Procmail can't create mailbox

[Rick Stevens]

Bob McClure Jr wrote:
> On Mon, Dec 01, 2008 at 01:21:50PM -0800, Rick Stevens wrote:
>> Bob McClure Jr wrote:
>>> On Mon, Dec 01, 2008 at 10:11:08AM -0800, Rick Stevens wrote:
>>>> Bob McClure Jr wrote:
>>>>> On Sat, Nov 29, 2008 at 09:28:38AM -0500, Mark Corsi wrote:
>>>>>> My guess is that the server is seeing the process as 'other'. This leaves
>>>>>> two solutions. One is to start the process with sudo so it starts as root. I
>>>>>> would hazard a guess that this would open up an unexpected security hole
>>>>>> since this is a mail process. The other solution is to make the process
>>>>>> owner part of the group that owns that folder and make the folder group
>>>>>> writable. Pretty sure the second solution will maintain security while
>>>>>> accomplishing your goal.
>>>>> Well, I already have a sufficiently secure work-around, but that works
>>>>> around a symptom.  I want to find out why an out-of-the-box
>>>>> configuration quit working.
>>>> Were there any diagnostics in the logs that may be of use?
>>> Only
>>>
>>> Nov 28 18:45:46 lfvsfcp19080 postfix/local[30613]: 759B024035:
>>> to=<bmcclure at dn.net>, orig_to=<root at dn.net>, relay=local, delay=3,
>>> delays=0/0/0/3, dsn=5.2.0, status=bounced (can't create user output
>>> file. Command output: procmail: Couldn't create "/var/mail/bmcclure" )
>>>
>>>> Did you
>>>> check /usr/bin/procmail and verified it was rwxr-xr-x (755), owned by
>>>> root, group of mail?
>>> -rwxr-xr-x 1 root mail 99128 Jul 12  2006 /usr/bin/procmail
>>>
>>>> Yes, /var/mail is a symlink to /var/spool/mail and
>>>> the link should be mode rwxrwxrwx (777).
>>> lrwxrwxrwx 1 root root 10 Nov 21 20:43 /var/mail -> spool/mail
>>>
>>>> /var/spool/mail itself should be owned by root, group of mail with mode
>>>> rwxrwxr-x (775).
>>> drwxrwxr-x 2 root mail 4096 Nov 28 04:02 /var/spool/mail
>>>
>>>> The files below that should be owned by the user whose
>>>> mailbox it is, group of mail with mode rw-rw---- (660).
>>> -rw------- 1 root root 0 Nov 28 04:02 root
>>> -rw-rw---- 1 root mail 0 Nov 21 20:52 root2
>>> -rw-rw---- 1 rpc  mail 0 Nov 21 20:47 rpc
>>>
>>>> I know of no extra things that may be affected by the addition of a user
>>>> via the "adduser" scripts that wouldn't be handled IF all of the user-
>>>> related files (home directories, hidden files, etc.) are present.
>>> drwx------ 25 bmcclure bmcclure 12288 Dec  1 04:02 /home/bmcclure
>>> -rw-r--r-- 1 bmcclure apache 1716 Nov 28 21:40 /home/bmcclure/.procmailrc
>>>
>>> I am mystified.
>> Have you tried (as root):
>>
>> 	touch /var/mail/bmcclure
>> 	chown bmcclure:mail /var/mail/bmcclure
>> 	chmod 660 /var/mail/bmcclure
> 
> Yeah, I know that works.
> 
>> Not sure if the adduser scripts create the empty mailbox or not.
> 
> Hmm.  I've been assuming that it doesn't, but I just looked at
> /etc/defaults/useradd, and indeed:
> 
> # useradd defaults file
> GROUP=100
> HOME=/home
> INACTIVE=-1
> EXPIRE=
> SHELL=/bin/bash
> SKEL=/etc/skel
> CREATE_MAIL_SPOOL=yes
> 
>> They
>> may...check that, they do.  One of the possible exit values for useradd
>> is:
>>
>> 	13 can’t create mail spool
>>
>> Ok, now THAT'S subtle to find!
> 
> Well, that would explain this server, and I know just how to fix it.
> Now I have to go back to the others, because, on at least one of them,
> useradd was not creating the mailbox.  Gotta verify that's the case
> and fix that.
> 
> Thanks for the clue.

No problem.  IIRC, procmail runs as the recipient's user and group.  I
believe some systems have the procmail binary's set-group-ID bit set
("chmod g+s /usr/bin/procmail") which would make it run as group "mail".
That'd get around the lack of a world-write bit set on /var/spool/mail.
For the machines where it worked, see if that's true.  procmail would
show up "rwxr-sr-x", I think.
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- Rick Stevens, Systems Engineer                      ricks at nerd.com -
- AIM/Skype: therps2        ICQ: 22643734            Yahoo: origrps2 -
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-  Unfortunately they use Borg to do their marketing and Ferengi to  -
-               do their programming."  -- Simon Slavin              -
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