1: #!/usr/bin/perl
2:
3: # The Learning Online Network with CAPA
4: #
5: # Copyright Michigan State University Board of Trustees
6: #
7: # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
8: #
9: # LON-CAPA is free software; you can redistribute it and/or modify
10: # it under the terms of the GNU General Public License as published by
11: # the Free Software Foundation; either version 2 of the License, or
12: # (at your option) any later version.
13: #
14: # LON-CAPA is distributed in the hope that it will be useful,
15: # but WITHOUT ANY WARRANTY; without even the implied warranty of
16: # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17: # GNU General Public License for more details.
18: #
19: # You should have received a copy of the GNU General Public License
20: # along with LON-CAPA; if not, write to the Free Software
21: # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
22: #
23: # /home/httpd/html/adm/gpl.txt
24: #
25: # http://www.lon-capa.org/
26: #
27: # lchtmldir - LONC-CAPA setuid script to:
28: # o If necessary, add a public_html directory
29: # to the specified user home directory.
30: # o Set the permissions according to the authentication type.
31: #
32: # Motivations:
33: # Originally, account creation would create a public_html
34: # directory for unix authorized people only. It is possible to have
35: # Kerberos, internal and locally authorized 'users' which may be authors
36: # and hence need a properly owned an protected public_html directory
37: # to serve as their construction space.
38: #
39: # Author:
40: # Ron Fox
41: # NSCL
42: # Michigan State University8
43: # East Lansing, MI 48824-1321
44:
45: # General flow of control:
46: # 1. Validate process state (must be run as www).
47: # 2. Validate parameters: Need two parameters:
48: # o Homedir - Home diretory of user
49: # o Username - Name of the user.
50: # o AuthMode - Authentication mode, can be:
51: # - unix
52: # - internal
53: # - krb4
54: # - localauth
55: # 3. Untaint the usename and home directory
56: #
57: # 4. As root if necessary, create $Homedir/public_html
58: # 5. Set ownership/permissions according to authentication mode (AuthMode)
59: # - unix - ~owner:www/2775
60: # - krb4 - ~owner:www/2775
61: # - internal - www:www/2775
62: # - local - www:www/2775
63: #
64:
65: #
66: # Take a few precautions to be sure that we're not vulnerable to trojan
67: # horses and other fine issues:
68: #
69: use strict;
70: use Fcntl qw(:mode);
71: use DirHandle;
72: use POSIX;
73:
74: $ENV{'PATH'} = '/bin:/usr/bin:/usr/local/sbin:/home/httpd/perl';
75: delete @ENV{qw{IFS CDPATH ENV BASH_ENV}};
76:
77: my $DEBUG = 1; # .nonzero -> Debug printing enabled.
78: my $path_sep = "/"; # Unix like operating systems.
79:
80:
81: # If the UID of the running process is not www exit with error.
82:
83: if ($DEBUG) {
84: print("Checking uid...\n");
85: }
86: my $wwwid = getpwnam('www');
87: &DisableRoot;
88: if($wwwid != $>) {
89: if ($DEBUG) {
90: print("User ID incorrect. This program must be run as user 'www'\n");
91: }
92: exit 1; # Exit with error status.
93: }
94:
95: # There must be three 'command line' parameters. The first
96: # is the home directory of the user.
97: # The second is the name of the user. This is only referenced
98: # in code branches dealing with unix mode authentication.
99: # The last is the authentication mode which must be one of unix, internal
100: # krb4 or localauth.
101: # If there is an error in the argument count or countents, we exit with an
102: # error.
