oddity with postfix delivering to homedir

[Manuel Wolfshant]

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.
b) what can I do to fix ?



    Tia
        Manuel