[Edbrowse-dev] tidy script bug workaround

[Karl Dahlke <eklhad@comcast.net>]

Well if they've been talking about this bug since 2007,
then they might not fix it soon.
With that in mind I was thinking about a preprocessing workaround.
My first attempt looked for strings within scripts,
and then <script within a string,
but that was completely derailed by
	if(whatever.match(/"/)) { do stuff }
The bare regexps make this approach impossible.
So I made the routine even simpler, and I think safer and better.
If it flags a false positive, then the script won't compile and won't run,
which is better than running and doing the wrong thing.
Normally I just push stuff without review,
in the interest of getting things done,
which is perhaps arrogant, and I apologize for that,
but this one I think people should look at first.
It is ready to push if you say go.
The new string is longer than the original,
so I have to use all those dynamic string functions.

/* Work around a nasty bug in tidy5 wherein "<script>" anywhere
 * in a javascript will totally derail things.
 * I turn < into \x3c. */
static char *escapeLessScript(const char *htmltext)
{
	char *ns;		/* new string */
	int ns_l;
	const char *s1, *s2;	/* start and end of script */
	const char *lw;		/* last write */
	const char *q;		/* inner script */

	ns = initString(&ns_l);
	lw = htmltext;

	while (true) {
		s1 = strstrCI(lw, "<script");
		if (!s1)
			break;
//  printf("@@%s", s1);
		s1 += 7;
		if (isalnumByte(*s1)) {	/* <scriptx */
			stringAndBytes(&ns, &ns_l, lw, s1 - lw);
			lw = s1;
			continue;
		}
		s2 = strstrCI(s1, "</script");
		if (!s2)
			goto abort;

/* script now has a start and end */
		stringAndBytes(&ns, &ns_l, lw, s1 - lw);
		lw = s1;

		while (true) {
			q = strstrCI(lw, "<script");
			if (!q || q > s2)
				break;
			stringAndBytes(&ns, &ns_l, lw, q - lw);
			stringAndString(&ns, &ns_l, "\\x3c");
			lw = q + 1;
		}

		stringAndBytes(&ns, &ns_l, lw, s2 - lw);
		lw = s2;
	}

	stringAndString(&ns, &ns_l, lw);
	return ns;

abort:
	nzFree(ns);
	return 0;
}				/* escapeLessScript */