aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/curl/lib/vtls/vtls.c
blob: 9dee5aa3b38ef77908343bc5954868e55fa9725e (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
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2022, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/

/* This file is for implementing all "generic" SSL functions that all libcurl
   internals should use. It is then responsible for calling the proper
   "backend" function.

   SSL-functions in libcurl should call functions in this source file, and not
   to any specific SSL-layer.

   Curl_ssl_ - prefix for generic ones

   Note that this source code uses the functions of the configured SSL
   backend via the global Curl_ssl instance.

   "SSL/TLS Strong Encryption: An Introduction"
   https://httpd.apache.org/docs/2.0/ssl/ssl_intro.html
*/

#include "curl_setup.h"

#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
#ifdef HAVE_SYS_STAT_H
#include <sys/stat.h>
#endif
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

#include "urldata.h"

#include "vtls.h" /* generic SSL protos etc */
#include "slist.h"
#include "sendf.h"
#include "strcase.h"
#include "url.h"
#include "progress.h"
#include "share.h"
#include "multiif.h"
#include "timeval.h"
#include "curl_md5.h"
#include "warnless.h"
#include "curl_base64.h"
#include "curl_printf.h"
#include "strdup.h"

/* The last #include files should be: */
#include "curl_memory.h"
#include "memdebug.h"

/* convenience macro to check if this handle is using a shared SSL session */
#define SSLSESSION_SHARED(data) (data->share &&                        \
                                 (data->share->specifier &             \
                                  (1<<CURL_LOCK_DATA_SSL_SESSION)))

#define CLONE_STRING(var)                    \
  do {                                       \
    if(source->var) {                        \
      dest->var = strdup(source->var);       \
      if(!dest->var)                         \
        return FALSE;                        \
    }                                        \
    else                                     \
      dest->var = NULL;                      \
  } while(0)

#define CLONE_BLOB(var)                        \
  do {                                         \
    if(blobdup(&dest->var, source->var))       \
      return FALSE;                            \
  } while(0)

static CURLcode blobdup(struct curl_blob **dest,
                        struct curl_blob *src)
{
  DEBUGASSERT(dest);
  DEBUGASSERT(!*dest);
  if(src) {
    /* only if there's data to dupe! */
    struct curl_blob *d;
    d = malloc(sizeof(struct curl_blob) + src->len);
    if(!d)
      return CURLE_OUT_OF_MEMORY;
    d->len = src->len;
    /* Always duplicate because the connection may survive longer than the
       handle that passed in the blob. */
    d->flags = CURL_BLOB_COPY;
    d->data = (void *)((char *)d + sizeof(struct curl_blob));
    memcpy(d->data, src->data, src->len);
    *dest = d;
  }
  return CURLE_OK;
}

/* returns TRUE if the blobs are identical */
static bool blobcmp(struct curl_blob *first, struct curl_blob *second)
{
  if(!first && !second) /* both are NULL */
    return TRUE;
  if(!first || !second) /* one is NULL */
    return FALSE;
  if(first->len != second->len) /* different sizes */
    return FALSE;
  return !memcmp(first->data, second->data, first->len); /* same data */
}


bool
Curl_ssl_config_matches(struct ssl_primary_config *data,
                        struct ssl_primary_config *needle)
{
  if((data->version == needle->version) &&
     (data->version_max == needle->version_max) &&
     (data->ssl_options == needle->ssl_options) &&
     (data->verifypeer == needle->verifypeer) &&
     (data->verifyhost == needle->verifyhost) &&
     (data->verifystatus == needle->verifystatus) &&
     blobcmp(data->cert_blob, needle->cert_blob) &&
     blobcmp(data->ca_info_blob, needle->ca_info_blob) &&
     blobcmp(data->issuercert_blob, needle->issuercert_blob) &&
     Curl_safecmp(data->CApath, needle->CApath) &&
     Curl_safecmp(data->CAfile, needle->CAfile) &&
     Curl_safecmp(data->issuercert, needle->issuercert) &&
     Curl_safecmp(data->clientcert, needle->clientcert) &&
#ifdef USE_TLS_SRP
     !Curl_timestrcmp(data->username, needle->username) &&
     !Curl_timestrcmp(data->password, needle->password) &&
     (data->authtype == needle->authtype) &&
#endif
     Curl_safe_strcasecompare(data->cipher_list, needle->cipher_list) &&
     Curl_safe_strcasecompare(data->cipher_list13, needle->cipher_list13) &&
     Curl_safe_strcasecompare(data->curves, needle->curves) &&
     Curl_safe_strcasecompare(data->CRLfile, needle->CRLfile) &&
     Curl_safe_strcasecompare(data->pinned_key, needle->pinned_key))
    return TRUE;

  return FALSE;
}

bool
Curl_clone_primary_ssl_config(struct ssl_primary_config *source,
                              struct ssl_primary_config *dest)
{
  dest->version = source->version;
  dest->version_max = source->version_max;
  dest->verifypeer = source->verifypeer;
  dest->verifyhost = source->verifyhost;
  dest->verifystatus = source->verifystatus;
  dest->sessionid = source->sessionid;
  dest->ssl_options = source->ssl_options;
#ifdef USE_TLS_SRP
  dest->authtype = source->authtype;
#endif

