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 1.39 2006/08/25 21:25:22 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: # (15, "Error. Could not add home directory.")
114:
115: # ------------------------------------------------------------- Initializations
116: # Security
117: $ENV{'PATH'}='/bin/:/usr/bin:/usr/local/sbin:/home/httpd/perl'; # Nullify path
118: # information
119: delete @ENV{qw(IFS CDPATH ENV BASH_ENV)}; # nullify potential taints
120:
121: # Do not print error messages.
122: my $noprint=1;
123:
124: print "In lcuseradd\n" unless $noprint;
125:
126: # ----------------------------- Make sure this process is running from user=www
127: my $wwwid=getpwnam('www');
128: &disable_root_capability;
129: if ($wwwid!=$>) {
130: print("User ID mismatch. This program must be run as user 'www'\n")
131: unless $noprint;
132: &Exit(1);
133: }
134:
135: # ----------------------------------- Start running script with www permissions
136: &disable_root_capability;
137:
138: # --------------------------- Handle case of another lcpasswd process (locking)
139: unless (&try_to_lock("/tmp/lock_lcpasswd")) {
140: print "Error. Too many other simultaneous password change requests being ".
141: "made.\n" unless $noprint;
142: &Exit(4);
143: }
144:
145: # ------- Error-check input, need 3 values (user name, password 1, password 2).
146: my @input;
147: if (@ARGV>=3) {
148: @input=@ARGV;
149: } elsif (@ARGV) {
150: print("Error. This program needs at least 3 command-line arguments (username, ".
151: "password 1, password 2 [errorfile]).\n") unless $noprint;
152: unlink('/tmp/lock_lcpasswd');
153: &Exit(2);
154: } else {
155: @input=<>;
156: if (@input < 3) {
157: print("Error. At least three lines should be entered into standard input.\n")
158: unless $noprint;
159: unlink('/tmp/lock_lcpasswd');
160: &Exit(3);
161: }
162: foreach (@input) {chomp;}
163: }
164:
165: my ($username,$password1,$password2, $error_file)=@input;
166: print "Username = ".$username."\n" unless $noprint;
167: $username=~/^(\w+)$/;
168: print "Username after substitution - ".$username unless $noprint;
169: my $safeusername=$1;
170: print "Safe username = $safeusername \n" unless $noprint;
171:
172: if (($username ne $safeusername) or ($safeusername!~/^[A-Za-z]/)) {
173: print "Error. The user name specified $username $safeusername has invalid characters.\n"
174: unless $noprint;
175: unlink('/tmp/lock_lcpasswd');
176: &Exit(9);
177: }
178: my $pbad=0;
179: foreach (split(//,$password1)) {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}}
180: foreach (split(//,$password2)) {if ((ord($_)<32)||(ord($_)>126)){$pbad=1;}}
181: if ($pbad) {
182: print "Error. A password entry had an invalid character.\n" unless $noprint;
183: unlink('/tmp/lock_lcpasswd');
184: &Exit(10);
185: }
186:
187: #
188: # Safe the filename. For our case, it must only have alpha, numeric, period
189: # and path sparators..
190: #
191:
192: print "Error file is $error_file \n" unless $noprint;
193:
194: if($error_file) {
195: if($error_file =~ /^([(\w)(\d)\.\/]+)$/) {
196: print "Error file matched pattern $error_file : $1\n" unless $noprint;
197: my $safe_error_file = $1; # Untainted I think.
198: print "Error file after transform $safe_error_file\n"
199: unless $noprint;
200: if($error_file == $safe_error_file) {
201: $error_file = $safe_error_file; # untainted error_file.
202: } else {
203: $error_file ="";
204: print "Invalid error filename\n" unless $noprint;
205: Exit(14);
206: }
207:
208: } else {
209: $error_file="";
210: print "Invalid error filename\n" unless $noprint;
211: Exit(14);
212: }
213: }
214:
215:
216: # -- Only add the user if they are >not< in /etc/passwd.
217: # Used to look for the ability to create a new directory for the
218: # user, however that disallows authentication changes from i
219: # internal->fs.. so just check the passwd file instead.
220: #
221: my $not_found = system("cut -d: -f1 /etc/passwd | grep -q \"^$safeusername\$\" ");
222: if (!$not_found) {
223: print "Error user already exists\n" unless $noprint;
224: unlink('/tmp/lock_lcpasswd');
225: &Exit(11);
226: }
227:
228:
229:
230: # -- Only add user if the two password arguments match.
