oss-sec mailing list archives
Re: STARTTLS vulnerabilities
From: Eric Blake <eblake () redhat com>
Date: Mon, 16 Aug 2021 14:04:06 -0500
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 () redhat 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
Current thread:
- STARTTLS vulnerabilities Hanno Böck (Aug 10)
- Re: STARTTLS vulnerabilities Guido Berhoerster (Aug 10)
- Re: STARTTLS vulnerabilities Hanno Böck (Aug 10)
- Re: STARTTLS vulnerabilities Eric Blake (Aug 11)
- Re: STARTTLS vulnerabilities Hanno Böck (Aug 11)
- Re: STARTTLS vulnerabilities Eric Blake (Aug 16)
- Re: STARTTLS vulnerabilities Eric Blake (Aug 18)
- Re: STARTTLS vulnerabilities Hanno Böck (Aug 10)
- Re: STARTTLS vulnerabilities Guido Berhoerster (Aug 10)
- Re: STARTTLS vulnerabilities Hanno Böck (Aug 11)
- Re: STARTTLS vulnerabilities Matthew Wild (Aug 11)