rnewson commented on a change in pull request #1176: Implement pluggable authentication and session support for replicator URL: https://github.com/apache/couchdb/pull/1176#discussion_r170089748
########## File path: src/couch_replicator/src/couch_replicator_auth_session.erl ########## @@ -0,0 +1,545 @@ +% Licensed under the Apache License, Version 2.0 (the "License"); you may not +% use this file except in compliance with the License. You may obtain a copy of +% the License at +% +% http://www.apache.org/licenses/LICENSE-2.0 +% +% Unless required by applicable law or agreed to in writing, software +% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT +% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the +% License for the specific language governing permissions and limitations under +% the License. + + +% This is the replicator session auth plugin. It implements session based +% authentication for the replicator. The only public API are the functions from +% the couch_replicator_auth behaviour. Most of the logic and state is in the +% gen_server. An instance of a gen_server could be spawned for the source and +% target endpoints of each replication jobs. +% +% The workflow is roughly this: +% +% * On initialization, try to get a cookie in `refresh/1` If an error occurs, +% the crash. If `_session` endpoint fails with a 404 (not found), return +% `ignore` assuming session authentication is not support or we simply hit a +% non-CouchDb server. +% +% * Before each request, auth framework calls `update_headers` API function. +% Before updating the headers and returning, check if need to refresh again. +% The check looks `next_refresh` time. If that time is set (not `infinity`) +% and just expired, then obtain a new cookie, then update headers and +% return. +% +% * After each request, auth framework calls `handle_response` function. If +% request was successful check if a new cookie was sent by the server in the +% `Set-Cookie` header. If it was then then that becomes the current cookie. +% +% * If last request has an auth failure, check if request used a stale cookie +% In this case nothing is done, and the client is told to retry. Next time +% it updates its headers befor the request it should pick up the latest +% cookie. +% +% * If last request failed and cookie was the latest known cookie, schedule a +% refresh and tell client to retry. However, if the cookie was just updated, +% tell the client to continue such that it will handle the auth failure on +% its own via a set of retries with exponential backoffs. This is it to +% ensure if something goes wrong and one of the endpoints issues invalid +% cookies, replicator won't be stuck in a busy loop refreshing them. + + +-module(couch_replicator_auth_session). + + +-behaviour(couch_replicator_auth). +-behaviour(gen_server). + + +-export([ + initialize/1, + update_headers/2, + handle_response/4, + cleanup/1 +]). + +-export([ + init/1, + terminate/2, + handle_call/3, + handle_cast/2, + handle_info/2, + code_change/3, + format_status/2 +]). + + +-include_lib("ibrowse/include/ibrowse.hrl"). +-include_lib("couch_replicator/include/couch_replicator_api_wrap.hrl"). + + +-type headers() :: [{string(), string()}]. +-type code() :: non_neg_integer(). +-type creds() :: {string() | undefined, string() | undefined}. + + +% Behavior API callbacks + + +-spec initialize(#httpdb{}) -> {ok, #httpdb{}, term()} | ignore. +initialize(#httpdb{} = HttpDb) -> + case remove_creds(HttpDb) of + {ok, User, Pass, HttpDb1} -> + case gen_server:start_link(?MODULE, [User, Pass, HttpDb1], []) of + {ok, Pid} -> + {ok, HttpDb1, {Pid, 0}}; + ignore -> + ignore; + {error, Error} -> + {error, Error} + end; + {error, missing_credentials} -> + ignore; + {error, Error} -> + {error, Error} + end. + + +-spec update_headers(term(), headers()) -> {headers(), term()}. +update_headers({Pid, Epoch}, Headers) -> + Args = {update_headers, Headers, Epoch}, + {Headers1, Epoch1} = gen_server:call(Pid, Args, infinity), + {Headers1, {Pid, Epoch1}}. + + +-spec handle_response(term(), code(), headers(), term()) -> + {continue | retry, term()}. +handle_response({Pid, Epoch}, Code, Headers, Body) -> + Args = {handle_response, Code, Headers, Body, Epoch}, + {Retry, Epoch1} = gen_server:call(Pid, Args, infinity), + {Retry, {Pid, Epoch1}}. + + +-spec cleanup(term()) -> ok. +cleanup({Pid, _Epoch}) -> + gen_server:call(Pid, stop, infinity). + + +%% Definitions + +-define(MIN_UPDATE_INTERVAL, 5). + + +%% gen_server state + +-record(state, { + epoch = 0 :: non_neg_integer(), + cookie :: string() | undefined, + user :: string() | undefined, + pass :: string() | undefined, + httpdb_timeout :: integer(), + httpdb_pool :: pid(), + httpdb_ibrowse_options = [] :: list(), + session_url :: string(), + next_refresh = infinity :: infinity | non_neg_integer(), + refresh_tstamp = 0 :: non_neg_integer() +}). + + +%% gen_server functions + +init([User, Pass, HttpDb]) -> + State = #state{ + user = User, + pass = Pass, + session_url = get_session_url(HttpDb#httpdb.url), + httpdb_pool = HttpDb#httpdb.httpc_pool, + httpdb_timeout = HttpDb#httpdb.timeout, + httpdb_ibrowse_options = HttpDb#httpdb.ibrowse_options + }, + case refresh(State) of + {ok, UpdatedState} -> + {ok, UpdatedState}; + {error, {session_not_supported, _, _}} -> + ignore; + {error, Error} -> + {stop, Error} + end. + + +terminate(_Reason, _State) -> + ok. + + +handle_call({update_headers, Headers, _Epoch}, _From, State) -> + case maybe_refresh(State) of + {ok, State1} -> + Cookie = "AuthSession=" ++ State1#state.cookie, + Headers1 = [{"Cookie", Cookie} | Headers], + {reply, {Headers1, State1#state.epoch}, State1}; + {error, Error} -> + LogMsg = "~p: Stopping session auth plugin because of error ~p", + couch_log:error(LogMsg, [?MODULE, Error]), + {stop, Error, State} + end; + +handle_call({handle_response, Code, Headers, _, Epoch}, _From, State) -> + {Retry, State1} = process_response(Code, Headers, Epoch, State), + {reply, {Retry, State1#state.epoch}, State1}; + +handle_call(stop, _From, State) -> + {stop, normal, ok, State}. + + +handle_cast(Msg, State) -> + couch_log:error("~p: Received un-expected cast ~p", [?MODULE, Msg]), + {noreply, State}. + + +handle_info(Msg, State) -> + couch_log:error("~p : Received un-expected message ~p", [?MODULE, Msg]), + {noreply, State}. + + +code_change(_OldVsn, State, _Extra) -> + {ok, State}. + + +format_status(_Opt, [_PDict, State]) -> + [ + {epoch, State#state.epoch}, + {user, State#state.user}, + {session_url, State#state.session_url}, + {refresh_tstamp, State#state.refresh_tstamp} + ]. + + +%% Private helper functions + +-spec remove_creds(#httpdb{}) -> + {ok, string(), string(), #httpdb{}} | {error, term()}. +remove_creds(#httpdb{url = Url, headers = Headers} = HttpDb) -> + {{HeadersUser, HeadersPass}, HeadersNoCreds} = + couch_replicator_utils:remove_basic_auth_from_headers(Headers), + case remove_creds_from_url(Url) of + {ok, UrlUser, UrlPass, UrlNoCreds} -> + case pick_creds({UrlUser, UrlPass}, {HeadersUser, HeadersPass}) of + {ok, User, Pass} -> + HttpDb1 = HttpDb#httpdb{ + url = UrlNoCreds, + headers = HeadersNoCreds + }, + {ok, User, Pass, HttpDb1}; + {error, Error} -> + {error, Error} + end; + {error, Error} -> + {error, Error} + end. + + +% Credentials