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.
181 No SKID extension will be included.
185 The process specified in RFC 5280 section 4.2.1.2. (1) is followed:
186 The keyIdentifier is composed of the 160-bit SHA-1 hash of the value of the BIT
187 STRING subjectPublicKey (excluding the tag, length, and number of unused bits).
189 =item A hex string (possibly with C<:> separating bytes)
191 The provided value is output directly.
192 This choice is strongly discouraged.
196 By default the B<x509>, B<req>, and B<ca> apps behave as if B<hash> was given.
200 subjectKeyIdentifier = hash
202 =head2 Authority Key Identifier
204 The AKID extension specification may have the value B<none>
205 indicating that no AKID shall be included.
206 Otherwise it may have the value B<keyid> or B<issuer>
207 or both of them, separated by C<,>.
208 Either or both can have the option B<always>,
209 indicated by putting a colon C<:> between the value and this option.
210 For self-signed certificates the AKID is suppressed unless B<always> is present.
212 By default the B<x509>, B<req>, and B<ca> apps behave as if B<none> was given
213 for self-signed certificates and B<keyid>C<,> B<issuer> otherwise.
215 If B<keyid> is present, an attempt is made to
216 copy the subject key identifier (SKID) from the issuer certificate except if
217 the issuer certificate is the same as the current one and it is not self-signed.
218 The hash of the public key related to the signing key is taken as fallback
219 if the issuer certificate is the same as the current certificate.
220 If B<always> is present but no value can be obtained, an error is returned.
222 If B<issuer> is present, and in addition it has the option B<always> specified
223 or B<keyid> is not present,
224 then the issuer DN and serial number are copied from the issuer certificate.
225 If this fails, an error is returned.
229 authorityKeyIdentifier = keyid, issuer
231 authorityKeyIdentifier = keyid, issuer:always
233 =head2 Subject Alternative Name
235 This is a multi-valued extension that supports several types of name
236 identifier, including
237 B<email> (an email address),
238 B<URI> (a uniform resource indicator),
239 B<DNS> (a DNS domain name),
240 B<RID> (a registered ID: OBJECT IDENTIFIER),
241 B<IP> (an IP address),
242 B<dirName> (a distinguished name),
244 The syntax of each is described in the following paragraphs.
246 The B<email> option has two special values.
247 C<copy> will automatically include any email addresses
248 contained in the certificate subject name in the extension.
249 C<move> will automatically move any email addresses
250 from the certificate subject name to the extension.
252 The IP address used in the B<IP> option can be in either IPv4 or IPv6 format.
254 The value of B<dirName> is specifies the configuration section containing
255 the distinguished name to use, as a set of name-value pairs.
256 Multi-valued AVAs can be formed by prefacing the name with a B<+> character.
258 The value of B<otherName> can include arbitrary data associated with an OID;
259 the value should be the OID followed by a semicolon and the content in specified
260 using the syntax in L<ASN1_generate_nconf(3)>.
264 subjectAltName = email:copy, email:my@example.com, URI:http://my.example.com/
266 subjectAltName = IP:192.168.7.1
268 subjectAltName = IP:13::17
270 subjectAltName = email:my@example.com, RID:1.2.3.4
272 subjectAltName = otherName:1.2.3.4;UTF8:some other identifier
275 subjectAltName = dirName:dir_sect
283 Non-ASCII Email Address conforming the syntax defined in Section 3.3 of RFC 6531
284 are provided as otherName.SmtpUTF8Mailbox. According to RFC 8398, the email
285 address should be provided as UTF8String. To enforce the valid representation in
286 the certificate, the SmtpUTF8Mailbox should be provided as follows
290 otherName = 1.3.6.1.5.5.7.8.9;FORMAT:UTF8,UTF8String:nonasciiname.example.com
292 =head2 Issuer Alternative Name
294 This extension supports most of the options of subject alternative name;
295 it does not support B<email:copy>.
296 It also adds B<issuer:copy> as an allowed value, which copies any subject
297 alternative names from the issuer certificate, if possible.
301 issuerAltName = issuer:copy
303 =head2 Authority Info Access
305 This extension gives details about how to retrieve information that
306 related to the certificate that the CA makes available. The syntax is
307 B<access_id;location>, where B<access_id> is an object identifier
308 (although only a few values are well-known) and B<location> has the same
309 syntax as subject alternative name (except that B<email:copy> is not supported).
