fortify-headers/README

What is it?
===========

This is a standalone implementation of fortify source[0].  It is libc-agnostic
and simply overlays the system headers by using the #include_next extension found
in GCC and clang.  It was initially intended to be used on musl[1] based Linux
distributions.


Features
========

- It is portable, works on *BSD, Linux and possibly other systems.
- 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 UB 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.


Sample usage
============

A plan for integrating fortify into a system is still under discussion.
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=1 -O1 fgets.c
./a.out

At this point, the program will crash.


Supported interfaces
====================

FD_CLR
FD_SET
bcopy
bzero
confstr
fgets
fgetws
fread
fwrite
getcwd
getdomainname
getgroups
gethostname
getlogin_r
mbsnrtowcs
mbsrtowcs
mbstowcs
memcpy
memmove
mempcpy
memset
poll
ppoll
pread
read
readlink
readlinkat
realpath
recv
recvfrom
send
sendto
snprintf
sprintf
stpcpy
stpncpy
strcat
strcpy
strlcat
strlcpy
strncat
strncpy
ttyname_r
vsnprintf
vsprintf
wcrtomb
wcscat
wcscpy
wcsncat
wcsncpy
wcsnrtombs
wcsrtombs
wcstombs
wctomb
wmemcpy
wmemmove
wmemset
write


[0] http://gcc.gnu.org/ml/gcc-patches/2004-09/msg02055.html
[1] http://www.musl-libc.org/