summaryrefslogtreecommitdiff
path: root/lib/vtls/cyassl.c
blob: ba5ee1548675c0805b9e1287c720f367d7adcd6a (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
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2017, 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.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 CyaSSL-specific code for the TLS/SSL layer. No code
 * but vtls.c should ever call or use these functions.
 *
 */

#include "curl_setup.h"

#ifdef USE_CYASSL

#define WOLFSSL_OPTIONS_IGNORE_SYS
/* CyaSSL's version.h, which should contain only the version, should come
before all other CyaSSL includes and be immediately followed by build config
aka options.h. https://curl.haxx.se/mail/lib-2015-04/0069.html */
#include <cyassl/version.h>
#if defined(HAVE_CYASSL_OPTIONS_H) && (LIBCYASSL_VERSION_HEX > 0x03004008)
#if defined(CYASSL_API) || defined(WOLFSSL_API)
/* Safety measure. If either is defined some API include was already included
and that's a problem since options.h hasn't been included yet. */
#error "CyaSSL API was included before the CyaSSL build options."
#endif
#include <cyassl/options.h>
#endif

/* To determine what functions are available we rely on one or both of:
   - the user's options.h generated by CyaSSL/wolfSSL
   - the symbols detected by curl's configure
   Since they are markedly different from one another, and one or the other may
   not be available, we do some checking below to bring things in sync. */

/* HAVE_ALPN is wolfSSL's build time symbol for enabling ALPN in options.h. */
#ifndef HAVE_ALPN
#ifdef HAVE_WOLFSSL_USEALPN
#define HAVE_ALPN
#endif
#endif

/* WOLFSSL_ALLOW_SSLV3 is wolfSSL's build time symbol for enabling SSLv3 in
   options.h, but is only seen in >= 3.6.6 since that's when they started
   disabling SSLv3 by default. */
#ifndef WOLFSSL_ALLOW_SSLV3
#if (LIBCYASSL_VERSION_HEX < 0x03006006) || \
    defined(HAVE_WOLFSSLV3_CLIENT_METHOD)
#define WOLFSSL_ALLOW_SSLV3
#endif
#endif

/* HAVE_SUPPORTED_CURVES is wolfSSL's build time symbol for enabling the ECC
   supported curve extension in options.h. Note ECC is enabled separately. */
#ifndef HAVE_SUPPORTED_CURVES
#if defined(HAVE_CYASSL_CTX_USESUPPORTEDCURVE) || \
    defined(HAVE_WOLFSSL_CTX_USESUPPORTEDCURVE)
#define HAVE_SUPPORTED_CURVES
#endif
#endif

#ifdef HAVE_LIMITS_H
#include <limits.h>
#endif

#include "urldata.h"
#include "sendf.h"
#include "inet_pton.h"
#include "vtls.h"
#include "parsedate.h"
#include "connect.h" /* for the connect timeout */
#include "select.h"
#include "strcase.h"
#include "x509asn1.h"
#include "curl_printf.h"

#include <cyassl/openssl/ssl.h>
#include <cyassl/ssl.h>
#ifdef HAVE_CYASSL_ERROR_SSL_H
#include <cyassl/error-ssl.h>
#else
#include <cyassl/error.h>
#endif
#include <cyassl/ctaocrypt/random.h>
#include <cyassl/ctaocrypt/sha256.h>

#include "cyassl.h"

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

#if LIBCYASSL_VERSION_HEX < 0x02007002 /* < 2.7.2 */
#define CYASSL_MAX_ERROR_SZ 80
#endif

/* KEEP_PEER_CERT is a product of the presence of build time symbol
   OPENSSL_EXTRA without NO_CERTS, depending on the version. KEEP_PEER_CERT is
   in wolfSSL's settings.h, and the latter two are build time symbols in
   options.h. */
#ifndef KEEP_PEER_CERT
#if defined(HAVE_CYASSL_GET_PEER_CERTIFICATE) || \
    defined(HAVE_WOLFSSL_GET_PEER_CERTIFICATE) || \
    (defined(OPENSSL_EXTRA) && !defined(NO_CERTS))
#define KEEP_PEER_CERT
#endif
#endif

struct ssl_backend_data {
  SSL_CTX* ctx;
  SSL*     handle;
};

#define BACKEND connssl->backend

static Curl_recv cyassl_recv;
static Curl_send cyassl_send;


static int do_file_type(const char *type)
{
  if(!type || !type[0])
    return SSL_FILETYPE_PEM;
  if(strcasecompare(type, "PEM"))
    return SSL_FILETYPE_PEM;
  if(strcasecompare(type, "DER"))
    return SSL_FILETYPE_ASN1;
  return -1;
}

