<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>Encrypted Storage Model</title>
</head>
<body><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="security.database.connection.html">Connecting to Database</a></div>
<div class="next" style="text-align: right; float: right;"><a href="security.database.sql-injection.html">SQL Injection</a></div>
<div class="up"><a href="security.database.html">Database Security</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div><hr /><div id="security.database.storage" class="sect1">
<h2 class="title">Encrypted Storage Model</h2>
<p class="simpara">
SSL/SSH protects data travelling from the client to the server: SSL/SSH
does not protect persistent data stored in a database. SSL is an
on-the-wire protocol.
</p>
<p class="simpara">
Once an attacker gains access to your database directly (bypassing the
webserver), 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.
</p>
<p class="simpara">
The easiest way to work around this problem is to first create your own
encryption package, and then use it from within your <acronym title="PHP: Hypertext Preprocessor">PHP</acronym> scripts. <acronym title="PHP: Hypertext Preprocessor">PHP</acronym>
can assist you in this with several extensions, such as <a href="ref.mcrypt.html" class="link">Mcrypt</a> and <a href="ref.mhash.html" class="link">Mhash</a>, 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.
</p>
<div class="sect2" id="security.database.storage.hashing">
<h3 class="title">Hashing</h3>
<p class="simpara">
In the case of truly hidden data, if its raw representation is not needed
(i.e. will not be displayed), hashing should be taken into consideration.
The well-known example for hashing is storing the cryptographic hash of a
password in a database, instead of the password itself.
</p>
<p class="simpara">
In PHP 5.5 or newer <a href="ref.password.html" class="link">password</a> functions
provide a convenient way to hash sensitive data and work with these hashes.
In PHP 5.3.7+ <a href="https://github.com/ircmaxell/password_compat" class="link external">»
password_compat</a> library can also be used.
</p>
<p class="simpara">
<span class="function"><a href="function.password-hash.html" class="function">password_hash()</a></span> is used to hash a given string using the
strongest algorithm currently available and <span class="function"><a href="function.password-verify.html" class="function">password_verify()</a></span>
checks whether the given password matches the hash stored in database.
</p>
<div class="example" id="example-359">
<p><strong>Example #1 Hashing password field</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #FF8000">// storing password hash<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #DD0000">"INSERT INTO users(name,pwd) VALUES('%s','%s');"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">),<br /> </span><span style="color: #0000BB">password_hash</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #0000BB">PASSWORD_DEFAULT</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$result </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$connection</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// querying if user submitted the right password<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT pwd FROM users WHERE name='%s';"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$row </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_fetch_assoc</span><span style="color: #007700">(</span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$connection</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">));<br /><br />if (</span><span style="color: #0000BB">$row </span><span style="color: #007700">&& </span><span style="color: #0000BB">password_verify</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'pwd'</span><span style="color: #007700">])) {<br /> echo </span><span style="color: #DD0000">'Welcome, ' </span><span style="color: #007700">. </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">) . </span><span style="color: #DD0000">'!'</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">'Authentication failed for ' </span><span style="color: #007700">. </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">) . </span><span style="color: #DD0000">'.'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
<p class="simpara">
In older versions of PHP this can be achieved using <span class="function"><a href="function.crypt.html" class="function">crypt()</a></span>
function.
</p>
<div class="example" id="example-360">
<p><strong>Example #2 Hashing password using <span class="function"><a href="function.crypt.html" class="function">crypt()</a></span>s</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br /></span><span style="color: #FF8000">// storing password hash<br />// $random_chars retrieved e.g. using /dev/random<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #DD0000">"INSERT INTO users(name,pwd) VALUES('%s','%s');"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">),<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">crypt</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #DD0000">'$2a$07$' </span><span style="color: #007700">. </span><span style="color: #0000BB">$random_chars </span><span style="color: #007700">. </span><span style="color: #DD0000">'$'</span><span style="color: #007700">)));<br /></span><span style="color: #0000BB">$result </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$connection</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// querying if user submitted the right password<br /></span><span style="color: #0000BB">$query </span><span style="color: #007700">= </span><span style="color: #0000BB">sprintf</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT pwd FROM users WHERE name='%s';"</span><span style="color: #007700">,<br /> </span><span style="color: #0000BB">pg_escape_string</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">$row </span><span style="color: #007700">= </span><span style="color: #0000BB">pg_fetch_assoc</span><span style="color: #007700">(</span><span style="color: #0000BB">pg_query</span><span style="color: #007700">(</span><span style="color: #0000BB">$connection</span><span style="color: #007700">, </span><span style="color: #0000BB">$query</span><span style="color: #007700">));<br /><br />if (</span><span style="color: #0000BB">$row </span><span style="color: #007700">&& </span><span style="color: #0000BB">crypt</span><span style="color: #007700">(</span><span style="color: #0000BB">$password</span><span style="color: #007700">, </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'pwd'</span><span style="color: #007700">]) == </span><span style="color: #0000BB">$row</span><span style="color: #007700">[</span><span style="color: #DD0000">'pwd'</span><span style="color: #007700">]) {<br /> echo </span><span style="color: #DD0000">'Welcome, ' </span><span style="color: #007700">. </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">) . </span><span style="color: #DD0000">'!'</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">'Authentication failed for ' </span><span style="color: #007700">. </span><span style="color: #0000BB">htmlspecialchars</span><span style="color: #007700">(</span><span style="color: #0000BB">$username</span><span style="color: #007700">) . </span><span style="color: #DD0000">'.'</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</div>
</div><hr /><div class="manualnavbar" style="text-align: center;">
<div class="prev" style="text-align: left; float: left;"><a href="security.database.connection.html">Connecting to Database</a></div>
<div class="next" style="text-align: right; float: right;"><a href="security.database.sql-injection.html">SQL Injection</a></div>
<div class="up"><a href="security.database.html">Database Security</a></div>
<div class="home"><a href="index.html">PHP Manual</a></div>
</div></body></html>
