Docker link expose MySQL/MariaDB root password on phpinfo() via MYSQLIP_ENV_MYSQL_ROOT_PASSWORD

alright. today I'm on a verbal puking spree! This is another scary security risk with the official docker MariaDB container if you are using a docker link. And if you are wondering what the heck is a docker link, it's basically the command you use to link one docker container to another. for example,

docker run -it --restart=always --name phpfpm \
--link mariadb:ip \
-v /root/www:/home \
-w /home claylua/phpfpm:7.0.29-fpm-alpine3.4

where I am linking MariaDB to my PHP-fpm container.

This is practically what everyone does without noticing that your PHP application actually exposes MariaDB root password for everyone to see with the variable "MYSQLIP_ENV_MYSQL_ROOT_PASSWORD".

As you can see, my root password is visible for all to see. And this is NOT good at all.


In order to resolve this issue, we need to wrap all our containers into their own private network. We can create a private network in docker with the following command,

docker network create hungred

Now, we have a new network called 'hungred'. And in order for every container to talk in secret, we need them to all use this network. Anyone outside of this network will not be able to communicate with other dockerscontainer. Thus, throwing a 502 error or Nginx error or anything that you'll not expect.

Now, for our example, we will join the hungred network with the following command,

--net=hungred \
--link mariadb:ip \
-v /root/www:/home \

where our phpfpm container now runs in the hungred network.

And if you try to run phpinfo() on your application, you won't be able to find the variable "MYSQLIP_ENV_MYSQL_ROOT_PASSWORD" anymore!

P.S: Do take note that ALL your dockers will have to join the same network or else you'll get a lot of unnecessary hiccups.

Setting correct permission for Docker PHP-FPM on mounted folder

Now, if you have followed my guide on setting up Docker with PHP-FPM then you'll most likely face this issue where your files and directories permission will have to set to 777 in order for docker to write files to your mounted folder.

In order to resolve this, you'll need to reset your 777 mistakes using the command given in my reset files/directories permission article.

Once you've done that, you'll be back to your square one where your application can't write to your mounted folder.

Now, in your mounted folder assuming its in /root/www you'll need to look for the user that exec your php script in your php-fpm docker. By default its www-data (dahhh). So let's find out what this user id is on the parent machine by firing the following docker command

docker exec phpfpm id www-data

where phpfpm is the docker name of your PHP-FPM container. If you are not using PHP-FPM on a separate container, you can easily just replace phpfpm to your LEMP/LAMP docker container name.

and the above will show you something like this

[email protected]:~# docker exec phpfpm id www-data
uid=82(www-data) gid=82(www-data) groups=82(www-data),82(www-data)

the above means that on the parent machine, the user id for www-data is 82. Now, go ahead and change the user permission on your mounted folder to 82 with the following command

chown 82:82 -r /root/www

where /root/www is the example mounted folder used in this article.

Now, with the correct user permission, your application should be able to write correctly without the need to set your directories permissions to 777 which is pretty insecure.

Hope this helps.

Error response from daemon: Container xxxxxx is already active

If you face this issue where it said "Error response from daemon: Container xxxxxx is already active", and your Container is unable to start, the only way it seems to work for me, is to do the following

sudo service docker restart

and the so call 'active' container will starts itself, using other command fails to start this baby up.