/*
 * This function loads all the client/CA certificates and CRLs. Setup the TLS
 * layer and do all necessary magic.
 */
static CURLcode
cyassl_connect_step1(struct connectdata *conn,
                     int sockindex)
{
  char error_buffer[CYASSL_MAX_ERROR_SZ];
  char *ciphers;
  struct Curl_easy *data = conn->data;
  struct ssl_connect_data* connssl = &conn->ssl[sockindex];
  SSL_METHOD* req_method = NULL;
  curl_socket_t sockfd = conn->sock[sockindex];
#ifdef HAVE_SNI
  bool sni = FALSE;
#define use_sni(x)  sni = (x)
#else
#define use_sni(x)  Curl_nop_stmt
#endif

  if(connssl->state == ssl_connection_complete)
    return CURLE_OK;

  if(SSL_CONN_CONFIG(version_max) != CURL_SSLVERSION_MAX_NONE) {
    failf(data, "CyaSSL does not support to set maximum SSL/TLS version");
    return CURLE_SSL_CONNECT_ERROR;
  }

  /* check to see if we've been told to use an explicit SSL/TLS version */
  switch(SSL_CONN_CONFIG(version)) {
  case CURL_SSLVERSION_DEFAULT:
  case CURL_SSLVERSION_TLSv1:
#if LIBCYASSL_VERSION_HEX >= 0x03003000 /* >= 3.3.0 */
    /* minimum protocol version is set later after the CTX object is created */
    req_method = SSLv23_client_method();
#else
    infof(data, "CyaSSL <3.3.0 cannot be configured to use TLS 1.0-1.2, "
          "TLS 1.0 is used exclusively\n");
    req_method = TLSv1_client_method();
#endif
    use_sni(TRUE);
    break;
  case CURL_SSLVERSION_TLSv1_0:
    req_method = TLSv1_client_method();
    use_sni(TRUE);
    break;
  case CURL_SSLVERSION_TLSv1_1:
    req_method = TLSv1_1_client_method();
    use_sni(TRUE);
    break;
  case CURL_SSLVERSION_TLSv1_2:
    req_method = TLSv1_2_client_method();
    use_sni(TRUE);
    break;
  case CURL_SSLVERSION_TLSv1_3:
    failf(data, "CyaSSL: TLS 1.3 is not yet supported");
    return CURLE_SSL_CONNECT_ERROR;
  case CURL_SSLVERSION_SSLv3:
#ifdef WOLFSSL_ALLOW_SSLV3
    req_method = SSLv3_client_method();
    use_sni(FALSE);
#else
    failf(data, "CyaSSL does not support SSLv3");
    return CURLE_NOT_BUILT_IN;
#endif
    break;
  case CURL_SSLVERSION_SSLv2:
    failf(data, "CyaSSL does not support SSLv2");
    return CURLE_SSL_CONNECT_ERROR;
  default:
    failf(data, "Unrecognized parameter passed via CURLOPT_SSLVERSION");
    return CURLE_SSL_CONNECT_ERROR;
  }

  if(!req_method) {
    failf(data, "SSL: couldn't create a method!");
    return CURLE_OUT_OF_MEMORY;
  }

  if(BACKEND->ctx)
    SSL_CTX_free(BACKEND->ctx);
  BACKEND->ctx = SSL_CTX_new(req_method);

  if(!BACKEND->ctx) {
    failf(data, "SSL: couldn't create a context!");
    return CURLE_OUT_OF_MEMORY;
  }

  switch(SSL_CONN_CONFIG(version)) {
  case CURL_SSLVERSION_DEFAULT:
  case CURL_SSLVERSION_TLSv1:
#if LIBCYASSL_VERSION_HEX > 0x03004006 /* > 3.4.6 */
    /* Versions 3.3.0 to 3.4.6 we know the minimum protocol version is whatever
    minimum version of TLS was built in and at least TLS 1.0. For later library
    versions that could change (eg TLS 1.0 built in but defaults to TLS 1.1) so
    we have this short circuit evaluation to find the minimum supported TLS
    version. We use wolfSSL_CTX_SetMinVersion and not CyaSSL_SetMinVersion
    because only the former will work before the user's CTX callback is called.
    */
    if((wolfSSL_CTX_SetMinVersion(BACKEND->ctx, WOLFSSL_TLSV1) != 1) &&
       (wolfSSL_CTX_SetMinVersion(BACKEND->ctx, WOLFSSL_TLSV1_1) != 1) &&
       (wolfSSL_CTX_SetMinVersion(BACKEND->ctx, WOLFSSL_TLSV1_2) != 1)) {
      failf(data, "SSL: couldn't set the minimum protocol version");
      return CURLE_SSL_CONNECT_ERROR;
    }
#endif
    break;
  }

