Upon return, functions should guarantee that any object returned by the function, or any modified value referenced by a pointer argument, is a valid object of function return type or argument type. Otherwise, type errors can occur in the program.
A good example is the null-terminated byte string type in C. If a string lacks the terminating null character, the program may be tricked into accessing storage after the string as legitimate data. A program may, as a result, process a string it should not process, which might be a security flaw in itself. It may also cause the program to abort, which might be a denial-of-service attack.
The emphasis of this recommendation is to avoid producing unterminated strings; it does not address processing of already existing unterminated strings. However, by preventing the creation of unterminated strings, the need to process them is greatly lessened.
Noncompliant Code Example
strncpy() function does not guarantee that the resulting string is null-terminated. If there is no null character in the first
n characters of the
source array, the result may not be null-terminated.
Compliant Solution (
strncpy_s(), C11 Annex K)
The C11 Annex K
strncpy_s() function copies up to
n characters from the source array to a destination array. If no null character was copied from the source array, the
nth position in the destination array is set to a null character, guaranteeing that the resulting string is null-terminated.
Failure to enforce type safety can result in type errors in the program.
Cast alters value
Key here (explains table format and definitions)
|ISO/IEC TR 24772:2013||String Termination [CJM]||Prior to 2018-01-12: CERT: Unspecified Relationship|
|MITRE CWE||CWE-192||Prior to 2018-01-12:|
|MITRE CWE||CWE-227||Prior to 2018-01-12:|
|MITRE CWE||CWE-590||Prior to 2018-01-12:|
|MITRE CWE||CWE-686||Prior to 2018-01-12:|
|MITRE CWE||CWE-704||Prior to 2018-01-12:|
|MITRE CWE||CWE-761||Prior to 2018-01-12:|
|MITRE CWE||CWE-762||Prior to 2018-01-12:|
|MITRE CWE||CWE-843||Prior to 2018-01-12:|