2014 database - course 3 - PHP and MySQL

PHP - MySQL

Ensky / 林宏昱

Load data from database

GET /enskylin HTTP/1.1 Host: www.facebook.com

HTTP/1.1 200 OK

HTML

generate HTML

GET /enskylin HTTP/1.1 Host: www.facebook.com

HTTP/1.1 200 OK

HTML

How to access database?

• today's topic :D

Establish a connection (you should set it up during your installation)

(If you use cscc account, then follow the instruction on cscc MySQL website)

username: root password: nctu5566

login successfully

Do some Queries Insert: Create Select: Read

Update: Update Delete: Delete

INSERT INTO users (id, pw) VALUES ('jlhuang', 'iLove5566')

Query OK, 1 rows affected

Dealing with Results

Generate the correspond HTML

SELECT * FROM users

100 row in set (0.00 sec)

That's all.

Hello world! - connect Establish a connection: $db_host = "host_name"; $db_name = "database_name"; $db_user = "user_name"; $db_password = "password"; $dsn = "mysql:host=$db_host;dbname=$db_name"; $db = new PDO($dsn, $db_user, $db_password);

Hello world! - Insert SQL -- INSERT INTO `users` (id, username, gender) VALUES(1, 'Ensky', 'male') PHP -- $sql = "INSERT INTO `users` (id, username, gender)" . " VALUES(?, ?, ?)"; $sth = $db->prepare($sql); $sth->execute(array(1, 'ensky', 'male')); id username gender

1 Ensky male

Hello world! - Select $sql = "SELECT * FROM `users`" . " WHERE `username` = ? AND `password` = ?"; $sth = $db->prepare($sql); $sth->execute(array('ensky', 'nctu5566'));

id username password gender

1 Ensky nctu5566 male

2 Emily sdfasdf female

Hello world! - Retrieve $sql = "SELECT username, gender FROM `users`" . " WHERE `username` = ? AND `password` = ?"; $sth = $db->prepare($sql); $sth->execute(array('ensky', 'nctu5566')); while ($result = $sth->fetchObject()) { echo $result->name . $result->gender; } // Ensky male // Emily female // …

id username password gender

1 Ensky nctu5566 male

2 Emily sdfasdf female

Named parameters $sql = "SELECT username, gender FROM `users`" . " WHERE `username` = ? AND `password` = ?"; $sth = $db->prepare($sql); $sth->execute(array('ensky', 'nctu5566')); is equal to $sql = "SELECT username, gender FROM `users`" . " WHERE `username` = :un AND `password` = :pw"; $sth = $db->prepare($sql); $sth->execute(array( ':un' => 'ensky', ':pw' => 'nctu5566'));

PHP Data Objects • PDO is an OO style class • Classes

– PDO • PDO __construct ( string $dsn, [, string $username [, string

$password ]]) • PDOStatement prepare( string $statement ) • PDOStatement query( string $statement )

– PDOStatement • bool execute ([ array $input_parameters ] ) • mixed fetchObject ([ string $class_name = "stdClass" [, array

$ctor_args ]] )

Don't use mysql_* • There are many libraries to help you connect to

MySQL database – MySQL – MySQLi – PDO

• If your books recommends you to use mysql_xxx functions, throws it.

Don't use mysql_* • What's the problem of mysql_ functions?

– It is deprecated in PHP 5.5.0, and will be removed in PHP6 – SQL Injection problem

• no prepared statement – Only support MySQL(PDO supports 12 different databases)

What's SQL injection?

