Date: Mon, 16 Aug 2021 14:04:06 -0500 From: Eric Blake <eblake@...hat.com> To: oss-security@...ts.openwall.com Subject: Re: STARTTLS vulnerabilities On Wed, Aug 11, 2021 at 06:02:35PM +0200, Hanno Böck wrote: > On Wed, 11 Aug 2021 10:31:58 -0500 > Eric Blake <eblake@...hat.com> wrote: > > > Not mentioned in that list was ndb, but as far as I can tell, that > > project has already documented the ramifications of opportunistic > > encryption as being a security risk, and all known implementations > > (both servers and clients) with TLS support have a mode of execution > > that ensures the connection is dropped if a downgrade attack is > > attempted: > > I should point out that our research is not on simple downgrade attacks. > These are kinda obvious by the design of STARTTLS if you implement it > in an opportunistic way. > > The buffering vulnerabilities we found are in STARTTLS implementations > that have the expectation to enforce a secure connection, but suffer > from various vulnerabilities in the implementation. Thank you for persisting. As a result, I have found a security bug in nbdkit, which improperly cached the result of NBD_OPT_STRUCTURED_REPLY from a plaintext MitM attacker prior to acting on NBD_OPT_STARTTLS, to the potential confusion of a client that does not expect structured replies. I will follow up again when I have a CVE number. https://listman.redhat.com/archives/libguestfs/2021-August/msg00077.html -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.