oddity with postfix delivering to homedir
Daniel J Walsh
dwalsh at redhat.com
Tue Feb 17 17:59:58 UTC 2009
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Manuel Wolfshant wrote:
> Daniel J Walsh wrote:
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>> Manuel Wolfshant wrote:
>>
>>> Daniel J Walsh wrote:
>>>
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>>>> 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 at 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 at imap2 ~]# ll -Zl /home/gigi.test\@nobugconsulting.ro/ -R
>>>>> /home/gigi.test at nobugconsulting.ro/: total
>>>>> 8 drwx------ 2
>>>>> root:object_r:home_root_t postfix postfix 4096 Feb 17 01:05 tmp
>>>>>
>>>>> /home/gigi.test at nobugconsulting.ro/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 at imap2 ~]# restorecon -v -R
>>>>> /home/gigi.test at nobugconsulting.ro
>>>>> restorecon reset /home/gigi.test at nobugconsulting.ro context
>>>>> root:object_r:home_root_t:s0->user_u:object_r:user_home_dir_t:s0
>>>>> restorecon reset /home/gigi.test at nobugconsulting.ro/tmp context
>>>>> root:object_r:home_root_t:s0->user_u:object_r:user_home_t:s0
>>>>> restorecon reset
>>>>> /home/gigi.test at nobugconsulting.ro/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 at 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 at 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 at imap2 ~]# ls -l /home/ -dZ
>>>>> drwxr-xr-x+ postfix postfix system_u:object_r:home_root_t /home/
>>>>> [root at imap2 ~]# ls -l /home/gigi.test\@nobugconsulting.ro/ -dZ
>>>>> drwx------ postfix postfix user_u:object_r:user_home_dir_t
>>>>> /home/gigi.test at nobugconsulting.ro/
>>>>>
>>>>> The only user on the system (beside root) is postfix:
>>>>> [root at imap2 ~]# getent passwd postfix
>>>>> postfix:x:89:89::/var/spool/postfix:/sbin/nologin
>>>>>
>>>>> raw content of audit log after a failed delivery for a never-seen
>>>>> before user:
>>>>> type=AVC msg=audit(1234873447.682:45616): avc: denied { write } for
>>>>> pid=2958 comm="virtual"
>>>>> path="/home/gigi.test at nobugconsulting.ro/tmp/1234873447.P2958.imap2"
>>>>> dev=hda1 ino=2736137 scontext=root:system_r:postfix_virtual_t:s0
>>>>> tcontext=root:object_r:home_root_t:s0 tclass=file
>>>>> type=SYSCALL msg=audit(1234873447.682:45616): arch=c000003e syscall=1
>>>>> success=no exit=-13 a0=c a1=2b96176fe510 a2=1b5 a3=7228206f722e676e
>>>>> items=0 ppid=26787 pid=2958 auid=0 uid=0 gid=0 euid=89 suid=0 fsuid=89
>>>>> egid=89 sgid=0 fsgid=89 tty=(none) ses=7290 comm="virtual"
>>>>> exe="/usr/libexec/postfix/virtual"
>>>>> subj=root:system_r:postfix_virtual_t:s0 key=(null)
>>>>> type=AVC msg=audit(1234873447.710:45617): avc: denied { write } for
>>>>> pid=2958 comm="virtual" name="1234873447.P2958.imap2" dev=hda1
>>>>> ino=2736137 scontext=root:system_r:postfix_virtual_t:s0
>>>>> tcontext=root:object_r:home_root_t:s0 tclass=file
>>>>> type=SYSCALL msg=audit(1234873447.710:45617): arch=c000003e syscall=77
>>>>> success=no exit=-13 a0=c a1=0 a2=2 a3=0 items=0 ppid=26787 pid=2958
>>>>> auid=0 uid=0 gid=0 euid=89 suid=0 fsuid=89 egid=89 sgid=0 fsgid=89
>>>>> tty=(none) ses=7290 comm="virtual" exe="/usr/libexec/postfix/virtual"
>>>>> subj=root:system_r:postfix_virtual_t:s0 key=(null)
>>>>> type=AVC msg=audit(1234873447.710:45618): avc: denied {
>>>>> remove_name }
>>>>> for pid=2958 comm="virtual" name="1234873447.P2958.imap2"
>>>>> dev=hda1ino=2736137 scontext=root:system_r:postfix_virtual_t:s0
>>>>> tcontext=root:object_r:home_root_t:s0 tclass=dir
>>>>> type=SYSCALL msg=audit(1234873447.710:45618): arch=c000003e syscall=87
>>>>> success=no exit=-13 a0=2b96176fdb80 a1=64 a2=4 a3=2b95fb0340ec items=0
>>>>> ppid=26787 pid=2958 auid=0 uid=0 gid=0 euid=89 suid=0 fsuid=89 egid=89
>>>>> sgid=0 fsgid=89 tty=(none) ses=7290 comm="virtual"
>>>>> exe="/usr/libexec/postfix/virtual"
>>>>> subj=root:system_r:postfix_virtual_t:s0 key=(null)
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> 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
>
> --
> fedora-selinux-list mailing list
> fedora-selinux-list at redhat.com
> https://www.redhat.com/mailman/listinfo/fedora-selinux-list
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.
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