aboutsummaryrefslogtreecommitdiff
path: root/lib/x509asn1.c
blob: 728562692da7d3e51c32ffa487341f5146339fb0 (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
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2015, 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.
 *
 ***************************************************************************/

#include "curl_setup.h"

#if defined(USE_GSKIT) || defined(USE_NSS) || defined(USE_GNUTLS) || \
    defined(USE_CYASSL)

#include <curl/curl.h>
#include "urldata.h"
#include "strequal.h"
#include "hostcheck.h"
#include "vtls/vtls.h"
#include "sendf.h"
#include "inet_pton.h"
#include "curl_base64.h"
#include "x509asn1.h"
#include "curl_printf.h"
#include "curl_memory.h"
/* The last #include file should be: */
#include "memdebug.h"


/* ASN.1 OIDs. */
static const char       cnOID[] = "2.5.4.3";    /* Common name. */
static const char       sanOID[] = "2.5.29.17"; /* Subject alternative name. */

static const curl_OID   OIDtable[] = {
  { "1.2.840.10040.4.1",        "dsa" },
  { "1.2.840.10040.4.3",        "dsa-with-sha1" },
  { "1.2.840.10045.2.1",        "ecPublicKey" },
  { "1.2.840.10045.3.0.1",      "c2pnb163v1" },
  { "1.2.840.10045.4.1",        "ecdsa-with-SHA1" },
  { "1.2.840.10046.2.1",        "dhpublicnumber" },
  { "1.2.840.113549.1.1.1",     "rsaEncryption" },
  { "1.2.840.113549.1.1.2",     "md2WithRSAEncryption" },
  { "1.2.840.113549.1.1.4",     "md5WithRSAEncryption" },
  { "1.2.840.113549.1.1.5",     "sha1WithRSAEncryption" },
  { "1.2.840.113549.1.1.10",    "RSASSA-PSS" },
  { "1.2.840.113549.1.1.14",    "sha224WithRSAEncryption" },
  { "1.2.840.113549.1.1.11",    "sha256WithRSAEncryption" },
  { "1.2.840.113549.1.1.12",    "sha384WithRSAEncryption" },
  { "1.2.840.113549.1.1.13",    "sha512WithRSAEncryption" },
  { "1.2.840.113549.2.2",       "md2" },
  { "1.2.840.113549.2.5",       "md5" },
  { "1.3.14.3.2.26",            "sha1" },
  { cnOID,                      "CN" },
  { "2.5.4.4",                  "SN" },
  { "2.5.4.5",                  "serialNumber" },
  { "2.5.4.6",                  "C" },
  { "2.5.4.7",                  "L" },
  { "2.5.4.8",                  "ST" },
  { "2.5.4.9",                  "streetAddress" },
  { "2.5.4.10",                 "O" },
  { "2.5.4.11",                 "OU" },
  { "2.5.4.12",                 "title" },
  { "2.5.4.13",                 "description" },
  { "2.5.4.17",                 "postalCode" },
  { "2.5.4.41",                 "name" },
  { "2.5.4.42",                 "givenName" },
  { "2.5.4.43",                 "initials" },
  { "2.5.4.44",                 "generationQualifier" },
  { "2.5.4.45",                 "X500UniqueIdentifier" },
  { "2.5.4.46",                 "dnQualifier" },
  { "2.5.4.65",                 "pseudonym" },
  { "1.2.840.113549.1.9.1",     "emailAddress" },
  { "2.5.4.72",                 "role" },
  { sanOID,                     "subjectAltName" },
  { "2.5.29.18",                "issuerAltName" },
  { "2.5.29.19",                "basicConstraints" },
  { "2.16.840.1.101.3.4.2.4",   "sha224" },
  { "2.16.840.1.101.3.4.2.1",   "sha256" },
  { "2.16.840.1.101.3.4.2.2",   "sha384" },
  { "2.16.840.1.101.3.4.2.3",   "sha512" },
  { (const char *) NULL,        (const char *) NULL }
};

/*
 * Lightweight ASN.1 parser.
 * In particular, it does not check for syntactic/lexical errors.
 * It is intended to support certificate information gathering for SSL backends
 * that offer a mean to get certificates as a whole, but do not supply
 * entry points to get particular certificate sub-fields.
 * Please note there is no pretention here to rewrite a full SSL library.
 */


const char * Curl_getASN1Element(curl_asn1Element * elem,
                                 const char * beg, const char * end)
{
  unsigned char b;
  unsigned long len;
  curl_asn1Element lelem;

  /* Get a single ASN.1 element into `elem', parse ASN.1 string at `beg'
     ending at `end'.
     Returns a pointer in source string after the parsed element, or NULL
     if an error occurs. */

  if(beg >= end || !*beg)
    return (const char *) NULL;

