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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: 59 rules found
cwe
    Impact
      Clean code attribute
        1. Function-like macros should not be invoked without all of their arguments

           Bug
        2. Function exit paths should have appropriate return values

           Bug
        3. The number of arguments passed to a function should match the number of parameters

           Bug
        4. Non-empty statements should change control flow or have at least one side-effect

           Bug
        5. Bitwise operators should not be applied to signed operands

           Bug
        6. Limited dependence should be placed on operator precedence

           Code Smell
        7. Variables should be initialized before use

           Bug
        8. Hard-coded secrets are security-sensitive

           Security Hotspot
        9. "sprintf" should not be used

           Security Hotspot
        10. Changing working directories without verifying the success is security-sensitive

           Security Hotspot
        11. Setting capabilities is security-sensitive

           Security Hotspot
        12. Accessing files should not introduce TOCTOU vulnerabilities

           Vulnerability
        13. Account validity should be verified when authenticating users with PAM

           Vulnerability
        14. Using "tmpnam", "tmpnam_s" or "tmpnam_r" is security-sensitive

           Security Hotspot
        15. Using "strncpy" or "wcsncpy" is security-sensitive

           Security Hotspot
        16. Using "strncat" or "wcsncat" is security-sensitive

           Security Hotspot
        17. Using "strcat" or "wcscat" is security-sensitive

           Security Hotspot
        18. Using "strlen" or "wcslen" is security-sensitive

           Security Hotspot
        19. Changing directories improperly when using "chroot" is security-sensitive

           Security Hotspot
        20. Using "strcpy" or "wcscpy" is security-sensitive

           Security Hotspot
        21. "memset" should not be used to delete sensitive data

           Vulnerability
        22. POSIX functions should not be called with arguments that trigger buffer overflows

           Vulnerability
        23. Cipher algorithms should be robust

           Vulnerability
        24. Encryption algorithms should be used with secure mode and padding scheme

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

           Vulnerability
        26. "pthread_mutex_t" should not be locked when already locked, or unlocked when already unlocked

           Bug
        27. Using publicly writable directories is security-sensitive

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

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

           Code Smell
        30. Expanding archive files without controlling resource consumption is security-sensitive

           Security Hotspot
        31. Server certificates should be verified during SSL/TLS connections

           Vulnerability
        32. Using weak hashing algorithms is security-sensitive

           Security Hotspot
        33. Cryptographic keys should be robust

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

           Vulnerability
        35. Dynamically allocated memory should be released

           Bug
        36. Freed memory should not be used

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

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

           Bug
        39. Zero should not be a possible denominator

           Bug
        40. "sizeof" should not be called on pointers

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

           Vulnerability
        42. Multiline blocks should be enclosed in curly braces

           Code Smell
        43. "nonnull" parameters and return values of "returns_nonnull" functions should not be null

           Bug
        44. Setting loose POSIX file permissions is security-sensitive

           Security Hotspot
        45. Conditionally executed code should be reachable

           Bug
        46. Null pointers should not be dereferenced

           Bug
        47. Using pseudorandom number generators (PRNGs) is security-sensitive

           Security Hotspot
        48. Resources should be closed

           Bug
        49. Hard-coded passwords are security-sensitive

           Security Hotspot
        50. Code annotated as deprecated should not be used

           Code Smell
        51. Unused assignments should be removed

           Code Smell
        52. All code should be reachable

           Bug
        53. "switch" statements should have "default" clauses

           Code Smell
        54. Switch cases should end with an unconditional "break" statement

           Code Smell
        55. Track uses of "TODO" tags

           Code Smell
        56. Track uses of "FIXME" tags

           Code Smell
        57. Assignments should not be made from within conditions

           Code Smell
        58. Insecure functions should not be used

           Vulnerability
        59. "scanf()" and "fscanf()" format strings should specify a field width for the "%s" string placeholder

           Vulnerability

        Using "strncpy" or "wcsncpy" is security-sensitive

        consistency - conventional
        security
        Security Hotspot
        • cwe
        • cert

        In C, a string is just a buffer of characters, normally using the null character as a sentinel for the end of the string. This means that the developer has to be aware of low-level details such as buffer sizes or having an extra character to store the final null character. Doing that correctly and consistently is notoriously difficult and any error can lead to a security vulnerability, for instance, giving access to sensitive data or allowing arbitrary code execution.

        The function char *strncpy(char * restrict dest, const char * restrict src, size_t count); copies the first count characters from src to dest, stopping at the first null character, and filling extra space with 0. The wcsncpy does the same for wide characters and should be used with the same guidelines.

        Both of those functions are designed to work with fixed-length strings and might result in a non-null-terminated string.

        Ask Yourself Whether

        • There is a possibility that either the source or the destination pointer is null
        • The security of your system can be compromised if the destination is a truncated version of the source
        • The source buffer can be both non-null-terminated and smaller than the count
        • The destination buffer can be smaller than the count
        • You expect dest to be a null-terminated string
        • There is an overlap between the source and the destination

        There is a risk if you answered yes to any of those questions.

        Recommended Secure Coding Practices

        • C11 provides, in its annex K, the strncpy_s and the wcsncpy_s that were designed as safer alternatives to strcpy and wcscpy. It’s not recommended to use them in all circumstances, because they introduce a runtime overhead and require to write more code for error handling, but they perform checks that will limit the consequences of calling the function with bad arguments.
        • Even if your compiler does not exactly support annex K, you probably have access to similar functions
        • If you are using strncpy and wsncpy as a safer version of strcpy and wcscpy, you should instead consider strcpy_s and wcscpy_s, because these functions have several shortcomings:
          • It’s not easy to detect truncation
          • Too much work is done to fill the buffer with 0, leading to suboptimal performance
          • Unless manually corrected, the dest string might not be null-terminated
        • If you want to use strcpy and wcscpy functions and detect if the string was truncated, the pattern is the following:
          • Set the last character of the buffer to null
          • Call the function
          • Check if the last character of the buffer is still null
        • If you are writing C++ code, using std::string to manipulate strings is much simpler and less error-prone

        Sensitive Code Example

        int f(char *src) {
          char dest[256];
          strncpy(dest, src, sizeof(dest)); // Sensitive: might silently truncate
          return doSomethingWith(dest);
        }
        

        Compliant Solution

        int f(char *src) {
          char dest[256];
          dest[sizeof dest - 1] = 0;
          strncpy(dest, src, sizeof(dest)); // Compliant
          if (dest[sizeof dest - 1] != 0) {
            // Handle error
          }
          return doSomethingWith(dest);
        }
        

        See

        • OWASP - Top 10 2021 Category A6 - Vulnerable and Outdated Components
        • OWASP - Top 10 2017 Category A9 - Using Components with Known Vulnerabilities
        • CWE - CWE-120 - Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
        • CERT, STR07-C. - Use the bounds-checking interfaces for string manipulation
        • STIG Viewer - Application Security and Development: V-222612 - The application must not be vulnerable to overflow attacks.
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