  CLONE_BLOB(cert_blob);
  CLONE_BLOB(ca_info_blob);
  CLONE_BLOB(issuercert_blob);
  CLONE_STRING(CApath);
  CLONE_STRING(CAfile);
  CLONE_STRING(issuercert);
  CLONE_STRING(clientcert);
  CLONE_STRING(cipher_list);
  CLONE_STRING(cipher_list13);
  CLONE_STRING(pinned_key);
  CLONE_STRING(curves);
  CLONE_STRING(CRLfile);
#ifdef USE_TLS_SRP
  CLONE_STRING(username);
  CLONE_STRING(password);
#endif

  return TRUE;
}

void Curl_free_primary_ssl_config(struct ssl_primary_config *sslc)
{
  Curl_safefree(sslc->CApath);
  Curl_safefree(sslc->CAfile);
  Curl_safefree(sslc->issuercert);
  Curl_safefree(sslc->clientcert);
  Curl_safefree(sslc->cipher_list);
  Curl_safefree(sslc->cipher_list13);
  Curl_safefree(sslc->pinned_key);
  Curl_safefree(sslc->cert_blob);
  Curl_safefree(sslc->ca_info_blob);
  Curl_safefree(sslc->issuercert_blob);
  Curl_safefree(sslc->curves);
  Curl_safefree(sslc->CRLfile);
#ifdef USE_TLS_SRP
  Curl_safefree(sslc->username);
  Curl_safefree(sslc->password);
#endif
}

#ifdef USE_SSL
static int multissl_setup(const struct Curl_ssl *backend);
#endif

curl_sslbackend Curl_ssl_backend(void)
{
#ifdef USE_SSL
  multissl_setup(NULL);
  return Curl_ssl->info.id;
#else
  return CURLSSLBACKEND_NONE;
#endif
}

#ifdef USE_SSL

/* "global" init done? */
static bool init_ssl = FALSE;

/**
 * Global SSL init
 *
 * @retval 0 error initializing SSL
 * @retval 1 SSL initialized successfully
 */
int Curl_ssl_init(void)
{
  /* make sure this is only done once */
  if(init_ssl)
    return 1;
  init_ssl = TRUE; /* never again */

  return Curl_ssl->init();
}

#if defined(CURL_WITH_MULTI_SSL)
static const struct Curl_ssl Curl_ssl_multi;
#endif

/* Global cleanup */
void Curl_ssl_cleanup(void)
{
  if(init_ssl) {
    /* only cleanup if we did a previous init */
    Curl_ssl->cleanup();
#if defined(CURL_WITH_MULTI_SSL)
    Curl_ssl = &Curl_ssl_multi;
#endif
    init_ssl = FALSE;
  }
}

static bool ssl_prefs_check(struct Curl_easy *data)
{
  /* check for CURLOPT_SSLVERSION invalid parameter value */
  const long sslver = data->set.ssl.primary.version;
  if((sslver < 0) || (sslver >= CURL_SSLVERSION_LAST)) {
    failf(data, "Unrecognized parameter value passed via CURLOPT_SSLVERSION");
    return FALSE;
  }

  switch(data->set.ssl.primary.version_max) {
  case CURL_SSLVERSION_MAX_NONE:
  case CURL_SSLVERSION_MAX_DEFAULT:
    break;

  default:
    if((data->set.ssl.primary.version_max >> 16) < sslver) {
      failf(data, "CURL_SSLVERSION_MAX incompatible with CURL_SSLVERSION");
      return FALSE;
    }
  }

  return TRUE;
}

#ifndef CURL_DISABLE_PROXY
static CURLcode
ssl_connect_init_proxy(struct connectdata *conn, int sockindex)
{
  DEBUGASSERT(conn->bits.proxy_ssl_connected[sockindex]);
  if(ssl_connection_complete == conn->ssl[sockindex].state &&
     !conn->proxy_ssl[sockindex].use) {
    struct ssl_backend_data *pbdata;

    if(!(Curl_ssl->supports & SSLSUPP_HTTPS_PROXY))
      return CURLE_NOT_BUILT_IN;

    /* The pointers to the ssl backend data, which is opaque here, are swapped
       rather than move the contents. */
    pbdata = conn->proxy_ssl[sockindex].backend;
    conn->proxy_ssl[sockindex] = conn->ssl[sockindex];

    DEBUGASSERT(pbdata != NULL);

    memset(&conn->ssl[sockindex], 0, sizeof(conn->ssl[sockindex]));
    memset(pbdata, 0, Curl_ssl->sizeof_ssl_backend_data);

    conn->ssl[sockindex].backend = pbdata;
  }
  return CURLE_OK;
}
#endif

CURLcode
Curl_ssl_connect(struct Curl_easy *data, struct connectdata *conn,
                 int sockindex)
{
  CURLcode result;

#ifndef CURL_DISABLE_PROXY
  if(conn->bits.proxy_ssl_connected[sockindex]) {
    result = ssl_connect_init_proxy(conn, sockindex);
    if(result)
      return result;
  }
#endif

  if(!ssl_prefs_check(data))
    return CURLE_SSL_CONNECT_ERROR;

  /* mark this is being ssl-enabled from here on. */
  conn->ssl[sockindex].use = TRUE;
  conn->ssl[sockindex].state = ssl_connection_negotiating;

  result = Curl_ssl->connect_blocking(data, conn, sockindex);

  if(!result)
    Curl_pgrsTime(data, TIMER_APPCONNECT); /* SSL is connected */
  else
    conn->ssl[sockindex].use = FALSE;

  return result;
}

CURLcode
Curl_ssl_connect_nonblocking(struct Curl_easy *data, struct connectdata *conn,
                             bool isproxy, int sockindex, bool *done)
{
  CURLcode result;

#ifndef CURL_DISABLE_PROXY
  if(conn->bits.proxy_ssl_connected[sockindex]) {
    result = ssl_connect_init_proxy(conn, sockindex);
    if(result)
      return result;
  }
#endif
  if(!ssl_prefs_check(data))
    return CURLE_SSL_CONNECT_ERROR;

  /* mark this is being ssl requested from here on. */
  conn->ssl[sockindex].use = TRUE;
  result = Curl_ssl->connect_nonblocking(data, conn, sockindex, done);
  if(result)
    conn->ssl[sockindex].use = FALSE;
  else if(*done && !isproxy)
    Curl_pgrsTime(data, TIMER_APPCONNECT); /* SSL is connected */
  return result;
}

