#!/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)
#
#
# $Id: lcuseradd,v 1.41 2007/03/28 20:43:37 albertel 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;
use File::Find;


# ------------------------------------------------------- Description of script
#
# This script is a setuid script that should
# be run by user 'www'.  It creates a /home/USERNAME 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)
#                Otherwise sensitive information will be available to ps-ers for
#                a small but exploitable time window.
#
# Standard input (STDIN) usage
# First line is USERNAME
# Second line is PASSWORD
# Third line is PASSWORD
# Fouth line is the name of a file to which an error code will be written.
#            If the fourth line is omitted, no error file will be written.
#            In either case, the program Exits with the code as its Exit status.
#            The error file will just be a single line containing an
#            error code.
#            
#  
#
# 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."),
# (14, "Error filename is invalid"),
# (15, "Error. Could not add home directory.")

# ------------------------------------------------------------- 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;

print "In lcuseradd\n" unless $noprint;

# ----------------------------- 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 at least 3 command-line arguments (username, ".
	  "password 1, password 2 [errorfile]).\n") unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    &Exit(2);
} else {
    @input=<>;
    if (@input < 3) {
	print("Error. At least three lines should be entered into standard input.\n")
	    unless $noprint;
	unlink('/tmp/lock_lcpasswd');
	&Exit(3);
    }
    foreach (@input) {chomp;}
}

my ($username,$password1,$password2, $error_file)=@input;
print "Username = ".$username."\n" unless $noprint;
$username=~/^(\w+)$/;
print "Username after substitution - ".$username unless $noprint;
my $safeusername=$1;
print "Safe username = $safeusername \n" unless $noprint;

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

#
#   Safe the filename.  For our case, it must only have alpha, numeric, period
#   and path sparators..
#

print "Error file is $error_file \n" unless $noprint;

if($error_file) {
    if($error_file =~ /^([(\w)(\d)\.\/]+)$/) {
	print "Error file matched pattern $error_file : $1\n" unless $noprint;
	my $safe_error_file = $1;	# Untainted I think.
	print "Error file after transform $safe_error_file\n"
	    unless $noprint;
	if($error_file == $safe_error_file) {
	    $error_file = $safe_error_file; # untainted error_file.
	} else {
	    $error_file ="";
	    print "Invalid error filename\n" unless $noprint;
	    Exit(14);
	}

    } else {
	$error_file="";
	print "Invalid error filename\n" unless $noprint;
	Exit(14);
    }
}


# -- Only add the user if they are >not< in /etc/passwd.
#    Used to look for the ability to create a new directory for the
#    user, however that disallows authentication changes from i
#    internal->fs.. so just check the passwd file instead.
#
my $not_found = system("cut -d: -f1 /etc/passwd | grep -q \"^$safeusername\$\" ");
if (!$not_found) {
    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);
}
print "enabling root\n" unless $noprint;
# ---------------------------------- Start running script with root permissions
&enable_root_capability;

# ------------------- Add group and user, and make www a member of the group
# -- Add group

print "adding group: $safeusername \n" unless $noprint;
my $status = system('/usr/sbin/groupadd', $safeusername);
if ($status) {
    print "Error.  Something went wrong with the addition of group ".
          "\"$safeusername\".\n" unless $noprint;
    print "Final status of groupadd = $status\n";
    unlink('/tmp/lock_lcpasswd');
    &Exit(12);
}
my $gid = getgrnam($safeusername);
                                                                                
# -- Add user

print "adding user: $safeusername \n" unless $noprint;
my $status = system('/usr/sbin/useradd','-c','LON-CAPA user','-g',$gid,$safeusername);
if ($status) {
    print "Error.  Something went wrong with the addition of user ".
	  "\"$safeusername\".\n" unless $noprint;
    system("/usr/sbin/groupdel $safeusername");
    print "Final status of useradd = $status\n";
    unlink('/tmp/lock_lcpasswd');
    &Exit(12);
}

print "Done adding user\n" unless $noprint;
# Make www a member of that user group.
my $groups=`/usr/bin/groups www` or &Exit(6);
# untaint
my ($safegroups)=($groups=~/:\s*([\s\w]+)/);
$groups=$safegroups;
chomp $groups; $groups=~s/^\S+\s+\:\s+//;
my @grouplist=split(/\s+/,$groups);
my @ugrouplist=grep {!/www|$safeusername/} @grouplist;
my $gl=join(',',(@ugrouplist,$safeusername));
print "Putting www in user's group\n" unless $noprint;
if (system('/usr/sbin/usermod','-G',$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);
print "Opening lcpasswd pipeline\n" unless $noprint;
open OUT,"|/home/httpd/perl/lcpasswd";
print OUT $safeusername;
print OUT "\n";
print OUT $password1;
print OUT "\n";
print OUT $password1;
print OUT "\n";
close OUT;
if ($?) {
    print "abnormal Exit from close lcpasswd\n" unless $noprint;
    &Exit(8);
}
($>,$<)=($wwwid,0);
&enable_root_capability;

