Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-29 Thread David Benjamin
On Wed, Jun 1, 2016 at 6:57 PM Eric Rescorla wrote: > On Wed, Jun 1, 2016 at 3:53 PM, David Benjamin > wrote: > >> On Wed, Jun 1, 2016 at 6:43 PM Eric Rescorla wrote: >> >>> 2% is actually pretty good, but I agree that we're going to need >>> fallback. >>> >>> I'd be fine with moving the 8 byte

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-06 Thread Martin Rex
The IMO most reasonable way forward would be to side-step the TLS version negotiation through ClientHello.client_version entirely, because of the well-known interop problems. Simply use the presence of *ANY* TLSv1.2+ TLS cipher suite in the offered list of TLS cipher suites as an indication that a

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-06 Thread Stefan Winter
Hi, > > > > I agree with Hubert. The big question is how you get the bug report to > the server operator. Automated mail to webmaster@domain_of_requested_hostname? Maybe a few thousand new mails in the operator's inbox of sorts "we have encountered a situation where your version intolerance brok

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-04 Thread Yaron Sheffer
On 02/06/16 18:16, David Benjamin wrote: On Thu, Jun 2, 2016 at 10:59 AM Viktor Dukhovni mailto:ietf-d...@dukhovni.org>> wrote: > On Jun 2, 2016, at 10:49 AM, David Benjamin mailto:david...@chromium.org>> wrote: > > I'm not sure I follow. The specification certainly spells

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread Viktor Dukhovni
> On Jun 2, 2016, at 11:16 AM, David Benjamin wrote: > > I've mused on something like that (I was the main driver behind painstakingly > removing the existing version fallback in Chrome), but I don't think > non-determinism is a good idea. Site owners need to be able to reproduce the > failur

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread David Benjamin
On Thu, Jun 2, 2016 at 11:20 AM Hubert Kario wrote: > > > Speaking of version number, does the text say that a server _MUST_ > > > accept any version higher than the one that is specified in the RFC, > > > but reply with 0x03,0x04 in case it doesn't support any future > > > version of the protoco

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread Hubert Kario
On Thursday 02 June 2016 14:49:52 David Benjamin wrote: > On Thu, Jun 2, 2016 at 6:40 AM Hubert Kario wrote: > > On Wednesday 01 June 2016 22:29:06 David Benjamin wrote: > > > In case folks hoped we could bump the ClientHello version without > > > those dreaded browser fallbacks, I have bad news.

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread David Benjamin
On Thu, Jun 2, 2016 at 10:59 AM Viktor Dukhovni wrote: > > > On Jun 2, 2016, at 10:49 AM, David Benjamin > wrote: > > > > I'm not sure I follow. The specification certainly spells out how > version negotiation is supposed to work. That hasn't stopped servers from > getting it wrong. Fundamentall

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread Viktor Dukhovni
> On Jun 2, 2016, at 10:49 AM, David Benjamin wrote: > > I'm not sure I follow. The specification certainly spells out how version > negotiation is supposed to work. That hasn't stopped servers from getting it > wrong. Fundamentally this is the sort of thing where bugs don't get noticed > unt

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread David Benjamin
On Thu, Jun 2, 2016 at 6:40 AM Hubert Kario wrote: > On Wednesday 01 June 2016 22:29:06 David Benjamin wrote: > > In case folks hoped we could bump the ClientHello version without > > those dreaded browser fallbacks, I have bad news. :-( 1.3 intolerance > > very much exists. (Maybe we should just

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-02 Thread Hubert Kario
On Wednesday 01 June 2016 22:29:06 David Benjamin wrote: > In case folks hoped we could bump the ClientHello version without > those dreaded browser fallbacks, I have bad news. :-( 1.3 intolerance > very much exists. (Maybe we should just give up on > ClientHello.version and use an extension? Exten

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-01 Thread Martin Thomson
On 2 June 2016 at 08:56, Eric Rescorla wrote: >> (Although, do we actually get the stronger protection if the client >> accepts plain RSA key exchange? I've never been very clear on that. >> Realistically, clients will be accepting plain RSA for a long while.) > > > Yes, that's correct. I don't be

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-01 Thread Eric Rescorla
On Wed, Jun 1, 2016 at 3:53 PM, David Benjamin wrote: > On Wed, Jun 1, 2016 at 6:43 PM Eric Rescorla wrote: > >> 2% is actually pretty good, but I agree that we're going to need fallback. >> >> I'd be fine with moving the 8 bytes to the end, but I wonder if it would >> be better to >> instead ha

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-01 Thread David Benjamin
On Wed, Jun 1, 2016 at 6:43 PM Eric Rescorla wrote: > 2% is actually pretty good, but I agree that we're going to need fallback. > > I'd be fine with moving the 8 bytes to the end, but I wonder if it would > be better to > instead have the *client* indicate its max version and the server check. >

Re: [TLS] Downgrade protection, fallbacks, and server time

2016-06-01 Thread Eric Rescorla
2% is actually pretty good, but I agree that we're going to need fallback. I'd be fine with moving the 8 bytes to the end, but I wonder if it would be better to instead have the *client* indicate its max version and the server check. That would have the advantage that it would leave more of the se

[TLS] Downgrade protection, fallbacks, and server time

2016-06-01 Thread David Benjamin
In case folks hoped we could bump the ClientHello version without those dreaded browser fallbacks, I have bad news. :-( 1.3 intolerance very much exists. (Maybe we should just give up on ClientHello.version and use an extension? Extensions have rusted less.) I picked a large list of top sites and