Have a look at the latest version I added OCTETS(STRING) to show the conversion. ASCII(STRING) seemed more confusing by drawing character encoding back in.
I was tempted to call it a octet array without the terminating NULL of STRING but didn’t want to introduce array. Let me know what you think. > On Jan 30, 2015, at 1:56 PM, Brian Campbell <bcampb...@pingidentity.com> > wrote: > > But, while it may be clear to you, what I'm saying here is that it's not > clear to a reader/implementer. > > Somehow the conversion from a character string to an octet string needs to be > clearly and unambiguously stated. It doesn't have to be the text I suggested > but it's not sufficient as it is now. > > Something like this might work, if you don't want to touch the parts in 4.2 > and 4.6: "SHA256(STRING) denotes a SHA2 256bit hash [RFC6234] of the octets > of the ASCII [RFC0020] representation of STRING." > > An "octet sequence using the url and filename safe Alphabet [...], with > length less than 128 characters." is ambiguous. Octets and characters are > intermixed with no mention of encoding. But they're not interchangeable. > > > On Fri, Jan 30, 2015 at 7:15 AM, Nat Sakimura <sakim...@gmail.com > <mailto:sakim...@gmail.com>> wrote: > I do not think we need ASCII(). It is quite clear without it, I suppose. > > In 4.1, I would rather do like: > > code_verifier = high entropy cryptographic random > octet sequence using the url and filename safe Alphabet [A-Z] / [a-z] > / [0-9] / "-" / "_" from Sec 5 of RFC 4648 [RFC4648], with length > less than 128 characters. > > Nat > > 2015-01-30 22:51 GMT+09:00 Brian Campbell <bcampb...@pingidentity.com > <mailto:bcampb...@pingidentity.com>>: > That's definitely an improvement (to me anyway). > > Checking that the rest of the document uses those notations appropriately, I > think, yields a few other changes. And probably begs for the "ASCII(STRING) > denotes the octets of the ASCII representation of STRING" notation/function, > or something like it, to be put back in. Those changes might look like the > following: > > > In 4.1.: > > OLD: > code_verifier = high entropy cryptographic random ASCII [RFC0020] > octet sequence using the url and filename safe Alphabet [A-Z] / [a-z] > / [0-9] / "-" / "_" from Sec 5 of RFC 4648 [RFC4648], with length > less than 128 characters. > > NEW (maybe): > code_verifier = high entropy cryptographically strong random STRING > using the url and filename safe Alphabet [A-Z] / [a-z] > / [0-9] / "-" / "_" from Sec 5 of RFC 4648 [RFC4648], with length > less than 128 characters. > > > In 4.2.: > > OLD: > S256 "code_challenge" = BASE64URL(SHA256("code_verifier")) > > NEW (maybe): > S256 "code_challenge" = BASE64URL(SHA256(ASCII("code_verifier"))) > > > In 4.6.: > > OLD: > SHA256("code_verifier" ) == BASE64URL-DECODE("code_challenge"). > > NEW (maybe): > SHA256(ASCII("code_verifier")) == BASE64URL-DECODE("code_challenge"). > > > > > On Thu, Jan 29, 2015 at 8:37 PM, Nat Sakimura (=nat) <n...@sakimura.org > <mailto:n...@sakimura.org>> wrote: > I take your point, Brian. > > In our most recent manuscript, STRING is defined inside ASCII(STRING) as > > STRING is a sequence of zero or more ASCII characters > > but it is kind of circular, and we do not seem to use ASCII(). > > What about re-writing the section like below? > > STRING denotes a sequence of zero or more ASCII [RFC0020] > <http://xml2rfc.ietf.org/cgi-bin/xml2rfc.cgi#RFC0020> characters. > > OCTETS denotes a sequence of zero or more octets. > > BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per Section 3 > <http://xml2rfc.ietf.org/cgi-bin/xml2rfc.cgi#Terminology> producing a > ASCII[RFC0020] <http://xml2rfc.ietf.org/cgi-bin/xml2rfc.cgi#RFC0020> STRING. > > BASE64URL-DECODE(STRING) denotes the base64url decoding of STRING, per > Section 3 <http://xml2rfc.ietf.org/cgi-bin/xml2rfc.cgi#Terminology>, > producing a sequence of octets. > > SHA256(OCTETS) denotes a SHA2 256bit hash [RFC6234] > <http://xml2rfc.ietf.org/cgi-bin/xml2rfc.cgi#RFC6234> of OCTETS. > > > > > > > >> On Jan 30, 2015, at 08:15, Brian Campbell <bcampb...@pingidentity.com >> <mailto:bcampb...@pingidentity.com>> wrote: >> >> In §2 [1] we've got "SHA256(STRING) denotes a SHA2 256bit hash [RFC6234] of >> STRING." >> >> But, in the little cow town where I come from anyway, you hash bits/octets >> not character strings (BTW, "STRING" isn't defined anywhere but it's kind of >> implied that it's a string of characters). >> >> Should it say something more like "SHA256(STRING) denotes a SHA2 256bit hash >> [RFC6234] of the octets of the ASCII [RFC0020] representation of STRING."? >> >> I know it's kind of pedantic but I find it kind of confusing because the >> code_verifier uses the url and filename safe alphabet, which has me second >> guessing if SHA256(STRING) actually means a hash of the octet produced by >> base64url decoding the string. >> >> Maybe it's just me but, when reading the text, I find the transform process >> to be much more confusing than I think it needs to be. Removing and >> clarifying some things will help. I hate to suggest this but maybe an >> example showing the computation steps on both ends would be helpful? >> >> Also "UTF8(STRING)" and "ASCII(STRING)" notations are defined in §2 but not >> used anywhere. >> >> And §2 also says, "BASE64URL-DECODE(STRING) denotes the base64url decoding >> of STRING, per Section 3, producing a UTF-8 sequence of octets." But what is >> a UTF-8 sequence of octets? Isn't it just a sequence octets? The [RFC3629] >> reference, I think, could be removed. >> >> [1] https://tools.ietf.org/html/draft-ietf-oauth-spop-06#section-2 >> <https://tools.ietf.org/html/draft-ietf-oauth-spop-06#section-2> > > Nat Sakimura > n...@sakimura.org <mailto:n...@sakimura.org> > > > > > > > > > > -- > Nat Sakimura (=nat) > Chairman, OpenID Foundation > http://nat.sakimura.org/ <http://nat.sakimura.org/> > @_nat_en >
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