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 27-1. Using hashed password field
<?php
// storing password hash
$query = sprintf("INSERT INTO users(name,pwd) VALUES('%s','%s');",
pg_escape_string($username), md5($password));
$result = pg_query($connection, $query);
// querying if user submitted the right password
$query = sprintf("SELECT 1 FROM users WHERE name='%s' AND pwd='%s';",
pg_escape_string($username), md5($password));
$result = pg_query($connection, $query);
if (pg_num_rows($result) > 0) {
echo 'Welcome, $username!';
} else {
echo 'Authentication failed for $username.';
}
?>
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