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

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 of 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.

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 preceeding 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

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.

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 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
issuingDistributionPoint = idp_section

OCSP No Check

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

Example:

noCheck = ignored

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.