  /* Process header byte. */
  elem->header = beg;
  b = (unsigned char) *beg++;
  elem->constructed = (b & 0x20) != 0;
  elem->class = (b >> 6) & 3;
  b &= 0x1F;
  if(b == 0x1F)
    return (const char *) NULL; /* Long tag values not supported here. */
  elem->tag = b;

  /* Process length. */
  if(beg >= end)
    return (const char *) NULL;
  b = (unsigned char) *beg++;
  if(!(b & 0x80))
    len = b;
  else if(!(b &= 0x7F)) {
    /* Unspecified length. Since we have all the data, we can determine the
       effective length by skipping element until an end element is found. */
    if(!elem->constructed)
      return (const char *) NULL;
    elem->beg = beg;
    while(beg < end && *beg) {
      beg = Curl_getASN1Element(&lelem, beg, end);
      if(!beg)
        return (const char *) NULL;
    }
    if(beg >= end)
      return (const char *) NULL;
    elem->end = beg;
    return beg + 1;
  }
  else if(beg + b > end)
    return (const char *) NULL; /* Does not fit in source. */
  else {
    /* Get long length. */
    len = 0;
    do {
      if(len & 0xFF000000L)
        return (const char *) NULL;  /* Lengths > 32 bits are not supported. */
      len = (len << 8) | (unsigned char) *beg++;
    } while(--b);
  }
  if((unsigned long) (end - beg) < len)
    return (const char *) NULL;  /* Element data does not fit in source. */
  elem->beg = beg;
  elem->end = beg + len;
  return elem->end;
}

static const curl_OID * searchOID(const char * oid)
{
  const curl_OID * op;

  /* Search the null terminated OID or OID identifier in local table.
     Return the table entry pointer or NULL if not found. */

  for(op = OIDtable; op->numoid; op++)
    if(!strcmp(op->numoid, oid) || curl_strequal(op->textoid, oid))
      return op;

  return (const curl_OID *) NULL;
}

static const char * bool2str(const char * beg, const char * end)
{
  /* Convert an ASN.1 Boolean value into its string representation.
     Return the dynamically allocated string, or NULL if source is not an
     ASN.1 Boolean value. */

  if(end - beg != 1)
    return (const char *) NULL;
  return strdup(*beg? "TRUE": "FALSE");
}

static const char * octet2str(const char * beg, const char * end)
{
  size_t n = end - beg;
  char * buf;

  /* Convert an ASN.1 octet string to a printable string.
     Return the dynamically allocated string, or NULL if an error occurs. */

  buf = malloc(3 * n + 1);
  if(buf)
    for(n = 0; beg < end; n += 3)
      snprintf(buf + n, 4, "%02x:", *(const unsigned char *) beg++);
  return buf;
}

static const char * bit2str(const char * beg, const char * end)
{
  /* Convert an ASN.1 bit string to a printable string.
     Return the dynamically allocated string, or NULL if an error occurs. */

  if(++beg > end)
    return (const char *) NULL;
  return octet2str(beg, end);
}

static const char * int2str(const char * beg, const char * end)
{
  long val = 0;
  size_t n = end - beg;

  /* Convert an ASN.1 integer value into its string representation.
     Return the dynamically allocated string, or NULL if source is not an
     ASN.1 integer value. */

  if(!n)
    return (const char *) NULL;

  if(n > 4)
    return octet2str(beg, end);

  /* Represent integers <= 32-bit as a single value. */
  if(*beg & 0x80)
    val = ~val;

  do
    val = (val << 8) | *(const unsigned char *) beg++;
  while(beg < end);
  return curl_maprintf("%s%lx", (val < 0 || val >= 10)? "0x": "", val);
}

static ssize_t
utf8asn1str(char * * to, int type, const char * from, const char * end)
{
  size_t inlength = end - from;
  int size = 1;
  size_t outlength;
  int charsize;
  unsigned int wc;
  char * buf;

  /* Perform a lazy conversion from an ASN.1 typed string to UTF8. Allocate the
     destination buffer dynamically. The allocation size will normally be too
     large: this is to avoid buffer overflows.
     Terminate the string with a nul byte and return the converted
     string length. */

  *to = (char *) NULL;
  switch (type) {
  case CURL_ASN1_BMP_STRING:
    size = 2;
    break;
  case CURL_ASN1_UNIVERSAL_STRING:
    size = 4;
    break;
  case CURL_ASN1_NUMERIC_STRING:
  case CURL_ASN1_PRINTABLE_STRING:
  case CURL_ASN1_TELETEX_STRING:
  case CURL_ASN1_IA5_STRING:
  case CURL_ASN1_VISIBLE_STRING:
  case CURL_ASN1_UTF8_STRING:
    break;
  default:
    return -1;  /* Conversion not supported. */
  }

  if(inlength % size)
    return -1;  /* Length inconsistent with character size. */
  buf = malloc(4 * (inlength / size) + 1);
  if(!buf)
    return -1;  /* Not enough memory. */

