[dnsext] spaces in hex DS digest, NSEC3 salt and SSHFP

[bert hubert <[e-mail]>]

Hi everybody,

PowerDNSSEC turns out to be confused by spaces in the database (or zone
file) in the DS digest. It terminates the digest at the first non-hex
character.

The venerable 'dig' tool emits DS digest type 2 with spaces:
powerdns.nl.		7200	IN	NS	powerdnssec2.ds9a.nl.
powerdns.nl.		7200	IN	NS	powerdnssec1.ds9a.nl.
powerdns.nl.		7200	IN	DS	7354 8 2
F238862D8DFCB5C837D33E28C0D318191DBA76FFC87C6F053D2AD67E 22BF1D7C

RFC 3658 says: 

 'The presentation format of the DS record consists of three numbers
  (key tag, algorithm, and digest type) followed by the digest itself
  presented in hex'

It says nothing about spaces in the hex. Of course we could be liberal in
what we accept, however, there is also the NSEC3 and NSEC3PARAM which store
the salt.. in hex.

RFC5155 says:

	The Salt field is represented as a sequence of case-insensitive
      	hexadecimal digits.  Whitespace is not allowed within the
      	sequence.

Finally, SSHFP is the third type that encodes hex blobs, and RFC 4255
states:

   'The RDATA of the presentation format of the SSHFP resource record
   consists of two numbers (algorithm and fingerprint type) followed by
   the fingerprint itself, presented in hex"

Sadly this breaks the nice symmetry where we had only one 'hexBlob', one
that terminates at the first space.

Because 'dig' is so widely distributed, I'm afraid we'll have no choice but
to butcher PowerDNS into dealing with the spaces, but what do people think?
Do spaces belong in hex blobs, and in the DS specifically?

	Bert