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
|
This is some preliminary documentation for OpenSSL.
Contents:
OpenSSL X509V3 extension configuration
X509V3 Extension code: programmers guide
PKCS#12 Library
==============================================================================
OpenSSL X509V3 extension configuration
==============================================================================
OpenSSL X509V3 extension configuration: preliminary documentation.
INTRODUCTION.
For OpenSSL 0.9.2 the extension code has be considerably enhanced. It is now
possible to add and print out common X509 V3 certificate and CRL extensions.
BEGINNERS NOTE
For most simple applications you don't need to know too much about extensions:
the default openssl.cnf values will usually do sensible things.
If you want to know more you can initially quickly look through the sections
describing how the standard OpenSSL utilities display and add extensions and
then the list of supported extensions.
For more technical information about the meaning of extensions see:
http://www.imc.org/ietf-pkix/
http://home.netscape.com/eng/security/certs.html
PRINTING EXTENSIONS.
Extension values are automatically printed out for supported extensions.
openssl x509 -in cert.pem -text
openssl crl -in crl.pem -text
will give information in the extension printout, for example:
X509v3 extensions:
X509v3 Basic Constraints:
CA:TRUE
X509v3 Subject Key Identifier:
73:FE:F7:59:A7:E1:26:84:44:D6:44:36:EE:79:1A:95:7C:B1:4B:15
X509v3 Authority Key Identifier:
keyid:73:FE:F7:59:A7:E1:26:84:44:D6:44:36:EE:79:1A:95:7C:B1:4B:15, DirName:/C=AU/ST=Some-State/O=Internet Widgits Pty Ltd/Email=email@1.address/Email=email@2.address, serial:00
X509v3 Key Usage:
Certificate Sign, CRL Sign
X509v3 Subject Alternative Name:
email:email@1.address, email:email@2.address
CONFIGURATION FILES.
The OpenSSL utilities 'ca' and 'req' can now have extension sections listing
which certificate extensions to include. In each case a line:
x509_extensions = extension_section
indicates which section contains the extensions. In the case of 'req' the
extension section is used when the -x509 option is present to create a
self signed root certificate.
The 'x509' utility also supports extensions when it signs a certificate.
The -extfile option is used to set the configuration file containing the
extensions. In this case a line with:
extensions = extension_section
in the nameless (default) section is used. If no such line is included then
it uses the default section.
You can also add extensions to CRLs: a line
crl_extensions = crl_extension_section
will include extensions when the -gencrl option is used with the 'ca' utility.
You can add any extension to a CRL but of the supported extensions only
issuerAltName and authorityKeyIdentifier make any real sense. Note: these are
CRL extensions NOT CRL *entry* extensions which cannot currently be generated.
CRL entry extensions can be displayed.
NB. At this time Netscape Communicator rejects V2 CRLs: to get an old V1 CRL
you should not include a crl_extensions line in the configuration file.
As with all configuration files you can use the inbuilt environment expansion
to allow the values to be passed in the environment. Therefore if you have
several extension sections used for different purposes you can have a line:
x509_extensions = $ENV::ENV_EXT
and set the ENV_EXT environment variable before calling the relevant utility.
EXTENSION SYNTAX.
Extensions have the basic form:
extension_name=[critical,] extension_options
the use of the critical option makes the extension critical. Extreme caution
should be made when using the critical flag. If an extension is marked
as critical then any client that does not understand the extension should
reject it as invalid. Some broken software will reject certificates which
have *any* critical extensions (these violates PKIX but we have to live
with it).
There are three main types of extension: string extensions, multi-valued
extensions, and raw extensions.
String extensions simply have a string which contains either the value itself
or how it is obtained.
For example:
nsComment="This is a Comment"
Multi-valued extensions have a short form and a long form. The short form
is a list of names and values:
basicConstraints=critical,CA:true,pathlen:1
The long form allows the values to be placed in a separate section:
basicConstraints=critical,@bs_section
[bs_section]
CA=true
pathlen=1
Both forms are equivalent. However it should be noted that in some cases the
same name can appear multiple times, for example,
subjectAltName=email:steve@here,email:steve@there
in this case an equivalent long form is:
subjectAltName=@alt_section
[alt_section]
email.1=steve@here
email.2=steve@there
This is because the configuration file code cannot handle the same name
occurring twice in the same section.
The syntax of raw extensions is governed by the extension code: it can
for example contain data in multiple sections. The correct syntax to
use is defined by the extension code itself: check out the certificate
policies extension for an example.
There are two ways to encode arbitrary extensions.
The first way is to use the word ASN1 followed by the extension content
using the same syntax as ASN1_generate_nconf(). For example:
1.2.3.4=critical,ASN1:UTF8String:Some random data
1.2.3.4=ASN1:SEQUENCE:seq_sect
[seq_sect]
field1 = UTF8:field1
field2 = UTF8:field2
It is also possible to use the word DER to include arbitrary data in any
extension.
1.2.3.4=critical,DER:01:02:03:04
1.2.3.4=DER:01020304
The value following DER is a hex dump of the DER encoding of the extension
Any extension can be placed in this form to override the default behaviour.