  if(type == CURL_ASN1_UTF8_STRING) {
    /* Just copy. */
    outlength = inlength;
    if(outlength)
      memcpy(buf, from, outlength);
  }
  else {
    for(outlength = 0; from < end;) {
      wc = 0;
      switch (size) {
      case 4:
        wc = (wc << 8) | *(const unsigned char *) from++;
        wc = (wc << 8) | *(const unsigned char *) from++;
        /* fallthrough */
      case 2:
        wc = (wc << 8) | *(const unsigned char *) from++;
        /* fallthrough */
      default: /* case 1: */
        wc = (wc << 8) | *(const unsigned char *) from++;
      }
      charsize = 1;
      if(wc >= 0x00000080) {
        if(wc >= 0x00000800) {
          if(wc >= 0x00010000) {
            if(wc >= 0x00200000) {
              free(buf);
              return -1;        /* Invalid char. size for target encoding. */
            }
            buf[outlength + 3] = (char) (0x80 | (wc & 0x3F));
            wc = (wc >> 6) | 0x00010000;
            charsize++;
          }
          buf[outlength + 2] = (char) (0x80 | (wc & 0x3F));
          wc = (wc >> 6) | 0x00000800;
          charsize++;
        }
        buf[outlength + 1] = (char) (0x80 | (wc & 0x3F));
        wc = (wc >> 6) | 0x000000C0;
        charsize++;
      }
      buf[outlength] = (char) wc;
      outlength += charsize;
    }
  }
  buf[outlength] = '\0';
  *to = buf;
  return outlength;
}

static const char * string2str(int type, const char * beg, const char * end)
{
  char * buf;

  /* Convert an ASN.1 String into its UTF-8 string representation.
     Return the dynamically allocated string, or NULL if an error occurs. */

  if(utf8asn1str(&buf, type, beg, end) < 0)
    return (const char *) NULL;
  return buf;
}

static int encodeUint(char * buf, int n, unsigned int x)
{
  int i = 0;
  unsigned int y = x / 10;

  /* Decimal ASCII encode unsigned integer `x' in the `n'-byte buffer at `buf'.
     Return the total number of encoded digits, even if larger than `n'. */

  if(y) {
    i += encodeUint(buf, n, y);
    x -= y * 10;
  }
  if(i < n)
    buf[i] = (char) ('0' + x);
  i++;
  if(i < n)
    buf[i] = '\0';      /* Store a terminator if possible. */
  return i;
}

static int encodeOID(char * buf, int n, const char * beg, const char * end)
{
  int i = 0;
  unsigned int x;
  unsigned int y;

  /* Convert an ASN.1 OID into its dotted string representation.
     Store the result in th `n'-byte buffer at `buf'.
     Return the converted string length, or -1 if an error occurs. */

  /* Process the first two numbers. */
  y = *(const unsigned char *) beg++;
  x = y / 40;
  y -= x * 40;
  i += encodeUint(buf + i, n - i, x);
  if(i < n)
    buf[i] = '.';
  i++;
  i += encodeUint(buf + i, n - i, y);

  /* Process the trailing numbers. */
  while(beg < end) {
    if(i < n)
      buf[i] = '.';
    i++;
    x = 0;
    do {
      if(x & 0xFF000000)
        return -1;
      y = *(const unsigned char *) beg++;
      x = (x << 7) | (y & 0x7F);
    } while(y & 0x80);
    i += encodeUint(buf + i, n - i, x);
  }
  if(i < n)
    buf[i] = '\0';
  return i;
}

static const char * OID2str(const char * beg, const char * end, bool symbolic)
{
  char * buf = (char *) NULL;
  const curl_OID * op;
  int n;

  /* Convert an ASN.1 OID into its dotted or symbolic string representation.
     Return the dynamically allocated string, or NULL if an error occurs. */

  if(beg < end) {
    n = encodeOID((char *) NULL, -1, beg, end);
    if(n >= 0) {
      buf = malloc(n + 1);
      if(buf) {
        encodeOID(buf, n, beg, end);
        buf[n] = '\0';

        if(symbolic) {
          op = searchOID(buf);
          if(op) {
            free(buf);
            buf = strdup(op->textoid);
          }
        }
      }
    }
  }
  return buf;
}

static const char * GTime2str(const char * beg, const char * end)
{
  const char * tzp;
  const char * fracp;
  char sec1, sec2;
  size_t fracl;
  size_t tzl;
  const char * sep = "";

  /* Convert an ASN.1 Generalized time to a printable string.
     Return the dynamically allocated string, or NULL if an error occurs. */

  for(fracp = beg; fracp < end && *fracp >= '0' && *fracp <= '9'; fracp++)
    ;

  /* Get seconds digits. */
  sec1 = '0';
  switch (fracp - beg - 12) {
  case 0:
    sec2 = '0';
    break;
  case 2:
    sec1 = fracp[-2];
  case 1:
    sec2 = fracp[-1];
    break;
  default:
    return (const char *) NULL;
  }

