aboutsummaryrefslogtreecommitdiff
path: root/lib/vtls/gtls.c
blob: 0f9bf7b3526a4ce373810b66693f1ceadba0abb5 (plain)
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
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2014, 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 http://curl.haxx.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.
 *
 ***************************************************************************/

/*
 * Source file for all GnuTLS-specific code for the TLS/SSL layer. No code
 * but vtls.c should ever call or use these functions.
 *
 * Note: don't use the GnuTLS' *_t variable type names in this source code,
 * since they were not present in 1.0.X.
 */

#include "curl_setup.h"

#ifdef USE_GNUTLS

#include <gnutls/gnutls.h>
#include <gnutls/x509.h>

#ifdef USE_GNUTLS_NETTLE
#include <gnutls/crypto.h>
#include <nettle/md5.h>
#else
#include <gcrypt.h>
#endif

#include "urldata.h"
#include "sendf.h"
#include "inet_pton.h"
#include "gtls.h"
#include "vtls.h"
#include "parsedate.h"
#include "connect.h" /* for the connect timeout */
#include "select.h"
#include "rawstr.h"
#include "warnless.h"

#define _MPRINTF_REPLACE /* use our functions only */
#include <curl/mprintf.h>
#include "curl_memory.h"
/* The last #include file should be: */
#include "memdebug.h"

/*
 Some hackish cast macros based on:
 http://library.gnome.org/devel/glib/unstable/glib-Type-Conversion-Macros.html
*/
#ifndef GNUTLS_POINTER_TO_INT_CAST
#define GNUTLS_POINTER_TO_INT_CAST(p) ((int) (long) (p))
#endif
#ifndef GNUTLS_INT_TO_POINTER_CAST
#define GNUTLS_INT_TO_POINTER_CAST(i) ((void*) (long) (i))
#endif

/* Enable GnuTLS debugging by defining GTLSDEBUG */
/*#define GTLSDEBUG */

#ifdef GTLSDEBUG
static void tls_log_func(int level, const char *str)
{
    fprintf(stderr, "|<%d>| %s", level, str);
}
#endif
static bool gtls_inited = FALSE;

#if defined(GNUTLS_VERSION_NUMBER)
#  if (GNUTLS_VERSION_NUMBER >= 0x020c00)
#    undef gnutls_transport_set_lowat
#    define gnutls_transport_set_lowat(A,B) Curl_nop_stmt
#    define USE_GNUTLS_PRIORITY_SET_DIRECT 1
#  endif
#  if (GNUTLS_VERSION_NUMBER >= 0x020c03)
#    define GNUTLS_MAPS_WINSOCK_ERRORS 1
#  endif

#  ifdef USE_NGHTTP2
#    undef HAS_ALPN
#    if (GNUTLS_VERSION_NUMBER >= 0x030200)
#      define HAS_ALPN
#    endif
#  endif
#endif

/*
 * Custom push and pull callback functions used by GNU TLS to read and write
 * to the socket.  These functions are simple wrappers to send() and recv()
 * (although here using the sread/swrite macros as defined by
 * curl_setup_once.h).
 * We use custom functions rather than the GNU TLS defaults because it allows
 * us to get specific about the fourth "flags" argument, and to use arbitrary
 * private data with gnutls_transport_set_ptr if we wish.
 *
 * When these custom push and pull callbacks fail, GNU TLS checks its own
 * session-specific error variable, and when not set also its own global
 * errno variable, in order to take appropriate action. GNU TLS does not
 * require that the transport is actually a socket. This implies that for
 * Windows builds these callbacks should ideally set the session-specific
 * error variable using function gnutls_transport_set_errno or as a last
 * resort global errno variable using gnutls_transport_set_global_errno,
 * with a transport agnostic error value. This implies that some winsock
 * error translation must take place in these callbacks.
 *
 * Paragraph above applies to GNU TLS versions older than 2.12.3, since
 * this version GNU TLS does its own internal winsock error translation
 * using system_errno() function.
 */

#if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
#  define gtls_EINTR  4
#  define gtls_EIO    5
#  define gtls_EAGAIN 11
static int gtls_mapped_sockerrno(void)
{
  switch(SOCKERRNO) {
  case WSAEWOULDBLOCK:
    return gtls_EAGAIN;
  case WSAEINTR:
    return gtls_EINTR;
  default:
    break;
  }
  return gtls_EIO;
}
#endif

static ssize_t Curl_gtls_push(void *s, const void *buf, size_t len)
{
  ssize_t ret = swrite(GNUTLS_POINTER_TO_INT_CAST(s), buf, len);
#if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
  if(ret < 0)
    gnutls_transport_set_global_errno(gtls_mapped_sockerrno());
#endif
  return ret;
}

static ssize_t Curl_gtls_pull(void *s, void *buf, size_t len)
{
  ssize_t ret = sread(GNUTLS_POINTER_TO_INT_CAST(s), buf, len);
#if defined(USE_WINSOCK) && !defined(GNUTLS_MAPS_WINSOCK_ERRORS)
  if(ret < 0)
    gnutls_transport_set_global_errno(gtls_mapped_sockerrno());
#endif
  return ret;
}

