>Neither DANE nor STS provide message origin authenticity, >these are hop-by-hop security mechanisms that authenticate >only the receiving system, not the sender.
What will be the provision for the origin authenticity then ? How to authenticate the sender ? On Wed, Jan 3, 2018 at 1:30 AM, <[email protected]> wrote: > Send Uta mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.ietf.org/mailman/listinfo/uta > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Uta digest..." > > Today's Topics: > > 1. Question Regarding DANE and MTA-STS (Ranjana Mukhia) > 2. Re: Question Regarding DANE and MTA-STS (Viktor Dukhovni) > > > ---------- Forwarded message ---------- > From: Ranjana Mukhia <[email protected]> > To: [email protected] > Cc: > Bcc: > Date: Tue, 2 Jan 2018 17:33:25 +0530 > Subject: [Uta] Question Regarding DANE and MTA-STS > Hello All, > > This related to the below part of the latest uta-mta-sts-13 draft > > >The primary motivation of MTA-STS is to provide a mechanism for domains > to ensure transport >security even when deploying DNSSEC is undesirable or > impractical. However, MTA-STS is >designed not to interfere with DANE > deployments when the two overlap; in particular, senders who >implement > MTA-STS validation MUST NOT allow a "valid" or "testing"-only MTA-STS > validation to >override a failing DANE validation. > > My questions are > > 1.If we are going to implement MTA-STS then, whether it should be > compulsorily used with DANE ?If Not why ? as we have faced many problems > related to CA's in past. > > 2.Whether MTA-STS is fully capable of securing email transmission without > the help of any other technologies like DKIM,SPF,DMARC or DANE ? > > > Thanks > > Regards > > Ranjana > > > ---------- Forwarded message ---------- > From: Viktor Dukhovni <[email protected]> > To: [email protected] > Cc: > Bcc: > Date: Tue, 2 Jan 2018 11:35:43 -0500 > Subject: Re: [Uta] Question Regarding DANE and MTA-STS > > > > On Jan 2, 2018, at 7:03 AM, Ranjana Mukhia <[email protected]> > wrote: > > > > 1.If we are going to implement MTA-STS then, whether it should be > compulsorily > > used with DANE? > > Nothing is compulsory. The standards will tell you how to use STS, but > cannot compel its use. Implementations that strive to avoid downgrade > and MiTM attacks should generally not permit weaker policies to downgrade > concurrent stronger policies. Therefore, if: > > 1. The domain's MX records are DNSSEC validated, and > > 2. The MX hostname to which a connection is established > is also in a signed zone (its A/AAAA records are signed, > or result from a CNAME alias and the initial CNAME > from the MX hostname is secure), and > > 3. Secure TLSA records are published at the domain obtained > by prefixing _<port>._tcp. (port is typically "25") to > either: > > a. The secure full CNAME expansion of the MX hostname, > or else if not secure, or, if no TLSA records present > there (NXDomain or NODATA, abort use of MX host on > TLSA lookup failure), at > b. The original MX hostname (abort use of MX host on > TLSA lookup failure). > > > then, a sender that supports and enables DANE should typically ignore STS. > Requiring both when both are published feels too fragile to me, and > requiring > either downgrades DANE security. > > On the other hand, some domains might have only a partial DANE > implementation, where some MX hosts have TLSA records and others > do not. In that case, when a given MX host is not secured with > DANE, but the domain has STS policy, it makes sense to apply STS > when delivering via that MX host (assuming STS is supported and > enabled at the sender). > > > 2.Whether MTA-STS is fully capable of securing email transmission > > without the help of any other technologies like DKIM,SPF,DMARC or DANE? > > You have not defined "securing email transmission". STS and DANE > are both designed to authenticate the nexthop SMTP destination to > the sending MTA, and to transmit the message envelope and body over > a TLS channel that provides integrity and confidentiality of the > transmitted data. > > STS does this subject to the integrity of WebPKI certificate > issuance and potential downgrade on first-contact (and possibly > after previous cached policy has expired if email flow to the > nexthop domain is infrequent). Given that DV certificates are > issued based on "domain control", the WebPKI can be at most as > secure as the DNS. > > DANE does this subject to the integrity of DNSSEC for the > domain and its ancestor domains up to the trust-anchor used > (typically the DNS root zone keys). DANE does not have a > first-contact security gap. > > Neither DANE nor STS provide message origin authenticity, > these are hop-by-hop security mechanisms that authenticate > only the receiving system, not the sender. > > -- > Viktor. > > > > _______________________________________________ > Uta mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/uta > >
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