5 x509v3_config - X509 V3 certificate extension configuration format
9 Several OpenSSL commands can add extensions to a certificate or
10 certificate request based on the contents of a configuration file
11 and CLI options such as B<-addext>.
12 The syntax of configuration files is described in L<config(5)>.
13 The commands typically have an option to specify the name of the configuration
14 file, and a section within that file; see the documentation of the
15 individual command for details.
17 This page uses B<extensions> as the name of the section, when needed
20 Each entry in the extension section takes the form:
22 name = [critical, ]value(s)
24 If B<critical> is present then the extension will be marked as critical.
26 If multiple entries are processed for the same extension name,
27 later entries override earlier ones with the same name.
29 The format of B<values> depends on the value of B<name>, many have a
30 type-value pairing where the type and value are separated by a colon.
31 There are four main types of extension:
38 Each is described in the following paragraphs.
40 String extensions simply have a string which contains either the value itself
41 or how it is obtained.
43 Multi-valued extensions have a short form and a long form. The short form
44 is a comma-separated list of names and values:
46 basicConstraints = critical, CA:true, pathlen:1
48 The long form allows the values to be placed in a separate section:
51 basicConstraints = critical, @basic_constraints
57 Both forms are equivalent.
59 If an extension is multi-value and a field value must contain a comma the long
60 form must be used otherwise the comma would be misinterpreted as a field
61 separator. For example:
63 subjectAltName = URI:ldap://somehost.com/CN=foo,OU=bar
65 will produce an error but the equivalent form:
68 subjectAltName = @subject_alt_section
71 subjectAltName = URI:ldap://somehost.com/CN=foo,OU=bar
75 OpenSSL does not support multiple occurrences of the same field within a
76 section. In this example:
79 subjectAltName = @alt_section
82 email = steve@example.com
83 email = steve@example.org
85 will only recognize the last value. To specify multiple values append a
86 numeric identifier, as shown here:
89 subjectAltName = @alt_section
92 email.1 = steve@example.com
93 email.2 = steve@example.org
95 The syntax of raw extensions is defined by the source code that parses
96 the extension but should be documented.
97 See L</Certificate Policies> for an example of a raw extension.
99 If an extension type is unsupported, then the I<arbitrary> extension syntax
100 must be used, see the L</ARBITRARY EXTENSIONS> section for more details.
102 =head1 STANDARD EXTENSIONS
104 The following sections describe the syntax of each supported extension.
105 They do not define the semantics of the extension.
107 =head2 Basic Constraints
109 This is a multi-valued extension which indicates whether a certificate is
110 a CA certificate. The first value is B<CA> followed by B<TRUE> or
111 B<FALSE>. If B<CA> is B<TRUE> then an optional B<pathlen> name followed by a
112 nonnegative value can be included.
116 basicConstraints = CA:TRUE
118 basicConstraints = CA:FALSE
120 basicConstraints = critical, CA:TRUE, pathlen:1
122 A CA certificate I<must> include the B<basicConstraints> name with the B<CA>
123 parameter set to B<TRUE>. An end-user certificate must either have B<CA:FALSE>
124 or omit the extension entirely.
125 The B<pathlen> parameter specifies the maximum number of CAs that can appear
126 below this one in a chain. A B<pathlen> of zero means the CA cannot sign
127 any sub-CA's, and can only sign end-entity certificates.
131 Key usage is a multi-valued extension consisting of a list of names of
132 the permitted key usages. The defined values are: C<digitalSignature>,
133 C<nonRepudiation>, C<keyEncipherment>, C<dataEncipherment>, C<keyAgreement>,
134 C<keyCertSign>, C<cRLSign>, C<encipherOnly>, and C<decipherOnly>.
138 keyUsage = digitalSignature, nonRepudiation
140 keyUsage = critical, keyCertSign
142 =head2 Extended Key Usage
144 This extension consists of a list of values indicating purposes for which
145 the certificate public key can be used.
146 Each value can be either a short text name or an OID.
147 The following text names, and their intended meaning, are known:
149 Value Meaning according to RFC 5280 etc.
150 ----- ----------------------------------
151 serverAuth SSL/TLS WWW Server Authentication
152 clientAuth SSL/TLS WWW Client Authentication
153 codeSigning Code Signing
154 emailProtection E-mail Protection (S/MIME)
155 timeStamping Trusted Timestamping
156 OCSPSigning OCSP Signing
157 ipsecIKE ipsec Internet Key Exchange
158 msCodeInd Microsoft Individual Code Signing (authenticode)
159 msCodeCom Microsoft Commercial Code Signing (authenticode)
160 msCTLSign Microsoft Trust List Signing
161 msEFS Microsoft Encrypted File System
163 While IETF RFC 5280 says that B<id-kp-serverAuth> and B<id-kp-clientAuth>
164 are only for WWW use, in practice they are used for all kinds of TLS clients
165 and servers, and this is what OpenSSL assumes as well.