/*
 * Lock shared SSL session data
 */
void Curl_ssl_sessionid_lock(struct Curl_easy *data)
{
  if(SSLSESSION_SHARED(data))
    Curl_share_lock(data, CURL_LOCK_DATA_SSL_SESSION, CURL_LOCK_ACCESS_SINGLE);
}

/*
 * Unlock shared SSL session data
 */
void Curl_ssl_sessionid_unlock(struct Curl_easy *data)
{
  if(SSLSESSION_SHARED(data))
    Curl_share_unlock(data, CURL_LOCK_DATA_SSL_SESSION);
}

/*
 * Check if there's a session ID for the given connection in the cache, and if
 * there's one suitable, it is provided. Returns TRUE when no entry matched.
 */
bool Curl_ssl_getsessionid(struct Curl_easy *data,
                           struct connectdata *conn,
                           const bool isProxy,
                           void **ssl_sessionid,
                           size_t *idsize, /* set 0 if unknown */
                           int sockindex)
{
  struct Curl_ssl_session *check;
  size_t i;
  long *general_age;
  bool no_match = TRUE;

#ifndef CURL_DISABLE_PROXY
  struct ssl_primary_config * const ssl_config = isProxy ?
    &conn->proxy_ssl_config :
    &conn->ssl_config;
  const char * const name = isProxy ?
    conn->http_proxy.host.name : conn->host.name;
  int port = isProxy ? (int)conn->port : conn->remote_port;
#else
  /* no proxy support */
  struct ssl_primary_config * const ssl_config = &conn->ssl_config;
  const char * const name = conn->host.name;
  int port = conn->remote_port;
#endif
  (void)sockindex;
  *ssl_sessionid = NULL;

#ifdef CURL_DISABLE_PROXY
  if(isProxy)
    return TRUE;
#endif

  DEBUGASSERT(SSL_SET_OPTION(primary.sessionid));

  if(!SSL_SET_OPTION(primary.sessionid) || !data->state.session)
    /* session ID re-use is disabled or the session cache has not been
       setup */
    return TRUE;

  /* Lock if shared */
  if(SSLSESSION_SHARED(data))
    general_age = &data->share->sessionage;
  else
    general_age = &data->state.sessionage;

  for(i = 0; i < data->set.general_ssl.max_ssl_sessions; i++) {
    check = &data->state.session[i];
    if(!check->sessionid)
      /* not session ID means blank entry */
      continue;
    if(strcasecompare(name, check->name) &&
       ((!conn->bits.conn_to_host && !check->conn_to_host) ||
        (conn->bits.conn_to_host && check->conn_to_host &&
         strcasecompare(conn->conn_to_host.name, check->conn_to_host))) &&
       ((!conn->bits.conn_to_port && check->conn_to_port == -1) ||
        (conn->bits.conn_to_port && check->conn_to_port != -1 &&
         conn->conn_to_port == check->conn_to_port)) &&
       (port == check->remote_port) &&
       strcasecompare(conn->handler->scheme, check->scheme) &&
       Curl_ssl_config_matches(ssl_config, &check->ssl_config)) {
      /* yes, we have a session ID! */
      (*general_age)++;          /* increase general age */
      check->age = *general_age; /* set this as used in this age */
      *ssl_sessionid = check->sessionid;
      if(idsize)
        *idsize = check->idsize;
      no_match = FALSE;
      break;
    }
  }

  DEBUGF(infof(data, "%s Session ID in cache for %s %s://%s:%d",
               no_match? "Didn't find": "Found",
               isProxy ? "proxy" : "host",
               conn->handler->scheme, name, port));
  return no_match;
}

/*
 * Kill a single session ID entry in the cache.
 */
void Curl_ssl_kill_session(struct Curl_ssl_session *session)
{
  if(session->sessionid) {
    /* defensive check */

    /* free the ID the SSL-layer specific way */
    Curl_ssl->session_free(session->sessionid);

    session->sessionid = NULL;
    session->age = 0; /* fresh */

    Curl_free_primary_ssl_config(&session->ssl_config);

    Curl_safefree(session->name);
    Curl_safefree(session->conn_to_host);
  }
}

/*
 * Delete the given session ID from the cache.
 */
void Curl_ssl_delsessionid(struct Curl_easy *data, void *ssl_sessionid)
{
  size_t i;

  for(i = 0; i < data->set.general_ssl.max_ssl_sessions; i++) {
    struct Curl_ssl_session *check = &data->state.session[i];

    if(check->sessionid == ssl_sessionid) {
      Curl_ssl_kill_session(check);
      break;
    }
  }
}

/*
 * Store session id in the session cache. The ID passed on to this function
 * must already have been extracted and allocated the proper way for the SSL
 * layer. Curl_XXXX_session_free() will be called to free/kill the session ID
 * later on.
 */
CURLcode Curl_ssl_addsessionid(struct Curl_easy *data,
                               struct connectdata *conn,
                               const bool isProxy,
                               void *ssl_sessionid,
                               size_t idsize,
                               int sockindex,
                               bool *added)
{
  size_t i;
  struct Curl_ssl_session *store;
  long oldest_age;
  char *clone_host;
  char *clone_conn_to_host;
  int conn_to_port;
  long *general_age;
#ifndef CURL_DISABLE_PROXY
  struct ssl_primary_config * const ssl_config = isProxy ?
    &conn->proxy_ssl_config :
    &conn->ssl_config;
  const char *hostname = isProxy ? conn->http_proxy.host.name :
    conn->host.name;
#else
  struct ssl_primary_config * const ssl_config = &conn->ssl_config;
  const char *hostname = conn->host.name;
#endif
  (void)sockindex;

  if(added)
    *added = FALSE;

  if(!data->state.session)
    return CURLE_OK;

  store = &data->state.session[0];
  oldest_age = data->state.session[0].age; /* zero if unused */
  DEBUGASSERT(SSL_SET_OPTION(primary.sessionid));

  clone_host = strdup(hostname);
  if(!clone_host)
    return CURLE_OUT_OF_MEMORY; /* bail out */

  if(conn->bits.conn_to_host) {
    clone_conn_to_host = strdup(conn->conn_to_host.name);
    if(!clone_conn_to_host) {
      free(clone_host);
      return CURLE_OUT_OF_MEMORY; /* bail out */
    }
  }
  else
    clone_conn_to_host = NULL;

  if(conn->bits.conn_to_port)
    conn_to_port = conn->conn_to_port;
  else
    conn_to_port = -1;

