Re: [TLS] renego, patricide, putting out to stud, etc.
Michael D'Errico <mike-list@pobox.com> Fri, 01 January 2010 01:17 UTC
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Date: Thu, 31 Dec 2009 17:19:09 -0800
From: Michael D'Errico <mike-list@pobox.com>
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Subject: Re: [TLS] renego, patricide, putting out to stud, etc.
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It's not really parent-child, it is actually more like cloning and metamorphosis. Mike Ravi Ganesan wrote: > >> OK, but that's a fairly complicated way of describing the semantics. > Also > >> you used the term "session" to describe the nodes: > > It is somewhat complicated, but I think it is the minimum needed. I just > feel getting into connections, sessions, channels, all words which carry > unintended baggage, does not seem to be working. Just consider if I am > the Client and you are the Server, and we open a thingy (call it A) > communicate for a while. Use A to spawn two more thingys in parallel > using abbreviated handshakes (B and C). Then do a renego using full > handshake on B (gives us D). D then spawns two more thingys using > abbreviated handshakes (E and F). F happens to do a renego using a full > handshakes to spawn G. In the meanwhile we do a full handshake renego on > A, and then.... you are asked to explain in retrospect exactly what on > earth happened. If you use my approach of tagging each of the nodes > A,B,C,D,E, F and G with the six variables (session-id, master-secret, > client-random, server-random, auth knowledge and RI), and show which of > them change from parent to child, you will end up with a compact tree > with the properties I mentioned. > > But of course I am biased, I feel it is limiting to use words that limit > TLS to "sockets" or "connections", needlessly. For instance what does > a connection mean if the binding is not TCP? e.g. EKR's work on UDP, > mine on HTTP, Gajek et al on SOAP). > This bias aside, however, I think the tree with its state transitions is > useful even for regular TLS. Especially since we are keeping chained > hashes around. > > > Message: 1 > Date: Wed, 30 Dec 2009 16:46:49 -0800 > From: Ravi Ganesan <ravi@findravi.com <mailto:ravi@findravi.com>> > Subject: Re: [TLS] sessions, contexts, etc. > To: tls@ietf.org <mailto:tls@ietf.org> > Message-ID: > <3561bdcc0912301646p65923143t1b138fb17b75d9@mail.gmail.com > <mailto:3561bdcc0912301646p65923143t1b138fb17b75d9@mail.gmail.com>> > Content-Type: text/plain; charset="utf-8" > > Does something along these lines work as a pedagogical device? Nodes > characterized by the parameters of relevance. A root node, three > types of > ways to spawn a child node. What a child inherits from parent, etc... > > At the end of a TLS handshake, the Client and the Server share six key > pieces of information: > (i) a session-id /*Public information */ > (ii) a shared master-secret /*Secret. Known only to Client and Server */ > (iii) the client-random and /* May be public or secret */ > (iv) the server-random. /*May be public or secret*/ > (v) authentication knowledge /* Namely, the Client MAY know that is has > authenticated the Server (in practice this almost always is true). The > Server MAY know that it has authenticated the Client (relatively rare in > practice, but an important sub-category). > (vi) renegotiation-information /*The newly introduced RI field at > the end of > the handshake. */ > > > When the Client and a Server share NONE of the above six pieces of > data, > the Client will typically initiate a completely fresh session using > the FULL > handshake. Such a session is called a ROOT session. A Client and a > Server > who have completed a ROOT session can engage in further handshakes > to create > new sessions, which in turn can create further sessions. Treating each > session as a node in a graph we can get a tree rooted at the ROOT. > > Each node can spawn a child node using three different techniques as > follows: > > i) A node can create a child-node by performing an abbreviated > handshake. > Such an abbreviated-child inherits the session-id, the shared > master-secret > and the authentication-knowledge, from its parent (these CANNOT > change). It > gets new client-random, server-random and starts afresh with > renegotiation-information. This technique of spawning a child node is > usually used for efficiency considerations (abbrv. handshake > requires no PKI > operations, which is why it cannot be used to update > authentication-knowledge of the other end either). The creation of > such a > child-node does NOT result in the previous node becoming inactive. > > ii) A node can create a child node by performing renegotiation, > followed by > a full handshake. Such a full-renego-child, starts afresh with new > values > for all of the first five parameters. The only parameter which keeps > it tied > to this tree is the renegotiation-information, which is derived from the > handshake and the parent-node's renegotiation-information. The primary > use-case for this technique is to update authentication-knowledge > of the > Server (i.e. does it know who the Client is?). The creation of such > a child > node means the parent node can no longer be used. > > iii) A node can create a child node by performing renegotiation > followed by > an abbreviated handshake. Such a abbrv-renego-child inherits the > session-id, > shared-master-secret and authentication-information of its parent. > There is > a new client-random and server-random, and as in a > full-renego-child, the > renegotiation-information is derived from the handshake and the the > renegotiation-information of its parent. I do not know why this > use-case > exists; the encryption/hashing keys change but it is questionable if > that > adds any protection. The creation of such a child node means the > parent node > can no longer be used. > > Observe that each of the different child nodes can give birth to any > of the > other three types of children. > > > ------------------------------------------------------------------------ > > _______________________________________________ > TLS mailing list > TLS@ietf.org > https://www.ietf.org/mailman/listinfo/tls
- Re: [TLS] renego, patricide, putting out to stud,… David-Sarah Hopwood
- Re: [TLS] renego, patricide, putting out to stud,… Ravi Ganesan
- [TLS] renego, patricide, putting out to stud, etc. Ravi Ganesan
- Re: [TLS] renego, patricide, putting out to stud,… Michael D'Errico
- Re: [TLS] renego, patricide, putting out to stud,… Marsh Ray
- [TLS] Fw: renego, patricide, putting out to stud,… tom.petch