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X.509 Reference

.. currentmodule:: cryptography.x509

.. testsetup::

    pem_crl_data = b"""
    -----BEGIN X509 CRL-----
    MIIBtDCBnQIBAjANBgkqhkiG9w0BAQsFADAnMQswCQYDVQQGEwJVUzEYMBYGA1UE
    AwwPY3J5cHRvZ3JhcGh5LmlvGA8yMDE1MDEwMTAwMDAwMFoYDzIwMTYwMTAxMDAw
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    X4B9vUQNXqc=
    -----END X509 CRL-----
    """.strip()

    pem_req_data = b"""
    -----BEGIN CERTIFICATE REQUEST-----
    MIIC0zCCAbsCAQAwWTELMAkGA1UEBhMCVVMxETAPBgNVBAgMCElsbGlub2lzMRAw
    DgYDVQQHDAdDaGljYWdvMREwDwYDVQQKDAhyNTA5IExMQzESMBAGA1UEAwwJaGVs
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    5wFkeYsZEA==
    -----END CERTIFICATE REQUEST-----
    """.strip()

    pem_data = b"""
    -----BEGIN CERTIFICATE-----
    MIIDfDCCAmSgAwIBAgIBAjANBgkqhkiG9w0BAQsFADBFMQswCQYDVQQGEwJVUzEf
    MB0GA1UEChMWVGVzdCBDZXJ0aWZpY2F0ZXMgMjAxMTEVMBMGA1UEAxMMVHJ1c3Qg
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    QYw2jOvpKcKtWCSAnegEbgsGYzATKjmPJPJ0npHFqzM=
    -----END CERTIFICATE-----
    """.strip()

    cryptography_cert_pem = b"""
    -----BEGIN CERTIFICATE-----
    MIIFvTCCBKWgAwIBAgICPyAwDQYJKoZIhvcNAQELBQAwRzELMAkGA1UEBhMCVVMx
    FjAUBgNVBAoTDUdlb1RydXN0IEluYy4xIDAeBgNVBAMTF1JhcGlkU1NMIFNIQTI1
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    GVI9+0lAFwxOUnOnwsoI40iOoxjLMGB+CgFLKCGUcWxP
    -----END CERTIFICATE-----
    """.strip()

    pem_issuer_public_key = b"""
    -----BEGIN RSA PUBLIC KEY-----
    MIICCgKCAgEAyYcqyuT6oQxpvg/VSn2Zc68wZ823D0VAJ2woramFx+2KPWB7B7Ot
    tVSNRfm0OxJOU3TFAoep54Z2wgOoz0zRmeW6/7gvIuBKp2TW0qZAt3l9sgpE29iw
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    0ZJJb5DXNbiTnspKLNmBt0YlNiXtlCIPxVUkhL141FuCLc8h6FjD6E0CAwEAAQ==
    -----END RSA PUBLIC KEY-----
    """.strip()

    pem_data_to_check = b"""
    -----BEGIN CERTIFICATE-----
    MIIErjCCApagAwIBAgIUUrUZsZrrBmRD2hvRuspp+lPsZXcwDQYJKoZIhvcNAQEN
    BQAwETEPMA0GA1UEAwwGSXNzdWVyMB4XDTE4MTAwODEzNDg1NFoXDTE4MTAxODEz
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    Nh4=
    -----END CERTIFICATE-----
    """.strip()

Loading Certificates

.. function:: load_pem_x509_certificate(data, backend)

    .. versionadded:: 0.7

    Deserialize a certificate from PEM encoded data. PEM certificates are
    base64 decoded and have delimiters that look like
    ``-----BEGIN CERTIFICATE-----``.

    :param bytes data: The PEM encoded certificate data.

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: An instance of :class:`~cryptography.x509.Certificate`.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> cert = x509.load_pem_x509_certificate(pem_data, default_backend())
        >>> cert.serial_number
        2

.. function:: load_der_x509_certificate(data, backend)

    .. versionadded:: 0.7

    Deserialize a certificate from DER encoded data. DER is a binary format
    and is commonly found in files with the ``.cer`` extension (although file
    extensions are not a guarantee of encoding type).

    :param bytes data: The DER encoded certificate data.

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: An instance of :class:`~cryptography.x509.Certificate`.

Loading Certificate Revocation Lists

.. function:: load_pem_x509_crl(data, backend)

    .. versionadded:: 1.1

    Deserialize a certificate revocation list (CRL) from PEM encoded data. PEM
    requests are base64 decoded and have delimiters that look like
    ``-----BEGIN X509 CRL-----``.

