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-za-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: &EnableRoot;
189:
190: &System("/bin/mkdir -p $fulldir") unless (-e $fulldir);
191: unless(-e $fulldir."/index.html") {
192: open OUT,">".$fulldir."/index.html";
193: print OUT<<END;
194: <html>
195: <head>
196: <title>$safeuser</title>
197: </head>
198: <body bgcolor="#ccffdd">
199: <h1>$safeuser Construction Space</h1>
200: <h2>
201: The Learning<i>Online</i> Network with Computer-Assisted Personalized Approach
202: </h2>
203: <p>
204: This is your construction space within LON-CAPA, where you would construct resources which are meant to be
205: used across courses and institutions.
206: </p>
207: <p>
208: Material within this area can only be seen and edited by $safeuser and designated co-authors. To make
209: it available to students and other instructors, the material needs to be published.
210: </p>
211: </body>
212: </html>
213: END
214: close OUT;
215: }
216:
217: &System("/bin/chmod 02775 $fulldir");
218: &System("/bin/chmod 0775 $fulldir"."/index.html");
219:
220:
221: # Based on the authentiation mode, set the ownership of the directory.
222:
223: if($authentication eq "unix:") { # Unix mode authentication...
224: &System("/bin/chown -R $safeuser".":".$safeuser." ".$fulldir);
225: &JoinGroup($safeuser);
226: } else {
227: # Internal, Kerberos, and Local authentication are for users
228: # who do not have unix accounts on the system. Therefore we
229: # will give ownership of their public_html directories to www:www
230: # If the user is an internal auth user, the rest of the directory tree
231: # gets owned by root. This chown is needed in case what's really happening
232: # is that a file system user is being demoted to internal user...
233:
234: if($authentication eq "internal:") {
235: # In case the user was a unix/filesystem authenticated user,
236: # we'll take a bit of time here to write a script in the
237: # user's home directory that can reset ownerships and permissions
238: # back the way the used to be.
239:
240: # This can take long enough for lond to time out, so we'll do it
241: # in a separate process that we'll not wait for.
242: #
243: my $fpid = fork;
244: if($fpid) {
245: &DisableRoot;
246: exit 0;
247: } else {
248: print "Forked\n";
249: POSIX::setsid(); # Disassociate from parent.
250: print "Separate session\n";
251: &write_restore_script($homedir);
252: print "Restore script written\n";
253: &System("/bin/chown -R root:root ".$homedir);
254: &System("/bin/chown -R www:www ".$fulldir);
255: print "Exiting\n";
256: exit 0;
257: }
258: } else {
259: &System("/bin/chown -R www:www ".$fulldir);
260: }
261:
262: }
263: &DisableRoot;
264:
265: exit 0;
266:
267: #----------------------------------------------------------------------
268: #
269: # Local utility procedures.
270: # These include:
271: # EnableRoot - Start running as root.
272: # DisableRoot- Stop running as root.
273: # JoinGroup - Join www to the specified group.
274:
275: # Turn on as root:
276:
277: sub EnableRoot {
278: if ($wwwid==$>) {
279: ($<,$>)=($>,$<);
280: ($(,$))=($),$();
281: }
282: else {
283: # root capability is already enabled
284: }
285: if($DEBUG) {
286: print("Enable Root - id = $> $<\n");
287: }
288: return $>;
289: }
290:
291: sub DisableRoot {
292: if ($wwwid==$<) {
293: ($<,$>)=($>,$<);
294: ($(,$))=($),$();
295: }
296: else {
297: # root capability is already disabled
298: }
299: if($DEBUG) {
300: print("Disable root: id = ".$>."\n");
301: }
302: }
303:
304: sub JoinGroup {
305: my $usergroup = shift;
306:
307: my $groups = `/usr/bin/groups www`;
308: # untaint
309: my ($safegroups)=($groups=~/:\s+([\s\w]+)/);
310: $groups=$safegroups;
311: chomp $groups; $groups=~s/^\S+\s+\:\s+//;
312: my @grouplist=split(/\s+/,$groups);
313: my @ugrouplist=grep {!/www|$usergroup/} @grouplist;
314: my $gl=join(',',(@ugrouplist,$usergroup));
315: if (&System('/usr/sbin/usermod','-G',$gl,'www')) {
316: if($DEBUG) {
317: print "Error. Could not make www a member of the group ".
