upstream: don't allow \0 characters in url-encoded strings.

Suggested by David Leadbeater, ok deraadt@

OpenBSD-Commit-ID: c92196cef0f970ceabc1e8007a80b01e9b7cd49c

Author: djmdjm

misc.c

@@ -1,4 +1,4 @@
-/* $OpenBSD: misc.c,v 1.204 2025/09/02 09:34:48 djm Exp $ */
+/* $OpenBSD: misc.c,v 1.205 2025/09/04 00:30:06 djm Exp $ */
 /*
  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  * Copyright (c) 2005-2020 Damien Miller.  All rights reserved.
@@ -994,17 +994,18 @@ urldecode(const char *src)
 	size_t srclen;
 
 	if ((srclen = strlen(src)) >= SIZE_MAX)
-		fatal_f("input too large");
+		return NULL;
 	ret = xmalloc(srclen + 1);
 	for (dst = ret; *src != '\0'; src++) {
 		switch (*src) {
 		case '+':
 			*dst++ = ' ';
 			break;
 		case '%':
+			/* note: don't allow \0 characters */
 			if (!isxdigit((unsigned char)src[1]) ||
 			    !isxdigit((unsigned char)src[2]) ||
-			    (ch = hexchar(src + 1)) == -1) {
+			    (ch = hexchar(src + 1)) == -1 || ch == 0) {
 				free(ret);
 				return NULL;
 			}