    :param bytes data: The PEM encoded request data.

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: An instance of
        :class:`~cryptography.x509.CertificateRevocationList`.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> from cryptography.hazmat.primitives import hashes
        >>> crl = x509.load_pem_x509_crl(pem_crl_data, default_backend())
        >>> isinstance(crl.signature_hash_algorithm, hashes.SHA256)
        True

.. function:: load_der_x509_crl(data, backend)

    .. versionadded:: 1.1

    Deserialize a certificate revocation list (CRL) from DER encoded data. DER
    is a binary format.

    :param bytes data: The DER encoded request data.

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: An instance of
        :class:`~cryptography.x509.CertificateRevocationList`.

Loading Certificate Signing Requests

.. function:: load_pem_x509_csr(data, backend)

    .. versionadded:: 0.9

    Deserialize a certificate signing request (CSR) from PEM encoded data. PEM
    requests are base64 decoded and have delimiters that look like
    ``-----BEGIN CERTIFICATE REQUEST-----``. This format is also known as
    PKCS#10.

    :param bytes data: The PEM encoded request data.

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: An instance of
        :class:`~cryptography.x509.CertificateSigningRequest`.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> from cryptography.hazmat.primitives import hashes
        >>> csr = x509.load_pem_x509_csr(pem_req_data, default_backend())
        >>> isinstance(csr.signature_hash_algorithm, hashes.SHA1)
        True

.. function:: load_der_x509_csr(data, backend)

    .. versionadded:: 0.9

    Deserialize a certificate signing request (CSR) from DER encoded data. DER
    is a binary format and is not commonly used with CSRs.

    :param bytes data: The DER encoded request data.

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: An instance of
        :class:`~cryptography.x509.CertificateSigningRequest`.

X.509 Certificate Object

.. versionadded:: 0.7

.. attribute:: version

    :type: :class:`~cryptography.x509.Version`

    The certificate version as an enumeration. Version 3 certificates are
    the latest version and also the only type you should see in practice.

    :raises cryptography.x509.InvalidVersion: If the version in the
        certificate is not a known
        :class:`X.509 version <cryptography.x509.Version>`.

    .. doctest::

        >>> cert.version
        <Version.v3: 2>

.. method:: fingerprint(algorithm)

    :param algorithm: The
        :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`
        that will be used to generate the fingerprint.

    :return bytes: The fingerprint using the supplied hash algorithm, as
        bytes.

    .. doctest::

        >>> from cryptography.hazmat.primitives import hashes
        >>> cert.fingerprint(hashes.SHA256())
        b'\x86\xd2\x187Gc\xfc\xe7}[+E9\x8d\xb4\x8f\x10\xe5S\xda\x18u\xbe}a\x03\x08[\xac\xa04?'

.. attribute:: serial_number

    :type: int

    The serial as a Python integer.

    .. doctest::

        >>> cert.serial_number
        2

.. method:: public_key()

    The public key associated with the certificate.

    :returns:
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`

    .. doctest::

        >>> from cryptography.hazmat.primitives.asymmetric import rsa
        >>> public_key = cert.public_key()
        >>> isinstance(public_key, rsa.RSAPublicKey)
        True

.. attribute:: not_valid_before

    :type: :class:`datetime.datetime`

    A naïve datetime representing the beginning of the validity period for
    the certificate in UTC. This value is inclusive.

    .. doctest::

        >>> cert.not_valid_before
        datetime.datetime(2010, 1, 1, 8, 30)

.. attribute:: not_valid_after

    :type: :class:`datetime.datetime`

    A naïve datetime representing the end of the validity period for the
    certificate in UTC. This value is inclusive.

    .. doctest::

        >>> cert.not_valid_after
        datetime.datetime(2030, 12, 31, 8, 30)

.. attribute:: issuer

    .. versionadded:: 0.8

    :type: :class:`Name`

    The :class:`Name` of the issuer.

.. attribute:: subject

    .. versionadded:: 0.8

    :type: :class:`Name`

    The :class:`Name` of the subject.

.. attribute:: signature_hash_algorithm

    :type: :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`

    Returns the
    :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm` which
    was used in signing this certificate.

    .. doctest::

        >>> from cryptography.hazmat.primitives import hashes
        >>> isinstance(cert.signature_hash_algorithm, hashes.SHA256)
        True

.. attribute:: signature_algorithm_oid

    .. versionadded:: 1.6

    :type: :class:`ObjectIdentifier`

    Returns the :class:`ObjectIdentifier` of the signature algorithm used
    to sign the certificate. This will be one of the OIDs from
    :class:`~cryptography.x509.oid.SignatureAlgorithmOID`.


