to establish these conditions.  First, if the
value of this parameter is a filename and that file exists in the
user's home directory then ``hushlogin'' conditions will be in effect.
The contents of this file are ignored; its mere presence triggers
``hushlogin'' conditions.  Second, if the value of this parameter is
a full pathname and either the user's login name or the user's shell
is found in this file, then ``hushlogin'' conditions will be in effect.
In this case, the file should be in a format similar to:
.nf
.sp
.ft I
	demo
	/usr/lib/uucp/uucico
	\0\0.
	\0\0.
	\0\0.
.ft R
.sp
.fi
If this parameter is not defined, then ``hushlogin'' conditions will
never occur.  When ``hushlogin'' conditions are established, the
message of the day, last successful and unsuccessful login display,
mail status display, and password aging checks are suppressed.  Note
that allowing hushlogin files in user home directories allows the user
to disable password aging checks.  See MOTD_FILE, FAILLOG_ENAB,
LASTLOG_ENAB, and MAIL_CHECK_ENAB for related information.
.\"
.IP "ISSUE_FILE (string)"
Full pathname of the file to display before each login prompt.
.\"
.IP "KILLCHAR (number)"
The terminal
.I kill
character is initialized to this value.  This is supported only on
systems with the
.I termio
interface, e.g. System V.  If not specified, the kill character will
be initialized to a \s-2CTRL/U\s0.
See ERASECHAR for related information.
.\"
.IP "LASTLOG_ENAB (boolean)"
If
.IR yes ,
and if the
.I /var/log/lastlog
file exists, then a successful user login will be recorded to this
file.  Furthermore, if this option is enabled then the times of the
most recent successful and unsuccessful logins will be displayed to
the user upon login.  The unsuccessful login display will be suppressed
if FAILLOG_ENAB is not enabled.  If ``hushlogin'' conditions are in
effect, then both the successful and unsuccessful login information
will be suppressed.
.\"
.IP "LOGIN_RETRIES (number)"
Number of login attempts allowed before the
.B login
program exits.
.\"
.IP "LOGIN_STRING (string)"
XXX needs to be documented.
.IP "LOGIN_TIMEOUT (number)"
XXX needs to be documented.
.IP "LOG_OK_LOGINS (boolean)"
XXX needs to be documented.
.IP "LOG_UNKFAIL_ENAB (boolean)"
If
.I yes
then unknown usernames will be included when a login failure is
recorded.  Note that this is a potential security risk; a common login
failure mode is transposition of the user name and password, thus this
mode will often cause passwords to accumulate in the failure logs.
If this option is disabled then unknown usernames will be suppressed
in login failure messages.
.\"
.IP "MAIL_CHECK_ENAB (boolean)"
If
.IR yes ,
the user will be notified of his or her mailbox status upon login.
See MAIL_DIR for related information.
.\"
.IP "MAIL_DIR (string)"
This parameter specifies the full pathname to the directory which
contains the user mailbox files.  The user's login name is appended
to this path to form the MAIL environment parameter \- the path to
the user's mailbox.  Either this parameter or MAIL_FILE must be defined;
if undefined some possibly incorrect default value will be assumed.
See MAIL_CHECK_ENAB for related information.
.\"
.IP "MAIL_FILE (string)"
This parameter specifies the name of the user's mailbox file.  This
name is appended to the name of the user's home directory to form the
MAIL environment parameter \- the path to the user's mailbox.  Either
this parameter or MAIL_DIR must be defined; if undefined some possibly
incorrect default value will be assumed.  See MAIL_CHECK_ENAB for
related information.
.\"
.IP "MD5_CRYPT_ENAB (boolean)"
If
.IR yes ,
the
.B passwd
program will encrypt newly changed passwords using a new MD5-based
.BR crypt (3)
password hashing algorithm, which originally appeared in FreeBSD, and
is also supported by libc-5.4.38 and glibc-2.0 (or higher) on Linux.
This algorithm allows passwords longer than 8 characters (limited by
.BR getpass (3)
to 127 characters), but is incompatible with traditional
.BR crypt (3)
implementations.
