Picking up on the one point about the asymmetry of TLS, I agree that the crypto is symmetric once the master key has been created. The weakness is the underlying assumption, at least when SSL started, that there is a human sitting at the client end who can respond to messages about the certificate being invalid (something my MUA offers me at least once a day for the past week, for reasons I cannot divine) or any other hiccup in the process prior to the establishment of the master key You can argue that almost all users haven't a clue about certificates and almost all systems are configured by default to suppress any such messages, but the technology is there for those who want adequate security, at least when there is a human at the TLS client.
What I worry about with such as PCE is getting an adequate check of the authentication, with a focus on how to validate certificates. As I said before, I have been involved with this with I-Ds on SNMP and Netconf and have seen much arise, even at the IESG stage, with some comments that to me seem misplaced; but as they are DISCUSS, they have to be taken seriously. So I value the early intervention of the Security Directorate to try and fix such issues sooner, and so cheaper, rather than later. Tom Petch ----- Original Message ----- From: "DIEGO LOPEZ GARCIA" <[email protected]> To: <[email protected]> Sent: Monday, November 09, 2015 8:23 AM Subject: Re: [Pce] PCE WG Last Call - draft-ietf-pce-pceps-04 > Hi Tom, > > Thanks for the review. We will update the draft text addressing your comments and those we received form Cyril. Some notes inline below > > On 4 Nov 2015, at 19:55 , t.p. <[email protected]<mailto:[email protected]>> wrote: > > s.3 At first, I was unsure whether or not both parties sent a StartTLS. > "The StartTLS message is a PCEP message sent by a PCC to a PCE and by > a PCE to a PCC " suggests both > "Once the TCP connection has been successfully established, the first > message sent by the PCC to the PCE or by the PCE to the PCC MUST be > a > StartTLS message " suggests only one. > Section 3.3 makes it clearer that both send it. This is fine but I am > unaware of any other protocol where this happens so I would suggest > /or/and/ in that second sentence and expanding the earlier sentence > OLD > 2. Initiating the TLS Procedures by the StartTLS message. > NEW > 2. Initiating the TLS Procedures by the StartTLS message from PCE to > PCC and from PCC to PCE. > > DRL> You are right in the ambiguity and we will correct it as you suggest. > > I focus on this because I was also looking to see which became TLS > Client. TLS is asymmetric, designed to authenticate a (HTTP) server to > a client. Netconf (and SNMP), which I know better, struggled with this > because the key for Netconf is to authenticate the client to the server, > which TLS does not do so well. Posts on the TLS list suggest that there > are very few implementations of TLS client authentication, rather > something else is done once the secure channel has been established. > > DRL> I’d not say there are few implementations, but that client authentication is not commonly employed, especially in the web environment where other mechanisms are preferred, like using a TLS connection based on server authentication to retrieve password credentials from the user… As far as I can tell, TLS is only asymmetric in this requirement for authentication of both peers, as the crypto exchanges become essentially equal if client authentication is required. > > So, do you care who is TLS client and who TLS server? It will be > interesting to see a security review of this. > > DRL> What we had in mind was that the natural approach taking into account the structure of PCEP was to have the PCC peer acting as client and the PCE acting as server. We’ll include a requirement in section 3.2 on this. I do not see any security issue here, but we could certainly request the UTA WG to make a review. I’d say this completely falls under their area of interest. > > In passing, RFC7465 prohibits RC4 with TLS so I would think it unlikely > that > "SHOULD support TLS_RSA_WITH_RC4_128_SHA" will be acceptable. > > DRL> Good catch. It will ve deleted in the coming version. > > Be goode, > > -- > "Esta vez no fallaremos, Doctor Infierno" > > Dr Diego R. Lopez > Telefonica I+D > http://people.tid.es/diego.lopez/ > > e-mail: [email protected] > Tel: +34 913 129 041 > Mobile: +34 682 051 091 > ---------------------------------- > > > ________________________________ > > Este mensaje y sus adjuntos se dirigen exclusivamente a su destinatario, puede contener información privilegiada o confidencial y es para uso exclusivo de la persona o entidad de destino. 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Please immediately reply to the sender that you have received this communication in error and then delete it. > > Esta mensagem e seus anexos se dirigem exclusivamente ao seu destinatário, pode conter informação privilegiada ou confidencial e é para uso exclusivo da pessoa ou entidade de destino. Se não é vossa senhoria o destinatário indicado, fica notificado de que a leitura, utilização, divulgação e/ou cópia sem autorização pode estar proibida em virtude da legislação vigente. Se recebeu esta mensagem por erro, rogamos-lhe que nos o comunique imediatamente por esta mesma via e proceda a sua destruição > _______________________________________________ Pce mailing list [email protected] https://www.ietf.org/mailman/listinfo/pce