/* Curl_gtls_init()
 *
 * Global GnuTLS init, called from Curl_ssl_init(). This calls functions that
 * are not thread-safe and thus this function itself is not thread-safe and
 * must only be called from within curl_global_init() to keep the thread
 * situation under control!
 */
int Curl_gtls_init(void)
{
  int ret = 1;
  if(!gtls_inited) {
    ret = gnutls_global_init()?0:1;
#ifdef GTLSDEBUG
    gnutls_global_set_log_function(tls_log_func);
    gnutls_global_set_log_level(2);
#endif
    gtls_inited = TRUE;
  }
  return ret;
}

int Curl_gtls_cleanup(void)
{
  if(gtls_inited) {
    gnutls_global_deinit();
    gtls_inited = FALSE;
  }
  return 1;
}

static void showtime(struct SessionHandle *data,
                     const char *text,
                     time_t stamp)
{
  struct tm buffer;
  const struct tm *tm = &buffer;
  CURLcode result = Curl_gmtime(stamp, &buffer);
  if(result)
    return;

  snprintf(data->state.buffer,
           BUFSIZE,
           "\t %s: %s, %02d %s %4d %02d:%02d:%02d GMT\n",
           text,
           Curl_wkday[tm->tm_wday?tm->tm_wday-1:6],
           tm->tm_mday,
           Curl_month[tm->tm_mon],
           tm->tm_year + 1900,
           tm->tm_hour,
           tm->tm_min,
           tm->tm_sec);
  infof(data, "%s\n", data->state.buffer);
}

static gnutls_datum_t load_file (const char *file)
{
  FILE *f;
  gnutls_datum_t loaded_file = { NULL, 0 };
  long filelen;
  void *ptr;

  if(!(f = fopen(file, "r")))
    return loaded_file;
  if(fseek(f, 0, SEEK_END) != 0
     || (filelen = ftell(f)) < 0
     || fseek(f, 0, SEEK_SET) != 0
     || !(ptr = malloc((size_t)filelen)))
    goto out;
  if(fread(ptr, 1, (size_t)filelen, f) < (size_t)filelen) {
    free(ptr);
    goto out;
  }

  loaded_file.data = ptr;
  loaded_file.size = (unsigned int)filelen;
out:
  fclose(f);
  return loaded_file;
}

static void unload_file(gnutls_datum_t data) {
  free(data.data);
}


/* this function does a SSL/TLS (re-)handshake */
static CURLcode handshake(struct connectdata *conn,
                          int sockindex,
                          bool duringconnect,
                          bool nonblocking)
{
  struct SessionHandle *data = conn->data;
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  gnutls_session_t session = conn->ssl[sockindex].session;
  curl_socket_t sockfd = conn->sock[sockindex];
  long timeout_ms;
  int rc;
  int what;

  for(;;) {
    /* check allowed time left */
    timeout_ms = Curl_timeleft(data, NULL, duringconnect);

    if(timeout_ms < 0) {
      /* no need to continue if time already is up */
      failf(data, "SSL connection timeout");
      return CURLE_OPERATION_TIMEDOUT;
    }

    /* if ssl is expecting something, check if it's available. */
    if(connssl->connecting_state == ssl_connect_2_reading
       || connssl->connecting_state == ssl_connect_2_writing) {

      curl_socket_t writefd = ssl_connect_2_writing==
        connssl->connecting_state?sockfd:CURL_SOCKET_BAD;
      curl_socket_t readfd = ssl_connect_2_reading==
        connssl->connecting_state?sockfd:CURL_SOCKET_BAD;

      what = Curl_socket_ready(readfd, writefd,
                               nonblocking?0:
                               timeout_ms?timeout_ms:1000);
      if(what < 0) {
        /* fatal error */
        failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
        return CURLE_SSL_CONNECT_ERROR;
      }
      else if(0 == what) {
        if(nonblocking)
          return CURLE_OK;
        else if(timeout_ms) {
          /* timeout */
          failf(data, "SSL connection timeout at %ld", timeout_ms);
          return CURLE_OPERATION_TIMEDOUT;
        }
      }
      /* socket is readable or writable */
    }

    rc = gnutls_handshake(session);

    if((rc == GNUTLS_E_AGAIN) || (rc == GNUTLS_E_INTERRUPTED)) {
      connssl->connecting_state =
        gnutls_record_get_direction(session)?
        ssl_connect_2_writing:ssl_connect_2_reading;
      continue;
      if(nonblocking)
        return CURLE_OK;
    }
    else if((rc < 0) && !gnutls_error_is_fatal(rc)) {
      const char *strerr = NULL;

      if(rc == GNUTLS_E_WARNING_ALERT_RECEIVED) {
        int alert = gnutls_alert_get(session);
        strerr = gnutls_alert_get_name(alert);
      }

      if(strerr == NULL)
        strerr = gnutls_strerror(rc);

      failf(data, "gnutls_handshake() warning: %s", strerr);
    }
    else if(rc < 0) {
      const char *strerr = NULL;

      if(rc == GNUTLS_E_FATAL_ALERT_RECEIVED) {
        int alert = gnutls_alert_get(session);
        strerr = gnutls_alert_get_name(alert);
      }

      if(strerr == NULL)
        strerr = gnutls_strerror(rc);

      failf(data, "gnutls_handshake() failed: %s", strerr);
      return CURLE_SSL_CONNECT_ERROR;
    }

    /* Reset our connect state machine */
    connssl->connecting_state = ssl_connect_1;
    return CURLE_OK;
  }
}

static gnutls_x509_crt_fmt_t do_file_type(const char *type)
{
  if(!type || !type[0])
    return GNUTLS_X509_FMT_PEM;
  if(Curl_raw_equal(type, "PEM"))
    return GNUTLS_X509_FMT_PEM;
  if(Curl_raw_equal(type, "DER"))
    return GNUTLS_X509_FMT_DER;
  return -1;
}