103:
104: if ($DEBUG) {
105: print("Checking parameters: \n");
106: }
107: if(@ARGV != 3) {
108: if($DEBUG) {
109: print("Error: lchtmldir need 3 parameters \n");
110: }
111: exit 2;
112: }
113: my ($dir,$username,$authentication) = @ARGV;
114:
115: if($DEBUG) {
116: print ("Directory = $dir \n");
117: print ("User = $username \n");
118: print ("Authmode = $authentication \n");
119:
120: }
121:
122: if( $authentication ne "unix:" &&
123: $authentication ne "internal:" &&
124: $authentication !~ /^krb(4|5):(.*)/ &&
125: $authentication ne "localauth:") {
126: if($DEBUG) {
127: print("Invalid authentication parameter: ".$authentication."\n");
128: print("Should be one of: unix, internal, krb4, localauth\n");
129: }
130: exit 3;
131: }
132:
133: # Untaint the username.
134:
135: my $match = $username =~ /^(\w+)$/;
136: my $patt = $1;
137:
138: if($DEBUG) {
139: print("Username word match flag = ".$match."\n");
140: print("Match value = ".$patt."\n");
141: }
142:
143: my $safeuser = $patt;
144: if($DEBUG) {
145: print("Save username = $safeuser \n");
146: }
147: if(($username ne $safeuser) or ($safeuser!~/^[A-z]/)) {
148: if($DEBUG) {
149: print("User name $username had illegal characters\n");
150: }
151: exit 4;
152: }
153:
154: #untaint the base directory require that the dir contain only
155: # alphas, / numbers or underscores, and end in /$safeuser
156:
157: $dir =~ /(^([\w\/]+))/;
158:
159: my $dirtry1 = $1;
160:
161: $dir =~ /$\/$safeuser/;
162: my $dirtry2 = $1;
163:
164: if(($dirtry1 ne $dir) or ($dirtry2 ne $dir)) {
165: if ($DEBUG) {
166: print("Directory $dir is not a valid home for $safeuser\n");
167: }
168: exit 5;
169: }
170:
171:
172: # As root, create the directory.
173:
174: my $homedir = $dirtry1;
175: my $fulldir = $homedir."/public_html";
176:
177: if($DEBUG) {
178: print("Full directory path is: $fulldir \n");
179: }
180: if(!( -e $dirtry1)) {
181: if($DEBUG) {
182: print("User's home directory $dirtry1 does not exist\n");
183: }
184: if ($authentication eq "unix:") {
185: exit 6;
186: }
187: }
188: if ($authentication eq "unix:") {
189: # check whether group $safeuser exists.
190: my $usergroups = `id -nG $safeuser`;
191: if (! grep /^$safeuser$/, split(/\s+/,$usergroups)) {
192: if($DEBUG) {
193: print("Group \"$safeuser\" does not exist or $safeuser is not a member of that group.\n");
194: }
195: exit 7;
196: }
197: }
198:
199: &EnableRoot;
200:
201: &System("/bin/mkdir -p $fulldir") unless (-e $fulldir);
202: unless(-e $fulldir."/index.html") {
203: open OUT,">".$fulldir."/index.html";
204: print OUT<<END;
205: <html>
206: <head>
207: <title>$safeuser</title>
208: </head>
209: <body bgcolor="#ccffdd">
210: <h1>$safeuser Construction Space</h1>
211: <h2>
212: The Learning<i>Online</i> Network with Computer-Assisted Personalized Approach
213: </h2>
214: <p>
215: This is your construction space within LON-CAPA, where you would construct resources which are meant to be
216: used across courses and institutions.
217: </p>
218: <p>
219: Material within this area can only be seen and edited by $safeuser and designated co-authors. To make
220: it available to students and other instructors, the material needs to be published.
221: </p>
222: </body>
223: </html>
224: END
225: close OUT;
226: }
227:
228: &System("/bin/chmod 02770 $fulldir");
229: &System("/bin/chmod 0770 $fulldir"."/index.html");
230:
231:
232: # Based on the authentiation mode, set the ownership of the directory.
233:
234: if($authentication eq "unix:") { # Unix mode authentication...
235: print "Unix auth\n";
236: &System("/bin/chown -R $safeuser:$safeuser"." ".$fulldir);
237: &JoinGroup($safeuser);
238: } else {
239: # Internal, Kerberos, and Local authentication are for users
240: # who do not have unix accounts on the system. Therefore we
241: # will give ownership of their public_html directories to www:www
242: # If the user is an internal auth user, the rest of the directory tree
243: # gets owned by root. This chown is needed in case what's really happening
244: # is that a file system user is being demoted to internal user...
