1: #!/usr/bin/perl
2:
3: # The Learning Online Network with CAPA
4: #
5: # lcuseradd - LON-CAPA setuid script to coordinate all actions
6: # with adding a user with filesystem privileges (e.g. author)
7: #
8: #
9: # $Id: lcuseradd,v 1.36 2005/04/07 22:27:52 albertel Exp $
10: ###
11:
12: ###############################################################################
13: ## ##
14: ## ORGANIZATION OF THIS PERL SCRIPT ##
15: ## ##
16: ## 1. Description of script ##
17: ## 2. Invoking script (standard input) ##
18: ## 3. Example usage inside another piece of code ##
19: ## 4. Description of functions ##
20: ## 5. Exit codes ##
21: ## 6. Initializations ##
22: ## 7. Make sure this process is running from user=www ##
23: ## 8. Start running script with www permissions ##
24: ## 9. Handle case of another lcpasswd process (locking) ##
25: ## 10. Error-check input, need 3 values (user name, password 1, password 2) ##
26: ## 11. Start running script with root permissions ##
27: ## 12. Add user and make www a member of the user-specific group ##
28: ## 13. Set password ##
29: ## 14. Make final modifications to the user directory ##
30: ## 15. Exit script (unlock) ##
31: ## ##
32: ###############################################################################
33:
34: use strict;
35: use File::Find;
36:
37:
38: # ------------------------------------------------------- Description of script
39: #
40: # This script is a setuid script that should
41: # be run by user 'www'. It creates a /home/USERNAME directory.
42: # It adds a user to the unix system.
43: # Passwords are set with lcpasswd.
44: # www becomes a member of this user group.
45:
46: # -------------- Invoking script (standard input versus command-line arguments)
47: # Otherwise sensitive information will be available to ps-ers for
48: # a small but exploitable time window.
49: #
50: # Standard input (STDIN) usage
51: # First line is USERNAME
52: # Second line is PASSWORD
53: # Third line is PASSWORD
54: # Fouth line is the name of a file to which an error code will be written.
55: # If the fourth line is omitted, no error file will be written.
56: # In either case, the program Exits with the code as its Exit status.
57: # The error file will just be a single line containing an
58: # error code.
59: #
60: #
61: #
62: # Command-line arguments [USERNAME] [PASSWORD] [PASSWORD]
63: # Yes, but be very careful here (don't pass shell commands)
64: # and this is only supported to allow perl-system calls.
65: #
66: # Valid passwords must consist of the
67: # ascii characters within the inclusive
68: # range of 0x20 (32) to 0x7E (126).
69: # These characters are:
70: # SPACE and
71: # !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO
72: # PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
73: #
74: # Valid user names must consist of ascii
75: # characters that are alphabetical characters
76: # (A-Z,a-z), numeric (0-9), or the underscore
77: # mark (_). (Essentially, the perl regex \w).
78: # User names must begin with an alphabetical character
79: # (A-Z,a-z).
80:
81: # ---------------------------------- Example usage inside another piece of code
82: # Usage within code
83: #
84: # $Exitcode=
85: # system("/home/httpd/perl/lcuseradd","NAME","PASSWORD1","PASSWORD2")/256;
86: # print "uh-oh" if $Exitcode;
87:
88: # ---------------------------------------------------- Description of functions
89: # enable_root_capability() : have setuid script run as root
90: # disable_root_capability() : have setuid script run as www
91: # try_to_lock() : make sure that another lcpasswd process isn't running
92:
93: # ------------------------------------------------------------------ Exit codes
94: # These are the Exit codes.
95: # ( (0,"ok"),
96: # (1,"User ID mismatch. This program must be run as user 'www'"),
97: # (2,"Error. This program needs 3 command-line arguments (username, ".
98: # "password 1, password 2)."),
99: # (3,"Error. Three lines should be entered into standard input."),
100: # (4,"Error. Too many other simultaneous password change requests being ".
101: # "made."),
102: # (5,"Error. User $username does not exist."),
103: # (6,"Error. Could not make www a member of the group \"$safeusername\"."),
104: # (7,"Error. Root was not successfully enabled.),
105: # (8,"Error. Cannot set password."),
106: # (9,"Error. The user name specified has invalid characters."),
107: # (10,"Error. A password entry had an invalid character."),
108: # (11,"Error. User already exists.),
109: # (12,"Error. Something went wrong with the addition of user ".
110: # "\"$safeusername\"."),
111: # (13,"Error. Password mismatch."),
112: # (14, "Error filename is invalid")
113:
114: # ------------------------------------------------------------- Initializations
115: # Security
116: $ENV{'PATH'}='/bin/:/usr/bin:/usr/local/sbin:/home/httpd/perl'; # Nullify path
117: # information
118: delete @ENV{qw(IFS CDPATH ENV BASH_ENV)}; # nullify potential taints
119:
120: # Do not print error messages.
