Mysqldump-secure was built with many security aspects in mind which are explained below.
Database password stealing
When you run
--password option from command line or automated via cron, it is possible for other users to see the specified password in cleartext inside the system's process list via
One mechanism to prevent this is to enable
hidepid on the mounted
/proc device which will then hide your processes to all other users.
hidepid=1 means users may not access any /proc// directories, but their own. Sensitive files like cmdline, sched*, status are now protected against other users. As permission checking done in proc_pid_permission() and files' permissions are left untouched, programs expecting specific files' modes are not confused.
This however might not be possible on shared hostings.
The second more clever solution lies within the usage of mysql config files. Credentials specified in
my.cnf (mysqldump section) are automatically used when running mysqldump without showing them in
ps auxw or
Mysqldump-secure installs its own .cnf file where you can set the credentials for your mysqldump session.
In the best case you would create a user who only has read permissions on all databases you want to dump (including the mysql database).
Mysqldump-secure's default permission values for files and folders are very strict and will only allow access (read/write) to the user starting the process (and obviously root, if it was not run by root).
Furthermore it will complain and in some cases abort if a file permission was not strict enough. For example if the password file was world readable, it will stop execution and inform you that the passwords could have been leaked.
For all other sensitive permissions, mysqldump-secure will auto-set them accordingly to the ones specified in
Umask and chmod
If you have not set any special
umask settings on the system,
mysqldump (and any other program) will normally write the databases to disk with chmod
0644 permissions. If the parent folder is not protected, the dumps will be readable by anybody.
You could do a
chmod 0600 afterwards, but doing it afterwards is already too late, so
mysqldump-secure is temporarily setting the
umask prior writing the file to disk, so that it is possible to dump with
This can be accomplished in such a way:
umask 377; mysqldump
This however is your responsibility, if you should change the following two variables from
Always make sure to protect the parent directory (where the dumps are going to be) as well as the dumps itself.
Another layer of security is to also encrypt the database on the fly while dumping (before writing to disk). This is accomplished via hybrid encryption. It is using aes and private/public key encryption.
You will need to create a private/public keypair and only copy your public key to the server. Mysqldump-secure will make use of the public key to encrypt your dumps against (similar to pgp encryption).
Dump can only be decrypted with the private key, which should be somewhere safe and ideally not on the same server.
When you want to check a program for a sucessful run, you should always check that the exit code was
0. If it was non-zero there has been some sort of error. However when you deal with piped commands and simply use
$? to check for an exit code, it will always only give the exit code of the last piped command.
Let's take an example:
$ fales $ echo $? 1
However, once you add another command to the pipe, it would seem as everything went fine even though the first command failed:
$ fales | true $ echo $? 0
So how do you do that in pure POSIX bourne shell? This one is kind of tricky:
$ exec 4>&1 $ error_statuses="$( ( \ (false || echo "0:$?" >&3) | \ (true || echo "1:$?" >&3) \ ) 3>&1 >&4)" $ exec 4>&- $ echo $error_statuses 0:1
$error_statuses will be filled, once there is an error.
Let's have a look what value it will have, when there is no error at all:
$ exec 4>&1 $ error_statuses="$( ( \ (true || echo "0:$?" >&3) | \ (true || echo "1:$?" >&3) \ ) 3>&1 >&4)" $ exec 4>&- $ echo $error_statuses
So the variable is empty (or not set) when everything went fine and we can finally check it like this:
if [ -z "$error_statuses" ]; then echo "No error" else echo "Error occured" fi
So this is the method mysqldump-secure checks for errors in piped commands.