169 extendedKeyUsage = critical, codeSigning, 1.2.3.4
171 extendedKeyUsage = serverAuth, clientAuth
173 =head2 Subject Key Identifier
175 The SKID extension specification has a value with three choices.
176 If the value is the word B<none> then no SKID extension will be included.
177 If the value is the word B<hash>, or by default for the B<x509>, B<req>, and
178 B<ca> apps, the process specified in RFC 5280 section 4.2.1.2. (1) is followed:
179 The keyIdentifier is composed of the 160-bit SHA-1 hash of the value of the BIT
180 STRING subjectPublicKey (excluding the tag, length, and number of unused bits).
182 Otherwise, the value must be a hex string (possibly with C<:> separating bytes)
183 to output directly, however, this is strongly discouraged.
187 subjectKeyIdentifier = hash
189 =head2 Authority Key Identifier
191 The AKID extension specification may have the value B<none>
192 indicating that no AKID shall be included.
193 Otherwise it may have the value B<keyid> or B<issuer>
194 or both of them, separated by C<,>.
195 Either or both can have the option B<always>,
196 indicated by putting a colon C<:> between the value and this option.
197 For self-signed certificates the AKID is suppressed unless B<always> is present.
198 By default the B<x509>, B<req>, and B<ca> apps behave as if
199 "none" was given for self-signed certificates and "keyid, issuer" otherwise.
201 If B<keyid> is present, an attempt is made to
202 copy the subject key identifier (SKID) from the issuer certificate except if
203 the issuer certificate is the same as the current one and it is not self-signed.
204 The hash of the public key related to the signing key is taken as fallback
205 if the issuer certificate is the same as the current certificate.
206 If B<always> is present but no value can be obtained, an error is returned.
208 If B<issuer> is present, and in addition it has the option B<always> specified
209 or B<keyid> is not present,
210 then the issuer DN and serial number are copied from the issuer certificate.
214 authorityKeyIdentifier = keyid, issuer
216 authorityKeyIdentifier = keyid, issuer:always
218 =head2 Subject Alternative Name
220 This is a multi-valued extension that supports several types of name
221 identifier, including
222 B<email> (an email address),
223 B<URI> (a uniform resource indicator),
224 B<DNS> (a DNS domain name),
225 B<RID> (a registered ID: OBJECT IDENTIFIER),
226 B<IP> (an IP address),
227 B<dirName> (a distinguished name),
229 The syntax of each is described in the following paragraphs.
231 The B<email> option has two special values.
232 C<copy> will automatically include any email addresses
233 contained in the certificate subject name in the extension.
234 C<move> will automatically move any email addresses
235 from the certificate subject name to the extension.
237 The IP address used in the B<IP> option can be in either IPv4 or IPv6 format.
239 The value of B<dirName> is specifies the configuration section containing
240 the distinguished name to use, as a set of name-value pairs.
241 Multi-valued AVAs can be formed by prefacing the name with a B<+> character.
243 The value of B<otherName> can include arbitrary data associated with an OID;
244 the value should be the OID followed by a semicolon and the content in specified
245 using the syntax in L<ASN1_generate_nconf(3)>.
249 subjectAltName = email:copy, email:my@example.com, URI:http://my.example.com/
251 subjectAltName = IP:192.168.7.1
253 subjectAltName = IP:13::17
255 subjectAltName = email:my@example.com, RID:1.2.3.4
257 subjectAltName = otherName:1.2.3.4;UTF8:some other identifier
260 subjectAltName = dirName:dir_sect
268 Non-ASCII Email Address conforming the syntax defined in Section 3.3 of RFC 6531
269 are provided as otherName.SmtpUTF8Mailbox. According to RFC 8398, the email
270 address should be provided as UTF8String. To enforce the valid representation in
271 the certificate, the SmtpUTF8Mailbox should be provided as follows
275 otherName = 1.3.6.1.5.5.7.8.9;FORMAT:UTF8,UTF8String:nonasciiname.example.com
277 =head2 Issuer Alternative Name
279 This extension supports most of the options of subject alternative name;
280 it does not support B<email:copy>.
281 It also adds B<issuer:copy> as an allowed value, which copies any subject
282 alternative names from the issuer certificate, if possible.
