Bug#797653: apache2-mpm-itk: Cant send emails from PHP script, when install mpm-itk and exim4.

[Stefan Fritsch <sf@sfritsch.de>]

On Tuesday 01 September 2015 13:35:11, Vitaliy Okulov wrote:
>    * What led up to the situation?
> Install apache2-mpm-itk and exim4. Configure apache vhost to some
> user and group.
> 
>    * What exactly did you do (or not do) that was effective (or
>      ineffective)?
> Add vhost, set AssignUserID to this vhost to some new user and
> group. Create php script for this vhost with text:
> <?php
> var_dump(mail('admin@vokulov.ru', 'test message from server', 'self
> testing')); ?>
> Then just open script from browser.
> 
>    * What was the outcome of this action?
> bool(False) and error in /var/log/exim4/paniclog:
> 2015-09-01 13:13:51 unable to set gid=1001 or uid=0 (euid=0):
> forcing real = effective

I fear this is a security feature in recent mpm-itk versions: It 
prevents changing uid to root, which was a significant security issue 
in previous versions.

To work around it, you would have to change your php or php-apps to 
send mails via SMTP to localhost instead of invoking /usr/lib/sendmail 
directly. I can't give any advice on how to do that, though. Or maybe 
there is some way to install some minimal MTA like ssmtp or nullmailer 
as /usr/lib/sendmail that forwards the mail to exim via SMPT. Not sure 
how easy it is to install those parallel to exim, though. Maybe it 
could work by diverting exim's /usr/lib/sendmail .

Cheers,
Stefan