Technical Reference: Base Operating System and Extensions, Volume 1

loginrestrictions Subroutine

Purpose

Determines if a user is allowed to access the system.

Syntax

#include <login.h>

int loginrestrictions (Name, Mode, Tty, Msg) char * Name; int Mode; char * Tty; char ** Msg;

Note: This subroutine is not thread-safe.

The loginrestrictions subroutine determines if the user specified by the Name parameter is allowed to access the system. The Mode parameter gives the mode of account usage and the Tty parameter defines the terminal used for access. The Msg parameter returns an informational message explaining why the loginrestrictions subroutine failed.

This subroutine is unsuccessful if any of the following conditions exists:

The user's account has expired as defined by the expires user attribute.
The user's account has been locked as defined by the account_locked user attribute.
The user attempted too many unsuccessful logins as defined by the loginretries user attribute.
The user is not allowed to access the given terminal as defined by the ttys user attribute.
The user is not allowed to access the system at the present time as defined by the logintimes user attribute.
The Mode parameter is set to the S_LOGIN value or the S_RLOGIN value, and too many users are logged in as defined by the maxlogins system attribute.
The Mode parameter is set to the S_LOGIN value and the user is not allowed to log in as defined by the login user attribute.
The Mode parameter is set to the S_RLOGIN value and the user is not allowed to log in from the network as defined by the rlogin user attribute.
The Mode parameter is set to the S_SU value and other users are not allowed to use the su command as defined by the su user attribute, or the group ID of the current process cannot use the su command to switch to this user as defined by the sugroups user attribute.
The Mode parameter is set to the S_DAEMON value and the user is not allowed to run processes from the cron or src subsystem as defined by the daemon user attribute.
The terminal is locked as defined by the locktime port attribute.
The user cannot use the terminal to access the system at the present time as defined by the logintimes port attribute.
The user is not the root user and the /etc/nologin file exists.

Note: The loginrestrictions subroutine is not safe in a multi-threaded environment. To use loginrestrictions in a threaded application, the application must keep the integrity of each thread.

Parameters

Name	Specifies the user's login name whose account is to be validated.
Mode	Specifies the mode of usage. Valid values as defined in the login.h file are listed below. The Mode parameter has a value of 0 or one of the following values: S_LOGIN Verifies that local logins are permitted for this account. S_SU Verifies that the su command is permitted and the current process has a group ID that can invoke the su command to switch to the account. S_DAEMON Verifies the account can invoke daemon or batch programs through the src or cron subsystems. S_RLOGIN Verifies the account can be used for remote logins through the rlogind or telnetd programs.
Tty	Specifies the terminal of the originating activity. If this parameter is a null pointer or a null string, no tty origin checking is done.
Msg	Returns an informative message indicating why the loginrestrictions subroutine failed. Upon return, the value is either a pointer to a valid string within memory allocated storage or a null value. If a message is displayed, it is provided based on the user interface.

Security

Access Control:The calling process must have access to the account information in the user database and the port information in the port database.

File Accessed:

Mode	Files
r	/etc/security/user
r	/etc/security/login.cfg
r	/etc/security/portlog
r	/etc/passwd

Return Values

If the account is valid for the specified usage, the loginrestrictions subroutine returns a value of 0. Otherwise, a value of -1 is returned, the errno global value is set to the appropriate error code, and the Msg parameter returns an informative message explaining why the specified account usage is invalid.

Error Codes

The loginrestrictions subroutine fails if one or more of the following values is true:

ENOENT	The user specified does not have an account.
ESTALE	The user's account is expired.
EPERM	The user's account is locked, the specified terminal is locked, the user has had too many unsuccessful login attempts, or the user cannot log in because the /etc/nologin file exists.
EACCES	One of the following conditions exists: The specified terminal does not have access to the specified account. The Mode parameter is the S_SU value and the current process is not permitted to use the su command to access the specified user. Access to the account is not permitted in the specified mode. Access to the account is not permitted at the current time. Access to the system with the specified terminal is not permitted at the current time.
EAGAIN	The Mode parameter is either the S_LOGIN value or the S_RLOGIN value, and all the user licenses are in use.
EINVAL	The Mode parameter has a value other than S_LOGIN, S_SU, S_DAEMON, S_RLOGIN, or 0.

Implementation Specifics

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

Related Information

The authenticate (authenticate Subroutine) subroutine, getpcred (getpcred Subroutine) subroutine, getpenv (getpenv Subroutine) subroutine, loginfailed (loginfailed Subroutine) subroutine, loginsuccess (loginsuccess Subroutine) subroutine, setpcred subroutine, setpenv subroutine.

The cron daemon.

The login command, rlogin command, telnet, tn, or tn3270 command, su command.

List of Security and Auditing Subroutines in AIX 5L Version 5.1 General Programming Concepts: Writing and Debugging Programs.

Subroutines, Example Programs, and Libraries in AIX 5L Version 5.1 General Programming Concepts: Writing and Debugging Programs.