  /* Now we should add the session ID and the host name to the cache, (remove
     the oldest if necessary) */

  /* If using shared SSL session, lock! */
  if(SSLSESSION_SHARED(data)) {
    general_age = &data->share->sessionage;
  }
  else {
    general_age = &data->state.sessionage;
  }

  /* find an empty slot for us, or find the oldest */
  for(i = 1; (i < data->set.general_ssl.max_ssl_sessions) &&
        data->state.session[i].sessionid; i++) {
    if(data->state.session[i].age < oldest_age) {
      oldest_age = data->state.session[i].age;
      store = &data->state.session[i];
    }
  }
  if(i == data->set.general_ssl.max_ssl_sessions)
    /* cache is full, we must "kill" the oldest entry! */
    Curl_ssl_kill_session(store);
  else
    store = &data->state.session[i]; /* use this slot */

  /* now init the session struct wisely */
  store->sessionid = ssl_sessionid;
  store->idsize = idsize;
  store->age = *general_age;    /* set current age */
  /* free it if there's one already present */
  free(store->name);
  free(store->conn_to_host);
  store->name = clone_host;               /* clone host name */
  store->conn_to_host = clone_conn_to_host; /* clone connect to host name */
  store->conn_to_port = conn_to_port; /* connect to port number */
  /* port number */
  store->remote_port = isProxy ? (int)conn->port : conn->remote_port;
  store->scheme = conn->handler->scheme;

  if(!Curl_clone_primary_ssl_config(ssl_config, &store->ssl_config)) {
    Curl_free_primary_ssl_config(&store->ssl_config);
    store->sessionid = NULL; /* let caller free sessionid */
    free(clone_host);
    free(clone_conn_to_host);
    return CURLE_OUT_OF_MEMORY;
  }

  if(added)
    *added = TRUE;

  DEBUGF(infof(data, "Added Session ID to cache for %s://%s:%d [%s]",
               store->scheme, store->name, store->remote_port,
               isProxy ? "PROXY" : "server"));
  return CURLE_OK;
}

void Curl_ssl_associate_conn(struct Curl_easy *data,
                             struct connectdata *conn)
{
  if(Curl_ssl->associate_connection) {
    Curl_ssl->associate_connection(data, conn, FIRSTSOCKET);
    if((conn->sock[SECONDARYSOCKET] != CURL_SOCKET_BAD) &&
       conn->bits.sock_accepted)
      Curl_ssl->associate_connection(data, conn, SECONDARYSOCKET);
  }
}

void Curl_ssl_detach_conn(struct Curl_easy *data,
                          struct connectdata *conn)
{
  if(Curl_ssl->disassociate_connection) {
    Curl_ssl->disassociate_connection(data, FIRSTSOCKET);
    if((conn->sock[SECONDARYSOCKET] != CURL_SOCKET_BAD) &&
       conn->bits.sock_accepted)
      Curl_ssl->disassociate_connection(data, SECONDARYSOCKET);
  }
}

void Curl_ssl_close_all(struct Curl_easy *data)
{
  /* kill the session ID cache if not shared */
  if(data->state.session && !SSLSESSION_SHARED(data)) {
    size_t i;
    for(i = 0; i < data->set.general_ssl.max_ssl_sessions; i++)
      /* the single-killer function handles empty table slots */
      Curl_ssl_kill_session(&data->state.session[i]);

    /* free the cache data */
    Curl_safefree(data->state.session);
  }

  Curl_ssl->close_all(data);
}

int Curl_ssl_getsock(struct connectdata *conn, curl_socket_t *socks)
{
  struct ssl_connect_data *connssl = &conn->ssl[FIRSTSOCKET];

  if(connssl->connecting_state == ssl_connect_2_writing) {
    /* write mode */
    socks[0] = conn->sock[FIRSTSOCKET];
    return GETSOCK_WRITESOCK(0);
  }
  if(connssl->connecting_state == ssl_connect_2_reading) {
    /* read mode */
    socks[0] = conn->sock[FIRSTSOCKET];
    return GETSOCK_READSOCK(0);
  }

  return GETSOCK_BLANK;
}

void Curl_ssl_close(struct Curl_easy *data, struct connectdata *conn,
                    int sockindex)
{
  DEBUGASSERT((sockindex <= 1) && (sockindex >= -1));
  Curl_ssl->close_one(data, conn, sockindex);
  conn->ssl[sockindex].state = ssl_connection_none;
}

CURLcode Curl_ssl_shutdown(struct Curl_easy *data, struct connectdata *conn,
                           int sockindex)
{
  if(Curl_ssl->shut_down(data, conn, sockindex))
    return CURLE_SSL_SHUTDOWN_FAILED;

  conn->ssl[sockindex].use = FALSE; /* get back to ordinary socket usage */
  conn->ssl[sockindex].state = ssl_connection_none;

  conn->recv[sockindex] = Curl_recv_plain;
  conn->send[sockindex] = Curl_send_plain;

  return CURLE_OK;
}

/* Selects an SSL crypto engine
 */
CURLcode Curl_ssl_set_engine(struct Curl_easy *data, const char *engine)
{
  return Curl_ssl->set_engine(data, engine);
}