286 issuerAltName = issuer:copy
288 =head2 Authority Info Access
290 This extension gives details about how to retrieve information that
291 related to the certificate that the CA makes available. The syntax is
292 B<access_id;location>, where B<access_id> is an object identifier
293 (although only a few values are well-known) and B<location> has the same
294 syntax as subject alternative name (except that B<email:copy> is not supported).
296 Possible values for access_id include B<OCSP> (OCSP responder),
297 B<caIssuers> (CA Issuers),
298 B<ad_timestamping> (AD Time Stamping),
299 B<AD_DVCS> (ad dvcs),
300 B<caRepository> (CA Repository).
304 authorityInfoAccess = OCSP;URI:http://ocsp.example.com/,caIssuers;URI:http://myca.example.com/ca.cer
306 authorityInfoAccess = OCSP;URI:http://ocsp.example.com/
308 =head2 CRL distribution points
310 This is a multi-valued extension whose values can be either a name-value
311 pair using the same form as subject alternative name or a single value
312 specifying the section name containing all the distribution point values.
314 When a name-value pair is used, a DistributionPoint extension will
315 be set with the given value as the fullName field as the distributionPoint
316 value, and the reasons and cRLIssuer fields will be omitted.
318 When a single option is used, the value specifies the section, and that
319 section can have the following items:
325 The full name of the distribution point, in the same format as the subject
330 The value is taken as a distinguished name fragment that is set as the
331 value of the nameRelativeToCRLIssuer field.
335 The value must in the same format as the subject alternative name.
339 A multi-value field that contains the reasons for revocation. The recognized
340 values are: C<keyCompromise>, C<CACompromise>, C<affiliationChanged>,
341 C<superseded>, C<cessationOfOperation>, C<certificateHold>,
342 C<privilegeWithdrawn>, and C<AACompromise>.
346 Only one of B<fullname> or B<relativename> should be specified.
350 crlDistributionPoints = URI:http://example.com/myca.crl
352 crlDistributionPoints = URI:http://example.com/myca.crl, URI:http://example.org/my.crl
354 Full distribution point example:
357 crlDistributionPoints = crldp1_section
360 fullname = URI:http://example.com/myca.crl
361 CRLissuer = dirName:issuer_sect
362 reasons = keyCompromise, CACompromise
369 =head2 Issuing Distribution Point
371 This extension should only appear in CRLs. It is a multi-valued extension
372 whose syntax is similar to the "section" pointed to by the CRL distribution
373 points extension. The following names have meaning:
379 The full name of the distribution point, in the same format as the subject
384 The value is taken as a distinguished name fragment that is set as the
385 value of the nameRelativeToCRLIssuer field.
387 =item onlysomereasons
389 A multi-value field that contains the reasons for revocation. The recognized
390 values are: C<keyCompromise>, C<CACompromise>, C<affiliationChanged>,
391 C<superseded>, C<cessationOfOperation>, C<certificateHold>,
392 C<privilegeWithdrawn>, and C<AACompromise>.
394 =item onlyuser, onlyCA, onlyAA, indirectCRL
396 The value for each of these names is a boolean.
403 issuingDistributionPoint = critical, @idp_section
406 fullname = URI:http://example.com/myca.crl
408 onlysomereasons = keyCompromise, CACompromise
410 =head2 Certificate Policies
412 This is a I<raw> extension that supports all of the defined fields of the
413 certificate extension.
415 Policies without qualifiers are specified by giving the OID.
416 Multiple policies are comma-separated. For example:
418 certificatePolicies = 1.2.4.5, 1.1.3.4
420 To include policy qualifiers, use the "@section" syntax to point to a
421 section that specifies all the information.
423 The section referred to must include the policy OID using the name
424 B<policyIdentifier>. cPSuri qualifiers can be included using the syntax:
428 where C<nnn> is a number.
430 userNotice qualifiers can be set using the syntax:
432 userNotice.nnn = @notice
434 The value of the userNotice qualifier is specified in the relevant section.
435 This section can include B<explicitText>, B<organization>, and B<noticeNumbers>
436 options. explicitText and organization are text strings, noticeNumbers is a
437 comma separated list of numbers. The organization and noticeNumbers options
438 (if included) must BOTH be present. Some software might require
439 the B<ia5org> option at the top level; this changes the encoding from
440 Displaytext to IA5String.
445 certificatePolicies = ia5org, 1.2.3.4, 1.5.6.7.8, @polsect
448 policyIdentifier = 1.3.5.8
449 CPS.1 = "http://my.host.example.com/"
450 CPS.2 = "http://my.your.example.com/"
451 userNotice.1 = @notice
454 explicitText = "Explicit Text Here"
455 organization = "Organisation Name"
456 noticeNumbers = 1, 2, 3, 4
458 The character encoding of explicitText can be specified by prefixing the
459 value with B<UTF8>, B<BMP>, or B<VISIBLE> followed by colon. For example:
462 explicitText = "UTF8:Explicit Text Here"
464 =head2 Policy Constraints
466 This is a multi-valued extension which consisting of the names
467 B<requireExplicitPolicy> or B<inhibitPolicyMapping> and a non negative integer
468 value. At least one component must be present.
