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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

    1: #!/usr/bin/perl
    2: #
    3: # lcuseradd
    4: #
    5: # Scott Harrison
    6: # October 27, 2000
    7: 
    8: use strict;
    9: 
   10: # This script is a setuid script that should
   11: # be run by user 'www'.  It creates a /home/USERNAME directory
   12: # as well as a /home/USERNAME/public_html directory.
   13: # It adds user entries to
   14: # /etc/passwd and /etc/groups.
   15: # Passwords are set with lcpasswd.
   16: # www becomes a member of this user group.
   17: 
   18: # Standard input usage
   19: # First line is USERNAME
   20: # Second line is PASSWORD
   21: # Third line is PASSWORD
   22: 
   23: # Valid passwords must consist of the
   24: # ascii characters within the inclusive
   25: # range of 0x20 (32) to 0x7E (126).
   26: # These characters are:
   27: # SPACE and
   28: # !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO
   29: # PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
   30: 
   31: # Valid user names must consist of ascii
   32: # characters that are alphabetical characters
   33: # (A-Z,a-z), numeric (0-9), or the underscore
   34: # mark (_). (Essentially, the perl regex \w).
   35: 
   36: # Command-line arguments [USERNAME] [PASSWORD] [PASSWORD]
   37: # Yes, but be very careful here (don't pass shell commands)
   38: # and this is only supported to allow perl-system calls.
   39: 
   40: # Usage within code
   41: #
   42: # $exitcode=system("/home/httpd/perl/lcuseradd","NAME","PASSWORD1","PASSWORD2")/256;
   43: # print "uh-oh" if $exitcode;
   44: 
   45: # These are the exit codes.
   46: 
   47: # Security
   48: $ENV{'PATH'}=""; # Nullify path information.
   49: $ENV{'BASH_ENV'}=""; # Nullify shell environment information.
   50: 
   51: # Do not print error messages if there are command-line arguments
   52: my $noprint=0;
   53: if (@ARGV) {
   54:     $noprint=1;
   55: }
   56: 
   57: # Read in /etc/passwd, and make sure this process is running from user=www
   58: open (IN, "</etc/passwd");
   59: my @lines=<IN>;
   60: close IN;
   61: my $wwwid;
   62: for my $l (@lines) {
   63:     chop $l;
   64:     my @F=split(/\:/,$l);
   65:     if ($F[0] eq 'www') {$wwwid=$F[2];}
   66: }
   67: if ($wwwid!=$<) {
   68:     print("User ID mismatch.  This program must be run as user 'www'\n") unless $noprint;
   69:     exit 1;
   70: }
   71: &disable_root_capability;
   72: 
   73: # Handle case of another lcpasswd process
   74: unless (&try_to_lock("/tmp/lock_lcpasswd")) {
   75:     print "Error. Too many other simultaneous password change requests being made.\n" unless $noprint;
   76:     exit 4;
   77: }
   78: 
   79: # Gather input.  Should be 3 values (user name, password 1, password 2).
   80: my @input;
   81: if (@ARGV==3) {
   82:     @input=@ARGV;
   83: }
   84: elsif (@ARGV) {
   85:     print("Error. This program needs 3 command-line arguments (username, password 1, password 2).\n") unless $noprint;
   86:     unlink('/tmp/lock_lcpasswd');
   87:     exit 2;
   88: }
   89: else {
   90:     @input=<>;
   91:     if (@input!=3) {
   92: 	print("Error. Three lines should be entered into standard input.\n") unless $noprint;
   93: 	unlink('/tmp/lock_lcpasswd');
   94: 	exit 3;
   95:     }
   96:     map {chop} @input;
   97: }
   98: 
   99: my ($username,$password1,$password2)=@input;
  100: $username=~/^(\w+)$/;
  101: my $safeusername=$1;
  102: if ($username ne $safeusername) {
  103:     print "Error. The user name specified has invalid characters.\n";
  104:     unlink('/tmp/lock_lcpasswd');
  105:     exit 9;
  106: }
  107: my $pbad=0;
  108: map {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}} (split(//,$password1));
  109: map {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}} (split(//,$password2));
  110: if ($pbad) {
  111:     print "Error. A password entry had an invalid character.\n";
  112:     unlink('/tmp/lock_lcpasswd');
  113:     exit 10;
  114: }
  115: 
  116: # Only add user if we can create a brand new home directory (/home/username).
