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X509V3_CONFIG(5)                    OpenSSL                   X509V3_CONFIG(5)

       x509v3_config - X509 V3 certificate extension configuration format

       Several OpenSSL commands can add extensions to a certificate or
       certificate request based on the contents of a configuration file and
       CLI options such as -addext.  The syntax of configuration files is
       described in config(5).  The commands typically have an option to
       specify the name of the configuration file, and a section within that
       file; see the documentation of the individual command for details.

       This page uses extensions as the name of the section, when needed in

       Each entry in the extension section takes the form:

        name = [critical, ]value(s)

       If critical is present then the extension will be marked as critical.

       If multiple entries are processed for the same extension name, later
       entries override earlier ones with the same name.

       The format of values depends on the value of name, many have a type-
       value pairing where the type and value are separated by a colon.  There
       are four main types of extension:


       Each is described in the following paragraphs.

       String extensions simply have a string which contains either the value
       itself or how it is obtained.

       Multi-valued extensions have a short form and a long form. The short
       form is a comma-separated 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, @basic_constraints

        CA = true
        pathlen = 1

       Both forms are equivalent.

       If an extension is multi-value and a field value must contain a comma
       the long form must be used otherwise the comma would be misinterpreted
       as a field separator. For example:

        subjectAltName = URI:ldap://somehost.com/CN=foo,OU=bar

       will produce an error but the equivalent form:

        subjectAltName = @subject_alt_section

        subjectAltName = URI:ldap://somehost.com/CN=foo,OU=bar

       is valid.

       OpenSSL does not support multiple occurrences of the same field within
       a section. In this example:

        subjectAltName = @alt_section

        email = steve@example.com
        email = steve@example.org

       will only recognize the last value.  To specify multiple values append
       a numeric identifier, as shown here:

        subjectAltName = @alt_section

        email.1 = steve@example.com
        email.2 = steve@example.org

       The syntax of raw extensions is defined by the source code that parses
       the extension but should be documented.  See "Certificate Policies" for
       an example of a raw extension.

       If an extension type is unsupported, then the arbitrary extension
       syntax must be used, see the "ARBITRARY EXTENSIONS" section for more

       The following sections describe the syntax of each supported extension.
       They do not define the semantics of the extension.

   Basic Constraints
       This is a multi-valued extension which indicates whether a certificate
       is a CA certificate. The first value is CA followed by TRUE or FALSE.
       If CA is TRUE then an optional pathlen name followed by a nonnegative
       value can be included.

       For example:

        basicConstraints = CA:TRUE

        basicConstraints = CA:FALSE

        basicConstraints = critical, CA:TRUE, pathlen:1

       A CA certificate must include the basicConstraints name with the CA
       parameter set to TRUE. An end-user certificate must either have
       CA:FALSE or omit the extension entirely.  The pathlen parameter
       specifies the maximum number of CAs that can appear below this one in a
       chain. A pathlen of zero means the CA cannot sign any sub-CA's, and can
       only sign end-entity certificates.

   Key Usage
       Key usage is a multi-valued extension consisting of a list of names of
       the permitted key usages.  The defined values are: "digitalSignature",
       "nonRepudiation", "keyEncipherment", "dataEncipherment",
       "keyAgreement", "keyCertSign", "cRLSign", "encipherOnly", and


        keyUsage = digitalSignature, nonRepudiation

        keyUsage = critical, keyCertSign

   Extended Key Usage
       This extension consists of a list of values indicating purposes for
       which the certificate public key can be used.  Each value can be either
       a short text name or an OID. The following text names, and their
       intended meaning, are known:

        Value                  Meaning according to RFC 5280 etc.
        -----                  ----------------------------------
        serverAuth             SSL/TLS WWW Server Authentication
        clientAuth             SSL/TLS WWW Client Authentication
        codeSigning            Code Signing
        emailProtection        E-mail Protection (S/MIME)
        timeStamping           Trusted Timestamping
        OCSPSigning            OCSP Signing
        ipsecIKE               ipsec Internet Key Exchange
        msCodeInd              Microsoft Individual Code Signing (authenticode)
        msCodeCom              Microsoft Commercial Code Signing (authenticode)
        msCTLSign              Microsoft Trust List Signing
        msEFS                  Microsoft Encrypted File System

       While IETF RFC 5280 says that id-kp-serverAuth and id-kp-clientAuth are
       only for WWW use, in practice they are used for all kinds of TLS
       clients and servers, and this is what OpenSSL assumes as well.


        extendedKeyUsage = critical, codeSigning,

        extendedKeyUsage = serverAuth, clientAuth

   Subject Key Identifier
       The SKID extension specification has a value with three choices.  If
       the value is the word none then no SKID extension will be included.  If
       the value is the word hash, or by default for the x509, req, and ca
       apps, the process specified in RFC 5280 section (1) is
       followed: The keyIdentifier is composed of the 160-bit SHA-1 hash of
       the value of the BIT STRING subjectPublicKey (excluding the tag,
       length, and number of unused bits).

       Otherwise, the value must be a hex string (possibly with ":" separating
       bytes) to output directly, however, this is strongly discouraged.


        subjectKeyIdentifier = hash

   Authority Key Identifier
       The AKID extension specification may have the value none indicating
       that no AKID shall be included.  Otherwise it may have the value keyid
       or issuer or both of them, separated by ",".  Either or both can have
       the option always, indicated by putting a colon ":" between the value
       and this option.  For self-signed certificates the AKID is suppressed
       unless always is present.  By default the x509, req, and ca apps behave
       as if "none" was given for self-signed certificates and "keyid, issuer"

       If keyid is present, an attempt is made to copy the subject key
       identifier (SKID) from the issuer certificate except if the issuer
       certificate is the same as the current one and it is not self-signed.
       The hash of the public key related to the signing key is taken as
       fallback if the issuer certificate is the same as the current
       certificate.  If always is present but no value can be obtained, an
       error is returned.

       If issuer is present, and in addition it has the option always
       specified or keyid is not present, then the issuer DN and serial number
       are copied from the issuer certificate.


        authorityKeyIdentifier = keyid, issuer

        authorityKeyIdentifier = keyid, issuer:always

   Subject Alternative Name
       This is a multi-valued extension that supports several types of name
       identifier, including email (an email address), URI (a uniform resource
       indicator), DNS (a DNS domain name), RID (a registered ID: OBJECT
       IDENTIFIER), IP (an IP address), dirName (a distinguished name), and
       otherName.  The syntax of each is described in the following

       The email option has two special values.  "copy" will automatically
       include any email addresses contained in the certificate subject name
       in the extension.  "move" will automatically move any email addresses
       from the certificate subject name to the extension.

       The IP address used in the IP option can be in either IPv4 or IPv6

       The value of dirName is specifies the configuration section containing
       the distinguished name to use, as a set of name-value pairs.  Multi-
       valued AVAs can be formed by prefacing the name with a + character.

       The value of otherName can include arbitrary data associated with an
       OID; the value should be the OID followed by a semicolon and the
       content in specified using the syntax in ASN1_generate_nconf(3).


        subjectAltName = email:copy, email:my@example.com, URI:http://my.example.com/

        subjectAltName = IP:

        subjectAltName = IP:13::17

        subjectAltName = email:my@example.com, RID:

        subjectAltName = otherName:;UTF8:some other identifier

        subjectAltName = dirName:dir_sect

        C = UK
        O = My Organization
        OU = My Unit
        CN = My Name

       Non-ASCII Email Address conforming the syntax defined in Section 3.3 of
       RFC 6531 are provided as otherName.SmtpUTF8Mailbox. According to RFC
       8398, the email address should be provided as UTF8String. To enforce
       the valid representation in the certificate, the SmtpUTF8Mailbox should
       be provided as follows

        otherName =;FORMAT:UTF8,UTF8String:nonasciiname.example.com

   Issuer Alternative Name
       This extension supports most of the options of subject alternative
       name; it does not support email:copy.  It also adds issuer:copy as an
       allowed value, which copies any subject alternative names from the
       issuer certificate, if possible.