472 policyConstraints = requireExplicitPolicy:3
474 =head2 Inhibit Any Policy
476 This is a string extension whose value must be a non negative integer.
482 =head2 Name Constraints
484 This is a multi-valued extension. The name should
485 begin with the word B<permitted> or B<excluded> followed by a B<;>. The rest of
486 the name and the value follows the syntax of subjectAltName except
488 is not supported and the B<IP> form should consist of an IP addresses and
489 subnet mask separated by a B</>.
493 nameConstraints = permitted;IP:192.168.0.0/255.255.0.0
495 nameConstraints = permitted;email:.example.com
497 nameConstraints = excluded;email:.com
501 This is a string extension. It is parsed, but ignored.
507 =head2 TLS Feature (aka Must Staple)
509 This is a multi-valued extension consisting of a list of TLS extension
510 identifiers. Each identifier may be a number (0..65535) or a supported name.
511 When a TLS client sends a listed extension, the TLS server is expected to
512 include that extension in its reply.
514 The supported names are: B<status_request> and B<status_request_v2>.
518 tlsfeature = status_request
520 =head1 DEPRECATED EXTENSIONS
522 The following extensions are non standard, Netscape specific and largely
523 obsolete. Their use in new applications is discouraged.
525 =head2 Netscape String extensions
527 Netscape Comment (B<nsComment>) is a string extension containing a comment
528 which will be displayed when the certificate is viewed in some browsers.
529 Other extensions of this type are: B<nsBaseUrl>,
530 B<nsRevocationUrl>, B<nsCaRevocationUrl>, B<nsRenewalUrl>, B<nsCaPolicyUrl>
531 and B<nsSslServerName>.
533 =head2 Netscape Certificate Type
535 This is a multi-valued extensions which consists of a list of flags to be
536 included. It was used to indicate the purposes for which a certificate could
537 be used. The basicConstraints, keyUsage and extended key usage extensions are
540 Acceptable values for nsCertType are: B<client>, B<server>, B<email>,
541 B<objsign>, B<reserved>, B<sslCA>, B<emailCA>, B<objCA>.
543 =head1 ARBITRARY EXTENSIONS
545 If an extension is not supported by the OpenSSL code then it must be encoded
546 using the arbitrary extension format. It is also possible to use the arbitrary
547 format for supported extensions. Extreme care should be taken to ensure that
548 the data is formatted correctly for the given extension type.
550 There are two ways to encode arbitrary extensions.
552 The first way is to use the word ASN1 followed by the extension content
553 using the same syntax as L<ASN1_generate_nconf(3)>.
557 1.2.3.4 = critical, ASN1:UTF8String:Some random data
558 1.2.3.4.1 = ASN1:SEQUENCE:seq_sect
564 It is also possible to use the word DER to include the raw encoded data in any
567 1.2.3.4 = critical, DER:01:02:03:04
568 1.2.3.4.1 = DER:01020304
570 The value following DER is a hex dump of the DER encoding of the extension
571 Any extension can be placed in this form to override the default behaviour.
574 basicConstraints = critical, DER:00:01:02:03
578 There is no guarantee that a specific implementation will process a given
579 extension. It may therefore be sometimes possible to use certificates for
580 purposes prohibited by their extensions because a specific application does
581 not recognize or honour the values of the relevant extensions.
583 The DER and ASN1 options should be used with caution. It is possible to create
584 invalid extensions if they are not used carefully.
588 L<openssl-req(1)>, L<openssl-ca(1)>, L<openssl-x509(1)>,
589 L<ASN1_generate_nconf(3)>
593 Copyright 2004-2021 The OpenSSL Project Authors. All Rights Reserved.
595 Licensed under the Apache License 2.0 (the "License"). You may not use
596 this file except in compliance with the License. You can obtain a copy
597 in the file LICENSE in the source distribution or at
598 L<https://www.openssl.org/source/license.html>.