static CURLcode
gtls_connect_step1(struct connectdata *conn,
                   int sockindex)
{
  struct SessionHandle *data = conn->data;
  gnutls_session_t session;
  int rc;
  void *ssl_sessionid;
  size_t ssl_idsize;
  bool sni = TRUE; /* default is SNI enabled */
#ifdef ENABLE_IPV6
  struct in6_addr addr;
#else
  struct in_addr addr;
#endif
#ifndef USE_GNUTLS_PRIORITY_SET_DIRECT
  static const int cipher_priority[] = {
  /* These two ciphers were added to GnuTLS as late as ver. 3.0.1,
     but this code path is only ever used for ver. < 2.12.0.
     GNUTLS_CIPHER_AES_128_GCM,
     GNUTLS_CIPHER_AES_256_GCM,
  */
    GNUTLS_CIPHER_AES_128_CBC,
    GNUTLS_CIPHER_AES_256_CBC,
    GNUTLS_CIPHER_CAMELLIA_128_CBC,
    GNUTLS_CIPHER_CAMELLIA_256_CBC,
    GNUTLS_CIPHER_3DES_CBC,
  };
  static const int cert_type_priority[] = { GNUTLS_CRT_X509, 0 };
  static int protocol_priority[] = { 0, 0, 0, 0 };
#else
#define GNUTLS_CIPHERS "NORMAL:-ARCFOUR-128:-CTYPE-ALL:+CTYPE-X509"
/* If GnuTLS was compiled without support for SRP it will error out if SRP is
   requested in the priority string, so treat it specially
 */
#define GNUTLS_SRP "+SRP"
  const char* prioritylist;
  const char *err = NULL;
#endif
#ifdef HAS_ALPN
  int protocols_size = 2;
  gnutls_datum_t protocols[2];
#endif

  if(conn->ssl[sockindex].state == ssl_connection_complete)
    /* to make us tolerant against being called more than once for the
       same connection */
    return CURLE_OK;

  if(!gtls_inited)
    Curl_gtls_init();

  /* GnuTLS only supports SSLv3 and TLSv1 */
  if(data->set.ssl.version == CURL_SSLVERSION_SSLv2) {
    failf(data, "GnuTLS does not support SSLv2");
    return CURLE_SSL_CONNECT_ERROR;
  }
  else if(data->set.ssl.version == CURL_SSLVERSION_SSLv3)
    sni = FALSE; /* SSLv3 has no SNI */

  /* allocate a cred struct */
  rc = gnutls_certificate_allocate_credentials(&conn->ssl[sockindex].cred);
  if(rc != GNUTLS_E_SUCCESS) {
    failf(data, "gnutls_cert_all_cred() failed: %s", gnutls_strerror(rc));
    return CURLE_SSL_CONNECT_ERROR;
  }

#ifdef USE_TLS_SRP
  if(data->set.ssl.authtype == CURL_TLSAUTH_SRP) {
    infof(data, "Using TLS-SRP username: %s\n", data->set.ssl.username);

    rc = gnutls_srp_allocate_client_credentials(
           &conn->ssl[sockindex].srp_client_cred);
    if(rc != GNUTLS_E_SUCCESS) {
      failf(data, "gnutls_srp_allocate_client_cred() failed: %s",
            gnutls_strerror(rc));
      return CURLE_OUT_OF_MEMORY;
    }

    rc = gnutls_srp_set_client_credentials(conn->ssl[sockindex].
                                           srp_client_cred,
                                           data->set.ssl.username,
                                           data->set.ssl.password);
    if(rc != GNUTLS_E_SUCCESS) {
      failf(data, "gnutls_srp_set_client_cred() failed: %s",
            gnutls_strerror(rc));
      return CURLE_BAD_FUNCTION_ARGUMENT;
    }
  }
#endif

  if(data->set.ssl.CAfile) {
    /* set the trusted CA cert bundle file */
    gnutls_certificate_set_verify_flags(conn->ssl[sockindex].cred,
                                        GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT);

    rc = gnutls_certificate_set_x509_trust_file(conn->ssl[sockindex].cred,
                                                data->set.ssl.CAfile,
                                                GNUTLS_X509_FMT_PEM);
    if(rc < 0) {
      infof(data, "error reading ca cert file %s (%s)\n",
            data->set.ssl.CAfile, gnutls_strerror(rc));
      if(data->set.ssl.verifypeer)
        return CURLE_SSL_CACERT_BADFILE;
    }
    else
      infof(data, "found %d certificates in %s\n",
            rc, data->set.ssl.CAfile);
  }

  if(data->set.ssl.CRLfile) {
    /* set the CRL list file */
    rc = gnutls_certificate_set_x509_crl_file(conn->ssl[sockindex].cred,
                                              data->set.ssl.CRLfile,
                                              GNUTLS_X509_FMT_PEM);
    if(rc < 0) {
      failf(data, "error reading crl file %s (%s)",
            data->set.ssl.CRLfile, gnutls_strerror(rc));
      return CURLE_SSL_CRL_BADFILE;
    }
    else
      infof(data, "found %d CRL in %s\n",
            rc, data->set.ssl.CRLfile);
  }

  /* Initialize TLS session as a client */
  rc = gnutls_init(&conn->ssl[sockindex].session, GNUTLS_CLIENT);
  if(rc != GNUTLS_E_SUCCESS) {
    failf(data, "gnutls_init() failed: %d", rc);
    return CURLE_SSL_CONNECT_ERROR;
  }

  /* convenient assign */
  session = conn->ssl[sockindex].session;

  if((0 == Curl_inet_pton(AF_INET, conn->host.name, &addr)) &&
#ifdef ENABLE_IPV6
     (0 == Curl_inet_pton(AF_INET6, conn->host.name, &addr)) &&
#endif
     sni &&
     (gnutls_server_name_set(session, GNUTLS_NAME_DNS, conn->host.name,
                             strlen(conn->host.name)) < 0))
    infof(data, "WARNING: failed to configure server name indication (SNI) "
          "TLS extension\n");

  /* Use default priorities */
  rc = gnutls_set_default_priority(session);
  if(rc != GNUTLS_E_SUCCESS)
    return CURLE_SSL_CONNECT_ERROR;

#ifndef USE_GNUTLS_PRIORITY_SET_DIRECT
  rc = gnutls_cipher_set_priority(session, cipher_priority);
  if(rc != GNUTLS_E_SUCCESS)
    return CURLE_SSL_CONNECT_ERROR;

