{ "mode": "man", "parameter": "x509v3_config", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/x509v3_config/5/json", "generated": "2026-05-30T10:44:47Z", "sections": { "NAME": { "content": "x509v3config - X509 V3 certificate extension configuration format\n", "subsections": [] }, "DESCRIPTION": { "content": "Several OpenSSL commands can add extensions to a certificate or certificate request based on\nthe contents of a configuration file and CLI options such as -addext. The syntax of\nconfiguration files is described in config(5). The commands typically have an option to\nspecify the name of the configuration file, and a section within that file; see the\ndocumentation of the individual command for details.\n\nThis page uses extensions as the name of the section, when needed in examples.\n\nEach entry in the extension section takes the form:\n\nname = [critical, ]value(s)\n\nIf critical is present then the extension will be marked as critical.\n\nIf multiple entries are processed for the same extension name, later entries override earlier\nones with the same name.\n\nThe format of values depends on the value of name, many have a type-value pairing where the\ntype and value are separated by a colon. There are four main types of extension:\n\nstring\nmulti-valued\nraw\narbitrary\n\nEach is described in the following paragraphs.\n\nString extensions simply have a string which contains either the value itself or how it is\nobtained.\n\nMulti-valued extensions have a short form and a long form. The short form is a comma-\nseparated list of names and values:\n\nbasicConstraints = critical, CA:true, pathlen:1\n\nThe long form allows the values to be placed in a separate section:\n\n[extensions]\nbasicConstraints = critical, @basicconstraints\n\n[basicconstraints]\nCA = true\npathlen = 1\n\nBoth forms are equivalent.\n\nIf an extension is multi-value and a field value must contain a comma the long form must be\nused otherwise the comma would be misinterpreted as a field separator. For example:\n\nsubjectAltName = URI:ldap://somehost.com/CN=foo,OU=bar\n\nwill produce an error but the equivalent form:\n\n[extensions]\nsubjectAltName = @subjectaltsection\n\n[subjectaltsection]\nsubjectAltName = URI:ldap://somehost.com/CN=foo,OU=bar\n\nis valid.\n\nOpenSSL does not support multiple occurrences of the same field within a section. In this\nexample:\n\n[extensions]\nsubjectAltName = @altsection\n\n[altsection]\nemail = steve@example.com\nemail = steve@example.org\n\nwill only recognize the last value. To specify multiple values append a numeric identifier,\nas shown here:\n\n[extensions]\nsubjectAltName = @altsection\n\n[altsection]\nemail.1 = steve@example.com\nemail.2 = steve@example.org\n\nThe syntax of raw extensions is defined by the source code that parses the extension but\nshould be documened. See \"Certificate Policies\" for an example of a raw extension.\n\nIf an extension type is unsupported, then the arbitrary extension syntax must be used, see\nthe \"ARBITRARY EXTENSIONS\" section for more details.\n", "subsections": [] }, "STANDARD EXTENSIONS": { "content": "The following sections describe the syntax of each supported extension. They do not define\nthe semantics of the extension.\n", "subsections": [ { "name": "Basic Constraints", "content": "This is a multi-valued extension which indicates whether a certificate is a CA certificate.\nThe first value is CA followed by TRUE or FALSE. If CA is TRUE then an optional pathlen name\nfollowed by a nonnegative value can be included.\n\nFor example:\n\nbasicConstraints = CA:TRUE\n\nbasicConstraints = CA:FALSE\n\nbasicConstraints = critical, CA:TRUE, pathlen:1\n\nA CA certificate must include the basicConstraints name with the CA parameter set to TRUE. An\nend-user certificate must either have CA:FALSE or omit the extension entirely. The pathlen\nparameter specifies the maximum number of CAs that can appear below this one in a chain. A\npathlen of zero means the CA cannot sign any sub-CA's, and can only sign end-entity\ncertificates.