This article presents a reflection about why this growth happened just in the latest years, as well what it means for the PHP world.

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Most importantly, turn off register_globals. This configuration setting defaults to off in PHP 4.2.0 and later. Access values from URLs, forms, and cookies through the superglobal arrays $_GET, $_POST, and $_COOKIE.

Before you use values from the superglobal arrays, validate them to make sure they don’t contain unexpected input. If you know what type of value you are expecting, make sure what you’ve got conforms to an expected format. For example, if you’re expecting a US ZIP Code, make sure your value is either five digits or five digits, a hyphen, and four more digits (ZIP+4). Often, regular expressions are the easiest way to validate data:

if (preg_match('/^\d{5}(-\d{4})?$/',$_GET['zip'])) {
    $zip = $_GET['zip'];
} else {
    die('Invalid ZIP Code format.');
}

If you’re expecting to receive data in a cookie or a hidden form field that you’ve previously sent to a client, make sure it hasn’t been tampered with by sending a hash of the data and a secret word along with the data. Put the hash in a hidden form field (or in the cookie) along with the data. When you receive the data and the hash, re-hash the data and make sure the new hash matches the old one:

// sending the cookie
$secret_word = 'gargamel';
$id = 123745323;
$hash = md5($secret_word.$id);
setcookie('id',$id.'-'.$hash);

// receiving and verifying the cookie
list($cookie_id,$cookie_hash) = explode('-',$_COOKIE['id']);
if (md5($secret_word.$cookie_id) == $cookie_hash) {
    $id = $cookie_id;
} else {
    die('Invalid cookie.');
}

If a user has changed the ID value in the cookie, the hashes won’t match. The success of this method obviously depends on keeping $secret_word secret, so put it in a file that can’t be read by just anybody and change it periodically. (But remember, when you change it, old hashes that might be lying around in cookies will no longer be valid.)

See Also:

• PHP Manual: Using Register Globals
• PHP Cookbook: Recipe 9.7 (“Securing PHP’s Form Processing”), Recipe 14.3 (“Verifying Data with Hashes”)

2. Broken Access Control

Instead of rolling your own access control solution, use PEAR modules. Auth does cookie-based authentication for you and Auth_HTTP does browser-based authentication.

See Also:

• PEAR Packages: Auth, Auth_HTTP.

3. Broken Account and Session Management

Use PHP’s built-in session management functions for secure, standardized session management. However, be careful how your server is configured to store session information. For example, if session contents are stored as world-readable files in /tmp, then any user that logs into the server can see the contents of all the sessions. Store the sessions in a database or in a part of the file system that only trusted users can access.

To prevent network sniffers from scooping up session IDs, session-specific traffic should be sent over SSL. You don’t need to do anything special to PHP when you’re using an SSL connection, but you do need to specially configure your webserver.

See Also:

• PHP Manual: Session handling functions
• PHP Cookbook: Recipe 8.5 (“Using Session Tracking”), Recipe 8.6 (“Storing Sessions in a Database”)

4. Cross-Site Scripting (XSS) Flaws

Never display any information coming from outside your program without filtering it first. Filter variables before including them in hidden form fields, in query strings, or just plain page output.

PHP gives you plenty of tools to filter untrusted data:

• htmlspecialchars() turns & > " < into their HTML-entity equivalents and can also convert single quotes by passing ENT_QUOTES as a second argument.
• strtr() filters any characters you’d like. Pass strtr() an array of characters and their replacements. To change ( and ) into their entity equivalents, which is recommended to prevent XSS attacks, do:
  $safer = strtr($untrusted, array('(' => '(', ')' => ')'));
• strip_tags() removes HTML and PHP tags from a string.
• utf8_decode() converts the ISO-8859-1 characters in a string encoded with the Unicode UTF-8 encoding to single-byte ASCII characters. Sometimes cross-site scripting attackers attempt to hide their attacks in Unicode encoding. You can use utf8_decode() to peel off that encoding.

See Also:

• PHP Manual: htmlspecialchars(), strtr(), strip_tags(), utf8_decode()
• PHP Cookbook: Recipe 8.8 (“Building a GET Query String”), Recipe 9.8 (“Escaping Control Characters from User Data”)

5. Buffer Overflows

You can’t allocate memory at runtime in PHP and their are no pointers like in C so your PHP code, however sloppy it may be, won’t have any buffer overflows. What you do have to watch out for, however, are buffer overflows in PHP itself (and its extensions.) Subscribe to the php-announce mailing list to keep abreast of patches and new releases.

