netlink: fix IP length check (SECURITY)

This would erroneously abort on some very short packets.

This is a DoS vulnerability, exposed to internal sites only.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

diff --git a/debian/changelog b/debian/changelog
index fe6caaeac517d982ee5994fe1b554c1bf9a50db2..46645f46732c547b86ad13f7508574e2b44cc410 100644 (file)
--- a/debian/changelog
+++ b/debian/changelog
@@ -9,6 +9,7 @@ secnet (0.3.1~~unstable) unstable; urgency=low
   * SECURITY: Fixes to MTU and fragmentation handling.
   * SECURITY: Correctly set "unused" ICMP header field.
   * Do not send ICMP errors in response to unknown incoming ICMP.
+  * SECURITY: Fix IP length check not to crash on very short packets.
 
  --
 

diff --git a/netlink.c b/netlink.c
index 2c3d12d4302b00aea1a59d44dbdd3ca130a532fc..787f4eb7e3c3ef8263d67344bdf831ebfdc6744f 100644 (file)
--- a/netlink.c
+++ b/netlink.c
@@ -831,7 +831,7 @@ static void netlink_incoming(struct netlink *st, struct netlink_client *client,
        BUF_FREE(buf);
        return;
     }
-    assert(buf->size >= (int)sizeof(struct icmphdr));
+    assert(buf->size >= (int)sizeof(struct iphdr));
     iph=(struct iphdr *)buf->start;
 
     source=ntohl(iph->saddr);