lib/libutil/login.conf.5

.\" Copyright (c) 1996 David Nugent <davidn@blaze.net.au>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, is permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice immediately at the beginning of the file, without modification,
.\"    this list of conditions, and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. This work was done expressly for inclusion into FreeBSD.  Other use
.\"    is permitted provided this notation is included.
.\" 4. Absolutely no warranty of function or purpose is made by the author
.\"    David Nugent.
.\" 5. Modifications may be freely made to this file providing the above
.\"    conditions are met.
.\"
.Dd June 28, 2023
.Dt LOGIN.CONF 5
.Os
.Sh NAME
.Nm login.conf
.Nd login class capability database
.Sh SYNOPSIS
.Pa /etc/login.conf ,
.Pa ~/.login_conf
.Sh DESCRIPTION
.Nm
contains various attributes and capabilities of login classes.
A login class (an optional annotation against each record in the user
account database,
.Pa /etc/master.passwd )
determines session accounting, resource limits and user environment settings.
It is used by various programs in the system to set up a user's login
environment and to enforce policy, accounting and administrative restrictions.
It also provides the means by which users are able to be
authenticated to the system and the types of authentication available.
Attributes in addition to the ones described here are available with
third-party packages.
.Pp
A special record "default" in the system user class capability database
.Pa /etc/login.conf
is used automatically for any
non-root user without a valid login class in
.Pa /etc/master.passwd .
A user with a uid of 0 without a valid login class will use the record
"root" if it exists, or "default" if not.
.Pp
Users may individually create a file called
.Pa .login_conf
in their home directory using the same format, consisting of a single
entry with a record id of "me".
If present, this file is used by
.Xr login 1
to set user-defined environment settings which override those specified
in the system login capabilities database.
Only a subset of login capabilities may be overridden, typically those
which do not involve authentication, resource limits and accounting.
.Pp
Records in a class capabilities database consist of a number of
colon-separated fields.
The first entry for each record gives one or more names that a record is
to be known by, each separated by a '|' character.
The first name is the most common abbreviation.
The last name given should be a long name that is more descriptive
of the capability entry, and all others are synonyms.
All names but the last should be in lower case and contain no blanks;
the last name may contain upper case characters and blanks for
readability.
.Pp
Note that since a colon
.Pq Ql :\&
is used to separate capability entries, a
.Ql \ec
escape sequence must be used to embed a literal colon in the
value or name of a capability.
.Pp
The default
.Pa /etc/login.conf
shipped with
.Fx
is an out of the box configuration.
Whenever changes to this, or
the user's
.Pa ~/.login_conf ,
file are made, the modifications will not be picked up until
.Xr cap_mkdb 1
is used to compile the file into a database.
This database file will have a
.Pa .db
extension and is accessed through
.Xr cgetent 3 .
See
.Xr getcap 3
for a more in-depth description of the format of a capability database.
.Sh CAPABILITIES
Fields within each record in the database follow the
.Xr getcap 3
conventions for boolean, type string
.Ql \&=
and type numeric
.Ql \&# ,
although type numeric is deprecated in favour of the string format and
either form is accepted for a numeric datum.
Values fall into the following categories:
.Bl -tag -width "program"
.It bool
If the name is present, then the boolean value is true; otherwise, it is
false
.It file
Path name to a data file
.It program
Path name to an executable file
.It list
A list of values (or pairs of values) separated by commas or spaces
.It path
A space or comma separated list of path names, following the usual csh
conventions (leading tilde with and without username being expanded to
home directories etc.)
.It number
A numeric value, either decimal (default), hexadecimal (with leading 0x),
or octal (with a leading 0).
With a numeric type, only one numeric value is allowed.
Numeric types may also be specified in string format (i.e., the capability
tag being delimited from the value by '=' instead of '#').
Whichever method is used, then all records in the database must use the
same method to allow values to be correctly overridden in interpolated
records.
A numeric value may be infinite.
.It size
A number which expresses a size.