/* Selects the default SSL crypto engine
 */
CURLcode Curl_ssl_set_engine_default(struct Curl_easy *data)
{
  return Curl_ssl->set_engine_default(data);
}

/* Return list of OpenSSL crypto engine names. */
struct curl_slist *Curl_ssl_engines_list(struct Curl_easy *data)
{
  return Curl_ssl->engines_list(data);
}

/*
 * This sets up a session ID cache to the specified size. Make sure this code
 * is agnostic to what underlying SSL technology we use.
 */
CURLcode Curl_ssl_initsessions(struct Curl_easy *data, size_t amount)
{
  struct Curl_ssl_session *session;

  if(data->state.session)
    /* this is just a precaution to prevent multiple inits */
    return CURLE_OK;

  session = calloc(amount, sizeof(struct Curl_ssl_session));
  if(!session)
    return CURLE_OUT_OF_MEMORY;

  /* store the info in the SSL section */
  data->set.general_ssl.max_ssl_sessions = amount;
  data->state.session = session;
  data->state.sessionage = 1; /* this is brand new */
  return CURLE_OK;
}

static size_t multissl_version(char *buffer, size_t size);

void Curl_ssl_version(char *buffer, size_t size)
{
#ifdef CURL_WITH_MULTI_SSL
  (void)multissl_version(buffer, size);
#else
  (void)Curl_ssl->version(buffer, size);
#endif
}

/*
 * This function tries to determine connection status.
 *
 * Return codes:
 *     1 means the connection is still in place
 *     0 means the connection has been closed
 *    -1 means the connection status is unknown
 */
int Curl_ssl_check_cxn(struct connectdata *conn)
{
  return Curl_ssl->check_cxn(conn);
}

bool Curl_ssl_data_pending(const struct connectdata *conn,
                           int connindex)
{
  return Curl_ssl->data_pending(conn, connindex);
}

void Curl_ssl_free_certinfo(struct Curl_easy *data)
{
  struct curl_certinfo *ci = &data->info.certs;

  if(ci->num_of_certs) {
    /* free all individual lists used */
    int i;
    for(i = 0; i<ci->num_of_certs; i++) {
      curl_slist_free_all(ci->certinfo[i]);
      ci->certinfo[i] = NULL;
    }

    free(ci->certinfo); /* free the actual array too */
    ci->certinfo = NULL;
    ci->num_of_certs = 0;
  }
}

CURLcode Curl_ssl_init_certinfo(struct Curl_easy *data, int num)
{
  struct curl_certinfo *ci = &data->info.certs;
  struct curl_slist **table;

  /* Free any previous certificate information structures */
  Curl_ssl_free_certinfo(data);

  /* Allocate the required certificate information structures */
  table = calloc((size_t) num, sizeof(struct curl_slist *));
  if(!table)
    return CURLE_OUT_OF_MEMORY;

  ci->num_of_certs = num;
  ci->certinfo = table;

  return CURLE_OK;
}

/*
 * 'value' is NOT a null-terminated string
 */
CURLcode Curl_ssl_push_certinfo_len(struct Curl_easy *data,
                                    int certnum,
                                    const char *label,
                                    const char *value,
                                    size_t valuelen)
{
  struct curl_certinfo *ci = &data->info.certs;
  char *output;
  struct curl_slist *nl;
  CURLcode result = CURLE_OK;
  size_t labellen = strlen(label);
  size_t outlen = labellen + 1 + valuelen + 1; /* label:value\0 */

  output = malloc(outlen);
  if(!output)
    return CURLE_OUT_OF_MEMORY;

  /* sprintf the label and colon */
  msnprintf(output, outlen, "%s:", label);

  /* memcpy the value (it might not be null-terminated) */
  memcpy(&output[labellen + 1], value, valuelen);

  /* null-terminate the output */
  output[labellen + 1 + valuelen] = 0;

  nl = Curl_slist_append_nodup(ci->certinfo[certnum], output);
  if(!nl) {
    free(output);
    curl_slist_free_all(ci->certinfo[certnum]);
    result = CURLE_OUT_OF_MEMORY;
  }

  ci->certinfo[certnum] = nl;
  return result;
}

/*
 * This is a convenience function for push_certinfo_len that takes a zero
 * terminated value.
 */
CURLcode Curl_ssl_push_certinfo(struct Curl_easy *data,
                                int certnum,
                                const char *label,
                                const char *value)
{
  size_t valuelen = strlen(value);

  return Curl_ssl_push_certinfo_len(data, certnum, label, value, valuelen);
}

CURLcode Curl_ssl_random(struct Curl_easy *data,
                         unsigned char *entropy,
                         size_t length)
{
  return Curl_ssl->random(data, entropy, length);
}

/*
 * Curl_ssl_snihost() converts the input host name to a suitable SNI name put
 * in data->state.buffer. Returns a pointer to the name (or NULL if a problem)
 * and stores the new length in 'olen'.
 *
 * SNI fields must not have any trailing dot and while RFC 6066 section 3 says
 * the SNI field is case insensitive, browsers always send the data lowercase
 * and subsequently there are numerous servers out there that don't work
 * unless the name is lowercased.
 */

char *Curl_ssl_snihost(struct Curl_easy *data, const char *host, size_t *olen)
{
  size_t len = strlen(host);
  if(len && (host[len-1] == '.'))
    len--;
  if(len >= data->set.buffer_size)
    return NULL;

  Curl_strntolower(data->state.buffer, host, len);
  data->state.buffer[len] = 0;
  if(olen)
    *olen = len;
  return data->state.buffer;
}

