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x509v3_config(5)




X509V3_CONFIG(5)             OpenSSL             X509V3_CONFIG(5)


NAME

     x509v3_config - X509 V3 certificate extension configuration
     format


DESCRIPTION

     Several of the OpenSSL utilities can add extensions to a
     certificate or certificate request based on the contents of
     a configuration file.

     Typically the application will contain an option to point to
     an extension section. Each line of the extension section
     takes the form:

      extension_name=[critical,] extension_options

     If critical is present then the extension will be critical.

     The format of extension_options depends on the value of
     extension_name.

     There are four main types of extension: string extensions,
     multi-valued extensions, raw and arbitrary 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.

     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.

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


STANDARD EXTENSIONS

     The following sections describe each supported extension in
     detail.

     Basic Constraints.

     This is a multi valued extension which indicates whether a
     certificate is a CA certificate. The first (mandatory) name
     is CA followed by TRUE or FALSE. If CA is TRUE then an
     optional pathlen name followed by an non-negative value can
     be included.

     For example:

      basicConstraints=CA:TRUE

      basicConstraints=CA:FALSE

      basicConstraints=critical,CA:TRUE, pathlen:0

     A CA certificate must include the basicConstraints value
     with the CA field set to TRUE. An end user certificate must
     either set CA to FALSE or exclude the extension entirely.
     Some software may require the inclusion of basicConstraints
     with CA set to FALSE for end entity certificates.

     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.

     Key Usage.

     Key usage is a multi valued extension consisting of a list
     of names of the permitted key usages.

     The supporte names are: digitalSignature, nonRepudiation,
     keyEncipherment, dataEncipherment, keyAgreement,
     keyCertSign, cRLSign, encipherOnly and decipherOnly.

     Examples:

      keyUsage=digitalSignature, nonRepudiation

      keyUsage=critical, keyCertSign

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     Extended Key Usage.

     This extensions consists of a list of usages indicating
     purposes for which the certificate public key can be used
     for,

     These can either be object short names or 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

     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 the word hash which will automatically follow
     the guidelines in RFC3280 or a hex string giving the
     extension value to include. 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 error is returned if
     the option fails.

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     The issuer option copies the issuer and serial number from
     the issuer certificate. This will only be done if the keyid
     option fails or is not included unless the "always" flag
     will always include the value.

     Example:

      authorityKeyIdentifier=keyid,issuer

     Subject Alternative Name.

     The subject alternative name extension allows various
     literal values to be included in the configuration file.
     These include 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 email option include a special 'copy' value. This will
     automatically include and email addresses contained in the
     certificate subject name in the extension.

     The IP address used in the IP options can be in either IPv4
     or IPv6 format.

     The value of dirName should point to a section containing
     the distinguished name to use as a set of name value pairs.
     Multi values AVAs can be formed by prefacing the name with a
     + character.

     otherName can include arbitrary data associated with an OID:
     the value should be the OID followed by a semicolon and the
     content in standard ASN1_generate_nconf(3) format.

     Examples:

      subjectAltName=email:copy,email:my@other.address,URI:http://my.url.here/
      subjectAltName=IP:192.168.7.1
      subjectAltName=IP:13::17
      subjectAltName=email:my@other.address,RID:1.2.3.4
      subjectAltName=otherName:1.2.3.4;UTF8:some other identifier

      subjectAltName=dirName:dir_sect

      [dir_sect]
      C=UK
      O=My Organization
      OU=My Unit
      CN=My Name

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     Issuer Alternative Name.

     The issuer alternative name option supports all the literal
     options of subject alternative name. It does not support the
     email:copy option because that would not make sense. It does
     support an additional issuer:copy option that will copy all
     the subject alternative name values from the issuer
     certificate (if possible).

     Example:

      issuserAltName = issuer:copy

     Authority Info Access.

     The authority information access extension gives details
     about how to access certain information relating to the CA.
     Its syntax is accessOID;location where location has the same
     syntax as subject alternative name (except that email:copy
     is not supported). accessOID can be any valid OID but only
     certain values are meaningful, for example OCSP and
     caIssuers.

     Example:

      authorityInfoAccess = OCSP;URI:http://ocsp.my.host/
      authorityInfoAccess = caIssuers;URI:http://my.ca/ca.html

     CRL distribution points.

     This is a multi-valued extension whose options can be either
     in name:value pair using the same form as subject
     alternative name or a single value representing a section
     name containing all the distribution point fields.

     For a name:value pair a new DistributionPoint with the
     fullName field set to the given value both the cRLissuer and
     reasons fields are omitted in this case.