\n" }, { "name": "Key Usage", "content": "Key usage is a multi-valued extension consisting of a list of names of the permitted key\nusages. The defined values are: \"digitalSignature\", \"nonRepudiation\", \"keyEncipherment\",\n\"dataEncipherment\", \"keyAgreement\", \"keyCertSign\", \"cRLSign\", \"encipherOnly\", and\n\"decipherOnly\".\n\nExamples:\n\nkeyUsage = digitalSignature, nonRepudiation\n\nkeyUsage = critical, keyCertSign\n" }, { "name": "Extended Key Usage", "content": "This extension consists of a list of values indicating purposes for which the certificate\npublic key can be used. Each value can be either a short text name or an OID. The following\ntext names, and their intended meaning, are known:\n\nValue Meaning according to RFC 5280 etc.\n----- ----------------------------------\nserverAuth SSL/TLS WWW Server Authentication\nclientAuth SSL/TLS WWW Client Authentication\ncodeSigning Code Signing\nemailProtection E-mail Protection (S/MIME)\ntimeStamping Trusted Timestamping\nOCSPSigning OCSP Signing\nipsecIKE ipsec Internet Key Exchange\nmsCodeInd Microsoft Individual Code Signing (authenticode)\nmsCodeCom Microsoft Commercial Code Signing (authenticode)\nmsCTLSign Microsoft Trust List Signing\nmsEFS Microsoft Encrypted File System\n\nWhile IETF RFC 5280 says that id-kp-serverAuth and id-kp-clientAuth are only for WWW use, in\npractice they are used for all kinds of TLS clients and servers, and this is what OpenSSL\nassumes as well.\n\nExamples:\n\nextendedKeyUsage = critical, codeSigning, 1.2.3.4\n\nextendedKeyUsage = serverAuth, clientAuth\n" }, { "name": "Subject Key Identifier", "content": "The SKID extension specification has a value with three choices. If the value is the word\nnone then no SKID extension will be included. If the value is the word hash, or by default\nfor the x509, req, and ca apps, the process specified in RFC 5280 section 4.2.1.2. (1) is\nfollowed: The keyIdentifier is composed of the 160-bit SHA-1 hash of the value of the BIT\nSTRING subjectPublicKey (excluding the tag, length, and number of unused bits).\n\nOtherwise, the value must be a hex string (possibly with \":\" separating bytes) to output\ndirectly, however, this is strongly discouraged.\n\nExample:\n\nsubjectKeyIdentifier = hash\n" }, { "name": "Authority Key Identifier", "content": "The AKID extension specification may have the value none indicating that no AKID shall be\nincluded. Otherwise it may have the value keyid or issuer or both of them, separated by \",\".\nEither or both can have the option always, indicated by putting a colon \":\" between the value\nand this option. For self-signed certificates the AKID is suppressed unless always is\npresent. By default the x509, req, and ca apps behave as if \"none\" was given for self-signed\ncertificates and \"keyid, issuer\" otherwise.\n\nIf keyid is present, an attempt is made to copy the subject key identifier (SKID) from the\nissuer certificate except if the issuer certificate is the same as the current one and it is\nnot self-signed. The hash of the public key related to the signing key is taken as fallback\nif the issuer certificate is the same as the current certificate. If always is present but\nno value can be obtained, an error is returned.\n\nIf issuer is present, and in addition it has the option always specified or keyid is not\npresent, then the issuer DN and serial number are copied from the issuer certificate.\n\nExamples:\n\nauthorityKeyIdentifier = keyid, issuer\n\nauthorityKeyIdentifier = keyid, issuer:always\n" }, { "name": "Subject Alternative Name", "content": "This is a multi-valued extension that supports several types of name identifier, including\nemail (an email address), URI (a uniform resource indicator), DNS (a DNS domain name), RID (a\nregistered ID: OBJECT IDENTIFIER), IP (an IP address), dirName (a distinguished name), and\notherName. The syntax of each is described in the following paragraphs.