linuxexpert-practice-labs/labs/ubuntu-server/1-4-web-app-and-database/README.md

Ubuntu Server 1.4: A web application with a database

Apache, PHP and MySQL: a database with a read-only user, a PHP page in a virtual host of its own, and finding a broken database login in the logs.

Before you start

The lab doesn't install anything: installing Apache, PHP and MySQL is part of task 1. It checks that nothing listens on port 80 yet. Reset removes the packages installed during the lab again, with MySQL's databases.

Tasks

1. Install Apache, PHP and MySQL. Create a database shop with a table item holding two rows, and a user shopapp (at localhost) who can only read it. mysql -u shopapp -p shop -e 'SELECT * FROM item;' shows the two rows, and mysql -u shopapp -p shop -e 'DELETE FROM item;' fails with "DELETE command denied".
2. Serve a PHP page that lists the items, as a virtual host named shop.example.test with its own error log. curl -H 'Host: shop.example.test' http://localhost/ prints the two items; apache2ctl -S lists shop.example.test; curl http://localhost/ still shows Ubuntu's default page.
3. Break the page by changing the database password in it, so that curl -s -o /dev/null -w '%{http_code}' -H 'Host: shop.example.test' http://localhost/ prints 500, and find the cause from the logs alone: the site's error log shows "Access denied for user 'shopapp'@'localhost'". Then put it back.

Hints

• apt install apache2 mysql-server php libapache2-mod-php php-mysql; sudo mysql, CREATE DATABASE, CREATE TABLE, INSERT, CREATE USER ... IDENTIFIED BY, GRANT SELECT ON shop.* TO.
• A file in /etc/apache2/sites-available/ with <VirtualHost *:80>, ServerName, DocumentRoot, DirectoryIndex index.php, ErrorLog ${APACHE_LOG_DIR}/...; a2ensite, apache2ctl configtest, systemctl reload apache2. In PHP, new mysqli(...), query(), fetch_assoc().
• tail the site's error log in /var/log/apache2/.