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These functions truncate strings that exceed the specified limits. Additionally, some functions, such as strncpy(), do not guarantee that the resulting string is null-terminated. (See STR32-C. Null-terminate byte strings as required.)

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This solution requires that string_data is null-terminated; that is, a null byte can be found within the bounds of the referenced character array. Otherwise, strlen() will stray into other objects before finding a null byte.

Compliant Solution (strcpy_s(), C11 Annex K)

The strcpy_s() function defined in C11 Annex K  [ISO/IEC 9899:2011] , which provides provides additional safeguards, including accepting the size of the destination buffer as an additional argument. (See STR07-C. Use the bounds-checking interfaces for remediation of existing string manipulation code.) Also, strnlen_s() accepts a maximum-length argument for strings that may not be null-terminated.

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If a runtime-constraint error is detected by either the call to either strnlen_s() or strcpy_s(), the currently registered runtime-constraint handler is invoked. See ERR03-C. Use runtime-constraint handlers when calling the bounds-checking interfaces for more information on using runtime-constraint handlers with C11 Annex K functions.

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STR03-EX1: The intent of the programmer is to intentionally purposely truncate the null-terminated byte string.

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Bibliography

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