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 <samuel.thiba...@ens-lyon.org>
---
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;