  /* Sets the priority on the certificate types supported by gnutls. Priority
   is higher for types specified before others. After specifying the types
   you want, you must append a 0. */
  rc = gnutls_certificate_type_set_priority(session, cert_type_priority);
  if(rc != GNUTLS_E_SUCCESS)
    return CURLE_SSL_CONNECT_ERROR;

  if(data->set.ssl.cipher_list != NULL) {
    failf(data, "can't pass a custom cipher list to older GnuTLS"
          " versions");
    return CURLE_SSL_CONNECT_ERROR;
  }

  switch (data->set.ssl.version) {
    case CURL_SSLVERSION_SSLv3:
      protocol_priority[0] = GNUTLS_SSL3;
      break;
    case CURL_SSLVERSION_DEFAULT:
    case CURL_SSLVERSION_TLSv1:
      protocol_priority[0] = GNUTLS_TLS1_0;
      protocol_priority[1] = GNUTLS_TLS1_1;
      protocol_priority[2] = GNUTLS_TLS1_2;
      break;
    case CURL_SSLVERSION_TLSv1_0:
      protocol_priority[0] = GNUTLS_TLS1_0;
      break;
    case CURL_SSLVERSION_TLSv1_1:
      protocol_priority[0] = GNUTLS_TLS1_1;
      break;
    case CURL_SSLVERSION_TLSv1_2:
      protocol_priority[0] = GNUTLS_TLS1_2;
    break;
      case CURL_SSLVERSION_SSLv2:
    default:
      failf(data, "GnuTLS does not support SSLv2");
      return CURLE_SSL_CONNECT_ERROR;
      break;
  }
  rc = gnutls_protocol_set_priority(session, protocol_priority);
  if(rc != GNUTLS_E_SUCCESS) {
    failf(data, "Did you pass a valid GnuTLS cipher list?");
    return CURLE_SSL_CONNECT_ERROR;
  }

#else
  /* Ensure +SRP comes at the *end* of all relevant strings so that it can be
   * removed if a run-time error indicates that SRP is not supported by this
   * GnuTLS version */
  switch (data->set.ssl.version) {
    case CURL_SSLVERSION_SSLv3:
      prioritylist = GNUTLS_CIPHERS ":-VERS-TLS-ALL:+VERS-SSL3.0";
      sni = false;
      break;
    case CURL_SSLVERSION_DEFAULT:
    case CURL_SSLVERSION_TLSv1:
      prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:" GNUTLS_SRP;
      break;
    case CURL_SSLVERSION_TLSv1_0:
      prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
                     "+VERS-TLS1.0:" GNUTLS_SRP;
      break;
    case CURL_SSLVERSION_TLSv1_1:
      prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
                     "+VERS-TLS1.1:" GNUTLS_SRP;
      break;
    case CURL_SSLVERSION_TLSv1_2:
      prioritylist = GNUTLS_CIPHERS ":-VERS-SSL3.0:-VERS-TLS-ALL:"
                     "+VERS-TLS1.2:" GNUTLS_SRP;
      break;
    case CURL_SSLVERSION_SSLv2:
    default:
      failf(data, "GnuTLS does not support SSLv2");
      return CURLE_SSL_CONNECT_ERROR;
      break;
  }
  rc = gnutls_priority_set_direct(session, prioritylist, &err);
  if((rc == GNUTLS_E_INVALID_REQUEST) && err) {
    if(!strcmp(err, GNUTLS_SRP)) {
      /* This GnuTLS was probably compiled without support for SRP.
       * Note that fact and try again without it. */
      int validprioritylen = curlx_uztosi(err - prioritylist);
      char *prioritycopy = strdup(prioritylist);
      if(!prioritycopy)
        return CURLE_OUT_OF_MEMORY;

      infof(data, "This GnuTLS does not support SRP\n");
      if(validprioritylen)
        /* Remove the :+SRP */
        prioritycopy[validprioritylen - 1] = 0;
      rc = gnutls_priority_set_direct(session, prioritycopy, &err);
      free(prioritycopy);
    }
  }
  if(rc != GNUTLS_E_SUCCESS) {
    failf(data, "Error %d setting GnuTLS cipher list starting with %s",
          rc, err);
    return CURLE_SSL_CONNECT_ERROR;
  }
#endif

#ifdef HAS_ALPN
  if(data->set.httpversion == CURL_HTTP_VERSION_2_0) {
    if(data->set.ssl_enable_alpn) {
      protocols[0].data = NGHTTP2_PROTO_VERSION_ID;
      protocols[0].size = NGHTTP2_PROTO_VERSION_ID_LEN;
      protocols[1].data = ALPN_HTTP_1_1;
      protocols[1].size = ALPN_HTTP_1_1_LENGTH;
      gnutls_alpn_set_protocols(session, protocols, protocols_size, 0);
      infof(data, "ALPN, offering %s, %s\n", NGHTTP2_PROTO_VERSION_ID,
            ALPN_HTTP_1_1);
    }
    else {
      infof(data, "SSL, can't negotiate HTTP/2.0 without ALPN\n");
    }
  }
#endif

  if(data->set.str[STRING_CERT]) {
    if(gnutls_certificate_set_x509_key_file(
         conn->ssl[sockindex].cred,
         data->set.str[STRING_CERT],
         data->set.str[STRING_KEY] ?
         data->set.str[STRING_KEY] : data->set.str[STRING_CERT],
         do_file_type(data->set.str[STRING_CERT_TYPE]) ) !=
       GNUTLS_E_SUCCESS) {
      failf(data, "error reading X.509 key or certificate file");
      return CURLE_SSL_CONNECT_ERROR;
    }
  }