  117: if (-e "/home/$safeusername") {
  118:     print "Error. User already exists.\n" unless $noprint;
  119:     unlink('/tmp/lock_lcpasswd');
  120:     exit 8;
  121: }
  122: 
  123: # Only add user if the two password arguments match.
  124: if ($password1 ne $password2) {
  125:     print "Error. Password mismatch.\n" unless $noprint;
  126:     unlink('/tmp/lock_lcpasswd');
  127:     exit 7;
  128: }
  129: 
  130: &enable_root_capability;
  131: 
  132: # Add user entry to /etc/passwd and /etc/groups in such
  133: # a way that www is a member of the user-specific group
  134: 
  135: if (system('/usr/sbin/useradd','-c','LON-CAPA user',$safeusername)) {
  136:     print "Error.  Something went wrong with the addition of user \"$safeusername\".\n" unless $noprint;
  137:     unlink('/tmp/lock_lcpasswd');
  138:     exit 5;
  139: }
  140: 
  141: # Make www a member of that user group.
  142: if (system('/usr/sbin/usermod','-G',$safeusername,'www')) {
  143:     print "Error. Could not make www a member of the group \"$safeusername\".\n" unless $noprint;
  144:     unlink('/tmp/lock_lcpasswd');
  145:     exit 6;
  146: }
  147: 
  148: # Set password with lcpasswd-style algorithm (which creates smbpasswd entry).
  149: # I cannot place a direct shell call to lcpasswd since I have to allow
  150: # for crazy characters in the password, and the setuid environment of perl
  151: # requires me to make everything safe.
  152: 
  153: # Grab the line corresponding to username
  154: open (IN, "</etc/passwd");
  155: @lines=<IN>;
  156: close IN;
  157: my ($userid,$useroldcryptpwd);
  158: my @F; my @U;
  159: for my $l (@lines) {
  160:     @F=split(/\:/,$l);
  161:     if ($F[0] eq $username) {($userid,$useroldcryptpwd)=($F[2],$F[1]); @U=@F;}
  162: }
  163: 
  164: # Verify existence of user
  165: if (!defined($userid)) {
  166:     print "Error. User $username does not exist.\n" unless $noprint;
  167:     unlink('/tmp/lock_lcpasswd');
  168:     exit 5;
  169: }
  170: 
  171: # Construct new password entry (random salt)
  172: my $newcryptpwd=crypt($password1,(join '', ('.', '/', 0..9, 'A'..'Z', 'a'..'z')[rand 64, rand 64]));
  173: $U[1]=$newcryptpwd;
  174: my $userline=join(':',@U);
  175: my $rootid=&enable_root_capability;
  176: if ($rootid!=0) {
  177:     print "Error.  Root was not successfully enabled.\n" unless $noprint;
  178:     unlink('/tmp/lock_lcpasswd');
  179:     exit 7;
  180: }
  181: open PASSWORDFILE, '>/etc/passwd' or (print("Error.  Cannot open /etc/passwd.\n") && unlink('/tmp/lock_lcpasswd') && exit(8));
  182: for my $l (@lines) {
  183:     @F=split(/\:/,$l);
  184:     if ($F[0] eq $username) {print PASSWORDFILE "$userline\n";}
  185:     else {print PASSWORDFILE "$l\n";}
  186: }
  187: close PASSWORDFILE;
  188: 
  189: ($>,$<)=(0,0); # fool smbpasswd here to think this is not a setuid environment
  190: unless (-e '/etc/smbpasswd') {
  191:     open (OUT,'>/etc/smbpasswd'); close OUT;
  192: }
  193: my $smbexist=0;
  194: open (IN, '</etc/smbpasswd');
  195: my @lines=<IN>;
  196: close IN;
  197: for my $l (@lines) {
  198:     chop $l;
  199:     my @F=split(/\:/,$l);
  200:     if ($F[0] eq $username) {$smbexist=1;}
  201: }
  202: unless ($smbexist) {
  203:     open(OUT,'>>/etc/smbpasswd');
  204:     print OUT join(':',($safeusername,$userid,'XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX','','/home/'.$safeusername,'/bin/bash')) . "\n";
  205:     close OUT;
  206: }
  207: open(OUT,"|/usr/bin/smbpasswd -s $safeusername>/dev/null");
  208: print OUT $password1; print OUT "\n";
  209: print OUT $password1; print OUT "\n";
  210: close OUT;
  211: $<=$wwwid; # unfool the program
  212: 
  213: # Make final modifications to the user directory.
