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#!/usr/bin/perl

# The Learning Online Network with CAPA
#
# lcuseradd - LON-CAPA setuid script to coordinate all actions
#             with adding a user with filesystem privileges (e.g. author)
#
# YEAR=2000
# 10/27,10/29,10/30 Scott Harrison
# YEAR=2001
# 10/21,11/13,11/15 Scott Harrison
#
# $Id: lcuseradd,v 1.18 2001/11/16 06:18:35 harris41 Exp $
###

###############################################################################
##                                                                           ##
## ORGANIZATION OF THIS PERL SCRIPT                                          ##
##                                                                           ##
## 1. Description of script                                                  ##
## 2. Invoking script (standard input)                                       ##
## 3. Example usage inside another piece of code                             ##
## 4. Description of functions                                               ##
## 5. Exit codes                                                             ##
## 6. Initializations                                                        ##
## 7. Make sure this process is running from user=www                        ##
## 8. Start running script with www permissions                              ##
## 9. Handle case of another lcpasswd process (locking)                      ##
## 10. Error-check input, need 3 values (user name, password 1, password 2)  ##
## 11. Start running script with root permissions                            ##
## 12. Add user and make www a member of the user-specific group             ##
## 13. Set password                                                          ##
## 14. Make final modifications to the user directory                        ##
## 15. Exit script (unlock)                                                  ##
##                                                                           ##
###############################################################################

use strict;

# ------------------------------------------------------- Description of script
#
# This script is a setuid script that should
# be run by user 'www'.  It creates a /home/USERNAME directory
# as well as a /home/USERNAME/public_html directory.
# It adds a user to the unix system.
# Passwords are set with lcpasswd.
# www becomes a member of this user group.

# -------------- Invoking script (standard input versus command-line arguments)
#
# Standard input (STDIN) usage
# First line is USERNAME
# Second line is PASSWORD
# Third line is PASSWORD
#
# Command-line arguments [USERNAME] [PASSWORD] [PASSWORD]
# Yes, but be very careful here (don't pass shell commands)
# and this is only supported to allow perl-system calls.
#
# Valid passwords must consist of the
# ascii characters within the inclusive
# range of 0x20 (32) to 0x7E (126).
# These characters are:
# SPACE and
# !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO
# PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
#
# Valid user names must consist of ascii
# characters that are alphabetical characters
# (A-Z,a-z), numeric (0-9), or the underscore
# mark (_). (Essentially, the perl regex \w).
# User names must begin with an alphabetical character
# (A-Z,a-z).

# ---------------------------------- Example usage inside another piece of code
# Usage within code
#
# $exitcode=
#      system("/home/httpd/perl/lcuseradd","NAME","PASSWORD1","PASSWORD2")/256;
# print "uh-oh" if $exitcode;

# ---------------------------------------------------- Description of functions
# enable_root_capability() : have setuid script run as root
# disable_root_capability() : have setuid script run as www
# try_to_lock() : make sure that another lcpasswd process isn't running

# ------------------------------------------------------------------ Exit codes
# These are the exit codes.
# ( (0,"ok"),
# (1,"User ID mismatch.  This program must be run as user 'www'"),
# (2,"Error. This program needs 3 command-line arguments (username, ".
#    "password 1, password 2)."),
# (3,"Error. Three lines should be entered into standard input."),
# (4,"Error. Too many other simultaneous password change requests being ".
#    "made."),
# (5,"Error. User $username does not exist."),
# (6,"Error. Could not make www a member of the group \"$safeusername\"."),
# (7,"Error. Root was not successfully enabled.),
# (8,"Error. Cannot set password."),
# (9,"Error. The user name specified has invalid characters."),
# (10,"Error. A password entry had an invalid character."),
# (11,"Error. User already exists.),
# (12,"Error. Something went wrong with the addition of user ".
#     "\"$safeusername\"."),
# (13,"Error. Password mismatch."),

# ------------------------------------------------------------- Initializations
# Security
$ENV{'PATH'}='/bin/:/usr/bin:/usr/local/sbin:/home/httpd/perl'; # Nullify path
                                                                # information
delete @ENV{qw(IFS CDPATH ENV BASH_ENV)}; # nullify potential taints

# Do not print error messages.
my $noprint=1;

# ----------------------------- Make sure this process is running from user=www
my $wwwid=getpwnam('www');
&disable_root_capability;
if ($wwwid!=$>) {
    print("User ID mismatch.  This program must be run as user 'www'\n")
	unless $noprint;
    exit 1;
}

# ----------------------------------- Start running script with www permissions
&disable_root_capability;

# --------------------------- Handle case of another lcpasswd process (locking)
unless (&try_to_lock("/tmp/lock_lcpasswd")) {
    print "Error. Too many other simultaneous password change requests being ".
	"made.\n" unless $noprint;
    exit 4;
}