  ciphers = SSL_CONN_CONFIG(cipher_list);
  if(ciphers) {
    if(!SSL_CTX_set_cipher_list(BACKEND->ctx, ciphers)) {
      failf(data, "failed setting cipher list: %s", ciphers);
      return CURLE_SSL_CIPHER;
    }
    infof(data, "Cipher selection: %s\n", ciphers);
  }

#ifndef NO_FILESYSTEM
  /* load trusted cacert */
  if(SSL_CONN_CONFIG(CAfile)) {
    if(1 != SSL_CTX_load_verify_locations(BACKEND->ctx,
                                      SSL_CONN_CONFIG(CAfile),
                                      SSL_CONN_CONFIG(CApath))) {
      if(SSL_CONN_CONFIG(verifypeer)) {
        /* Fail if we insist on successfully verifying the server. */
        failf(data, "error setting certificate verify locations:\n"
              "  CAfile: %s\n  CApath: %s",
              SSL_CONN_CONFIG(CAfile)?
              SSL_CONN_CONFIG(CAfile): "none",
              SSL_CONN_CONFIG(CApath)?
              SSL_CONN_CONFIG(CApath) : "none");
        return CURLE_SSL_CACERT_BADFILE;
      }
      else {
        /* Just continue with a warning if no strict certificate
           verification is required. */
        infof(data, "error setting certificate verify locations,"
              " continuing anyway:\n");
      }
    }
    else {
      /* Everything is fine. */
      infof(data, "successfully set certificate verify locations:\n");
    }
    infof(data,
          "  CAfile: %s\n"
          "  CApath: %s\n",
          SSL_CONN_CONFIG(CAfile) ? SSL_CONN_CONFIG(CAfile):
          "none",
          SSL_CONN_CONFIG(CApath) ? SSL_CONN_CONFIG(CApath):
          "none");
  }

  /* Load the client certificate, and private key */
  if(SSL_SET_OPTION(cert) && SSL_SET_OPTION(key)) {
    int file_type = do_file_type(SSL_SET_OPTION(cert_type));

    if(SSL_CTX_use_certificate_file(BACKEND->ctx, SSL_SET_OPTION(cert),
                                     file_type) != 1) {
      failf(data, "unable to use client certificate (no key or wrong pass"
            " phrase?)");
      return CURLE_SSL_CONNECT_ERROR;
    }

    file_type = do_file_type(SSL_SET_OPTION(key_type));
    if(SSL_CTX_use_PrivateKey_file(BACKEND->ctx, SSL_SET_OPTION(key),
                                    file_type) != 1) {
      failf(data, "unable to set private key");
      return CURLE_SSL_CONNECT_ERROR;
    }
  }
#endif /* !NO_FILESYSTEM */

  /* SSL always tries to verify the peer, this only says whether it should
   * fail to connect if the verification fails, or if it should continue
   * anyway. In the latter case the result of the verification is checked with
   * SSL_get_verify_result() below. */
  SSL_CTX_set_verify(BACKEND->ctx,
                     SSL_CONN_CONFIG(verifypeer)?SSL_VERIFY_PEER:
                                                 SSL_VERIFY_NONE,
                     NULL);

#ifdef HAVE_SNI
  if(sni) {
    struct in_addr addr4;
#ifdef ENABLE_IPV6
    struct in6_addr addr6;
#endif
    const char * const hostname = SSL_IS_PROXY() ? conn->http_proxy.host.name :
      conn->host.name;
    size_t hostname_len = strlen(hostname);
    if((hostname_len < USHRT_MAX) &&
       (0 == Curl_inet_pton(AF_INET, hostname, &addr4)) &&
#ifdef ENABLE_IPV6
       (0 == Curl_inet_pton(AF_INET6, hostname, &addr6)) &&
#endif
       (CyaSSL_CTX_UseSNI(BACKEND->ctx, CYASSL_SNI_HOST_NAME, hostname,
                          (unsigned short)hostname_len) != 1)) {
      infof(data, "WARNING: failed to configure server name indication (SNI) "
            "TLS extension\n");
    }
  }
#endif