231:
232: if ($password1 ne $password2) {
233: print "Error. Password mismatch.\n" unless $noprint;
234: unlink('/tmp/lock_lcpasswd');
235: &Exit(13);
236: }
237: print "enabling root\n" unless $noprint;
238: # ---------------------------------- Start running script with root permissions
239: &enable_root_capability;
240:
241: # ------------------- Add group and user, and make www a member of the group
242: # -- Add group
243:
244: print "adding group: $safeusername \n" unless $noprint;
245: my $status = system('/usr/sbin/groupadd', $safeusername);
246: if ($status) {
247: print "Error. Something went wrong with the addition of group ".
248: "\"$safeusername\".\n" unless $noprint;
249: print "Final status of groupadd = $status\n";
250: unlink('/tmp/lock_lcpasswd');
251: &Exit(12);
252: }
253: my $gid = getgrnam($safeusername);
254:
255: # -- Add user
256:
257: print "adding user: $safeusername \n" unless $noprint;
258: my $status = system('/usr/sbin/useradd','-c','LON-CAPA user','-g',$gid,$safeusername);
259: if ($status) {
260: print "Error. Something went wrong with the addition of user ".
261: "\"$safeusername\".\n" unless $noprint;
262: system("/usr/sbin/groupdel $safeusername");
263: print "Final status of useradd = $status\n";
264: unlink('/tmp/lock_lcpasswd');
265: &Exit(12);
266: }
267:
268: print "Done adding user\n" unless $noprint;
269: # Make www a member of that user group.
270: my $groups=`/usr/bin/groups www` or &Exit(6);
271: # untaint
272: my ($safegroups)=($groups=~/:\s*([\s\w]+)/);
273: $groups=$safegroups;
274: chomp $groups; $groups=~s/^\S+\s+\:\s+//;
275: my @grouplist=split(/\s+/,$groups);
276: my @ugrouplist=grep {!/www|$safeusername/} @grouplist;
277: my $gl=join(',',(@ugrouplist,$safeusername));
278: print "Putting www in user's group\n" unless $noprint;
279: if (system('/usr/sbin/usermod','-G',$gl,'www')) {
280: print "Error. Could not make www a member of the group ".
281: "\"$safeusername\".\n" unless $noprint;
282: unlink('/tmp/lock_lcpasswd');
283: &Exit(6);
284: }
285:
286: # ---------------------------------------------------------------- Set password
287: # Set password with lcpasswd (which creates smbpasswd entry).
288:
289: unlink('/tmp/lock_lcpasswd');
290: &disable_root_capability;
291: ($>,$<)=($wwwid,$wwwid);
292: print "Opening lcpasswd pipeline\n" unless $noprint;
293: open OUT,"|/home/httpd/perl/lcpasswd";
294: print OUT $safeusername;
295: print OUT "\n";
296: print OUT $password1;
297: print OUT "\n";
298: print OUT $password1;
299: print OUT "\n";
300: close OUT;
301: if ($?) {
302: print "abnormal Exit from close lcpasswd\n" unless $noprint;
303: &Exit(8);
304: }
305: ($>,$<)=($wwwid,0);
306: &enable_root_capability;
307:
308: # Check if home directory exists for user
309: # If not, create one.
310: if (!-e "/home/$safeusername") {
311: if (!mkdir("/home/$safeusername",0710)) {
312: print "Error. Could not add home directory for ".
313: "\"$safeusername\".\n" unless $noprint;
314: unlink('/tmp/lock_lcpasswd');
315: &Exit(15);
316: }
317: }
318:
319: # ------------------------------ Make final modifications to the user directory
320: # -- Add a public_html file with a stand-in index.html file
321:
322: if (-d "/home/$safeusername") {
323: system('/bin/chmod','-R','0660',"/home/$safeusername");
324: system('/bin/chmod','0710',"/home/$safeusername");
325: mkdir "/home/$safeusername/public_html",0755;
326: open OUT,">/home/$safeusername/public_html/index.html";
327: print OUT<<END;
328: <html>
329: <head>
330: <title>$safeusername</title>
331: </head>
332: <body>
333: <h1>Construction Space</h1>
334: <h3>$safeusername</h3>
335: </body>
336: </html>
337: END
338: close OUT;
339: }
340:
341: #
342: # In order to allow the loncapa daemons appropriate access
343: # to public_html, Top level and public_html directories should
344: # be owned by safeusername:safeusername as should the smaple index.html..
