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Re: [K12OSN] Dropbox directory permissions



OK. A quick test was done.

Make the directory group writeable and set the file mask for that
directory to make all files -w- for the group. The teacher can still
read and move the files but students can only drop them. They can't copy
them or list them.

Anything a bunch of kids can dream up, a dedicated bunch of old farts
can squash.

:)

On Sun, 2007-03-04 at 20:59 -0600, Petre Scheie wrote:
> It's not as convenient, but perhaps you could give each student her/his 
> own directory within /home/inbox, with permissions set to 770, and put 
> the teacher into each student's primary group so the teacher can get to 
> the files.  Give each student's directory the same name as the student's 
> ID, e.g., bob's directory would be /home/inbox/bob.  Modify your script 
> so that is automatically uses the caller's ID to specify the path to the 
> directory.  This way, only the student and the teacher have access to 
> that student's work.  It would be harder to hunt through all the 
> directories for the students' work, but you could write a script that 
> parses through all those directories and moves any files found to one 
> folder in the teacher's $HOME.  Give the teacher an icon to call it with 
> sudo, call it something like "Gather up handed in assignments".
> 
> HTH
> 
> Petre
> 
> Robert Arkiletian wrote:
> > mkdir /home/inbox
> > chmod 1773 /home/inbox  (Not readable by others and sticky bit
> > prevents overwriting)
> > 
> > But if a clever kid happens to know the filename of another kid
> > 
> > cp /home/inbox/filename ~
> > 
> > unfortunately works. Not good.
> > ==============================
> > My solution:
> > Write a 1 line bashscript /usr/bin/handin
> > 
> > cp -p $1 /home/inbox/
> > 
> > chgrp teacher /usr/bin/handin
> > chmod 2755 /usr/bin/handin   (setgid escalate priviliges to teacher group)
> > 
> > now
> > 
> > chgrp teacher /home/inbox
> > chmod 1770 /home/inbox
> > 
> > To hand-in a test students go
> > handin filename
> > 
> > But it does not work. I get
> > 
> > cp: cannot stat `/home/inbox/filename': Permission denied
> > 
> > Why? Apparently, setgid cannot change the group of the process to one
> > which you don't already belong to. So I have to add the teacher group
> > to all students, which defeats the purpose. So much for privilege
> > escalation of setgid. I even tried using setuid.
> > 
> > [root server ~]# ls -ld /home/inbox/
> > drwxrwx--T  2 root root 4096 Mar  4 16:02 /home/inbox/
> > [root server ~]# ls -l /usr/bin/handin
> > -rwsr-xr-x  1 root root 79 Mar  3 14:40 /usr/bin/handin
> > 
> > I get the same stat Permission denied error. Any suggestions?
> > 
> > 
> 
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-- 
James P. Kinney III          
CEO & Director of Engineering 
Local Net Solutions,LLC        
770-493-8244                    
http://www.localnetsolutions.com

GPG ID: 829C6CA7 James P. Kinney III (M.S. Physics)
<jkinney localnetsolutions com>
Fingerprint = 3C9E 6366 54FC A3FE BA4D 0659 6190 ADC3 829C 6CA7

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