  /* Scan for timezone, measure fractional seconds. */
  tzp = fracp;
  fracl = 0;
  if(fracp < end && (*fracp == '.' || *fracp == ',')) {
    fracp++;
    do
      tzp++;
    while(tzp < end && *tzp >= '0' && *tzp <= '9');
    /* Strip leading zeroes in fractional seconds. */
    for(fracl = tzp - fracp - 1; fracl && fracp[fracl - 1] == '0'; fracl--)
      ;
  }

  /* Process timezone. */
  if(tzp >= end)
    ;           /* Nothing to do. */
  else if(*tzp == 'Z') {
    tzp = " GMT";
    end = tzp + 4;
  }
  else {
    sep = " ";
    tzp++;
  }

  tzl = end - tzp;
  return curl_maprintf("%.4s-%.2s-%.2s %.2s:%.2s:%c%c%s%.*s%s%.*s",
                       beg, beg + 4, beg + 6,
                       beg + 8, beg + 10, sec1, sec2,
                       fracl? ".": "", fracl, fracp,
                       sep, tzl, tzp);
}

static const char * UTime2str(const char * beg, const char * end)
{
  const char * tzp;
  size_t tzl;
  const char * sec;

  /* Convert an ASN.1 UTC time to a printable string.
     Return the dynamically allocated string, or NULL if an error occurs. */

  for(tzp = beg; tzp < end && *tzp >= '0' && *tzp <= '9'; tzp++)
    ;
  /* Get the seconds. */
  sec = beg + 10;
  switch (tzp - sec) {
  case 0:
    sec = "00";
  case 2:
    break;
  default:
    return (const char *) NULL;
  }

  /* Process timezone. */
  if(tzp >= end)
    return (const char *) NULL;
  if(*tzp == 'Z') {
    tzp = "GMT";
    end = tzp + 3;
  }
  else
    tzp++;

  tzl = end - tzp;
  return curl_maprintf("%u%.2s-%.2s-%.2s %.2s:%.2s:%.2s %.*s",
                       20 - (*beg >= '5'), beg, beg + 2, beg + 4,
                       beg + 6, beg + 8, sec,
                       tzl, tzp);
}

const char * Curl_ASN1tostr(curl_asn1Element * elem, int type)
{
  /* Convert an ASN.1 element to a printable string.
     Return the dynamically allocated string, or NULL if an error occurs. */

  if(elem->constructed)
    return (const char *) NULL; /* No conversion of structured elements. */

  if(!type)
    type = elem->tag;   /* Type not forced: use element tag as type. */

  switch (type) {
  case CURL_ASN1_BOOLEAN:
    return bool2str(elem->beg, elem->end);
  case CURL_ASN1_INTEGER:
  case CURL_ASN1_ENUMERATED:
    return int2str(elem->beg, elem->end);
  case CURL_ASN1_BIT_STRING:
    return bit2str(elem->beg, elem->end);
  case CURL_ASN1_OCTET_STRING:
    return octet2str(elem->beg, elem->end);
  case CURL_ASN1_NULL:
    return strdup("");
  case CURL_ASN1_OBJECT_IDENTIFIER:
    return OID2str(elem->beg, elem->end, TRUE);
  case CURL_ASN1_UTC_TIME:
    return UTime2str(elem->beg, elem->end);
  case CURL_ASN1_GENERALIZED_TIME:
    return GTime2str(elem->beg, elem->end);
  case CURL_ASN1_UTF8_STRING:
  case CURL_ASN1_NUMERIC_STRING:
  case CURL_ASN1_PRINTABLE_STRING:
  case CURL_ASN1_TELETEX_STRING:
  case CURL_ASN1_IA5_STRING:
  case CURL_ASN1_VISIBLE_STRING:
  case CURL_ASN1_UNIVERSAL_STRING:
  case CURL_ASN1_BMP_STRING:
    return string2str(type, elem->beg, elem->end);
  }

  return (const char *) NULL;   /* Unsupported. */
}

static ssize_t encodeDN(char * buf, size_t n, curl_asn1Element * dn)
{
  curl_asn1Element rdn;
  curl_asn1Element atv;
  curl_asn1Element oid;
  curl_asn1Element value;
  size_t l = 0;
  const char * p1;
  const char * p2;
  const char * p3;
  const char * str;

  /* ASCII encode distinguished name at `dn' into the `n'-byte buffer at `buf'.
     Return the total string length, even if larger than `n'. */

  for(p1 = dn->beg; p1 < dn->end;) {
    p1 = Curl_getASN1Element(&rdn, p1, dn->end);
    for(p2 = rdn.beg; p2 < rdn.end;) {
      p2 = Curl_getASN1Element(&atv, p2, rdn.end);
      p3 = Curl_getASN1Element(&oid, atv.beg, atv.end);
      Curl_getASN1Element(&value, p3, atv.end);
      str = Curl_ASN1tostr(&oid, 0);
      if(!str)
        return -1;