245:
246: if($authentication eq "internal:") {
247: # In case the user was a unix/filesystem authenticated user,
248: # we'll take a bit of time here to write a script in the
249: # user's home directory that can reset ownerships and permissions
250: # back the way the used to be.
251:
252: # This can take long enough for lond to time out, so we'll do it
253: # in a separate process that we'll not wait for.
254: #
255: my $fpid = fork;
256: if($fpid) {
257: &DisableRoot;
258: exit 0;
259: } else {
260: print "Forked\n";
261: POSIX::setsid(); # Disassociate from parent.
262: print "Separate session\n";
263: &write_restore_script($homedir);
264: print "Restore script written\n";
265: &System("/bin/chown -R root:root ".$homedir);
266: &System("/bin/chown -R www:www ".$fulldir);
267: print "Exiting\n";
268: exit 0;
269: }
270: } else {
271: &System("/bin/chown -R www:www ".$fulldir);
272: }
273:
274: }
275: &DisableRoot;
276:
277: exit 0;
278:
279: #----------------------------------------------------------------------
280: #
281: # Local utility procedures.
282: # These include:
283: # EnableRoot - Start running as root.
284: # DisableRoot- Stop running as root.
285: # JoinGroup - Join www to the specified group.
286:
287: # Turn on as root:
288:
289: sub EnableRoot {
290: if ($wwwid==$>) {
291: ($<,$>)=($>,$<);
292: ($(,$))=($),$();
293: }
294: else {
295: # root capability is already enabled
296: }
297: if($DEBUG) {
298: print("Enable Root - id = $> $<\n");
299: }
300: return $>;
301: }
302:
303: sub DisableRoot {
304: if ($wwwid==$<) {
305: ($<,$>)=($>,$<);
306: ($(,$))=($),$();
307: }
308: else {
309: # root capability is already disabled
310: }
311: if($DEBUG) {
312: print("Disable root: id = ".$>."\n");
313: }
314: }
315: #
316: # Join the www user to the user's group.
317: # we must be running with euid as root at this time.
318: #
319: sub JoinGroup {
320: my $usergroup = shift;
321:
322: my $groups = `/usr/bin/groups www`;
323: # untaint
324: my ($safegroups)=($groups=~/:\s+([\s\w]+)/);
325: $groups=$safegroups;
326: chomp $groups; $groups=~s/^\S+\s+\:\s+//;
327: my @grouplist=split(/\s+/,$groups);
328: my @ugrouplist=grep {!/www|$usergroup/} @grouplist;
329: my $gl=join(',',(@ugrouplist,$usergroup));
330: if (&System('/usr/sbin/usermod','-G',$gl,'www')) {
331: if($DEBUG) {
332: print "Error. Could not make www a member of the group ".
333: "\"$usergroup\".\n";
334: }
335: exit 6;
336: }
337: if (-e '/var/run/httpd.pid') {
338: open(PID,'/var/run/httpd.pid');
339: my $pid=<PID>;
340: close(PID);
341: my ($safepid) = $pid=~ /(\d+)/;
342: $pid = $safepid;
343: if ($pid) {
344: my $status = system("kill -USR1 $safepid");
345: }
346: }
347: }
348:
349:
350:
351: sub System {
352: my ($command,@args) = @_;
353: if($DEBUG) {
354: print("system: $command with args ".join(' ',@args)."\n");
355: }
356: system($command,@args);
357: }
358:
359:
360:
361:
362:
363: #
364: # This file contains code to recursively process
365: # a Directory. This is a bit more powerful
366: # than File::Find in that we pass the full
367: # stat info to the processing function.
368: # For each file in the specified directory subtree,
369: # The user's Code reference is invoked for all files, regular and otherwise
370: # except:
371: # ., ..
