#!/usr/bin/perl
#
# lcuseradd
#
# Scott Harrison
# October 27, 2000

use strict;

# 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 user entries to
# /etc/passwd and /etc/groups.
# Passwords are set with lcpasswd.
# www becomes a member of this user group.

# Standard input 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.

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

# These are the exit codes.

# Security
$ENV{'PATH'}=""; # Nullify path information.
$ENV{'BASH_ENV'}=""; # Nullify shell environment information.

# Do not print error messages if there are command-line arguments
my $noprint=0;
if (@ARGV) {
    $noprint=1;
}

# Read in /etc/passwd, and make sure this process is running from user=www
open (IN, "</etc/passwd");
my @lines=<IN>;
close IN;
my $wwwid;
for my $l (@lines) {
    chop $l;
    my @F=split(/\:/,$l);
    if ($F[0] eq 'www') {$wwwid=$F[2];}
}
if ($wwwid!=$<) {
    print("User ID mismatch.  This program must be run as user 'www'\n") unless $noprint;
    exit 1;
}
&disable_root_capability;

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

# Gather input.  Should be 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 {chop} @input;
}

my ($username,$password1,$password2)=@input;
$username=~/^(\w+)$/;
my $safeusername=$1;

if ($password1 ne $password2) {
    print "Error. Password mismatch.\n";
    unlink('/tmp/lock_lcpasswd');
    exit 7;
}

&enable_root_capability;

# Add user entry to /etc/passwd and /etc/groups in such
# a way that www is a member of the user-specific group

if (system('/usr/sbin/useradd','-c','LON-CAPA user',$safeusername)) {
    print "Error.  Something went wrong with the addition of user \"$safeusername\".\n";
    unlink('/tmp/lock_lcpasswd');
    exit 5;
}
if (system('/usr/sbin/usermod','-G',$safeusername,'www')) {
    print "Error. Could not make www a member of the group \"$safeusername\".\n";
    unlink('/tmp/lock_lcpasswd');
    exit 6;
}

# Set password with lcpasswd-style algorithm (which creates smbpasswd entry).
# I cannot place a direct shell call to lcpasswd since I have to allow
# for crazy characters in the password, and the setuid environment of perl
# requires me to make everything safe.



# ----------------------------------------------------------- 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;
}