121: my $noprint=1;
122:
123: # Error file:
124:
125: my $error_file; # This is either the error file name or undef.
126:
127: print "In lcuseradd\n" unless $noprint;
128:
129: # ----------------------------- Make sure this process is running from user=www
130: my $wwwid=getpwnam('www');
131: &disable_root_capability;
132: if ($wwwid!=$>) {
133: print("User ID mismatch. This program must be run as user 'www'\n")
134: unless $noprint;
135: &Exit(1);
136: }
137:
138: # ----------------------------------- Start running script with www permissions
139: &disable_root_capability;
140:
141: # --------------------------- Handle case of another lcpasswd process (locking)
142: unless (&try_to_lock("/tmp/lock_lcpasswd")) {
143: print "Error. Too many other simultaneous password change requests being ".
144: "made.\n" unless $noprint;
145: &Exit(4);
146: }
147:
148: # ------- Error-check input, need 3 values (user name, password 1, password 2).
149: my @input;
150: if (@ARGV>=3) {
151: @input=@ARGV;
152: } elsif (@ARGV) {
153: print("Error. This program needs at least 3 command-line arguments (username, ".
154: "password 1, password 2 [errorfile]).\n") unless $noprint;
155: unlink('/tmp/lock_lcpasswd');
156: &Exit(2);
157: } else {
158: @input=<>;
159: if (@input < 3) {
160: print("Error. At least three lines should be entered into standard input.\n")
161: unless $noprint;
162: unlink('/tmp/lock_lcpasswd');
163: &Exit(3);
164: }
165: foreach (@input) {chomp;}
166: }
167:
168: my ($username,$password1,$password2, $error_file)=@input;
169: print "Username = ".$username."\n" unless $noprint;
170: $username=~/^(\w+)$/;
171: print "Username after substitution - ".$username unless $noprint;
172: my $safeusername=$1;
173: print "Safe username = $safeusername \n" unless $noprint;
174:
175: if (($username ne $safeusername) or ($safeusername!~/^[A-Za-z]/)) {
176: print "Error. The user name specified $username $safeusername has invalid characters.\n"
177: unless $noprint;
178: unlink('/tmp/lock_lcpasswd');
179: &Exit(9);
180: }
181: my $pbad=0;
182: foreach (split(//,$password1)) {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}}
183: foreach (split(//,$password2)) {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}}
184: if ($pbad) {
185: print "Error. A password entry had an invalid character.\n" unless $noprint;
186: unlink('/tmp/lock_lcpasswd');
187: &Exit(10);
188: }
189:
190: #
191: # Safe the filename. For our case, it must only have alpha, numeric, period
192: # and path sparators..
193: #
194:
195: print "Error file is $error_file \n" unless $noprint;
196:
197: if($error_file) {
198: if($error_file =~ /^([(\w)(\d)\.\/]+)$/) {
199: print "Error file matched pattern $error_file : $1\n" unless $noprint;
200: my $safe_error_file = $1; # Untainted I think.
201: print "Error file after transform $safe_error_file\n"
202: unless $noprint;
203: if($error_file == $safe_error_file) {
204: $error_file = $safe_error_file; # untainted error_file.
205: } else {
206: $error_file ="";
207: print "Invalid error filename\n" unless $noprint;
208: Exit(14);
209: }
210:
211: } else {
212: $error_file="";
213: print "Invalid error filename\n" unless $noprint;
214: Exit(14);
215: }
216: }
217:
218:
219: # -- Only add the user if they are >not< in /etc/passwd.
220: # Used to look for the ability to create a new directory for the
221: # user, however that disallows authentication changes from i
222: # internal->fs.. so just check the passwd file instead.
223: #
224: my $not_found = system("cut -d: -f1 /etc/passwd | grep -q \"^$safeusername\$\" ");
225: if (!$not_found) {
226: print "Error user already exists\n" unless $noprint;
227: unlink('/tmp/lock_lcpasswd');
228: &Exit(11);
229: }
230:
231:
232:
233: # -- Only add user if the two password arguments match.
234:
235: if ($password1 ne $password2) {
236: print "Error. Password mismatch.\n" unless $noprint;
237: unlink('/tmp/lock_lcpasswd');
238: &Exit(13);
239: }
240: print "enabling root\n" unless $noprint;
241: # ---------------------------------- Start running script with root permissions
242: &enable_root_capability;
243:
244: # ------------------- Add user and make www a member of the user-specific group
245: # -- Add user
246:
247: print "adding user: $safeusername \n" unless $noprint;
248: my $status = system('/usr/sbin/useradd','-c','LON-CAPA user',$safeusername);
249: if ($status) {
250: print "Error. Something went wrong with the addition of user ".