The default interpretation of a value is the number of bytes, but a
suffix may specify alternate units:
.Bl -tag -offset indent -compact -width xxxx
.It b
explicitly selects 512-byte blocks
.It k
selects kilobytes (1024 bytes)
.It m
specifies a multiplier of 1 megabyte (1048576 bytes),
.It g
specifies units of gigabytes, and
.It t
represents terabytes.
.El
A size value is a numeric quantity and case of the suffix is not significant.
Concatenated values are added together.
A size value may be infinite.
.It time
A period of time, by default in seconds.
A prefix may specify a different unit:
.Bl -tag -offset indent -compact -width xxxx
.It y
indicates the number of 365 day years,
.It w
indicates the number of weeks,
.It d
the number of days,
.It h
the number of hours,
.It m
the number of minutes, and
.It s
the number of seconds.
.El
Concatenated values are added together.
For example, 2 hours and 40 minutes may be written either as
9600s, 160m or 2h40m.
A time value may be infinite.
.El
.Pp
.Dq infinity ,
.Dq inf ,
.Dq unlimited ,
.Dq unlimit,
and -1
are considered infinite values.
.Pp
The usual convention to interpolate capability entries using the special
.Em tc=value
notation may be used.
.Pp
Default values are specified in the
.Ql Default
column.
If there is no default, the value is inherited from the process setting up the
login environment.
.Sh RESOURCE LIMITS
.Bl -column pseudoterminals indent indent
.It Sy "Name	Type	Default	Description"
.It "coredumpsize	size		Maximum coredump size limit."
.It "cputime	time		CPU usage limit."
.It "datasize	size		Maximum data size limit."
.It "filesize	size		Maximum file size limit."
.It "maxproc	number		Maximum number of processes."
.It "memorylocked	size		Maximum locked in core memory size limit."
.It "memoryuse	size		Maximum of core memory use size limit."
.It "openfiles	number		Maximum number of open files per process."
.It "sbsize	size		Maximum permitted socketbuffer size."
.It "vmemoryuse	size		Maximum permitted total VM usage per process."
.It "stacksize	size		Maximum stack size limit."
.It "pseudoterminals	number		Maximum number of pseudo-terminals."
.It "swapuse	size		Maximum swap space size limit."
.It "umtxp	number		Maximum number of process-shared pthread locks."
.El
.Pp
These resource limit entries actually specify both the maximum
and current limits (see
.Xr getrlimit 2 ) .
The current (soft) limit is the one normally used, although the user is
permitted to increase the current limit to the maximum (hard) limit.
The maximum and current limits may be specified individually by appending a
-max or -cur to the capability name.
.Sh ENVIRONMENT
.Bl -column ignorenologin indent xbinxxusrxbin
.It Sy "Name	Type	Default	Description"
.It "charset	string		Set $MM_CHARSET environment variable to the specified"
value.
.It "cpumask	string		List of cpus to bind the user to."
The syntax is the same as for the
.Fl l
argument of
.Xr cpuset 1
or the word
.Ql default .
If set to
.Ql default
no action is taken.
.It "hushlogin	bool	false	Same as having a ~/.hushlogin file."
.It "ignorenologin	bool	false	Login not prevented by nologin."
.It "ftp-chroot	bool	false	Limit FTP access with"
.Xr chroot 2
to the
.Ev HOME
directory of the user.
See
.Xr ftpd 8
for details.
.It "label	string		Default MAC policy; see"
.Xr maclabel 7 .
.It "lang	string		Set $LANG environment variable to the specified value."
.It "mail	string		Set $MAIL environment variable to the specified value."
.It "manpath	path		Default search path for manpages."
.It "nocheckmail	bool	false	Display mail status at login."
.It "nologin	file		If the file exists it will be displayed and"
the login session will be terminated.
.It "path	path	/bin /usr/bin	Default search path."
.It "priority	number	0	Initial priority level."
A value in the nice range
.Pq -20 to 20 included ,
extended below with the 32 real-time class priorities
.Po
so -52 maps to priority 0 in the real-time class, -51 to 1, and so on until -21
which maps to 31; see
.Xr rtprio 1
.Pc
and above with the 32 idle class priorities
.Po
so 21 maps to priority 0 in the idle class, 22 to 1, and so on until 52 which
maps to 31; see
.Xr idprio 1
.Pc .