345: print "lcuseradd ownership\n" unless $noprint;
346: system('/bin/chown','-R',"$safeusername:$safeusername","/home/$safeusername"); # First set std ownership on everything.
347: &set_public_html_permissions("/home/$safeusername/public_html");
348: # system('/bin/chown',"$safeusername:www","/home/$safeusername"); # Now adust top level...
349: # system('/bin/chown','-R',"$safeusername:www","/home/$safeusername/public_html"); # And web dir.
350: # ---------------------------------------------------- Gracefull Apache Restart
351: if (-e '/var/run/httpd.pid') {
352: print "lcuseradd Apache restart\n" unless $noprint;
353: open(PID,'/var/run/httpd.pid');
354: my $pid=<PID>;
355: close(PID);
356: $pid=~ /(\D+)/;
357: my $safepid = $1;
358: if ($pid) {
359: system('kill','-USR1',"$safepid");
360: }
361: }
362: # -------------------------------------------------------- Exit script
363: print "lcuseradd Exiting\n" unless $noprint;
364: &disable_root_capability;
365: &Exit(0);
366:
367: # ---------------------------------------------- Have setuid script run as root
368: sub enable_root_capability {
369: if ($wwwid==$>) {
370: ($<,$>)=($>,0);
371: ($(,$))=($),0);
372: } else {
373: # root capability is already enabled
374: }
375: return $>;
376: }
377:
378: # ----------------------------------------------- Have setuid script run as www
379: sub disable_root_capability {
380: if ($wwwid==$<) {
381: ($<,$>)=($>,$<);
382: ($(,$))=($),$();
383: } else {
384: # root capability is already disabled
385: }
386: }
387:
388: # ----------------------- Make sure that another lcpasswd process isn't running
389: sub try_to_lock {
390: my ($lockfile)=@_;
391: my $currentpid;
392: my $lastpid;
393: # Do not manipulate lock file as root
394: if ($>==0) {
395: return 0;
396: }
397: # Try to generate lock file.
398: # Wait 3 seconds. If same process id is in
399: # lock file, then assume lock file is stale, and
400: # go ahead. If process id's fluctuate, try
401: # for a maximum of 10 times.
402: for (0..10) {
403: if (-e $lockfile) {
404: open(LOCK,"<$lockfile");
405: $currentpid=<LOCK>;
406: close LOCK;
407: if ($currentpid==$lastpid) {
408: last;
409: }
410: sleep 3;
411: $lastpid=$currentpid;
412: } else {
413: last;
414: }
415: if ($_==10) {
416: return 0;
417: }
418: }
419: open(LOCK,">$lockfile");
420: print LOCK $$;
421: close LOCK;
422: return 1;
423: }
424: # Called by File::Find::find for each file examined.
425: #
426: # Untaint the file and, if it is a directory,
427: # chmod it to 02770
428: #
429: sub set_permission {
430: $File::Find::name =~ /^(.*)$/;
431: my $safe_name = $1; # Untainted filename...
432:
433: print "$safe_name" unless $noprint;
434: if(-d $safe_name) {
435: print " - directory" unless $noprint;
436: chmod(02770, $safe_name);
437: }
438: print "\n" unless $noprint;
439:
440: }
441: #
442: # Set up the correct permissions for all files in the
443: # user's public htmldir. We just do a chmod -R 0660 ... for
444: # the ordinary files. The we use File::Find
445: # to pop through the directory tree changing directories only
446: # to 02770:
447: #
448: sub set_public_html_permissions {
449: my ($topdir) = @_;
450:
451: # Set the top level dir permissions (I'm not sure if find
452: # will enumerate it specifically), correctly and all
453: # files and dirs to the 'ordinary' file permissions:
454:
455: system("chmod -R 0660 $topdir");
456: chmod(02770, $topdir);
457:
458: # Now use find to locate all directories under $topdir
459: # and set their modes to 02770...
460: #
461: print "Find file\n " unless $noprint;
462: File::Find::find({"untaint" => 1,
463: "untaint_pattern" => qr(/^(.*)$/),
464: "untaint_skip" => 1,
465: "no_chdir" => 1,
466: "wanted" => \&set_permission }, "$topdir");
467:
468:
469: }
470:
471: #-------------------------- Exit...
472: #
473: # Write the file if the error_file is defined. Regardless
474: # Exit with the status code.
475: #
476: sub Exit {
477: my ($code) = @_; # Status code.
478:
479: # TODO: Ensure the error file is owned/deletable by www:www:
480:
481: &disable_root_capability(); # We run unprivileged to write the error file.
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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