The New C Standard Explored 

C11 specifies many security features that require minimal changes to existing code. They greatly reduce unexpected behavior and prevent many kinds of common attacks.

C and C++ are members of the same family of languages. The evolutionary boldness of C++ removes some of the marketplace pressure on C; people who are continually pushing for innovation are naturally drawn to the C++ development process. Each language had a coherent original design (by Dennis Ritchie and Bjarne Stroustrup, respectively), followed by successive refinement in a very competitive marketplace of ideas. Both languages share an extreme concern for performance, with the slogan "don't leave space for a more-efficient systems-programming language underneath our language (C or C++)." However, it's unfair to complain that the original designs assigned too little importance to cybersecurity; both languages pre-date the beginnings of concern for security. But in recent years, as the marketplace has started to emphasize cybersecurity, C and C++ have been responding in several ways.

The C11 Annex K Functions

I'll start my tour of Annex K with the fopen_s function. The main innovation is that files are opened with exclusive (also known as non-shared) access. Furthermore, if the mode string doesn't begin with u (such as with code being updated from the older fopen ), then to the extent that the underlying system supports it, the file gets a file permission that prevents other users on the system from accessing the file.

In this article, I'll sequentially enumerate the security benefits of these _s functions. The new semantics illustrate the pattern of "least privilege." This "exclusive" mode was previously available in the Posix open() function, but the ISO standard for C doesn't standardize system-dependent, low-level I/O.

fopen() safety

If a file is opened with x as the last character in the mode argument, and the requested filename is already in use, the fopen_s function fails (as opposed to truncating the existing file, which is presumably already being used by someone).

Fixing tmpnam()

This function illustrates another security pattern in C11: "In the calling sequence of the function, every pointer through which the function might modify an array is immediately followed by the number of elements which the function is permitted to modify."