Improve composer installer

- Check to signature.
- Add error handling.
- See Also https://getcomposer.org/doc/faqs/how-to-install-composer-programmatically.md

src/linux.sh

@@ -13,13 +13,27 @@ if [ "$version" != "$1" ]; then
 fi	
 
 if [ ! -e "/usr/bin/composer" ]; then
-	sudo curl -s https://getcomposer.org/installer | php;
+	EXPECTED_SIGNATURE="$(curl -s https://composer.github.io/installer.sig)"
-	sudo mv composer.phar /usr/local/bin/composer;
+	curl -s -L https://getcomposer.org/installer > composer-setup.php
+	ACTUAL_SIGNATURE="$(php -r "echo hash_file('sha384', 'composer-setup.php');")"
+
+	if [ "$EXPECTED_SIGNATURE" != "$ACTUAL_SIGNATURE" ]; then
+		>&2 echo 'ERROR: Invalid installer signature'
+		rm composer-setup.php
+		exit 1
+	fi
+
+	COMPOSER_ALLOW_SUPERUSER=1
+	sudo php composer-setup.php --install-dir=/usr/local/bin --filename=composer
+	RESULT=$?
+	rm composer-setup.php
+	exit $RESULT
 fi
+
 composer global require hirak/prestissimo > /dev/null 2>&1
 ini_file=$(php --ini | grep "Loaded Configuration" | sed -e "s|.*:s*||" | sed "s/ //g")
 ext_dir=$(/usr/bin/php -i | grep "extension_dir => /usr" | sed -e "s|.*=> s*||")
 sudo chmod 777 "$ini_file"
 sudo mkdir -p /run/php
 php -v
-composer -V
+composer -V