     In the single option case the section indicated contains
     values for each field. In this section:

     If the name is "fullname" the value field should contain the
     full name of the distribution point in the same format as
     subject alternative name.

     If the name is "relativename" then the value field should
     contain a section name whose contents represent a DN
     fragment to be placed in this field.

     The name "CRLIssuer" if present should contain a value for
     this field in subject alternative name format.

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     If the name is "reasons" the value field should consist of a
     comma separated field containing the reasons. Valid reasons
     are: "keyCompromise", "CACompromise", "affiliationChanged",
     "superseded", "cessationOfOperation", "certificateHold",
     "privilegeWithdrawn" and "AACompromise".

     Simple examples:

      crlDistributionPoints=URI:http://myhost.com/myca.crl
      crlDistributionPoints=URI:http://my.com/my.crl,URI:http://oth.com/my.crl

     Full distribution point example:

      crlDistributionPoints=crldp1_section

      [crldp1_section]

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

      [issuer_sect]
      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 with a
     few differences.

     The names "reasons" and "CRLissuer" are not recognized.

     The name "onlysomereasons" is accepted which sets this
     field. The value is in the same format as the CRL
     distribution point "reasons" field.

     The names "onlyuser", "onlyCA", "onlyAA" and "indirectCRL"
     are also accepted the values should be a boolean value (TRUE
     or FALSE) to indicate the value of the corresponding field.

     Example:

      issuingDistributionPoint=critical, @idp_section

      [idp_section]

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

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      [issuer_sect]
      C=UK
      O=Organisation
      CN=Some Name

     Certificate Policies.

     This is a raw extension. All the fields of this extension
     can be set by using the appropriate syntax.

     If you follow the PKIX recommendations and just using one
     OID then you just include the value of that OID. Multiple
     OIDs can be set separated by commas, for example:

      certificatePolicies= 1.2.4.5, 1.1.3.4

     If you wish to include qualifiers then the policy OID and
     qualifiers need to be specified in a separate section: this
     is done by using the @section syntax instead of a literal
     OID value.

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

      CPS.nnn=value

     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. If
     you use the userNotice option with IE5 then you need the
     'ia5org' option at the top level to modify the encoding:
     otherwise it will not be interpreted properly.

     Example:

      certificatePolicies=ia5org,1.2.3.4,1.5.6.7.8,@polsect

      [polsect]

      policyIdentifier = 1.3.5.8
      CPS.1="http://my.host.name/"
      CPS.2="http://my.your.name/"
      userNotice.1=@notice

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      [notice]

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

     The ia5org option changes the type of the organization
     field. In RFC2459 it can only be of type DisplayText. In
     RFC3280 IA5Strring is also permissible.  Some software (for
     example some versions of MSIE) may require ia5org.

     Policy Constraints

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

     Example:

      policyConstraints = requireExplicitPolicy:3

     Inhibit Any Policy

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

     Example:

      inhibitAnyPolicy = 2

     Name Constraints

     The name constraints extension 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 /.

     Examples:

      nameConstraints=permitted;IP:192.168.0.0/255.255.0.0

      nameConstraints=permitted;email:.somedomain.com

      nameConstraints=excluded;email:.com

     OCSP No Check

     The OCSP No Check extension is a string extension but its
     value is ignored.

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     Example:

      noCheck = ignored


DEPRECATED EXTENSIONS

     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.

     Example:

      nsComment = "Some Random Comment"

     Other supported extensions in this category are: nsBaseUrl,
     nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl,
     nsCaPolicyUrl and nsSslServerName.

     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.


ARBITRARY EXTENSIONS

     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:

      1.2.3.4=critical,ASN1:UTF8String:Some random data

      1.2.3.4=ASN1:SEQUENCE:seq_sect

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      [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.

      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

     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 totally invalid extensions if they are
     not used carefully.


NOTES

     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

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

     is valid.

     Due to the behaviour of the OpenSSL conf library the same
     field name can only occur once in a section. This means
     that:

      subjectAltName=@alt_section

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      [alt_section]

      email=steve@here
      email=steve@there

     will only recognize the last value. This can be worked
     around by using the form:

      [alt_section]

      email.1=steve@here
      email.2=steve@there


HISTORY

     The X509v3 extension code was first added to OpenSSL 0.9.2.

     Policy mappings, inhibit any policy and name constraints
     support was added in OpenSSL 0.9.8

     The directoryName and otherName option as well as the ASN1
     option for arbitrary extensions was added in OpenSSL 0.9.8


SEE ALSO

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

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