Bug 466235 - SELinux is preventing master (postfix_master_t) "write" to ./postfix (var_lib_t)
SELinux is preventing master (postfix_master_t) "write" to ./postfix (var_lib_t)
Product: Fedora
Classification: Fedora
Component: selinux-policy-targeted (Show other bugs)
All Linux
medium Severity high
: ---
: ---
Assigned To: Daniel Walsh
Ben Levenson
: 466609 466664 (view as bug list)
Depends On:
  Show dependency treegraph
Reported: 2008-10-09 06:26 EDT by Dave Mitchell
Modified: 2008-11-26 12:37 EST (History)
9 users (show)

See Also:
Fixed In Version: F8
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2008-11-26 12:37:51 EST
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Dave Mitchell 2008-10-09 06:26:14 EDT
Description of problem:

After update, postfix refuses to start, with selinux error

Version-Release number of selected component (if applicable):


How reproducible:

Steps to Reproduce:
1. yum update postfix
Actual results:

Oct  9 09:44:58 pigeon setroubleshoot: SELinux is preventing master (postfix_master_t) "write" to ./postfix (var_lib_t). For complete SELinux messages. run sealert -l 248b64c2-270e-4ed2-b2ab-7c03ade2c8b6

Expected results:

postfix to start without errors

Additional info:

[root@pigeon lib]# ls -ldZ /var/lib/postfix/
drwx------  postfix root system_u:object_r:var_lib_t:s0   /var/lib/postfix/
[root@pigeon lib]# sealert -l 248b64c2-270e-4ed2-b2ab-7c03ade2c8b6


SELinux is preventing master (postfix_master_t) "write" to ./postfix

Detailed Description:

SELinux is preventing master (postfix_master_t) "write" to ./postfix
(var_lib_t). The SELinux type var_lib_t, is a generic type for all files in the
directory and very few processes (SELinux Domains) are allowed to write to this
SELinux type. This type of denial usual indicates a mislabeled file. By default
a file created in a directory has the gets the context of the parent directory,
but SELinux policy has rules about the creation of directories, that say if a
process running in one SELinux Domain (D1) creates a file in a directory with a
particular SELinux File Context (F1) the file gets a different File Context
(F2). The policy usually allows the SELinux Domain (D1) the ability to write,
unlink, and append on (F2). But if for some reason a file (./postfix) was
created with the wrong context, this domain will be denied. The usual solution
to this problem is to reset the file context on the target file, restorecon -v
'./postfix'. If the file context does not change from var_lib_t, then this is
probably a bug in policy. Please file a bug report
(http://bugzilla.redhat.com/bugzilla/enter_bug.cgi) against the selinux-policy
package. If it does change, you can try your application again to see if it
works. The file context could have been mislabeled by editing the file or moving
the file from a different directory, if the file keeps getting mislabeled, check
the init scripts to see if they are doing something to mislabel the file.

Allowing Access:

You can attempt to fix file context by executing restorecon -v './postfix'

The following command will allow this access:

restorecon './postfix'

Additional Information:

Source Context                system_u:system_r:postfix_master_t:s0
Target Context                system_u:object_r:var_lib_t:s0
Target Objects                ./postfix [ dir ]
Source                        master
Source Path                   /usr/libexec/postfix/master
Port                          <Unknown>
Host                          pigeon
Source RPM Packages           postfix-2.5.5-1.fc8
Target RPM Packages           
Policy RPM                    selinux-policy-3.0.8-117.fc8
Selinux Enabled               True
Policy Type                   targeted
MLS Enabled                   True
Enforcing Mode                Enforcing
Plugin Name                   mislabeled_file
Host Name                     pigeon
Platform                      Linux pigeon #1 SMP Sat Sep 20
                              09:32:58 EDT 2008 i686 i686
Alert Count                   1
First Seen                    Thu Oct  9 09:44:58 2008
Last Seen                     Thu Oct  9 09:44:58 2008
Local ID                      248b64c2-270e-4ed2-b2ab-7c03ade2c8b6
Line Numbers                  

