acl: Avoid undefined behaviour due to 32-bit shift.

[paraslash.git] / acl.c

diff --git a/acl.c b/acl.c
index 62677711e34f7c00e732bb049c705d08a9a3b8e1..75fdc55b12842890136afec74e70125f81b6318c 100644 (file)
--- a/acl.c
+++ b/acl.c
@@ -1,8 +1,4 @@
-/*
- * Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 2005 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 
 /** \file acl.c Access control lists for paraslash senders. */
 
@@ -35,10 +31,12 @@ struct access_info {
 /**
  * Return true if addr_1 matches addr_2 in the first `netmask' bits.
  */
-static int v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
+static bool v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
 {
        uint32_t mask = ~0U;
 
+       if (netmask == 0) /* avoid 32-bit shift, which is undefined in C. */
+               return true;
        if (netmask < 32)
                mask <<= (32 - netmask);
        return (htonl(addr_1) & mask) == (htonl(addr_2) & mask);