251: "\"$safeusername\".\n" unless $noprint;
252: print "Final status of useradd = $status";
253: unlink('/tmp/lock_lcpasswd');
254: &Exit(12);
255: }
256: my ($dmy1, $dmy2, $uid, $gid) = getpwnam($safeusername);
257: my ($group) = getgrgid($gid);
258: if (! $group) {
259: print "Error. The primary group of user \"$safeusername\" could not be".
260: "determined.\n" unless $noprint;
261: system("/usr/sbin/userdel -r $safeusername");
262: unlink('/tmp/lock_lcpasswd');
263: &Exit(12);
264: }
265: if ($group != $safeusername) {
266: $status = system("/usr/sbin/groupadd -g $uid $safeusername");
267: if (! $status) {
268: $status = system("/usr/sbin/usermod -g $uid $safeusername");
269: if ($status) {
270: system("/usr/sbin/groupdel $safeusername");
271: }
272: }
273: if ($status) {
274: print "Error. Something went wrong with the addition of user ".
275: "\"$safeusername\".\n" unless $noprint;
276: system("/usr/sbin/userdel -r $safeusername");
277: unlink('/tmp/lock_lcpasswd');
278: &Exit(12);
279: }
280: }
281:
282: print "Done adding user\n" unless $noprint;
283: # Make www a member of that user group.
284: my $groups=`/usr/bin/groups www` or &Exit(6);
285: # untaint
286: my ($safegroups)=($groups=~/:\s*([\s\w]+)/);
287: $groups=$safegroups;
288: chomp $groups; $groups=~s/^\S+\s+\:\s+//;
289: my @grouplist=split(/\s+/,$groups);
290: my @ugrouplist=grep {!/www|$safeusername/} @grouplist;
291: my $gl=join(',',(@ugrouplist,$safeusername));
292: print "Putting user in its own group\n" unless $noprint;
293: if (system('/usr/sbin/usermod','-G',$gl,'www')) {
294: print "Error. Could not make www a member of the group ".
295: "\"$safeusername\".\n" unless $noprint;
296: unlink('/tmp/lock_lcpasswd');
297: &Exit(6);
298: }
299:
300: # ---------------------------------------------------------------- Set password
301: # Set password with lcpasswd (which creates smbpasswd entry).
302:
303: unlink('/tmp/lock_lcpasswd');
304: &disable_root_capability;
305: ($>,$<)=($wwwid,$wwwid);
306: print "Opening lcpasswd pipeline\n" unless $noprint;
307: open OUT,"|/home/httpd/perl/lcpasswd";
308: print OUT $safeusername;
309: print OUT "\n";
310: print OUT $password1;
311: print OUT "\n";
312: print OUT $password1;
313: print OUT "\n";
314: close OUT;
315: if ($?) {
316: print "abnormal Exit from close lcpasswd\n" unless $noprint;
317: &Exit(8);
318: }
319: ($>,$<)=($wwwid,0);
320: &enable_root_capability;
321:
322: # -- Don't add public_html... that can be added either by the user
323: # or by lchtmldir when the user is granted an authorship role.
324:
325: # ------------------------------ Make final modifications to the user directory
326: # -- Add a public_html file with a stand-in index.html file
327:
328: system('/bin/chmod','-R','0660',"/home/$safeusername");
329: system('/bin/chmod','0710',"/home/$safeusername");
330: mkdir "/home/$safeusername/public_html",0755;
331: open OUT,">/home/$safeusername/public_html/index.html";
332: print OUT<<END;
333: <html>
334: <head>
335: <title>$safeusername</title>
336: </head>
337: <body>
338: <h1>Construction Space</h1>
339: <h3>$safeusername</h3>
340: </body>
341: </html>
342: END
343: close OUT;
344:
345: #
346: # In order to allow the loncapa daemons appropriate access
347: # to public_html, Top level and public_html directories should
348: # be owned by safeusername:safeusername as should the smaple index.html..
349: print "lcuseradd ownership\n" unless $noprint;
350: system('/bin/chown','-R',"$safeusername:$safeusername","/home/$safeusername"); # First set std ownership on everything.
351: &set_public_html_permissions("/home/$safeusername/public_html");
352: # system('/bin/chown',"$safeusername:www","/home/$safeusername"); # Now adust top level...
353: # system('/bin/chown','-R',"$safeusername:www","/home/$safeusername/public_html"); # And web dir.
