Re: [Dcrup] Is there anything this WG wants to do not yet in draft-ietf-dcrup-dkim-crypto-01 ?

"John R. Levine" <johnl@iecc.com> Tue, 20 June 2017 20:01 UTC

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Date: Tue, 20 Jun 2017 16:01:18 -0400
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From: "John R. Levine" <johnl@iecc.com>
To: Scott Kitterman <sklist@kitterman.com>
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Subject: Re: [Dcrup] Is there anything this WG wants to do not yet in draft-ietf-dcrup-dkim-crypto-01 ?
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> I think it's still not clear where the group lies on how dead we should kill
> rsa-sha1.  I think the WG chairs are going to have to evaluate the consensus
> and let us know.  Once that's done, converging on the correct wording should
> be ~easy (whether it ends up in my draft or John's).

Given that we are not the Network Police, I don't see this as a very 
meaningful questions We can tell people not to sign with sha-1 or to 
verify sha-1 signatures, but we can't threaten them with penalties if they 
ignore us.

In practice, the known problems with sha-1 aren't yet very relevant to 
short lived signatures like DKIM's since the cost of finding a collision 
remains high, so signers can't be bothered to upgrade their signers.  I 
looked at the last 1000 signed messages I got from non-spam bulkish 
mailers, and 354 of them still had sha1 signatures.  They can't be 
bothered to upgrade, and the IETF has no leverage.

At some point I expect one of the big gorillas will decide to stop 
accepting sha-1 and after a week of panic in the bulk mail community, 
they'll all patch their signers and we'll never see another sha-1 
signature again.

Regards,
John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly

PS: Hall of shame:

   67 d=patreon.com;
   37 d=bookbub.com;
   32 d=gbp.co.uk;
   20 d=email.powells.com;
   18 d=audiencerewards.com;
   17 d=astorwines.com;
   16 d=aaas.sciencepubs.org;
   12 d=e.avis.com;
   10 d=email.airbnb.com;
    7 d=mail125.wdc01.mcdlv.net;
    6 d=ebay.com;
    5 d=rocketmiles.com;
    4 d=sendgrid.me;
    4 d=rel1.aeroplan.com;
    4 d=mail63.us4.mcsv.net;
    4 d=e-vanguard.com;
    3 d=subscription.theatlantic.com;
    3 d=emessaging.us.hsbc.com;
    3 d=emails.hertz.com;
    3 d=cmail19.com;
    2 d=your.lufthansa-group.com;
    2 d=ted.com;
    2 d=notify.transunion.com;
    2 d=newsletter.milesandmore.com;
    2 d=mg.expediamail.com;
    2 d=mail70.atl11.rsgsv.net;
    2 d=mail215.atl171.mcdlv.net;
    2 d=mail103.atl161.mcsv.net;
    2 d=kickstarter.com;