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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

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

        intentionality - logical
        reliability
        Bug
        • cwe
        • symbolic-execution
        • cert

        Pointers marked as "nonnull" may not be set to null, since they are typically not null-checked before use.

        Why is this an issue?

        What is the potential impact?

        How can I fix it?

        More Info

        A function’s return value and parameters may be decorated with attributes to convey additional information to the compiler and/or other developers.

        A commonly used attribute is nonnull which can be used to mark a function’s return value and parameters as shown in the following:

        #include <stdlib.h>
        #include <stdio.h>
        #include <string.h>
        
        __attribute__((returns_nonnull)) int *
        make_array_copy(int *src, size_t len) __attribute__((nonnull(1)));
        
        int *make_array_copy(int *src, size_t len) {
          int *dst = (int *)malloc(len * sizeof(int));
          if (dst == NULL) {
            perror("malloc failed");
            exit(1);
          }
          memcpy(dst, src, len);
          return dst;
        }
        

        The nonnull attribute is meant for other developers and as a hint for compilers. Values marked as nonnull are assumed to have non-null values.

        However, developers may accidentally break the nonnull attribute as shown in the following code snippet:

        __attribute__((returns_nonnull))
        int *foo(__attribute__((nonnull)) int *x) {
          x = 0; // This is compliant but might be surprising, use with caution
          foo(0); // Noncompliant: null is passed as an argument marked as "nonnull"
          return 0; // Noncompliant: return value is marked "nonnull" but null is returned
        }
        

        Failing to adhere to the attribute may introduce serious program errors. In particular, the compiler does not enforce that values marked as nonnull are indeed non-null at runtime; it is the developers' responsibility to adhere to the attribute. These values are typically not null-checked before use. Passing null (i.e., NULL, 0 or nullptr) as an argument to a parameter that is marked as nonnull or returning null from a function marked as returns_nonnull is, hence, likely to cause a null-pointer dereference. Compilers may even apply optimizations based on this attribute and might, for instance, remove an explicit null-check if the parameter is declared as nonnull — even in code outside of the function with the attribute.

        Note that the nonnull attribute is a GNU extension (see nonnull and returns_nonnull) which many compiler vendors have implemented.

        Note that it is allowed to assign null to a parameter marked as nonnull. This attribute is only concerned with the function call contract and does not control the evolution of the parameter variable. For example, a linked-list search could be implemented as follows:

        struct List {
          int value;
          List *next; // nullptr for a tail node.
        };
        
        
        List *findElement(List *l, int elem) __attribute__((nonnull(1)));
        
        List *findElement(List *l, int elem) {
          while(l && l->value != elem)
            l = l->next;
          return l;
        }
        
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