aboutsummaryrefslogtreecommitdiffstats
path: root/lib/ssl/src/ssl_manager.erl
blob: 2b82f18bb59368dd5851703966df3c4315c5da64 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2007-2016. All Rights Reserved.
%%
%% 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.
%%
%% %CopyrightEnd%
%%

%%----------------------------------------------------------------------
%% Purpose: Manages ssl sessions and trusted certifacates
%%----------------------------------------------------------------------

-module(ssl_manager).
-behaviour(gen_server).

%% Internal application API
-export([start_link/1, start_link_dist/1,
	 connection_init/3, cache_pem_file/2,
	 lookup_trusted_cert/4,
	 new_session_id/1, clean_cert_db/2,
	 register_session/2, register_session/3, invalidate_session/2,
	 insert_crls/2, insert_crls/3, delete_crls/1, delete_crls/2, 
	 invalidate_session/3, name/1]).

-export([init_session_validator/1]).

%% gen_server callbacks
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
	 terminate/2, code_change/3]).

-include("ssl_handshake.hrl").
-include("ssl_internal.hrl").
-include_lib("kernel/include/file.hrl").

-record(state, {
	  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	 
	  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).
-define(SESSION_VALIDATION_INTERVAL, 60000).
-define(CLEAN_SESSION_DB, 60000).
-define(CLEAN_CERT_DB, 500).
-define(DEFAULT_MAX_SESSION_CACHE, 1000).
-define(LOAD_MITIGATION, 10).

%%====================================================================
%% API
%%====================================================================

%%--------------------------------------------------------------------
-spec name(normal | dist) -> atom().
%%
%% Description: Returns the registered name of the ssl manager process
%% in the operation modes 'normal' and 'dist'.
%%--------------------------------------------------------------------
name(normal) ->
    ?MODULE;
name(dist) ->
    list_to_atom(atom_to_list(?MODULE) ++ "dist").

%%--------------------------------------------------------------------
-spec start_link(list()) -> {ok, pid()} | ignore | {error, term()}.
%%
%% Description: Starts the ssl manager that takes care of sessions
%% and certificate caching.
%%--------------------------------------------------------------------
start_link(Opts) ->
    MangerName = name(normal),
    CacheName = ssl_pem_cache:name(normal),
    gen_server:start_link({local, MangerName}, 
			  ?MODULE, [MangerName, CacheName, Opts], []).

%%--------------------------------------------------------------------
-spec start_link_dist(list()) -> {ok, pid()} | ignore | {error, term()}.
%%
%% Description: Starts a special instance of the ssl manager to
%% be used by the erlang distribution. Note disables soft upgrade!
%%--------------------------------------------------------------------
start_link_dist(Opts) ->
    DistMangerName = name(dist),
    DistCacheName = ssl_pem_cache:name(dist),
    gen_server:start_link({local, DistMangerName}, 
			  ?MODULE, [DistMangerName, DistCacheName, Opts], []).

%%--------------------------------------------------------------------
-spec connection_init(binary()| {der, list()}, client | server, 
		      {Cb :: atom(), Handle:: term()}) ->
			     {ok, map()}.
%%			     
%% Description: Do necessary initializations for a new connection.
%%--------------------------------------------------------------------
connection_init({der, _} = Trustedcerts, Role, CRLCache) ->
    {ok, Extracted} = ssl_pkix_db:extract_trusted_certs(Trustedcerts),
    call({connection_init, Extracted, Role, CRLCache});
connection_init(Trustedcerts, Role, CRLCache) ->
    call({connection_init, Trustedcerts, Role, CRLCache}).

%%--------------------------------------------------------------------
-spec cache_pem_file(binary(), term()) -> {ok, term()} | {error, reason()}.
%%		    
%% Description: Cache a pem file and return its content.
%%--------------------------------------------------------------------
cache_pem_file(File, DbHandle) ->
    case ssl_pkix_db:lookup(File, DbHandle) of
	[Content]  ->
	    {ok, Content};
	undefined ->
            ssl_pem_cache:insert(File)
    end.