Special value
.Ql inherit
prevents resetting the priority.
.It "requirehome 	bool	false	Require a valid home directory to login."
.It "setenv	list		A comma-separated list of environment variables and"
values to which they are to be set.
Values containing commas must be quoted.
.It "shell	prog		Session shell to execute rather than the"
shell specified in the passwd file.
The SHELL environment variable will
contain the shell specified in the password file.
.It "term	string		Default terminal type if not able to determine"
from other means.
.It "timezone	string		Default value of $TZ environment variable."
.It "umask	number		Initial umask. Should always have a leading 0 to"
ensure octal interpretation.
Special value
.Ql inherit
explicitly indicates not to change the umask.
.It "welcome	file	/etc/motd	File containing welcome message."
.El
.Sh AUTHENTICATION
.Bl -column passwd_prompt indent indent
.It Sy "Name	Type	Default	Description"
.\" .It "approve	program 	Program to approve login.
.It "copyright	file		File containing additional copyright information"
.It "host.allow	list		List of remote host wildcards from which users in"
the class may access.
.It "host.deny	list		List of remote host wildcards from which users"
in the class may not access.
.It "login_prompt	string		The login prompt given by"
.Xr login 1
.It "login-backoff	number	3	The number of login attempts"
allowed before the backoff delay is inserted after each subsequent
attempt.
The backoff delay is the number of tries above
.Em login-backoff
multiplied by 5 seconds.
.It "login-retries	number	10	The number of login attempts"
allowed before the login fails.
.It "passwd_format	string	sha512	The encryption format that new or"
changed passwords will use.
Valid values include "des", "md5", "blf", "sha256" and "sha512"; see
.Xr crypt 3
for details.
NIS clients using a
.No non- Ns Fx
NIS server should probably use "des".
.It "passwd_prompt	string		The password prompt presented by"
.Xr login 1
.It "passwordtime	time		Used by"
.Xr passwd 1
to set next password expiry date.
.It "times.allow 	list		List of time periods during which"
logins are allowed.
.It "times.deny	list		List of time periods during which logins are"
disallowed.
.It "ttys.allow	list		List of ttys and ttygroups which users"
in the class may use for access.
.It "ttys.deny	list		List of ttys and ttygroups which users"
in the class may not use for access.
.It "warnexpire	time		Advance notice for pending account expiry."
.It "warnpassword	time		Advance notice for pending password expiry."
.\".It "widepasswords	bool	false	Use the wide password format. The wide password
.\" format allows up to 128 significant characters in the password.
.El
.Pp
These fields are intended to be used by
.Xr passwd 1
and other programs in the login authentication system.
.Pp
Capabilities that set environment variables are scanned for both
.Ql \&~
and
.Ql \&$
characters, which are substituted for a user's home directory and name
respectively.
To pass these characters literally into the environment variable, escape
the character by preceding it with a backslash '\\'.
.Pp
The
.Em host.allow
and
.Em host.deny
entries are comma separated lists used for checking remote access to the system,
and consist of a list of hostnames and/or IP addresses against which remote
network logins are checked.
Items in these lists may contain wildcards in the form used by shell programs
for wildcard matching (See
.Xr fnmatch 3
for details on the implementation).
The check on hosts is made against both the remote system's Internet address
and hostname (if available).
If both lists are empty or not specified, then logins from any remote host
are allowed.
If host.allow contains one or more hosts, then only remote systems matching
any of the items in that list are allowed to log in.
If host.deny contains one or more hosts, then a login from any matching hosts
will be disallowed.
.Pp
The
.Em times.allow
and
.Em times.deny
entries consist of a comma-separated list of time periods during which the users
in a class are allowed to be logged in.
These are expressed as one or more day codes followed by a start and end times
expressed in 24 hour format, separated by a hyphen or dash.
For example, MoThSa0200-1300 translates to Monday, Thursday and Saturday between
the hours of 2 am and 1 p.m..
If both of these time lists are empty, users in the class are allowed access at
any time.
