What is it?

This is a standalone implementation of fortify source level 3, providing compile time security checks. It is libc-agnostic and simply overlays the system headers by using the #include_next extension found in GCC, and black magic on Clang. It was initially intended to be used on musl based Linux distributions.

Features

• It is portable, works on *BSD, Linux, Solaris and possibly others.
• It will only trap non-conformant programs. This means that fortify level 2 is treated in the same way as level 1.
• Avoids making function calls when undefined behaviour has already been invoked. This is handled by using __builtin_trap().
• Support for out-of-bounds read interfaces, such as send(), write(), fwrite() etc.
• No ABI is enforced. All of the fortify check functions are inlined into the resulting binary.
• It has a comprehensive suite of tests, running both on Clang and on GCC for every commit, on C89, C99, C11 and C17, with significant coverage
• Defining FORTIFY_USE_NATIVE_CHK will make use of compiler-provided builtin _chk functions, which might be a bit better in term of diagnostics, but won't necessarily provide the same amount of security checks.
• Defining FORTIFY_PEDANTIC_CHECKS will enable pedantic checks, that while technically correct, might break some programs relying on widely accepted undefined-behaviours.

Sample usage

If you want to quickly test it, you can try something like the following:

cat > fgets.c <<EOF
#include <stdio.h>
int
main(void)
{
	char buf[BUFSIZ];
	fgets(buf, sizeof(buf) + 1, stdin);
	return 0;
}
EOF
cc -I<path-to-fortify-include-dir> -D_FORTIFY_SOURCE=3 -O1 fgets.c
./a.out

At this point, the program will safely and loudly crash.

Supported interfaces

• FD_CLR
• FD_SET
• asprintf
• bcopy
• bzero
• calloc
• confstr
• fdopen
• fgets
• fgetws
• fmemopen
• fopen
• fprintf
• fread
• fwrite
• getcwd
• getdomainname
• getgroups
• gethostname
• getlogin_r
• malloc
• mbsnrtowcs
• mbsrtowcs
• mbstowcs
• memchr
• memcpy
• memmove
• mempcpy
• memset
• poll
• popen
• ppoll
• pread
• printf
• pwrite
• qsort
• read
• readlink
• readlinkat
• realloc
• reallocarray
• realpath
• recv
• recvfrom
• select
• send
• sendto
• snprintf
• sprintf
• stpcpy
• stpncpy
• strcat
• strchr
• strcpy
• strlcat
• strlcpy
• strlen
• strncat
• strncpy
• strrchr
• tmpfile
• ttyname_r
• umask
• vfprintf
• vprintf
• vasprintf
• vsnprintf
• vsprintf
• wcrtomb
• wcscat
• wcscpy
• wcsncat
• wcsncpy
• wcsnrtombs
• wcsrtombs
• wcstombs
• wctomb
• wmemcpy
• wmemmove
• wmemset
• write