%%--------------------------------------------------------------------
-spec lookup_trusted_cert(term(), reference(), serialnumber(), issuer()) ->
				 undefined | 
				 {ok, {der_cert(), #'OTPCertificate'{}}}.
%%				 
%% Description: Lookup the trusted cert with Key = {reference(),
%% serialnumber(), issuer()}.
%% --------------------------------------------------------------------
lookup_trusted_cert(DbHandle, Ref, SerialNumber, Issuer) ->
    ssl_pkix_db:lookup_trusted_cert(DbHandle, Ref, SerialNumber, Issuer).

%%--------------------------------------------------------------------
-spec new_session_id(integer()) -> session_id().
%%
%% Description: Creates a session id for the server.
%%--------------------------------------------------------------------
new_session_id(Port) ->
    call({new_session_id, Port}).

%%--------------------------------------------------------------------
-spec clean_cert_db(reference(), binary()) -> ok.
%%
%% Description: Send clean request of cert db to ssl_manager process should
%% 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}),
    ok.

%%--------------------------------------------------------------------
%%
%% Description: Make the session available for reuse.
%%--------------------------------------------------------------------
-spec register_session(host(), inet:port_number(), #session{}) -> ok.
register_session(Host, Port, Session) ->
    cast({register_session, Host, Port, Session}).

-spec register_session(inet:port_number(), #session{}) -> ok.
register_session(Port, Session) ->
    cast({register_session, Port, Session}).
%%--------------------------------------------------------------------
%%
%% Description: Make the session unavailable for reuse. After
%% a the session has been marked "is_resumable = false" for some while
%% it will be safe to remove the data from the session database.
%%--------------------------------------------------------------------
-spec invalidate_session(host(), inet:port_number(), #session{}) -> ok.
invalidate_session(Host, Port, Session) ->
    load_mitigation(),
    cast({invalidate_session, Host, Port, Session}).

-spec invalidate_session(inet:port_number(), #session{}) -> ok.
invalidate_session(Port, Session) ->
    load_mitigation(),
    cast({invalidate_session, Port, Session}).

insert_crls(Path, CRLs)->
    insert_crls(Path, CRLs, normal).
insert_crls(?NO_DIST_POINT_PATH = Path, CRLs, ManagerType)->
    put(ssl_manager, name(ManagerType)),
    cast({insert_crls, Path, CRLs});
insert_crls(Path, CRLs, ManagerType)->
    put(ssl_manager, name(ManagerType)),
    call({insert_crls, Path, CRLs}).

delete_crls(Path)->
    delete_crls(Path, normal).
delete_crls(?NO_DIST_POINT_PATH = Path, ManagerType)->
    put(ssl_manager, name(ManagerType)),
    cast({delete_crls, Path});
delete_crls(Path, ManagerType)->
    put(ssl_manager, name(ManagerType)),
    call({delete_crls, Path}).

%%====================================================================
%% gen_server callbacks
%%====================================================================

%%--------------------------------------------------------------------
-spec init(list()) -> {ok, #state{}}.
%% Possible return values not used now. 
%% |  {ok, #state{}, timeout()} | ignore | {stop, term()}.		  
%%
%% Description: Initiates the server
%%--------------------------------------------------------------------
init([ManagerName, PemCacheName, Opts]) ->
    put(ssl_manager, ManagerName),
    put(ssl_pem_cache, PemCacheName),
    process_flag(trap_exit, true),
    CacheCb = proplists:get_value(session_cb, Opts, ssl_session_cache),
    SessionLifeTime =  
	proplists:get_value(session_lifetime, Opts, ?'24H_in_sec'),
    CertDb = ssl_pkix_db:create(PemCacheName),
    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),
    {ok, #state{certificate_db = CertDb,
		session_cache_client = ClientSessionCache,
		session_cache_server = ServerSessionCache,
		session_cache_cb = CacheCb,
		session_lifetime = SessionLifeTime,
		session_validation_timer = Timer,
		session_cache_client_max = 
		    max_session_cache_size(session_cache_client_max),
		session_cache_server_max = 
		    max_session_cache_size(session_cache_server_max),
		session_client_invalidator = undefined,
		session_server_invalidator = undefined
	       }}.