\n\nThe email option has two special values. \"copy\" will automatically include any email\naddresses contained in the certificate subject name in the extension. \"move\" will\nautomatically move any email addresses from the certificate subject name to the extension.\n\nThe IP address used in the IP option can be in either IPv4 or IPv6 format.\n\nThe value of dirName is specifies the configuration section containing the distinguished name\nto use, as a set of name-value pairs. Multi-valued AVAs can be formed by prefacing the name\nwith a + character.\n\nThe value of otherName can include arbitrary data associated with an OID; the value should be\nthe OID followed by a semicolon and the content in specified using the syntax in\nASN1generatenconf(3).\n\nExamples:\n\nsubjectAltName = email:copy, email:my@example.com, URI:http://my.example.com/\n\nsubjectAltName = IP:192.168.7.1\n\nsubjectAltName = IP:13::17\n\nsubjectAltName = email:my@example.com, RID:1.2.3.4\n\nsubjectAltName = otherName:1.2.3.4;UTF8:some other identifier\n\n[extensions]\nsubjectAltName = dirName:dirsect\n\n[dirsect]\nC = UK\nO = My Organization\nOU = My Unit\nCN = My Name\n\nNon-ASCII Email Address conforming the syntax defined in Section 3.3 of RFC 6531 are provided\nas otherName.SmtpUTF8Mailbox. According to RFC 8398, the email address should be provided as\nUTF8String. To enforce the valid representation in the certificate, the SmtpUTF8Mailbox\nshould be provided as follows\n\nsubjectAltName=@alts\n[alts]\notherName = 1.3.6.1.5.5.7.8.9;FORMAT:UTF8,UTF8String:nonasciiname.example.com\n" }, { "name": "Issuer Alternative Name", "content": "This extension supports most of the options of subject alternative name; it does not support\nemail:copy. It also adds issuer:copy as an allowed value, which copies any subject\nalternative names from the issuer certificate, if possible.\n\nExample:\n\nissuerAltName = issuer:copy\n" }, { "name": "Authority Info Access", "content": "This extension gives details about how to retrieve information that related to the\ncertificate that the CA makes available. The syntax is accessid;location, where accessid is\nan object identifier (although only a few values are well-known) and location has the same\nsyntax as subject alternative name (except that email:copy is not supported).\n\nPossible values for accessid include OCSP (OCSP responder), caIssuers (CA Issuers),\nadtimestamping (AD Time Stamping), ADDVCS (ad dvcs), caRepository (CA Repository).\n\nExamples:\n\nauthorityInfoAccess = OCSP;URI:http://ocsp.example.com/,caIssuers;URI:http://myca.example.com/ca.cer\n\nauthorityInfoAccess = OCSP;URI:http://ocsp.example.com/\n" }, { "name": "CRL distribution points", "content": "This is a multi-valued extension whose values can be either a name-value pair using the same\nform as subject alternative name or a single value specifying the section name containing all\nthe distribution point values.\n\nWhen a name-value pair is used, a DistributionPoint extension will be set with the given\nvalue as the fullName field as the distributionPoint value, and the reasons and cRLIssuer\nfields will be omitted.\n\nWhen a single option is used, the value specifies the section, and that section can have the\nfollowing items:\n\nfullname\nThe full name of the distribution point, in the same format as the subject alternative\nname.\n\nrelativename\nThe value is taken as a distinguished name fragment that is set as the value of the\nnameRelativeToCRLIssuer field.\n\nCRLIssuer\nThe value must in the same format as the subject alternative name.\n\nreasons\nA multi-value field that contains the reasons for revocation. The recognized values are:\n\"keyCompromise\", \"CACompromise\", \"affiliationChanged\", \"superseded\",\n\"cessationOfOperation\", \"certificateHold\", \"privilegeWithdrawn\", and \"AACompromise\".\n\nOnly one of fullname or relativename should be specified.