        issuerAltName = issuer:copy

   Authority Info Access
       This extension gives details about how to retrieve information that
       related to the certificate that the CA makes available. The syntax is
       access_id;location, where access_id is an object identifier (although
       only a few values are well-known) and location has the same syntax as
       subject alternative name (except that email:copy is not supported).

       Possible values for access_id include OCSP (OCSP responder), caIssuers
       (CA Issuers), ad_timestamping (AD Time Stamping), AD_DVCS (ad dvcs),
       caRepository (CA Repository).


        authorityInfoAccess = OCSP;URI:http://ocsp.example.com/,caIssuers;URI:http://myca.example.com/ca.cer

        authorityInfoAccess = OCSP;URI:http://ocsp.example.com/

   CRL distribution points
       This is a multi-valued extension whose values can be either a name-
       value pair using the same form as subject alternative name or a single
       value specifying the section name containing all the distribution point

       When a name-value pair is used, a DistributionPoint extension will be
       set with the given value as the fullName field as the distributionPoint
       value, and the reasons and cRLIssuer fields will be omitted.

       When a single option is used, the value specifies the section, and that
       section can have the following items:

           The full name of the distribution point, in the same format as the
           subject alternative name.

           The value is taken as a distinguished name fragment that is set as
           the value of the nameRelativeToCRLIssuer field.

           The value must in the same format as the subject alternative name.

           A multi-value field that contains the reasons for revocation. The
           recognized values are: "keyCompromise", "CACompromise",
           "affiliationChanged", "superseded", "cessationOfOperation",
           "certificateHold", "privilegeWithdrawn", and "AACompromise".

       Only one of fullname or relativename should be specified.

       Simple examples:

        crlDistributionPoints = URI:http://example.com/myca.crl

        crlDistributionPoints = URI:http://example.com/myca.crl, URI:http://example.org/my.crl

       Full distribution point example:

        crlDistributionPoints = crldp1_section

        fullname = URI:http://example.com/myca.crl
        CRLissuer = dirName:issuer_sect
        reasons = keyCompromise, CACompromise

        C = UK
        O = Organisation
        CN = Some Name

   Issuing Distribution Point
       This extension should only appear in CRLs. It is a multi-valued
       extension whose syntax is similar to the "section" pointed to by the
       CRL distribution points extension. The following names have meaning:

           The full name of the distribution point, in the same format as the
           subject alternative name.

           The value is taken as a distinguished name fragment that is set as
           the value of the nameRelativeToCRLIssuer field.

           A multi-value field that contains the reasons for revocation. The
           recognized values are: "keyCompromise", "CACompromise",
           "affiliationChanged", "superseded", "cessationOfOperation",
           "certificateHold", "privilegeWithdrawn", and "AACompromise".

       onlyuser, onlyCA, onlyAA, indirectCRL
           The value for each of these names is a boolean.


        issuingDistributionPoint = critical, @idp_section

        fullname = URI:http://example.com/myca.crl
        indirectCRL = TRUE
        onlysomereasons = keyCompromise, CACompromise

   Certificate Policies
       This is a raw extension that supports all of the defined fields of the
       certificate extension.

       Policies without qualifiers are specified by giving the OID. Multiple
       policies are comma-separated. For example:

        certificatePolicies =,

       To include policy qualifiers, use the "@section" syntax to point to a
       section that specifies all the information.

