Minor When constructing RRSIGs, I suppose normalisation of character case to lowercase is needed to avoid being unable to validate a <domain-name> value in situations where case got mangled in a resolver. What ods-signer also does however, is write out the <domain-name> to the output zone file in all-lowercase, which is not in line with the intentions of DNS to preserve case as much as possible.
I noticed this when signing a number of PTR records, but I assume it applies generally to all <domain-name> occurrences. From the RFC's below, I had not expected the mapping to lowercase, and I would argue that it is not in line with the intentions of DNS.
The testdata was:
_kerberos.lowercase.ptrdemo.vanrein.org. 3600 IN PTR
lowercase.vanrein.org.
_kerberos.mixedcase.ptrdemo.vanrein.org. 3600 IN PTR
MiXeDcAsE.VaNrEiN.OrG.
_kerberos.uppercase.ptrdemo.vanrein.org. 3600 IN PTR
UPPERCASE.VANREIN.ORG.
STANDARDS TEXT
Section 4.1 of RFC 4343:
No "case conversion" or "case folding" is done
during such output operations, thus "preserving" case. However, to
optimize output, indirect labels may be used to point to names
elsewhere in the DNS answer. In determining whether the name to be
pointed to (for example, the QNAME) is the "same" as the remainder of
the name being optimized, the case insensitive comparison specified
above is done. Thus, such optimization may easily destroy the output
preservation of case.
Section 3.3 of RFC 1035:
The following RR definitions are expected to occur, at least
potentially, in all classes. In particular, NS, SOA, CNAME, and PTR
will be used in all classes, and have the same format in all classes.
Because their RDATA format is known, all domain names in the RDATA
section of these RRs may be compressed.
<domain-name> is a domain name represented as a series of labels, and
terminated by a label with zero length. <character-string> is a single
length octet followed by that number of characters. <character-string>
is treated as binary information, and can be up to 256 characters in
length (including the length octet).
[...]
3.3.12. PTR RDATA format
--+
/ PTRDNAME /
--+
where:
PTRDNAME A <domain-name> which points to some location in the
domain name space.
