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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

        Size of variable length arrays should be greater than zero

        intentionality - logical
        maintainability
        Code Smell
        • symbolic-execution
        • suspicious

        Creating a Variable Length Array (VLA) with a size that is not greater than zero leads to undefined behavior.

        Why is this an issue?

        How can I fix it?

        Going the extra mile

        More Info

        Variable length arrays are used to allocate a stack size for the number of elements that are known at the runtime, for example:

        void merge(int* tab, int size, int first) {
          int res[size]; // allocate buffer for merging on stack
          /* Code that merges two sorted ranges [tab, tab + first) and [tab + first, tab + last)
           * into res buffer.
           * ....
           */
          // copy merged data into input
          memcpy(tab, res, size * sizeof(int));
        }
        

        The syntax follows the one used by an array with static size (where size is a constant), and the value placed in the square brackets ([size] in the above example) determines the size of the array. For both static and runtime-sized arrays, the size is required to be greater than zero. However, in the case of VLAs, this cannot be checked by the compiler, and any program that creates such an array with a size that has a value of zero or is negative, has undefined behavior.

        void example() {
          int s = -1;
          int vla[s];  // program compiles, and have undefined behavior
          int arr[-1]; // program is ill-formed
        }
        

        This defect may also manifest when the variable used as size is not initialized. Uninitialized variables might have zero, negative, or any value at each time the program executes.

        void uninitialized() {
          int s;      // uninitialized, the value is not determined
          int vla[s]; // program compiles, have undefined behavior if the value read from s is negative or zero
        }
        

        A non-positive size of the VLAs may also result from using a value loaded by the program from a file or other external resources used as size without previous validation. Such values as usually referred to as being tainted.

        void loadFromInput() {
          int size = -1;
          scanf("%d", &size); // loads size from input
          char bytes[size];   // size may be negative
          /* ... */
        }
        

        The above code will lead to undefined behavior when the value of the size load from the input is not greater than zero. This may happen due to source data corruption, accidental user mistake, or malicious action.

        What is the potential impact?

        Creating a variable length array with a size smaller or equal to zero leads to undefined behavior. This means the compiler is not bound by the language standard anymore, and your program has no meaning assigned to it.

        Practically this can lead to a wide range of effects and may lead to the following:

        • crashes, in particular segmentation faults, when the program access memory that it is not allowed to,
        • memory corruption and data losses, when the program overwrites bytes responsible for storing data or executable code,
        • stack overflow, when negative size is interpreted as a large positive number.

        Furthermore, in a situation when VLA size is dependent on the user input, it can lead to vulnerabilities in the program.

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          Available Since
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