LOGIN.CONF(5) BSD Reference Manual LOGIN.CONF(5)
login.conf - login class capability database
/etc/login.conf
The login.conf file describes the various attributes of login classes. A
login class determines what styles of authentication are available as
well as session resource limits and environment setup. While designed
primarily for the login(1) program, it is also used by other programs,
e.g., ftpd(8), to determine what means of authentication are available.
It is also used by programs, e.g., rshd(8), which need to set up a user
environment.
A special record, "default", in /etc/login.conf is used for any user
without a valid login class in /etc/master.passwd.
Sites with very large /etc/login.conf files may wish to create a database
version of the file, /etc/login.conf.db, for improved performance. Using
a database version for small files does not result in a performance im-
provement. To build /etc/login.conf.db from /etc/login.conf the following
command may be used:
# cap_mkdb /etc/login.conf
Note that cap_mkdb(1) must be run after each edit of /etc/login.conf to
keep the database version in sync with the plain file.
Refer to getcap(3) for a description of the file layout. All entries in
the login.conf file are either boolean or use a '=' to separate the capa-
bility from the value. The types are described after the capability
table.
Name Type Default Description
approve program Default program to approve lo-
gin.
approve-service program Program to approve login for
service.
auth list passwd Allowed authentication styles.
The first value is the default
styles.
auth-type list Allowed authentication styles
for the authentication type
type.
classify program Classify type of login.
copyright file File containing additional
copyright information.
coredumpsize size Maximum coredump size limit.
cputime time CPU usage limit.
datasize size Maximum data size limit.
expire-warn time 2w If the user's account will ex-
pire within this length of time
then warn the user of this.
filesize size Maximum file size limit.
hushlogin bool false Same as having a
$HOME/.hushlogin file. See
login(1).
ignorenologin bool false Not affected by nologin files.
See login(1).
localcipher string blowfish,6 The cipher to use for local
passwords. Possible values are:
"old", "newsalt,<rounds>",
"md5", and "blowfish,<rounds>"
where "old" means classic 56-
bit DES. For "newsalt" the
value of rounds is a 24-bit in-
teger with a minimum of 7250
rounds. For "blowfish" the
value can be between 4 and 31.
It specifies the base 2 loga-
rithm of the number of rounds.
ypcipher string old The cipher to use for YP pass-
words. The possible values are
the same as for localcipher.
login-backoff number 3 After login-backoff unsuccess-
ful login attempts during a
single session, login(1) will
start sleeping a bit in between
attempts.
login-timeout time 300 Number of seconds before
login(1) times out at the pass-
word prompt. Note that this
setting is only valid for the
default record.
login-tries number 10 Number of tries a user gets to
successfully login before
login(1) closes the connection.
stacksize size Maximum stack size limit.
maxproc number Maximum number of processes.
memorylocked size Maximum locked in core memory
size limit.
memoryuse size Maximum in core memoryuse size
limit.
minpasswordlen number 6 The minimum length a local
password may be. If a negative
value or zero, no length res-
trictions are enforced. Used by
the passwd(1) utility.
nologin file If the file exists it will be
displayed and the login session
will be terminated.
openfiles number Maximum number of open file
descriptors per process.
password-dead time 0 Length of time a password may
be expired but not quite dead
yet. When set (for both the
client and remote server
machine when doing remote au-
thentication), a user is al-
lowed to log in just one more
time after their password (but
not account) has expired. This
allows a grace period for up-
dating their password.
password-warn time 2w If the user's password will ex-
pire within this length of time
then warn the user of this.
passwordcheck program An external program that checks
the quality of the password.
The password is passed to the
program on stdin. An exit code
of 0 indicates that the quality
of the password is sufficient,
an exit code of 1 signals that
the password failed the check.
passwordtime time The lifetime of a password in
seconds, reset every time a
user changes their password.
When this value is exceeded the
user will no longer be able to
login unless the password-dead
option has been specified. Used
by the passwd(1) utility.
passwordtries number 3 The number of times the
passwd(1) utility enforces a
check on the password. If 0,
the new password will only be
accepted if it passes the pass-
word quality check.
path path value of _PATH_DEFPATH
Default search path. See
/usr/include/paths.h.
priority number Initial priority (nice) level.
requirehome bool false Require home directory to lo-
gin.
setenv envlist A list of environment variables
and associated values to be set
for the class.
shell program Session shell to execute rather
than the shell specified in the
password file. The SHELL en-
vironment variable will contain
the shell specified in the
password file.
term string su Default terminal type if not
able to determine from other
means.
umask number 022 Initial umask. Should always
have a leading 0 to ensure oc-
tal interpretation. See
umask(2).
vmemoryuse size Maximum virtual memoryuse size
limit.
welcome file /etc/motd File containing welcome mes-
sage.
The resource limit entries (cputime, filesize, datasize, memoryuse,
memorylocked, maxproc, and openfiles) actually specify both the maximum
and current limits (see getrlimit(2)). The current limit is the one nor-
mally used, although the user is permitted to increase the current limit
to the maximum limit. The maximum and current limits may be specified in-
dividually by appending a -max or -cur to the capability name (e.g.,
openfiles-max and openfiles-cur).