      /* Encode delimiter.
         If attribute has a short uppercase name, delimiter is ", ". */
      if(l) {
        for(p3 = str; isupper(*p3); p3++)
          ;
        for(p3 = (*p3 || p3 - str > 2)? "/": ", "; *p3; p3++) {
          if(l < n)
            buf[l] = *p3;
          l++;
        }
      }

      /* Encode attribute name. */
      for(p3 = str; *p3; p3++) {
        if(l < n)
          buf[l] = *p3;
        l++;
      }
      free((char *) str);

      /* Generate equal sign. */
      if(l < n)
        buf[l] = '=';
      l++;

      /* Generate value. */
      str = Curl_ASN1tostr(&value, 0);
      if(!str)
        return -1;
      for(p3 = str; *p3; p3++) {
        if(l < n)
          buf[l] = *p3;
        l++;
      }
      free((char *) str);
    }
  }

  return l;
}

const char * Curl_DNtostr(curl_asn1Element * dn)
{
  char * buf = (char *) NULL;
  ssize_t n = encodeDN(buf, 0, dn);

  /* Convert an ASN.1 distinguished name into a printable string.
     Return the dynamically allocated string, or NULL if an error occurs. */

  if(n >= 0) {
    buf = malloc(n + 1);
    if(buf) {
      encodeDN(buf, n + 1, dn);
      buf[n] = '\0';
    }
  }
  return (const char *) buf;
}

/*
 * X509 parser.
 */

void Curl_parseX509(curl_X509certificate * cert,
                    const char * beg, const char * end)
{
  curl_asn1Element elem;
  curl_asn1Element tbsCertificate;
  const char * ccp;
  static const char defaultVersion = 0;  /* v1. */

  /* ASN.1 parse an X509 certificate into structure subfields.
     Syntax is assumed to have already been checked by the SSL backend.
     See RFC 5280. */

  cert->certificate.header = NULL;
  cert->certificate.beg = beg;
  cert->certificate.end = end;

  /* Get the sequence content. */
  Curl_getASN1Element(&elem, beg, end);
  beg = elem.beg;
  end = elem.end;

  /* Get tbsCertificate. */
  beg = Curl_getASN1Element(&tbsCertificate, beg, end);
  /* Skip the signatureAlgorithm. */
  beg = Curl_getASN1Element(&cert->signatureAlgorithm, beg, end);
  /* Get the signatureValue. */
  Curl_getASN1Element(&cert->signature, beg, end);

  /* Parse TBSCertificate. */
  beg = tbsCertificate.beg;
  end = tbsCertificate.end;
  /* Get optional version, get serialNumber. */
  cert->version.header = NULL;
  cert->version.beg = &defaultVersion;
  cert->version.end = &defaultVersion + sizeof defaultVersion;;
  beg = Curl_getASN1Element(&elem, beg, end);
  if(elem.tag == 0) {
    Curl_getASN1Element(&cert->version, elem.beg, elem.end);
    beg = Curl_getASN1Element(&elem, beg, end);
  }
  cert->serialNumber = elem;
  /* Get signature algorithm. */
  beg = Curl_getASN1Element(&cert->signatureAlgorithm, beg, end);
  /* Get issuer. */
  beg = Curl_getASN1Element(&cert->issuer, beg, end);
  /* Get notBefore and notAfter. */
  beg = Curl_getASN1Element(&elem, beg, end);
  ccp = Curl_getASN1Element(&cert->notBefore, elem.beg, elem.end);
  Curl_getASN1Element(&cert->notAfter, ccp, elem.end);
  /* Get subject. */
  beg = Curl_getASN1Element(&cert->subject, beg, end);
  /* Get subjectPublicKeyAlgorithm and subjectPublicKey. */
  beg = Curl_getASN1Element(&cert->subjectPublicKeyInfo, beg, end);
  ccp = Curl_getASN1Element(&cert->subjectPublicKeyAlgorithm,
                            cert->subjectPublicKeyInfo.beg,
                            cert->subjectPublicKeyInfo.end);
  Curl_getASN1Element(&cert->subjectPublicKey, ccp,
                      cert->subjectPublicKeyInfo.end);
  /* Get optional issuerUiqueID, subjectUniqueID and extensions. */
  cert->issuerUniqueID.tag = cert->subjectUniqueID.tag = 0;
  cert->extensions.tag = elem.tag = 0;
  cert->issuerUniqueID.header = cert->subjectUniqueID.header = NULL;
  cert->issuerUniqueID.beg = cert->issuerUniqueID.end = "";
  cert->subjectUniqueID.beg = cert->subjectUniqueID.end = "";
  cert->extensions.header = NULL;
  cert->extensions.beg = cert->extensions.end = "";
  if(beg < end)
    beg = Curl_getASN1Element(&elem, beg, end);
  if(elem.tag == 1) {
    cert->issuerUniqueID = elem;
    if(beg < end)
      beg = Curl_getASN1Element(&elem, beg, end);
  }
  if(elem.tag == 2) {
    cert->subjectUniqueID = elem;
    if(beg < end)
      beg = Curl_getASN1Element(&elem, beg, end);
  }
  if(elem.tag == 3)
    Curl_getASN1Element(&cert->extensions, elem.beg, elem.end);
}

static size_t copySubstring(char * to, const char * from)
{
  size_t i;