Raw Audit Messages            

host=pigeon type=AVC msg=audit(1223541898.350:448): avc:  denied  { write } for  pid=8231 comm="master" name="postfix" dev=dm-2 ino=1900694 scontext=system_u:system_r:postfix_master_t:s0 tcontext=system_u:object_r:var_lib_t:s0 tclass=dir

host=pigeon type=SYSCALL msg=audit(1223541898.350:448): arch=40000003 syscall=5 success=no exit=-13 a0=b8985850 a1=c2 a2=1a4 a3=0 items=0 ppid=1 pid=8231 auid=500 uid=0 gid=0 euid=89 suid=0 fsuid=89 egid=89 sgid=0 fsgid=89 tty=(none) ses=2 comm="master" exe="/usr/libexec/postfix/master" subj=system_u:system_r:postfix_master_t:s0 key=(null)

[root@pigeon lib]#
Comment 1 Thomas Woerner 2008-10-09 07:57:29 EDT
The context for /var/lib/postfix needs to get changed in selinux-policy-targeted for the new postfix package.

As an interim solution you could set the context of /var/lib/postfix to system_u:object_r:postfix_var_lib_t:s0 with chcon.

Reassigning to selinux-policy-targeted.
Comment 2 Eric Hopper 2008-10-10 11:35:29 EDT
Except, the context system_u:object_r:postfix_var_lib_t:s0 doesn't exist in the current Fedora 8 selinux-policy-targeted package so doing that will fail.
Comment 3 Eric Hopper 2008-10-10 11:43:20 EDT
There is a magic dance some nice person (domg472) in #selinux gave me:

First, make sure selinux-policy-devel is installed.

mkdir ~/mypostfix
cd ~/mypostfix
vi mypostfix.te
policy_module(mypostfix, 0.0.1)
type postfix_var_lib_t;
require { type postfix_master_t; }
manage_dirs_pattern(postfix_master_t, postfix_var_lib_t, postfix_var_lib_t)
manage_files_pattern(postfix_master_t, postfix_var_lib_t, postfix_var_lib_t)
make -f /usr/share/selinux/devel/Makefile
/usr/sbin/semodule -i mypostfix.pp
/usr/sbin/semanage fcontext -a -t postfix_var_lib_t "/var/lib/postfix(/.*)?"
restorecon -vR /var/lib/postfix
Comment 4 Dave Mitchell 2008-10-11 13:39:52 EDT
That hack has taken me a bit further; now I get a new error trying to start postfix:

Oct 11 17:45:39 pigeon setroubleshoot: SELinux is preventing postfix (sendmail_t) "execute" to ./postfix-script (postfix_exec_t). For complete SELinux messages. run sealert -l b5b91e16-8a62-499a-bfd2-7c875c8d256e

[root@pigeon mypostfix]# ls -lZ /etc/postfix/postfix-script 
-rwxr-xr-x  root root system_u:object_r:postfix_exec_t:s0 /etc/postfix/postfix-script

[root@pigeon mypostfix]# sealert -l b5b91e16-8a62-499a-bfd2-7c875c8d256e


SELinux is preventing postfix (sendmail_t) "execute" to ./postfix-script

Detailed Description:

SELinux denied access requested by postfix. It is not expected that this access
is required by postfix and this access may signal an intrusion attempt. It is
also possible that the specific version or configuration of the application is
causing it to require additional access.

Allowing Access:

Sometimes labeling problems can cause SELinux denials. You could try to restore
the default system file context for ./postfix-script,

restorecon -v './postfix-script'

If this does not work, there is currently no automatic way to allow this access.
Instead, you can generate a local policy module to allow this access - see FAQ
(http://fedora.redhat.com/docs/selinux-faq-fc5/#id2961385) Or you can disable
SELinux protection altogether. Disabling SELinux protection is not recommended.
Please file a bug report (http://bugzilla.redhat.com/bugzilla/enter_bug.cgi)
against this package.

Additional Information:

Source Context                system_u:system_r:sendmail_t:s0
Target Context                system_u:object_r:postfix_exec_t:s0
Target Objects                ./postfix-script [ file ]
Source                        postfix
Source Path                   /usr/sbin/postfix
Port                          <Unknown>
Host                          pigeon
Source RPM Packages           postfix-2.5.5-1.fc8
Target RPM Packages           
Policy RPM                    selinux-policy-3.0.8-117.fc8
Selinux Enabled               True
Policy Type                   targeted
MLS Enabled                   True
Enforcing Mode                Enforcing
Plugin Name                   catchall_file
Host Name                     pigeon
Platform                      Linux pigeon #1 SMP Sat Sep 20
                              09:32:58 EDT 2008 i686 i686
Alert Count                   3
First Seen                    Sat Oct 11 17:37:56 2008
Last Seen                     Sat Oct 11 17:45:39 2008
Local ID                      b5b91e16-8a62-499a-bfd2-7c875c8d256e
Line Numbers                  