OpenBSD will never define capabilities which start with x- or X-, these
are reserved for external use (unless included through contributed
software).
The argument types are defined as:
envlist A comma-separated list of environment variables of the form
variable=value. If no value is specified, the '=' is optional.
A ~ in the path name is expanded to the user's home directory
if it is at the end of a string or is followed by a slash
('/') or the user's login name. A $ in the path name is ex-
panded to the user's login name.
file Path name to a text file.
list A comma-separated list of values.
number A number. A leading 0x implies the number is expressed in hex-
adecimal. A leading 0 implies the number is expressed in oc-
tal. Any other number is treated as decimal.
path A space-separated list of path names. Login name and directory
are substituted as for envlist. Additionally, a ~ is only ex-
panded at the beginning of a path name.
program A path name to program.
size A number which expresses a size in bytes. It may have a trail-
ing b to multiply the value by 512, a k to multiply the value
by 1 K (1024), and an m to multiply the value by 1 M
(1048576).
time A time in seconds. A time may be expressed as a series of
numbers which are added together. Each number may have a
trailing character to represent time units:
y Indicates a number of 365 day years.
w Indicates a number of 7 day weeks.
d Indicates a number of 24 hour days.
h Indicates a number of 60 minute hours.
m Indicates a number of 60 second minutes.
s Indicates a number of seconds.
For example, to indicate 1 and 1/2 hours, the following string
could be used: 1h30m.
MirBSD #10-current uses BSD Authentication, which is made up of a variety
of authentication styles. The authentication styles currently provided
are:
activ Authenticate using an ActivCard token. See login_activ(8).
chpass Change user's password. See login_chpass(8).
crypto Authenticate using a CRYPTOCard token. See
login_crypto(8).
krb5 Request a password and use it to request a ticket from the
kerberos 5 server. See login_krb5(8).
krb5-or-pwd Request a password and first try the krb5 authentication
style and if that fails use the same password with the
passwd authentication style. See login_krb5-or-pwd(8).
lchpass Change user's local password. See login_lchpass(8).
passwd Request a password and check it against the password in
the master.passwd file. See login_passwd(8).
radius Normally linked to another authentication type, contact
the radius server to do authentication. See
login_radius(8).
reject Request a password and reject any request. See
login_reject(8).
rpasswd Request a password and check it against the password in
the rpasswd.db file.
skey Send a challenge and request a response, checking it with
S/Key (tm) authentication. See login_skey(8).
snk Authenticate using a SecureNet Key token. See
login_snk(8).
token Authenticate using a generic X9.9 token. See
login_token(8).
Local authentication styles may be added by creating a login script for
the style (see below). To prevent collisions with future official BSD Au-
thentication style names all local style names should start with a dash
(-). Current plans are for all official BSD Authentication style names to
begin with a lower case alphabetic character. For example, if you have a
new style you refer to as slick then you should create an authentication
script named /usr/libexec/auth/login_-slick using the style name -slick.
When logging in via the login(1) program, the syntax user:-slick would be
used.
Authentication requires several pieces of information:
class The login class being used.
service The type of service requesting authentication. The service
type is used to determine what information the authentication
program can provide to the user and what information the user
can provide to the authentication program.
The service type login is appropriate for most situations.
Two other service types, challenge and response, are provided
for use by programs like ftpd(8) and radiusd. If no service
type is specified, login is used.
style The authentication style being used.
type The authentication type, used to determine the available au-
thentication styles.
username The name of the user to authenticate. The name may contain an
instance, e.g. "user/root", as used by Kerberos authentica-
tion. If the authentication style being used does not support
such instances, the request will fail.
The program requesting authentication must specify a username and an au-
thentication style. (For example, login(1) requests a username from the
user. Users may enter usernames of the form "user:style" to optionally
specify the authentication style.) The requesting program may also speci-
fy the type of authentication that will be done. Most programs will only
have a single type, if any at all, i.e., ftpd(8) will always request the
ftp type authentication, and su(1) will always request the su type au-
thentication. The login(1) utility is special in that it may select an
authentication type based on information found in the /etc/ttys file for
the appropriate tty (see ttys(5)).
The class to be used is normally determined by the class field in the
password file (see passwd(5)).
The class is used to look up a corresponding entry in the login.conf
file. If an authentication type is defined and a value for auth-type ex-
ists in that entry, it will be used as a list of potential authentication
styles. If an authentication type is not defined, or auth-type is not
specified for the class, the value of auth is used as the list of avail-
able authentication styles.
If the user did not specify an authentication style the first style in
the list of available styles is used. If the user did specify an authen-
tication style and the style is in the list of available styles it will
be used, otherwise the request is rejected.
