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Alternative functions that limit the number of bytes copied are often recommended to mitigate buffer overflow vulnerabilities, for example:

• strncpy() instead of strcpy()
• fgets() instead of gets()
• snprintf() instead of sprintf()

These function truncate strings that exceed the specified limits. Additionally, some functions such as strncpy() do not guarantee that the resulting string is null-terminated .
Truncation results in a loss of data, and in some cases, leads to software vulnerabilities.

Non-Compliant Code Example

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The correct solution depends on the original intent.   If your intent was to truncate a string but ensure that the
result was a null-terminated string the following solution can be used.

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An exception to this rule applies if the intent of the programmer was to convert a null-terminated byte string to a character array.  To be compliant with this standard, this intent must be made clear statement in comments.

Priority: P12 Level: L1

Failure to properly null terminate null-termianted byte strings can result in buffer overflows and the execution of arbitrary code with the permissions of the vulnerable process by an attacker.

References

• ISO/IEC 9899-1999 Section 7.1.1 Definitions of terms, Section 7.21 String handling <string.2.4 The strncpy functionh>
• Seacord 05 Chapter 2 Strings
• ISO/IEC 9899-1999TR 24731-2006 Section 6.7.211.3 .2 The strncat functionSAMATE Reference Dataset Test Case ID 000-000-004strcpy_s function