--- loncom/Attic/lcuseradd 2000/10/29 22:20:43 1.3 +++ loncom/Attic/lcuseradd 2006/08/25 21:25:22 1.39 @@ -1,42 +1,519 @@ #!/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) # -# lcuseradd # -# Scott Harrison -# October 27, 2000 +# $Id: lcuseradd,v 1.39 2006/08/25 21:25:22 albertel 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 -# as well as a /home/USERNAME/public_html directory. -# It adds user entries to -# /etc/passwd and /etc/groups. +# 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. -# Standard input usage +# -------------- 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 PASSWORD # Third line is PASSWORD - +# Fouth 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] [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","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'}=""; # Nullify path information. -$ENV{'BASH_ENV'}=""; # Nullify shell environment information. +$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,$password1,$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 $noprint; + +if (($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 -# Add user entry to /etc/passwd and /etc/groups in such -# a way that www is a member of the user-specific group +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); +} -# useradd [-c comment] [-d home_dir] -# [-e expire_date] [-f inactive_time] -# [-g initial_group] [-G group[,...]] -# [-m [-k skeleton_dir] | -M] [-p passwd] -# [-s shell] [-u uid [ -o]] [-n] [-r] login -system('/usr/sbin/useradd','-c','LON-CAPA user','-G','www','junk'); +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 $noprint; + unlink('/tmp/lock_lcpasswd'); + &Exit(15); + } +} + +# ------------------------------ Make final modifications to the user directory +# -- Add a public_html file with a stand-in index.html file + +if (-d "/home/$safeusername") { + system('/bin/chmod','-R','0660',"/home/$safeusername"); + system('/bin/chmod','0710',"/home/$safeusername"); + mkdir "/home/$safeusername/public_html",0755; + open OUT,">/home/$safeusername/public_html/index.html"; + print OUT< + +$safeusername + + +

Construction Space

+

$safeusername

+ + +END +close OUT; +} + +# +# In order to allow the loncapa daemons appropriate access +# to public_html, Top level and public_html directories should +# be owned by safeusername:safeusername as should the smaple index.html.. +print "lcuseradd ownership\n" unless $noprint; +system('/bin/chown','-R',"$safeusername:$safeusername","/home/$safeusername"); # First set std ownership on everything. +&set_public_html_permissions("/home/$safeusername/public_html"); +# system('/bin/chown',"$safeusername:www","/home/$safeusername"); # Now adust top level... +# system('/bin/chown','-R',"$safeusername:www","/home/$safeusername/public_html"); # And web dir. +# ---------------------------------------------------- Gracefull Apache Restart +if (-e '/var/run/httpd.pid') { + print "lcuseradd Apache restart\n" unless $noprint; + open(PID,'/var/run/httpd.pid'); + my $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 + } + 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"); + $currentpid=; + close LOCK; + if ($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 $noprint; + +} +# +# Set up the correct permissions for all files in the +# user's public htmldir. We just do a chmod -R 0660 ... for +# the ordinary files. The we use File::Find +# to pop through the directory tree changing directories only +# to 02770: +# +sub set_public_html_permissions { + my ($topdir) = @_; + + # Set the top level dir permissions (I'm not sure if find + # will enumerate it specifically), correctly and all + # files and dirs to the 'ordinary' file permissions: + + system("chmod -R 0660 $topdir"); + chmod(02770, $topdir); + + # Now use find to locate all directories under $topdir + # and set their modes to 02770... + # + print "Find file\n " unless $noprint; + File::Find::find({"untaint" => 1, + "untaint_pattern" => qr(/^(.*)$/), + "untaint_skip" => 1, + "no_chdir" => 1, + "wanted" => \&set_permission }, "$topdir"); + + +} + +#-------------------------- Exit... +# +# Write the file if the error_file is defined. Regardless +# Exit with the status code. +# +sub Exit { + my ($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