include: ssp: round out fortification of current set of headers

[kevans]

Summary

ssp/ssp.h needed some improvements:

• len isn't always a size_t, it may need casted
• In some cases we may want to use a len that isn't specified as a parameter (e.g., L_ctermid), so __ssp_redirect() should be more flexible.
• In other cases we may want additional checking, so pull all of the declaration bits out of __ssp_redirect_raw() so that some functions can implement the body themselves.

strlcat/strlcpy should be the last of the fortified functions that get
their own __*_chk symbols, and these cases are only done to be
consistent with the rest of the str*() set.

Sponsored by: Stormshield
Sponsored by: Klara, Inc.

[kevans]

Fix libc build without FORTIFY_SOURCE enabled

[markj]

lib/libc/secure/strlcat_chk.c

47

We know that n <= dbufsize, and the loop predicate checks n-- != 0 so this condition is always false.

lib/libc/secure/strlcpy_chk.c

27–28

Do you want to check dbufsize > 0 here?

28

Do you actually need to undef?

lib/libc/stdio/fread.c

50–51

This line is too long.

[kevans]

Reduce __strlcpy_chk to size check + strlcpy(), address review feedback

[kevans]

lib/libc/secure/strlcpy_chk.c

27–28

Looking at it again, I'm not sure it actually makes sense to inline strlcpy like this anyways... n passed in is supposed to cover room for the NUL terminator, so it should be sufficient to just __bos it up front then call into the real strlcpy