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 1.42 2011/10/24 21:30:09 www 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 DOMAIN
53: # Third line is PASSWORD
54: # Fourth line is PASSWORD
55: # Fifth line is the name of a file to which an error code will be written.
56: # If the fourth line is omitted, no error file will be written.
57: # In either case, the program Exits with the code as its Exit status.
58: # The error file will just be a single line containing an
59: # error code.
60: #
61: #
62: #
63: # Command-line arguments [USERNAME] [DOMAIN] [PASSWORD] [PASSWORD]
64: # Yes, but be very careful here (don't pass shell commands)
65: # and this is only supported to allow perl-system calls.
66: #
67: # Valid passwords must consist of the
68: # ascii characters within the inclusive
69: # range of 0x20 (32) to 0x7E (126).
70: # These characters are:
71: # SPACE and
72: # !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNO
73: # PQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~
74: #
75: # Valid user names must consist of ascii
76: # characters that are alphabetical characters
77: # (A-Z,a-z), numeric (0-9), or the underscore
78: # mark (_). (Essentially, the perl regex \w).
79: # User names must begin with an alphabetical character
80: # (A-Z,a-z).
81:
82: # ---------------------------------- Example usage inside another piece of code
83: # Usage within code
84: #
85: # $Exitcode=
86: # system("/home/httpd/perl/lcuseradd","NAME","DOMAIN","PASSWORD1","PASSWORD2")/256;
87: # print "uh-oh" if $Exitcode;
88:
89: # ---------------------------------------------------- Description of functions
90: # enable_root_capability() : have setuid script run as root
91: # disable_root_capability() : have setuid script run as www
92: # try_to_lock() : make sure that another lcpasswd process isn't running
93:
94: # ------------------------------------------------------------------ Exit codes
95: # These are the Exit codes.
96: # ( (0,"ok"),
97: # (1,"User ID mismatch. This program must be run as user 'www'"),
98: # (2,"Error. This program needs 3 command-line arguments (username, ".
99: # "password 1, password 2)."),
100: # (3,"Error. Three lines should be entered into standard input."),
101: # (4,"Error. Too many other simultaneous password change requests being ".
102: # "made."),
103: # (5,"Error. User $username does not exist."),
104: # (6,"Error. Could not make www a member of the group \"$safeusername\"."),
105: # (7,"Error. Root was not successfully enabled.),
106: # (8,"Error. Cannot set password."),
107: # (9,"Error. The user name specified has invalid characters."),
108: # (10,"Error. A password entry had an invalid character."),
109: # (11,"Error. User already exists.),
110: # (12,"Error. Something went wrong with the addition of user ".
111: # "\"$safeusername\"."),
112: # (13,"Error. Password mismatch."),
113: # (14, "Error filename is invalid"),
114: # (15, "Error. Could not add home directory.")
115:
116: # ------------------------------------------------------------- Initializations
117: # Security
118: $ENV{'PATH'}='/bin/:/usr/bin:/usr/local/sbin:/home/httpd/perl'; # Nullify path
119: # information
120: delete @ENV{qw(IFS CDPATH ENV BASH_ENV)}; # nullify potential taints
121:
122: # Do not print error messages.
123: my $noprint=1;
124:
125: print "In lcuseradd\n" unless $noprint;
126:
127: # ----------------------------- Make sure this process is running from user=www
128: my $wwwid=getpwnam('www');
129: &disable_root_capability;
130: if ($wwwid!=$>) {
131: print("User ID mismatch. This program must be run as user 'www'\n")
132: unless $noprint;
133: &Exit(1);
134: }
135:
136: # ----------------------------------- Start running script with www permissions
137: &disable_root_capability;
138:
139: # --------------------------- Handle case of another lcpasswd process (locking)
140: unless (&try_to_lock("/tmp/lock_lcpasswd")) {
141: print "Error. Too many other simultaneous password change requests being ".
142: "made.\n" unless $noprint;
143: &Exit(4);
144: }
145:
146: # ------- Error-check input, need 3 values (user name, password 1, password 2).
147: my @input;
148: if (@ARGV>=3) {
149: @input=@ARGV;
150: } elsif (@ARGV) {
151: print("Error. This program needs at least 3 command-line arguments (username, ".
