Re: [ietf-dkim] DKIM Japan has been set up
We really need a FAQ for this group. >> Simply publishing an ADSP record does not change this fact. ADSP can >> perhaps be used productively for specific signers and verifiers, but it >> does not work for all legitimate scenarios. >> > What does work for all legitimate scenarios? Short answer: nothing. Slightly longer answer: the problem with ADSP is that, based on my limited but I think credible statistics, most people who publish ADSP don't know what it means, so blindly following ADSP advice from random domains is more likely to discard real mail than phishes. There certainly are some domains that sign all their mail, don't mix individual with transactional mail, and are phish targets. Paypal.com is the standard example. Competently maintained lists of those domains would provide useful advice for discarding likely phishes. Back in June I wrote draft-levine-dbr-00, which describes Denounce-By-Reference, a simple way to publish such lists in the DNS. Anyone want to move it along? Regards, John Levine, jo...@iecc.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. http://jl.ly ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] A comprehensive DKIM verification specification will not violate protocol layers.
Murray argued singleton header checks to qualify DKIM signatures violates protocol layering. SMTP messages are exchanged in two parts, a header and a body section. The header section should conform with RFC5322, and the body should conform with RFC2045. RFC2047 and RFC2231 define header encoding for non US-ASCII repertoire using US-ASCII, and RFC1652 relaxes restrictions on the body. Section 6.4 of RFC5321 makes it clear that non-compliance with RFC5322 occurs, and that there is no consensus whether to reject, repair, or accept such messages. RFC1847 (Security Multiparts for MIME), RFC4880 (PGP), or RFC3851 (S/MIME) authenticates the source and integrity of the message body, whereas DKIM retains the integrity of trusted portions of the header section, specifically the From header field, and perhaps others. Whenever message acceptance is based upon valid DKIM signatures by trusted domains, defeating trivial exploitation of DKIM's bottom-up header selection requires exclusion of multiple singleton header fields from being considered having valid DKIM signatures. Otherwise, this would permit inappropriate header fields to be conveyed using top-down selections. It is imperative that DKIM's verification process defeat such exploits, since DKIM does not assume applications conveying the header section is DKIM aware. Expecting consumers of DKIM results to re-evaluate the header section eliminates DKIM's value proposition. Recommending subsequent checks for multiple singleton headers represents poor protocol layering, since this would expect consumers of DKIM results to recheck the header section being associated with a DKIM domain. -Doug ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] DKIM Japan has been set up
On 11/22/10 9:25 AM, Steve Atkins wrote: > ... > > But if you're trying to stop mail that's being sent by a bad > actor... give up on this approach, as it's trivial to add a "fake" > DKIM header that will not authenticate. > > Also, it may discard quite a bit > of legitimate email, if any of your users subscribe to mailing > lists (some mailing list managers are likely to strip out > DKIM headers in the cases where they know they'll invalidate > them). Agreed. DKIM does not offer a comprehensive method to qualify the source of a message. Extensions, such as the TPA-Label scheme, could extend signing policy to include other authentication and authorization methods and retain delivery integrity. ADSP using just DKIM is likely to cause a significant loss of legitimate email, especially when DISCARDABLE is asserted. -Doug ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] DKIM Japan has been set up
On Monday, November 22, 2010 01:37:13 pm Dave CROCKER wrote: > On 11/21/2010 6:43 PM, Tsuneki Ohnishi wrote: > > But there is a small problem. It is rather polical. > > We have a telecommunication law that allows ISPs to discard > > forged email, but our Ministry so far does not acknowledge > > that failure of DKIM verification immediately equals to > > forgery, because there could be other reasons to fail. > > There are technical and operational reasons that can cause legitimate mail > that was originally signed with a legitimate DKIM signature, to fail to > verify. > > The fact that a signer signs all their mail does not mean that all their > mail will arrive with a valid signature. > > Simply publishing an ADSP record does not change this fact. ADSP can > perhaps be used productively for specific signers and verifiers, but it > does not work for all legitimate scenarios. > What does work for all legitimate scenarios? Scott K ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] DKIM Japan has been set up
