Fix phpGH-16523: FILTER_FLAG_HOSTNAME accepts ending hyphen

Domain name labels must not end with a hyphen, and that is also true
for the last label.  Apparently, this has been overlooked so far.

Closes phpGH-16540.

NEWS

@@ -42,6 +42,9 @@ PHP NEWS
  . Fixed bug GH-16397 (Segmentation fault when comparing FFI object).
  (nielsdos)
 
+- Filter:
+ . Fixed bug GH-16523 (FILTER_FLAG_HOSTNAME accepts ending hyphen). (cmb)
+
 - GD:
  . Fixed bug GH-16334 (imageaffine overflow on matrix elements).
  (David Carlier)

ext/filter/logical_filters.c

@@ -542,7 +542,7 @@ static int _php_filter_validate_domain(char * domain, size_t len, zend_long flag
  /* Reset label length counter */
  i = 1;
  } else {
- if (i > 63 || (hostname && *s != '-' && !isalnum((int)*(unsigned char *)s))) {
+ if (i > 63 || (hostname && (*s != '-' || *(s + 1) == '\0') && !isalnum((int)*(unsigned char *)s))) {
  return 0;
  }
 

ext/filter/tests/gh16523.phpt

@@ -0,0 +1,20 @@
+--TEST--
+GH-16523 (FILTER_FLAG_HOSTNAME accepts ending hyphen)
+--EXTENSIONS--
+filter
+--FILE--
+<?php
+$domains = [
+ 'a-.bc.com',
+ 'a.bc-.com',
+ 'a.bc.com-',
+];
+
+foreach ($domains as $domain) {
+ var_dump(filter_var($domain, FILTER_VALIDATE_DOMAIN, FILTER_FLAG_HOSTNAME));
+}
+?>
+--EXPECT--
+bool(false)
+bool(false)
+bool(false)