Improving Web Application Security: Threats and - CGISecurity

lxviImproving Web Application Security: Threats and CountermeasuresDevelopment SolutionsFor developers, this guide provides the following solutions:● What is .NET Framework security?The .NET Framework provides user and code security models that allow you torestrict what users can do and what code can do. To program role-based securityand code access security, use types from the System.Security namespace. The.NET Framework also provides the System.Security.Cryptography namespace,which exposes symmetric and asymmetric encryption and decryption, hashing,random number generation, support for digital signatures, and more.To understand the .NET Framework security landscape, see Chapter 6, “.NETSecurity Overview.”● How to write secure managed codeUse strong names to digitally sign your assemblies and to make themtamperproof. At the same time you need to be aware of strong name issues whenyou use strong name assemblies with ASP.NET. Reduce your assembly attackprofile by adhering to solid object oriented design principles, and then use codeaccess security to further restrict which code can call your code. Use structuredexception handling to prevent sensitive information from propagating beyondyour current trust boundary and to develop more robust code. Avoidcanonicalization issues, particularly with input file names and URLs.For information about how to improve the security of your managed code, seeChapter 7, “Building Secure Assemblies.” For more information about how touse code access security effectively to further improve security, see Chapter 8,“Code Access Security in Practice.” For information about performing managedcode reviews, see Chapter 21, “Code Review.”● How to handle exceptions securelyDo not reveal internal system or application details, such as stack traces,SQL statement fragments, and so on. Ensure that this type of information is notallowed to propagate to the end user or beyond your current trust boundary.Fail securely in the event of an exception, and make sure your application deniesaccess and is not left in an insecure state. Do not log sensitive or private data suchas passwords, which could be compromised. When you log or report exceptions,if user input is included in exception messages, validate it or sanitize it. Forexample, if you return an HTML error message, you should encode the outputto avoid script injection.For more information, see the “Exception Management” sections in Chapter 7,“Building Secure Assemblies,” and in Chapter 10, “Building Secure ASP.NETPages and Controls.”