#ifdef USE_TLS_SRP
  /* put the credentials to the current session */
  if(data->set.ssl.authtype == CURL_TLSAUTH_SRP) {
    rc = gnutls_credentials_set(session, GNUTLS_CRD_SRP,
                                conn->ssl[sockindex].srp_client_cred);
    if(rc != GNUTLS_E_SUCCESS)
      failf(data, "gnutls_credentials_set() failed: %s", gnutls_strerror(rc));
  }
  else
#endif
    rc = gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE,
                                conn->ssl[sockindex].cred);

  /* set the connection handle (file descriptor for the socket) */
  gnutls_transport_set_ptr(session,
                           GNUTLS_INT_TO_POINTER_CAST(conn->sock[sockindex]));

  /* register callback functions to send and receive data. */
  gnutls_transport_set_push_function(session, Curl_gtls_push);
  gnutls_transport_set_pull_function(session, Curl_gtls_pull);

  /* lowat must be set to zero when using custom push and pull functions. */
  gnutls_transport_set_lowat(session, 0);

  /* This might be a reconnect, so we check for a session ID in the cache
     to speed up things */

  if(!Curl_ssl_getsessionid(conn, &ssl_sessionid, &ssl_idsize)) {
    /* we got a session id, use it! */
    gnutls_session_set_data(session, ssl_sessionid, ssl_idsize);

    /* Informational message */
    infof (data, "SSL re-using session ID\n");
  }

  return CURLE_OK;
}

static Curl_recv gtls_recv;
static Curl_send gtls_send;

static CURLcode
gtls_connect_step3(struct connectdata *conn,
                   int sockindex)
{
  unsigned int cert_list_size;
  const gnutls_datum_t *chainp;
  unsigned int verify_status;
  gnutls_x509_crt_t x509_cert,x509_issuer;
  gnutls_datum_t issuerp;
  char certbuf[256] = ""; /* big enough? */
  size_t size;
  unsigned int algo;
  unsigned int bits;
  time_t certclock;
  const char *ptr;
  struct SessionHandle *data = conn->data;
  gnutls_session_t session = conn->ssl[sockindex].session;
  int rc;
  int incache;
  void *ssl_sessionid;
#ifdef HAS_ALPN
  gnutls_datum_t proto;
#endif
  CURLcode result = CURLE_OK;

  /* This function will return the peer's raw certificate (chain) as sent by
     the peer. These certificates are in raw format (DER encoded for
     X.509). In case of a X.509 then a certificate list may be present. The
     first certificate in the list is the peer's certificate, following the
     issuer's certificate, then the issuer's issuer etc. */

  chainp = gnutls_certificate_get_peers(session, &cert_list_size);
  if(!chainp) {
    if(data->set.ssl.verifypeer ||
       data->set.ssl.verifyhost ||
       data->set.ssl.issuercert) {
#ifdef USE_TLS_SRP
      if(data->set.ssl.authtype == CURL_TLSAUTH_SRP
         && data->set.ssl.username != NULL
         && !data->set.ssl.verifypeer
         && gnutls_cipher_get(session)) {
        /* no peer cert, but auth is ok if we have SRP user and cipher and no
           peer verify */
      }
      else {
#endif
        failf(data, "failed to get server cert");
        return CURLE_PEER_FAILED_VERIFICATION;
#ifdef USE_TLS_SRP
      }
#endif
    }
    infof(data, "\t common name: WARNING couldn't obtain\n");
  }

  if(data->set.ssl.verifypeer) {
    /* This function will try to verify the peer's certificate and return its
       status (trusted, invalid etc.). The value of status should be one or
       more of the gnutls_certificate_status_t enumerated elements bitwise
       or'd. To avoid denial of service attacks some default upper limits
       regarding the certificate key size and chain size are set. To override
       them use gnutls_certificate_set_verify_limits(). */

    rc = gnutls_certificate_verify_peers2(session, &verify_status);
    if(rc < 0) {
      failf(data, "server cert verify failed: %d", rc);
      return CURLE_SSL_CONNECT_ERROR;
    }

    /* verify_status is a bitmask of gnutls_certificate_status bits */
    if(verify_status & GNUTLS_CERT_INVALID) {
      if(data->set.ssl.verifypeer) {
        failf(data, "server certificate verification failed. CAfile: %s "
              "CRLfile: %s", data->set.ssl.CAfile?data->set.ssl.CAfile:"none",
              data->set.ssl.CRLfile?data->set.ssl.CRLfile:"none");
        return CURLE_SSL_CACERT;
      }
      else
        infof(data, "\t server certificate verification FAILED\n");
    }
    else
      infof(data, "\t server certificate verification OK\n");
  }
  else
    infof(data, "\t server certificate verification SKIPPED\n");

  /* initialize an X.509 certificate structure. */
  gnutls_x509_crt_init(&x509_cert);

  if(chainp)
    /* convert the given DER or PEM encoded Certificate to the native
       gnutls_x509_crt_t format */
    gnutls_x509_crt_import(x509_cert, chainp, GNUTLS_X509_FMT_DER);

  if(data->set.ssl.issuercert) {
    gnutls_x509_crt_init(&x509_issuer);
    issuerp = load_file(data->set.ssl.issuercert);
    gnutls_x509_crt_import(x509_issuer, &issuerp, GNUTLS_X509_FMT_PEM);
    rc = gnutls_x509_crt_check_issuer(x509_cert,x509_issuer);
    unload_file(issuerp);
    if(rc <= 0) {
      failf(data, "server certificate issuer check failed (IssuerCert: %s)",
            data->set.ssl.issuercert?data->set.ssl.issuercert:"none");
      return CURLE_SSL_ISSUER_ERROR;
    }
    infof(data,"\t server certificate issuer check OK (Issuer Cert: %s)\n",
          data->set.ssl.issuercert?data->set.ssl.issuercert:"none");
  }

  size=sizeof(certbuf);
  rc = gnutls_x509_crt_get_dn_by_oid(x509_cert, GNUTLS_OID_X520_COMMON_NAME,
                                     0, /* the first and only one */
                                     FALSE,
                                     certbuf,
                                     &size);
  if(rc) {
    infof(data, "error fetching CN from cert:%s\n",
          gnutls_strerror(rc));
  }

