ssl: Add upper limit for session cache

If upper limit is reached invalidate the current cache entries, e.i the session
lifetime is the max time a session will be keept, but it may be invalidated
earlier if the max limit for the table is reached. This will keep the ssl
manager process well behaved, not exhusting memeory. Invalidating the entries
will incrementally empty the cache to make room for fresh sessions entries.

4 files changed, 138 insertions, 59 deletions

diff --git a/lib/ssl/src/ssl_manager.erl b/lib/ssl/src/ssl_manager.erl
index 9e535104f7..00e95f5c5b 100644
--- a/lib/ssl/src/ssl_manager.erl
+++ b/lib/ssl/src/ssl_manager.erl
@@ -46,15 +46,19 @@
 -include_lib("kernel/include/file.hrl").
 
 -record(state, {
-	  session_cache_client,
-	  session_cache_server,
-	  session_cache_cb,
-	  session_lifetime,
-	  certificate_db,
-	  session_validation_timer,
+	  session_cache_client    :: db_handle(),
+	  session_cache_server    :: db_handle(),
+	  session_cache_cb        :: atom(),
+	  session_lifetime        :: integer(),
+	  certificate_db          :: db_handle(),
+	  session_validation_timer :: reference(),
 	  last_delay_timer  = {undefined, undefined},%% Keep for testing purposes
-	  last_pem_check,
-	  clear_pem_cache 
+	  last_pem_check             :: erlang:timestamp(),
+	  clear_pem_cache            :: integer(),
+	  session_cache_client_max   :: integer(),
+	  session_cache_server_max   :: integer(),
+	  session_server_invalidator :: undefined | pid(),
+	  session_client_invalidator :: undefined | pid()
 	 }).
 
 -define(GEN_UNIQUE_ID_MAX_TRIES, 10).
@@ -62,7 +66,7 @@
 -define(CLEAR_PEM_CACHE, 120000).
 -define(CLEAN_SESSION_DB, 60000).
 -define(CLEAN_CERT_DB, 500).
--define(NOT_TO_BIG, 10).
+-define(DEFAULT_MAX_SESSION_CACHE, 1000).
 
 %%====================================================================
 %% API
@@ -87,7 +91,8 @@ manager_name(dist) ->
 %%--------------------------------------------------------------------
 start_link(Opts) ->
     DistMangerName = manager_name(normal),
-    gen_server:start_link({local, DistMangerName}, ?MODULE, [DistMangerName, Opts], []).
+    gen_server:start_link({local, DistMangerName}, 
+			  ?MODULE, [DistMangerName, Opts], []).
 
 %%--------------------------------------------------------------------
 -spec start_link_dist(list()) -> {ok, pid()} | ignore | {error, term()}.
@@ -97,7 +102,8 @@ start_link(Opts) ->
 %%--------------------------------------------------------------------
 start_link_dist(Opts) ->
     DistMangerName = manager_name(dist),
-    gen_server:start_link({local, DistMangerName}, ?MODULE, [DistMangerName, Opts], []).
+    gen_server:start_link({local, DistMangerName}, 
+			  ?MODULE, [DistMangerName, Opts], []).
 
 %%--------------------------------------------------------------------
 -spec connection_init(binary()| {der, list()}, client | server, 
@@ -167,7 +173,8 @@ new_session_id(Port) ->
 %% be called by ssl-connection processes. 
 %%--------------------------------------------------------------------
 clean_cert_db(Ref, File) ->
-    erlang:send_after(?CLEAN_CERT_DB, get(ssl_manager), {clean_cert_db, Ref, File}),
+    erlang:send_after(?CLEAN_CERT_DB, get(ssl_manager), 
+		      {clean_cert_db, Ref, File}),
     ok.
 
 %%--------------------------------------------------------------------
@@ -235,10 +242,12 @@ init([Name, Opts]) ->
     SessionLifeTime =  
 	proplists:get_value(session_lifetime, Opts, ?'24H_in_sec'),
     CertDb = ssl_pkix_db:create(),
-    ClientSessionCache = CacheCb:init([{role, client} | 
-				       proplists:get_value(session_cb_init_args, Opts, [])]),
-    ServerSessionCache = CacheCb:init([{role, server} | 
-				       proplists:get_value(session_cb_init_args, Opts, [])]),
+    ClientSessionCache = 
+	CacheCb:init([{role, client} | 
+		      proplists:get_value(session_cb_init_args, Opts, [])]),
+    ServerSessionCache = 
+	CacheCb:init([{role, server} | 
+		      proplists:get_value(session_cb_init_args, Opts, [])]),
     Timer = erlang:send_after(SessionLifeTime * 1000 + 5000, 
 			      self(), validate_sessions),
     Interval = pem_check_interval(),
@@ -250,7 +259,11 @@ init([Name, Opts]) ->
 		session_lifetime = SessionLifeTime,
 		session_validation_timer = Timer,
 		last_pem_check =  os:timestamp(),
-		clear_pem_cache = Interval 	
+		clear_pem_cache = Interval, 	
+		session_cache_client_max = 
+		    max_session_cache_size(session_cache_client_max),
+		session_cache_server_max = 
+		    max_session_cache_size(session_cache_server_max)
 	       }}.
 