152: "password 1, password 2 [errorfile]).\n") unless $noprint;
153: unlink('/tmp/lock_lcpasswd');
154: &Exit(2);
155: } else {
156: @input=<>;
157: if (@input < 3) {
158: print("Error. At least three lines should be entered into standard input.\n")
159: unless $noprint;
160: unlink('/tmp/lock_lcpasswd');
161: &Exit(3);
162: }
163: foreach (@input) {chomp;}
164: }
165:
166: my ($username,$domain,$password1,$password2, $error_file)=@input;
167: print "Username = ".$username."\n" unless $noprint;
168: $username=~/^(\w+)$/;
169: print "Username after substitution - ".$username unless $noprint;
170: my $safeusername=$1;
171: print "Safe username = $safeusername \n" unless $noprint;
172:
173: print "Domain = ".$domain."\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 group and user, and make www a member of the group
245: # -- Add group
246:
247: print "adding group: $safeusername \n" unless $noprint;
248: my $status = system('/usr/sbin/groupadd', $safeusername);
249: if ($status) {
250: print "Error. Something went wrong with the addition of group ".
251: "\"$safeusername\".\n" unless $noprint;
252: print "Final status of groupadd = $status\n";
253: unlink('/tmp/lock_lcpasswd');
254: &Exit(12);
255: }
256: my $gid = getgrnam($safeusername);
257:
258: # -- Add user
259:
260: print "adding user: $safeusername \n" unless $noprint;
261: my $status = system('/usr/sbin/useradd','-c','LON-CAPA user','-g',$gid,$safeusername);
262: if ($status) {
263: print "Error. Something went wrong with the addition of user ".
264: "\"$safeusername\".\n" unless $noprint;
265: system("/usr/sbin/groupdel $safeusername");
266: print "Final status of useradd = $status\n";
267: unlink('/tmp/lock_lcpasswd');
268: &Exit(12);
269: }
270:
271: print "Done adding user\n" unless $noprint;
272: # Make www a member of that user group.
273: my $groups=`/usr/bin/groups www` or &Exit(6);
274: # untaint
275: my ($safegroups)=($groups=~/:\s*([\s\w]+)/);
276: $groups=$safegroups;
277: chomp $groups; $groups=~s/^\S+\s+\:\s+//;
278: my @grouplist=split(/\s+/,$groups);
279: my @ugrouplist=grep {!/www|$safeusername/} @grouplist;
280: my $gl=join(',',(@ugrouplist,$safeusername));
281: print "Putting www in user's group\n" unless $noprint;
282: if (system('/usr/sbin/usermod','-G',$gl,'www')) {
283: print "Error. Could not make www a member of the group ".
284: "\"$safeusername\".\n" unless $noprint;
285: unlink('/tmp/lock_lcpasswd');
286: &Exit(6);
287: }
288:
289: # ---------------------------------------------------------------- Set password
290: # Set password with lcpasswd (which creates smbpasswd entry).
291:
292: unlink('/tmp/lock_lcpasswd');
293: &disable_root_capability;
294: ($>,$<)=($wwwid,$wwwid);
295: print "Opening lcpasswd pipeline\n" unless $noprint;
296: open OUT,"|/home/httpd/perl/lcpasswd";
297: print OUT $safeusername;
298: print OUT "\n";
299: print OUT $password1;
300: print OUT "\n";
301: print OUT $password1;
302: print OUT "\n";
303: close OUT;
304: if ($?) {
305: print "abnormal Exit from close lcpasswd\n" unless $noprint;
306: &Exit(8);
307: }
308: ($>,$<)=($wwwid,0);
309: &enable_root_capability;
310:
311: # Check if home directory exists for user
312: # If not, create one.
313: if (!-e "/home/$safeusername") {
314: if (!mkdir("/home/$safeusername",0710)) {
315: print "Error. Could not add home directory for ".