could be specified in the url and/or in the headers. +% * If no credentials specified return error. +% * If specified in url but not in headers, pick url creds. +% * Otherwise pick headers creds. +% +-spec pick_creds(creds(), creds()) -> + {ok, string(), string()} | {error, missing_credentials}. +pick_creds({undefined, _}, {undefined, _}) -> + {error, missing_credentials}; +pick_creds({UrlUser, UrlPass}, {undefined, _}) -> + {ok, UrlUser, UrlPass}; +pick_creds({_, _}, {HeadersUser, HeadersPass}) -> + {ok, HeadersUser, HeadersPass}. + + +-spec remove_creds_from_url(string()) -> + {ok, string() | undefined, string() | undefined, string()} | + {error, term()}. +remove_creds_from_url(Url) -> + case ibrowse_lib:parse_url(Url) of + {error, Error} -> + {error, Error}; + #url{username = undefined, password = undefined} -> + {ok, undefined, undefined, Url}; + #url{protocol = Proto, username = User, password = Pass} -> + % Excise user and pass parts from the url. Try to keep the host, + % port and path as they were in the original. + Prefix = lists:concat([Proto, "://", User, ":", Pass, "@"]), + Suffix = lists:sublist(Url, length(Prefix) + 1, length(Url) + 1), + NoCreds = lists:concat([Proto, "://", Suffix]), + {ok, User, Pass, NoCreds} + end. + + +-spec process_response(non_neg_integer(), headers(), + non_neg_integer(), #state{}) -> {retry | continue, #state{}}. +process_response(403, _Headers, Epoch, State) -> + process_auth_failure(Epoch, State); +process_response(401, _Headers, Epoch, State) -> + process_auth_failure(Epoch, State); +process_response(Code, Headers, _Epoch, State) when Code >= 200, Code < 300 -> + % If server noticed cookie is about to time out it can send a new cookie in + % the response headers. Take advantage of that and refresh the cookie. + State1 = case maybe_update_cookie(Headers, State) of + {ok, UpdatedState} -> + UpdatedState; + {error, cookie_not_found} -> + State; + {error, Other} -> + LogMsg = "~p : Could not parse cookie from response headers ~p", + couch_log:error(LogMsg, [?MODULE, Other]), + State + end, + {continue, State1}; +process_response(_Code, _Headers, _Epoch, State) -> + {continue, State}. + + +-spec process_auth_failure(non_neg_integer(), #state{}) -> + {retry | continue, #state{}}. +process_auth_failure(Epoch, #state{epoch = StateEpoch} = State) + when StateEpoch > Epoch -> + % This request used an outdated cookie, tell it to immediately retry + % and it will pick up the current cookie when its headers are updated + {retry, State}; +process_auth_failure(Epoch, #state{epoch = Epoch} = State) -> + MinInterval = min_update_interval(), + case cookie_age_sec(State, now_sec()) of + AgeSec when AgeSec < MinInterval -> + % A recently acquired cookie failed. Schedule a refresh and + % return `continue` to let httpc's retry apply a backoff + {continue, schedule_refresh(now_sec() + MinInterval, State)}; + _AgeSec -> + % Current cookie failed auth. Schedule refresh and ask + % httpc to retry the request. + {retry, schedule_refresh(now_sec(), State)} + end. + + +-spec get_session_url(string()) -> string(). +get_session_url(Url) -> + #url{ + protocol = Proto, + host = Host, + port = Port + } = ibrowse_lib:parse_url(Url), + WithPort = lists:concat([Proto, "://", Host, ":", Port]), + case lists:prefix(WithPort, Url) of + true -> + % Explicit port specified in the original url + WithPort ++ "/_session"; + false -> + % Implicit proto default port was used + lists:concat([Proto, "://", Host, "/_session"]) + end. + + +-spec schedule_refresh(non_neg_integer(), #state{}) -> #state{}. +schedule_refresh(T, #state{next_refresh = Tc} = State) when T < Tc -> + State#state{next_refresh = T}; +schedule_refresh(_, #state{} = State) -> + State. + + +-spec maybe_refresh(#state{}) -> {ok, #state{}} | {error, term()}. +maybe_refresh(#state{next_refresh = T} = State) -> + case now_sec() >= T of + true -> + refresh(State#state{next_refresh = infinity}); + false -> + {ok, State} + end. + + +-spec refresh(#state{}) -> {ok, #state{}} | {error, term()}. +refresh(#state{session_url = Url, user = User, pass = Pass} = State) -> + Body = lists:concat(["name=", User, "&password=", Pass]), + Headers = [{"Content-Type", "application/x-www-form-urlencoded"}], + Result = http_request(State, Url, Headers, post, Body), + http_response(Result, State). + + +-spec http_request(#state{}, string(), headers(), atom(), string()) -> + {ok, string(), headers(), binary()} | {error, term()}. +http_request(#state{httpdb_pool = Pool} = State, Url, Headers, Method, Body) -> + Timeout = State#state.httpdb_timeout, + Opts = [ + {response_format, binary}, + {inactivity_timeout, Timeout} + | State#state.httpdb_ibrowse_options + ], + {ok, Wrk} = couch_replicator_httpc_pool:get_worker(Pool), + try + ibrowse:send_req_direct(Wrk, Url, Headers, Method, Body, Opts, Timeout) + after + ok = couch_replicator_httpc_pool:release_worker(Pool, Wrk) + end. + + +-spec http_response({ok, string(), headers(), binary()} | {error, term()}, + #state{}) -> {ok, #state{}} | {error, term()}. +http_response({ok, "200", Headers, _}, State) -> + maybe_update_cookie(Headers, State); +http_response({ok, "401", _, _}, #state{session_url = Url, user = User}) -> + {error, {session_request_unauthorized, Url, User}}; +http_response({ok, "403", _, _}, #state{session_url = Url, user = User}) -> + {error, {session_request_forbidden, Url, User}}; +http_response({ok, "404", _, _}, #state{session_url = Url, user = User}) -> + {error, {session_not_supported, Url, User}}; +http_response({ok, Code, _, _}, #state{session_url = Url, user = User}) -> + {error, {session_unexpected_result, Code, Url, User}}; +http_response({error, Error}, #state{session_url = Url, user = User}) -> + {error, {session_request_failed, Url, User, Error}}. + + +-spec parse_cookie(list()) -> {ok, string()} | {error, term()}. +parse_cookie(Headers0) -> + Headers = mochiweb_headers:make(Headers0), + case mochiweb_headers:get_value("Set-Cookie", Headers) of + undefined -> + {error, cookie_not_found}; + CookieHeader -> + CookieKVs = mochiweb_cookies:parse_cookie(CookieHeader), + CaseInsKVs = mochiweb_headers:make(CookieKVs), + case mochiweb_headers:get_value("AuthSession", CaseInsKVs) of + undefined -> + {error, cookie_format_invalid}; + Cookie -> + {ok, Cookie} + end + end. + + +-spec maybe_update_cookie(headers(), #state{}) -> + {ok, string()} | {error, term()}. +maybe_update_cookie(ResponseHeaders, State) -> + case parse_cookie(ResponseHeaders) of + {ok, Cookie} -> + {ok, update_cookie(State, Cookie, now_sec())}; + {error, Error} -> + {error, Error} + end. + + +-spec update_cookie(#state{}, string(), non_neg_integer()) -> #state{}. +update_cookie(#state{cookie = Cookie} = State, Cookie, _) -> + State; +update_cookie(#state{epoch = Epoch} = State, Cookie, NowSec) -> + State#state{ + epoch = Epoch + 1, + cookie = Cookie, + refresh_tstamp = NowSec + }. + + +-spec cookie_age_sec(#state{}, non_neg_integer()) -> non_neg_integer(). +cookie_age_sec(#state{refresh_tstamp = RefreshTs}, Now) -> + case Now - RefreshTs of + Diff when Diff >= 0 -> + Diff; + _Diff -> + 0 % In the rare chance time jumps backwards Review comment: `math:max(0, Now - RefreshTs)`? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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