Wrong value from ini_get() for shared files because of opcache optimization

Description

Opcache saves values from ini_get() for PHP_INI_SYSTEM type directives in the opcache when optimization is enabled.
This is a problem when a shared file uses ini_get() for PHP_INI_SYSTEM.

Example of this is a server with multiple virtual hosts where the sites use a common/shared framework.
The framework has an image uploading part where it fetches the upload_tmp_dir setting from ini to use a place for temporary image manipulations.
The virtual hosts are set up using PHP_ADMIN_VALUE to set a specific upload folder for each site.

fastcgi_param PHP_ADMIN_VALUE "upload_tmp_dir=/tmp/uploads/site1";

In this scenario the framework uses ini_get('upload_tmp_dir') to get the tmp folder value, but the value it gets is always the value for the first site that included that php file. So if site "foo.example.com" was first, then ALL other sites will get the upload_tmp_dir from "foo.example.com".

I reproduced this in all versions >=7.2, and for cli, fpm and mod_php.

Security

Not sure this counts as a security problem but this means that information could leak between sites.

Note that using PHP_ADMIN_VALUE for any option results in this problem.

Ways to reproduce:

Setup php files

mkdir /tmp/test/ && cd /tmp/test/
echo '<?php echo "S: " . ini_get("upload_tmp_dir") . "\n";' > shared.php
echo '<?php echo "1: " . ini_get("upload_tmp_dir") . "\n"; include "./shared.php";' > 1.php
echo '<?php echo "2: " . ini_get("upload_tmp_dir") . "\n"; include "./shared.php";' > 2.php

Cli

Create a cli-opcache.ini file in the "scan" additional .ini files directory:

zend_extension=opcache.so
[opcache]
opcache.enable=1
opcache.enable_cli=1
opcache.file_cache="/tmp/php-file-cache"
opcache.file_cache_only=1
opcache.file_cache_consistency_checks=1

Create file cache folder

mkdir /tmp/php-file-cache

Run the test

php -d upload_tmp_dir=/tmp/num1 /tmp/test/1.php
php -d upload_tmp_dir=/tmp/num2 /tmp/test/2.php

Expected result:

1: /tmp/num1
S: /tmp/num1
2: /tmp/num2
S: /tmp/num2

Actual result:

1: /tmp/num1
S: /tmp/num1
2: /tmp/num2
S: /tmp/num1

nginx + fpm

Make sure that opcache with optimizations is enabled.

Setup two virtual hosts and reload nginx:

server {
    listen 80; 
    server_name p1; 
    root /tmp/test; 
    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
	    fastcgi_pass   127.0.0.1:9000;
	    fastcgi_param  PHP_ADMIN_VALUE "upload_tmp_dir=/tmp/cache1";
    }
}

server {
    listen 80; 
    server_name p2; 
    root /tmp/test; 
    location ~ \.php$ {
	    include snippets/fastcgi-php.conf;
	    fastcgi_pass   127.0.0.1:9000;
	    fastcgi_param  PHP_ADMIN_VALUE "upload_tmp_dir=/tmp/cache2";
    }
}

Run the tests:

curl --resolve p1:80:127.0.0.1 http://p1/1.php
curl --resolve p2:80:127.0.0.1 http://p2/2.php

Expected result:

1: /tmp/cache1
S: /tmp/cache1
2: /tmp/cache2
S: /tmp/cache2

Actual result:

1: /tmp/cache1
S: /tmp/cache1
2: /tmp/cache2
S: /tmp/cache1

Workarounds

For me, I ended up with changing the shared framework, and now have to maintain my own fork of it.

You can turn off opcache optimizations.

Another way to work around this is to compile php yourself, with removing the ini_get if block, or even just
changing ini_get to ini_get_opcache_workaround in the zend_optimizer_eval_special_func_call function
in Zend/Optimizer/zend_optimizer.c.

PHP Version

7.2.0 - 8.1.6

Operating System

No response

Inizia leggendo Zend/Optimizer/zend_optimizer.c, in particolare la condizione ini_get e zend_optimizer_eval_special_func_call indicata nel report. Esegui la riproduzione CLI con opcache file caching, quindi confronta i valori attesi e quelli effettivi negli esempi shared-file e virtual-host. Il lavoro è completato quando i valori PHP_INI_SYSTEM rimangono specifici per ogni richiesta o host, mantenendo abilitata l’ottimizzazione.