311 Possible values for access_id include B<OCSP> (OCSP responder),
312 B<caIssuers> (CA Issuers),
313 B<ad_timestamping> (AD Time Stamping),
314 B<AD_DVCS> (ad dvcs),
315 B<caRepository> (CA Repository).
319 authorityInfoAccess = OCSP;URI:http://ocsp.example.com/,caIssuers;URI:http://myca.example.com/ca.cer
321 authorityInfoAccess = OCSP;URI:http://ocsp.example.com/
323 =head2 CRL distribution points
325 This is a multi-valued extension whose values can be either a name-value
326 pair using the same form as subject alternative name or a single value
327 specifying the section name containing all the distribution point values.
329 When a name-value pair is used, a DistributionPoint extension will
330 be set with the given value as the fullName field as the distributionPoint
331 value, and the reasons and cRLIssuer fields will be omitted.
333 When a single option is used, the value specifies the section, and that
334 section can have the following items:
340 The full name of the distribution point, in the same format as the subject
345 The value is taken as a distinguished name fragment that is set as the
346 value of the nameRelativeToCRLIssuer field.
350 The value must in the same format as the subject alternative name.
354 A multi-value field that contains the reasons for revocation. The recognized
355 values are: C<keyCompromise>, C<CACompromise>, C<affiliationChanged>,
356 C<superseded>, C<cessationOfOperation>, C<certificateHold>,
357 C<privilegeWithdrawn>, and C<AACompromise>.
361 Only one of B<fullname> or B<relativename> should be specified.
365 crlDistributionPoints = URI:http://example.com/myca.crl
367 crlDistributionPoints = URI:http://example.com/myca.crl, URI:http://example.org/my.crl
369 Full distribution point example:
372 crlDistributionPoints = crldp1_section
375 fullname = URI:http://example.com/myca.crl
376 CRLissuer = dirName:issuer_sect
377 reasons = keyCompromise, CACompromise
384 =head2 Issuing Distribution Point
386 This extension should only appear in CRLs. It is a multi-valued extension
387 whose syntax is similar to the "section" pointed to by the CRL distribution
388 points extension. The following names have meaning:
394 The full name of the distribution point, in the same format as the subject
399 The value is taken as a distinguished name fragment that is set as the
400 value of the nameRelativeToCRLIssuer field.
402 =item onlysomereasons
404 A multi-value field that contains the reasons for revocation. The recognized
405 values are: C<keyCompromise>, C<CACompromise>, C<affiliationChanged>,
406 C<superseded>, C<cessationOfOperation>, C<certificateHold>,
407 C<privilegeWithdrawn>, and C<AACompromise>.
409 =item onlyuser, onlyCA, onlyAA, indirectCRL
411 The value for each of these names is a boolean.
418 issuingDistributionPoint = critical, @idp_section
421 fullname = URI:http://example.com/myca.crl
423 onlysomereasons = keyCompromise, CACompromise
425 =head2 Certificate Policies
427 This is a I<raw> extension that supports all of the defined fields of the
428 certificate extension.
430 Policies without qualifiers are specified by giving the OID.
431 Multiple policies are comma-separated. For example:
433 certificatePolicies = 1.2.4.5, 1.1.3.4
435 To include policy qualifiers, use the "@section" syntax to point to a
436 section that specifies all the information.
438 The section referred to must include the policy OID using the name
439 B<policyIdentifier>. cPSuri qualifiers can be included using the syntax:
443 where C<nnn> is a number.
445 userNotice qualifiers can be set using the syntax:
447 userNotice.nnn = @notice
449 The value of the userNotice qualifier is specified in the relevant section.
450 This section can include B<explicitText>, B<organization>, and B<noticeNumbers>
451 options. explicitText and organization are text strings, noticeNumbers is a
452 comma separated list of numbers. The organization and noticeNumbers options
453 (if included) must BOTH be present. Some software might require
454 the B<ia5org> option at the top level; this changes the encoding from
455 Displaytext to IA5String.
460 certificatePolicies = ia5org, 1.2.3.4, 1.5.6.7.8, @polsect
463 policyIdentifier = 1.3.5.8
464 CPS.1 = "http://my.host.example.com/"
465 CPS.2 = "http://my.your.example.com/"
466 userNotice.1 = @notice
469 explicitText = "Explicit Text Here"
470 organization = "Organisation Name"
471 noticeNumbers = 1, 2, 3, 4
473 The character encoding of explicitText can be specified by prefixing the
474 value with B<UTF8>, B<BMP>, or B<VISIBLE> followed by colon. For example:
477 explicitText = "UTF8:Explicit Text Here"
479 =head2 Policy Constraints
481 This is a multi-valued extension which consisting of the names
482 B<requireExplicitPolicy> or B<inhibitPolicyMapping> and a non negative integer
483 value. At least one component must be present.