 %%--------------------------------------------------------------------
@@ -267,7 +280,8 @@ init([Name, Opts]) ->
 handle_call({{connection_init, <<>>, Role, {CRLCb, UserCRLDb}}, _Pid}, _From,
 	    #state{certificate_db = [CertDb, FileRefDb, PemChace | _] = Db} = State) ->
     Ref = make_ref(), 
-    Result = {ok, Ref, CertDb, FileRefDb, PemChace, session_cache(Role, State), {CRLCb, crl_db_info(Db, UserCRLDb)}},
+    Result = {ok, Ref, CertDb, FileRefDb, PemChace, 
+	      session_cache(Role, State), {CRLCb, crl_db_info(Db, UserCRLDb)}},
     {reply, Result, State#state{certificate_db = Db}};
 
 handle_call({{connection_init, Trustedcerts, Role, {CRLCb, UserCRLDb}}, Pid}, _From,
@@ -305,7 +319,8 @@ handle_call({{cache_pem,File}, _Pid}, _,
 	_:Reason ->
 	    {reply, {error, Reason}, State}
     end;
-handle_call({unconditionally_clear_pem_cache, _},_, #state{certificate_db = [_,_,PemChace | _]} = State) ->
+handle_call({unconditionally_clear_pem_cache, _},_, 
+	    #state{certificate_db = [_,_,PemChace | _]} = State) ->
     ssl_pkix_db:clear(PemChace),
     {reply, ok,  State}.
 
@@ -317,27 +332,12 @@ handle_call({unconditionally_clear_pem_cache, _},_, #state{certificate_db = [_,_
 %%
 %% Description: Handling cast messages
 %%--------------------------------------------------------------------
-handle_cast({register_session, Host, Port, Session}, 
-	    #state{session_cache_client = Cache,
-		   session_cache_cb = CacheCb} = State) ->
-    TimeStamp = erlang:monotonic_time(),
-    NewSession = Session#session{time_stamp = TimeStamp},
-    
-    case CacheCb:select_session(Cache, {Host, Port}) of
-	no_session ->
-	    CacheCb:update(Cache, {{Host, Port}, 
-				   NewSession#session.session_id}, NewSession);
-	Sessions ->
-	    register_unique_session(Sessions, NewSession, CacheCb, Cache, {Host, Port})
-    end,
+handle_cast({register_session, Host, Port, Session}, State0) ->
+    State = ssl_client_register_session(Host, Port, Session, State0), 
     {noreply, State};
 
-handle_cast({register_session, Port, Session},  
-	    #state{session_cache_server = Cache,
-		   session_cache_cb = CacheCb} = State) ->    
-    TimeStamp =  erlang:monotonic_time(),
-    NewSession = Session#session{time_stamp = TimeStamp},
-    CacheCb:update(Cache, {Port, NewSession#session.session_id}, NewSession),
+handle_cast({register_session, Port, Session}, State0) ->    
+    State = server_register_session(Port, Session, State0), 		       
     {noreply, State};
 
 handle_cast({invalidate_session, Host, Port,
@@ -411,10 +411,10 @@ handle_info({clean_cert_db, Ref, File},
     end,
     {noreply, State};
 
-handle_info({'EXIT', _, _}, State) ->
-    %% Session validator died!! Do we need to take any action?
-    %% maybe error log
-    {noreply, State};
+handle_info({'EXIT', Pid, _}, #state{session_client_invalidator = Pid} = State) ->
+    {noreply, State#state{session_client_invalidator = undefined}};
+handle_info({'EXIT', Pid, _}, #state{session_server_invalidator = Pid} = State) ->
+    {noreply, State#state{session_server_invalidator = undefined}};
 
 handle_info(_Info, State) ->
     {noreply, State}.
@@ -495,23 +495,39 @@ delay_time() ->
 	   ?CLEAN_SESSION_DB
     end.
 