  /* This function will check if the given certificate's subject matches the
     given hostname. This is a basic implementation of the matching described
     in RFC2818 (HTTPS), which takes into account wildcards, and the subject
     alternative name PKIX extension. Returns non zero on success, and zero on
     failure. */
  rc = gnutls_x509_crt_check_hostname(x509_cert, conn->host.name);
#if GNUTLS_VERSION_NUMBER < 0x030306
  /* Before 3.3.6, gnutls_x509_crt_check_hostname() didn't check IP
     addresses. */
  if(!rc) {
#ifdef ENABLE_IPV6
    #define use_addr in6_addr
#else
    #define use_addr in_addr
#endif
    unsigned char addrbuf[sizeof(struct use_addr)];
    unsigned char certaddr[sizeof(struct use_addr)];
    size_t addrlen = 0, certaddrlen;
    int i;
    int ret = 0;

    if(Curl_inet_pton(AF_INET, conn->host.name, addrbuf) > 0)
      addrlen = 4;
#ifdef ENABLE_IPV6
    else if(Curl_inet_pton(AF_INET6, conn->host.name, addrbuf) > 0)
      addrlen = 16;
#endif

    if(addrlen) {
      for(i=0; ; i++) {
        certaddrlen = sizeof(certaddr);
        ret = gnutls_x509_crt_get_subject_alt_name(x509_cert, i, certaddr,
                                                   &certaddrlen, NULL);
        /* If this happens, it wasn't an IP address. */
        if(ret == GNUTLS_E_SHORT_MEMORY_BUFFER)
          continue;
        if(ret < 0)
          break;
        if(ret != GNUTLS_SAN_IPADDRESS)
          continue;
        if(certaddrlen == addrlen && !memcmp(addrbuf, certaddr, addrlen)) {
          rc = 1;
          break;
        }
      }
    }
  }
#endif
  if(!rc) {
    if(data->set.ssl.verifyhost) {
      failf(data, "SSL: certificate subject name (%s) does not match "
            "target host name '%s'", certbuf, conn->host.dispname);
      gnutls_x509_crt_deinit(x509_cert);
      return CURLE_PEER_FAILED_VERIFICATION;
    }
    else
      infof(data, "\t common name: %s (does not match '%s')\n",
            certbuf, conn->host.dispname);
  }
  else
    infof(data, "\t common name: %s (matched)\n", certbuf);

  /* Check for time-based validity */
  certclock = gnutls_x509_crt_get_expiration_time(x509_cert);

  if(certclock == (time_t)-1) {
    if(data->set.ssl.verifypeer) {
      failf(data, "server cert expiration date verify failed");
      return CURLE_SSL_CONNECT_ERROR;
    }
    else
      infof(data, "\t server certificate expiration date verify FAILED\n");
  }
  else {
    if(certclock < time(NULL)) {
      if(data->set.ssl.verifypeer) {
        failf(data, "server certificate expiration date has passed.");
        return CURLE_PEER_FAILED_VERIFICATION;
      }
      else
        infof(data, "\t server certificate expiration date FAILED\n");
    }
    else
      infof(data, "\t server certificate expiration date OK\n");
  }

  certclock = gnutls_x509_crt_get_activation_time(x509_cert);

  if(certclock == (time_t)-1) {
    if(data->set.ssl.verifypeer) {
      failf(data, "server cert activation date verify failed");
      return CURLE_SSL_CONNECT_ERROR;
    }
    else
      infof(data, "\t server certificate activation date verify FAILED\n");
  }
  else {
    if(certclock > time(NULL)) {
      if(data->set.ssl.verifypeer) {
        failf(data, "server certificate not activated yet.");
        return CURLE_PEER_FAILED_VERIFICATION;
      }
      else
        infof(data, "\t server certificate activation date FAILED\n");
    }
    else
      infof(data, "\t server certificate activation date OK\n");
  }

  /* Show:

  - ciphers used
  - subject
  - start date
  - expire date
  - common name
  - issuer

  */

  /* public key algorithm's parameters */
  algo = gnutls_x509_crt_get_pk_algorithm(x509_cert, &bits);
  infof(data, "\t certificate public key: %s\n",
        gnutls_pk_algorithm_get_name(algo));

  /* version of the X.509 certificate. */
  infof(data, "\t certificate version: #%d\n",
        gnutls_x509_crt_get_version(x509_cert));


  size = sizeof(certbuf);
  gnutls_x509_crt_get_dn(x509_cert, certbuf, &size);
  infof(data, "\t subject: %s\n", certbuf);

  certclock = gnutls_x509_crt_get_activation_time(x509_cert);
  showtime(data, "start date", certclock);

  certclock = gnutls_x509_crt_get_expiration_time(x509_cert);
  showtime(data, "expire date", certclock);

  size = sizeof(certbuf);
  gnutls_x509_crt_get_issuer_dn(x509_cert, certbuf, &size);
  infof(data, "\t issuer: %s\n", certbuf);

  gnutls_x509_crt_deinit(x509_cert);

  /* compression algorithm (if any) */
  ptr = gnutls_compression_get_name(gnutls_compression_get(session));
  /* the *_get_name() says "NULL" if GNUTLS_COMP_NULL is returned */
  infof(data, "\t compression: %s\n", ptr);

  /* the name of the cipher used. ie 3DES. */
  ptr = gnutls_cipher_get_name(gnutls_cipher_get(session));
  infof(data, "\t cipher: %s\n", ptr);

  /* the MAC algorithms name. ie SHA1 */
  ptr = gnutls_mac_get_name(gnutls_mac_get(session));
  infof(data, "\t MAC: %s\n", ptr);