354: # ---------------------------------------------------- Gracefull Apache Restart
355: if (-e '/var/run/httpd.pid') {
356: print "lcuseradd Apache restart\n" unless $noprint;
357: open(PID,'/var/run/httpd.pid');
358: my $pid=<PID>;
359: close(PID);
360: my $pid=~ /(\D+)/;
361: my $safepid = $1;
362: if ($pid) {
363: system('kill','-USR1',"$safepid");
364: }
365: }
366: # -------------------------------------------------------- Exit script
367: print "lcuseradd Exiting\n" unless $noprint;
368: &disable_root_capability;
369: &Exit(0);
370:
371: # ---------------------------------------------- Have setuid script run as root
372: sub enable_root_capability {
373: if ($wwwid==$>) {
374: ($<,$>)=($>,0);
375: ($(,$))=($),0);
376: } else {
377: # root capability is already enabled
378: }
379: return $>;
380: }
381:
382: # ----------------------------------------------- Have setuid script run as www
383: sub disable_root_capability {
384: if ($wwwid==$<) {
385: ($<,$>)=($>,$<);
386: ($(,$))=($),$();
387: } else {
388: # root capability is already disabled
389: }
390: }
391:
392: # ----------------------- Make sure that another lcpasswd process isn't running
393: sub try_to_lock {
394: my ($lockfile)=@_;
395: my $currentpid;
396: my $lastpid;
397: # Do not manipulate lock file as root
398: if ($>==0) {
399: return 0;
400: }
401: # Try to generate lock file.
402: # Wait 3 seconds. If same process id is in
403: # lock file, then assume lock file is stale, and
404: # go ahead. If process id's fluctuate, try
405: # for a maximum of 10 times.
406: for (0..10) {
407: if (-e $lockfile) {
408: open(LOCK,"<$lockfile");
409: $currentpid=<LOCK>;
410: close LOCK;
411: if ($currentpid==$lastpid) {
412: last;
413: }
414: sleep 3;
415: $lastpid=$currentpid;
416: } else {
417: last;
418: }
419: if ($_==10) {
420: return 0;
421: }
422: }
423: open(LOCK,">$lockfile");
424: print LOCK $$;
425: close LOCK;
426: return 1;
427: }
428: # Called by File::Find::find for each file examined.
429: #
430: # Untaint the file and, if it is a directory,
431: # chmod it to 02770
432: #
433: sub set_permission {
434: $File::Find::name =~ /^(.*)$/;
435: my $safe_name = $1; # Untainted filename...
436:
437: print "$safe_name" unless $noprint;
438: if(-d $safe_name) {
439: print " - directory" unless $noprint;
440: chmod(02770, $safe_name);
441: }
442: print "\n" unless $noprint;
443:
444: }
445: #
446: # Set up the correct permissions for all files in the
447: # user's public htmldir. We just do a chmod -R 0660 ... for
448: # the ordinary files. The we use File::Find
449: # to pop through the directory tree changing directories only
450: # to 02770:
451: #
452: sub set_public_html_permissions {
453: my ($topdir) = @_;
454:
455: # Set the top level dir permissions (I'm not sure if find
456: # will enumerate it specifically), correctly and all
457: # files and dirs to the 'ordinary' file permissions:
458:
459: system("chmod -R 0660 $topdir");
460: chmod(02770, $topdir);
461:
462: # Now use find to locate all directories under $topdir
463: # and set their modes to 02770...
464: #
465: print "Find file\n " unless $noprint;
466: File::Find::find({"untaint" => 1,
467: "untaint_pattern" => qr(/^(.*)$/),
468: "untaint_skip" => 1,
469: "no_chdir" => 1,
470: "wanted" => \&set_permission }, "$topdir");
471:
472:
473: }
474:
475: #-------------------------- Exit...
476: #
477: # Write the file if the error_file is defined. Regardless
478: # Exit with the status code.
479: #
480: sub Exit {
481: my ($code) = @_; # Status code.
482:
483: print "Exiting with status $code error file is $error_file\n" unless $noprint;
484: if($error_file) {
485: open(FH, ">$error_file");
486: print FH "$code\n";
487: close(FH);
488: }
489: exit $code;
490: }
491:
492: =head1 NAME
493:
494: lcuseradd - LON-CAPA setuid script to coordinate all actions
495: with adding a user with filesystem privileges (e.g. author)
496:
497: =head1 DESCRIPTION
498:
499: lcuseradd - LON-CAPA setuid script to coordinate all actions
500: with adding a user with filesystem privileges (e.g. author)
501:
502: =head1 README
503:
504: lcuseradd - LON-CAPA setuid script to coordinate all actions
505: with adding a user with filesystem privileges (e.g. author)
506:
507: =head1 PREREQUISITES
508:
509: =head1 COREQUISITES
510:
511: =pod OSNAMES
512:
513: linux
514:
515: =pod SCRIPT CATEGORIES
516:
517: LONCAPA/Administrative
518:
519: =cut
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