-invalidate_session(Cache, CacheCb, Key, Session, #state{last_delay_timer = LastTimer} = State) ->
+max_session_cache_size(CacheType) ->
+    case application:get_env(ssl, CacheType) of
+	{ok, Size} when is_integer(Size) ->
+	    Size;
+	_ ->
+	   ?DEFAULT_MAX_SESSION_CACHE
+    end.
+
+invalidate_session(Cache, CacheCb, Key, Session, State) ->
     case CacheCb:lookup(Cache, Key) of
 	undefined -> %% Session is already invalidated
 	    {noreply, State};
 	#session{is_resumable = new} ->
 	    CacheCb:delete(Cache, Key),
 	    {noreply, State};
-	_ -> 
-	    %% When a registered session is invalidated we need to wait a while before deleting
-	    %% it as there might be pending connections that rightfully needs to look
-	    %% up the session data but new connections should not get to use this session.
-	    CacheCb:update(Cache, Key, Session#session{is_resumable = false}),
-	    TRef =
-		erlang:send_after(delay_time(), self(), {delayed_clean_session, Key, Cache}),
-	    {noreply, State#state{last_delay_timer = last_delay_timer(Key, TRef, LastTimer)}}
+	_ ->
+	    delayed_invalidate_session(CacheCb, Cache, Key, Session, State)
     end.
 
+delayed_invalidate_session(CacheCb, Cache, Key, Session, 
+			   #state{last_delay_timer = LastTimer} = State) ->
+    %% When a registered session is invalidated we need to
+    %% wait a while before deleting it as there might be
+    %% pending connections that rightfully needs to look up
+    %% the session data but new connections should not get to
+    %% use this session.
+    CacheCb:update(Cache, Key, Session#session{is_resumable = false}),
+    TRef =
+	erlang:send_after(delay_time(), self(), 
+			  {delayed_clean_session, Key, Cache}),
+    {noreply, State#state{last_delay_timer = 
+			      last_delay_timer(Key, TRef, LastTimer)}}.
+
 last_delay_timer({{_,_},_}, TRef, {LastServer, _}) ->
     {LastServer, TRef};
 last_delay_timer({_,_}, TRef, {_, LastClient}) ->
@@ -535,7 +551,7 @@ new_id(Port, Tries, Cache, CacheCb) ->
 	    %% until handshake is compleate and the
 	    %% other session values are set.
 	    CacheCb:update(Cache, {Port, Id}, #session{session_id = Id,
-						       is_resumable = false,
+						       is_resumable = new,
 						       time_stamp = Now}),
 	    Id;
 	_ ->
@@ -557,15 +573,62 @@ clean_cert_db(Ref, CertDb, RefDb, PemCache, File) ->
 	    ok
     end.
 
+ssl_client_register_session(Host, Port, Session, #state{session_cache_client = Cache,
+							session_cache_cb = CacheCb,
+							session_cache_client_max = Max,
+							session_client_invalidator = Pid0} = State) ->
+    TimeStamp = erlang:monotonic_time(),
+    NewSession = Session#session{time_stamp = TimeStamp},
+    
+    case CacheCb:select_session(Cache, {Host, Port}) of
+	no_session ->
+	    Pid = do_register_session({{Host, Port}, 
+				     NewSession#session.session_id}, 
+				      NewSession, Max, Pid0, Cache, CacheCb),
+	    State#state{session_client_invalidator = Pid};
+	Sessions ->
+	    register_unique_session(Sessions, NewSession, {Host, Port}, State)
+    end.
+
+server_register_session(Port, Session, #state{session_cache_server_max = Max,
+					      session_cache_server = Cache,
+					      session_cache_cb = CacheCb,
+					      session_server_invalidator = Pid0} = State) ->
+    TimeStamp =  erlang:monotonic_time(),
+    NewSession = Session#session{time_stamp = TimeStamp},
+    Pid = do_register_session({Port, NewSession#session.session_id}, 
+			      NewSession, Max, Pid0, Cache, CacheCb),
+    State#state{session_server_invalidator = Pid}.
+
+do_register_session(Key, Session, Max, Pid, Cache, CacheCb) ->
+    try CacheCb:size(Cache) of
+	N when N > Max  ->
+	  invalidate_session_cache(Pid, CacheCb, Cache);
+	_ ->	
+	    CacheCb:update(Cache, Key, Session),
+	    Pid
+    catch 
+	error:undef ->
+	    CacheCb:update(Cache, Key, Session),
+            Pid		
+    end.
+
+
 %% Do not let dumb clients create a gigantic session table
 %% for itself creating big delays at connection time. 
-register_unique_session(Sessions, Session, CacheCb, Cache, PartialKey) ->
+register_unique_session(Sessions, Session, PartialKey, 
+			#state{session_cache_client_max = Max,
+			       session_cache_client = Cache,
+			       session_cache_cb = CacheCb,
+			       session_client_invalidator = Pid0} = State) ->
     case exists_equivalent(Session , Sessions) of
 	true ->
-	    ok;
+	    State;
 	false ->
-	    CacheCb:update(Cache, {PartialKey, 
-				   Session#session.session_id}, Session)
+	    Pid = do_register_session({PartialKey, 
+				       Session#session.session_id}, 
+				      Session, Max, Pid0, Cache, CacheCb),
+	    State#state{session_client_invalidator = Pid}
     end.
 