.\"
.IP "MOTD_FILE (string)"
This parameter specifies a colon-delimited list of pathnames to ``message
of the day'' files.
If a specified file exists, then its contents are displayed to the user
upon login.
If this parameter is not defined or ``hushlogin'' login conditions are
in effect, this information will be suppressed.
.\"
.IP "NOLOGINS_FILE (string)"
This parameter specifies the full pathname to a file which inhibits
non-root logins.  If this file exists and a user other than root
attempts to log in, the contents of the file will be displayed and
the user will be disconnected.  If this parameter is not specified
then this feature will be inhibited.
.\"
.IP "NOLOGIN_STR (string)"
XXX needs to be documented.
.\"
.IP "OBSCURE_CHECKS_ENAB (boolean)"
If
.IR yes ,
the
.B passwd
program will perform additional checks before accepting a password change.
The checks performed are fairly simple, and their use is recommended.
These obscurity checks are bypassed if
.B passwd
is run by
.IR root .
See PASS_MIN_LEN for related information.
.\"
.IP "PASS_ALWAYS_WARN (boolean)"
XXX needs to be documented.
.\"
.IP "PASS_CHANGE_TRIES (number)"
XXX needs to be documented.
.\"
.IP "PASS_MIN_DAYS (number)"
The minimum number of days allowed between password changes.  Any password
changes attempted sooner than this will be rejected.  If not specified, a
zero value will be assumed.
.\"
.IP "PASS_MIN_LEN (number)"
The minimum number of characters in an acceptable password.  An attempt to
assign a password with fewer characters will be rejected.  A zero value
suppresses this check.  If not specified, a zero value will be assumed.
.\"
.IP "PASS_MAX_DAYS (number)"
The maximum number of days a password may be used.  If the password is
older than this, then the account will be locked.  If not specified,
a large value will be assumed.
.\"
.IP "PASS_MAX_LEN (number)"
XXX needs to be documented.
.\"
.IP "PASS_WARN_AGE (number)"
The number of days warning given before a password expires.  A zero means
warning is given only upon the day of expiration, a negative value means
no warning is given.  If not specified, no warning will be provided.
.\"
.IP "PORTTIME_CHECKS_ENAB (boolean)"
If
.I yes
and an
.I /etc/porttime
file exists, that file will be consulted to ensure the user may login
at this time on the given line.
c.f.
.BR porttime (5)
.\"
.IP "QMAIL_DIR (string)"
For Qmail users, this parameter specifies a directory where a Maildir
hierarchy is stored.
See MAIL_CHECK_ENAB for related information.
.\"
.IP "QUOTAS_ENAB (boolean)"
If
.I yes ,
then the user's ``ulimit,'' ``umask,'' and ``niceness'' will be
initialized to the values if specified in the
.I gecos
field of the
.I passwd
file.
c.f.
.BR passwd (5).
.\"
.IP "SU_NAME (string)"
This parameter assigns a command name when ``su -'' is run.  For
example, if the parameter is defined as ``su'', then a
.BR ps (1)
listing would show the command running as ``-su''.  If this parameter
is undefined, then a
.BR ps (1)
listing would show the name of the actual shell being run, e.g.
something like ``-sh''.
.\"
.IP "SULOG_FILE (string)"
This parameter specifies a full pathname of a file in which
.B su
activity is logged.
If this parameter is not specified, the logging is suppressed.
Because the
.B su
command may be used when attempting to authenticate a password,
either this option, or
.I syslog
should be used to note
.B su
activity.  See the SYSLOG_SU_ENAB option for related information.
.\"
.IP "SU_WHEEL_ONLY (boolean)"
XXX needs to be documented.
.\"
.IP "SYSLOG_SG_ENAB (boolean)"
XXX needs to be documented.
.\"
.IP "SYSLOG_SU_ENAB (boolean)"
If
.I yes
and
.B login
was compiled with
.I syslog
support, then all
.B su
activity will be noted through the
.I syslog
facility.
See SULOG_FILE for related information.
