| %% @author Asier Azkuenaga Batiz <asier@zebixe.com> |
| %% @copyright 2013 Mochi Media, Inc. |
| %% |
| %% 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. |
| |
| %% @doc HTTP Cookie session. Note that the expiration time travels unencrypted |
| %% as far as this module is concerned. In order to achieve more security, |
| %% it is advised to use https. |
| %% Based on the paper |
| %% <a href="http://www.cse.msu.edu/~alexliu/publications/Cookie/cookie.pdf"> |
| %% "A Secure Cookie Protocol"</a>. |
| %% This module is only supported on R15B02 and later, the AES CFB mode is not |
| %% available in earlier releases of crypto. |
| -module(mochiweb_session). |
| -export([generate_session_data/4, generate_session_cookie/4, |
| check_session_cookie/4]). |
| |
| -export_types([expiration_time/0]). |
| -type expiration_time() :: integer(). |
| -type key_fun() :: fun((string()) -> iolist()). |
| |
| %% TODO: Import this from elsewhere after attribute types refactor. |
| -type header() :: {string(), string()}. |
| |
| %% @doc Generates a secure encrypted binary convining all the parameters. The |
| %% expiration time must be a 32-bit integer. |
| -spec generate_session_data( |
| ExpirationTime :: expiration_time(), |
| Data :: iolist(), |
| FSessionKey :: key_fun(), |
| ServerKey :: iolist()) -> binary(). |
| generate_session_data(ExpirationTime, Data, FSessionKey, ServerKey) |
| when is_integer(ExpirationTime), is_function(FSessionKey)-> |
| BData = ensure_binary(Data), |
| ExpTime = integer_to_list(ExpirationTime), |
| Key = gen_key(ExpTime, ServerKey), |
| Hmac = gen_hmac(ExpTime, BData, FSessionKey(ExpTime), Key), |
| EData = encrypt_data(BData, Key), |
| mochiweb_base64url:encode( |
| <<ExpirationTime:32/integer, Hmac/binary, EData/binary>>). |
| |
| %% @doc Convenience wrapper for generate_session_data that returns a |
| %% mochiweb cookie with "id" as the key, a max_age of 20000 seconds, |
| %% and the current local time as local time. |
| -spec generate_session_cookie( |
| ExpirationTime :: expiration_time(), |
| Data :: iolist(), |
| FSessionKey :: key_fun(), |
| ServerKey :: iolist()) -> header(). |
| generate_session_cookie(ExpirationTime, Data, FSessionKey, ServerKey) |
| when is_integer(ExpirationTime), is_function(FSessionKey)-> |
| CookieData = generate_session_data(ExpirationTime, Data, |
| FSessionKey, ServerKey), |
| mochiweb_cookies:cookie("id", CookieData, |
| [{max_age, 20000}, |
| {local_time, |
| calendar:universal_time_to_local_time( |
| calendar:universal_time())}]). |
| |
| %% TODO: This return type is messy to express in the type system. |
| -spec check_session_cookie( |
| ECookie :: binary(), |
| ExpirationTime :: string(), |
| FSessionKey :: key_fun(), |
| ServerKey :: iolist()) -> |
| {Success :: boolean(), |
| ExpTimeAndData :: [integer() | binary()]}. |
| check_session_cookie(ECookie, ExpirationTime, FSessionKey, ServerKey) |
| when is_binary(ECookie), is_integer(ExpirationTime), |
| is_function(FSessionKey) -> |
| case mochiweb_base64url:decode(ECookie) of |
| <<ExpirationTime1:32/integer, BHmac:20/binary, EData/binary>> -> |
| ETString = integer_to_list(ExpirationTime1), |
| Key = gen_key(ETString, ServerKey), |
| Data = decrypt_data(EData, Key), |
| Hmac2 = gen_hmac(ETString, |
| Data, |
| FSessionKey(ETString), |
| Key), |
| {ExpirationTime1 >= ExpirationTime andalso eq(Hmac2, BHmac), |
| [ExpirationTime1, binary_to_list(Data)]}; |
| _ -> |
| {false, []} |
| end; |
| check_session_cookie(_ECookie, _ExpirationTime, _FSessionKey, _ServerKey) -> |
| {false, []}. |
| |
| %% 'Constant' time =:= operator for binary, to mitigate timing attacks. |
| -spec eq(binary(), binary()) -> boolean(). |
| eq(A, B) when is_binary(A) andalso is_binary(B) -> |
| eq(A, B, 0). |
| |
| eq(<<A, As/binary>>, <<B, Bs/binary>>, Acc) -> |