/*
 * Public key pem to der conversion
 */

static CURLcode pubkey_pem_to_der(const char *pem,
                                  unsigned char **der, size_t *der_len)
{
  char *stripped_pem, *begin_pos, *end_pos;
  size_t pem_count, stripped_pem_count = 0, pem_len;
  CURLcode result;

  /* if no pem, exit. */
  if(!pem)
    return CURLE_BAD_CONTENT_ENCODING;

  begin_pos = strstr(pem, "-----BEGIN PUBLIC KEY-----");
  if(!begin_pos)
    return CURLE_BAD_CONTENT_ENCODING;

  pem_count = begin_pos - pem;
  /* Invalid if not at beginning AND not directly following \n */
  if(0 != pem_count && '\n' != pem[pem_count - 1])
    return CURLE_BAD_CONTENT_ENCODING;

  /* 26 is length of "-----BEGIN PUBLIC KEY-----" */
  pem_count += 26;

  /* Invalid if not directly following \n */
  end_pos = strstr(pem + pem_count, "\n-----END PUBLIC KEY-----");
  if(!end_pos)
    return CURLE_BAD_CONTENT_ENCODING;

  pem_len = end_pos - pem;

  stripped_pem = malloc(pem_len - pem_count + 1);
  if(!stripped_pem)
    return CURLE_OUT_OF_MEMORY;

  /*
   * Here we loop through the pem array one character at a time between the
   * correct indices, and place each character that is not '\n' or '\r'
   * into the stripped_pem array, which should represent the raw base64 string
   */
  while(pem_count < pem_len) {
    if('\n' != pem[pem_count] && '\r' != pem[pem_count])
      stripped_pem[stripped_pem_count++] = pem[pem_count];
    ++pem_count;
  }
  /* Place the null terminator in the correct place */
  stripped_pem[stripped_pem_count] = '\0';

  result = Curl_base64_decode(stripped_pem, der, der_len);

  Curl_safefree(stripped_pem);

  return result;
}

/*
 * Generic pinned public key check.
 */

CURLcode Curl_pin_peer_pubkey(struct Curl_easy *data,
                              const char *pinnedpubkey,
                              const unsigned char *pubkey, size_t pubkeylen)
{
  FILE *fp;
  unsigned char *buf = NULL, *pem_ptr = NULL;
  CURLcode result = CURLE_SSL_PINNEDPUBKEYNOTMATCH;

  /* if a path wasn't specified, don't pin */
  if(!pinnedpubkey)
    return CURLE_OK;
  if(!pubkey || !pubkeylen)
    return result;

  /* only do this if pinnedpubkey starts with "sha256//", length 8 */
  if(strncmp(pinnedpubkey, "sha256//", 8) == 0) {
    CURLcode encode;
    size_t encodedlen, pinkeylen;
    char *encoded, *pinkeycopy, *begin_pos, *end_pos;
    unsigned char *sha256sumdigest;

    if(!Curl_ssl->sha256sum) {
      /* without sha256 support, this cannot match */
      return result;
    }

    /* compute sha256sum of public key */
    sha256sumdigest = malloc(CURL_SHA256_DIGEST_LENGTH);
    if(!sha256sumdigest)
      return CURLE_OUT_OF_MEMORY;
    encode = Curl_ssl->sha256sum(pubkey, pubkeylen,
                        sha256sumdigest, CURL_SHA256_DIGEST_LENGTH);

    if(encode != CURLE_OK)
      return encode;

    encode = Curl_base64_encode((char *)sha256sumdigest,
                                CURL_SHA256_DIGEST_LENGTH, &encoded,
                                &encodedlen);
    Curl_safefree(sha256sumdigest);

    if(encode)
      return encode;

    infof(data, " public key hash: sha256//%s", encoded);

    /* it starts with sha256//, copy so we can modify it */
    pinkeylen = strlen(pinnedpubkey) + 1;
    pinkeycopy = malloc(pinkeylen);
    if(!pinkeycopy) {
      Curl_safefree(encoded);
      return CURLE_OUT_OF_MEMORY;
    }
    memcpy(pinkeycopy, pinnedpubkey, pinkeylen);
    /* point begin_pos to the copy, and start extracting keys */
    begin_pos = pinkeycopy;
    do {
      end_pos = strstr(begin_pos, ";sha256//");
      /*
       * if there is an end_pos, null terminate,
       * otherwise it'll go to the end of the original string
       */
      if(end_pos)
        end_pos[0] = '\0';

      /* compare base64 sha256 digests, 8 is the length of "sha256//" */
      if(encodedlen == strlen(begin_pos + 8) &&
         !memcmp(encoded, begin_pos + 8, encodedlen)) {
        result = CURLE_OK;
        break;
      }

      /*
       * change back the null-terminator we changed earlier,
       * and look for next begin
       */
      if(end_pos) {
        end_pos[0] = ';';
        begin_pos = strstr(end_pos, "sha256//");
      }
    } while(end_pos && begin_pos);
    Curl_safefree(encoded);
    Curl_safefree(pinkeycopy);
    return result;
  }

  fp = fopen(pinnedpubkey, "rb");
  if(!fp)
    return result;

  do {
    long filesize;
    size_t size, pem_len;
    CURLcode pem_read;

    /* Determine the file's size */
    if(fseek(fp, 0, SEEK_END))
      break;
    filesize = ftell(fp);
    if(fseek(fp, 0, SEEK_SET))
      break;
    if(filesize < 0 || filesize > MAX_PINNED_PUBKEY_SIZE)
      break;

    /*
     * if the size of our certificate is bigger than the file
     * size then it can't match
     */
    size = curlx_sotouz((curl_off_t) filesize);
    if(pubkeylen > size)
      break;

    /*
     * Allocate buffer for the pinned key
     * With 1 additional byte for null terminator in case of PEM key
     */
    buf = malloc(size + 1);
    if(!buf)
      break;

    /* Returns number of elements read, which should be 1 */
    if((int) fread(buf, size, 1, fp) != 1)
      break;

