Apple's libc shells out to Perl to implement wordexp

Apple's libc shells out to Perl to implement wordexp
github.com

http://linux.die.net/man/3/wordexp

wordexp, wordfree - perform word expansion like a posix-shell

So, the implementer decided to take the short route, and just spawn a shell which, essentially, gets passed the input data to wordexp(), to do the work. But, of course, having something that starts with such a comment...

/* XXX this is _not_ designed to be fast (...) wordexp is also rife with security "challenges", unless you pass it WRDE_NOCMD it must support subshell expansion, and even if you don't beause it has to support so much of the standard shell (all the odd little variable expansion options for example) it is hard to do without a subshell). It is probably just plan a Bad Idea to call in anything setuid, or executing remotely. */

...in your standard C library wasn't such a smart idea to start with. Scroll down, there are many more gems in the comments!

Sometimes it's better to just implement it as

        void wordexp() {
                fprintf(stderr,"wordexp() is a security nightmare. Not implemented.\n");
                assert(0);
        }

(EDIT: typos)

And Apple have always been masters in selling polished, nicely packages shit as the most advanced technology ever conceived.

In an ideal world, we'd have a libsh that exposed all of the steps of what /bin/sh does in a nice fashion, this function would call one of the libsh functions, and /bin/sh would be a 10-line while (true) { libsh_this(); libsh_that(); }.

In a slightly less ideal world, the shell would have a way to separate things with null characters, without bothering Perl.

We really don't live in an ideal world.