487 policyConstraints = requireExplicitPolicy:3
489 =head2 Inhibit Any Policy
491 This is a string extension whose value must be a non negative integer.
497 =head2 Name Constraints
499 This is a multi-valued extension. The name should
500 begin with the word B<permitted> or B<excluded> followed by a B<;>. The rest of
501 the name and the value follows the syntax of subjectAltName except
503 is not supported and the B<IP> form should consist of an IP addresses and
504 subnet mask separated by a B</>.
508 nameConstraints = permitted;IP:192.168.0.0/255.255.0.0
510 nameConstraints = permitted;email:.example.com
512 nameConstraints = excluded;email:.com
516 This is a string extension. It is parsed, but ignored.
522 =head2 TLS Feature (aka Must Staple)
524 This is a multi-valued extension consisting of a list of TLS extension
525 identifiers. Each identifier may be a number (0..65535) or a supported name.
526 When a TLS client sends a listed extension, the TLS server is expected to
527 include that extension in its reply.
529 The supported names are: B<status_request> and B<status_request_v2>.
533 tlsfeature = status_request
535 =head1 DEPRECATED EXTENSIONS
537 The following extensions are non standard, Netscape specific and largely
538 obsolete. Their use in new applications is discouraged.
540 =head2 Netscape String extensions
542 Netscape Comment (B<nsComment>) is a string extension containing a comment
543 which will be displayed when the certificate is viewed in some browsers.
544 Other extensions of this type are: B<nsBaseUrl>,
545 B<nsRevocationUrl>, B<nsCaRevocationUrl>, B<nsRenewalUrl>, B<nsCaPolicyUrl>
546 and B<nsSslServerName>.
548 =head2 Netscape Certificate Type
550 This is a multi-valued extensions which consists of a list of flags to be
551 included. It was used to indicate the purposes for which a certificate could
552 be used. The basicConstraints, keyUsage and extended key usage extensions are
555 Acceptable values for nsCertType are: B<client>, B<server>, B<email>,
556 B<objsign>, B<reserved>, B<sslCA>, B<emailCA>, B<objCA>.
558 =head1 ARBITRARY EXTENSIONS
560 If an extension is not supported by the OpenSSL code then it must be encoded
561 using the arbitrary extension format. It is also possible to use the arbitrary
562 format for supported extensions. Extreme care should be taken to ensure that
563 the data is formatted correctly for the given extension type.
565 There are two ways to encode arbitrary extensions.
567 The first way is to use the word ASN1 followed by the extension content
568 using the same syntax as L<ASN1_generate_nconf(3)>.
572 1.2.3.4 = critical, ASN1:UTF8String:Some random data
573 1.2.3.4.1 = ASN1:SEQUENCE:seq_sect
579 It is also possible to use the word DER to include the raw encoded data in any
582 1.2.3.4 = critical, DER:01:02:03:04
583 1.2.3.4.1 = DER:01020304
585 The value following DER is a hex dump of the DER encoding of the extension
586 Any extension can be placed in this form to override the default behaviour.
589 basicConstraints = critical, DER:00:01:02:03
593 There is no guarantee that a specific implementation will process a given
594 extension. It may therefore be sometimes possible to use certificates for
595 purposes prohibited by their extensions because a specific application does
596 not recognize or honour the values of the relevant extensions.
598 The DER and ASN1 options should be used with caution. It is possible to create
599 invalid extensions if they are not used carefully.
603 L<openssl-req(1)>, L<openssl-ca(1)>, L<openssl-x509(1)>,
604 L<ASN1_generate_nconf(3)>
608 Copyright 2004-2023 The OpenSSL Project Authors. All Rights Reserved.
610 Licensed under the Apache License 2.0 (the "License"). You may not use
611 this file except in compliance with the License. You can obtain a copy
612 in the file LICENSE in the source distribution or at
613 L<https://www.openssl.org/source/license.html>.