See Also:

• PHP Mailing Lists: http://www.php.net/mailing-lists.php

6. Command Injection Flaws

Cross-site scripting flaws happen when you display unfiltered, unescaped malicious content to a user’s browser. Command injection flaws happen when you pass unfiltered, unescaped malicious commands to an external process or database. To prevent command injection flaws, in addition to validating input, always escape user input before passing it to an external process or database.

If you’re passing user input to a shell (via a command like exec(), system(), or the backtick operator), first, ask yourself if you really need to. Most file operations can be performed with native PHP functions. If you absolutely, positively need to run an external program whose name or arguments come from untrusted input, escape program names with escapeshellcmd() and arguments with escapeshellarg().

Before executing an external program or opening an external file, you should also canonicalize its pathname with realpath(). This expands all symbolic links, translates . (current directory) .. (parent directory), and removes duplicate directory separators. Once a pathname is canonicalized you can test it to make sure it meets certain criteria, like being beneath the web server document root or in a user’s home directory.

If you’re passing user input to a SQL query, escape the input with addslashes() before putting it into the query. If you’re using MySQL, escape strings with mysql_real_escape_string() (or mysql_escape_string() for PHP versions before 4.3.0). If you’re using the PEAR DB database abstraction layer, you can use the DB::quote() method or use a query placeholder like ?, which automatically escapes the value that replaces the placeholder.

See Also:

• PHP Manual: escapeshellcmd(), escapeshellarg(), realpath(), addslashes(), mysql_real_escape_string(), mysql_escape_string()
• PEAR Package: DB, DB Documentation
• PHP Cookbook: Recipe 18.20 (“Escaping Shell Metacharacters”), Recipe 10.9 (“Escaping Quotes”)

7. Error Handling Problems

If users (and attackers) can see the raw error messages returned from PHP, your database, or external programs, they can make educated guesses about how your system is organized and what software you use. These educated guesses make it easier for attackers to break into your system. Error messages shouldn’t contain any descriptive system information. Tell PHP to put error messages in your server’s error log instead of displaying them to a user with these configuration directives:

log_errors = On
display_errors = Off

See Also:

• PHP Manual: Error Handling and Logging Functions
• PHP Cookbook: Recipe 8.14 (“Hiding Error Messages from Users”)

8. Insecure Use of Cryptography

The mcrypt extension provides a standardized interface to many popular cryptographic algorithms. Use mcrypt instead of rolling your own encryption scheme. Also, be careful about where (if anywhere) you store encryption keys. The strongest algorithm in the world is pointless if an attacker can easily obtain a key for decryption. If you need to store keys at all, store them apart from encrypted data. Better yet, don’t store the keys and prompt users to enter them when something needs to be decrypted. (Of course, if you’re prompting a user over the web for sensitive information like an encryption key, that prompt and the user’s reply should be passed over SSL.)

See Also:

• PHP Manual: Mcrypt Encryption Functions
• PHP Cookbook: Recipe 14.7 (“Encrypting and Decrypting Data”)

9. Remote Administration Flaws

When possible, run remote administration tools over an SSL connection to prevent sniffing of passwords and content. If you’ve installed third-party software that has a remote administration component, change the default administrative user names and passwords. Change the default administrative URL as well, if possible. Running administrative tools on a different web server than the public web server that the administrative tool administrates can be a good idea as well.

10. Web and Application Server Misconfiguration

Keep on top of PHP patches and security problems by subscribing to the php-announce mailing list. Stay away from the automatic PHP source display handler (AddType application/x-httpd-php-source .phps), since it lets attackers look at your code. Of the two sample php.ini files distributed with PHP ( php.ini-dist and php.ini-recommended), use php.ini-recommended as a base for your site configuration.

Read the Original Post at: http://www.sklar.com/page/article/owasp-top-ten

That comes in useful when it comes to changing an application after it has been deployed. Separation of the views from the data means modifications made in the views do not affect the model and modifications made to the model to not effect the graphical user interface, simplifying maintenance. Also, an application may be expanded to add views and controllers that talk to a model without actually making any changes to the model itself.

Unfortunately for web developers, one of the features lacking in PHP until recently has been support for the MVC architecture. That has meant the MVC pattern has had to be implemented externally.

Some PHP frameworks have now added support for the MVC pattern, most notably the Zend Framework – one of the leading open-source PHP frameworks. Zend simplifies the task of developing secure, reliable web-based applications and web services. Zend provides an extensible code base, a flexible architecture and does not require any configuration files.

In this article we shall connect Zend to a database from Oracle, a company that’s been working closely to optimize its software with Zend.

