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C#

C# static code analysis

Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C# code

  • All rules 493
  • Vulnerability46
  • Bug88
  • Security Hotspot24
  • Code Smell335

  • Quick Fix 61
Filtered: 17 rules found
symbolic-execution
    Impact
      Clean code attribute
        1. Locks should be released within the same method

           Bug
        2. A write lock should not be released when a read lock has been acquired and vice versa

           Bug
        3. First/Single should be used instead of FirstOrDefault/SingleOrDefault on collections that are known to be non-empty

           Code Smell
        4. JWT secret keys should not be disclosed

           Vulnerability
        5. Types allowed to be deserialized should be restricted

           Vulnerability
        6. Secure random number generators should not output predictable values

           Vulnerability
        7. Empty collections should not be accessed or iterated

           Bug
        8. Objects should not be disposed more than once

           Code Smell
        9. Calculations should not overflow

           Bug
        10. Arguments of public methods should be validated against null

           Code Smell
        11. Empty nullable value should not be accessed

           Bug
        12. Cipher Block Chaining IVs should be unpredictable

           Vulnerability
        13. Boolean expressions should not be gratuitous

           Code Smell
        14. Conditionally executed code should be reachable

           Bug
        15. Null pointers should not be dereferenced

           Bug
        16. Locks should be released on all paths

           Bug
        17. Password hashing functions should use an unpredictable salt

           Vulnerability

        Null pointers should not be dereferenced

        intentionality - logical
        reliability
        Bug
        • cwe
        • symbolic-execution

        Why is this an issue?

        How can I fix it?

        More Info

        Accessing a null value will always throw a NullReferenceException most likely causing an abrupt program termination.

        Such termination might expose sensitive information that a malicious third party could exploit to, for instance, bypass security measures.

        Exceptions

        In the following cases, the rule does not raise:

        Extensions Methods

        Calls to extension methods can still operate on null values.

        using System;
        using System.Text.RegularExpressions;
        
        public static class Program
        {
            public static string RemoveVowels(this string value)
            {
                if (value == null)
                {
                    return null;
                }
                return Regex.Replace(value, "[aeoui]*","", RegexOptions.IgnoreCase);
            }
        
            public static void Main()
            {
                Console.WriteLine(((string?)null).RemoveVowels());  // Compliant: 'RemoveVowels' is an extension method
            }
        }
        

        Unreachable code

        Unreachable code is not executed, thus null values will never be accessed.

        public void Method()
        {
            object o = null;
            if (false)
            {
                o.ToString();    // Compliant: code is unreachable
            }
        }
        

        Validated value by analysis attributes

        Nullable analysis attributes enable the developer to annotate methods with information about the null-state of its arguments. Thus, potential null values validated by one of the following attributes will not raise:

        • NotNullAttribute
        • NotNullWhenAttribute
        • DoesNotReturnAttribute
        • DoesNotReturnIfAttribute

        It is important to note those attributes are only available starting .NET Core 3. As a workaround, it is possible to define those attributes manually in a custom class:

        using System;
        
        public sealed class NotNullAttribute : Attribute { } // The alternative name 'ValidatedNotNullAttribute' is also supported
        
        public static class Guard
        {
            public static void NotNull<T>([NotNull] T value, string name) where T : class
            {
                if (value == null)
                {
                    throw new ArgumentNullException(name);
                }
            }
        }
        
        public static class Utils
        {
            public static string Normalize(string value)
            {
                Guard.NotNull(value, nameof(value)); // Will throw if value is null
                return value.ToUpper(); // Compliant: value is known to be not null here.
            }
        }
        

        Validated value by Debug.Assert

        A value validated with Debug.Assert to not be null is safe to access.

        using System.Diagnostics;
        
        public void Method(object myObject)
        {
            Debug.Assert(myObject != null);
            myObject.ToString(); // Compliant: 'myObject' is known to be not null here.
        }
        

        Validated value by IDE-specific attributes

        Like with null-analysis-attribute, potential null values validated by one of the following IDE-specific attributes will not raise

        Visual Studio
        • ValidatedNotNullAttribute (The attribute is interpreted the same as the NotNullAttribute)
        JetBrains Rider
        • NotNullAttribute
        • TerminatesProgramAttribute
          using System;
          using JetBrains.Annotations;
          
          public class Utils
          {
              [TerminatesProgram]
              public void TerminateProgram()
              {
                  Environment.FailFast("A catastrophic failure has occurred.")
              }
          
              public void TerminatesProgramIsRespected()
              {
                  object myObject = null;
                  TerminateProgram();
                  myObject.ToString(); // Compliant: unreachable
              }
          }
          

        Null forgiving operator

        Expression marked with the null forgiving operator

        public void Method()
        {
            object o = null;
            o!.ToString();    // Compliant: the null forgiving operator suppresses the nullable warning
        }
        
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