| eq(As, Bs, Acc bor (A bxor B)); |
| eq(<<>>, <<>>, 0) -> |
| true; |
| eq(_As, _Bs, _Acc) -> |
| false. |
| |
| -spec ensure_binary(iolist()) -> binary(). |
| ensure_binary(B) when is_binary(B) -> |
| B; |
| ensure_binary(L) when is_list(L) -> |
| iolist_to_binary(L). |
| |
| -ifdef(crypto_compatibility). |
| -spec encrypt_data(binary(), binary()) -> binary(). |
| encrypt_data(Data, Key) -> |
| IV = crypto:strong_rand_bytes(16), |
| Crypt = crypto:aes_cfb_128_encrypt(Key, IV, Data), |
| <<IV/binary, Crypt/binary>>. |
| |
| -spec decrypt_data(binary(), binary()) -> binary(). |
| decrypt_data(<<IV:16/binary, Crypt/binary>>, Key) -> |
| crypto:aes_cfb_128_decrypt(Key, IV, Crypt). |
| |
| -spec gen_key(iolist(), iolist()) -> binary(). |
| gen_key(ExpirationTime, ServerKey)-> |
| crypto:md5_mac(ServerKey, [ExpirationTime]). |
| |
| -spec gen_hmac(iolist(), binary(), iolist(), binary()) -> binary(). |
| gen_hmac(ExpirationTime, Data, SessionKey, Key) -> |
| crypto:sha_mac(Key, [ExpirationTime, Data, SessionKey]). |
| |
| -else. |
| -spec encrypt_data(binary(), binary()) -> binary(). |
| encrypt_data(Data, Key) -> |
| IV = crypto:strong_rand_bytes(16), |
| Crypt = crypto:block_encrypt(aes_cfb128, Key, IV, Data), |
| <<IV/binary, Crypt/binary>>. |
| |
| -spec decrypt_data(binary(), binary()) -> binary(). |
| decrypt_data(<<IV:16/binary, Crypt/binary>>, Key) -> |
| crypto:block_decrypt(aes_cfb128, Key, IV, Crypt). |
| |
| -spec gen_key(iolist(), iolist()) -> binary(). |
| gen_key(ExpirationTime, ServerKey)-> |
| crypto:hmac(md5, ServerKey, [ExpirationTime]). |
| |
| -spec gen_hmac(iolist(), binary(), iolist(), binary()) -> binary(). |
| gen_hmac(ExpirationTime, Data, SessionKey, Key) -> |
| crypto:hmac(sha, Key, [ExpirationTime, Data, SessionKey]). |
| |
| -endif. |
| |
| -ifdef(TEST). |
| -include_lib("eunit/include/eunit.hrl"). |
| |
| generate_check_session_cookie_test_() -> |
| {setup, |
| fun setup_server_key/0, |
| fun generate_check_session_cookie/1}. |
| |
| setup_server_key() -> |
| crypto:start(), |
| ["adfasdfasfs",30000]. |
| |
| generate_check_session_cookie([ServerKey, TS]) -> |
| Id = fun (A) -> A end, |
| TSFuture = TS + 1000, |
| TSPast = TS - 1, |
| [?_assertEqual( |
| {true, [TSFuture, "alice"]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, "alice", Id, ServerKey), |
| TS, Id, ServerKey)), |
| ?_assertEqual( |
| {true, [TSFuture, "alice and"]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, "alice and", Id, ServerKey), |
| TS, Id, ServerKey)), |
| ?_assertEqual( |
| {true, [TSFuture, "alice and"]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, "alice and", Id, ServerKey), |
| TS, Id,ServerKey)), |
| ?_assertEqual( |
| {true, [TSFuture, "alice and bob"]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, "alice and bob", |
| Id, ServerKey), |
| TS, Id, ServerKey)), |
| ?_assertEqual( |
| {true, [TSFuture, "alice jlkjfkjsdfg sdkfjgldsjgl"]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, "alice jlkjfkjsdfg sdkfjgldsjgl", |
| Id, ServerKey), |
| TS, Id, ServerKey)), |
| ?_assertEqual( |
| {true, [TSFuture, "alice .'¡'ç+-$%/(&\""]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, "alice .'¡'ç+-$%/(&\"" |
| ,Id, ServerKey), |
| TS, Id, ServerKey)), |
| ?_assertEqual( |
| {true,[TSFuture,"alice456689875"]}, |
| check_session_cookie( |
| generate_session_data(TSFuture, ["alice","456689875"], |
| Id, ServerKey), |
| TS, Id, ServerKey)), |
| ?_assertError( |
| function_clause, |
| check_session_cookie( |
| generate_session_data(TSFuture, {tuple,one}, |
| Id, ServerKey), |
| TS, Id,ServerKey)), |
| ?_assertEqual( |
| {false, [TSPast, "bob"]}, |
| check_session_cookie( |
| generate_session_data(TSPast, "bob", Id,ServerKey), |
| TS, Id, ServerKey)) |
| ]. |
| -endif. |
