MMDF II .forward permissions

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2 total messages Started by Gunther Anderson Tue, 21 Jun 1994 16:32

#5692

Author: Gunther Anderson
Date: Tue, 21 Jun 1994 16:32

34 lines
2524 bytes

Recently, my users have gotten more technically savvy, and have learned
how to change permissions on their home directories.  MMDF requires that
the file .forward be owned by the user, and readable by the user 'mmdf'. 
I'm having trouble making that work.  If users have directory permissions
set to at least 751 (rwxr-x--x), then users' .forwards get read.  However,
750 doesn't cut it.  (Note that all the .forwards are set to 644).  The
users all have the same group id, 'group'.  Normally, 'mmdf' has the group
id 'mmdf' in /etc/passwd, and is listed as part of 'group' in /etc/group. 
When logged in as 'mmdf' I can read everyone's .forward properly.  But
msg.log from MMDF has lines like: 

[SYSERR(13)Permission denied]  lc_forward: stat(/u/gunther/.forward)

whenever a message goes to an account with a .forward.  I have tried 
setting the /etc/passwd group designation of 'mmdf' to 'group' and that 
hasn't helped either.  It's like the system is ignoring group permissions 
on the directories, so that only world file-searching (--x) permission 
allows MMDF to get to the .forward, which it can then read because of 
world-readability on the file.

This is no good for me, since I would like MMDF to be able to read
.forwards no matter what the directory permission.  I want users to be
able to be as paranoid as they want, and still have message forwarding
work.  I have tried chown'ing /usr/mmdf/bin/submit to root (it's setuid), 
but then the system stops working altogether, apparently knowing full 
well that that's an awful security hole.

What can I do?  How do others have MMDF configured to handle user-level 
.forwards?  Is there an MMDF-specific mailing list I can glom onto?

My system is SCO Unix SYSV 3.2.4.2 with the stock MMDF II.

Thanks for any help,
Gunther Anderson

Re: MMDF II .forward permissions

#5691

Author: Jim Sullivan
Date: Wed, 22 Jun 1994 17:22

41 lines
3068 bytes

In <Crr9xE.5LB@ssi.edc.org> gunther@ssi.edc.org (Gunther Anderson) writes:
>Recently, my users have gotten more technically savvy, and have learned
>how to change permissions on their home directories.  MMDF requires that
>the file .forward be owned by the user, and readable by the user 'mmdf'. 
>I'm having trouble making that work.  If users have directory permissions
>set to at least 751 (rwxr-x--x), then users' .forwards get read.  However,
>750 doesn't cut it.  (Note that all the .forwards are set to 644).  The
>users all have the same group id, 'group'.  Normally, 'mmdf' has the group
>id 'mmdf' in /etc/passwd, and is listed as part of 'group' in /etc/group. 
>When logged in as 'mmdf' I can read everyone's .forward properly.  But
>msg.log from MMDF has lines like: 
>
>[SYSERR(13)Permission denied]  lc_forward: stat(/u/gunther/.forward)
>
>whenever a message goes to an account with a .forward.  I have tried 
>setting the /etc/passwd group designation of 'mmdf' to 'group' and that 
>hasn't helped either.  It's like the system is ignoring group permissions 
>on the directories, so that only world file-searching (--x) permission 
>allows MMDF to get to the .forward, which it can then read because of 
>world-readability on the file.

I suspect that the confusion is related to the use of supplemental groups.
Permissions are mapped to the users/programs [RE]UID and [RE]GID.  For
users that have logged into the system, there is support for supplemental
groups, but I don't think that applies to the mmdf programs.  So, the GID
for the mmdf programs default to mmdf.

If it is true that supplemental groups do not apply to the mmdf programs
(since they are not logged in, per se), then removing the directory search
permissions on the home directory would have the described effect (EACCESS
is returned, errno 13).

This is my reading of the situation.  Since the delivery programs are started
up at boot time, they may not (and it appears that they don't) use
supplemental groups.  This would explain the ability to read the files while
logged on as mmdf but not via the delivery programs.
--
Jim Sullivan				
SCO Canada, Inc. Toronto, Ontario	 "I like picking up five 'cause it
jim@sco.com, ...!uunet!scocan!jim	  gives me more miss-a-turns" -Hilary,
416 922 1937 (8397 for fax)	 	  beating her dad in Crazy-8s

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