Re: SELinux blocking Dovecot from mysqld socket

Lukas Vrabec <[email protected]> Wed, 6 Feb 2019 11:04:29 +0100
Newsgroups	gmane.linux.redhat.fedora.selinux
Organization	Red Hat, Inc.
Message-ID	<[email protected]>
On 2/6/19 10:59 AM, Ondrej Mosnacek wrote:
> On Tue, Feb 5, 2019 at 6:57 PM Robert Moskowitz <[email protected]> wrote:
>> On 2/5/19 10:41 AM, Ondrej Mosnacek wrote:
>>> On Tue, Feb 5, 2019 at 2:54 PM Robert Moskowitz <[email protected]> wrote:
>>>>
>>>>
>>>> On 2/5/19 3:23 AM, Zdenek Pytela wrote:
>>>>
>>>>
>>>>
>>>> On Mon, Feb 4, 2019 at 9:03 PM Robert Moskowitz <[email protected]> wrote:
>>>>> I am working with Centos7:
>>>>>
>>>>> I have configured Dovecot to connect to mysqld via socket:
>>>>>
>>>>> connect = host=/var/lib/mysql/mysql.sock dbname=postfix user=postfix
>>>>> password=Postfix_Database_Password
>>>>>
>>>>> I test sending a message with
>>>>>
>>>>> sendmail -i [email protected] < README
>>>>>
>>>>> This fails with the following message in maillog
>>>>>
>>>>> Feb  4 11:28:48 klovia dovecot: dict(13122): Error:
>>>>> mysql(/var/lib/mysql/mysql.sock): Connect failed to database (postfix):
>>>>> Can't connect to local MySQL server through socket
>>>>> '/var/lib/mysql/mysql.sock' (13) - waiting for 25 seconds before retry
>>>>>
>>>>> If I setenforce to 0, the connection works.  So it clearly is an SELinux
>>>>> problem.  I worked on this almost 2 years ago on another system and found:
>>>>>
>>>>> http://zszsit.blogspot.com/2012/12/dovecot-mysql-selinux-issue-on-centos6.html
>>>>>
>>>>> But I was hoping that there were better tools now with Centos7.  I
>>>>> checked for setsebool at:
>>>>>
>>>>> https://linux.die.net/man/8/mysqld_selinux
>>>>>
>>>>> and tried:
>>>>>
>>>>> setsebool -P allow_user_mysql_connect 1
>>>>>
>>>>> But the mail still does not go unless I setenforce to 0.
>>>> Hi,
>>>>
>>>> this boolean allows a different permission - see the manual page:
>>>>>> If you want to allow users to connect to mysql, you must turn on the allow_user_mysql_connect boolean.
>>>>> Is there someway to get SELinux to allow dovecot (and postfix) to
>>>>> connect to mysqld?
>>>> While dovecot is allowed to connect to postgresql port, there is no similar permission for mysql:
>>>>
>>>> # sesearch -A -s dovecot_t -c tcp_socket -p name_connect | grep sql
>>>> allow dovecot_t postgresql_port_t:tcp_socket name_connect;
>>>>
>>>> However, if this permission is the only one missing, you can simply add it with:
>>>>
>>>> # echo '(allow dovecot_t mysqld_port_t (tcp_socket (name_connect)))' > dovecot-mysql.cil
>>>> # semodule -i dovecot-mysql.cil
>>>> # sesearch -A -s dovecot_t -c tcp_socket -p name_connect | grep sql
>>>> allow dovecot_t mysqld_port_t:tcp_socket name_connect;
>>>> allow dovecot_t postgresql_port_t:tcp_socket name_connect;
>>>>
>>>>
>>>> Still getting the error.  This does not seem to be what is needed.  Isn't this to open TCP access where I am using the unix socket interface?
>>> Indeed, what Zdenek advised is for allowing to connect via TCP. Could
>>> you try the following instead?
>>>
>>> dnf install selinux-policy-devel
>>
>> Nit this is CentOS7, so yum.  In fact it is CentOS7-armhfp...
>>
>>> cat >dovecot_mysql.te <<EOF
>>> policy_module(dovecot_mysql,1.0.0)
>>> gen_require(`
>>>         type dovecot_t;
>>> ')
>>> mysql_read_config(dovecot_t)
>>> mysql_stream_connect(dovecot_t)
>>> EOF
>>
>> For some reason this made an empty file.  Don't know if it was the lack
>> of spaces on that first line?  I use this myself a lot, but always put
>> spaces around the > and <<
> 
> As other have already pointed out, it was because of the unescaped
> backtick. I initially started with just the last two lines and later
> realized the other lines are also needed, so I just vim'd the file and
> copy-pasted the new contents into the e-mail without checking if it
> still works :)
> 
>>
>> So I just used vi this time.  :)
>>
>>> make -f /usr/share/selinux/devel/Makefile dovecot_mysql.pp
>>
>>> semodule -i dovecot_mysql.pp
>>
>> And the sendmail test went through with enforcing.
>>
>> thanks!
> 
> Great! I submitted a PR to allow this in Fedora policy, since it seems
> like a valid use case. Hopefully it gets to RHEL/CentOS from there
> eventually.
> 
> https://github.com/fedora-selinux/selinux-policy-contrib/pull/86
> 

Thanks Ondrej, for PR, it's already merged and back ported to Fedora 28
and Fedora 29.

https://github.com/fedora-selinux/selinux-policy-contrib/commit/e7c5f327c12dac498cfef69f9a4f9a3d57fa8677

Robert,

Do you have some more SELinux denials (AVC msgs) in audit.log after
workaround from Ondrej? If yes, please attach it , we can work on them.

Thanks,
Lukas.

> --
> Ondrej Mosnacek <omosnace at redhat dot com>
> Associate Software Engineer, Security Technologies
> Red Hat, Inc.
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> 


-- 
Lukas Vrabec
Software Engineer, Security Technologies
Red Hat, Inc.

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