318: "\"$usergroup\".\n";
319: }
320: exit 6;
321: }
322:
323: }
324:
325:
326:
327: sub System {
328: my ($command,@args) = @_;
329: if($DEBUG) {
330: print("system: $command with args ".join(' ',@args)."\n");
331: }
332: system($command,@args);
333: }
334:
335:
336:
337:
338:
339: #
340: # This file contains code to recursively process
341: # a Directory. This is a bit more powerful
342: # than File::Find in that we pass the full
343: # stat info to the processing function.
344: # For each file in the specified directory subtree,
345: # The user's Code reference is invoked for all files, regular and otherwise
346: # except:
347: # ., ..
348: #
349: # Parameters:
350: # code_ref - Code reference, invoked for each file in the tree.
351: # as follows: CodeRef(directory, name, statinfo)
352: # directory the path to the directory holding the file.
353: # name the name of the file within Directory.
354: # statinfo a reference to the stat of the file.
355: # start_dir - The starting point of the directory walk.
356: #
357: # NOTE:
358: # Yes, we could have just used File::Find, but since we have to get the
359: # stat anyway, this is actually simpler, as File::Find would have gotten
360: # the stat to figure out the file type and then we would have gotten it
361: # again.
362: #
363:
364: sub process_tree {
365: my ($code_ref, $start_dir) = @_;
366:
367: my $dir = new DirHandle $start_dir;
368: if (!defined($dir)) {
369: print "Failed to open dirhandle: $start_dir\n";
370: }
371:
372: # Now iterate through this level of the tree:
373:
374: while (defined (my $name = $dir->read)) {
375: next if $name =~/^\.\.?$/; # Skip ., .. (see cookbook pg 319)
376:
377: my $full_name = $start_dir.$path_sep.$name; # Full filename path.
378: my @stat_info = lstat($full_name);
379: my $mode = $stat_info[2];
380: my $type = $mode & 0170000; # File type.
381:
382: # Unless the file type is a symlink, call the user code:
383:
384: unless ($type == S_IFLNK) {
385: &$code_ref($start_dir, $name, \@stat_info);
386: }
387:
388: # If the entry is a directory, we need to recurse:
389:
390:
391: if (($type == S_IFDIR) != 0) {
392: &process_tree($code_ref, $full_name);
393: }
394: }
395:
396: }
397: #
398: # Callback from process_tree to write the script lines
399: # requried to restore files to current ownership and permission.
400: # Parameters:
401: # dir - Name of the directory the file lives in.
402: # name - Name of the file itself.
403: # statinfo - Array from lstat called on the file.
404: #
405: #
406: sub write_script {
407: my ($dir, $name, $statinfo) = @_;
408:
409: my $fullname = $dir.$path_sep.$name;
410:
411: # We're going to '' the name, but we need to deal with embedded
412: # ' characters. Using " is much worse as we'd then have to
413: # escape all the shell escapes too. This way all we need
414: # to do is replace ' with '\''
415:
416: $fullname =~ s/\'/\'\\\'\'/g;
417:
418: my $perms = $statinfo->[2] & 0777; # Just permissions.
419: printf CHMODSCRIPT "chmod 0%o '%s'\n", $perms, $fullname;
420: printf CHMODSCRIPT "chown %d:%d '%s'\n", $statinfo->[4], $statinfo->[5],
421: $fullname
422:
423:
424: }
425: #
426: # Write a script in the user's home directory that can restore
427: # the permissions and ownerhips of all the files in the directory
428: # tree to their current ownerships and permissions. This is done
429: # prior to making the user into an internally authenticated user
430: # in case they were previously file system authenticated and
431: # need to go back.
432: # The file we will create will be of the form
433: # restore_n.sh Where n is a number that we will keep
434: # incrementing as needed until there isn't a file by that name.
435: #
436: # Parameters:
437: # dir - Path to the user's home directory.
438: #
439: sub write_restore_script {
440: my ($dir) = @_;
441:
442: # Create a unique file:
443:
444: my $version_number = 0;
445: my $filename = 'restore_'.$version_number.'.sh';
446: my $full_name = $dir.$path_sep.$filename;
447:
448: while(-e $full_name) {
449: $version_number++;
450: $filename = 'restore_'.$version_number.'.sh';
451: $full_name = $dir.$path_sep.$filename;
452: }
453: # $full_name is the full path of a file that does not yet exist
454: # of the form we want:
455:
456: open(CHMODSCRIPT, "> $full_name");
457:
458: &process_tree(\&write_script, $dir);
459:
460: close(CHMODSCRIPT);
461:
462: chmod(0750, $full_name);
463:
464: }
465:
466:
467:
468:
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