On 11/21/2010 6:43 PM, Tsuneki Ohnishi wrote: > But there is a small problem. It is rather polical. > We have a telecommunication law that allows ISPs to discard > forged email, but our Ministry so far does not acknowledge > that failure of DKIM verification immediately equals to > forgery, because there could be other reasons to fail. There are technical and operational reasons that can cause legitimate mail that was originally signed with a legitimate DKIM signature, to fail to verify. The fact that a signer signs all their mail does not mean that all their mail will arrive with a valid signature. Simply publishing an ADSP record does not change this fact. ADSP can perhaps be used productively for specific signers and verifiers, but it does not work for all legitimate scenarios. d/ -- Dave Crocker Brandenburg InternetWorking bbiw.net ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] DKIM Japan has been set up
On Nov 21, 2010, at 6:43 PM, Tsuneki Ohnishi wrote: > > Thanks, Bill, Mark and Byung-Hee for the warm welcome. > > Yes, we gotta start something somewhere and glad to > let you know that we are staring something here. > If possible, let's work together for the spread out > in eastern asia, Byung-Hee. > > Well, let me give you the first feedback of what's > been discussed at the point of implementation here, > and I would like to ask your opinions. > > Here is our stuation. Members of dkim.jp so far circulate > somewhat like 30% of domestic emails and a lot more forged > emails coming from overseas, especially forged @yahoo.co.jp > and @rakuten.co.jp. So with the initiative of those two > companies and others, we got together to get rid of those > forged emails. > > Senders in dkim.jp are committed to attach DKIM signature > withing 6 months, and possibly ready to write their ADSP > "discardable". Since we have major ISPs on our member list > and they are very willing to discard unveryfied emails, > no surprise about it :-), we are trying to inch up to the > level where all domestic emails are signed and verified. > > But there is a small problem. It is rather polical. > We have a telecommunication law that allows ISPs to discard > forged email, but our Ministry so far does not acknowledge > that failure of DKIM verification immediately equals to > forgery, because there could be other reasons to fail. That's not political, that's technical. Mail that is validly DKIM signed when it's sent may not be DKIM signed when it is received. If you discard mail that isn't DKIM signed just because you expected it to be DKIM signed, you'll end up discarding quite a lot of email. And the errors aren't likely to be terribly random, rather they'll be related to particular mail paths, so some people will see a lot of mail wrongly discarded. ADSP is better than SPF, but it's still not something anyone should consider deploying widely as a primary means of deciding to discard inbound email. > We can fight about it taking time to get through to dull > Japanese bureaucracy, but I think there is a faster way. > It is to let senders to have an option to declare that > if there is no DKIM signature at all, verifiers can discard > those messages. Then we can shut their mouths insisting > there could be other reasons. > > So, my point is that what do you think of the idea to have > an new entry in ADSP "discard-if-no-sig", which allows > senders to declare messages without DKIM signature should > be discarded? If you're just trying to stop email such as virus blowback then something simple like that will work OK, some of the time. It's more complex, and less effective, than other approaches so it's not a really good idea. But if you're trying to stop mail that's being sent by a bad actor... give up on this approach, as it's trivial to add a "fake" DKIM header that will not authenticate. Also, it may discard quite a bit of legitimate email, if any of your users subscribe to mailing lists (some mailing list managers are likely to strip out DKIM headers in the cases where they know they'll invalidate them). Cheers, Steve ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] DKIM Japan has been set up
Thanks for your comment, Hector and Alessandoro. I understand your point. First, Alessandoro, let me reply to your comment. Yes, very true, it is recipients' choice to discard messages. But in fact, that choice is lost for now because our Ministry does not allow that. My idea was to build another level of ground where the author, recipients and the Ministry can agee on, "if-no-sig then discardable". And I see your point, Hector. If we draw a line between Sig and No-sig, that would allow broken signature to be accepted. But as you poited out, bad guys still remain in legacy operation, so the line between Sig and No-sig works for the time being. I know that it is not the best way to do it, but it could be a practical step to the wider adoption. Because if that option gets valid, I am sure more authors would choose it at least here in Japan. I don't think that undermines the effectivenes of DKIM, because one can always rewrite