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#!/usr/bin/perl
#
# lcuserdel
#

use strict;

# $Id: lcuserdel,v 1.16 2007/08/22 19:53:22 albertel Exp $

# This script is a setuid script (chmod 6755) that should
# be run by user 'www'.  It DOES NOT delete directories.
# All it does is remove a user's entries from
# /etc/passwd, /etc/groups, and /etc/smbpasswd.
# It also disables user directory access by making the directory
# to be owned by user=www (as opposed to the former "username").
# This command only returns an error if it is
# invoked incorrectly (by passing bad command-line arguments, etc).

# 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.

# Standard input usage
# First line is USERNAME

# 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).

# Command-line arguments [USERNAME]
# 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/lcuserdel","NAME")/256;
# print "uh-oh" if $exitcode;

# These are the exit codes.
# ( (0,"ok"),
#   (1,"User ID mismatch.  This program must be run as user 'www'"),
#   (2,"Error. This program needs just 1 command-line argument (username).") )
#   (3,"Error. Only one line should be entered into standard input."),
#   (4,"Error. Too many other simultaneous password change requests being made."),
#   (5,"Error. The user name specified has invalid characters.") )

# 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 only be 1 value (user name).
my @input;
if (@ARGV==1) {
    @input=@ARGV;
}
elsif (@ARGV) {
    print("Error. This program needs just 1 command-line argument (username).\n") unless $noprint;
    unlink('/tmp/lock_lcpasswd');
    exit 2;
}
else {
    @input=<>;
    if (@input!=1) {
	print("Error. Only one line should be entered into standard input.\n") unless $noprint;
	unlink('/tmp/lock_lcpasswd');
	exit 3;
    }
    map {chop} @input;
}

my ($username)=@input;
$username=~/^(\w+)$/;
my $safeusername=$1;
if ($username ne $safeusername) {
    print "Error. The user name specified has invalid characters.\n";
    unlink('/tmp/lock_lcpasswd');
    exit 5;
}

&enable_root_capability;

# By using the system userdel command:
# Remove entry from /etc/passwd if it exists
# Remove entry from /etc/groups if it exists
# I surround with groupdel command to make absolutely sure the group definition disappears.
system('/usr/sbin/groupdel',$safeusername); # ignore error message
system('/usr/sbin/userdel',$safeusername); # ignore error message
system('/usr/sbin/groupdel',$safeusername); # ignore error message

# Remove entry from /etc/smbpasswd if it exists
#  the safest way to do this is with smbpasswd -x
#  as that's independent of location of the smbpasswd file.
#
if (-e '/usr/bin/smbpasswd') {
  ($>,$<) = (0,0);		# fool smbpasswd to think this is not setuid.
  system('/usr/bin/smbpasswd -x '.$safeusername);
  $< = $wwwid;
}


# Change ownership on directory from username:username to www:www
# This prevents subsequently added users from having access.

system('/bin/chown','-R','www:www',"/home/$safeusername");

&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;
}