On Fri, Oct 07, 2016 at 01:41:14PM -0700, Watson Ladd wrote: > On Fri, Sep 23, 2016 at 10:47 PM, Ilari Liusvaara > <ilariliusva...@welho.com> wrote: > > > > Also, it is very likely that 0-RTT would need its own read API, because > > it is pretty unlikely that existing API could be safely retrofitted > > or even purpose-built unified API be designed that isn't just asking > > for security problems via mixing 0-RTT and 1-RTT data. > > Yes. In particular I think the TLS state machine transitions need to > be ordered with respect to the arrival and sending of data. The > challenge for a multithreaded program (yes, some programs have > multiple threads sending and receiving at once) is making this make > sense, or even a single-threaded program where the TLS stack can > change state at times not visible to the sending thread. Maybe there > is some slop here, like 0-RTT can become 1-RTT on send, but this > raises all sorts of problems for receiving. I think we need to require > separation in the API.
0-RTT can't be allowed to become 1-RTT on send (unless it is auto- retransmit, which needs to be disableable, as sometimes that just plain won't work). This impiles that the application always needs to explicitly signal the end of 0-RTT data, even just to abort sending it. > > (This is the reason one needs to be especially careful when combining > > dynamic client certificates with HTTP/2... Basically, it can not be > > done safely without coordination on application layer). > > > > One likely wants application protocol to be able to specify part of > > or the entiere request context and to extract that part in the other > > end when requesting a certificate selection. This is to allow putting > > part of coordination data into the request itself. However, this is not > > sufficient for e.g. HTTP/2 signaling, so more needs to be exchanged at > > application layer. > > > > And then upon completion of the authentication (either successful or > > explicitly rejected), signal the application with the new certificate > > chain and the context the request had. > > This is going to require major changes to APIs and to the HTTP/2 > layer. It also interacts with token binding, whee! My question then > becomes one of what we actually need: can we assume that leakage > between authentication contexts over a single session is safe because > all contexts represent the same principal, by restricting the usages, > or is this overly restrictive? Yes, it is going to reuqire such changes. And you absolutely can not assume that all contexts present the same principal. And as I said, in multiplexed protocol like HTTP/2, you need application- level coordination on top. TLS just can't do that. > When we have multiple requests and replies in flight and the > authentication state changes, things get nasty. If we think of TLS as > sending a stream of events including authentication changes to the > application, this fits the semantics of the TLS draft as I understand > them to be, but does not necessarily fit what application protocols > want. There might be a semantic mismatch here requiring reworking of > one or another part. Also, some applications presumably want the events done synchronously, so they don't move with data reads. Basically, post-handshake auth is heckuva nasty problem. -Ilari _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