  /* Copy at most 64-characters, terminate with a newline and returns the
     effective number of stored characters. */

  for(i = 0; i < 64; i++) {
    to[i] = *from;
    if(!*from++)
      break;
  }

  to[i++] = '\n';
  return i;
}

static const char * dumpAlgo(curl_asn1Element * param,
                             const char * beg, const char * end)
{
  curl_asn1Element oid;

  /* Get algorithm parameters and return algorithm name. */

  beg = Curl_getASN1Element(&oid, beg, end);
  param->header = NULL;
  param->tag = 0;
  param->beg = param->end = end;
  if(beg < end)
    Curl_getASN1Element(param, beg, end);
  return OID2str(oid.beg, oid.end, TRUE);
}

static void do_pubkey_field(struct SessionHandle * data, int certnum,
                            const char * label, curl_asn1Element * elem)
{
  const char * output;

  /* Generate a certificate information record for the public key. */

  output = Curl_ASN1tostr(elem, 0);
  if(output) {
    if(data->set.ssl.certinfo)
      Curl_ssl_push_certinfo(data, certnum, label, output);
    if(!certnum)
      infof(data, "   %s: %s\n", label, output);
    free((char *) output);
  }
}

static void do_pubkey(struct SessionHandle * data, int certnum,
                      const char * algo, curl_asn1Element * param,
                      curl_asn1Element * pubkey)
{
  curl_asn1Element elem;
  curl_asn1Element pk;
  const char * p;
  const char * q;
  unsigned long len;
  unsigned int i;

  /* Generate all information records for the public key. */

  /* Get the public key (single element). */
  Curl_getASN1Element(&pk, pubkey->beg + 1, pubkey->end);

  if(curl_strequal(algo, "rsaEncryption")) {
    p = Curl_getASN1Element(&elem, pk.beg, pk.end);
    /* Compute key length. */
    for(q = elem.beg; !*q && q < elem.end; q++)
      ;
    len = (unsigned long)((elem.end - q) * 8);
    if(len)
      for(i = *(unsigned char *) q; !(i & 0x80); i <<= 1)
        len--;
    if(len > 32)
      elem.beg = q;     /* Strip leading zero bytes. */
    if(!certnum)
      infof(data, "   RSA Public Key (%lu bits)\n", len);
    if(data->set.ssl.certinfo) {
      q = curl_maprintf("%lu", len);
      if(q) {
        Curl_ssl_push_certinfo(data, certnum, "RSA Public Key", q);
        free((char *) q);
      }
    }
    /* Generate coefficients. */
    do_pubkey_field(data, certnum, "rsa(n)", &elem);
    Curl_getASN1Element(&elem, p, pk.end);
    do_pubkey_field(data, certnum, "rsa(e)", &elem);
  }
  else if(curl_strequal(algo, "dsa")) {
    p = Curl_getASN1Element(&elem, param->beg, param->end);
    do_pubkey_field(data, certnum, "dsa(p)", &elem);
    p = Curl_getASN1Element(&elem, p, param->end);
    do_pubkey_field(data, certnum, "dsa(q)", &elem);
    Curl_getASN1Element(&elem, p, param->end);
    do_pubkey_field(data, certnum, "dsa(g)", &elem);
    do_pubkey_field(data, certnum, "dsa(pub_key)", &pk);
  }
  else if(curl_strequal(algo, "dhpublicnumber")) {
    p = Curl_getASN1Element(&elem, param->beg, param->end);
    do_pubkey_field(data, certnum, "dh(p)", &elem);
    Curl_getASN1Element(&elem, param->beg, param->end);
    do_pubkey_field(data, certnum, "dh(g)", &elem);
    do_pubkey_field(data, certnum, "dh(pub_key)", &pk);
  }
#if 0 /* Patent-encumbered. */
  else if(curl_strequal(algo, "ecPublicKey")) {
    /* Left TODO. */
  }
#endif
}

CURLcode Curl_extract_certinfo(struct connectdata * conn,
                               int certnum,
                               const char * beg,
                               const char * end)
{
  curl_X509certificate cert;
  struct SessionHandle * data = conn->data;
  curl_asn1Element param;
  const char * ccp;
  char * cp1;
  size_t cl1;
  char * cp2;
  CURLcode result;
  unsigned long version;
  size_t i;
  size_t j;

  if(!data->set.ssl.certinfo)
    if(certnum)
      return CURLE_OK;

  /* Prepare the certificate information for curl_easy_getinfo(). */

  /* Extract the certificate ASN.1 elements. */
  Curl_parseX509(&cert, beg, end);

