Date: Fri, 17 Oct 2014 17:28:56 +0100 From: Vitor Ventura <ventura.vitor@...il.com> To: oss-security@...ts.openwall.com Subject: Re: Connected UDP sockets and kernel queuing (CVE-2014-6512) Hello, I was thinking if this might open a door for a reflected amplification attack. By your description this shouldn't be possible because the application shouldn't be waiting for any packets after the close of he socket, nevertheless a possible vector of attack seems to be open. The attack vector could be achieved by the creation of a "connection" and closure by a side channel and then exploit the time window created. These side channels are common on gaming servers and streaming. I will try to test it. Em 17/10/2014 16:03, "Florian Weimer" <fweimer@...hat.com> escreveu: > I noticed a potential issue with connected UDP sockets and the kernel > kernel per-socket packet queue, potentially leading to IP spoofing > vulnerabilities in the sense that the application thinks the packet came > from host A, but it really came from host B: > > <https://bugzilla.redhat.com/show_bug.cgi?id=1071210> > > OpenJDK is particularly exposed because DatagramSocket.disconnect() calls > connect(2) with AF_UNSPEC (or a NULL socket address on some systems) to > disconnect sockets, which is a rarely used feature of the BSD sockets API. > OpenJDK ensures that these disconnected sockets remain bound to a port, so > it was possible to enqueue packets whose source address will not be > checked, without even having a tight race to win. > > We thought briefly about fixing this in the kernel, but thought better of > it because of backwards compatibility concerns (and we would have to patch > OpenJDK nevertheless). The OpenJDK fix simply checks the source address of > incoming packets. Oracle's fix has an optimization that drops this > additional filter after the maximum amount of pending packets has been > consumed from the socket; my patch moved the filter to native code instead > and applied it to every packet on a connected socket. I think both > approaches are valid. > > I'm sharing this with a wider audience because in theory, other UDP-based > services could be affected, although I didn't spot any when I looked at > this prior to disclosure. > > -- > Florian Weimer / Red Hat Product Security >
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