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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 315
  • Vulnerability13
  • Bug76
  • Security Hotspot19
  • Code Smell207

  • Quick Fix 19
Filtered: 35 rules found
symbolic-execution
    Impact
      Clean code attribute
        1. The address of an automatic object should not be assigned to another object that may persist after the first object has ceased to exist

           Bug
        2. Variables should be initialized before use

           Bug
        3. Variables should not be accessed outside of their scope

           Bug
        4. Account validity should be verified when authenticating users with PAM

           Vulnerability
        5. Changing directories improperly when using "chroot" is security-sensitive

           Security Hotspot
        6. POSIX functions should not be called with arguments that trigger buffer overflows

           Vulnerability
        7. Server hostnames should be verified during SSL/TLS connections

           Vulnerability
        8. "pthread_mutex_t" should be unlocked in the reverse order they were locked

           Bug
        9. Only valid arguments should be passed to UNIX/POSIX functions

           Code Smell
        10. "pthread_mutex_t" should be properly initialized and destroyed

           Bug
        11. "pthread_mutex_t" should not be locked when already locked, or unlocked when already unlocked

           Bug
        12. Only valid arguments should be passed to stream functions

           Code Smell
        13. Using publicly writable directories is security-sensitive

           Security Hotspot
        14. Using clear-text protocols is security-sensitive

           Security Hotspot
        15. Blocking functions should not be called inside critical sections

           Code Smell
        16. Return value of "setuid" family of functions should always be checked

           Code Smell
        17. Size of variable length arrays should be greater than zero

           Code Smell
        18. "mktemp" family of functions templates should have at least six trailing "X"s

           Code Smell
        19. Appropriate size arguments should be passed to "strncat" and "strlcpy"

           Code Smell
        20. Server certificates should be verified during SSL/TLS connections

           Vulnerability
        21. Weak SSL/TLS protocols should not be used

           Vulnerability
        22. Integral operations should not overflow

           Bug
        23. Parameter values should be appropriate

           Bug
        24. Stack allocated memory and non-owned memory should not be freed

           Bug
        25. Closed resources should not be accessed

           Bug
        26. Dynamically allocated memory should be released

           Bug
        27. Freed memory should not be used

           Bug
        28. Memory locations should not be released more than once

           Bug
        29. Memory access should be explicitly bounded to prevent buffer overflows

           Bug
        30. Zero should not be a possible denominator

           Bug
        31. XML parsers should not be vulnerable to XXE attacks

           Vulnerability
        32. "nonnull" parameters and return values of "returns_nonnull" functions should not be null

           Bug
        33. Null pointers should not be dereferenced

           Bug
        34. Resources should be closed

           Bug
        35. Unused assignments should be removed

           Code Smell

        Variables should be initialized before use

        intentionality - logical
        reliability
        Bug
        • cwe
        • symbolic-execution
        • based-on-misra

        Variables should be initialized before their use to avoid unexpected behavior due to garbage values.

        Why is this an issue?

        How can I fix it?

        More Info

        A local variable of any built-in type (such as int, float, and pointers), declared without an initial value is not initialized to any particular value. Consequently, if no value is assigned to such a variable first, the code that uses it has no defined behavior.

        int addition() {
          int x;  // x is not initialized
          return x + 10; // Noncompliant: x has grabage value
        }
        
        int dereference() {
          int* p; // p is not initialized
          return *p; // Noncompliant: p has garbage value
        }
        

        Similarly, structures that simply aggregate variables of built-in types, such as arrays or struct/class types without a constructor, will not initialize their members when declared without an initializer:

        struct Aggregate {
          int i;
          float f;
        };
        
        void aggregates() {
          int* intArray[5]; // each element of array is not initializer
          Aggregate aggr; // members aggr.i, agrr.f are not initialized
          Aggregate aggrArray[2]; // members of each element are not initialized
        }
        

        Finally, allocating objects of builtin or such aggregates types on the heap, also does not initialize their values:

        void usingMalloc() {
          int* intArr = (int*)malloc(sizeof(int) * 10); // each of 10 allocated integers is not initialized
        }
        

        This also applies when new is used in C++:

        void usingNew() {
          Aggregate* aggrPtr = new Aggregate; // members of allocated Aggregate are not initialized
          Aggregate* aggrArr = new Aggregate[5]; // members of each of 5 Aggregate objects are not initialized
        }
        

        What is the potential impact?

        Using garbage values will cause the program to behave nondeterministically at runtime. The program may produce a different output or crash depending on the run.

        In some situations, loading a variable may expose sensitive data, such as a password that was previously stored in the same location, leading to a vulnerability that uses such a defect as a gadget for extracting information from the instance of the program.

        Finally, in C++, outside of a few exceptions related to the uses of unsigned char or std::byte, loading data from an uninitialized variable causes undefined behavior. This means that the compiler is not bound by the language standard anymore, and the program has no meaning assigned to it. As a consequence, the impact of such a defect is not limited to the use of garbage values.

        Why is there an issue for a class with a default constructor?

        In C++, a class can define a default constructor invoked when an object of the given type is created. Such a constructor is called even if a variable is declared without any initializer. However, if the constructor code omits the initialization of a member that itself does not have the default constructor, the member will remain uninitialized (See also S2107). And reading from it will produce a garbage value:

        struct Partial {
          // x is not initialized
          Partial() : y(10.0) {}
        
          int x;
          float y;
        };
        
        int initialized() {
          Partial p; // constructor is called
          // or even Partial p{};
          return p.x; // Non-compliant: reading an uninitialized variable
        }
        

        Exceptions

        This rule does not flag the variables with static storage duration, meaning: global, static, and thread-local variables.

        All the variables with static storage duration are zero-initialized before the initializer is evaluated. As a consequence, any variable or member of such an object has a defined value even if no initializer is specified.

        int globInt;
        int globTab[10];
        Aggregate globAggr;
        Partial globPart; // x member is zero-initialized
        
        int uses() {
          static int staticInt;
          return globInt     // Compliant: all zero-initialized
               + globTab[2]
               + globAggr.f
               + globPart.x
               + staticInt;
        }
        
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