[horde] IMP attachment upload limit with PHP-FPM and .user.ini

[Admin Beckspaced]

Hello there :)

I recently migrated my mail server from openSUSE Leap 15.6 to openSUSE 
Leap 16.0 and ran into a strange issue with attachment uploads in IMP.

My current setup is:

  *

    openSUSE Leap 16.0

  *

    PHP 8.4.24

  *

    Apache with proxy_fcgi and PHP-FPM

  *

    Horde: dev-FRAMEWORK_6_0 (1b16603)

  *

    IMP: dev-FRAMEWORK_6_0 (3852464)

  *

    Horde Core: 3.3.0

  *

    Horde Browser: 3.0.0

Horde is installed via Composer under:

|/srv/www/horde/httpdocs|

The active PHP-FPM configuration contained the PHP default:

|/etc/php8/fpm/php.ini: upload_max_filesize = 2M|

For the Horde installation I had a |.user.ini| in the web directory 
containing:

|upload_max_filesize = 32M post_max_size = 40M memory_limit = 128M|

I verified with a PHP test script in the same web environment that PHP 
reported these values from |.user.ini| correctly.

Nevertheless, IMP refused attachments larger than approximately 2 MB and 
displayed:

|Your attachment(s) are too large and cannot be uploaded.|

IMP itself was configured with:

|$conf['compose']['link_attachments'] = false; 
$conf['compose']['attach_size_limit'] = 0; 
$conf['compose']['attach_count_limit'] = 0;|

According to IMP's |conf.xml|, |attach_size_limit = 0| means that there 
is no IMP-specific total attachment size limit.

As a test I also explicitly set:

|$conf['compose']['attach_size_limit'] = 33554432;|

but this made no difference. IMP still rejected attachments larger than 
approximately 2 MB.

I then looked at |Horde_Browser::allowFileUploads()|. As far as I 
understand the code, the upload limit is determined from:

|ini_get('upload_max_filesize') ini_get('post_max_size')|

with the smaller value being returned.

What finally solved the problem was setting the limits directly in the 
active PHP-FPM pool configuration:

|/etc/php8/fpm/php-fpm.d/www.conf|

|php_admin_value[upload_max_filesize] = 32M 
php_admin_value[post_max_size] = 40M php_admin_value[memory_limit] = 128M|

After restarting PHP-FPM, IMP immediately accepted larger attachments. I 
successfully tested uploads with attachments of 4.4 MB and 7.1 MB.

So the practical problem is solved, but I would like to understand the 
reason for this behaviour.

The interesting point for me is that the PHP-FPM |php.ini| definitely 
contained |upload_max_filesize = 2M|, while the |.user.ini| contained 
|upload_max_filesize = 32M|. A PHP test script in the Horde web 
environment reported the 32M value correctly, but IMP still behaved as 
if the 2M value from the FPM |php.ini| was being used.

Only after setting the same 32M value as |php_admin_value| directly in 
the FPM pool did IMP accept larger attachments.

Is there anything in IMP's dynamic attachment upload handling or in 
|Horde_Browser::allowFileUploads()| that could explain why the 
|.user.ini| value appeared to be effective in a PHP test script, but IMP 
still behaved according to the 2M FPM default?

And is configuring these limits directly in the PHP-FPM pool the 
recommended way to configure Horde/IMP when using Apache with 
|proxy_fcgi| and PHP-FPM?

Thanks in advance for any hints or explanations.

Greetings
Becki