#ifdef HAVE_SUPPORTED_CURVES
  /* CyaSSL/wolfSSL does not send the supported ECC curves ext automatically:
     https://github.com/wolfSSL/wolfssl/issues/366
     The supported curves below are those also supported by OpenSSL 1.0.2 and
     in the same order. */
  CyaSSL_CTX_UseSupportedCurve(BACKEND->ctx, 0x17); /* secp256r1 */
  CyaSSL_CTX_UseSupportedCurve(BACKEND->ctx, 0x19); /* secp521r1 */
  CyaSSL_CTX_UseSupportedCurve(BACKEND->ctx, 0x18); /* secp384r1 */
#endif

  /* give application a chance to interfere with SSL set up. */
  if(data->set.ssl.fsslctx) {
    CURLcode result = CURLE_OK;
    result = (*data->set.ssl.fsslctx)(data, BACKEND->ctx,
                                      data->set.ssl.fsslctxp);
    if(result) {
      failf(data, "error signaled by ssl ctx callback");
      return result;
    }
  }
#ifdef NO_FILESYSTEM
  else if(SSL_CONN_CONFIG(verifypeer)) {
    failf(data, "SSL: Certificates couldn't be loaded because CyaSSL was built"
          " with \"no filesystem\". Either disable peer verification"
          " (insecure) or if you are building an application with libcurl you"
          " can load certificates via CURLOPT_SSL_CTX_FUNCTION.");
    return CURLE_SSL_CONNECT_ERROR;
  }
#endif

  /* Let's make an SSL structure */
  if(BACKEND->handle)
    SSL_free(BACKEND->handle);
  BACKEND->handle = SSL_new(BACKEND->ctx);
  if(!BACKEND->handle) {
    failf(data, "SSL: couldn't create a context (handle)!");
    return CURLE_OUT_OF_MEMORY;
  }

#ifdef HAVE_ALPN
  if(conn->bits.tls_enable_alpn) {
    char protocols[128];
    *protocols = '\0';

    /* wolfSSL's ALPN protocol name list format is a comma separated string of
       protocols in descending order of preference, eg: "h2,http/1.1" */

#ifdef USE_NGHTTP2
    if(data->set.httpversion >= CURL_HTTP_VERSION_2) {
      strcpy(protocols + strlen(protocols), NGHTTP2_PROTO_VERSION_ID ",");
      infof(data, "ALPN, offering %s\n", NGHTTP2_PROTO_VERSION_ID);
    }
#endif

    strcpy(protocols + strlen(protocols), ALPN_HTTP_1_1);
    infof(data, "ALPN, offering %s\n", ALPN_HTTP_1_1);

    if(wolfSSL_UseALPN(BACKEND->handle, protocols,
                       (unsigned)strlen(protocols),
                       WOLFSSL_ALPN_CONTINUE_ON_MISMATCH) != SSL_SUCCESS) {
      failf(data, "SSL: failed setting ALPN protocols");
      return CURLE_SSL_CONNECT_ERROR;
    }
  }
#endif /* HAVE_ALPN */

  /* Check if there's a cached ID we can/should use here! */
  if(SSL_SET_OPTION(primary.sessionid)) {
    void *ssl_sessionid = NULL;

    Curl_ssl_sessionid_lock(conn);
    if(!Curl_ssl_getsessionid(conn, &ssl_sessionid, NULL, sockindex)) {
      /* we got a session id, use it! */
      if(!SSL_set_session(BACKEND->handle, ssl_sessionid)) {
        Curl_ssl_sessionid_unlock(conn);
        failf(data, "SSL: SSL_set_session failed: %s",
              ERR_error_string(SSL_get_error(BACKEND->handle, 0),
              error_buffer));
        return CURLE_SSL_CONNECT_ERROR;
      }
      /* Informational message */
      infof(data, "SSL re-using session ID\n");
    }
    Curl_ssl_sessionid_unlock(conn);
  }

  /* pass the raw socket into the SSL layer */
  if(!SSL_set_fd(BACKEND->handle, (int)sockfd)) {
    failf(data, "SSL: SSL_set_fd failed");
    return CURLE_SSL_CONNECT_ERROR;
  }

  connssl->connecting_state = ssl_connect_2;
  return CURLE_OK;
}


static CURLcode
cyassl_connect_step2(struct connectdata *conn,
                     int sockindex)
{
  int ret = -1;
  struct Curl_easy *data = conn->data;
  struct ssl_connect_data* connssl = &conn->ssl[sockindex];
  const char * const hostname = SSL_IS_PROXY() ? conn->http_proxy.host.name :
    conn->host.name;
  const char * const dispname = SSL_IS_PROXY() ?
    conn->http_proxy.host.dispname : conn->host.dispname;
  const char * const pinnedpubkey = SSL_IS_PROXY() ?
                        data->set.str[STRING_SSL_PINNEDPUBLICKEY_PROXY] :
                        data->set.str[STRING_SSL_PINNEDPUBLICKEY_ORIG];

  conn->recv[sockindex] = cyassl_recv;
  conn->send[sockindex] = cyassl_send;