%%--------------------------------------------------------------------
-spec handle_call(msg(), from(), #state{}) -> {reply, reply(), #state{}}. 
%% Possible return values not used now.  
%%					      {reply, reply(), #state{}, timeout()} |
%%					      {noreply, #state{}} |
%%					      {noreply, #state{}, timeout()} |
%%					      {stop, reason(), reply(), #state{}} |
%%					      {stop, reason(), #state{}}.
%%
%% Description: Handling call messages
%%--------------------------------------------------------------------
handle_call({{connection_init, <<>>, Role, {CRLCb, UserCRLDb}}, _Pid}, _From,
	    #state{certificate_db = [CertDb, FileRefDb, PemChace | _] = Db} = State) ->
    Ref = make_ref(), 
    {reply, {ok, #{cert_db_ref => Ref, 
                   cert_db_handle => CertDb, 
                   fileref_db_handle => FileRefDb, 
                   pem_cache => PemChace, 
                   session_cache => session_cache(Role, State), 
                   crl_db_info => {CRLCb, crl_db_info(Db, UserCRLDb)}}}, State};

handle_call({{connection_init, Trustedcerts, Role, {CRLCb, UserCRLDb}}, Pid}, _From,
	    #state{certificate_db = [CertDb, FileRefDb, PemChace | _] = Db} = State) ->
    case add_trusted_certs(Pid, Trustedcerts, Db) of
	{ok, Ref} ->
	    {reply, {ok, #{cert_db_ref => Ref, 
                           cert_db_handle => CertDb, 
                           fileref_db_handle => FileRefDb, 
                           pem_cache => PemChace, 
                           session_cache => session_cache(Role, State), 
                           crl_db_info => {CRLCb, crl_db_info(Db, UserCRLDb)}}}, State};
        {error, _} = Error ->
            {reply, Error, State}
    end;

handle_call({{insert_crls, Path, CRLs}, _}, _From,   
	    #state{certificate_db = Db} = State) ->
    ssl_pkix_db:add_crls(Db, Path, CRLs),
    {reply, ok, State};

handle_call({{delete_crls, CRLsOrPath}, _}, _From,   
	    #state{certificate_db = Db} = State) ->
    ssl_pkix_db:remove_crls(Db, CRLsOrPath),
    {reply, ok, State};

handle_call({{new_session_id, Port}, _},
	    _, #state{session_cache_cb = CacheCb,
		      session_cache_server = Cache} = State) ->
    Id = new_id(Port, ?GEN_UNIQUE_ID_MAX_TRIES, Cache, CacheCb),
    {reply, Id, State}.

%%--------------------------------------------------------------------
-spec  handle_cast(msg(), #state{}) -> {noreply, #state{}}.
%% Possible return values not used now.  
%%				      | {noreply, #state{}, timeout()} |
%%				       {stop, reason(), #state{}}.
%%
%% Description: Handling cast messages
%%--------------------------------------------------------------------
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}, State0) ->    
    State = server_register_session(Port, Session, State0), 		       
    {noreply, State};

handle_cast({invalidate_session, Host, Port,
	     #session{session_id = ID} = Session},
	    #state{session_cache_client = Cache,
		   session_cache_cb = CacheCb} = State) ->
    invalidate_session(Cache, CacheCb, {{Host, Port}, ID}, Session, State);

handle_cast({invalidate_session, Port, #session{session_id = ID} = Session},
	    #state{session_cache_server = Cache,
		   session_cache_cb = CacheCb} = State) ->
    invalidate_session(Cache, CacheCb, {Port, ID}, Session, State);


handle_cast({insert_crls, Path, CRLs},   
	    #state{certificate_db = Db} = State) ->
    ssl_pkix_db:add_crls(Db, Path, CRLs),
    {noreply, State};

handle_cast({delete_crls, CRLsOrPath},   
	    #state{certificate_db = Db} = State) ->
    ssl_pkix_db:remove_crls(Db, CRLsOrPath),
    {noreply, State}.

