Say if you had to write an erratum explaining this, rather than
fixing it...what'd you say?
And (assuming such a note is useful) would it make sense to
add that to the RFC?
S.
Eric Allman wrote:
Well, this is unfortunate, and I'm not sure how we ended up with both
FWS and LWSP at the same time. As Frank noted they are nearly equivalent.
The problem is that both of them are assuming use in a header field
context, which requires the trailing white space. Contrary to what
Frank says, just replacing LWSP with [FWS] won't solve the problem. In
fact, since base64string is used both in the DKIM-Signature header field
and in the selector record, we would need to split that in two. Ugly.
For the time being I agree with Paul's suggestion: live with it. This is
the sort of thing that can be solved in DKIMbis, which I'm sure will be
required before DKIM gets to full standard.
eric
--On March 7, 2007 9:34:45 AM +0100 Mark Martinec
<Mark(_dot_)Martinec+dkim(_at_)ijs(_dot_)si> wrote:
I came across a real life example where a public key as returned
by a DNS record contained embedded CR LF, probably due to a
misconfiguration or a broken DNS server implementation.
Two different DKIM implementations gave different treatment to the
situation, one claiming 'key syntax error', the other accepted it.
Turning to draft-ietf-dkim-base-10 reveals:
key-p-tag = %x70 [FWS] "=" [ [FWS] base64string ]
base64string = 1*(ALPHA / DIGIT / "+" / "/" / LWSP)
[ "=" LWSP [ "=" LWSP ] ]
LWSP = *(WSP / CRLF WSP)
which would indicate that a public key in TXT RR
like the following would be alright:
k=rsa; p=MIGfMA0GCSq<CR><LF><SP>GSIb3DQEBAQUA...
while the one without a <SP> would not be syntactically correct:
k=rsa; p=MIGfMA0GCSq<CR><LF>GSIb3DQEBAQUA...
It seems the requirement to insist on LWSP (e.g. a WSP must follow
CRLF) in a non- message header context is very much artificial and
unwarranted.
Mark
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