 exists_equivalent(_, []) ->
@@ -620,7 +683,8 @@ pem_check_interval() ->
     end.
 	
 is_before_checkpoint(Time, CheckPoint) ->
-    calendar:datetime_to_gregorian_seconds(calendar:now_to_datetime(CheckPoint)) -
+    calendar:datetime_to_gregorian_seconds(
+      calendar:now_to_datetime(CheckPoint)) -
     calendar:datetime_to_gregorian_seconds(Time) > 0.
 
 add_trusted_certs(Pid, Trustedcerts, Db) ->
@@ -641,3 +705,9 @@ crl_db_info([_,_,_,Local], {internal, Info}) ->
 crl_db_info(_, UserCRLDb) ->
     UserCRLDb.
 
+%% Only start a session invalidator if there is not
+%% one already active
+invalidate_session_cache(undefined, CacheCb, Cache) ->
+    start_session_validator(Cache, CacheCb, {invalidate_before, erlang:monotonic_time()});
+invalidate_session_cache(Pid, _CacheCb, _Cache) ->
+    Pid.
diff --git a/lib/ssl/src/ssl_session.erl b/lib/ssl/src/ssl_session.erl
index 0ee8a096e9..2b24bff5ff 100644
--- a/lib/ssl/src/ssl_session.erl
+++ b/lib/ssl/src/ssl_session.erl
@@ -61,10 +61,12 @@ client_id(ClientInfo, Cache, CacheCb, OwnCert) ->
 	    SessionId
     end.
 
--spec valid_session(#session{}, seconds()) -> boolean().
+-spec valid_session(#session{}, seconds() | {invalidate_before, integer()}) -> boolean().
 %%
 %% Description: Check that the session has not expired
 %%--------------------------------------------------------------------
+valid_session(#session{time_stamp = TimeStamp}, {invalidate_before, Before}) ->
+    TimeStamp > Before;
 valid_session(#session{time_stamp = TimeStamp}, LifeTime) ->
     Now = erlang:monotonic_time(),
     Lived = erlang:convert_time_unit(Now-TimeStamp, native, seconds),
diff --git a/lib/ssl/src/ssl_session_cache.erl b/lib/ssl/src/ssl_session_cache.erl
index cfc48cd935..9585e613e6 100644
--- a/lib/ssl/src/ssl_session_cache.erl
+++ b/lib/ssl/src/ssl_session_cache.erl
@@ -27,7 +27,7 @@
 -include("ssl_internal.hrl").
 
 -export([init/1, terminate/1, lookup/2, update/3, delete/2, foldl/3, 
-	 select_session/2]). 
+	 select_session/2, size/1]). 
 
 %%--------------------------------------------------------------------
 %% Description: Return table reference. Called by ssl_manager process. 
@@ -86,6 +86,12 @@ select_session(Cache, PartialKey) ->
 	       [{{{PartialKey,'_'}, '$1'},[],['$1']}]).
 
 %%--------------------------------------------------------------------
+%% Description: Returns the cache size
+%%--------------------------------------------------------------------
+size(Cache) ->
+    ets:info(Cache, size).
+
+%%--------------------------------------------------------------------
 %%% Internal functions
 %%--------------------------------------------------------------------
 cache_name(Name) ->
diff --git a/lib/ssl/src/ssl_session_cache_api.erl b/lib/ssl/src/ssl_session_cache_api.erl
index 536b52c44b..8f62c25be5 100644
--- a/lib/ssl/src/ssl_session_cache_api.erl
+++ b/lib/ssl/src/ssl_session_cache_api.erl
@@ -33,3 +33,4 @@
 -callback delete(db_handle(), key()) -> any().
 -callback foldl(fun(), term(), db_handle()) -> term().
 -callback select_session(db_handle(), {host(), inet:port_number()} | inet:port_number()) -> [#session{}].
+-callback size(db_handle()) -> integer().