For any given style, the program /usr/libexec/auth/login_style is used to
perform the authentication. The synopsis of this program is:
/usr/libexec/auth/login_style [-v name=value] [-s service] username class
The -v option is used to specify arbitrary information to the authentica-
tion programs. Any number of -v options may be used. The login(1) program
provides the following through the -v option:
auth_type The type of authentication to use.
fqdn The hostname provided to login by the -h option.
hostname The name login(1) will place in the utmp file for the re-
mote hostname.
local_addr The local IP address given to login(1) by the -L option.
lastchance Set to "yes" when a user's password has expired but the
user is being given one last chance to login and update
the password.
login This is a new login session (as opposed to a simple iden-
tity check).
remote_addr The remote IP address given to login(1) by the -R option.
style The style of authentication used for this user (see ap-
proval scripts below).
The su(1) program provides the following through the -v option:
invokinguser Set to the name of the user being authenticated; used for
Kerberos authentication.
wheel Set to either "yes" or "no" to indicate if the user is in
group wheel when they are trying to become root. Some au-
thentication types require the user to be in group wheel
when using the su(1) program to become super user.
When the authentication program is executed, the environment will only
contain the values PATH=/bin:/usr/bin and SHELL=/bin/sh. File descriptor
3 will be open for reading and writing. The authentication program should
write one or more of the following strings to this file descriptor:
authorize The user has been authorized.
authorize secure
The user has been authorized and root should be allowed to lo-
gin even if this is not a secure terminal. This should only be
sent by authentication styles that are secure over insecure
lines.
reject Authorization is rejected. This overrides any indication that
the user was authorized (though one would question the wisdom
in sending both a reject and an authorize command).
reject challenge
Authorization was rejected and a challenge has been made
available via the value challenge.
reject silent
Authorization is rejected, but no error messages should be
generated.
remove file
If the login session fails for any reason, remove file before
termination (a kerberos ticket file, for example).
setenv name value
If the login session succeeds, the environment variable name
should be set to the specified value.
unsetenv name
If the login session succeeds, the environment variable name
should be removed.
value name value
Set the internal variable name to the specified value. The
value should only contain printable characters. Several \ se-
quences may be used to introduce non printing characters.
These are:
\n A newline.
\r A carriage return.
\t A tab.
\xxx The character represented by the octal value xxx. The
value may be one, two, or three octal digits.
\c The string is replaced by the value of c. This allows
quoting an initial space or the \ character itself.
The following values are currently defined:
challenge
See section on challenges below.
errormsg
If set, the value is the reason authentication failed.
The calling program may choose to display this when
rejecting the user, but display is not required.
In order for authentication to be successful, the authentication program
must exit with a value of 0 as well as provide an authorize or authorize
root statement on file descriptor 3.
An authentication program must not assume it will be called as root, nor
must it assume it will not be called as root. If it needs special permis-
sions to access files it should be setuid or setgid to the appropriate
user/group. See chmod(1).
When an authentication program is called with a service of challenge it
should do one of three things:
If this style of authentication supports challenge response it should set
the internal variable challenge to be the appropriate challenge for the
user. This is done by the value command listed above. The program should
also issue a reject challenge and then exit with a 0 status. See the sec-
tion on responses below.
If this style of authentication does not support challenge response, but
does support the response service (described below) it should issue
reject silent and then exit with a 0 status.
If this style of authentication does not support the response service it
should simply fail, complaining about an unknown service type. It should
exit with a non-zero status.
When an authentication program is called with a service of response, and
this style supports this mode of authentication, it should read two null
terminated strings from file descriptor 3. The first string is a chal-
lenge that was issued to the user (obtained from the challenge service
above). The second string is the response the user gave (i.e., the pass-
word). If the response is correct for the specified challenge, the au-
thentication should be accepted, else it should be rejected. It is possi-
ble for the challenge to be any empty string, which implies the calling
program did first obtain a challenge prior to getting a response from the
user. Not all authentication styles support empty challenges.
An approval program has the synopsis of:
approve [-v name=value] username class service
Just as with an authentication program, file descriptor 3 will be open
for writing when the approval program is executed. The -v option is the
same as in the authentication program. Unlike an authentication program,
the approval program need not explicitly send an authorize or authorize
root statement, it only need exit with a value of 0 or non-zero. An exit
value of 0 is equivalent to an authorize statement, and non-zero to a
reject statement. This allows for simple programs which have no informa-
tion to provide other than approval or denial.
A classify program has the synopsis of:
classify [-v name=value] [-f] [user]
See login(1) for a description of the -f, option. The -v option is the
same as for the authentication programs. The user is the username passed
to login(1) login, if any.
The typical job of the classify program is to determine what authentica-
tion type should actually be used, presumably based on the remote IP ad-
dress. It might also re-specify the hostname to be included in the
utmp(5) file, reject the login attempt outright, or even print an addi-
tional login banner (e.g., /etc/issue).
The classify entry is only valid for the default class as it is used pri-
or to knowing who the user is. The classify script may pass environment
variables or other commands back to login(1) on file descriptor 3, just
as an authentication program does. The two variables AUTH_TYPE and
REMOTE_NAME are used to specify a new authentication type (the type must
have the form auth-type) and override the -h option to login, respective-
ly.
cap_mkdb(1), login(1), authenticate(3), bsd_auth(3), getcap(3),
login_cap(3), passwd(5), ttys(5), ftpd(8)
MirBSD #10-current June 18, 2001 8