Raw Audit Messages            

host=pigeon type=AVC msg=audit(1223743539.224:781): avc:  denied  { execute } for  pid=521 comm="postfix" name="postfix-script" dev=dm-2 ino=1836888 scontext=system_u:system_r:sendmail_t:s0 tcontext=system_u:object_r:postfix_exec_t:s0 tclass=file

host=pigeon type=SYSCALL msg=audit(1223743539.224:781): arch=40000003 syscall=11 success=no exit=-13 a0=b9052c30 a1=bff71604 a2=b9052b50 a3=b9052c30 items=0 ppid=1 pid=521 auid=500 uid=0 gid=0 euid=0 suid=0 fsuid=0 egid=0 sgid=0 fsgid=0 tty=pts1 ses=2 comm="postfix" exe="/usr/sbin/postfix" subj=system_u:system_r:sendmail_t:s0 key=(null)
Comment 5 Dave Mitchell 2008-10-12 07:06:01 EDT
ignore my previous comment. For some reason I was typing
    service sendmail start
rather than
    service postfix start
D'oh! Works now.
Comment 6 Thomas Woerner 2008-10-14 06:51:21 EDT
*** Bug 466609 has been marked as a duplicate of this bug. ***
Comment 7 Thomas Woerner 2008-10-14 06:51:47 EDT
*** Bug 466664 has been marked as a duplicate of this bug. ***
Comment 8 Daniel Walsh 2008-10-14 21:14:05 EDT
I believe this might be fixed in selinux-policy-3.0.8-118.fc8  I have upgraded to the f9 policy for postfix.  The real problem here might be that you have the postfix executable running as sendmail_t?
Comment 9 Scott Schmit 2008-10-14 22:00:50 EDT
No, if you look carefully at the comments, Dave and I both got bitten by the lack of a postfix_var_lib_t and associated rules. The instructions in Comment #3 fixed that for me and Dave both. However, as Dave explained in Comment #5, he thought he had other problems on top of that, but was typing the wrong command.

If there is any lingering doubt:
$ ps -eo user,label,command|grep postfix|grep -v grep
root     unconfined_u:system_r:postfix_master_t /usr/libexec/postfix/master
postfix  unconfined_u:system_r:postfix_qmgr_t qmgr -l -t fifo -u
postfix  unconfined_u:system_r:postfix_pickup_t pickup -l -t fifo -u

(unconfined_u because I started the service after bootup, due to the aforementioned selinux-policy-targeted bug).

What I'm curious about is how to handle the custom policy/fcontext rules when the new update is installed. Will the custom policy/fcontext rules get thrown out? Will it conflict? Will I need to uninstall it first?
Comment 10 Daniel Walsh 2008-10-15 09:08:29 EDT
Ok I looked again and made an update to selinux-policy-3.0.8-119.fc8
WHich allows sendmail_t to transition to postfix_master_t as it does in F9 and F10.

This package should be in Fedora Testing soon, or you can grab it from koji.
Comment 11 Bug Zapper 2008-11-26 06:14:12 EST
This message is a reminder that Fedora 8 is nearing its end of life.
Approximately 30 (thirty) days from now Fedora will stop maintaining
and issuing updates for Fedora 8.  It is Fedora's policy to close all
bug reports from releases that are no longer maintained.  At that time
this bug will be closed as WONTFIX if it remains open with a Fedora 
'version' of '8'.

Package Maintainer: If you wish for this bug to remain open because you
plan to fix it in a currently maintained version, simply change the 'version' 
to a later Fedora version prior to Fedora 8's end of life.

Bug Reporter: Thank you for reporting this issue and we are sorry that 
we may not be able to fix it before Fedora 8 is end of life.  If you 
would still like to see this bug fixed and are able to reproduce it 
against a later version of Fedora please change the 'version' of this 
bug to the applicable version.  If you are unable to change the version, 
please add a comment here and someone will do it for you.

Although we aim to fix as many bugs as possible during every release's 
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The process we are following is described here: 
Comment 12 Jon Stanley 2008-11-26 12:37:51 EST
As this bug is in MODIFIED, Fedora believes that a fix has been committed that resolves the problem listed in this bug report.

If this is not the case, please re-open this report, noting the version of the package that you reproduced the bug against.

Thanks for the report!

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