On Thu, Jul 31, 2014 at 05:15:58PM +0200, Ondrej Mikle wrote: > On 07/31/2014 09:54 AM, Kurt Roeckx wrote: > > On 2014-07-31 01:29, Ondrej Mikle wrote: > >> I should probably add that a MitM attacker like an ISP can generally > >> tamper with > >> certificate chains sent in TLS handshake anyway, but AIA fetching would > >> allow an > >> adversary more hops away on a different continent to tamper with the > >> connection. > > > > How would an ISP tamper with the certificates send in TLS without TLS > > giving an > > error that the packets were tampered with? > > > > I understand that it's possible with SSL 3.0 but not with TLS 1.0. > > IIRC the Server Certificate message in hanshake protocol is not authenticated. > Thus one could exchange an intermediate certificate(s) for a different one > having identical public key etc, but for example different validity period or > extensions (if such certificate exists, but CA reissue intermediates).
As far as I understand, the Finished message will detect that the certificates have been changed. You might be validating some other chain first, but you'll end up with an error. Kurt _______________________________________________ dev-security-policy mailing list [email protected] https://lists.mozilla.org/listinfo/dev-security-policy
