nextcloud/lib/private/setup/mysql.php

<?php

namespace OC\Setup;

class MySQL extends AbstractDatabase {
	public $dbprettyname = 'MySQL/MariaDB';

	public function setupDatabase($username) {
		//check if the database user has admin right
		$connection = @mysql_connect($this->dbhost, $this->dbuser, $this->dbpassword);
		if(!$connection) {
			throw new \OC\DatabaseSetupException($this->trans->t('MySQL/MariaDB username and/or password not valid'),
				$this->trans->t('You need to enter either an existing account or the administrator.'));
		}
		//user already specified in config
		$oldUser=\OC_Config::getValue('dbuser', false);

		//we don't have a dbuser specified in config
		if($this->dbuser!=$oldUser) {
			//add prefix to the admin username to prevent collisions
			$adminUser=substr('oc_'.$username, 0, 16);

			$i = 1;
			while(true) {
				//this should be enough to check for admin rights in mysql
				$query="SELECT user FROM mysql.user WHERE user='$adminUser'";

				$result = mysql_query($query, $connection);

				//current dbuser has admin rights
				if($result) {
					//new dbuser does not exist
					if(mysql_num_rows($result) === 0) {
						//use the admin login data for the new database user
						$this->dbuser=$adminUser;

						//create a random password so we don't need to store the admin password in the config file
						$this->dbpassword=\OC_Util::generateRandomBytes(30);

						$this->createDBUser($connection);

						break;
					} else {
						//repeat with different username
						$length=strlen((string)$i);
						$adminUser=substr('oc_'.$username, 0, 16 - $length).$i;
						$i++;
					}
				} else {
					break;
				}
			};

			\OC_Config::setValues([
				'dbuser'		=> $this->dbuser,
				'dbpassword'	=> $this->dbpassword,
			]);
		}

		//create the database
		$this->createDatabase($connection);

		//fill the database if needed
		$query='select count(*) from information_schema.tables'
			." where table_schema='".$this->dbname."' AND table_name = '".$this->tableprefix."users';";
		$result = mysql_query($query, $connection);
		if($result) {
			$row=mysql_fetch_row($result);
		}
		if(!$result or $row[0]==0) {
			\OC_DB::createDbFromStructure($this->dbDefinitionFile);
		}
		mysql_close($connection);
	}

	private function createDatabase($connection) {
		$name = $this->dbname;
		$user = $this->dbuser;
		//we cant use OC_BD functions here because we need to connect as the administrative user.
		$query = "CREATE DATABASE IF NOT EXISTS `$name` CHARACTER SET utf8 COLLATE utf8_bin;";
		$result = mysql_query($query, $connection);
		if(!$result) {
			$entry = $this->trans->t('DB Error: "%s"', array(mysql_error($connection))) . '<br />';
			$entry .= $this->trans->t('Offending command was: "%s"', array($query)) . '<br />';
			\OC_Log::write('setup.mssql', $entry, \OC_Log::WARN);
		}
		$query="GRANT ALL PRIVILEGES ON `$name` . * TO '$user'";

		//this query will fail if there aren't the right permissions, ignore the error
		mysql_query($query, $connection);
	}

	private function createDBUser($connection) {
		$name = $this->dbuser;
		$password = $this->dbpassword;
		// we need to create 2 accounts, one for global use and one for local user. if we don't specify the local one,
		// the anonymous user would take precedence when there is one.
		$query = "CREATE USER '$name'@'localhost' IDENTIFIED BY '$password'";
		$result = mysql_query($query, $connection);
		if (!$result) {
			throw new \OC\DatabaseSetupException($this->trans->t("MySQL/MariaDB user '%s'@'localhost' exists already.", array($name)),
				$this->trans->t("Drop this user from MySQL/MariaDB", array($name)));
		}
		$query = "CREATE USER '$name'@'%' IDENTIFIED BY '$password'";
		$result = mysql_query($query, $connection);
		if (!$result) {
			throw new \OC\DatabaseSetupException($this->trans->t("MySQL/MariaDB user '%s'@'%%' already exists", array($name)),
				$this->trans->t("Drop this user from MySQL/MariaDB."));
		}
	}
}