For example:
basicConstraints=critical,DER:00:01:02:03
WARNING: DER should be used with caution. It is possible to create totally
invalid extensions unless care is taken.
CURRENTLY SUPPORTED EXTENSIONS.
If you aren't sure about extensions then they can be largely ignored: its only
when you want to do things like restrict certificate usage when you need to
worry about them.
The only extension that a beginner might want to look at is Basic Constraints.
If in addition you want to try Netscape object signing the you should also
look at Netscape Certificate Type.
Literal String extensions.
In each case the 'value' of the extension is placed directly in the
extension. Currently supported extensions in this category are: nsBaseUrl,
nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl,
nsSslServerName and nsComment.
For example:
nsComment="This is a test comment"
Bit Strings.
Bit string extensions just consist of a list of supported bits, currently
two extensions are in this category: PKIX keyUsage and the Netscape specific
nsCertType.
nsCertType (netscape certificate type) takes the flags: client, server, email,
objsign, reserved, sslCA, emailCA, objCA.
keyUsage (PKIX key usage) takes the flags: digitalSignature, nonRepudiation,
keyEncipherment, dataEncipherment, keyAgreement, keyCertSign, cRLSign,
encipherOnly, decipherOnly.
For example:
nsCertType=server
keyUsage=digitalSignature, nonRepudiation
Hints on Netscape Certificate Type.
Other than Basic Constraints this is the only extension a beginner might
want to use, if you want to try Netscape object signing, otherwise it can
be ignored.
If you want a certificate that can be used just for object signing then:
nsCertType=objsign
will do the job. If you want to use it as a normal end user and server
certificate as well then
nsCertType=objsign,email,server
is more appropriate. You cannot use a self signed certificate for object
signing (well Netscape signtool can but it cheats!) so you need to create
a CA certificate and sign an end user certificate with it.
Side note: If you want to conform to the Netscape specifications then you
should really also set:
nsCertType=objCA
in the *CA* certificate for just an object signing CA and
nsCertType=objCA,emailCA,sslCA
for everything. Current Netscape software doesn't enforce this so it can
be omitted.
Basic Constraints.
This is generally the only extension you need to worry about for simple
applications. If you want your certificate to be usable as a CA certificate
(in addition to an end user certificate) then you set this to:
basicConstraints=CA:TRUE
if you want to be certain the certificate cannot be used as a CA then do:
basicConstraints=CA:FALSE
The rest of this section describes more advanced usage.
Basic constraints is a multi-valued extension that supports a CA and an
optional pathlen option. The CA option takes the values true and false and
pathlen takes an integer. Note if the CA option is false the pathlen option
should be omitted.
The pathlen parameter indicates the maximum number of CAs that can appear
below this one in a chain. So if you have a CA with a pathlen of zero it can
only be used to sign end user certificates and not further CAs. This all
assumes that the software correctly interprets this extension of course.
Examples:
basicConstraints=CA:TRUE
basicConstraints=critical,CA:TRUE, pathlen:0
NOTE: for a CA to be considered valid it must have the CA option set to
TRUE. An end user certificate MUST NOT have the CA value set to true.
According to PKIX recommendations it should exclude the extension entirely,
however some software may require CA set to FALSE for end entity certificates.
Extended Key Usage.
This extensions consists of a list of usages.
These can either be object short names of the dotted numerical form of OIDs.
While any OID can be used only certain values make sense. In particular the
following PKIX, NS and MS values are meaningful:
Value Meaning
----- -------
serverAuth SSL/TLS Web Server Authentication.
clientAuth SSL/TLS Web Client Authentication.
codeSigning Code signing.
emailProtection E-mail Protection (S/MIME).
timeStamping Trusted Timestamping
msCodeInd Microsoft Individual Code Signing (authenticode)
msCodeCom Microsoft Commercial Code Signing (authenticode)
msCTLSign Microsoft Trust List Signing
msSGC Microsoft Server Gated Crypto
msEFS Microsoft Encrypted File System
nsSGC Netscape Server Gated Crypto
For example, under IE5 a CA can be used for any purpose: by including a list
of the above usages the CA can be restricted to only authorised uses.
Note: software packages may place additional interpretations on certificate
use, in particular some usages may only work for selected CAs. Don't for example
expect just including msSGC or nsSGC will automatically mean that a certificate
can be used for SGC ("step up" encryption) otherwise anyone could use it.
Examples:
extendedKeyUsage=critical,codeSigning,1.2.3.4
extendedKeyUsage=nsSGC,msSGC
Subject Key Identifier.
This is really a string extension and can take two possible values. Either
a hex string giving details of the extension value to include or the word
'hash' which then automatically follow PKIX guidelines in selecting and
appropriate key identifier. The use of the hex string is strongly discouraged.
Example: subjectKeyIdentifier=hash
Authority Key Identifier.
The authority key identifier extension permits two options. keyid and issuer:
both can take the optional value "always".
If the keyid option is present an attempt is made to copy the subject key
identifier from the parent certificate. If the value "always" is present
then an e
|