\n\nSimple examples:\n\ncrlDistributionPoints = URI:http://example.com/myca.crl\n\ncrlDistributionPoints = URI:http://example.com/myca.crl, URI:http://example.org/my.crl\n\nFull distribution point example:\n\n[extensions]\ncrlDistributionPoints = crldp1section\n\n[crldp1section]\nfullname = URI:http://example.com/myca.crl\nCRLissuer = dirName:issuersect\nreasons = keyCompromise, CACompromise\n\n[issuersect]\nC = UK\nO = Organisation\nCN = Some Name\n" }, { "name": "Issuing Distribution Point", "content": "This extension should only appear in CRLs. It is a multi-valued extension whose syntax is\nsimilar to the \"section\" pointed to by the CRL distribution points extension. The following\nnames have meaning:\n\nfullname\nThe full name of the distribution point, in the same format as the subject alternative\nname.\n\nrelativename\nThe value is taken as a distinguished name fragment that is set as the value of the\nnameRelativeToCRLIssuer field.\n\nonlysomereasons\nA multi-value field that contains the reasons for revocation. The recognized values are:\n\"keyCompromise\", \"CACompromise\", \"affiliationChanged\", \"superseded\",\n\"cessationOfOperation\", \"certificateHold\", \"privilegeWithdrawn\", and \"AACompromise\".\n\nonlyuser, onlyCA, onlyAA, indirectCRL\nThe value for each of these names is a boolean.\n\nExample:\n\n[extensions]\nissuingDistributionPoint = critical, @idpsection\n\n[idpsection]\nfullname = URI:http://example.com/myca.crl\nindirectCRL = TRUE\nonlysomereasons = keyCompromise, CACompromise\n" }, { "name": "Certificate Policies", "content": "This is a raw extension that supports all of the defined fields of the certificate extension.\n\nPolicies without qualifiers are specified by giving the OID. Multiple policies are comma-\nseparated. For example:\n\ncertificatePolicies = 1.2.4.5, 1.1.3.4\n\nTo include policy qualifiers, use the \"@section\" syntax to point to a section that specifies\nall the information.\n\nThe section referred to must include the policy OID using the name policyIdentifier. cPSuri\nqualifiers can be included using the syntax:\n\nCPS.nnn = value\n\nwhere \"nnn\" is a number.\n\nuserNotice qualifiers can be set using the syntax:\n\nuserNotice.nnn = @notice\n\nThe value of the userNotice qualifier is specified in the relevant section. This section can\ninclude explicitText, organization, and noticeNumbers options. explicitText and organization\nare text strings, noticeNumbers is a comma separated list of numbers. The organization and\nnoticeNumbers options (if included) must BOTH be present. Some software might require the\nia5org option at the top level; this changes the encoding from Displaytext to IA5String.\n\nExample:\n\n[extensions]\ncertificatePolicies = ia5org, 1.2.3.4, 1.5.6.7.8, @polsect\n\n[polsect]\npolicyIdentifier = 1.3.5.8\nCPS.1 = \"http://my.host.example.com/\"\nCPS.2 = \"http://my.your.example.com/\"\nuserNotice.1 = @notice\n\n[notice]\nexplicitText = \"Explicit Text Here\"\norganization = \"Organisation Name\"\nnoticeNumbers = 1, 2, 3, 4\n\nThe character encoding of explicitText can be specified by prefixing the value with UTF8,\nBMP, or VISIBLE followed by colon. For example:\n\n[notice]\nexplicitText = \"UTF8:Explicit Text Here\"\n" }, { "name": "Policy Constraints", "content": "This is a multi-valued extension which consisting of the names requireExplicitPolicy or\ninhibitPolicyMapping and a non negative integer value. At least one component must be\npresent.\n\nExample:\n\npolicyConstraints = requireExplicitPolicy:3\n" }, { "name": "Inhibit Any Policy", "content": "This is a string extension whose value must be a non negative integer.\n\nExample:\n\ninhibitAnyPolicy = 2\n" }, { "name": "Name Constraints", "content": "This is a multi-valued extension. The name should begin with the word permitted or excluded\nfollowed by a ;. The rest of the name and the value follows the syntax of subjectAltName\nexcept email:copy is not supported and the IP form should consist of an IP addresses and\nsubnet mask separated by a /.\n\nExamples:\n\nnameConstraints = permitted;IP:192.168.0.0/255.255.0.0\n\nnameConstraints = permitted;email:.example.com\n\nnameConstraints = excluded;email:.com\n" }, { "name": "OCSP No Check", "content": "This is a string extension. It is parsed, but ignored.