Connecting to Database
You may want to estabilish the connections over SSL to encrypt
client/server communications for increased security, or you
can use ssh to encrypt the network connection between clients
and the database server. If either of these is used, then
monitoring your traffic and gaining information about your
database will be difficult for a would-be attacker.
Encrypted Storage Model
SSL/SSH protects data travelling from the client to the
server, SSL/SSH does not protect the persistent data stored
in a database. SSL is an on-the-wire protocol.
Once an attacker gains access to your database directly
(bypassing the webserver), the stored sensitive data may
be exposed or misused, unless the information is protected
by the database itself. Encrypting the data is a good way
to mitigate this threat, but very few databases offer this
type of data encryption.
The easiest way to work around this problem is to first
create your own encryption package, and then use it from
within your PHP scripts. PHP can assist you in this with
several extensions, such as Mcrypt and Mhash, covering a
wide variety of encryption algorithms. The script encrypts
the data before inserting it into the database, and decrypts
it when retrieving. See the references for further examples
of how encryption works.
In case of truly hidden data, if its raw representation
is not needed (i.e. not be displayed), hashing may also
be taken into consideration. The well-known example for
the hashing is storing the MD5 hash of a password in a database,
instead of the password itself. See also crypt() and md5().
Example 15-5. Using hashed password field
<?php
// storing password hash
$query = sprintf("INSERT INTO users(name,pwd) VALUES('%s','%s');",
addslashes($username), md5($password));
$result = pg_exec($connection, $query);
// querying if user submitted the right password
$query = sprintf("SELECT 1 FROM users WHERE name='%s'
AND pwd='%s';",
addslashes($username), md5($password));
$result = pg_exec($connection, $query);
if (pg_numrows($result) > 0) {
echo "Welcome, $username!";
}
else {
echo "Authentication failed for $username.";
}
?>