  /* Enable RFC2818 checks */
  if(SSL_CONN_CONFIG(verifyhost)) {
    ret = CyaSSL_check_domain_name(BACKEND->handle, hostname);
    if(ret == SSL_FAILURE)
      return CURLE_OUT_OF_MEMORY;
  }

  ret = SSL_connect(BACKEND->handle);
  if(ret != 1) {
    char error_buffer[CYASSL_MAX_ERROR_SZ];
    int  detail = SSL_get_error(BACKEND->handle, ret);

    if(SSL_ERROR_WANT_READ == detail) {
      connssl->connecting_state = ssl_connect_2_reading;
      return CURLE_OK;
    }
    else if(SSL_ERROR_WANT_WRITE == detail) {
      connssl->connecting_state = ssl_connect_2_writing;
      return CURLE_OK;
    }
    /* There is no easy way to override only the CN matching.
     * This will enable the override of both mismatching SubjectAltNames
     * as also mismatching CN fields */
    else if(DOMAIN_NAME_MISMATCH == detail) {
#if 1
      failf(data, "\tsubject alt name(s) or common name do not match \"%s\"\n",
            dispname);
      return CURLE_PEER_FAILED_VERIFICATION;
#else
      /* When the CyaSSL_check_domain_name() is used and you desire to continue
       * on a DOMAIN_NAME_MISMATCH, i.e. 'conn->ssl_config.verifyhost == 0',
       * CyaSSL version 2.4.0 will fail with an INCOMPLETE_DATA error. The only
       * way to do this is currently to switch the CyaSSL_check_domain_name()
       * in and out based on the 'conn->ssl_config.verifyhost' value. */
      if(SSL_CONN_CONFIG(verifyhost)) {
        failf(data,
              "\tsubject alt name(s) or common name do not match \"%s\"\n",
              dispname);
        return CURLE_PEER_FAILED_VERIFICATION;
      }
      else {
        infof(data,
              "\tsubject alt name(s) and/or common name do not match \"%s\"\n",
              dispname);
        return CURLE_OK;
      }
#endif
    }
#if LIBCYASSL_VERSION_HEX >= 0x02007000 /* 2.7.0 */
    else if(ASN_NO_SIGNER_E == detail) {
      if(SSL_CONN_CONFIG(verifypeer)) {
        failf(data, "\tCA signer not available for verification\n");
        return CURLE_SSL_CACERT_BADFILE;
      }
      else {
        /* Just continue with a warning if no strict certificate
           verification is required. */
        infof(data, "CA signer not available for verification, "
                    "continuing anyway\n");
      }
    }
#endif
    else {
      failf(data, "SSL_connect failed with error %d: %s", detail,
          ERR_error_string(detail, error_buffer));
      return CURLE_SSL_CONNECT_ERROR;
    }
  }

  if(pinnedpubkey) {
#ifdef KEEP_PEER_CERT
    X509 *x509;
    const char *x509_der;
    int x509_der_len;
    curl_X509certificate x509_parsed;
    curl_asn1Element *pubkey;
    CURLcode result;

    x509 = SSL_get_peer_certificate(BACKEND->handle);
    if(!x509) {
      failf(data, "SSL: failed retrieving server certificate");
      return CURLE_SSL_PINNEDPUBKEYNOTMATCH;
    }

    x509_der = (const char *)CyaSSL_X509_get_der(x509, &x509_der_len);
    if(!x509_der) {
      failf(data, "SSL: failed retrieving ASN.1 server certificate");
      return CURLE_SSL_PINNEDPUBKEYNOTMATCH;
    }

    memset(&x509_parsed, 0, sizeof x509_parsed);
    if(Curl_parseX509(&x509_parsed, x509_der, x509_der + x509_der_len))
      return CURLE_SSL_PINNEDPUBKEYNOTMATCH;

    pubkey = &x509_parsed.subjectPublicKeyInfo;
    if(!pubkey->header || pubkey->end <= pubkey->header) {
      failf(data, "SSL: failed retrieving public key from server certificate");
      return CURLE_SSL_PINNEDPUBKEYNOTMATCH;
    }

    result = Curl_pin_peer_pubkey(data,
                                  pinnedpubkey,
                                  (const unsigned char *)pubkey->header,
                                  (size_t)(pubkey->end - pubkey->header));
    if(result) {
      failf(data, "SSL: public key does not match pinned public key!");
      return result;
    }
#else
    failf(data, "Library lacks pinning support built-in");
    return CURLE_NOT_BUILT_IN;
#endif
  }

