Rule of secure coding: 'See input as evil'
- By Jack Vaughan
We recently asked security maven Steve Orrin to tell us some of the tenets of
secure coding today. While this was once an administrator's main look-see, it
has become part of the developer's job in the wake of some high-profile
Above all, said Orrin, developers should be wary of any program portions that
invite input from users. ''The number one thing for developers to realize is that
you need to treat input as evil,'' he said.
Orrin, who serves as CTO at security expert Sanctum Inc., said that besides
input dialogs, developers should be especially careful when they implement
authentication and authorization functions. User input is a ''trust problem.'' If
input isn't validated or sanitized, it is trouble waiting to happen, he
Specifically, insertion of dangerous keyboard characters leads to attacks
Culprits employ cross-site scripting to reflect-back user data from an unwary
site to the user's browser where authentication cookie data, for example, can be
captured and then sent to the computer culprit's cove. Such tricks could be part
of a growing problem known as ''identity theft.''
''It has become a problem because, too often, there is no validation or
sanitation of the input,'' said Orrin.
As Microsoft has avowed a new emphasis on secure software, we
asked Orrin how the software giant was doing on that front.
''We've seen a significant commitment to improving security by Microsoft, and
this has been evidenced in Visual Studio .NET,'' he said. ''Sanctum's security
experts have done quite a bit of testing on Visual Studio .NET and have been
impressed by several key security enhancements.
''First,'' he said, ''[Microsoft has] made it rather easy to implement signing
and encrypting the ViewState. Secondly, with Visual Studio .NET 1.1, Microsoft
added a generic validator to help catch many of the Cross Site Scripting (XSS)
variants. Finally, one can use the Regular Expression and Range Validators to
perform User Input Validation and Sanitation to prevent attacks like XSS, SQL
Injection and Buffer Overflow.''
On the Java side, application-level security is still in need of some work,
though Orrin noted that Java environments by default have protections against
Orrin noted positive moves in that the Eclipse plug-in bus can more easily
support add-ons that handle authentication and authorization.
''But as with much of the Java and open-source world, features such as
validation and sanitization are left to the user to 'do-it yourself,''' he
Sanctum Inc.'s AppScan Developer Edition (DE) 1.5 for
Writing Secure Code Second Edition by Michael Howard and David LeBlanc on
the Microsoft Press Web site: http://www.microsoft.com/mspress/books/5957.asp
Information on encrypting the form ViewState can be found on the ASP101.com
Web site at http://www.asp101.com/lessons/viewstate.asp
Information on encrypting the form ViewState can be found on the MSDN.com Web
site at http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnaspnet/html/asp11222001.asp
For other Programmers Report articles, please go to http://www.adtmag.com/article.asp?id=6265
Jack Vaughan is former Editor-at-Large at Application Development Trends magazine.