Re: [openpgp] Web Key Directory I-D -07

azul <azul@riseup.net> Thu, 15 November 2018 09:16 UTC

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From: azul <azul@riseup.net>
Openpgp: preference=signencrypt
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Date: Thu, 15 Nov 2018 10:16:55 +0100
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Subject: Re: [openpgp] Web Key Directory I-D -07
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Hi,

>> Thus if presented with a new address test+foo@spodhuis.org and needing
>> to get a key for it, with Bart's proposal, the MUA and the OpenPGP
>> client software can make no assumptions.  It must not normalize anything
>> to the left of the '@' sign.  But the MUA can use WKD and get back a key
>> for <test@spodhuis.org>;; the software can then record a mapping of
>> test+foo@spodhuis.org -> test@spodhuis.org in OpenPGP recipient key
>> selection preferences.  When later sending email to
>> test+foo@spodhuis.org, the SMTP transaction proceeds unmodified: the MUA
>> does not rewrite the recipient, you have to preserve the address
>> as-given.  The remapped OpenPGP key selection proceeds as suggested
>> though.  If sending email to test+bar@spodhuis.org then another WKD
>> lookup needs to be made.  (Future work might look at protocols for
>> indicating patterns to avoid repeated lookups).
> I'm probably confused, but is this implying that WKD would insert a new
> "lookup" operation such that a compromised WKD could cause me to encrypt a
> message to an attacker-controlled key (with different UID) when I am trying
> to encrypt to a non-attacker peer?
As far as i understand the compromised WKD could easily send you
an attacker controlled key with a valid UID as well.

Why would the different UID make the attack any worse?

Cheers,
 Azul