Canonicalise DS RR and refactor dns a bit.dnssec

Rename split_rrset/1 -> decode_rrset/1.
Add type rr() and use it.
Canonicalise DS RR.

1 files changed, 52 insertions, 22 deletions

diff --git a/src/dns.erl b/src/dns.erl
index 24fb8fb..b8a8ffe 100644
--- a/src/dns.erl
+++ b/src/dns.erl
@@ -2,22 +2,33 @@
 %%% See LICENSE for licensing information.
 
 -module(dns).
--export([split_rrset/1, encode_rr/1, encode_rrset/1]).
+-export([decode_rrset/1, decode_rr/1, encode_rrset/1, encode_rr/1,
+         canonicalize_dsrr/2]).
 
-decode_name_label(Name) ->
-    <<Len:8/integer, Label:Len/binary, Rest/binary>> = Name,
-    {Label, Rest}.
+-record(rr, {name :: list(),                    % List of name labels.
+             type :: binary(),
+             class :: binary(),
+             ttl :: integer(),
+             rdata :: binary()}).
+-type rr() :: #rr{}.
 
+-spec decode_name_label(binary()) -> tuple().
+decode_name_label(RRbin) ->
+    <<Len:8/integer, Label:Len/binary, Rest/binary>> = RRbin,
+    {binary_to_list(Label), Rest}.
+
+-spec encode_name_label(string()) -> binary().
 encode_name_label(Label) ->
-    Len = byte_size(Label),
-    <<Len:8/integer, Label/binary>>.
+    LabelBin = list_to_binary(Label),
+    Len = byte_size(LabelBin),
+    <<Len:8/integer, LabelBin/binary>>.
 
-decode_name(RR) ->
-    decode_name(RR, []).
+decode_name(RRbin) ->
+    decode_name(RRbin, []).
 decode_name(<<0, Rest/binary>>, Acc) ->
     {lists:reverse(Acc), Rest};
-decode_name(Name, Acc) ->
-    {Label, Rest} = decode_name_label(Name),
+decode_name(RRbin, Acc) ->
+    {Label, Rest} = decode_name_label(RRbin),
     decode_name(Rest, [Label | Acc]).
 
 -spec encode_name(list()) -> binary().
@@ -29,28 +40,29 @@ encode_name([], Acc) ->
 encode_name([H|T], Acc) ->
     encode_name(T, [encode_name_label(H) | Acc]).
 
--spec decode_rr(binary()) -> {list(), binary()}.
-decode_rr(RR) ->
-    {Name, RestRR} = decode_name(RR),
+-spec decode_rr(binary()) -> {rr(), binary()}.
+decode_rr(RRBin) ->
+    {Name, RestRR} = decode_name(RRBin),
     <<Type:2/binary,
       Class:2/binary,
       TTL:4/integer-unit:8,
       RDLength:2/integer-unit:8,
       RDATA:RDLength/binary,
       Rest/binary>> = RestRR,
-    {[Name, Type, Class, TTL, RDATA], Rest}.
+    {#rr{name = Name, type = Type, class = Class, ttl = TTL, rdata = RDATA},
+     Rest}.
 
--spec split_rrset(binary()) -> list().
-split_rrset(RRSet) ->
-    split_rrset(RRSet, []).
-split_rrset(<<>>, Acc) ->
+-spec decode_rrset(binary()) -> [rr()].
+decode_rrset(RRSet) ->
+    decode_rrset(RRSet, []).
+decode_rrset(<<>>, Acc) ->
     lists:reverse(Acc);
-split_rrset(RRSet, Acc) ->
+decode_rrset(RRSet, Acc) ->
     {RR, Rest} = decode_rr(RRSet),
-    split_rrset(Rest, [RR | Acc]).
+    decode_rrset(Rest, [RR | Acc]).
 
--spec encode_rr(list()) -> binary().
-encode_rr([Name, Type, Class, TTL, RDATA]) ->
+-spec encode_rr(rr()) -> binary().
+encode_rr(#rr{name = Name, type = Type, class = Class, ttl = TTL, rdata = RDATA}) ->
     EncodedName = encode_name(Name),
     RDLength = byte_size(RDATA),
     <<EncodedName/binary,
@@ -67,3 +79,21 @@ encode_rrset([], Acc) ->
     list_to_binary(lists:reverse(Acc));
 encode_rrset([H|T], Acc) ->
     encode_rrset(T, [encode_rr(H) | Acc]).
+
+%% Cacnonicalise a single DS RR according to RFC4034 section 6.2.
+canonicalize_dsrr(DS, RRSIG) ->
+    %% 1. expand domain name
+    %% FIXME: What does a compressed name look like?
+
+    %% 2. lowercase
+    LCName = lists:map(fun(L) -> string:to_lower(L) end, DS#rr.name),
+
+    %% 3. N/A for DS
+    %% 4. N/A for DS FIXME: verify
+
+    %% 5. set TTL to that of the RRSIG
+    OrigTTL = RRSIG#rr.ttl,
+
+    DS#rr{name = LCName, ttl = OrigTTL}.
+
+%% TODO: Add unit tests.