Bug 16690: Simplify SHOW GRANTS to work when connected

Bug 16690: Simplify SHOW GRANTS to work when connected

If the DB is on a remote machine, the web server and the
db server are different, but the SHOW GRANTS code in
installer/install.pl is trying to use the SAME machine.
And even if the permissions were allowed accessing from
both the web and db servers, MySQL won't return the
SHOW GRANTS without access to the mysql.user table. To
install *.* permissions became easiest to get working.
Unless the DB is set up with 'user'@'%', which is also a
potential security issue.

MySQL / MariaDB allow the current connected user to
check their own grants with CURRENT_USER.
There is no need for the installer to know the
IP address of the webserver.

This also removes the need to have permissions for
'koha_kohadev'@'%', because the only process to be
accessing the koha DB is from a known host/ip.
This tightens security too.

TEST PLAN
---------
Install 2 fresh VMs from a Debian ISO.
Make sure they are on the same network (192.168.50.x) as
the kohadevbox. You will need to remember one as DB_IPADDRESS.

On the DB VM & Third VM:
sudo apt-get install mariadb-server mariadb-client net-tools
-- the third vm just needs to be able to run mysql to access
   the DB VM.

On DB VM:
sudo vi /etc/mysql/mariadb.conf.d/50-server.cnf
-- make sure the bind-address line is commented out with a #
sudo service mariadb restart
-- congratulations, your DB server is listening to remote
   calls now.

sudo mysql -u root
CREATE DATABASE koha_kohadev;
GRANT ALL PRIVILEGES ON `koha_kohadev`.* TO 'koha_kohadev'@'localhost' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;
-- now you have an empty DB ready to run a web install on.
   However, because only koha_kohadev from localhost is
   allowed, we expect failure when we try to run the web
   installation step when we get there.

Let's confirm that everything is working as expected
before trying.  It will also demonstrate the reason why
this patch is superior to the existing code.

On a kohadevbox:
mysql -u koha_kohadev -h DB_IPADDRESS -p
-- this should be denied

On DB VM:
DROP USER 'koha_kohadev'@'localhost';
GRANT ALL PRIVILEGES ON `koha_kohadev`.* TO 'koha_kohadev'@'%' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;

On a kohadevbox:
mysql -u koha_kohadev -h DB_IPADDRESS -p
-- this should give you a SQL prompt
SHOW GRANTS FOR CURRENT_USER;
-- this should show two lines based on 'koha_kohadev'@'%';
SHOW GRANTS FOR 'koha_kohadev'@'192.168.50.10';
-- this should give an access denied error.
SHOW GRANTS FOR 'koha_kohadev'@'%';
-- this should show two lines based on 'koha_kohadev'@'%';
QUIT
-- This case requires the unless code currently in place,
   because we aren't checking CURRENT_USER.

On DB VM:
DROP USER 'koha_kohadev'@'%';
GRANT ALL PRIVILEGES ON `koha_kohadev`.* TO 'koha_kohadev'@'192.168.50.10' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;

On a kohadevbox:
mysql -u koha_kohadev -h DB_IPADDRESS -p
-- this should give you a SQL prompt
SHOW GRANTS FOR CURRENT_USER;
-- this should show two lines based on 'koha_kohadev'@'%';
SHOW GRANTS FOR 'koha_kohadev'@'192.168.50.10';
-- this should show two lines based on 'koha_kohadev'@'192.168.50.10';
SHOW GRANTS FOR 'koha_kohadev'@'%';
-- this should give an access denied error.
QUIT
-- This case demonstrates that we have two failure points:
       1) The GRANT command by the DB Admin and
       2) The koha-conf.xml setting.
   This is why CURRENT_USER is superior: only (2) is the
   failure point.

On DB VM:
GRANT ALL PRIVILEGES ON `koha_kohadev`.* TO 'koha_kohadev'@'%' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;
SELECT host,user FROM mysql.user;
-- Should see both koha_kohadev for 192.168.50.10 and %.

On a kohadevbox:
mysql -u koha_kohadev -h DB_IPADDRESS -p
-- this should give you a SQL prompt
SHOW GRANTS FOR CURRENT_USER;
-- this should show two lines based on 'koha_kohadev'@'192.168.50.10';
SHOW GRANTS FOR 'koha_kohadev'@'192.168.50.10';
-- this should show two lines based on 'koha_kohadev'@'192.168.50.10';
SHOW GRANTS FOR 'koha_kohadev'@'%';
-- this should give an access denied error.
QUIT
-- This case doesn't need the unless. CURRENT_USER still
   just works.

On an third VM on the same network:
mysql -u koha_kohadev -h DB_IPADDRESS -p
-- this should give you a SQL prompt
SHOW GRANTS FOR CURRENT_USER;
-- this should show two lines based on 'koha_kohadev'@'%';
SHOW GRANTS FOR 'koha_kohadev'@'192.168.50.10';
-- this should give an access denied error.
SHOW GRANTS FOR 'koha_kohadev'@'%';
-- this should show two lines based on 'koha_kohadev'@'%';
QUIT
-- This case demonstrates that it may be more open than a DB
   administrator would prefer. And notice, CURRENT_USER still
   just works.

On DB VM:
DROP USER 'koha_kohadev'@'192.168.50.10';
DROP USER 'koha_kohadev'@'%';
GRANT ALL PRIVILEGES ON *.* TO 'koha_kohadev'@'%' IDENTIFIED BY 'password';
FLUSH PRIVILEGES;
-- This basically give koha_kohadev free reign to do pretty
   dangerous stuff.

On an third VM on the same network:
mysql -u koha_kohadev -h DB_IPADDRESS -p
-- this should give you a SQL prompt
SHOW GRANTS FOR CURRENT_USER;
-- this should show a line based on 'koha_kohadev'@'%';
SHOW GRANTS FOR 'koha_kohadev'@'192.168.50.10';
-- this should give a no such grant error.
SHOW GRANTS FOR 'koha_kohadev'@'%';
-- this should show two lines based on 'koha_kohadev'@'%';
QUIT
-- This case demonstrates that it may be more open than a DB
   administrator would prefer. And notice, CURRENT_USER still
   just works.

In the old code, both cases were literally checked.
This tweak is an optimization which doesn't require
setting permissions to the mysql.user table. Without it,
the code says the user doesn't have permissions to check
the show grants.  This issue is not visible to the user,
because both cases are checked.

On DB VM:
SELECT host,user FROM mysql.user;
-- for each one do an appropriate DROP USER 'user'@'host';
GRANT ALL PRIVILEGES ON `koha_kohadev`.* TO 'koha_kohadev'@'192.168.50.10' IDENTIFIED BY 'password';

On kohadevbox:
-- Make sure the /etc/koha/sites/kohadev/koha-conf.xml
   points to the DB VM.
-- Make sure a web install runs correctly

On third VM:
-- Make sure unable to connect as koha_kohadev/password.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
I have not followed the whole test plan but trusting author and SO
Changes make sense to me

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>