login.cfg File

AIX Version 4 Files Reference

login.cfg File

Purpose

Contains configuration information for login and user authentication.

Description

The /etc/security/login.cfg file is an ASCII file that contains stanzas of configuration information for login and user authentication. Each stanza has a name, followed by a : (colon), that defines its purpose. Attributes are in the form Attribute=Value. Each attribute ends with a new-line character, and each stanza ends with an additional new-line character. For an example of a stanza, see the "Examples" section.

There are three types of stanzas:

port	Defines the login characteristics of ports.
authentication method	Defines the authentication methods for users.
user configuration	Defines programs that change user attributes.

Port Stanzas

Port stanzas define the login characteristics of ports and are named with the full path name of the port. Each port should have its own separate stanza. Each stanza has the following attributes:

herald

Defines the login message printed when the getty process opens the port. The default herald is the login prompt. The value is a character string.

herald2

Defines the login message printed after a failed login attempt. The default herald is the login prompt. The value is a character string.

logindelay

Defines the delay factor (in seconds) between unsuccessful login attempts. The value is a decimal integer string. The default value is 0, indicating no delay between unsuccessful login attempts.

logindisable

Defines the number of unsuccessful login attempts allowed before the port is locked. The value is a decimal integer string. The default value is 0, indicating that the port cannot lock as a result of unsuccessful login attempts.

logininterval

Defines the time interval (in seconds) in which the specified unsuccessful login attempts must occur before the port is locked. The value is a decimal integer string. The default value is 0.

loginreenable

Defines the time interval (in minutes) a port is unlocked after a system lock. The value is a decimal integer string. The default value is 0, indicating that the port is not automatically unlocked.

logintimes

Specifies the times, days, or both the user is allowed to access the system. The value is a comma-separated list of entries of the following form:

[!]:time-time
   -or-
[!]day[-day][:time-time]
   -or-
[!]date[-date][:time-time]

The day variable must be one digit between 0 and 6 that represents one of the days of the week. A 0 (zero) indicates Sunday and a 6 indicates Saturday.

The time variable is 24-hour military time (1700 is 5:00 p.m.). Leading zeroes are required. For example, you must enter 0800, not 800. The time variable must be four characters in length, and there must be a leading colon (:). An entry consisting of only a time specification applies to every day. The start hour of a time value must be less than the end hour.

The date variable is a four digit string in the form mmdd. mm represents the calendar month and dd represents the day number. For example 0001 represents January 1. dd may be 00 to indicate the entire month, if the entry is not a range, or indicating the first or last day of the month depending on whether it appears as part of the start or end of a range. For example, 0000 indicates the entire month of January. 0600 indicates the entire month of June. 0311-0500 indicates April 11 through the last day of June.

Entries in this list specify times that a user is allowed or denied access to the system. Entries not preceded by an exclamation point (!) allow access and are called ALLOW entries. Entries prefixed with an exclamation point (!) deny access to the system and are called DENY entries. The ! operator applies to only one entry, not the whole restriction list. It must appear at the beginning of an entry.

sak_enabled

Defines whether the secure attention key (SAK) is enabled for the port. The SAK key is the Ctrl-X, Ctrl-R key sequence. Possible values for the sak_enabled attribute are:

true	SAK processing is enabled, so the key sequence establishes a trusted path for the port.
false	SAK processing is not enabled, so a trusted path cannot be established. This is the default value.

The sak_enabled stanza can also be modified to close a potential security exposure that exists when tty login devices are writable by others; for example, when the tty mode is 0622. If the sak_enabled stanza is set to True, the tty mode is set to a more restrictive 0600 at login. If the sak_enabled stanza is set to False (or absent), the tty mode is set to 0622.

synonym

Defines other path names for the terminal. This attribute revokes access to the port and is used only for trusted path processing. The path names should be device special files with the same major and minor number and should not include hard or symbolic links. The value is a list of comma-separated path names.

Synonyms are not associative. For example, if you specify synonym=/dev/tty0 in the stanza for the /dev/console path name, then the /dev/tty0 path name is a synonym for the /dev/console path name. However, the /dev/console path name is not a synonym for the /dev/tty0 path name unless you specify synonym=/dev/console in the stanza for the /dev/tty0 path name.

Authentication Method Stanzas

These stanzas define the authentication methods for users assigned in the /etc/security/user file. The name of each stanza must be identical to one of the methods defined by the auth1 or the auth2 attribute in the /etc/security/user file.

Each stanza has one attribute:

program

Contains the full path name of a program that provides primary or secondary authentication for a user. Program flags and parameters may be included.

Since the SYSTEM authentication method is supported directly by the login command and the su command, and the NONE method does not provide any authentication, neither requires definition. However, all other authentication methods must be defined in this file. Different authentication methods can be defined for each user.

User-Configuration Stanzas

User-configuration stanzas provide configuration information for programs that change user attributes. There is one user-configuration stanza: usw.

Note: Password restrictions have no effect if you are on a network using Network Information Services (NIS). See "Network Information Service (NIS) Overview for System Management" in AIX Version 4.3 System Management Guide: Communications and Networks for a description of NIS.

The usw stanza defines the configuration of miscellaneous facilities. The following attributes can be included:

logintimeout	Defines the time (in seconds) the user is given to type the password. The value is a decimal integer string. The default is a value of 60.
maxlogins	Defines the maximum number of simultaneous logins to the system. The format is a decimal integer string. The default value varies depending on the specific machine license. A value of 0 indicates no limit on simultaneous login attempts. Note: Login sessions include rlogins and telnets; these are counted against the maximum allowable number of simultaneous logins by the maxlogins attribute.
shells	Defines the valid shells on the system. This attribute is used by the chsh command to determine which shells a user can select. The value is a list of comma-separated full path names. The default is /usr/bin/sh, /usr/bin/bsh, /usr/bin/csh, /usr/bin/ksh, or /usr/bin/tsh.

Security

Access Control: This command should grant read (r) and write (w) access to the root user and members of the security group.

Auditing Events:

Event	Information
S_LOGIN_WRITE	File name

Examples

A typical authentication_method stanza looks like the following:
```
meth1:
  program = /bin/auth_meth1 
```

A typical port stanza looks like the following:

/dev/tty0:
  sak_enabled = true
  herald = "login to tty0:"

Implementation Specifics

This command is part of Base Operating System (BOS) Runtime.

Files

/etc/security/login.cfg	Specifies the path to the file.
/etc/group	Contains the basic attributes of groups.
/etc/security/group	Contains the extended attributes of groups.
/etc/passwd	Contains the basic attributes of users.
/etc/security/passwd	Contains password information.
/etc/security/user	Contains the extended attributes of users.
/etc/security/environ	Contains the environment attributes of users.
/etc/security/limits	Contains the process resource limits of users.
/etc/security/audit/config	Contains audit system configuration information.
/etc/security/lastlog	Contains last login information.

Related Information

The chfn command, chsec command, chsh command, login command, passwd command, pwdadm command, su command.

The newpass subroutine.

Security Administration in AIX Version 4.3 System Management Guide: Operating System and Devices.