# ------- Error-check input, need 3 values (user name, password 1, password 2).
my @input;
if (@ARGV==3) {
    @input=@ARGV;
}
elsif (@ARGV) {
    print("Error. This program needs 3 command-line arguments (username, ".
	  "password 1, password 2).\n") unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 2;
}
else {
    @input=<>;
    if (@input!=3) {
	print("Error. Three lines should be entered into standard input.\n")
	    unless $noprint;
	unlink('/tmp/lock_lcpasswd');
	exit 3;
    }
    map {chomp} @input;
}

my ($username,$password1,$password2)=@input;
$username=~/^(\w+)$/;
my $safeusername=$1;
if (($username ne $safeusername) or ($safeusername!~/^[A-Za-z]/)) {
    print "Error. The user name specified has invalid characters.\n"
	unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 9;
}
my $pbad=0;
map {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}} (split(//,$password1));
map {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}} (split(//,$password2));
if ($pbad) {
    print "Error. A password entry had an invalid character.\n";
    unlink('/tmp/lock_lcpasswd');
    exit 10;
}

# -- Only add user if we can create a brand new home directory (/home/username)
if (-e "/home/$safeusername") {
    print "Error. User already exists.\n" unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 11;
}

# -- Only add user if the two password arguments match.
if ($password1 ne $password2) {
    print "Error. Password mismatch.\n" unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 13;
}

# ---------------------------------- Start running script with root permissions
&enable_root_capability;

# ------------------- Add user and make www a member of the user-specific group
# -- Add user
if (system('/usr/sbin/useradd','-c','LON-CAPA user',$safeusername)) {
    print "Error.  Something went wrong with the addition of user ".
	  "\"$safeusername\".\n" unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 12;
}

# Make www a member of that user group.
my $groups=`/usr/bin/groups www` or exit(6);
chomp $groups; $groups=~s/^\S+\s+\:\s+//;
my @grouplist=split(/\s+/,$groups);
my @ugrouplist=grep {!/www|$safeusername/} @grouplist;
my $gl=join(',',(@ugrouplist,$safeusername));
if (system('/usr/sbin/usermod','-G',$gl,'www')) {
    print "Error. Could not make www a member of the group ".
	  "\"$safeusername\".\n" unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 6;
}

# ---------------------------------------------------------------- Set password
# Set password with lcpasswd (which creates smbpasswd entry).

unlink('/tmp/lock_lcpasswd');
&disable_root_capability;
($>,$<)=($wwwid,$wwwid);
open OUT,"|/home/httpd/perl/lcpasswd";
print OUT $safeusername;
print OUT "\n";
print OUT $password1;
print OUT "\n";
print OUT $password1;
print OUT "\n";
close OUT;
if ($?) {
    exit 8;
}
($>,$<)=($wwwid,0);
&enable_root_capability;

# ------------------------------ Make final modifications to the user directory
# -- Add a public_html file with a stand-in index.html file

# system('/bin/chmod','-R','0660',"/home/$safeusername");
system('/bin/chmod','0710',"/home/$safeusername");
mkdir "/home/$safeusername/public_html",0755;
system('/bin/chmod','02770',"/home/$safeusername/public_html");
open OUT,">/home/$safeusername/public_html/index.html";
print OUT<<END;
<html>
<head>
<title>$safeusername</title>
</head>
<body>
<h1>$safeusername</h1>
<p>
Learning Online Network
</p>
<p>
This area provides for:
</p>
<ul>
<li>resource construction</li>
<li>resource publication</li>
<li>record-keeping</li>
</ul>
</body>
</html>
END
close OUT;
system('/bin/chown','-R',"$safeusername:$safeusername","/home/$safeusername");

# -------------------------------------------------------- Exit script
&disable_root_capability;
exit 0;

# ---------------------------------------------- Have setuid script run as root
sub enable_root_capability {
    if ($wwwid==$>) {
	($<,$>)=($>,$<);
	($(,$))=($),$();
    }
    else {
	# root capability is already enabled
    }
    return $>;
}

# ----------------------------------------------- Have setuid script run as www
sub disable_root_capability {
    if ($wwwid==$<) {
	($<,$>)=($>,$<);
	($(,$))=($),$();
    }
    else {
	# root capability is already disabled
    }
}

# ----------------------- Make sure that another lcpasswd process isn't running
sub try_to_lock {
    my ($lockfile)=@_;
    my $currentpid;
    my $lastpid;
    # Do not manipulate lock file as root
    if ($>==0) {
	return 0;
    }
    # Try to generate lock file.
    # Wait 3 seconds.  If same process id is in
    # lock file, then assume lock file is stale, and
    # go ahead.  If process id's fluctuate, try
    # for a maximum of 10 times.
    for (0..10) {
	if (-e $lockfile) {
	    open(LOCK,"<$lockfile");
	    $currentpid=<LOCK>;
	    close LOCK;
	    if ($currentpid==$lastpid) {
		last;
	    }
	    sleep 3;
	    $lastpid=$currentpid;
	}
	else {
	    last;
	}
	if ($_==10) {
	    return 0;
	}
    }
    open(LOCK,">$lockfile");
    print LOCK $$;
    close LOCK;
    return 1;
}

=head1 NAME

lcuseradd - LON-CAPA setuid script to coordinate all actions
            with adding a user with filesystem privileges (e.g. author)

=head1 DESCRIPTION

lcuseradd - LON-CAPA setuid script to coordinate all actions
            with adding a user with filesystem privileges (e.g. author)

=head1 README

lcuseradd - LON-CAPA setuid script to coordinate all actions
            with adding a user with filesystem privileges (e.g. author)

=head1 PREREQUISITES

=head1 COREQUISITES

=pod OSNAMES

linux

=pod SCRIPT CATEGORIES

LONCAPA/Administrative

=cut