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lcuseradd
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Mon Oct 30 02:50:23 2000 UTC (23 years, 10 months ago) by
harris41
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The program is basically working with a few minor bugs
like improper directory ownership, failing to create'
index.html, inserting too many lines into /etc/passwd.
-Scott
#!/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
# 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).
# 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=$1;
if ($username ne $safeusername) {
print "Error. The user name specified has invalid characters.\n";
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 $noprint;
unlink('/tmp/lock_lcpasswd');
exit 8;
}
# Only add user if the two password arguments match.
if ($password1 ne $password2) {
print "Error. Password mismatch.\n" unless $noprint;
unlink('/tmp/lock_lcpasswd');
exit 7;
}
&enable_root_capability;
# Add user entry to /etc/passwd and /etc/groups in such
# a way that www is a member of the user-specific group
if (system('/usr/sbin/useradd','-c','LON-CAPA user',$safeusername)) {
print "Error. Something went wrong with the addition of user \"$safeusername\".\n" unless $noprint;
unlink('/tmp/lock_lcpasswd');
exit 5;
}
# Make www a member of that user group.
if (system('/usr/sbin/usermod','-G',$safeusername,'www')) {
print "Error. Could not make www a member of the group \"$safeusername\".\n" unless $noprint;
unlink('/tmp/lock_lcpasswd');
exit 6;
}
# Set password with lcpasswd-style algorithm (which creates smbpasswd entry).
# I cannot place a direct shell call to lcpasswd since I have to allow
# for crazy characters in the password, and the setuid environment of perl
# requires me to make everything safe.
# Grab the line corresponding to username
open (IN, "</etc/passwd");
@lines=<IN>;
close IN;
my ($userid,$useroldcryptpwd);
my @F; my @U;
for my $l (@lines) {
@F=split(/\:/,$l);
if ($F[0] eq $username) {($userid,$useroldcryptpwd)=($F[2],$F[1]); @U=@F;}
}
# Verify existence of user
if (!defined($userid)) {
print "Error. User $username does not exist.\n" unless $noprint;
unlink('/tmp/lock_lcpasswd');
exit 5;
}
# Construct new password entry (random salt)
my $newcryptpwd=crypt($password1,(join '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand 64, rand 64]));
$U[1]=$newcryptpwd;
my $userline=join(':',@U);
my $rootid=&enable_root_capability;
if ($rootid!=0) {
print "Error. Root was not successfully enabled.\n" unless $noprint;
unlink('/tmp/lock_lcpasswd');
exit 7;
}
open PASSWORDFILE, '>/etc/passwd' or (print("Error. Cannot open /etc/passwd.\n") && unlink('/tmp/lock_lcpasswd') && exit(8));
for my $l (@lines) {
@F=split(/\:/,$l);
if ($F[0] eq $username) {print PASSWORDFILE "$userline\n";}
else {print PASSWORDFILE "$l\n";}
}
close PASSWORDFILE;
($>,$<)=(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,$userid,'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX','','/home/'.$safeusername,'/bin/bash')) . "\n";
close OUT;
}
open(OUT,"|/usr/bin/smbpasswd -s $safeusername>/dev/null");
print OUT $password1; print OUT "\n";
print OUT $password1; print OUT "\n";
close OUT;
$<=$wwwid; # unfool the program
# Make final modifications to the user directory.
# Add a public_html file with a stand-in index.html file.
system('/bin/chmod','-R','0640',"/home/$safeusername");
system('/bin/chmod','0750',"/home/$safeusername");
mkdir "/home/$safeusername/public_html",0750;
open OUT,">/home/$safeusername/public_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>resource publication
<LI>record-keeping
</UL>
</BODY>
</HTML>
END
close OUT;
&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;
}
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