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Crypt::PKCS10 - parse PKCS #10 certificate requests


version 1.800201


    use Crypt::PKCS10;

    Crypt::PKCS10->setAPIversion( 1 );
    my $decoded = Crypt::PKCS10->new( $csr ) or die Crypt::PKCS10->error;

    print $decoded;

    @names = $decoded->extensionValue('subjectAltName' );
    @names = $decoded->subject unless( @names );

    %extensions = map { $_ => $decoded->extensionValue( $_ ) } $decoded->extensions


Crypt::PKCS10 parses PKCS #10 certificate requests (CSRs) and provides accessor methods to extract the data in usable form.

Common object identifiers will be translated to their corresponding names. Additionally, accessor methods allow extraction of single data fields. The format of returned data varies by accessor.

The access methods return the value corresponding to their name. If called in scalar context, they return the first value (or an empty string). If called in array context, they return all values.

true values should be specified as 1 and false values as 0. Future API changes may provide different functions when other values are used.


Crypt::PKCS10 - parse PKCS #10 certificate requests


Access methods may exist for subject name components that are not listed here. To test for these, use code of the form:

  $locality = $decoded->localityName if( $decoded->can('localityName') );

If a name component exists in a CSR, the method will be present. The converse is not (always) true.

class method setAPIversion( $version )

Selects the API version (0 or 1) expected.

Must be called before calling any other method.

The API version determines how a CSR is parsed. Changing the API version after parsing a CSR will cause accessors to produce unpredictable results.

Version 0 - DEPRECATED

Some OID names have spaces and descriptions

This is the format used for Crypt::PKCS10 version 1.3 and lower. The attributes method returns legacy data.

Some new API functions are disabled.

Version 1

OID names from RFCs - or at least compatible with OpenSSL and ASN.1 notation. The attributes method conforms to version 1.

If not called, a warning will be generated and the API will default to version 0.

In a future release, the warning will be changed to a fatal exception.

To ease migration, both old and new names are accepted by the API.

Every program should call setAPIversion(1).

class method getAPIversion

Returns the current API version.

Returns undef if setAPIversion has never been called.

class method new( $csr, %options )

Constructor, creates a new object containing the parsed PKCS #10 certificate request.

$csr may be a scalar containing the request, a file name, or a file handle from which to read it.

If a file name is specified, the readFile option must be specified.

If a file handle is supplied, the caller should specify acceptPEM => 0 if the contents are DER.

The request may be PEM or binary DER encoded. Only one request is processed.

If PEM, other data (such as mail headers) may precede or follow the CSR.

    my $decoded = Crypt::PKCS10->new( $csr ) or die Crypt::PKCS10->error;

Returns undef if there is an I/O error or the request can not be parsed successfully.

Call error() to obtain more detail.


The options are specified as name => value.

If the first option is a HASHREF, it is expanded and any remaining options are added.


If false, the input must be in DER format. binmode will be called on a file handle.

If true, the input is checked for a CERTIFICATE REQUEST header. If not found, the csr is assumed to be in DER format.

Default is true.


If true, the input must be in PEM format. An error will be returned if the input doesn't contain a CERTIFICATE REQUEST header. If false, the input is parsed according to acceptPEM.

Default is false.


If true, an input file or file handle will be set to binary mode prior to reading.

If false, an input file or file handle's binmode will not be modified.

Defaults to false if acceptPEM is true, otherwise true.


If true, any API function that sets an error string will also die.

If false, exceptions are only generated for fatal conditions.

The default is false. API version 1 only..


If true, strings returned for extension and attribute values are '\'-escaped when formatted. This is compatible with OpenSSL configuration files.

The special characters are: '\', '$', and '"'

If false, these strings are not '\'-escaped. This is useful when they are being displayed to a human.

The default is true.


If true, most invalid base64 characters in PEM data will be ignored. For example, this will accept CSRs prefixed with '> ', as e-mail when the PEM is inadvertently quoted. Note that the BEGIN and END lines may not be corrupted.

If false, invalid base64 characters in PEM data will cause the CSR to be rejected.

The default is false.


If true, $csr is the name of a file containing the CSR.

If false, $csr contains the CSR or is an open file handle.

The default is false.


If true, the CSR's signature is checked. If verification fails, new will fail. Requires API version 1.

If false, the CSR's signature is not checked.

The default is true for API version 1 and false for API version 0.

No exceptions are generated, unless dieOnError is set or new() is called in void context.

The defaults will accept either PEM or DER from a string or file hande, which will not be set to binary mode. Automatic detection of the data format may not be reliable on file systems that represent text and binary files differently. Set acceptPEM to false and PEMonly to match the file type on these systems.