372: #
373: # Parameters:
374: # code_ref - Code reference, invoked for each file in the tree.
375: # as follows: CodeRef(directory, name, statinfo)
376: # directory the path to the directory holding the file.
377: # name the name of the file within Directory.
378: # statinfo a reference to the stat of the file.
379: # start_dir - The starting point of the directory walk.
380: #
381: # NOTE:
382: # Yes, we could have just used File::Find, but since we have to get the
383: # stat anyway, this is actually simpler, as File::Find would have gotten
384: # the stat to figure out the file type and then we would have gotten it
385: # again.
386: #
387:
388: sub process_tree {
389: my ($code_ref, $start_dir) = @_;
390:
391: my $dir = new DirHandle $start_dir;
392: if (!defined($dir)) {
393: print "Failed to open dirhandle: $start_dir\n";
394: }
395:
396: # Now iterate through this level of the tree:
397:
398: while (defined (my $name = $dir->read)) {
399: next if $name =~/^\.\.?$/; # Skip ., .. (see cookbook pg 319)
400:
401: my $full_name = $start_dir.$path_sep.$name; # Full filename path.
402: my @stat_info = lstat($full_name);
403: my $mode = $stat_info[2];
404: my $type = $mode & 0170000; # File type.
405:
406: # Unless the file type is a symlink, call the user code:
407:
408: unless ($type == S_IFLNK) {
409: &$code_ref($start_dir, $name, \@stat_info);
410: }
411:
412: # If the entry is a directory, we need to recurse:
413:
414:
415: if (($type == S_IFDIR) != 0) {
416: &process_tree($code_ref, $full_name);
417: }
418: }
419:
420: }
421: #
422: # Callback from process_tree to write the script lines
423: # requried to restore files to current ownership and permission.
424: # Parameters:
425: # dir - Name of the directory the file lives in.
426: # name - Name of the file itself.
427: # statinfo - Array from lstat called on the file.
428: #
429: #
430: sub write_script {
431: my ($dir, $name, $statinfo) = @_;
432:
433: my $fullname = $dir.$path_sep.$name;
434:
435: # We're going to '' the name, but we need to deal with embedded
436: # ' characters. Using " is much worse as we'd then have to
437: # escape all the shell escapes too. This way all we need
438: # to do is replace ' with '\''
439:
440: $fullname =~ s/\'/\'\\\'\'/g;
441:
442: my $perms = $statinfo->[2] & 0777; # Just permissions.
443: printf CHMODSCRIPT "chmod 0%o '%s'\n", $perms, $fullname;
444: printf CHMODSCRIPT "chown %d:%d '%s'\n", $statinfo->[4], $statinfo->[5],
445: $fullname
446:
447:
448: }
449: #
450: # Write a script in the user's home directory that can restore
451: # the permissions and ownerhips of all the files in the directory
452: # tree to their current ownerships and permissions. This is done
453: # prior to making the user into an internally authenticated user
454: # in case they were previously file system authenticated and
455: # need to go back.
456: # The file we will create will be of the form
457: # restore_n.sh Where n is a number that we will keep
458: # incrementing as needed until there isn't a file by that name.
459: #
460: # Parameters:
461: # dir - Path to the user's home directory.
462: #
463: sub write_restore_script {
464: my ($dir) = @_;
465:
466: # Create a unique file:
467:
468: my $version_number = 0;
469: my $filename = 'restore_'.$version_number.'.sh';
470: my $full_name = $dir.$path_sep.$filename;
471:
472: while(-e $full_name) {
473: $version_number++;
474: $filename = 'restore_'.$version_number.'.sh';
475: $full_name = $dir.$path_sep.$filename;
476: }
477: # $full_name is the full path of a file that does not yet exist
478: # of the form we want:
479:
480: open(CHMODSCRIPT, "> $full_name");
481:
482: &process_tree(\&write_script, $dir);
483:
484: close(CHMODSCRIPT);
485:
486: chmod(0750, $full_name);
487:
488: }
489:
490:
491:
492:
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