# Check if home directory exists for user
# If not, create one.
if (!-e "/home/$safeusername") {
    if (!mkdir("/home/$safeusername",0710)) {
        print "Error. Could not add home directory for ".
          "\"$safeusername\".\n" unless $noprint;
        unlink('/tmp/lock_lcpasswd');
        &Exit(15);
    }
}

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

if (-d "/home/$safeusername") {
    system('/bin/chmod','-R','0660',"/home/$safeusername");
    system('/bin/chmod','0710',"/home/$safeusername");
    mkdir "/home/$safeusername/public_html",0755;
    open OUT,">/home/$safeusername/public_html/index.html";
    print OUT<<END;
<html>
<head>
<title>$safeusername</title>
</head>
<body>
<h1>Construction Space</h1>
<h3>$safeusername</h3>
</body>
</html>
END
close OUT;
}

#
#   In order to allow the loncapa daemons appropriate access
#   to public_html, Top level and public_html directories should
#   be owned by safeusername:safeusername as should the smaple index.html..
print "lcuseradd ownership\n" unless $noprint;
system('/bin/chown','-R',"$safeusername:$safeusername","/home/$safeusername"); # First set std ownership on everything.
&set_public_html_permissions("/home/$safeusername/public_html");
#  system('/bin/chown',"$safeusername:www","/home/$safeusername");	# Now adust top level...
#  system('/bin/chown','-R',"$safeusername:www","/home/$safeusername/public_html"); # And web dir.
# ---------------------------------------------------- Gracefull Apache Restart
my $pidfile;
if (-e '/var/run/httpd.pid') {
    $pidfile = '/var/run/httpd.pid';
} elsif (-e '/var/run/httpd2.pid') {   #Apache 2 on SuSE 10.1 and SLES10 
    $pidfile = '/var/run/httpd2.pid';
} 

if ($pidfile) {
    print "lcuseradd Apache restart\n" unless $noprint;
    open(PID,"<$pidfile");
    my $pid=<PID>;
    close(PID);
    $pid=~ /(\D+)/;
    my $safepid = $1;
    if ($pid) {
	system('kill','-USR1',"$safepid");
    }
}
# -------------------------------------------------------- Exit script
print "lcuseradd Exiting\n" unless $noprint;
&disable_root_capability;
&Exit(0);

# ---------------------------------------------- Have setuid script run as root
sub enable_root_capability {
    if ($wwwid==$>) {
	($<,$>)=($>,0);
	($(,$))=($),0);
    } else {
	# root capability is already enabled
    }
    if ($wwwid == $>) {
	print("Failed to become root\n") unless $noprint;
    } else {
	print("Became root\n") unless $noprint;
    }
    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;
}
#    Called by File::Find::find for each file examined.
#
#     Untaint the file and, if it is a directory,
#     chmod it to 02770
#
sub set_permission {
    $File::Find::name =~ /^(.*)$/;
    my $safe_name = $1;		# Untainted filename...
    
    print "$safe_name" unless $noprint;
    if(-d $safe_name) {
	print " - directory" unless $noprint;
	chmod(02770, $safe_name);
    }
    print "\n" unless $noprint;

}
#
#    Set up the correct permissions for all files in the 
#    user's public htmldir. We just do a chmod -R 0660 ... for
#    the ordinary files.  The we use File::Find
#    to pop through the directory tree changing directories only
#    to 02770:
#
sub set_public_html_permissions {
    my ($topdir) = @_;

    #   Set the top level dir permissions (I'm not sure if find 
    #   will enumerate it specifically), correctly and all
    #   files and dirs to the 'ordinary' file permissions:

    system("chmod -R 0660 $topdir");
    chmod(02770, $topdir);

    #  Now use find to locate all directories under $topdir
    #  and set their modes to 02770...
    #
    print "Find file\n " unless $noprint;
    File::Find::find({"untaint"         => 1,
		      "untaint_pattern" => qr(/^(.*)$/),
		      "untaint_skip"    => 1,
		      "no_chdir"         => 1,
		      "wanted"          => \&set_permission }, "$topdir");


}

#-------------------------- Exit...
#
#   Write the file if the error_file is defined.  Regardless
#   Exit with the status code.
#
sub Exit {
    my ($code) = @_;		# Status code.

    # TODO: Ensure the error file is owned/deletable by www:www:

    &disable_root_capability();	# We run unprivileged to write the error file.

    print "Exiting with status $code error file is $error_file\n" unless $noprint;
    if($error_file) {
	open(FH, ">$error_file");
	print FH  "$code\n";
	close(FH);
    }
    exit $code;
}

=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