%%--------------------------------------------------------------------
-spec handle_info(msg(), #state{}) -> {noreply, #state{}}.
%% Possible return values not used now.
%%				      |{noreply, #state{}, timeout()} |
%%				      {stop, reason(), #state{}}.
%%
%% Description: Handling all non call/cast messages
%%-------------------------------------------------------------------
handle_info(validate_sessions, #state{session_cache_cb = CacheCb,
				      session_cache_client = ClientCache,
				      session_cache_server = ServerCache,
				      session_lifetime = LifeTime,
				      session_client_invalidator = Client,
				      session_server_invalidator = Server				      
				     } = State) ->
    Timer = erlang:send_after(?SESSION_VALIDATION_INTERVAL, 
			      self(), validate_sessions),
    CPid = start_session_validator(ClientCache, CacheCb, LifeTime, Client),
    SPid = start_session_validator(ServerCache, CacheCb, LifeTime, Server),
    {noreply, State#state{session_validation_timer = Timer, 
			  session_client_invalidator = CPid,
			  session_server_invalidator = SPid}};


handle_info({delayed_clean_session, Key, Cache}, #state{session_cache_cb = CacheCb
						       } = State) ->
    CacheCb:delete(Cache, Key),
    {noreply, State};

handle_info({clean_cert_db, Ref, File},
	    #state{certificate_db = [CertDb, {RefDb, FileMapDb} | _]} = State) ->
    
    case ssl_pkix_db:lookup(Ref, RefDb) of
	undefined -> %% Alredy cleaned
	    ok;
	_ ->
	    clean_cert_db(Ref, CertDb, RefDb, FileMapDb, File)
    end,
    {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}.

%%--------------------------------------------------------------------
-spec terminate(reason(), #state{}) -> ok.
%%		       
%% Description: This function is called by a gen_server when it is about to
%% terminate. It should be the opposite of Module:init/1 and do any necessary
%% cleaning up. When it returns, the gen_server terminates with Reason.
%% The return value is ignored.
%%--------------------------------------------------------------------
terminate(_Reason, #state{certificate_db = Db,
			  session_cache_client = ClientSessionCache,
			  session_cache_server = ServerSessionCache,
			  session_cache_cb = CacheCb,
			  session_validation_timer = Timer}) ->
    erlang:cancel_timer(Timer),
    ssl_pkix_db:remove(Db),
    catch CacheCb:terminate(ClientSessionCache),
    catch CacheCb:terminate(ServerSessionCache),
    ok.

%%--------------------------------------------------------------------
-spec code_change(term(), #state{}, list()) -> {ok, #state{}}.			 
%%
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, State, _Extra) ->
    {ok, State}.

%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
call(Msg) ->
    gen_server:call(get(ssl_manager), {Msg, self()}, infinity).

cast(Msg) ->
    gen_server:cast(get(ssl_manager), Msg).
 
validate_session(Host, Port, Session, LifeTime) ->
    case ssl_session:valid_session(Session, LifeTime) of
	true ->
	    ok;
	false ->
	    invalidate_session(Host, Port, Session)
    end.

validate_session(Port, Session, LifeTime) ->
    case ssl_session:valid_session(Session, LifeTime) of
	true ->
	    ok;
	false ->
	    invalidate_session(Port, Session)
    end.
		    
start_session_validator(Cache, CacheCb, LifeTime, undefined) ->
    spawn_link(?MODULE, init_session_validator, 
	       [[get(ssl_manager), Cache, CacheCb, LifeTime]]);
start_session_validator(_,_,_, Pid) ->
    Pid.