    /* If the sizes are the same, it can't be base64 encoded, must be der */
    if(pubkeylen == size) {
      if(!memcmp(pubkey, buf, pubkeylen))
        result = CURLE_OK;
      break;
    }

    /*
     * Otherwise we will assume it's PEM and try to decode it
     * after placing null terminator
     */
    buf[size] = '\0';
    pem_read = pubkey_pem_to_der((const char *)buf, &pem_ptr, &pem_len);
    /* if it wasn't read successfully, exit */
    if(pem_read)
      break;

    /*
     * if the size of our certificate doesn't match the size of
     * the decoded file, they can't be the same, otherwise compare
     */
    if(pubkeylen == pem_len && !memcmp(pubkey, pem_ptr, pubkeylen))
      result = CURLE_OK;
  } while(0);

  Curl_safefree(buf);
  Curl_safefree(pem_ptr);
  fclose(fp);

  return result;
}

/*
 * Check whether the SSL backend supports the status_request extension.
 */
bool Curl_ssl_cert_status_request(void)
{
  return Curl_ssl->cert_status_request();
}

/*
 * Check whether the SSL backend supports false start.
 */
bool Curl_ssl_false_start(void)
{
  return Curl_ssl->false_start();
}

/*
 * Check whether the SSL backend supports setting TLS 1.3 cipher suites
 */
bool Curl_ssl_tls13_ciphersuites(void)
{
  return Curl_ssl->supports & SSLSUPP_TLS13_CIPHERSUITES;
}

/*
 * Default implementations for unsupported functions.
 */

int Curl_none_init(void)
{
  return 1;
}

void Curl_none_cleanup(void)
{ }

int Curl_none_shutdown(struct Curl_easy *data UNUSED_PARAM,
                       struct connectdata *conn UNUSED_PARAM,
                       int sockindex UNUSED_PARAM)
{
  (void)data;
  (void)conn;
  (void)sockindex;
  return 0;
}

int Curl_none_check_cxn(struct connectdata *conn UNUSED_PARAM)
{
  (void)conn;
  return -1;
}

CURLcode Curl_none_random(struct Curl_easy *data UNUSED_PARAM,
                          unsigned char *entropy UNUSED_PARAM,
                          size_t length UNUSED_PARAM)
{
  (void)data;
  (void)entropy;
  (void)length;
  return CURLE_NOT_BUILT_IN;
}

void Curl_none_close_all(struct Curl_easy *data UNUSED_PARAM)
{
  (void)data;
}

void Curl_none_session_free(void *ptr UNUSED_PARAM)
{
  (void)ptr;
}

bool Curl_none_data_pending(const struct connectdata *conn UNUSED_PARAM,
                            int connindex UNUSED_PARAM)
{
  (void)conn;
  (void)connindex;
  return 0;
}

bool Curl_none_cert_status_request(void)
{
  return FALSE;
}

CURLcode Curl_none_set_engine(struct Curl_easy *data UNUSED_PARAM,
                              const char *engine UNUSED_PARAM)
{
  (void)data;
  (void)engine;
  return CURLE_NOT_BUILT_IN;
}

CURLcode Curl_none_set_engine_default(struct Curl_easy *data UNUSED_PARAM)
{
  (void)data;
  return CURLE_NOT_BUILT_IN;
}

struct curl_slist *Curl_none_engines_list(struct Curl_easy *data UNUSED_PARAM)
{
  (void)data;
  return (struct curl_slist *)NULL;
}

bool Curl_none_false_start(void)
{
  return FALSE;
}

static int multissl_init(void)
{
  if(multissl_setup(NULL))
    return 1;
  return Curl_ssl->init();
}

static CURLcode multissl_connect(struct Curl_easy *data,
                                 struct connectdata *conn, int sockindex)
{
  if(multissl_setup(NULL))
    return CURLE_FAILED_INIT;
  return Curl_ssl->connect_blocking(data, conn, sockindex);
}

static CURLcode multissl_connect_nonblocking(struct Curl_easy *data,
                                             struct connectdata *conn,
                                             int sockindex, bool *done)
{
  if(multissl_setup(NULL))
    return CURLE_FAILED_INIT;
  return Curl_ssl->connect_nonblocking(data, conn, sockindex, done);
}

static int multissl_getsock(struct connectdata *conn, curl_socket_t *socks)
{
  if(multissl_setup(NULL))
    return 0;
  return Curl_ssl->getsock(conn, socks);
}

static void *multissl_get_internals(struct ssl_connect_data *connssl,
                                    CURLINFO info)
{
  if(multissl_setup(NULL))
    return NULL;
  return Curl_ssl->get_internals(connssl, info);
}

static void multissl_close(struct Curl_easy *data, struct connectdata *conn,
                           int sockindex)
{
  if(multissl_setup(NULL))
    return;
  Curl_ssl->close_one(data, conn, sockindex);
}

static const struct Curl_ssl Curl_ssl_multi = {
  { CURLSSLBACKEND_NONE, "multi" },  /* info */
  0, /* supports nothing */
  (size_t)-1, /* something insanely large to be on the safe side */

  multissl_init,                     /* init */
  Curl_none_cleanup,                 /* cleanup */
  multissl_version,                  /* version */
  Curl_none_check_cxn,               /* check_cxn */
  Curl_none_shutdown,                /* shutdown */
  Curl_none_data_pending,            /* data_pending */
  Curl_none_random,                  /* random */
  Curl_none_cert_status_request,     /* cert_status_request */
  multissl_connect,                  /* connect */
  multissl_connect_nonblocking,      /* connect_nonblocking */
  multissl_getsock,                  /* getsock */
  multissl_get_internals,            /* get_internals */
  multissl_close,                    /* close_one */
  Curl_none_close_all,               /* close_all */
  Curl_none_session_free,            /* session_free */
  Curl_none_set_engine,              /* set_engine */
  Curl_none_set_engine_default,      /* set_engine_default */
  Curl_none_engines_list,            /* engines_list */
  Curl_none_false_start,             /* false_start */
  NULL,                              /* sha256sum */
  NULL,                              /* associate_connection */
  NULL                               /* disassociate_connection */
};

