From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34342) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WkNl0-00084c-7v for qemu-devel@nongnu.org; Tue, 13 May 2014 21:13:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WkNku-00080V-5T for qemu-devel@nongnu.org; Tue, 13 May 2014 21:13:18 -0400 Received: from toccata.ens-lyon.fr ([140.77.166.68]:43361 helo=toccata.ens-lyon.org) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WkNkt-00080R-Ul for qemu-devel@nongnu.org; Tue, 13 May 2014 21:13:12 -0400 Received: from localhost (localhost [127.0.0.1]) by toccata.ens-lyon.org (Postfix) with ESMTP id 80A0F8409A for ; Wed, 14 May 2014 03:13:11 +0200 (CEST) Received: from toccata.ens-lyon.org ([127.0.0.1]) by localhost (toccata.ens-lyon.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id cQzL1GcFLNhq for ; Wed, 14 May 2014 03:13:11 +0200 (CEST) Received: from type.ipv6 (youpi.perso.aquilenet.fr [80.67.176.89]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by toccata.ens-lyon.org (Postfix) with ESMTPSA id 2D5AE8406F for ; Wed, 14 May 2014 03:13:11 +0200 (CEST) Received: from samy by type.ipv6 with local (Exim 4.82) (envelope-from ) id 1WkNkr-0004Gi-P7 for qemu-devel@nongnu.org; Wed, 14 May 2014 03:13:09 +0200 Date: Wed, 14 May 2014 03:13:09 +0200 From: Samuel Thibault Message-ID: <20140514011309.GY6302@type.youpi.perso.aquilenet.fr> References: <1396218189-14422-1-git-send-email-samuel.thibault@ens-lyon.org> <1396218189-14422-2-git-send-email-samuel.thibault@ens-lyon.org> <20140507221509.GA3302@type.youpi.perso.aquilenet.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140507221509.GA3302@type.youpi.perso.aquilenet.fr> Subject: [Qemu-devel] [PATCHv2, DoS] slirp (arp): do not special-case bogus IP addresses List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Do not special-case addresses with zero host part, as we do not necessarily know how big it is, and the guest can fake them anyway. Silently avoid having 0.0.0.0 as a destination, however. Signed-off-by: Samuel Thibault --- This is particularly bad actually, one can for instance simply do this inside a Linux guest ip addr add 192.0.0.0/1 dev eth0 and crash qemu (thus a DoS) by just emitting a packet (thus from 192.0.0.0), getting: qemu-system-x86_64: /usr/src/qemu/slirp/arp_table.c:77: arp_table_search: Assertion `(ip_addr & __bswap_32 (~(0xfU << 28))) != 0' failed. so it should probably go to all stable maintained versions. diff --git a/slirp/arp_table.c b/slirp/arp_table.c index ecdb0ba..bcaeb44 100644 --- a/slirp/arp_table.c +++ b/slirp/arp_table.c @@ -37,12 +37,7 @@ void arp_table_add(Slirp *slirp, uint32_t ip_addr, uint8_t ethaddr[ETH_ALEN]) ethaddr[0], ethaddr[1], ethaddr[2], ethaddr[3], ethaddr[4], ethaddr[5])); - /* Check 0.0.0.0/8 invalid source-only addresses */ - if ((ip_addr & htonl(~(0xfU << 28))) == 0) { - return; - } - - if (ip_addr == 0xffffffff || ip_addr == broadcast_addr) { + if (ip_addr == 0 || ip_addr == 0xffffffff || ip_addr == broadcast_addr) { /* Do not register broadcast addresses */ return; } @@ -73,9 +68,6 @@ bool arp_table_search(Slirp *slirp, uint32_t ip_addr, DEBUG_CALL("arp_table_search"); DEBUG_ARG("ip = 0x%x", ip_addr); - /* Check 0.0.0.0/8 invalid source-only addresses */ - assert((ip_addr & htonl(~(0xfU << 28))) != 0); - /* If broadcast address */ if (ip_addr == 0xffffffff || ip_addr == broadcast_addr) { /* return Ethernet broadcast address */ diff --git a/slirp/slirp.c b/slirp/slirp.c index 3fb48a4..00f4eb5 100644 --- a/slirp/slirp.c +++ b/slirp/slirp.c @@ -778,6 +778,11 @@ int if_encap(Slirp *slirp, struct mbuf *ifm) return 1; } + if (iph->ip_dst.s_addr == 0) { + /* 0.0.0.0 can not be a destination address, something went wrong, + * avoid making it worse */ + return 1; + } if (!arp_table_search(slirp, iph->ip_dst.s_addr, ethaddr)) { uint8_t arp_req[ETH_HLEN + sizeof(struct arphdr)]; struct ethhdr *reh = (struct ethhdr *)arp_req;