316: "\"$safeusername\".\n" unless $noprint;
317: unlink('/tmp/lock_lcpasswd');
318: &Exit(15);
319: }
320: }
321:
322: # ------------------------------ Make final modifications to the user directory
323: # -- Add a construction space
324:
325: my $path="/home/httpd/html/priv/".$domain;
326: unless (-e $path) {
327: mkdir($path);
328: }
329: unless (-e $path.'/'.$safeusername) {
330: mkdir($path.'/'.$safeusername);
331: }
332:
333:
334: # ---------------------------------------------------- Gracefull Apache Restart
335: my $pidfile;
336: if (-e '/var/run/httpd.pid') {
337: $pidfile = '/var/run/httpd.pid';
338: } elsif (-e '/var/run/httpd2.pid') { #Apache 2 on SuSE 10.1 and SLES10
339: $pidfile = '/var/run/httpd2.pid';
340: }
341:
342: if ($pidfile) {
343: print "lcuseradd Apache restart\n" unless $noprint;
344: open(PID,"<$pidfile");
345: my $pid=<PID>;
346: close(PID);
347: $pid=~ /(\D+)/;
348: my $safepid = $1;
349: if ($pid) {
350: system('kill','-USR1',"$safepid");
351: }
352: }
353: # -------------------------------------------------------- Exit script
354: print "lcuseradd Exiting\n" unless $noprint;
355: &disable_root_capability;
356: &Exit(0);
357:
358: # ---------------------------------------------- Have setuid script run as root
359: sub enable_root_capability {
360: if ($wwwid==$>) {
361: ($<,$>)=($>,0);
362: ($(,$))=($),0);
363: } else {
364: # root capability is already enabled
365: }
366: if ($wwwid == $>) {
367: print("Failed to become root\n") unless $noprint;
368: } else {
369: print("Became root\n") unless $noprint;
370: }
371: return $>;
372: }
373:
374: # ----------------------------------------------- Have setuid script run as www
375: sub disable_root_capability {
376: if ($wwwid==$<) {
377: ($<,$>)=($>,$<);
378: ($(,$))=($),$();
379: } else {
380: # root capability is already disabled
381: }
382: }
383:
384: # ----------------------- Make sure that another lcpasswd process isn't running
385: sub try_to_lock {
386: my ($lockfile)=@_;
387: my $currentpid;
388: my $lastpid;
389: # Do not manipulate lock file as root
390: if ($>==0) {
391: return 0;
392: }
393: # Try to generate lock file.
394: # Wait 3 seconds. If same process id is in
395: # lock file, then assume lock file is stale, and
396: # go ahead. If process id's fluctuate, try
397: # for a maximum of 10 times.
398: for (0..10) {
399: if (-e $lockfile) {
400: open(LOCK,"<$lockfile");
401: $currentpid=<LOCK>;
402: close LOCK;
403: if ($currentpid==$lastpid) {
404: last;
405: }
406: sleep 3;
407: $lastpid=$currentpid;
408: } else {
409: last;
410: }
411: if ($_==10) {
412: return 0;
413: }
414: }
415: open(LOCK,">$lockfile");
416: print LOCK $$;
417: close LOCK;
418: return 1;
419: }
420: # Called by File::Find::find for each file examined.
421: #
422: # Untaint the file and, if it is a directory,
423: # chmod it to 02770
424: #
425: sub set_permission {
426: $File::Find::name =~ /^(.*)$/;
427: my $safe_name = $1; # Untainted filename...
428:
429: print "$safe_name" unless $noprint;
430: if(-d $safe_name) {
431: print " - directory" unless $noprint;
432: chmod(02770, $safe_name);
433: }
434: print "\n" unless $noprint;
435:
436: }
437:
438: #-------------------------- Exit...
439: #
440: # Write the file if the error_file is defined. Regardless
441: # Exit with the status code.
442: #
443: sub Exit {
444: my ($code) = @_; # Status code.
445:
446: # TODO: Ensure the error file is owned/deletable by www:www:
447:
448: &disable_root_capability(); # We run unprivileged to write the error file.
449:
450: print "Exiting with status $code error file is $error_file\n" unless $noprint;
451: if($error_file) {
452: open(FH, ">$error_file");
453: print FH "$code\n";
454: close(FH);
455: }
456: exit $code;
457: }
458:
459: =head1 NAME
460:
461: lcuseradd - LON-CAPA setuid script to coordinate all actions
462: with adding a user with filesystem privileges (e.g. author)
463:
464: =head1 DESCRIPTION
465:
466: lcuseradd - LON-CAPA setuid script to coordinate all actions
467: with adding a user with filesystem privileges (e.g. author)
468:
469: =head1 README
470:
471: lcuseradd - LON-CAPA setuid script to coordinate all actions
472: with adding a user with filesystem privileges (e.g. author)
473:
474: =head1 PREREQUISITES
475:
476: =head1 COREQUISITES
477:
478: =pod OSNAMES
479:
480: linux
481:
482: =pod SCRIPT CATEGORIES
483:
484: LONCAPA/Administrative
485:
486: =cut
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