Hi Paul, Thank you for the follow-up.
Please see inline. Cheers, Med > -----Message d'origine----- > De : Paul Wouters <[email protected]> > Envoyé : dimanche 7 mai 2023 21:44 > À : BOUCADAIR Mohamed INNOV/NET <[email protected]> > Cc : Paul Wouters <[email protected]>; The IESG > <[email protected]>; [email protected]; ipsecme- > [email protected]; [email protected]; [email protected] > Objet : Re: [IPsec] Paul Wouters' Discuss on draft-ietf-ipsecme- > add-ike-11: (with DISCUSS and COMMENT) > > On Tue, 25 Apr 2023, [email protected] wrote: > ... > >> #3 Security Considerations > >> > >> The initiator may trust the encrypted DNS resolvers > supplied > >> by > >> means of IKEv2 from a trusted responder more than the > locally > >> provided DNS resolvers, especially in the case of > connecting > >> to unknown or untrusted networks (e.g., coffee shops or > hotel > >> networks). > >> > >> This does not seem to be a "Security Consideration". > >> Also, before this draft, receiving an (unencrypted) DNS server > >> supplied by IKEv2 would also be more trusted. In general, VPN > clients > >> trust the "VPN provided nameserver" more than the local network > one, > >> irrespective of transport encryption. Perhaps this sentence can > just > >> be deleted? > >> > > > > [Med] The intent of the text is to remind the precedence of IKE > supplied data over local supplied resolvers (even if those are > encrypted resolvers). > > Nothing this draft does changs that from before. I still don't > think it adds anything and in the case of split vpn is not > entirely true either. But it is not my hill to die on. > [Med] OK, removed that sentence. > > I do not understand the point that > >> A.2 is > >> trying to make? > >> > > > > [Med] In addition to the answer from Valery, another point of > this appendix is that some app may not fall back to Do53. > > I still do not understand. I doubt you can talk about what VPN > providers "expect". > > > >> Similarly, I don't understand Appendix A.3. The VPN service is > not > >> involved in "allowing" an application to send traffic through > the > >> tunnel. > > > > [Med] This is not what the text says. > > > >> It is the > >> VPN client that decided whether or not to send its traffic > through > >> the tunnel or not. Also VPNs typically are configured to be > either > >> split- tunnel or not. > > > > [Med] The text focuses on the case of split-tunnel VPN > configuration. > > > >> This can be, be hardly ever is, dynamic. > > > > [Med] The text does not say that. > > > > I don't understand what > >> A.3 is trying > >> to convey as example use related to the encrypted dns > capability of > >> the document. > >> > > > > [Med] This is to provide some background to motivate the > discussion about INTERNAL_DNS_DOMAIN in Section 4. > > If the section is about setting or not setting INTERNAL_DNS_DOMAIN > to > certain values, then it should do so. > > I still don't think A2 or A3 provides anything useful to the > document. > [Med] We removed A1/A2/A3. > >> Which explains one of the number "1"s in the Figure which is > >> otherwise > >> unreferenced. > > The idea here is that the other "1" should also be described here. > [Med] That other "1" is about the address count. This is why we are referring to an "address" not "addresses". Made this change "s/Its IPv6 address (2001:db8:99:88:77:66:55:44)/Its single IPv6 address (2001:db8:99:88:77:66:55:44)". > >> The placement of "AliasMode" confuses me. It appears as part of > >> the > >> Service Priority as a field name, but it is not a mode or value > of > >> that. Perhaps the text should be moved somewhat down, after the > >> listing od fields? (It is also somewhat confusing in the > reference > >> document I-D.ietf-dnsop-svcb-https. > >> > > > > [Med] svcb says "SvcPriority is a number in the range 0-65535". > We have that text there to explain why 0 is not allowed. I suggest > to leave the text there. Thanks. > > Then make it part of the previous paragraph so it is clear what > value > is talked about [Med] OK. , eg: > > CURRENT: > > Service Priority (2 octets) - The priority of this attribute > compared to other ENCDNS_IP* instances. This 16-bit unsigned > integer is interpreted following the rules specified in > Section > 2.4.1 of [I-D.ietf-dnsop-svcb-https]. > > AliasMode (Section 2.4.2 of [I-D.ietf-dnsop-svcb-https]) is > not > supported because such a mode will trigger additional Do53 > queries > while the data can be supplied directly in the IKE response. > As > such, this field MUST NOT be set to 0. > > NEW: > > Service Priority (2 octets) - The priority of this attribute > compared to other ENCDNS_IP* instances. This 16-bit unsigned > integer is interpreted following the rules specified in > Section > 2.4.1 of [I-D.ietf-dnsop-svcb-https]. As AliasMode (Section > 2.4.2 > of [I-D.ietf-dnsop-svcb-https]) is not supported, this field > MUST NOT be set to 0. > > > > >> Note that, VPN clients might have code that specifically > prohibits > >> the > >> use of DNS servers on IP addresses that are not covered by the > VPN > >> tunnel. > > Thanks for adding a warning note about this. > [Med] The following comments do not apply anymore as we removed the appendices. > >> I also have some concern with the word plausible, as that seems > to > >> only take > >> encryption into account and not redirection or privacy concerns > >> towards > >> the encrypted DNS server, or what could be monitored from an > >> adversary > >> seeing the encrypted DNS stream not protected by the VPN to a > DNS > >> server. > > > > [Med] These privacy concerns fall under this part of the > security considerations "the use of encrypted DNS does not reduce > the data available in the DNS resolver". > > That's not entirely true as there is a connection between what to > trust more, the local network or the VPN. You always seem to > assume > the VPN is more trustworthy (from an encryption and privacy point > of > view) which does not take into account other views. Again, this is > not my hill to die on, but I find the text punting to a non-VPN > encrypted DNS case not really matching what is required in this > document's security and privacy considerations. > > >> This example does not make it clear if the encrypted DNS > resolver > >> can be > >> used for all DNS or not. > > > > [Med] I guess you are referring to the example in A.1. Isn't > this explicit in this text right before the one you quoted: " For > both split- and non-split-tunnel configurations, the use of > encrypted DNS instead of Do53 provides privacy and integrity > protection ..."? > > No it does not. In a split-tunnel, it could be that only DNS > lookups for > the internal domains are allowed. Or it could be that ALL DNS > lookups > are allowed, even for non-enterprise use cases. But this is not > signaled > in any way AFAIK. The extreme case is a VPN service whose only > supported > traffic is DNS (eg think ExpressVPN SmartDNS). It is a "split > tunnel" > but it is meant to get all DNS traffic. > > > > It appears to say there is a limitation > >> to only > >> use it for internal-only domain names. I do not think such a > >> protocol > >> limitation should be implied by this example? > > So the problem is your clarifying text in split/no-split implies a > protocol feature that is not actually part of the defined > protocol. > ("split tunnel means only send DNS for INTERNAL_DNS_DOMAINS") > > Is "." a valid INTERNAL_DNS_DOMAINS ? > > Paul _________________________________________________________________________________________________________________________ Ce message et ses pieces jointes peuvent contenir des informations confidentielles ou privilegiees et ne doivent donc pas etre diffuses, exploites ou copies sans autorisation. 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