Improving Web Application Security: Threats and - CGISecurity

288 Part III: Building Secure Web ApplicationsSensitive DataSensitive data includes application configuration details (for example, connectionstrings and service account credentials) and application-specific data (for example,customer credit card numbers). The following recommendations help to reduce riskwhen you handle sensitive data:● Do not pass sensitive data from page to page.●●●Avoid plain text passwords in configuration files.Use DPAPI to avoid key management.Do not cache sensitive data.Do not Pass Sensitive Data from Page to PageAvoid using any of the client-side state management options, such as view state,cookies, query strings, or hidden form-field variables, to store sensitive data. The datacan be tampered with and viewed in clear text. Use server-side state managementoptions, such as a SQL Server database for secure data exchange.Avoid Plaintext Passwords in Configuration FilesThe , , and elements in Machine.configand Web.config have userName and password attributes. Do not store these inplaintext. Store encrypted credentials in the registry using the Aspnet_setreg.exe tool.For more information about encrypting credentials in configuration files and aboutAspnet_setreg.exe, see Chapter 19, “Securing Your ASP.NET Application and WebServices.”Use DPAPI to Avoid Key ManagementDPAPI is ideally suited for encrypting secrets such as connection strings and serviceaccount credentials. If your pages need to use this type of configuration data, useDPAPI to avoid the key management problem.For more information see “Cryptography” in Chapter 7, “Building SecureAssemblies.”Do Not Cache Sensitive DataIf your page contains data that is sensitive, such as a password, credit card number,or account status, the page should not be cached. Output caching is off by default.