  214: # Add a public_html file with a stand-in index.html file.
  215: 
  216: system('/bin/chmod','-R','0640',"/home/$safeusername");
  217: system('/bin/chmod','0750',"/home/$safeusername");
  218: mkdir "/home/$safeusername/public_html",0750;
  219: open OUT,">/home/$safeusername/public_html";
  220: print OUT<<END;
  221: <HTML>
  222: <HEAD>
  223: <TITLE>$safeusername</TITLE>
  224: </HEAD>
  225: <BODY>
  226: <H1>$safeusername</H1>
  227: <P>
  228: Learning Online Network
  229: </P>
  230: <P>
  231: This area provides for:
  232: </P>
  233: <UL>
  234: <LI>resource construction
  235: <LI>resource publication
  236: <LI>record-keeping
  237: </UL>
  238: </BODY>
  239: </HTML>
  240: END
  241: close OUT;
  242: 
  243: &disable_root_capability;
  244: unlink('/tmp/lock_lcpasswd');
  245: exit 0;
  246: 
  247: # ----------------------------------------------------------- have setuid script run as root
  248: sub enable_root_capability {
  249:     if ($wwwid==$>) {
  250: 	($<,$>)=($>,$<);
  251: 	($(,$))=($),$();
  252:     }
  253:     else {
  254: 	# root capability is already enabled
  255:     }
  256:     return $>;
  257: }
  258: 
  259: # ----------------------------------------------------------- have setuid script run as www
  260: sub disable_root_capability {
  261:     if ($wwwid==$<) {
  262: 	($<,$>)=($>,$<);
  263: 	($(,$))=($),$();
  264:     }
  265:     else {
  266: 	# root capability is already disabled
  267:     }
  268: }
  269: 
  270: # ----------------------------------- make sure that another lcpasswd process isn't running
  271: sub try_to_lock {
  272:     my ($lockfile)=@_;
  273:     my $currentpid;
  274:     my $lastpid;
  275:     # Do not manipulate lock file as root
  276:     if ($>==0) {
  277: 	return 0;
  278:     }
  279:     # Try to generate lock file.
  280:     # Wait 3 seconds.  If same process id is in
  281:     # lock file, then assume lock file is stale, and
  282:     # go ahead.  If process id's fluctuate, try
  283:     # for a maximum of 10 times.
  284:     for (0..10) {
  285: 	if (-e $lockfile) {
  286: 	    open(LOCK,"<$lockfile");
  287: 	    $currentpid=<LOCK>;
  288: 	    close LOCK;
  289: 	    if ($currentpid==$lastpid) {
  290: 		last;
  291: 	    }
  292: 	    sleep 3;
  293: 	    $lastpid=$currentpid;
  294: 	}
  295: 	else {
  296: 	    last;
  297: 	}
  298: 	if ($_==10) {
  299: 	    return 0;
  300: 	}
  301:     }
  302:     open(LOCK,">$lockfile");
  303:     print LOCK $$;
  304:     close LOCK;
  305:     return 1;
  306: }