Re: [lamps] Benjamin Kaduk's Discuss on draft-ietf-lamps-cms-hash-sig-09: (with DISCUSS and COMMENT)
Russ Housley <housley@vigilsec.com> Mon, 16 September 2019 16:33 UTC
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From: Russ Housley <housley@vigilsec.com>
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Date: Mon, 16 Sep 2019 12:33:34 -0400
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To: Ben Kaduk <kaduk@mit.edu>
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Subject: Re: [lamps] Benjamin Kaduk's Discuss on draft-ietf-lamps-cms-hash-sig-09: (with DISCUSS and COMMENT)
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Ben: Dropping the resolved parts ... >>> ---------------------------------------------------------------------- >>> DISCUSS: >>> ---------------------------------------------------------------------- >>> >>> Two fairly minor points that should be easy to resolve, but seem to be >>> worth some time: >>> >>> I think we need to be a bit more clear about what exactly the contents >>> of the signature OCTET STRING are. Section 3 has a fairly abstract note >>> about including enough information to be self-describing (within the >>> HSS/LMS variants), and Section 5 does better with "the single HSS >>> signature value resulting from the signing operation as specified in >>> [HASHSIG]", but it doesn't seem too burdensome to say something like >>> "the string returned from Algorithm 3 in [RFC8554]" or even refer back >>> to the description language at the end of Section 2 and avoid any >>> confusion. >> >> I suggest: >> >> The signature value is a large OCTET STRING as described in Section 2 >> of this document. The signature format is designed for easy parsing. >> The HSS, LMS, and LMOTS component of the signature value each format >> include a counter and a type code that indirectly providing all of >> the information that is needed to parse the value during signature >> validation. > > This is for the Section 3 text? I think that works for me, thanks. Yes, this text goes in Section 3. [snip] >>> ---------------------------------------------------------------------- >>> COMMENT: >>> ---------------------------------------------------------------------- >>> [snip] >>> Section 4 >>> >>> It feels a little surprising to make explicit requirements on the >>> keyUsage contents but not say anything about extendedKeyUsage. Having a >>> static whitelist of EKU OIDs is not reasonable, of course, and the >>> PUBLIC-KEY class from RFC 5912 only covers regular keyUsage, but some >>> advice about "encipherment methods are not going to make sense" might >>> still be appropriate. >> >> That is what the "it MUST NOT contain other values" does. RFC 5280 define the keyUsage bits as: >> >> KeyUsage ::= BIT STRING { >> digitalSignature (0), >> nonRepudiation (1), -- recent editions of X.509 have >> -- renamed this bit to contentCommitment >> keyEncipherment (2), >> dataEncipherment (3), >> keyAgreement (4), >> keyCertSign (5), >> cRLSign (6), >> encipherOnly (7), >> decipherOnly (8) } > > That's true, but does not seem relevant to extendedKeyUsage (unless you are > saying that restrictions on keyUsage somehow supersede usage of > extendedKeyUsage?) -- I understand what we are saying about keyUsage, and > wonder if we can say anything useful about extendedKeyUsage in an analogous > fashion. Because extendedKeyUsage is an object identifier, more are defined all the time, and they usually say something about protocol context. These are defined in RFC 5280: id-kp-serverAuth OBJECT IDENTIFIER ::= { id-kp 1 } -- TLS WWW server authentication -- Key usage bits that may be consistent: digitalSignature, -- keyEncipherment or keyAgreement id-kp-clientAuth OBJECT IDENTIFIER ::= { id-kp 2 } -- TLS WWW client authentication -- Key usage bits that may be consistent: digitalSignature -- and/or keyAgreement id-kp-codeSigning OBJECT IDENTIFIER ::= { id-kp 3 } -- Signing of downloadable executable code -- Key usage bits that may be consistent: digitalSignature id-kp-emailProtection OBJECT IDENTIFIER ::= { id-kp 4 } -- Email protection -- Key usage bits that may be consistent: digitalSignature, -- nonRepudiation, and/or (keyEncipherment or keyAgreement) So, for algorithms (without any protocol context) we only say anything about keyUsage. You can see this in RFC 3279, Section 2.3.. Russ
- [lamps] Benjamin Kaduk's Discuss on draft-ietf-la… Benjamin Kaduk via Datatracker
- Re: [lamps] Benjamin Kaduk's Discuss on draft-iet… Russ Housley
- Re: [lamps] Benjamin Kaduk's Discuss on draft-iet… Benjamin Kaduk
- Re: [lamps] Benjamin Kaduk's Discuss on draft-iet… Russ Housley