#ifdef HAVE_ALPN
  if(conn->bits.tls_enable_alpn) {
    int rc;
    char *protocol = NULL;
    unsigned short protocol_len = 0;

    rc = wolfSSL_ALPN_GetProtocol(BACKEND->handle, &protocol, &protocol_len);

    if(rc == SSL_SUCCESS) {
      infof(data, "ALPN, server accepted to use %.*s\n", protocol_len,
            protocol);

      if(protocol_len == ALPN_HTTP_1_1_LENGTH &&
         !memcmp(protocol, ALPN_HTTP_1_1, ALPN_HTTP_1_1_LENGTH))
        conn->negnpn = CURL_HTTP_VERSION_1_1;
#ifdef USE_NGHTTP2
      else if(data->set.httpversion >= CURL_HTTP_VERSION_2 &&
              protocol_len == NGHTTP2_PROTO_VERSION_ID_LEN &&
              !memcmp(protocol, NGHTTP2_PROTO_VERSION_ID,
                      NGHTTP2_PROTO_VERSION_ID_LEN))
        conn->negnpn = CURL_HTTP_VERSION_2;
#endif
      else
        infof(data, "ALPN, unrecognized protocol %.*s\n", protocol_len,
              protocol);
    }
    else if(rc == SSL_ALPN_NOT_FOUND)
      infof(data, "ALPN, server did not agree to a protocol\n");
    else {
      failf(data, "ALPN, failure getting protocol, error %d", rc);
      return CURLE_SSL_CONNECT_ERROR;
    }
  }
#endif /* HAVE_ALPN */

  connssl->connecting_state = ssl_connect_3;
#if (LIBCYASSL_VERSION_HEX >= 0x03009010)
  infof(data, "SSL connection using %s / %s\n",
        wolfSSL_get_version(BACKEND->handle),
        wolfSSL_get_cipher_name(BACKEND->handle));
#else
  infof(data, "SSL connected\n");
#endif

  return CURLE_OK;
}


static CURLcode
cyassl_connect_step3(struct connectdata *conn,
                     int sockindex)
{
  CURLcode result = CURLE_OK;
  struct Curl_easy *data = conn->data;
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];

  DEBUGASSERT(ssl_connect_3 == connssl->connecting_state);

  if(SSL_SET_OPTION(primary.sessionid)) {
    bool incache;
    SSL_SESSION *our_ssl_sessionid;
    void *old_ssl_sessionid = NULL;

    our_ssl_sessionid = SSL_get_session(BACKEND->handle);

    Curl_ssl_sessionid_lock(conn);
    incache = !(Curl_ssl_getsessionid(conn, &old_ssl_sessionid, NULL,
                                      sockindex));
    if(incache) {
      if(old_ssl_sessionid != our_ssl_sessionid) {
        infof(data, "old SSL session ID is stale, removing\n");
        Curl_ssl_delsessionid(conn, old_ssl_sessionid);
        incache = FALSE;
      }
    }

    if(!incache) {
      result = Curl_ssl_addsessionid(conn, our_ssl_sessionid,
                                     0 /* unknown size */, sockindex);
      if(result) {
        Curl_ssl_sessionid_unlock(conn);
        failf(data, "failed to store ssl session");
        return result;
      }
    }
    Curl_ssl_sessionid_unlock(conn);
  }

  connssl->connecting_state = ssl_connect_done;

  return result;
}


static ssize_t cyassl_send(struct connectdata *conn,
                           int sockindex,
                           const void *mem,
                           size_t len,
                           CURLcode *curlcode)
{
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  char error_buffer[CYASSL_MAX_ERROR_SZ];
  int  memlen = (len > (size_t)INT_MAX) ? INT_MAX : (int)len;
  int  rc     = SSL_write(BACKEND->handle, mem, memlen);

  if(rc < 0) {
    int err = SSL_get_error(BACKEND->handle, rc);