The object will stringify to a human-readable representation of the CSR. This is useful for debugging and perhaps for displaying a request. However, the format is not part of the API and may change. It should not be parsed by automated tools.

Exception: The public key and extracted request are PEM blocks, which other tools can extract.

If another object inherits from Crypt::PKCS10, it can extend the representation by overloading or calling as_string.

{class} method error

Returns a string describing the last error encountered;

If called as an instance method, last error encountered by the object.

If called as a class method, last error encountered by the class.

Any method can reset the string to undef, so the results are only valid immediately after a method call.

class method name2oid( $oid )

Returns the OID corresponding to a name returned by an access method.

Not in API v0;

csrRequest( $format )

Returns the binary (ASN.1) request (after conversion from PEM and removal of any data beyond the length of the ASN.1 structure.

If $format is true, the request is returned as a PEM CSR. Otherwise as a binary string.


Returns the binary (ASN.1) section of the request that is signed by the requestor.

The caller can verify the signature using signatureAlgorithm, certificationRequest and signature(1).

Access methods for the subject's distinguished name

Note that subjectAltName is prefered, and that modern certificate users will ignore the subject if subjectAltName is present.

subject( $format )

Returns the entire subject of the CSR.

In scalar context, returns the subject as a string in the form /componentName=value,value. If format is true, long component names are used. By default, abbreviations are used when they exist.

  e.g. /countryName=AU/organizationalUnitName=Big org/organizationalUnitName=Smaller org
  or     /C=AU/OU=Big org/OU=Smaller org

In array context, returns an array of (componentName, [values]) pairs. Abbreviations are not used.

Note that the order of components in a name is significant.


Returns the common name(s) from the subject.

    my $cn = $decoded->commonName();


Returns the organizational unit name(s) from the subject


Returns the organization name(s) from the subject.


Returns the email address from the subject.


Returns the state or province name(s) from the subject.


Returns the country name(s) from the subject.

subjectAltName( $type )

Convenience method.

When $type is specified: returns the subject alternate name values of the specified type in list context, or the first value of the specified type in scalar context.

Returns undefined/empty list if no values of the specified type are present, or if the subjectAltName extension is not present.

Types can be any of:

 * rfc822Name
 * dNSName
 * uniformResourceIdentifier
 * iPAddress
 * registeredID

The types marked with '*' are the most common.

If $type is not specified: In list context returns the types present in the subjectAlternate name. In scalar context, returns the SAN as a string.


Returns the structure version as a string, e.g. "v1" "v2", or "v3"


Returns the public key algorithm according to its object identifier.

subjectPublicKey( $format )

If $format is true, the public key will be returned in PEM format.

Otherwise, the public key will be returned in its hexadecimal representation


Returns a hash describing the public key. The contents vary depending on the public key type.

Standard items:

keytype - ECC, RSA, DSA or undef

keytype will be undef if the key type is not supported. In this case, error() returns a diagnostic message.

keylen - Approximate length of the key in bits.

Other items include:

For RSA, modulus and publicExponent.

For DSA, G, P and Q.

For ECC, curve, pub_x and pub_y. curve is an OID name.

Additional detail

subjectPublicKeyParams(1) returns the standard items, and may also return detail, which is a hashref.

For ECC, the detail hash includes the curve definition constants.


Returns the signature algorithm according to its object identifier.


Returns the parameters associated with the signatureAlgorithm as binary. Returns undef if none, or if NULL.

Note: In the future, some signatureAlgorithms may return a hashref of decoded fields.

Callers are advised to check for a ref before decoding...

signature( $format )

The CSR's signature is returned.

If $format is 1, in binary.

If $format is 2, decoded as an ECDSA signature - returns hashref to r and s.

Otherwise, in its hexadecimal representation.

attributes( $name )

A request may contain a set of attributes. The attributes are OIDs with values. The most common is a list of requested extensions, but other OIDs can also occur. Of those, challengePassword is typical.

For API version 0, this method returns a hash consisting of all attributes in an internal format. This usage is deprecated.

For API version 1:

If $name is not specified, a list of attribute names is returned. The list does not include the requestedExtensions attribute. For that, use extensions();

If no attributes are present, the empty list (undef in scalar context) is returned.

If $name is specified, the value of the extension is returned. $name can be specified as a numeric OID.

In scalar context, a single string is returned, which may include lists and labels.

  cspName="Microsoft Strong Cryptographic Provider",keySpec=2,signature=("",0)

Special characters are escaped as described in options.

In array context, the value(s) are returned as a list of items, which may be references.

 print( " $_: ", scalar $decoded->attributes($_), "\n" )
                                   foreach ($decoded->attributes);

See the Table of known OID names below for a list of names.