Fire up Zend

The Zend framework requires at least PHP 5.1.4. It’s recommended to install PHP 5.2.2 or later because of the security and performance improvements in the newer version of PHP. Download the Zend Framework zip file from here and – if you don’t already have it – download and install Apache 2.2.3, making sure it’s configured with PHP. Then, add the following include_path directive to php.ini configuration file:

include_path=".;C:\ZendFramework\ZendFramework-1.0.1\library"

Enable the PHP database extension for Oracle database in php.ini.

extension=php_oci8.dll

Restart Apache HTTP Server. Install the Oracle database including the sample schemas and create a table Catalog using SQL script catalog.sql.

Create an MVC application

Now it’s time to create a Create Read Update Delete (CRUD) application using Zend’s MVC architecture that’ll let us build, read, update, and delete an Oracle database table row.

In the MVC architecture the model represents the entities/class objects, the controller implements the business logic and integrates the model with the view, and the view represents the presentation layer or the user interface.

The MVC architecture in Zend Framework is implemented by the Zend_Controller component. The Zend_Controller_Front class provides a front controller for the MVC architecture. The front controller intercepts all requests and dispatches the requests to action controllers based on the request URL. The format of the request URL is http://localhost/controller/action. If no controller is specified the index controller and the index action are invoked. An action controller class extends the Zend_Controller_Action class. An action controller class is named with the notation <ControllerName>Controller. For example, the action controller class for the “index” controller is IndexController.

Add a row

First, we shall add a row to the Catalog table. In the insertView.php add a form with input fields for the table row to be added. The “action” attribute of the <form> element specifies “database/insert”, which corresponds to the “insert” action of the “database” controller. In the DatabaseController insertAction function create a Zend_Db adapter, which represents a connection with Oracle database, using the Zend_Db factory.

$params = array ('host'=>'localhost','username'=>'OE','password'=>'pw','dbname'=>'orcl'); $db=Zend_Db::factory('Oracle', $params);

The first argument specifies the base name for the adapter class – “Oracle” for the Oracle database. The second argument specifies the adapter parameters. Retrieve the input fields specified in the insertView.php using $_POST['field'] and create an associative array, $row, for the columns that constitute a row in the database table. Specify the database table to be updated and insert the new row using the insert() method of the Zend_Db adapter class.

$table = 'Catalog'; $rowsAffected = $db->insert($table, $row);

The first argument of the insert() method is the database table and the second argument is the associative array that maps column names to values. Invoke the insertView.php with URL http://localhost/views/insertView.php. To add a row specify the column values and click on create.

Adding a row

Retrieve a row

Next, retrieve a row from the catalog table using the Zend Framework. Create a Zend_Db_Select object from the Zend_Db adapter object using the select() method.

$select = $db->select();

The Zend_Db_Select object is used to construct a SQL SELECT statement. Specify the FROM clause using the from() method and the WHERE clause using the where() method.

$select->from('Catalog', '*'); $select->where('ID = ?', $_POST['id']);

Create the SQL query string from the Zend_Db_Select object using the _toString() method. Run the SQL query using the fetchAll() method and query results will be returned as a row set.

$sql = $select->__toString(); $rowset = $db->fetchAll($sql);

Create a Zend_View object to render a view script and specify the directory containing the view scripts. The Zend_View class represents the “view” component of the model-view-controller pattern.

$view = new Zend_View(); $view->setScriptPath('views');

$view->id = $_POST['id']; $view->journal = $rowset[0]["JOURNAL"]; $view->publisher = $rowset[0]["PUBLISHER"]; $view->edition = $rowset[0]["EDITION"]; $view->title = $rowset[0]["TITLE"]; $view->author = $rowset[0]["AUTHOR"];

Create a view script, resultView.php, associated with the Zend_View object. The view script will run in the scope of the Zend_View object. References to $this in the view script are references to the Zend_View object. Create a table header and add values to the table using the Zend_View properties assigned in the action controller. In the selectAction function render the resultView.php script.

echo $view->render('resultView.php');

Invoke the selectView.php view script with the URL http://localhost/views/selectView.php. Specify the catalog ID for the row that is to be retrieved and click select.

Selecting a database table row

The row corresponding to the specified catalog ID will be retrieved and the results displayed.

Update a Row

Next, update a catalog table row using the Zend Framework. Create an associative array, $data, of column names and values for the row to be updated. Create a SQL expression specifying the WHERE clause for the ID of the row to be updated.

$where[] = "ID ="."'".$_POST['id']."'";

Update the database table using the update() method.

$n = $db->update('Catalog', $data, $where);

Invoke the updateView.php script with URL http://localhost/views/updateView.php. Specify the catalog ID of the row to be updated and the column values to be updated and click on update.

Updating database table

A table row may be deleted using the delete() function.

MVC has a proven track record in simplifying the development and on-going maintenance of applications. Using Zend and the methodology I have outlined, you can now take advantage of MVC to simplify your work with PHP applications