const struct Curl_ssl *Curl_ssl =
#if defined(CURL_WITH_MULTI_SSL)
  &Curl_ssl_multi;
#elif defined(USE_WOLFSSL)
  &Curl_ssl_wolfssl;
#elif defined(USE_SECTRANSP)
  &Curl_ssl_sectransp;
#elif defined(USE_GNUTLS)
  &Curl_ssl_gnutls;
#elif defined(USE_GSKIT)
  &Curl_ssl_gskit;
#elif defined(USE_MBEDTLS)
  &Curl_ssl_mbedtls;
#elif defined(USE_NSS)
  &Curl_ssl_nss;
#elif defined(USE_RUSTLS)
  &Curl_ssl_rustls;
#elif defined(USE_OPENSSL)
  &Curl_ssl_openssl;
#elif defined(USE_SCHANNEL)
  &Curl_ssl_schannel;
#elif defined(USE_BEARSSL)
  &Curl_ssl_bearssl;
#else
#error "Missing struct Curl_ssl for selected SSL backend"
#endif

static const struct Curl_ssl *available_backends[] = {
#if defined(USE_WOLFSSL)
  &Curl_ssl_wolfssl,
#endif
#if defined(USE_SECTRANSP)
  &Curl_ssl_sectransp,
#endif
#if defined(USE_GNUTLS)
  &Curl_ssl_gnutls,
#endif
#if defined(USE_GSKIT)
  &Curl_ssl_gskit,
#endif
#if defined(USE_MBEDTLS)
  &Curl_ssl_mbedtls,
#endif
#if defined(USE_NSS)
  &Curl_ssl_nss,
#endif
#if defined(USE_OPENSSL)
  &Curl_ssl_openssl,
#endif
#if defined(USE_SCHANNEL)
  &Curl_ssl_schannel,
#endif
#if defined(USE_BEARSSL)
  &Curl_ssl_bearssl,
#endif
#if defined(USE_RUSTLS)
  &Curl_ssl_rustls,
#endif
  NULL
};

static size_t multissl_version(char *buffer, size_t size)
{
  static const struct Curl_ssl *selected;
  static char backends[200];
  static size_t backends_len;
  const struct Curl_ssl *current;

  current = Curl_ssl == &Curl_ssl_multi ? available_backends[0] : Curl_ssl;

  if(current != selected) {
    char *p = backends;
    char *end = backends + sizeof(backends);
    int i;

    selected = current;

    backends[0] = '\0';

    for(i = 0; available_backends[i]; ++i) {
      char vb[200];
      bool paren = (selected != available_backends[i]);

      if(available_backends[i]->version(vb, sizeof(vb))) {
        p += msnprintf(p, end - p, "%s%s%s%s", (p != backends ? " " : ""),
                       (paren ? "(" : ""), vb, (paren ? ")" : ""));
      }
    }

    backends_len = p - backends;
  }

  if(!size)
    return 0;

  if(size <= backends_len) {
    strncpy(buffer, backends, size - 1);
    buffer[size - 1] = '\0';
    return size - 1;
  }

  strcpy(buffer, backends);
  return backends_len;
}

static int multissl_setup(const struct Curl_ssl *backend)
{
  const char *env;
  char *env_tmp;

  if(Curl_ssl != &Curl_ssl_multi)
    return 1;

  if(backend) {
    Curl_ssl = backend;
    return 0;
  }

  if(!available_backends[0])
    return 1;

  env = env_tmp = curl_getenv("CURL_SSL_BACKEND");
#ifdef CURL_DEFAULT_SSL_BACKEND
  if(!env)
    env = CURL_DEFAULT_SSL_BACKEND;
#endif
  if(env) {
    int i;
    for(i = 0; available_backends[i]; i++) {
      if(strcasecompare(env, available_backends[i]->info.name)) {
        Curl_ssl = available_backends[i];
        free(env_tmp);
        return 0;
      }
    }
  }

  /* Fall back to first available backend */
  Curl_ssl = available_backends[0];
  free(env_tmp);
  return 0;
}

/* This function is used to select the SSL backend to use. It is called by
   curl_global_sslset (easy.c) which uses the global init lock. */
CURLsslset Curl_init_sslset_nolock(curl_sslbackend id, const char *name,
                                   const curl_ssl_backend ***avail)
{
  int i;

  if(avail)
    *avail = (const curl_ssl_backend **)&available_backends;

  if(Curl_ssl != &Curl_ssl_multi)
    return id == Curl_ssl->info.id ||
           (name && strcasecompare(name, Curl_ssl->info.name)) ?
           CURLSSLSET_OK :
#if defined(CURL_WITH_MULTI_SSL)
           CURLSSLSET_TOO_LATE;
#else
           CURLSSLSET_UNKNOWN_BACKEND;
#endif

  for(i = 0; available_backends[i]; i++) {
    if(available_backends[i]->info.id == id ||
       (name && strcasecompare(available_backends[i]->info.name, name))) {
      multissl_setup(available_backends[i]);
      return CURLSSLSET_OK;
    }
  }

  return CURLSSLSET_UNKNOWN_BACKEND;
}

#else /* USE_SSL */
CURLsslset Curl_init_sslset_nolock(curl_sslbackend id, const char *name,
                                   const curl_ssl_backend ***avail)
{
  (void)id;
  (void)name;
  (void)avail;
  return CURLSSLSET_NO_BACKENDS;
}

#endif /* !USE_SSL */