Returns an array containing the names of all extensions present in the CSR. If no extensions are present, the empty list is returned.

The names vary depending on the API version; however, the returned names are acceptable to extensionValue, extensionPresent, and name2oid.

The values of extensions vary, however the following code fragment will dump most extensions and their value(s).

 print( "$_: ", $decoded->extensionValue($_,1), "\n" ) foreach ($decoded->extensions);

The sample code fragment is not guaranteed to handle all cases. Production code needs to select the extensions that it understands and should respect the critical boolean. critical can be obtained with extensionPresent.

extensionValue( $name, $format )

Returns the value of an extension by name, e.g. extensionValue( 'keyUsage' ). The name SHOULD be an API v1 name, but API v0 names are accepted for compatibility. The name can also be specified as a numeric OID.

If $format is 1, the value is a formatted string, which may include lists and labels. Special characters are escaped as described in options;

If $format is 0 or not defined, a string, or an array reference may be returned. The array many contain any Perl variable type.

To interpret the value(s), you need to know the structure of the OID.

See the Table of known OID names below for a list of names.

extensionPresent( $name )

Returns true if a named extension is present: If the extension is critical, returns 2. Otherwise, returns 1, indicating not critical, but present.

If the extension is not present, returns undef.

The name can also be specified as a numeric OID.

See the Table of known OID names below for a list of names.

registerOID( )

Class method.

Register a custom OID, or a public OID that has not been added to Crypt::PKCS10 yet.

The OID may be an extension identifier or an RDN component.

The oid is specified as a string in numeric form, e.g. ''

registerOID( $oid )

Returns true if the specified OID is registered, false otherwise.

registerOID( $oid, $longname, $shortname )

Registers the specified OID with the associated long name. This enables the OID to be translated to a name in output.

The long name should be Hungarian case (commonName), but this is not currently enforced.

Optionally, specify the short name used for extracting the subject. The short name should be upper-case (and will be upcased).

E.g. built-in are $oid => '', $longname => 'commonName', $shortname => 'CN'

To register a shortname for an existing OID without one, specify $longname as undef.

E.g. To register /E for emailAddress, use: Crypt::PKCS10->registerOID( '1.2.840.113549.1.9.1', undef, 'e' )

Generates an exception if any argument is not valid, or is in use.

Returns true otherwise.


Verifies the signature of a CSR. (Useful if new() specified verifySignature => 0.)

Returns true if the signature is OK.

Returns false if the signature is incorrect. error() returns the reason.

Returns undef if it was not possible to complete the verification process (e.g. a required Perl module could not be loaded or an unsupported key/signature type is present.)


CertificateTemplate returns the certificateTemplate attribute.

Equivalent to extensionValue( 'certificateTemplate' ), which is prefered.

Table of known OID names

The following OID names are known. They are used in returned strings and structures, and as names by methods such as extensionValue.

Unknown OIDs are returned in numeric form, or can be registered with registerOID.

