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:

 issuerAltName = 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.

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 Valid reasons are: "keyCompromise", "CACompromise", "affiliationChanged", "superseded", "cessationOfOperation", "certificateHold", "privilegeWithdrawn" and "AACompromise".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

 [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

 [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 IA5String is also permissible. Some software (for example some versions of MSIE) may require ia5org.

ASN1 type of explicitText can be specified by prepending UTF8, BMP or VISIBLE prefix followed by colon. For example:

 [notice]
 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.

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.

Example:

 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.

Example:

 tlsfeature = status_request

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 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

 [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

SEE ALSO