.\"
.IP "TTYGROUP (string or number)"
The group ownership of the terminal is initialized to this group
name or number.  One well-known security attack involves forcing terminal
control sequences upon another user's terminal line.  This problem
can be averted by disabling permissions which allow other users to
access the terminal line, but this unfortunately prevents programs
such as
.B write
from operating.  Another solution is to use a version of the
.B write
program which filters out potentially dangerous character sequences,
make this program ``setgid'' to a special group, assign group ownership
of the terminal line to this special group, and assign permissions of
\fI0620\fR to the terminal line.  The TTYGROUP definition has been
provided for just this situation.  If this item is not defined, then
the group ownership of the terminal is initialized to the user's group
number.  See TTYPERMS for related information.
.\"
.IP "TTYPERM (number)"
The login terminal permissions are initialized to this value.  Typical
values will be \fI0622\fR to permit others write access to the line
or \fI0600\fR to secure the line from other users.  If not specified,
the terminal permissions will be initialized to \fI0622\fR.  See
TTYGROUP for related information.
.\"
.IP "TTYTYPE_FILE (string)"
This parameter specifies the full pathname to a file which maps terminal
lines to terminal types.  Each line of the file contains a terminal
type and a terminal line, seperated by whitespace, for example:
.nf
.sp
.ft I
	vt100\0	tty01
	wyse60	tty02
	\0\0.\0\0\0	\0\0.
	\0\0.\0\0\0	\0\0.
	\0\0.\0\0\0	\0\0.
.ft R
.sp
.fi
This information is used to initialize the TERM environment parameter.
A line starting with a ``#'' pound sign will be treated as a comment.
If this paramter is not specified, the file does not exist, or the terminal
line is not found in the file, then the TERM environment parameter will not
be set.
.\"
.IP "UID_MAX (number)"
XXX needs to be documented.
.IP "UID_MIN (number)"
XXX needs to be documented.
.\"
.IP "ULIMIT (long number)"
The file size limit is initialized to this value.  This is supported
only on systems with a
.IR ulimit ,
e.g. System V.  If not specified, the file size limit will be initialized
to some large value.
.\"
.IP "UMASK (number)"
The permission mask is initialized to this value.  If not specified,
the permission mask will be initialized to zero.
.\"
.IP "USERDEL_CMD (string)"
XXX needs to be documented.
.\"
.SH CROSS REFERENCE
The following cross reference shows which programs in the shadow login
suite use which parameters.
.na
.IP login 12
CONSOLE DIALUPS_CHECK_ENAB ENV_HZ ENV_SUPATH ENV_TZ ERASECHAR FAILLOG_ENAB
FTMP_FILE HUSHLOGIN_FILE KILLCHAR LASTLOG_ENAB LOG_UNKFAIL_ENAB
MAIL_CHECK_ENAB MAIL_DIR MOTD_FILE NOLOGINS_FILE PORTTIME_CHECKS_ENAB
QUOTAS_ENAB TTYPERM TTYTYPE_FILE ULIMIT UMASK
.IP newusers 12
PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE UMASK
.IP passwd 12
OBSCURE_CHECKS_ENAB PASS_MIN_LEN
.IP pwconv 12
PASS_MAX_DAYS PASS_MIN_DAYS PASS_WARN_AGE
.IP su 12
ENV_HZ ENV_SUPATH ENV_TZ HUSHLOGIN_FILE MAIL_CHECK_ENAB MAIL_DIR
MOTD_FILE NOLOGIN_STR QUOTAS_ENAB SULOG_FILE SYSLOG_SU_ENAB
.IP sulogin 12
ENV_HZ ENV_SUPATH ENV_TZ MAIL_DIR QUOTAS_ENAB TTYPERM
.ad
.SH BUGS
Some of the supported configuration parameters are not documented in this
manual page.
.SH SEE ALSO
.BR login (1),
.BR passwd (5),
.BR faillog (5),
.BR porttime (5),
.BR faillog (8)
.SH AUTHORS
Julianne Frances Haugh (jfh@bga.com)
.br
Chip Rosenthal (chip@unicom.com)