    switch(err) {
    case SSL_ERROR_WANT_READ:
    case SSL_ERROR_WANT_WRITE:
      /* there's data pending, re-invoke SSL_write() */
      *curlcode = CURLE_AGAIN;
      return -1;
    default:
      failf(conn->data, "SSL write: %s, errno %d",
            ERR_error_string(err, error_buffer),
            SOCKERRNO);
      *curlcode = CURLE_SEND_ERROR;
      return -1;
    }
  }
  return rc;
}

static void Curl_cyassl_close(struct connectdata *conn, int sockindex)
{
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];

  if(BACKEND->handle) {
    (void)SSL_shutdown(BACKEND->handle);
    SSL_free(BACKEND->handle);
    BACKEND->handle = NULL;
  }
  if(BACKEND->ctx) {
    SSL_CTX_free(BACKEND->ctx);
    BACKEND->ctx = NULL;
  }
}

static ssize_t cyassl_recv(struct connectdata *conn,
                           int num,
                           char *buf,
                           size_t buffersize,
                           CURLcode *curlcode)
{
  struct ssl_connect_data *connssl = &conn->ssl[num];
  char error_buffer[CYASSL_MAX_ERROR_SZ];
  int  buffsize = (buffersize > (size_t)INT_MAX) ? INT_MAX : (int)buffersize;
  int  nread    = SSL_read(BACKEND->handle, buf, buffsize);

  if(nread < 0) {
    int err = SSL_get_error(BACKEND->handle, nread);

    switch(err) {
    case SSL_ERROR_ZERO_RETURN: /* no more data */
      break;
    case SSL_ERROR_WANT_READ:
    case SSL_ERROR_WANT_WRITE:
      /* there's data pending, re-invoke SSL_read() */
      *curlcode = CURLE_AGAIN;
      return -1;
    default:
      failf(conn->data, "SSL read: %s, errno %d",
            ERR_error_string(err, error_buffer),
            SOCKERRNO);
      *curlcode = CURLE_RECV_ERROR;
      return -1;
    }
  }
  return nread;
}


static void Curl_cyassl_session_free(void *ptr)
{
  (void)ptr;
  /* CyaSSL reuses sessions on own, no free */
}


static size_t Curl_cyassl_version(char *buffer, size_t size)
{
#if LIBCYASSL_VERSION_HEX >= 0x03006000
  return snprintf(buffer, size, "wolfSSL/%s", wolfSSL_lib_version());
#elif defined(WOLFSSL_VERSION)
  return snprintf(buffer, size, "wolfSSL/%s", WOLFSSL_VERSION);
#elif defined(CYASSL_VERSION)
  return snprintf(buffer, size, "CyaSSL/%s", CYASSL_VERSION);
#else
  return snprintf(buffer, size, "CyaSSL/%s", "<1.8.8");
#endif
}


static int Curl_cyassl_init(void)
{
  return (CyaSSL_Init() == SSL_SUCCESS);
}


static bool Curl_cyassl_data_pending(const struct connectdata* conn,
                                     int connindex)
{
  const struct ssl_connect_data *connssl = &conn->ssl[connindex];
  if(BACKEND->handle)   /* SSL is in use */
    return (0 != SSL_pending(BACKEND->handle)) ? TRUE : FALSE;
  else
    return FALSE;
}


/*
 * This function is called to shut down the SSL layer but keep the
 * socket open (CCC - Clear Command Channel)
 */
static int Curl_cyassl_shutdown(struct connectdata *conn, int sockindex)
{
  int retval = 0;
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];

  if(BACKEND->handle) {
    SSL_free(BACKEND->handle);
    BACKEND->handle = NULL;
  }
  return retval;
}


static CURLcode
cyassl_connect_common(struct connectdata *conn,
                      int sockindex,
                      bool nonblocking,
                      bool *done)
{
  CURLcode result;
  struct Curl_easy *data = conn->data;
  struct ssl_connect_data *connssl = &conn->ssl[sockindex];
  curl_socket_t sockfd = conn->sock[sockindex];
  time_t timeout_ms;
  int what;

  /* check if the connection has already been established */
  if(ssl_connection_complete == connssl->state) {
    *done = TRUE;
    return CURLE_OK;
  }

  if(ssl_connect_1 == connssl->connecting_state) {
    /* Find out how much more time we're allowed */
    timeout_ms = Curl_timeleft(data, NULL, TRUE);

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

    result = cyassl_connect_step1(conn, sockindex);
    if(result)
      return result;
  }

  while(ssl_connect_2 == connssl->connecting_state ||
        ssl_connect_2_reading == connssl->connecting_state ||
        ssl_connect_2_writing == connssl->connecting_state) {