#ifdef HAS_ALPN
  if(data->set.ssl_enable_alpn) {
    rc = gnutls_alpn_get_selected_protocol(session, &proto);
    if(rc == 0) {
      infof(data, "ALPN, server accepted to use %.*s\n", proto.size,
          proto.data);

      if(proto.size == NGHTTP2_PROTO_VERSION_ID_LEN &&
        memcmp(NGHTTP2_PROTO_VERSION_ID, proto.data,
        NGHTTP2_PROTO_VERSION_ID_LEN) == 0) {
        conn->negnpn = NPN_HTTP2;
      }
      else if(proto.size == ALPN_HTTP_1_1_LENGTH && memcmp(ALPN_HTTP_1_1,
          proto.data, ALPN_HTTP_1_1_LENGTH) == 0) {
        conn->negnpn = NPN_HTTP1_1;
      }
    }
    else {
      infof(data, "ALPN, server did not agree to a protocol\n");
    }
  }
#endif

  conn->ssl[sockindex].state = ssl_connection_complete;
  conn->recv[sockindex] = gtls_recv;
  conn->send[sockindex] = gtls_send;

  {
    /* we always unconditionally get the session id here, as even if we
       already got it from the cache and asked to use it in the connection, it
       might've been rejected and then a new one is in use now and we need to
       detect that. */
    void *connect_sessionid;
    size_t connect_idsize = 0;

    /* get the session ID data size */
    gnutls_session_get_data(session, NULL, &connect_idsize);
    connect_sessionid = malloc(connect_idsize); /* get a buffer for it */

    if(connect_sessionid) {
      /* extract session ID to the allocated buffer */
      gnutls_session_get_data(session, connect_sessionid, &connect_idsize);

      incache = !(Curl_ssl_getsessionid(conn, &ssl_sessionid, NULL));
      if(incache) {
        /* there was one before in the cache, so instead of risking that the
           previous one was rejected, we just kill that and store the new */
        Curl_ssl_delsessionid(conn, ssl_sessionid);
      }

      /* store this session id */
      result = Curl_ssl_addsessionid(conn, connect_sessionid, connect_idsize);
      if(result) {
        free(connect_sessionid);
        result = CURLE_OUT_OF_MEMORY;
      }
    }
    else
      result = CURLE_OUT_OF_MEMORY;
  }

  return result;
}


/*
 * This function is called after the TCP connect has completed. Setup the TLS
 * layer and do all necessary magic.
 */
/* We use connssl->connecting_state to keep track of the connection status;
   there are three states: 'ssl_connect_1' (not started yet or complete),
   'ssl_connect_2_reading' (waiting for data from server), and
   'ssl_connect_2_writing' (waiting to be able to write).
 */
static CURLcode
gtls_connect_common(struct connectdata *conn,
                    int sockindex,
                    bool nonblocking,
                    bool *done)
{
  int rc;
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];

  /* Initiate the connection, if not already done */
  if(ssl_connect_1==connssl->connecting_state) {
    rc = gtls_connect_step1 (conn, sockindex);
    if(rc)
      return rc;
  }

  rc = handshake(conn, sockindex, TRUE, nonblocking);
  if(rc)
    /* handshake() sets its own error message with failf() */
    return rc;

  /* Finish connecting once the handshake is done */
  if(ssl_connect_1==connssl->connecting_state) {
    rc = gtls_connect_step3(conn, sockindex);
    if(rc)
      return rc;
  }

  *done = ssl_connect_1==connssl->connecting_state;

  return CURLE_OK;
}

CURLcode
Curl_gtls_connect_nonblocking(struct connectdata *conn,
                              int sockindex,
                              bool *done)
{
  return gtls_connect_common(conn, sockindex, TRUE, done);
}

CURLcode
Curl_gtls_connect(struct connectdata *conn,
                  int sockindex)

{
  CURLcode retcode;
  bool done = FALSE;

  retcode = gtls_connect_common(conn, sockindex, FALSE, &done);
  if(retcode)
    return retcode;

  DEBUGASSERT(done);

  return CURLE_OK;
}

static ssize_t gtls_send(struct connectdata *conn,
                         int sockindex,
                         const void *mem,
                         size_t len,
                         CURLcode *curlcode)
{
  ssize_t rc = gnutls_record_send(conn->ssl[sockindex].session, mem, len);

  if(rc < 0 ) {
    *curlcode = (rc == GNUTLS_E_AGAIN)
      ? CURLE_AGAIN
      : CURLE_SEND_ERROR;

    rc = -1;
  }

  return rc;
}

void Curl_gtls_close_all(struct SessionHandle *data)
{
  /* FIX: make the OpenSSL code more generic and use parts of it here */
  (void)data;
}

static void close_one(struct connectdata *conn,
                      int idx)
{
  if(conn->ssl[idx].session) {
    gnutls_bye(conn->ssl[idx].session, GNUTLS_SHUT_RDWR);
    gnutls_deinit(conn->ssl[idx].session);
    conn->ssl[idx].session = NULL;
  }
  if(conn->ssl[idx].cred) {
    gnutls_certificate_free_credentials(conn->ssl[idx].cred);
    conn->ssl[idx].cred = NULL;
  }
#ifdef USE_TLS_SRP
  if(conn->ssl[idx].srp_client_cred) {
    gnutls_srp_free_client_credentials(conn->ssl[idx].srp_client_cred);
    conn->ssl[idx].srp_client_cred = NULL;
  }
#endif
}

void Curl_gtls_close(struct connectdata *conn, int sockindex)
{
  close_one(conn, sockindex);
}

/*
 * This function is called to shut down the SSL layer but keep the
 * socket open (CCC - Clear Command Channel)
 */
int Curl_gtls_shutdown(struct connectdata *conn, int sockindex)
{
  ssize_t result;
  int retval = 0;
  struct SessionHandle *data = conn->data;
  int done = 0;
  char buf[120];

