Manuel Wolfshant wrote:
On 02/17/2009 07:59 PM, Daniel J Walsh wrote:
Manuel Wolfshant wrote:
Daniel J Walsh wrote:
Manuel Wolfshant wrote:
Daniel J Walsh wrote:
Manuel Wolfshant wrote:
hello
I have migrated a working mailserver from Centos 4.7 to Centos
5.2.
The system uses postfix to receive messages from a mail relay and is
supposed to deliver them to folders named after the users,
following
the /home/firstname.lastname@domain template. Authentication is
done via
mysql against a db running on another system.
New accounts are created automatically when a mail has to be
delivered to an user which has never been seen before.
For the users which existed before migration, everything is fine.
However, for non-existing (i.e. to be created) users the homedir is
created with wrong contexts, which prohibit postfix to finalize the
delivery. Once a message is received for a new user, the
following is
created:
[root@imap2 ~]# ll -Zl /home/gigi.test\@nobugconsulting.ro/ -R
/home/gigi.test@xxxxxxxxxxxxxxxxxx/: total
8 drwx------ 2
root:object_r:home_root_t postfix postfix 4096 Feb 17
01:05 tmp
/home/gigi.test@xxxxxxxxxxxxxxxxxx/tmp:
total 4 -rw------- 1
root:object_r:home_root_t postfix postfix 0 Feb 17 01:05
1234825528.P26797.imap2
After that postfix tries to do stuff on the newly created file
and
selinux kicks in and denies access.
Running restorecon at this point fixes things:
[root@imap2 ~]# restorecon -v -R
/home/gigi.test@xxxxxxxxxxxxxxxxxx
restorecon reset /home/gigi.test@xxxxxxxxxxxxxxxxxx context
root:object_r:home_root_t:s0->user_u:object_r:user_home_dir_t:s0
restorecon reset /home/gigi.test@xxxxxxxxxxxxxxxxxx/tmp context
root:object_r:home_root_t:s0->user_u:object_r:user_home_t:s0
restorecon reset
/home/gigi.test@xxxxxxxxxxxxxxxxxx/tmp/1234825528.P26797.imap2
context
root:object_r:home_root_t:s0->user_u:object_r:user_home_t:s0
I am running the following versions of packages:
[root@imap2 ~]# rpm -qa kernel\* \*selinux\* postfix\*
kernel-xen-2.6.18-92.1.22.el5
libselinux-utils-1.33.4-5.1.el5
selinux-policy-targeted-2.4.6-203.el5
libselinux-1.33.4-5.1.el5
libselinux-python-1.33.4-5.1.el5
selinux-policy-2.4.6-203.el5
postfix-2.3.3-2.1.centos.mysql_pgsql
Selinux related packages have been upgraded last night in the
hope to
fix the problem, postfix is almost stock centosplus 5.2, recompiled
with
support for mysql but without postgresql- support.
Obviously I no not want to follow the result of audit2allow,
home_root_t:dir should not be there in the first place:
[root@imap2 ~]# grep avc /var/log/audit/audit.log|audit2allow
#============= postfix_virtual_t ==============
allow postfix_virtual_t home_root_t:dir { write remove_name create
add_name };
allow postfix_virtual_t home_root_t:file { write create unlink link
getattr };
allow postfix_virtual_t postfix_private_t:dir search;
allow postfix_virtual_t postfix_private_t:sock_file write;
allow postfix_virtual_t usr_t:file { read getattr };
Correct access rights and contexts seem to be:
[root@imap2 ~]# ls -l /home/ -dZ
drwxr-xr-x+ postfix postfix system_u:object_r:home_root_t /home/
[root@imap2 ~]# ls -l /home/gigi.test\@nobugconsulting.ro/ -dZ
drwx------ postfix postfix user_u:object_r:user_home_dir_t
/home/gigi.test@xxxxxxxxxxxxxxxxxx/
The only user on the system (beside root) is postfix:
[root@imap2 ~]# getent passwd postfix
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
[...]
My questions are
a) why does postfix create the initial home directories with a wrong
context ? Note this only happens for NEW users, messages for the
users
which already existed [and have correct context] on the old
system are
perfectly fine.
Does postfix actually create the homedir or was the homedir
created by
an init script? postfix does not know anything about SELinux but
there
are rules about processes running as postfix_t creating files in
user_home_dir_t directories. In your case it seems that the
directory
was labeled home_root_t, which is where the problem is.
/home exists; everything below it is created (and should be created
with correct contexts) by postfix in real time
Why is postfix creating a homedir?
Because that's where all the virtual users have their mails.
I have never seen this before.
That is where the problem is, selinux policy does not allow postfix to
create directories under /home (home_root_t), so it is being blocked.
I am sorry, I do not remember from which site was the setup taken. 4
years or so since I installed it the first time in Centos 4.2, but if I
am not mistaken it's an almost exact replica of the setup suggested by
postfixadmin
So postfix_virtual creates the homedir just to put a file in it and then
send it somewhere else?
If this is standard I can allow it, although it seems pretty strange.
To be honest, I am not 100% sure how standard that is, although I am
pretty sure that delivering to home dirs is not uncommon. Fact is that
(in my case) postfix is the only user on the box and owns all the
directories created below /home. Technically I presume that the whole
structure could be moved anywhere else, but 4 years ago /home seemed a
logical place, even if all users are virtual and defined in mysql.
Basically when doing a deliver, postfix uses maildirmake to create the
top-level directory assigned to any specific user, leading to a tree
like this:
/home
/home/specific.user
/home/specific.user/cur (cur stands for current)
/home/specific.user/tmp
/home/specific.user/new
The structure gets created when the very first message for a user is
received.
As far as I have understood (it always "just worked" so I never did
in-depth digging), messages are first created in /home/specific.user/tmp
and after that copied to the final delivery place i.e.
/home/specific.user/new. Once the user reads the message (via an imap /
pop daemon), the message is transferred to /home/specific.user/cur (or
to other folders, created via the IMAP daemon, but all of them placed
below /home/specific.user)
This looks like standard delivery to maildir operation, with the
addition of having the mailboxes in virtual user home directories under
/home that are auto-created when necessary.
Given that there are no other users on the system, I wonder if
everything would work smoothly if you made /home and everything
underneath it mail_spool_t ?
Paul.
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