Tips & Tricks: Scrubbing Source Code For Common Coding Mistakes (FxCop And PREfast) Nicholas Guerrera TLNL06 Software Design Engineer Microsoft Corporation

2 Why Code Analysis? One of a collection of strategies for improving code quality Identify potential issues earlier in development cycle Problems are cheaper to fix the earlier they are identified

3 Code Analysis In Visual Studio Team System Managed code analysis (FxCop) C#, C++/CLI, VB.NET, ASP.NET Unmanaged code analysis (PREfast) C/C++ Automatically suppress warnings in source File bugs based on analysis results Enforce code analysis policy for check-ins

4 Types Of Mistakes Typographical Misuse of API Security issues API design guidelines / best practices Code complexity and maintainability Constructs that do not perform well

5 Demo: Managed Code Analysis In Visual Studio Team System Nicholas Guerrera Software Design Engineer Visual Studio Team System

6 Example One SQL injection vulnerability private string GetAccountNumber(string username, string password) { string cnxString = ConfigurationManager.AppSettings["ConnectionString"]; using (SqlConnection connection = new SqlConnection(cnxString)) using (SqlCommand command = new SqlCommand()) { connection.Open(); command.Connection = connection; command.CommandText = "SELECT AccountNumber FROM Users " + "WHERE (Username='" + username + "')" + "' AND (Password='" + password + "')"; return (string)command.ExecuteScalar(); } "q' OR 'q'='q"

7 public class box { public int height; public int width; public box(int height, int width) { this.height = height; this.width = width; this.print_to_console(); } public void print_to_console() { Console.WriteLine("({0},{1}", this.height, this.width); } Issues: public fields, incorrect casing, underscores Tip: Use C# refactoring to fix these! Example Two Naming and design guidelines

8 private Font ReadFontFromSettings() { XmlDocument doc = new XmlDocument(); XmlDocument doc = new XmlDocument(); doc.Load(GetSettingsXmlPath()); doc.Load(GetSettingsXmlPath()); XmlNode fontNode = doc.SelectSingleNode("Font"); XmlNode fontNode = doc.SelectSingleNode("Font"); float size = float.Parse(fontNode.Attributes["Size"].Value); float size = float.Parse(fontNode.Attributes["Size"].Value); string name = fontNode.Attributes["Name"].Value; string name = fontNode.Attributes["Name"].Value; FontStyle style = (FontStyle)Enum.Parse(typeof(FontStyle), fontNode.Attributes["Style"].Value); FontStyle style = (FontStyle)Enum.Parse(typeof(FontStyle), fontNode.Attributes["Style"].Value); return new Font(name, size, style); return new Font(name, size, style);} Issue: Missing IFormatProvider argument, defaults to CultureInfo.CurrentCulture Example Three Globalization error

9 public class SampleException : Exception { public SampleException() : base() { } public SampleException(string message) : base(message) { } public SampleException(string message, Exception innerException) : base(message, innerException) { } } Issue: Missing [Serializable] attribute and deserialization constructor  Exception cannot be serialized or thrown across AppDomains. Example Four Serialization error

10 Demo: Unmanaged Code Analysis In Visual Studio Team System Nicholas Guerrera Software Design Engineer Visual Studio Team System

11 Example One Buffer overrun void PrintModuleFileName() { wchar_t *p = (wchar_t *)malloc(MAX_PATH); GetModuleFileName(NULL, p, MAX_PATH); printf("%S", p); } Issues Buffer overrun: confusion between character and byte counts Misuse of malloc and GetModuleFileName

12 Example Two Arithmetic overflow long long Shift(int x, int y) { return x << y; } Issue Arithmetic overflow: result is cast to 64-bit after the shift may already have overflown beyond 32-bits.

13 Example Three Incorrect HRESULT usage // Call CoInitialize and return true if it succeeds. bool Initialize() { if (CoInitialize(0)) { return false; } return true; } Issue HRESULT and bool are semantically different, use FAILED or SUCCEEDED macros. Success codes can be non-zero (true in a boolean context). For example, S_FALSE == 0x1

14 Example Four Incorrect printf usage bool PrintStuff() { printf("%s - %d", 22, "twenty-two"); printf("%s - %d", "twenty-two"); printf("%s - %d", "twenty-two", 22, 22); } Issues Type mismatches Too few arguments Too many arguments

15 Example Five Possible NULL dereference void DoWork() { int x, *p; if (Condition()) { p = &x; } else { p = (int *)malloc(sizeof(int)); } *p = 27; } Issue: If Condition() returns false, p could be null Tip: Double-click on messages in the error list to see path highlighting

16 Where To Find Out More Getting started with code analysis Hands-On Lab: Visual Studio Team System, Source Code Analysis: HOL- TLN04 Visual Studio Team System 2005 Beta 2, CTP, or upcoming RTM Discussions on public forums at FxCop is also available as a standalone tool from

17 Questions?

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