  /* This has only been tested on the proftpd server, and the mod_tls code
     sends a close notify alert without waiting for a close notify alert in
     response. Thus we wait for a close notify alert from the server, but
     we do not send one. Let's hope other servers do the same... */

  if(data->set.ftp_ccc == CURLFTPSSL_CCC_ACTIVE)
      gnutls_bye(conn->ssl[sockindex].session, GNUTLS_SHUT_WR);

  if(conn->ssl[sockindex].session) {
    while(!done) {
      int what = Curl_socket_ready(conn->sock[sockindex],
                                   CURL_SOCKET_BAD, SSL_SHUTDOWN_TIMEOUT);
      if(what > 0) {
        /* Something to read, let's do it and hope that it is the close
           notify alert from the server */
        result = gnutls_record_recv(conn->ssl[sockindex].session,
                                    buf, sizeof(buf));
        switch(result) {
        case 0:
          /* This is the expected response. There was no data but only
             the close notify alert */
          done = 1;
          break;
        case GNUTLS_E_AGAIN:
        case GNUTLS_E_INTERRUPTED:
          infof(data, "GNUTLS_E_AGAIN || GNUTLS_E_INTERRUPTED\n");
          break;
        default:
          retval = -1;
          done = 1;
          break;
        }
      }
      else if(0 == what) {
        /* timeout */
        failf(data, "SSL shutdown timeout");
        done = 1;
        break;
      }
      else {
        /* anything that gets here is fatally bad */
        failf(data, "select/poll on SSL socket, errno: %d", SOCKERRNO);
        retval = -1;
        done = 1;
      }
    }
    gnutls_deinit(conn->ssl[sockindex].session);
  }
  gnutls_certificate_free_credentials(conn->ssl[sockindex].cred);

#ifdef USE_TLS_SRP
  if(data->set.ssl.authtype == CURL_TLSAUTH_SRP
     && data->set.ssl.username != NULL)
    gnutls_srp_free_client_credentials(conn->ssl[sockindex].srp_client_cred);
#endif

  conn->ssl[sockindex].cred = NULL;
  conn->ssl[sockindex].session = NULL;

  return retval;
}

static ssize_t gtls_recv(struct connectdata *conn, /* connection data */
                         int num,                  /* socketindex */
                         char *buf,                /* store read data here */
                         size_t buffersize,        /* max amount to read */
                         CURLcode *curlcode)
{
  ssize_t ret;

  ret = gnutls_record_recv(conn->ssl[num].session, buf, buffersize);
  if((ret == GNUTLS_E_AGAIN) || (ret == GNUTLS_E_INTERRUPTED)) {
    *curlcode = CURLE_AGAIN;
    return -1;
  }

  if(ret == GNUTLS_E_REHANDSHAKE) {
    /* BLOCKING call, this is bad but a work-around for now. Fixing this "the
       proper way" takes a whole lot of work. */
    CURLcode rc = handshake(conn, num, FALSE, FALSE);
    if(rc)
      /* handshake() writes error message on its own */
      *curlcode = rc;
    else
      *curlcode = CURLE_AGAIN; /* then return as if this was a wouldblock */
    return -1;
  }

  if(ret < 0) {
    failf(conn->data, "GnuTLS recv error (%d): %s",
          (int)ret, gnutls_strerror((int)ret));
    *curlcode = CURLE_RECV_ERROR;
    return -1;
  }

  return ret;
}

void Curl_gtls_session_free(void *ptr)
{
  free(ptr);
}

size_t Curl_gtls_version(char *buffer, size_t size)
{
  return snprintf(buffer, size, "GnuTLS/%s", gnutls_check_version(NULL));
}

static int Curl_gtls_seed(struct SessionHandle *data)
{
  /* we have the "SSL is seeded" boolean static to prevent multiple
     time-consuming seedings in vain */
  static bool ssl_seeded = FALSE;

  /* Quickly add a bit of entropy */
#ifndef USE_GNUTLS_NETTLE
  gcry_fast_random_poll();
#endif

  if(!ssl_seeded || data->set.str[STRING_SSL_RANDOM_FILE] ||
     data->set.str[STRING_SSL_EGDSOCKET]) {

    /* TODO: to a good job seeding the RNG
       This may involve the gcry_control function and these options:
       GCRYCTL_SET_RANDOM_SEED_FILE
       GCRYCTL_SET_RNDEGD_SOCKET
    */
    ssl_seeded = TRUE;
  }
  return 0;
}

/* data might be NULL! */
int Curl_gtls_random(struct SessionHandle *data,
                     unsigned char *entropy,
                     size_t length)
{
#if defined(USE_GNUTLS_NETTLE)
  (void)data;
  gnutls_rnd(GNUTLS_RND_RANDOM, entropy, length);
#elif defined(USE_GNUTLS)
  if(data)
    Curl_gtls_seed(data); /* Initiate the seed if not already done */
  gcry_randomize(entropy, length, GCRY_STRONG_RANDOM);
#endif
  return 0;
}

void Curl_gtls_md5sum(unsigned char *tmp, /* input */
                      size_t tmplen,
                      unsigned char *md5sum, /* output */
                      size_t md5len)
{
#if defined(USE_GNUTLS_NETTLE)
  struct md5_ctx MD5pw;
  md5_init(&MD5pw);
  md5_update(&MD5pw, (unsigned int)tmplen, tmp);
  md5_digest(&MD5pw, (unsigned int)md5len, md5sum);
#elif defined(USE_GNUTLS)
  gcry_md_hd_t MD5pw;
  gcry_md_open(&MD5pw, GCRY_MD_MD5, 0);
  gcry_md_write(MD5pw, tmp, tmplen);
  memcpy(md5sum, gcry_md_read (MD5pw, 0), md5len);
  gcry_md_close(MD5pw);
#endif
}

#endif /* USE_GNUTLS */