Fix #78862: link() silently truncates after a null byte on Windows

Since link() is supposed to accepts paths (i.e. strings without NUL
bytes), we must not accept arbitrary strings.

Author: cmb69

ext/standard/link_win32.c

@@ -211,7 +211,7 @@ PHP_FUNCTION(link)
 
 	/*First argument to link function is the target and hence should go to frompath
 	  Second argument to link function is the link itself and hence should go to topath */
-	if (zend_parse_parameters(ZEND_NUM_ARGS(), "ss", &frompath, &frompath_len, &topath, &topath_len) == FAILURE) {
+	if (zend_parse_parameters(ZEND_NUM_ARGS(), "pp", &frompath, &frompath_len, &topath, &topath_len) == FAILURE) {
 		return;
 	}
 

ext/standard/tests/file/windows_links/bug78862.phpt

@@ -0,0 +1,17 @@
+--TEST--
+Bug #78862 (link() silently truncates after a null byte on Windows)
+--FILE--
+<?php
+file_put_contents(__DIR__ . '/bug78862.target', 'foo');
+var_dump(link(__DIR__ . "/bug78862.target\0more", __DIR__ . "/bug78862.link\0more"));
+var_dump(file_exists(__DIR__ . '/bug78862.link'));
+?>
+--EXPECTF--
+Warning: link() expects parameter 1 to be a valid path, string given in %s on line %d
+NULL
+bool(false)
+--CLEAN--
+<?php
+unlink(__DIR__ . '/bug78862.target');
+unlink(__DIR__ . '/bug78862.link');
+?>