File:
[LON-CAPA] /
loncom /
Attic /
lcuseradd
Revision
1.43:
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Sat Aug 10 01:15:13 2013 UTC (11 years, 5 months ago) by
raeburn
Branches:
MAIN
CVS tags:
HEAD
- Bug 1320.
- No need to create a user directory in /home/httpd/html/priv/$udom/$uname
when a unix auth user is created; one will be created automatically if an
author role is assigned.
#!/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 1.43 2013/08/10 01:15:13 raeburn 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 DOMAIN
# Third line is PASSWORD
# Fourth line is PASSWORD
# Fifth 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] [DOMAIN] [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","DOMAIN","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,$domain,$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 $noprint;
print "Domain = ".$domain."\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);
}
}
# ---------------------------------------------------- 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 $noprint;
}
#-------------------------- Exit...
#
# Write the file if the error_file is defined. Regardless
# Exit with the status code.
#
sub Exit {
my ($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
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