If
.Em times.allow
is specified, then logins are only allowed during the periods given.
If
.Em times.deny
is specified, then logins are denied during the periods given, regardless of whether
one of the periods specified in
.Em times.allow
applies.
.Pp
Note that
.Xr login 1
enforces only that the actual login falls within periods allowed by these entries.
Further enforcement over the life of a session requires a separate daemon to
monitor transitions from an allowed period to a non-allowed one.
.Pp
The
.Em ttys.allow
and
.Em ttys.deny
entries contain a comma-separated list of tty devices (without the /dev/ prefix)
that a user in a class may use to access the system, and/or a list of ttygroups
(See
.Xr getttyent 3
and
.Xr ttys 5
for information on ttygroups).
If neither entry exists, then the choice of login device used by the user is
unrestricted.
If only
.Em ttys.allow
is specified, then the user is restricted only to ttys in the given
group or device list.
If only
.Em ttys.deny
is specified, then the user is prevented from using the specified devices or
devices in the group.
If both lists are given and are non-empty, the user is restricted to those
devices allowed by ttys.allow that are not available by ttys.deny.
.Pp
The
.Em minpasswordlen
and
.Em minpasswordcase
facilities for enforcing restrictions on password quality, which used
to be supported by
.Nm ,
have been superseded by the
.Xr pam_passwdqc 8
PAM module.
.Sh RESERVED CAPABILITIES
The following capabilities are reserved for the purposes indicated and
may be supported by third-party software.
They are not implemented in the base system.
.Bl -column host.accounted indent indent
.It Sy "Name	Type	Default	Description"
.It "accounted	bool	false	Enable session time accounting for all users"
in this class.
.It "auth	list	passwd	Allowed authentication styles."
The first item is the default style.
.It "auth-" Ns Ar type Ta "list		Allowed authentication styles for the"
authentication
.Ar type .
.It "autodelete	time		Time after expiry when account is auto-deleted."
.It "bootfull	bool	false	Enable 'boot only if ttygroup is full' strategy"
when terminating sessions.
.It "daytime	time		Maximum login time per day."
.It "expireperiod	time		Time for expiry allocation."
.It "graceexpire 	time		Grace days for expired account."
.It "gracetime	time		Additional grace login time allowed."
.It "host.accounted	list		List of remote host wildcards from which"
login sessions will be accounted.
.It "host.exempt 	list		List of remote host wildcards from which"
login session accounting is exempted.
.It "idletime	time		Maximum idle time before logout."
.It "minpasswordlen	number	6	The minimum length a local"
password may be.
.It "mixpasswordcase	bool	true	Whether"
.Xr passwd 1
will warn the user if an all lower case password is entered.
.It "monthtime 	time		Maximum login time per month."
.It "refreshtime 	time		New time allowed on account refresh."
.It "refreshperiod	str		How often account time is refreshed."
.It "sessiontime 	time		Maximum login time per session."
.It "sessionlimit	number		Maximum number of concurrent"
login sessions on ttys in any group.
.It "ttys.accounted	list		List of ttys and ttygroups for which"
login accounting is active.
.It "ttys.exempt	list		List of ttys and ttygroups for which login accounting"
is exempt.
.It "warntime	time		Advance notice for pending out-of-time."
.It "weektime	time		Maximum login time per week."
.El
.Pp
The
.Em ttys.accounted
and
.Em ttys.exempt
fields operate in a similar manner to
.Em ttys.allow
and
.Em ttys.deny
as explained
above.
Similarly with the
.Em host.accounted
and
.Em host.exempt
lists.
.Sh SEE ALSO
.Xr cap_mkdb 1 ,
.Xr login 1 ,
.Xr chroot 2 ,
.Xr getcap 3 ,
.Xr getttyent 3 ,
.Xr login_cap 3 ,
.Xr login_class 3 ,
.Xr pam 3 ,
.Xr passwd 5 ,
.Xr ttys 5 ,
.Xr ftpd 8 ,
.Xr pam_passwdqc 8
.Sh HISTORY
The file
.Nm
first appeared in
.Fx 2.1.5 .