 OID                        Name (API v1)              Old Name (API v0)
 -------------------------- -------------------------- ---------------------------
 0.9.2342.19200300.100.1.1  userID
 0.9.2342.19200300.100.1.25 domainComponent
 1.2.840.10040.4.1          dsa                        (DSA)
 1.2.840.10040.4.3          dsaWithSha1                (DSA with SHA1)
 1.2.840.10045.2.1          ecPublicKey
 1.2.840.10045.3.1.1        secp192r1
 1.2.840.10045.3.1.7        secp256r1
 1.2.840.10045.4.3.1        ecdsa-with-SHA224
 1.2.840.10045.4.3.2        ecdsa-with-SHA256
 1.2.840.10045.4.3.3        ecdsa-with-SHA384
 1.2.840.10045.4.3.4        ecdsa-with-SHA512
 1.2.840.113549.1.1.1       rsaEncryption              (RSA encryption)
 1.2.840.113549.1.1.2       md2WithRSAEncryption       (MD2 with RSA encryption)
 1.2.840.113549.1.1.3       md4WithRSAEncryption
 1.2.840.113549.1.1.4       md5WithRSAEncryption       (MD5 with RSA encryption)
 1.2.840.113549.1.1.5       sha1WithRSAEncryption      (SHA1 with RSA encryption)
 1.2.840.113549.1.1.6       rsaOAEPEncryptionSET
 1.2.840.113549.1.1.7       RSAES-OAEP
 1.2.840.113549.1.1.11      sha256WithRSAEncryption    (SHA-256 with RSA encryption)
 1.2.840.113549.1.1.12      sha384WithRSAEncryption
 1.2.840.113549.1.1.13      sha512WithRSAEncryption    (SHA-512 with RSA encryption)
 1.2.840.113549.1.1.14      sha224WithRSAEncryption
 1.2.840.113549.1.9.1       emailAddress
 1.2.840.113549.1.9.2       unstructuredName
 1.2.840.113549.1.9.7       challengePassword
 1.2.840.113549.1.9.14      extensionRequest
 1.2.840.113549.1.9.15      smimeCapabilities          (SMIMECapabilities)     CERT_EXTENSIONS     msCodeInd     msCodeCom     msCTLSign     msTimeStamping     msSGC     msEFS   msEFSRecovery     msWHQLCrypto     msNT5Crypto     msOEMWHQLCrypto     msEmbeddedNTCrypto     msRootListSigner    msQualifiedSubordination    msKeyRecovery    msDocumentSigning    msLifetimeSigning    msMobileDeviceSoftware       RENEWAL_CERTIFICATE     ENROLLMENT_NAME_VALUE_PAIR     ENROLLMENT_CSP_PROVIDER     OS_Version       certificateTemplateName     msSmartCardLogon       certificateTemplate      ApplicationCertPolicies      ClientInformation            keyPurposeKdc              (KDC Authentication)          CPS          userNotice          serverAuth          clientAuth          codeSigning          emailProtection          timeStamping          OCSPSigning         sshClient         sshServer          countryOfResidence              sha1WithRSAEncryption      (SHA1 with RSA signature)       brainpoolP160r1       brainpoolP160t1       brainpoolP192r1       brainpoolP192t1       brainpoolP224r1       brainpoolP224t1       brainpoolP256r1       brainpoolP256t1       brainpoolP320r1      brainpoolP320t1      brainpoolP384r1      brainpoolP384t1      brainpoolP512r1      brainpoolP512t1                sect163k1               sect163r2               sect283k1               sect283r1               sect233k1               sect233r1               secp224r1               secp384r1               secp521r1               sect409k1               sect409r1               sect571k1               sect571r1                    commonName                    surname                    (Surname)                    serialNumber                    countryName                    localityName                    stateOrProvinceName                    streetAddress                   organizationName                   organizationalUnitName                   title                      (Title)                   description                (Description)                   searchGuide                   businessCategory                   postalAddress                   postalCode                   postOfficeBox                   physicalDeliveryOfficeName                   telephoneNumber                   facsimileTelephoneNumber                   name                       (Name)                   givenName                   initials                   generationQualifier                   uniqueIdentifier                   dnQualifier                   houseIdentifier                   pseudonym                  subjectKeyIdentifier       (SubjectKeyIdentifier)                  keyUsage                   (KeyUsage)                  subjectAltName                  basicConstraints           (Basic Constraints)                  certificatePolicies                anyPolicy                  extKeyUsage                (EnhancedKeyUsage)
 2.16.840.     sha256                     (SHA-256)
 2.16.840.     sha384                     (SHA-384)
 2.16.840.     sha512                     (SHA-512)
 2.16.840.     sha224                     (SHA-224)
 2.16.840.     dsaWithSha224
 2.16.840.     dsaWithSha256
 2.16.840.     dsaWithSha384
 2.16.840.     dsaWithSha512
 2.16.840.1.113730.1.1      netscapeCertType
 2.16.840.1.113730.1.2      netscapeBaseUrl
 2.16.840.1.113730.1.4      netscapeCaRevocationUrl
 2.16.840.1.113730.1.7      netscapeCertRenewalUrl
 2.16.840.1.113730.1.8      netscapeCaPolicyUrl
 2.16.840.1.113730.1.12     netscapeSSLServerName
 2.16.840.1.113730.1.13     netscapeComment
 2.16.840.1.113730.4.1      nsSGC


In addition to the code snippets contained in this document, the examples/ directory of the distribution contains some sample utilitiles.

Also, the t/ directory of the distribution contains a number of tests that exercise the API. Although artificial, they are another good source of examples.

Note that the type of data returned when extracting attributes and extensions is dependent on the specific OID used.

Also note that some functions not listed in this document are tested. The fact that they are tested does not imply that they are stable, or that they will be present in any future release.

The test data was selected to exercise the API; the CSR contents are not representative of realistic certificate requests.


Martin Bartosch contributed preliminary EC support: OIDs and tests.

Timothe Litt made most of the changes for V1.4+

Crypt::PKCS10 is based on the generic ASN.1 module by Graham Barr and on the x509decode example by Norbert Klasen. It is also based upon the works of Duncan Segrest's Crypt-X509-CRL module.


  • Gideon Knocke <>

  • Timothe Litt <>


This software is copyright (c) 2014, 2016 by Gideon Knocke, Timothe Litt.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.


Please report any bugs or feature requests on the bugtracker website or by email to

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.