his ADSP 'discaradable' if the bad guys start spoofing with forged signatures. Well, it's just a newbie's idea, so may be totally unacceptable. But please understand that we're heavily committed. Gotta find a way through. Tsuneki Ohnishi infomani@ Inc. On 2010/11/22, at 18:16, Alessandro Vesely wrote: > As an alternative, it is the recipients who may eventually decide they > are not interested in receiving unsigned contributions to their > inboxes, unless they have other means to identify those messages. > IMHO, such decision should be made by each recipient individually. On 2010/11/22, at 14:49, Hector Santos wrote: > Tsuneki Ohnishi wrote: > >> So, my point is that what do you think of the idea to have >> an new entry in ADSP "discard-if-no-sig", which allows >> senders to declare messages without DKIM signature should >> be discarded? >> >> If that's possible, it makes our job a lot easier and faster. > > Hi. > > You are basically asking to make a distinct difference between: > > 1) a real no signature message versus > 2) a message who's signature is broken (invalid). > > The DKIM specification says that a broken signature is the same as no > signature message. > > It is important to know the difference because if you are concern about a > Real No-Sig versus a Broken one where a Real No-SIG is discarded but a Broken > one is not, then whats to stop the Bad Guy from adding a broken signature by > design and for the sole purpose of making sure the message is now > indeterminate and you don't filter it? > > The problem with DKIM is the is the "stuff in the middle" - A real no-sig > message can be made to work, as well as when there is a valid signature. > > It the faults of the system that is challenging - what do you do with > failures and what makes it even more difficult is the specifications has > evolved to one where where any system, middle-ware or hop, can break or > remove an author domain signature without restrictions. This was done to > appease the LIST managers, 3rd party signer and the reputation market. > > IMO, I think DISCARD should cover what you want, but you have to view it as a > strong policy with no exceptions, i.e., a broken signature is just as bad as > no-signature and more importantly, no interference or 3rd party signers can > override the message author domain security expectations. > > If you allow for broken signatures to be "acceptable" partially or otherwise > in an ADSP setup, then it just confuses the intent and it potentially feeds > bad guys to give you broken signatures because that is "OK" by you. > > Right now, there is no incentive for bad guys to adapt or change. They can > remain in legacy operations (no signature) because there is no wide adoption > or foundation for DKIM policies or the handling of policy faults. > > Having a "MUST SIGN" policy widely adopted (and supported) would begin to > make a change in legacy operations. They will most likely avoid your POLICY > protected domain. But if you allow for broken ones, then they can adapt by > adding a spoofed but broken signature. > > -- > Hector Santos, CTO > http://www.santronics.com > > > > --_ 株式会社インフォマニア ≫ http://www.infomania.co.jp/ 代表取締役 大西恒樹 ≫ TEL 045-914-5304 FAX 5404 迷惑メールフィルター ≫ http://www.answre.jp/ Pizzeria マルターノ ≫ http://www.martano.jp/ twitter アカウント ≫ mjwords - ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
Re: [ietf-dkim] DKIM Japan has been set up
Hi Tsuneki, first of all, since I write, let me make my welcome-on-list explicit! On 22/Nov/10 03:43, Tsuneki Ohnishi wrote: > Senders in dkim.jp are committed to attach DKIM signature > withing 6 months, and possibly ready to write their ADSP > "discardable". Since we have major ISPs on our member list > and they are very willing to discard unveryfied emails, > no surprise about it :-), we are trying to inch up to the > level where all domestic emails are signed and verified. I hope you'll get replies more qualified than mine... FWIW, I suggest you do not use ADSP that way. > But there is a small problem. It is rather political. > We have a telecommunication law that allows ISPs to discard > forged email, but our Ministry so far does not acknowledge > that failure of DKIM verification immediately equals to > forgery, because there could be other reasons to fail. IMHO, your Ministry is correct. > We can fight about it taking time to get through to dull > Japanese bureaucracy, but I think there is a faster way. > It is to let senders to have an option to declare that > if there is no DKIM signature at all, verifiers can discard > those messages. Then we can shut their mouths insisting > there could be other reasons. As an alternative, it is the recipients who may eventually decide they are not interested in receiving unsigned contributions to their inboxes, unless they have other means to identify those messages. IMHO, such decision should be made by each recipient individually. ___ NOTE WELL: This list operates according to http://mipassoc.org/dkim/ietf-list-rules.html
