They use the three stages of input validation shown in Figure 1 to reduce the risk of malicious content getting in to their app. Using HTML5, each field can easily be constrained to known good data. To illustrate examples in this article, I use the fictitious Contoso Health app, which stores personal health information for users. As the developer, I know in general what good data looks like for each of these fields:.
For the Name input element, I need to limit what characters are valid for the field as well as how long the value can be. I can do this using two new attributes of the input tag: pattern and title. Pattern is a regular expression to which the data entered must conform.
For example, the Name field can be composed of alpha characters and spaces, and it must be three to 45 characters long. The following pattern value supports this:.
Title is used to inform the user of what the system is expecting. Nothing is more frustrating to users than having invalid input without knowing what valid input is. Patterns for the data fields including acceptable characters and length can be difficult to determine. Some fields are specific data types, such as numbers, dates and e-mail addresses.
HTML5 comes to the rescue again with an army of new input types, such as email, phone, date, number and many more. You can find more types and their uses at bit. For example, to capture an e-mail address for the Profile page, I would set the type attribute to be email, as in the following example:.
This field accepts a value only if it conforms to the format of a valid e-mail address. Some of the new input types also allow range restrictions using the new min and max attributes. As an example, because of the business rules, the people in our app must have a height between 3 and 8 feet. The following range restrictions can be used on the height field:.
The examples provided use the four techniques to constrain data with the HTML5 input tag. Not all attributes and types prompt you to correct them prior to submission.
IsValid in ASP. You might be wondering whether you can constrain data like this just by using JavaScript. Reject denies known bad that is, a deny list input. Deny lists are useful when you have a somewhat fixed scope defined for what you want to block. As an example, consider sending e-mail to a group such as your development team and then specifically removing individuals from the development team e-mail list.
In this example, you know which e-mail addresses you want to deny from the development team list. For secure software, you want to focus on constrain an allow list over reject a deny list. Always remember that known bad data changes constantly as attackers find ever more creative ways to circumvent software defenses. In the preceding example, imagine new developers joining the development team and needing to vet whether they should be included in the e-mail.
Constraints are much easier to manage in the long run and provide a more maintainable list as opposed to the thousands of items in a deny list. Sometimes data contains both known good and known bad data.
An example of this is HTML content. Some tags are approved to display while others are not. The process of filtering out or disabling the known bad data and allowing the approved data is known as sanitizing the input. The notes field in the Contoso Health app is a great example of this.
Note that if the app sets the innerText of a script tag to JavaScript, executable script is produced. You can find a complete listing of approved tags, attributes, CSS rules and properties at bit. Input validation reduces the risk of malicious content entering the system. Now that Contoso Health is getting valid data, what do we do with sensitive data such as medical or financial information?
Web developer says:Never store sensitive data on the client because secure storage is unavailable. Windows 8 developer says: Sensitive data can be encrypted and securely stored through the Windows Runtime.
In the previous section, the Contoso Health app retrieved general profile information. As development continues, a medical history form is requested by the business sponsor. In Windows Store app development, sensitive data can be stored locally using the security features of the Windows Runtime. Although this document focuses on Web development best practices, it provides a lot of excellent foundation knowledge that you can apply to any type of development.
When the user clicks btnAddItem, the app encrypts data entered into the Medical History form. This simple encryption system allows developers to encrypt data quickly without the overhead of key management. Download Windows 8. If you need to install or reinstall Windows 8. Before you begin Make sure you have: An internet connection internet service provider fees may apply.
Sufficient data storage available on a computer, USB or external drive for the download. Read the System Requirements If you will be installing the operating system for the first time, you will need your Windows product key xxxxx-xxxxx-xxxxx-xxxxx-xxxxx. The WebView control is intended to allow a Store app developer to embed some part of the web inside the application, but should not be added to an application to allow browsing to any site on the Internet - it should be used to link specifically to pages hosted on your own website for the purposes of being displayed within your Store application.
In fact, the documentation is clear about the limitations of this control:. WebView always uses Internet Explorer 11 in document mode.
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