  /* Subject. */
  ccp = Curl_DNtostr(&cert.subject);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Subject", ccp);
  if(!certnum)
    infof(data, "%2d Subject: %s\n", certnum, ccp);
  free((char *) ccp);

  /* Issuer. */
  ccp = Curl_DNtostr(&cert.issuer);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Issuer", ccp);
  if(!certnum)
    infof(data, "   Issuer: %s\n", ccp);
  free((char *) ccp);

  /* Version (always fits in less than 32 bits). */
  version = 0;
  for(ccp = cert.version.beg; ccp < cert.version.end; ccp++)
    version = (version << 8) | *(const unsigned char *) ccp;
  if(data->set.ssl.certinfo) {
    ccp = curl_maprintf("%lx", version);
    if(!ccp)
      return CURLE_OUT_OF_MEMORY;
    Curl_ssl_push_certinfo(data, certnum, "Version", ccp);
    free((char *) ccp);
  }
  if(!certnum)
    infof(data, "   Version: %lu (0x%lx)\n", version + 1, version);

  /* Serial number. */
  ccp = Curl_ASN1tostr(&cert.serialNumber, 0);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Serial Number", ccp);
  if(!certnum)
    infof(data, "   Serial Number: %s\n", ccp);
  free((char *) ccp);

  /* Signature algorithm .*/
  ccp = dumpAlgo(&param, cert.signatureAlgorithm.beg,
                 cert.signatureAlgorithm.end);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Signature Algorithm", ccp);
  if(!certnum)
    infof(data, "   Signature Algorithm: %s\n", ccp);
  free((char *) ccp);

  /* Start Date. */
  ccp = Curl_ASN1tostr(&cert.notBefore, 0);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Start Date", ccp);
  if(!certnum)
    infof(data, "   Start Date: %s\n", ccp);
  free((char *) ccp);

  /* Expire Date. */
  ccp = Curl_ASN1tostr(&cert.notAfter, 0);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Expire Date", ccp);
  if(!certnum)
    infof(data, "   Expire Date: %s\n", ccp);
  free((char *) ccp);

  /* Public Key Algorithm. */
  ccp = dumpAlgo(&param, cert.subjectPublicKeyAlgorithm.beg,
                 cert.subjectPublicKeyAlgorithm.end);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Public Key Algorithm", ccp);
  if(!certnum)
    infof(data, "   Public Key Algorithm: %s\n", ccp);
  do_pubkey(data, certnum, ccp, &param, &cert.subjectPublicKey);
  free((char *) ccp);

/* TODO: extensions. */

  /* Signature. */
  ccp = Curl_ASN1tostr(&cert.signature, 0);
  if(!ccp)
    return CURLE_OUT_OF_MEMORY;
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Signature", ccp);
  if(!certnum)
    infof(data, "   Signature: %s\n", ccp);
  free((char *) ccp);

  /* Generate PEM certificate. */
  result = Curl_base64_encode(data, cert.certificate.beg,
                              cert.certificate.end - cert.certificate.beg,
                              &cp1, &cl1);
  if(result)
    return result;
  /* Compute the number of characters in final certificate string. Format is:
     -----BEGIN CERTIFICATE-----\n
     <max 64 base64 characters>\n
     .
     .
     .
     -----END CERTIFICATE-----\n
   */
  i = 28 + cl1 + (cl1 + 64 - 1) / 64 + 26;
  cp2 = malloc(i + 1);
  if(!cp2) {
    free(cp1);
    return CURLE_OUT_OF_MEMORY;
  }
  /* Build the certificate string. */
  i = copySubstring(cp2, "-----BEGIN CERTIFICATE-----");
  for(j = 0; j < cl1; j += 64)
    i += copySubstring(cp2 + i, cp1 + j);
  i += copySubstring(cp2 + i, "-----END CERTIFICATE-----");
  cp2[i] = '\0';
  free(cp1);
  if(data->set.ssl.certinfo)
    Curl_ssl_push_certinfo(data, certnum, "Cert", cp2);
  if(!certnum)
    infof(data, "%s\n", cp2);
  free(cp2);
  return CURLE_OK;
}

#endif /* USE_GSKIT or USE_NSS or USE_GNUTLS or USE_CYASSL */

#if defined(USE_GSKIT)

static const char * checkOID(const char * beg, const char * end,
                             const char * oid)
{
  curl_asn1Element e;
  const char * ccp;
  const char * p;
  bool matched;

  /* Check if first ASN.1 element at `beg' is the given OID.
     Return a pointer in the source after the OID if found, else NULL. */

  ccp = Curl_getASN1Element(&e, beg, end);
  if(!ccp || e.tag != CURL_ASN1_OBJECT_IDENTIFIER)
    return (const char *) NULL;

  p = OID2str(e.beg, e.end, FALSE);
  if(!p)
    return (const char *) NULL;

  matched = !strcmp(p, oid);
  free((char *) p);
  return matched? ccp: (const char *) NULL;
}