       The section referred to must include the policy OID using the name
       policyIdentifier. cPSuri qualifiers can be included using the syntax:

        CPS.nnn = value

       where "nnn" is a number.

       userNotice qualifiers can be set using the syntax:

        userNotice.nnn = @notice

       The value of the userNotice qualifier is specified in the relevant
       section.  This section can include explicitText, organization, and
       noticeNumbers options. explicitText and organization are text strings,
       noticeNumbers is a comma separated list of numbers. The organization
       and noticeNumbers options (if included) must BOTH be present. Some
       software might require the ia5org option at the top level; this changes
       the encoding from Displaytext to IA5String.


        certificatePolicies = ia5org,,, @polsect

        policyIdentifier =
        CPS.1 = "http://my.host.example.com/"
        CPS.2 = "http://my.your.example.com/"
        userNotice.1 = @notice

        explicitText = "Explicit Text Here"
        organization = "Organisation Name"
        noticeNumbers = 1, 2, 3, 4

       The character encoding of explicitText can be specified by prefixing
       the value with UTF8, BMP, or VISIBLE followed by colon. For example:

        explicitText = "UTF8:Explicit Text Here"

   Policy Constraints
       This is a multi-valued extension which consisting of the names
       requireExplicitPolicy or inhibitPolicyMapping and a non negative
       integer value. At least one component must be present.


        policyConstraints = requireExplicitPolicy:3

   Inhibit Any Policy
       This is a string extension whose value must be a non negative integer.


        inhibitAnyPolicy = 2

   Name Constraints
       This is a multi-valued extension. The name should begin with the word
       permitted or excluded followed by a ;. The rest of the name and the
       value follows the syntax of subjectAltName except email:copy is not
       supported and the IP form should consist of an IP addresses and subnet
       mask separated by a /.


        nameConstraints = permitted;IP:

        nameConstraints = permitted;email:.example.com

        nameConstraints = excluded;email:.com

   OCSP No Check
       This is a string extension. It is parsed, but ignored.


        noCheck = ignored

   TLS Feature (aka Must Staple)
       This is a multi-valued extension consisting of a list of TLS extension
       identifiers. Each identifier may be a number (0..65535) or a supported
       name.  When a TLS client sends a listed extension, the TLS server is
       expected to include that extension in its reply.

       The supported names are: status_request and status_request_v2.


        tlsfeature = status_request

       The following extensions are non standard, Netscape specific and
       largely obsolete. Their use in new applications is discouraged.

   Netscape String extensions
       Netscape Comment (nsComment) is a string extension containing a comment
       which will be displayed when the certificate is viewed in some
       browsers.  Other extensions of this type are: nsBaseUrl,
       nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl and

   Netscape Certificate Type
       This is a multi-valued extensions which consists of a list of flags to
       be included. It was used to indicate the purposes for which a
       certificate could be used. The basicConstraints, keyUsage and extended
       key usage extensions are now used instead.

       Acceptable values for nsCertType are: client, server, email, objsign,
       reserved, sslCA, emailCA, objCA.

       If an extension is not supported by the OpenSSL code then it must be
       encoded using the arbitrary extension format. It is also possible to
       use the arbitrary format for supported extensions. Extreme care should
       be taken to ensure that the data is formatted correctly for the given
       extension type.

       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(3).  For example:

        [extensions] = critical, ASN1:UTF8String:Some random data = ASN1:SEQUENCE:seq_sect

        field1 = UTF8:field1
        field2 = UTF8:field2

       It is also possible to use the word DER to include the raw encoded data
       in any extension. = critical, DER:01:02:03:04 = 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

       There is no guarantee that a specific implementation will process a
       given extension. It may therefore be sometimes possible to use
       certificates for purposes prohibited by their extensions because a
       specific application does not recognize or honour the values of the
       relevant extensions.

       The DER and ASN1 options should be used with caution. It is possible to
       create invalid extensions if they are not used carefully.

       openssl-req(1), openssl-ca(1), openssl-x509(1), ASN1_generate_nconf(3)

       Copyright 2004-2023 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at

3.0.12                            2023-10-25                  X509V3_CONFIG(5)