From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:58864) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WuxsC-0003Aq-6v for qemu-devel@nongnu.org; Thu, 12 Jun 2014 01:48:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Wuxs6-0007P8-PG for qemu-devel@nongnu.org; Thu, 12 Jun 2014 01:48:28 -0400 Message-ID: <53993F24.5040305@siemens.com> Date: Thu, 12 Jun 2014 07:48:20 +0200 From: Jan Kiszka MIME-Version: 1.0 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> <20140514011309.GY6302@type.youpi.perso.aquilenet.fr> <20140514012225.GA21829@hostname> <20140527231002.GB3396@toto> In-Reply-To: <20140527231002.GB3396@toto> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [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: "Edgar E. Iglesias" , Samuel Thibault Cc: qemu-devel@nongnu.org On 2014-05-28 01:10, Edgar E. Iglesias wrote: > On Wed, May 14, 2014 at 01:22:25AM +0000, Edgar E. Iglesias wrote: >> On Wed, May 14, 2014 at 03:13:09AM +0200, Samuel Thibault wrote: >>> 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 >> >> Reviewed-by: Edgar E. Iglesias > > Ping Thanks for merging! Jan > > > >> >>> --- >>> >>> 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; >>> -- Siemens AG, Corporate Technology, CT RTC ITP SES-DE Corporate Competence Center Embedded Linux