initial commit

.gitignore

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+ebin
+deps
+.eunit
+.ct
+logs
+test/*.beam
+erl_crash.dump

LICENSE.txt

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+Copyright (c) 2013 Vladimir Dronnikov <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Makefile

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+all: deps compile check test
+
+deps:
+	rebar get-deps
+
+compile:
+	rebar compile
+
+run: compile
+	sh start.sh
+
+clean:
+	rebar clean
+	rm -fr ebin .ct test/*.beam
+
+check:
+	rebar eunit skip_deps=true
+
+test:
+	#rebar ct
+	mkdir -p .ct
+	ct_run -dir test -logdir .ct -pa ebin
+
+dist: deps compile
+	echo TODO
+
+.PHONY: all deps compile check test run clean dist
+.SILENT:
+

README.md

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+Termit
+==============
+
+Library for serializing Erlang terms to signed encrypted binaries and reliably deserializing them back.
+
+Usage
+--------------
+
+A typical use case is to provide means to keep secrets put in public domain, e.g. secure cookies.
+
+```erlang
+Term = {this, is, an, [erlang, <<"term">>]}.
+Cookie = termit:encode_base64(Term, <<"cekpet">>).
+
+% time-to-live is 1000 seconds =:= secret valid no more than 1000 seconds
+{ok, Term} = termit:decode_base64(Cookie, <<"cekpet">>, 1000).
+% time-to-live is 0 seconds =:= expired
+{error, expired} = termit:decode_base64(Cookie, <<"cekpet">>, 0).
+
+% check whether secret was not forged
+{error, forged} = termit:decode_base64(<<Cookie/binary, "1">>, <<"cekpet">>, 1000).
+{error, forged} = termit:decode_base64(Cookie, <<"secret">>, 1000).
+{error, forged} = termit:decode_base64(undefined, <<"cekpet">>, 1000).
+```
+
+[License](termit/blob/master/LICENSE.txt)
+-------
+
+Copyright (c) 2013 Vladimir Dronnikov <[email protected]>
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

rebar.config

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+{lib_dirs, ["deps"]}.
+
+{erl_opts, [
+  debug_info,
+  warn_format,
+  warn_export_vars,
+  warn_obsolete_guard,
+  warn_bif_clash
+]}.
+
+{cover_enabled, true}.

src/termit.app.src

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+{application, termit, [
+  {description, "Securely serialize/deserialize Erlang terms"},
+  {vsn, "0.0.1"},
+  {registered, []},
+  {applications, [
+    kernel,
+    stdlib
+  ]},
+  {env, []}
+]}.

