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NAMEx509v3_config - X509 V3 certificate extension configuration format
DESCRIPTIONSeveral 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:
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.
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:
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.
If an extension type is unsupported then the arbitrary extension syntax must be used, see the
STANDARD EXTENSIONSThe following sections describe each supported extension in detail.
Basic Constraints.This is a multi valued extension which indicates whether a certificate is a
basicConstraints=CA:TRUE basicConstraints=CA:FALSE basicConstraints=critical,CA:TRUE, pathlen:0
The pathlen parameter indicates the maximum number of CAs that can appear below this one in a chain. So if you have a
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.
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
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
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
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.
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)
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 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
subjectAltName=email:copy,email:firstname.lastname@example.org,URI:my.url.here subjectAltName=IP:192.168.7.1 subjectAltName=IP:13::17 subjectAltName=email:email@example.com,RID:188.8.131.52 subjectAltName=otherName:184.108.40.206;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).
issuserAltName = issuer:copy
Authority Info Access.The authority information access extension gives details about how to access certain information relating to the
authorityInfoAccess = OCSP;URI:ocsp.my.host authorityInfoAccess = caIssuers;URI: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
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''.
Full distribution point example:
crlDistributionPoints=crldp1_section [crldp1_section] fullname=URI:myhost.com/myca.crl CRLissuer=dirName:issuer_sect reasons=keyCompromise, CACompromise [issuer_sect] C=UK O=Organisation CN=Some Name
Issuing Distribution PointThis extension should only appear in CRLs. It is a multi valued extension whose syntax is similar to the ``section'' pointed to by the
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
The names ``onlyuser'', ``onlyCA'', ``onlyAA'' and ``indirectCRL'' are also accepted the values should be a boolean value (
issuingDistributionPoint=critical, @idp_section [idp_section] fullname=URI: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
certificatePolicies= 220.127.116.11, 18.104.22.168
If you wish to include qualifiers then the policy
The section referred to must include the policy
userNotice qualifiers can be set using the syntax:
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
certificatePolicies=ia5org,22.214.171.124,126.96.36.199.8,@polsect [polsect] policyIdentifier = 188.8.131.52 CPS.1="my.host.name" CPS.2="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
Policy ConstraintsThis 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.
policyConstraints = requireExplicitPolicy:3
Inhibit Any PolicyThis is a string extension whose value must be a non negative integer.
inhibitAnyPolicy = 2
Name ConstraintsThe 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
nameConstraints=permitted;IP:192.168.0.0/255.255.0.0 nameConstraints=permitted;email:.somedomain.com nameConstraints=excluded;email:.com
noCheck = ignored
DEPRECATED EXTENSIONSThe 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.
nsComment = "Some Random Comment"
Other supported extensions in this category are: nsBaseUrl, nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl and nsSslServerName.
Netscape Certificate TypeThis 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 EXTENSIONSIf 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
184.108.40.206=critical,ASN1:UTF8String:Some random data 220.127.116.11=ASN1:SEQUENCE:seq_sect [seq_sect] field1 = UTF8:field1 field2 = UTF8:field2
It is also possible to use the word
The value following
WARNINGThere 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.
NOTESIf 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:
will produce an error but the equivalent form:
subjectAltName=@subject_alt_section [subject_alt_section] subjectAltName=URI:ldap://somehost.com/CN=foo,OU=bar
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
HISTORYThe 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