\n\nExample:\n\nnoCheck = ignored\n" }, { "name": "TLS Feature (aka Must Staple)", "content": "This is a multi-valued extension consisting of a list of TLS extension identifiers. Each\nidentifier may be a number (0..65535) or a supported name. When a TLS client sends a listed\nextension, the TLS server is expected to include that extension in its reply.\n\nThe supported names are: statusrequest and statusrequestv2.\n\nExample:\n\ntlsfeature = statusrequest\n" } ] }, "DEPRECATED EXTENSIONS": { "content": "The following extensions are non standard, Netscape specific and largely obsolete. Their use\nin new applications is discouraged.\n", "subsections": [ { "name": "Netscape String extensions", "content": "Netscape Comment (nsComment) is a string extension containing a comment which will be\ndisplayed when the certificate is viewed in some browsers. Other extensions of this type\nare: nsBaseUrl, nsRevocationUrl, nsCaRevocationUrl, nsRenewalUrl, nsCaPolicyUrl and\nnsSslServerName.\n" }, { "name": "Netscape Certificate Type", "content": "This is a multi-valued extensions which consists of a list of flags to be included. It was\nused to indicate the purposes for which a certificate could be used. The basicConstraints,\nkeyUsage and extended key usage extensions are now used instead.\n\nAcceptable values for nsCertType are: client, server, email, objsign, reserved, sslCA,\nemailCA, objCA.\n" } ] }, "ARBITRARY EXTENSIONS": { "content": "If an extension is not supported by the OpenSSL code then it must be encoded using the\narbitrary extension format. It is also possible to use the arbitrary format for supported\nextensions. Extreme care should be taken to ensure that the data is formatted correctly for\nthe given extension type.\n\nThere are two ways to encode arbitrary extensions.\n\nThe first way is to use the word ASN1 followed by the extension content using the same syntax\nas ASN1generatenconf(3). For example:\n\n[extensions]\n1.2.3.4 = critical, ASN1:UTF8String:Some random data\n1.2.3.4.1 = ASN1:SEQUENCE:seqsect\n\n[seqsect]\nfield1 = UTF8:field1\nfield2 = UTF8:field2\n\nIt is also possible to use the word DER to include the raw encoded data in any extension.\n\n1.2.3.4 = critical, DER:01:02:03:04\n1.2.3.4.1 = DER:01020304\n\nThe value following DER is a hex dump of the DER encoding of the extension Any extension can\nbe placed in this form to override the default behaviour. For example:\n\nbasicConstraints = critical, DER:00:01:02:03\n", "subsections": [] }, "WARNINGS": { "content": "There is no guarantee that a specific implementation will process a given extension. It may\ntherefore be sometimes possible to use certificates for purposes prohibited by their\nextensions because a specific application does not recognize or honour the values of the\nrelevant extensions.\n\nThe DER and ASN1 options should be used with caution. It is possible to create invalid\nextensions if they are not used carefully.\n", "subsections": [] }, "SEE ALSO": { "content": "openssl-req(1), openssl-ca(1), openssl-x509(1), ASN1generatenconf(3)\n", "subsections": [] }, "COPYRIGHT": { "content": "Copyright 2004-2021 The OpenSSL Project Authors. All Rights Reserved.\n\nLicensed under the Apache License 2.0 (the \"License\"). You may not use this file except in\ncompliance with the License. You can obtain a copy in the file LICENSE in the source\ndistribution or at .\n\n\n\n3.0.2 2026-04-07 X509V3CONFIG(5SSL)", "subsections": [] } }, "summary": "x509v3config - X509 V3 certificate extension configuration format", "flags": [], "examples": [], "see_also": [ { "name": "openssl-req", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-req/1/json" }, { "name": "openssl-ca", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-ca/1/json" }, { "name": "openssl-x509", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-x509/1/json" }, { "name": "ASN1generatenconf", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/ASN1generatenconf/3/json" } ] }