src/termit.erl

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+%%
+%% @doc Serialize an Erlang term to signed encrypted binary and
+%% deserialize it back ensuring it's not been forged.
+%%
+
+-module(termit).
+-author('Vladimir Dronnikov <[email protected]>').
+
+-export([
+    encode/2, decode/3,
+    encode_base64/2, decode_base64/3
+  ]).
+
+%%
+%% -----------------------------------------------------------------------------
+%% @doc Serialize Term, encrypt and sign the result with Secret.
+%% Return binary().
+%% -----------------------------------------------------------------------------
+%%
+
+-spec encode(Term :: any(), Secret :: binary()) -> Cipher :: binary().
+
+encode(Term, Secret) ->
+  Bin = term_to_binary(Term),
+  Enc = encrypt(Bin, Secret),
+  {MegaSecs, Secs, _} = erlang:now(),
+  Time = list_to_binary(integer_to_list(MegaSecs * 1000000 + Secs)),
+  Sig = sign(<<Time/binary, Enc/binary>>, Secret),
+  <<Sig/binary, Time/binary, Enc/binary>>.
+
+%%
+%% -----------------------------------------------------------------------------
+%% @doc Given a result of encode/2, i.e. a signed encrypted binary,
+%% check the signature, uncrypt and deserialize into original term.
+%% Check it timestamp encoded into the data is not older than Ttl.
+%% Return {ok, Term} or {error, Reason}.
+%% -----------------------------------------------------------------------------
+%%
+
+-spec decode(
+    Cipher :: binary(),
+    Secret :: binary(),
+    Ttl :: non_neg_integer()
+  ) -> {ok, Term :: any()} | {error, Reason :: atom()}.
+
+%% @todo how do we know time is 10 octets?
+
+decode(<<Sig:32/binary, Time:10/binary, Enc/binary>>, Secret, Ttl) ->
+  case sign(<<Time/binary, Enc/binary>>, Secret) of
+      % signature ok?
+      Sig ->
+        Bin = uncrypt(Enc, Secret),
+        % deserialize
+        try binary_to_term(Bin, [safe]) of
+            Term ->
+              % not yet expired?
+              {MegaSecs, Secs, _} = erlang:now(),
+              Now = MegaSecs * 1000000 + Secs,
+              Expires = list_to_integer(binary_to_list(Time)) + Ttl,
+              case Expires > Now of
+                  true ->
+                    {ok, Term};
+                  false ->
+                    {error, expired}
+                end
+          catch _:_ ->
+              {error, badarg}
+          end;
+      _ ->
+        {error, forged}
+    end;
+
+%% N.B. unmatched binaries are forged
+decode(Bin, _, _) when is_binary(Bin) ->
+  {error, forged}.
+
+%%
+%% -----------------------------------------------------------------------------
+%% @doc Get 32-byte SHA1 sum of Data salted with Secret.
+%% -----------------------------------------------------------------------------
+%%
+
+-spec sign(binary(), binary()) -> binary().
+
+sign(Data, Secret) ->
+  crypto:sha256([Data, Secret]).
+
+%%
+%% -----------------------------------------------------------------------------
+%% @doc Encrypt Bin using Secret.
+%% -----------------------------------------------------------------------------
+%%
+
+-spec encrypt(binary(), binary()) -> binary().
+
+encrypt(Bin, Secret) ->
+  <<Key:16/binary, IV:16/binary>> = crypto:sha256(Secret),
+  crypto:aes_cfb_128_encrypt(Key, IV, Bin).
+
+%%
+%% -----------------------------------------------------------------------------
+%% @doc Uncrypt Bin using Secret.
+%% -----------------------------------------------------------------------------
+%%
+
+-spec uncrypt(binary(), binary()) -> binary().
+
+uncrypt(Bin, Secret) ->
+  <<Key:16/binary, IV:16/binary>> = crypto:sha256(Secret),
+  crypto:aes_cfb_128_decrypt(Key, IV, Bin).
+
+%%
+%% -----------------------------------------------------------------------------
+%% Conversion helpers
+%% -----------------------------------------------------------------------------
+%%
+
+encode_base64(Term, Secret) ->
+  base64:encode(encode(Term, Secret)).
+
+decode_base64(undefined, _, _) ->
+  {error, forged};
+
+decode_base64(Bin, Secret, Ttl) when is_binary(Bin) ->
+  decode(base64:decode(Bin), Secret, Ttl).
+
+%%
+%% -----------------------------------------------------------------------------
+%% Some unit tests
+%% -----------------------------------------------------------------------------
+%%
+
+-ifdef(TEST).
+-include_lib("eunit/include/eunit.hrl").
+
+encrypt_test() ->
+  Secret = <<"Make It Elegant">>,
+  Bin = <<"Transire Benefaciendo">>,
+  ?assertEqual(Bin, uncrypt(encrypt(Bin, Secret), Secret)),
+  ?assert(Bin =/= uncrypt(encrypt(Bin, Secret), <<Secret/binary, "1">>)),
+  ?assert(Bin =/= uncrypt(encrypt(Bin, <<Secret/binary, "1">>), Secret)).
+
+smoke_test() ->
+  Term = {a, b, c, [d, "e", <<"foo">>]},
+  Secret = <<"TopSecRet">>,
+  Enc = encode(Term, Secret),
+  % decode encoded term with valid time to live
+  ?assertEqual({ok, Term}, decode(Enc, Secret, 1)),
+  % expired data
+  ?assertEqual({error, expired}, decode(encode(Term, Secret), Secret, 0)),
+  % forged data
+  ?assertEqual({error, forged}, decode(<<"1">>, Secret, 1)),
+  ?assertEqual({error, forged}, decode(<<Enc/binary, "1">>, Secret, 1)).
+
+encode_test(_Config) ->
+  Term = {a, b, c, [d, "e", <<"foo">>]},
+  Secret = <<"TopSecRet">>,
+  undefined = decode_base64(undefined, a, b),
+  {ok, Term} = decode_base64(encode_base64(Term, Secret), Secret, 1),
+  {error, expired} = decode_base64(encode_base64(Term, Secret), Secret, 0).
+
+-endif.

test/termit_SUITE.erl

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+-module(termit_SUITE).
+-author('Vladimir Dronnikov <[email protected]>').
+
+%% interface
+-export([all/0]).
+
+%% tests
+-export([encode_test/1]).
+
+-include_lib("common_test/include/ct.hrl").
+
+all() ->
+  [encode_test].
+
+encode_test(_Config) ->
+  Term = {a, b, c, [d, "e", <<"foo">>]},
+  Secret = <<"TopSecRet">>,
+  {error, forged} = termit:decode_base64(undefined, a, b),
+  {ok, Term} = termit:decode_base64(
+      termit:encode_base64(Term, Secret), Secret, 1),
+  {error, expired} = termit:decode_base64(
+      termit:encode_base64(Term, Secret), Secret, 0).