2014 database - course 3 - PHP and MySQL

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)

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->execute(array('ensky', 'nctu5566'));
id username password gender
1 Ensky nctu5566 male
2 Emily sdfasdf female

Hello world! - Retrieve
$sql = "SELECT username, gender FROM `users`"
while ($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
is equal to
. " WHERE `username` = :un AND `password` = :pw";
$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)

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']}'"
);
// …

login_form.php
login_action.php
--
." WHERE `email` = '{$_POST['email']}'"
." AND `password = '{$_POST['password']}'"
);

login_form.php
login_action.php
--
." WHERE `email` = 'enskylin@gmail.com'"
." AND `password = 'nctu5566'"
);

." WHERE èmail` = 'enskylin@gmail.com'"
." AND `password = 'nctu5566'"
);
SELECT * FROM ùsers`
WHERE èmail` = 'enskylin@gmail.com'
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:
WHERE `email` = 'user_account'
AND `password = 'user_password'
give a try:
user_account = ' OR 1=1 --
WHERE `email` = '' OR 1=1 --'
OOPS!

SQL injection
WHERE `email` = '' OR 1=1 --'
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/

2014 database - course 3 - PHP and MySQL

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