    /* check allowed time left */
    timeout_ms = Curl_timeleft(data, NULL, TRUE);

    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_check(readfd, CURL_SOCKET_BAD, writefd,
                               nonblocking?0:timeout_ms);
      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) {
          *done = FALSE;
          return CURLE_OK;
        }
        else {
          /* timeout */
          failf(data, "SSL connection timeout");
          return CURLE_OPERATION_TIMEDOUT;
        }
      }
      /* socket is readable or writable */
    }

    /* Run transaction, and return to the caller if it failed or if
     * this connection is part of a multi handle and this loop would
     * execute again. This permits the owner of a multi handle to
     * abort a connection attempt before step2 has completed while
     * ensuring that a client using select() or epoll() will always
     * have a valid fdset to wait on.
     */
    result = cyassl_connect_step2(conn, sockindex);
    if(result || (nonblocking &&
                  (ssl_connect_2 == connssl->connecting_state ||
                   ssl_connect_2_reading == connssl->connecting_state ||
                   ssl_connect_2_writing == connssl->connecting_state)))
      return result;
  } /* repeat step2 until all transactions are done. */

  if(ssl_connect_3 == connssl->connecting_state) {
    result = cyassl_connect_step3(conn, sockindex);
    if(result)
      return result;
  }

  if(ssl_connect_done == connssl->connecting_state) {
    connssl->state = ssl_connection_complete;
    conn->recv[sockindex] = cyassl_recv;
    conn->send[sockindex] = cyassl_send;
    *done = TRUE;
  }
  else
    *done = FALSE;

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

  return CURLE_OK;
}


static CURLcode Curl_cyassl_connect_nonblocking(struct connectdata *conn,
                                                int sockindex, bool *done)
{
  return cyassl_connect_common(conn, sockindex, TRUE, done);
}


static CURLcode Curl_cyassl_connect(struct connectdata *conn, int sockindex)
{
  CURLcode result;
  bool done = FALSE;

  result = cyassl_connect_common(conn, sockindex, FALSE, &done);
  if(result)
    return result;

  DEBUGASSERT(done);

  return CURLE_OK;
}

static CURLcode Curl_cyassl_random(struct Curl_easy *data,
                                   unsigned char *entropy, size_t length)
{
  RNG rng;
  (void)data;
  if(InitRng(&rng))
    return CURLE_FAILED_INIT;
  if(length > UINT_MAX)
    return CURLE_FAILED_INIT;
  if(RNG_GenerateBlock(&rng, entropy, (unsigned)length))
    return CURLE_FAILED_INIT;
  return CURLE_OK;
}

static void Curl_cyassl_sha256sum(const unsigned char *tmp, /* input */
                                  size_t tmplen,
                                  unsigned char *sha256sum /* output */,
                                  size_t unused)
{
  Sha256 SHA256pw;
  (void)unused;
  InitSha256(&SHA256pw);
  Sha256Update(&SHA256pw, tmp, (word32)tmplen);
  Sha256Final(&SHA256pw, sha256sum);
}

static void *Curl_cyassl_get_internals(struct ssl_connect_data *connssl,
                                       CURLINFO info UNUSED_PARAM)
{
  (void)info;
  return BACKEND->handle;
}

const struct Curl_ssl Curl_ssl_cyassl = {
  { CURLSSLBACKEND_WOLFSSL, "WolfSSL" }, /* info */

  0, /* have_ca_path */
  0, /* have_certinfo */
#ifdef KEEP_PEER_CERT
  1, /* have_pinnedpubkey */
#else
  0, /* have_pinnedpubkey */
#endif
  1, /* have_ssl_ctx */
  0, /* support_https_proxy */

  sizeof(struct ssl_backend_data),

  Curl_cyassl_init,                /* init */
  Curl_none_cleanup,               /* cleanup */
  Curl_cyassl_version,             /* version */
  Curl_none_check_cxn,             /* check_cxn */
  Curl_cyassl_shutdown,            /* shutdown */
  Curl_cyassl_data_pending,        /* data_pending */
  Curl_cyassl_random,              /* random */
  Curl_none_cert_status_request,   /* cert_status_request */
  Curl_cyassl_connect,             /* connect */
  Curl_cyassl_connect_nonblocking, /* connect_nonblocking */
  Curl_cyassl_get_internals,       /* get_internals */
  Curl_cyassl_close,               /* close */
  Curl_none_close_all,             /* close_all */
  Curl_cyassl_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 */
  Curl_none_md5sum,                /* md5sum */
  Curl_cyassl_sha256sum            /* sha256sum */
};

#endif