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%%% @doc Server holding log entries in a database and hashes in a Merkle tree.
%%%
%%% When you submit data for insertion in the log, the data and a hash
%%% of it is stored in a way that [mumble FIXME and FIXME]. In return
%%% you will get a proof of your entry being included in the log. This
%%% proof can later, together with the public key of the log, be used
%%% to prove that your entry is indeed present in the log.
-module('plop').
-include("plop.hrl").
-include_lib("public_key/include/public_key.hrl").
-include_lib("eunit/include/eunit.hrl").
-export([start/2, loop/1, dummy_add/1]).
-record(plop, {pubkey :: public_key:rsa_public_key(),
privkey :: public_key:rsa_private_key(),
logid :: binary(),
hashtree :: ht:head()}).
-spec start(string(), string()) -> pid().
start(Keyfile, Passphrase) ->
{Private_key, Public_key} = read_keyfile(Keyfile, Passphrase),
LogID = crypto:hash(sha256, public_key:der_encode('RSAPublicKey', Public_key)),
Plop = #plop{pubkey = Public_key,
privkey = Private_key,
logid = LogID,
hashtree = ht:create()},
Pid = spawn_link(plop, loop, [Plop]),
register(plop, Pid),
Pid.
log(Format, Data) ->
io:format(Format, Data).
loop(Plop) ->
receive
{From, quit} ->
From ! {ok, quit};
{From, Data} ->
handle_req(From, Plop, Data),
loop(Plop);
Unknown ->
log("DEBUG: Received malformed command: ~p~n", [Unknown]),
loop(Plop)
end.
-spec serialise(plop_entry() | plop_data()) -> iolist().
serialise(#plop_entry{type = EntryType, entry = Entry}) ->
[<<EntryType:16>>, Entry];
serialise(#plop_data{version = Version,
signature_type = Sigtype,
timestamp = Timestamp,
entry = Entry}) ->
[<<Version:8, Sigtype:8, Timestamp:64>>, serialise(Entry)].
handle_req(From,
#plop{privkey = Privkey,
logid = LogID,
hashtree = Tree},
Arg) ->
case Arg of
{add, PlopData = #plop_data{entry = Entry}} when is_record(Entry, plop_entry) ->
%% fixme: add Entry to db,
H = ht:append(Tree, serialise(Entry)),
SPT = spt(LogID, Privkey, PlopData),
%%io:format("adding ~p to ~p -> H: ~p, SPT: ~p~n",
[Entry, Tree, H, SPT]),
From ! {ok, SPT};
sth -> % Signed tree head.
From ! {ok, sth(Tree)};
Unknown ->
From ! {error, Unknown}
end.
%% RFC6962
%% Signed Timestamp
%% struct {
%% Version sct_version;
%% LogID id;
%% uint64 timestamp;
%% CtExtensions extensions;
%% digitally-signed struct {
%% Version sct_version;
%% SignatureType signature_type = certificate_timestamp;
%% uint64 timestamp;
%% LogEntryType entry_type;
%% select(entry_type) {
%% case x509_entry: ASN.1Cert;
%% case precert_entry: PreCert;
%% } signed_entry;
%% CtExtensions extensions;
%% };
%% } SignedCertificateTimestamp;
%% RRC 5246
%% A digitally-signed element is encoded as a struct DigitallySigned:
%% struct {
%% SignatureAndHashAlgorithm algorithm;
%% opaque signature<0..2^16-1>;
%% } DigitallySigned;
-define(PLOPVERSION, 1).
%% @doc Signed Plop Timestamp.
spt(LogID, PrivKey, #plop_data{version = Version, % >= 1
signature_type = Sigtype, % >= 0
timestamp = Timestamp_in,
entry = Entry = #plop_entry{}}) when is_binary(LogID) ->
Timestamp = case Timestamp_in of
now ->
{NowMegaSec, NowSec, NowMicroSec} = now(),
trunc(NowMegaSec * 1.0e9 + NowSec * 1.0e3 + NowMicroSec / 1.0e3);
_ -> Timestamp_in
end,
BinToSign = list_to_binary(
serialise(#plop_data{version = Version,
signature_type = Sigtype,
timestamp = Timestamp,
entry = Entry})),
%% Was going to just sign/3 the hash but looking at
%% digitally_signed() in lib/ssl/src/ssl_handshake.erl it seems
%% like we should rather use (undocumented) encrypt_private/3.
%public_key:sign(hash(sha256, BinToSign), sha256, PrivKey)
Signature = public_key:encrypt_private(crypto:hash(sha256, BinToSign),
PrivKey,
[{rsa_pad, rsa_pkcs1_padding}]),
SPT = <<?PLOPVERSION:8,
LogID/binary,
Timestamp:64,
Signature/binary>>,
%%io:format("SPT: ~p~nBinToSign: ~p~nSignature = ~p~n", [SPT, BinToSign, Signature]),
SPT.
%% @doc Signed Tree Head
%% digitally-signed struct {
%% Version version;
%% SignatureType signature_type = tree_hash;
%% uint64 timestamp;
%% uint64 tree_size;
%% opaque sha256_root_hash[32];
%% } TreeHeadSignature;
sth(Tree) ->
"FIXME: signed tree head for " ++ Tree.
read_keyfile(Filename, Passphrase) ->
{ok, PemBin} = file:read_file(Filename),
[Entry] = public_key:pem_decode(PemBin),
Privatekey = public_key:pem_entry_decode(Entry, Passphrase),
{Privatekey, public_key(Privatekey)}.
public_key(#'RSAPrivateKey'{modulus = Mod, publicExponent = Exp}) ->
#'RSAPublicKey'{modulus = Mod, publicExponent = Exp}.
%%%%%%%%%%%%%%%%%%%%
%% Playing around
dummy_add(String) ->
String.
%%%%%%%%%%%%%%%%%%%%
%% Tests.
serialise_test_() ->
Entry = #plop_entry{type = ?PLOP_ENTRY_TYPE_X509, entry = "foo"},
Entry_serialised = <<0:16, "foo">>,
[?_assertEqual(Entry_serialised, list_to_binary(serialise(Entry))),
?_assertEqual(<<1:8, 0:8, 0:64, Entry_serialised/binary>>,
list_to_binary(serialise(#plop_data{signature_type = 0,
timestamp = 0,
entry = Entry})))].
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