Simple query(use mysql ext) login_action.php -- <?php mysql_connect($db_host, $db_user, $db_password); mysql_select_db($dn_name); $result = mysql_query( "SELECT * FROM `users`" ." WHERE `email` = '{$_POST['email']}'" ." AND `password = '{$_POST['password']}'" ); // …

Simple query(use mysql ext) login_form.php login_action.php -- $result = mysql_query( "SELECT * FROM `users`" ." WHERE `email` = '{$_POST['email']}'" ." AND `password = '{$_POST['password']}'" );

Simple query(use mysql ext) login_form.php login_action.php -- $result = mysql_query( "SELECT * FROM `users`" ." WHERE `email` = '[email protected]'" ." AND `password = 'nctu5566'" );

Simple query(use mysql ext) $result = mysql_query( "SELECT * FROM `users`" ." WHERE `email` = '[email protected]'" ." AND `password = 'nctu5566'" ); SELECT * FROM `users` WHERE `email` = '[email protected]' AND `password` = 'nctu5566'

SQL injection "--" in SQL represents "comments" SELECT * FROM `users` -- I want to select all from user SELECT * FROM `users` -- today is a good day

SQL injection If a cracker knows your query logic: SELECT * FROM `users` WHERE `email` = 'user_account' AND `password = 'user_password' give a try: user_account = ' OR 1=1 -- SELECT * FROM `users` WHERE `email` = '' OR 1=1 --' AND `password = 'user_password'

OOPS!

SQL injection SELECT * FROM `users` WHERE `email` = '' OR 1=1 --' AND `password = 'user_password' Since 1=1 is obviously true in any circumstances, and below messages are commented out, this instruction will select all users instead of logged in user.

Prepared statement • By prepare query statement before execute,

we can prevent SQL injection PREPARE SELECT * FROM `user` WHERE `id`=? AND `password`=?

OK, prepared

EXECUTE "enskylin", "nctu5566"

1 row in set (0.00 sec)

Password Hashing • Let's look at User creation INSERT INTO (id, password) VALUES ('ensky', 'nctu5566') • Actually, it is very dangerous! • Note that Database server is able to be cracked

If hackers can get your "real password", than it is a big problem

• Even more, if database administrator can access your real password, than it should be a problem, too.

more plaintext passwords: https://www.facebook.com/PlainPass

How to solve the plaintext password problem?

Password Hashing

Hashing!

a many-to-one no inverse function http://www.php.net/manual/en/function.hash.php#104987

Password Hashed PW

hello 5d41402abc4 …

world 7d793037a07 …

Flow • register

• login

• Reset

hello 5d41402abc4 … 5d41402abc4 … generate hashed password save to database

hello 5d41402abc4 … 5d41402abc4 … generate hashed password verify with database's hash

world 7d793037a07 … 7d793037a07 …

generate new hashed password save to database

Crack • One common crack method is "rainbow table"

– detail algorithm: wiki

• password hashing can be cracked by using

predefined hash tables

• However it can be prevented by using "random salt" for each password

Best practice • Best practice to deal with hashing is to hash with

"random salt" • Save

1. generate a random salt 2. hashing password use this random salt 3. save "hashed password" with random salt to database

• Verify 1. query hashed password with random salt by user 2. regenerate hashed password and verify with real data

PHP support • PHP 5.5 supports password_hash, password_verify

functions to deal with password hashing problem http://www.php.net/manual/en/function.password-hash.php

• However, CSCC only provides PHP 5.3 so you should use crypt function instead http://www.php.net/manual/en/function.crypt.php

• Since crypt is not easy enough to use, TA provided TA's version: http://pastebin.com/aDdWvhXm

Usage // create a hash $hash = password_hash($_POST['password']); // verify a hash if (password_verify($_POST['password'], $hash)) { echo 'Password is valid!'; } else { echo 'Invalid password.'; }

References • PDO: http://tw2.php.net/manual/en/class.pdo.php • crypt: http://tw2.php.net/manual/en/function.crypt.php • plainpassword: https://www.facebook.com/PlainPass • pdo-mysql-mysqli:

http://blog.roga.tw/2010/06/%E6%B7%BA%E8%AB%87-php-mysql-php-mysqli-pdo-%E7%9A%84%E5%B7%AE%E7%95%B0/