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important fixes, documentation addition

#!/usr/bin/perl

# The Learning Online Network with CAPA
#
# lcpasswd - LON-CAPA setuid script to synchronously change all
#            filesystem-related passwords (samba, unix, etc)
#
# YEAR=2000
# 10/27,10/28,10/29,10/30 Scott Harrison
#
# YEAR=2001
# 10/22,10/23,11/13,11/15 Scott Harrison
#
# $Id: lcpasswd,v 1.13 2001/11/15 18:34:57 harris41 Exp $
###

###############################################################################
##                                                                           ##
## ORGANIZATION OF THIS PERL SCRIPT                                          ##
##                                                                           ##
## 1. Description of script                                                  ##
## 2. Invoking script (standard input only)                                  ##
## 3. Example usage inside another piece of code                             ##
## 4. Description of functions                                               ##
## 5. Exit codes                                                             ##
##                                                                           ##
###############################################################################

use strict;

# ------------------------------------------------------- Description of script
#
# This script is a setuid script that should
# be run by user 'www'.  This script allows
# for synchronous entry of passwords into
# both the /etc/passwd and the /etc/smbpasswd
# files.
#
# This script works under the same process control mechanism
# as lcuseradd and lcpasswd, to make sure that only one of these
# processes is running at any one time on the system.

# --------------------------------------- Invoking script (standard input only)
#
# Standard input usage
# First line is USERNAME
# Second line is CURRENT PASSWORD
# Third line is NEW PASSWORD
#
# 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).

# ---------------------------------------------------- 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, old ".
#       password, new password)."),
#   (3,"Error. Three lines need to 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. Invalid entry of current password."),
#   (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.") )

# ------------------------------------------------------------- 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;
@input=<>;
if (@input!=3) {
    print("Error. Three lines need to 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";
    unlink('/tmp/lock_lcpasswd');
    exit 9;
}
my $pbad=0;
map {if (($_<32)&&($_>126)){$pbad=1;}} (split(//,$password1));
map {if (($_<32)&&($_>126)){$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 the two password arguments match.
if ($password1 ne $password2) {
    print "Error. Password mismatch.\n" unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 13;
}

# Verify existence of user
unless(getpwnam($safeusername)) {
    print "Error. User $username does not exist.\n" unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 5;
}

&enable_root_capability;
($>,$<)=(0,0);
open OUT,"|pwchange $safeusername";
print OUT $password1;
print OUT "\n";
close OUT;
($>,$<)=(0,500);

if ($?) {
    exit 8;
}
my $userid=getpwnam($safeusername);

if (-e '/usr/bin/smbpasswd') {

    ($>,$<)=(0,0); # fool smbpasswd here to think this is not a setuid
                   # environment
    unless (-e '/etc/smbpasswd') {
	open (OUT,'>/etc/smbpasswd'); close OUT;
    }

    my $smbexist=0;
    open (IN, '</etc/smbpasswd');
    my @lines=<IN>;
    close IN;
    for my $l (@lines) {
	chop $l;
	my @F=split(/\:/,$l);
	if ($F[0] eq $username) {$smbexist=1;}
    }
    unless ($smbexist) {
	open(OUT,'>>/etc/smbpasswd');
	print OUT join(':',($safeusername,$userid,
			    'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:XXXXXXXXXXXXXX'.
			    'XXXXXXXXXXXXXXXXXX','','/home/'.$safeusername,
			    '/bin/bash')) . "\n";
	close OUT;
    }

    open(OUT,"|/usr/bin/smbpasswd -s $safeusername>/dev/null") or
	die('cannot run smbpasswd');
    print OUT $password2; print OUT "\n";
    print OUT $password2; print OUT "\n";
    close OUT;
    $<=$wwwid; # unfool the program
}

&disable_root_capability;
unlink('/tmp/lock_lcpasswd');
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

lcpasswd - LON-CAPA setuid script to synchronously change all
           filesystem-related passwords (samba, unix, etc)

=head1 DESCRIPTION

LON-CAPA setuid script to synchronously change all
filesystem-related passwords (samba, unix, etc)

=head1 README

LON-CAPA setuid script to synchronously change all
filesystem-related passwords (samba, unix, etc)

=head1 PREREQUISITES

=head1 COREQUISITES

=pod OSNAMES

linux

=pod SCRIPT CATEGORIES

LONCAPA/Administrative

=cut