init_session_validator([SslManagerName, Cache, CacheCb, LifeTime]) ->
    put(ssl_manager, SslManagerName),
    CacheCb:foldl(fun session_validation/2,
		  LifeTime, Cache).

session_validation({{{Host, Port}, _}, Session}, LifeTime) ->
    validate_session(Host, Port, Session, LifeTime),
    LifeTime;
session_validation({{Port, _}, Session}, LifeTime) ->
    validate_session(Port, Session, LifeTime),
    LifeTime.

delay_time() ->
    case application:get_env(ssl, session_delay_cleanup_time) of
	{ok, Time} when is_integer(Time) ->
	    Time;
	_ ->
	   ?CLEAN_SESSION_DB
    end.

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};
	_ ->
	    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}) ->
    {TRef, LastClient}.

%% If we can not generate a not allready in use session ID in
%% ?GEN_UNIQUE_ID_MAX_TRIES we make the new session uncacheable The
%% value of ?GEN_UNIQUE_ID_MAX_TRIES is stolen from open SSL which
%% states : "If we can not find a session id in
%% ?GEN_UNIQUE_ID_MAX_TRIES either the RAND code is broken or someone
%% is trying to open roughly very close to 2^128 (or 2^256) SSL
%% sessions to our server"
new_id(_, 0, _, _) ->
    <<>>;
new_id(Port, Tries, Cache, CacheCb) ->
    Id = ssl_cipher:random_bytes(?NUM_OF_SESSION_ID_BYTES),
    case CacheCb:lookup(Cache, {Port, Id}) of
	undefined ->
	    Now = erlang:monotonic_time(),
	    %% New sessions can not be set to resumable
	    %% until handshake is compleate and the
	    %% other session values are set.
	    CacheCb:update(Cache, {Port, Id}, #session{session_id = Id,
						       is_resumable = new,
						       time_stamp = Now}),
	    Id;
	_ ->
	    new_id(Port, Tries - 1, Cache, CacheCb)
    end.

clean_cert_db(Ref, CertDb, RefDb, FileMapDb, File) ->
    case ssl_pkix_db:ref_count(Ref, RefDb, 0) of
	0 ->	  
	    ssl_pkix_db:remove(Ref, RefDb),
	    ssl_pkix_db:remove(File, FileMapDb),
	    ssl_pkix_db:remove_trusted_certs(Ref, CertDb);
	_ ->
	    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
	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, 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 ->
	    State;
	false ->
	    Pid = do_register_session({PartialKey, 
				       Session#session.session_id}, 
				      Session, Max, Pid0, Cache, CacheCb),
	    State#state{session_client_invalidator = Pid}
    end.

exists_equivalent(_, []) ->
    false;
exists_equivalent(#session{
		     peer_certificate = PeerCert,
		     own_certificate = OwnCert,
		     compression_method = Compress,
		     cipher_suite = CipherSuite,
		     srp_username = SRP,
		     ecc = ECC} , 
		  [#session{
		      peer_certificate = PeerCert,
		      own_certificate = OwnCert,
		      compression_method = Compress,
		      cipher_suite = CipherSuite,
		      srp_username = SRP,
		      ecc = ECC} | _]) ->
    true;
exists_equivalent(Session, [ _ | Rest]) ->
    exists_equivalent(Session, Rest).

add_trusted_certs(Pid, Trustedcerts, Db) ->
    try
	ssl_pkix_db:add_trusted_certs(Pid, Trustedcerts, Db) 	    
    catch
	_:Reason ->
	    {error, Reason}
    end.

session_cache(client, #state{session_cache_client = Cache}) ->
    Cache;
session_cache(server, #state{session_cache_server = Cache}) ->
    Cache.

crl_db_info([_,_,_,Local], {internal, Info}) ->
    {Local, 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()}, undefined);
invalidate_session_cache(Pid, _CacheCb, _Cache) ->
    Pid.

load_mitigation() ->
    MSec = rand:uniform(?LOAD_MITIGATION),
    receive 
    after 
	MSec ->
	    continue
    end.