CURLcode Curl_verifyhost(struct connectdata * conn,
                         const char * beg, const char * end)
{
  struct SessionHandle * data = conn->data;
  curl_X509certificate cert;
  curl_asn1Element dn;
  curl_asn1Element elem;
  curl_asn1Element ext;
  curl_asn1Element name;
  const char * p;
  const char * q;
  char * dnsname;
  int matched = -1;
  size_t addrlen = (size_t) -1;
  ssize_t len;
#ifdef ENABLE_IPV6
  struct in6_addr addr;
#else
  struct in_addr addr;
#endif

  /* Verify that connection server matches info in X509 certificate at
     `beg'..`end'. */

  if(!data->set.ssl.verifyhost)
    return CURLE_OK;

  if(!beg)
    return CURLE_PEER_FAILED_VERIFICATION;
  Curl_parseX509(&cert, beg, end);

  /* Get the server IP address. */
#ifdef ENABLE_IPV6
  if(conn->bits.ipv6_ip && Curl_inet_pton(AF_INET6, conn->host.name, &addr))
    addrlen = sizeof(struct in6_addr);
  else
#endif
  if(Curl_inet_pton(AF_INET, conn->host.name, &addr))
    addrlen = sizeof(struct in_addr);

  /* Process extensions. */
  for(p = cert.extensions.beg; p < cert.extensions.end && matched != 1;) {
    p = Curl_getASN1Element(&ext, p, cert.extensions.end);
    /* Check if extension is a subjectAlternativeName. */
    ext.beg = checkOID(ext.beg, ext.end, sanOID);
    if(ext.beg) {
      ext.beg = Curl_getASN1Element(&elem, ext.beg, ext.end);
      /* Skip critical if present. */
      if(elem.tag == CURL_ASN1_BOOLEAN)
        ext.beg = Curl_getASN1Element(&elem, ext.beg, ext.end);
      /* Parse the octet string contents: is a single sequence. */
      Curl_getASN1Element(&elem, elem.beg, elem.end);
      /* Check all GeneralNames. */
      for(q = elem.beg; matched != 1 && q < elem.end;) {
        q = Curl_getASN1Element(&name, q, elem.end);
        switch (name.tag) {
        case 2: /* DNS name. */
          len = utf8asn1str(&dnsname, CURL_ASN1_IA5_STRING,
                            name.beg, name.end);
          if(len > 0 && (size_t)len == strlen(dnsname))
            matched = Curl_cert_hostcheck(dnsname, conn->host.name);
          else
            matched = 0;
          free(dnsname);
          break;

        case 7: /* IP address. */
          matched = (size_t) (name.end - q) == addrlen &&
                    !memcmp(&addr, q, addrlen);
          break;
        }
      }
    }
  }

  switch (matched) {
  case 1:
    /* an alternative name matched the server hostname */
    infof(data, "\t subjectAltName: %s matched\n", conn->host.dispname);
    return CURLE_OK;
  case 0:
    /* an alternative name field existed, but didn't match and then
       we MUST fail */
    infof(data, "\t subjectAltName does not match %s\n", conn->host.dispname);
    return CURLE_PEER_FAILED_VERIFICATION;
  }

  /* Process subject. */
  name.header = NULL;
  name.beg = name.end = "";
  q = cert.subject.beg;
  /* we have to look to the last occurrence of a commonName in the
     distinguished one to get the most significant one. */
  while(q < cert.subject.end) {
    q = Curl_getASN1Element(&dn, q, cert.subject.end);
    for(p = dn.beg; p < dn.end;) {
      p = Curl_getASN1Element(&elem, p, dn.end);
      /* We have a DN's AttributeTypeAndValue: check it in case it's a CN. */
      elem.beg = checkOID(elem.beg, elem.end, cnOID);
      if(elem.beg)
        name = elem;    /* Latch CN. */
    }
  }

  /* Check the CN if found. */
  if(!Curl_getASN1Element(&elem, name.beg, name.end))
    failf(data, "SSL: unable to obtain common name from peer certificate");
  else {
    len = utf8asn1str(&dnsname, elem.tag, elem.beg, elem.end);
    if(len < 0) {
      free(dnsname);
      return CURLE_OUT_OF_MEMORY;
    }
    if(strlen(dnsname) != (size_t) len)         /* Nul byte in string ? */
      failf(data, "SSL: illegal cert name field");
    else if(Curl_cert_hostcheck((const char *) dnsname, conn->host.name)) {
      infof(data, "\t common name: %s (matched)\n", dnsname);
      free(dnsname);
      return CURLE_OK;
    }
    else
      failf(data, "SSL: certificate subject name '%s' does not match "
            "target host name '%s'", dnsname, conn->host.dispname);
    free(dnsname);
  }

  return CURLE_PEER_FAILED_VERIFICATION;
}

#endif /* USE_GSKIT */