Improving Web Application Security: Threats and - CGISecurity

Contents xiiiChapter 7Building Secure Assemblies 145In This Chapter ....................................................................................................... 145Overview ................................................................................................................ 145How to Use This Chapter ......................................................................................... 146Threats and Countermeasures ................................................................................. 146Unauthorized Access or Privilege Elevation, or both................................................ 147Code Injection .................................................................................................... 147Information Disclosure ........................................................................................ 148Tampering .......................................................................................................... 149Privileged Code....................................................................................................... 149Privileged Resources ........................................................................................... 150Privileged Operations .......................................................................................... 150Assembly Design Considerations ............................................................................. 150Identify Privileged Code ....................................................................................... 150Identify the Trust Level of Your Target Environment................................................. 151Sandbox Highly Privileged Code............................................................................ 152Design Your Public Interface................................................................................. 153Class Design Considerations ................................................................................... 153Restrict Class and Member Visibility..................................................................... 153Seal Non-Base Classes ....................................................................................... 153Restrict Which Users Can Call Your Code.............................................................. 154Expose Fields Using Properties ............................................................................ 154Strong Names ........................................................................................................ 155Security Benefits of Strong Names ....................................................................... 156Using Strong Names ........................................................................................... 156Delay Signing...................................................................................................... 157ASP.NET and Strong Names................................................................................. 158Authenticode vs. Strong Names ........................................................................... 159Authorization .......................................................................................................... 160Exception Management ........................................................................................... 161Use Structured Exception Handling....................................................................... 161Do Not Log Sensitive Data................................................................................... 162Do Not Reveal Sensitive System or Application Information .................................... 162Consider Exception Filter Issues .......................................................................... 162Consider an Exception Management Framework .................................................... 163File I/O .................................................................................................................. 164Avoid Untrusted Input for File Names.................................................................... 164Do Not Trust Environment Variables...................................................................... 164Validate Input File Names .................................................................................... 164Constrain File I/O Within Your Application’s Context............................................... 165Event Log ............................................................................................................... 165