    .. doctest::

        >>> cert.signature_algorithm_oid
        <ObjectIdentifier(oid=1.2.840.113549.1.1.11, name=sha256WithRSAEncryption)>

.. attribute:: extensions

    :type: :class:`Extensions`

    The extensions encoded in the certificate.

    :raises cryptography.x509.DuplicateExtension: If more than one
        extension of the same type is found within the certificate.

    :raises cryptography.x509.UnsupportedGeneralNameType: If an extension
        contains a general name that is not supported.

    :raises UnicodeError: If an extension contains IDNA encoding that is
        invalid or not compliant with IDNA 2008.

    .. doctest::

        >>> for ext in cert.extensions:
        ...     print(ext)
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.35, name=authorityKeyIdentifier)>, critical=False, value=<AuthorityKeyIdentifier(key_identifier=b'\xe4}_\xd1\\\x95\x86\x08,\x05\xae\xbeu\xb6e\xa7\xd9]\xa8f', authority_cert_issuer=None, authority_cert_serial_number=None)>)>
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.14, name=subjectKeyIdentifier)>, critical=False, value=<SubjectKeyIdentifier(digest=b'X\x01\x84$\x1b\xbc+R\x94J=\xa5\x10r\x14Q\xf5\xaf:\xc9')>)>
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.15, name=keyUsage)>, critical=True, value=<KeyUsage(digital_signature=False, content_commitment=False, key_encipherment=False, data_encipherment=False, key_agreement=False, key_cert_sign=True, crl_sign=True, encipher_only=None, decipher_only=None)>)>
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.32, name=certificatePolicies)>, critical=False, value=<CertificatePolicies([<PolicyInformation(policy_identifier=<ObjectIdentifier(oid=2.16.840.1.101.3.2.1.48.1, name=Unknown OID)>, policy_qualifiers=None)>])>)>
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.19, name=basicConstraints)>, critical=True, value=<BasicConstraints(ca=True, path_length=None)>)>

.. attribute:: signature

    .. versionadded:: 1.2

    :type: bytes

    The bytes of the certificate's signature.

.. attribute:: tbs_certificate_bytes

    .. versionadded:: 1.2

    :type: bytes

    The DER encoded bytes payload (as defined by :rfc:`5280`) that is hashed
    and then signed by the private key of the certificate's issuer. This
    data may be used to validate a signature, but use extreme caution as
    certificate validation is a complex problem that involves much more
    than just signature checks.

    To validate the signature on a certificate you can do the following.
    Note: This only verifies that the certificate was signed with the
    private key associated with the public key provided and does not
    perform any of the other checks needed for secure certificate
    validation. Additionally, this example will only work for RSA public
    keys with ``PKCS1v15`` signatures, and so it can't be used for general
    purpose signature verification.

    .. doctest::

       >>> from cryptography.hazmat.primitives.serialization import load_pem_public_key
       >>> from cryptography.hazmat.primitives.asymmetric import padding
       >>> issuer_public_key = load_pem_public_key(pem_issuer_public_key, default_backend())
       >>> cert_to_check = x509.load_pem_x509_certificate(pem_data_to_check, default_backend())
       >>> issuer_public_key.verify(
       ...     cert_to_check.signature,
       ...     cert_to_check.tbs_certificate_bytes,
       ...     # Depends on the algorithm used to create the certificate
       ...     padding.PKCS1v15(),
       ...     cert_to_check.signature_hash_algorithm,
       ... )

       An
       :class:`~cryptography.exceptions.InvalidSignature`
       exception will be raised if the signature fails to verify.

.. method:: public_bytes(encoding)

    .. versionadded:: 1.0

    :param encoding: The
        :class:`~cryptography.hazmat.primitives.serialization.Encoding`
        that will be used to serialize the certificate.

    :return bytes: The data that can be written to a file or sent
        over the network to be verified by clients.

X.509 CRL (Certificate Revocation List) Object

.. versionadded:: 1.0

A CertificateRevocationList is an object representing a list of revoked certificates. The object is iterable and will yield the RevokedCertificate objects stored in this CRL.

>>> len(crl)
1
>>> revoked_certificate = crl[0]
>>> type(revoked_certificate)
<class 'cryptography.hazmat.backends.openssl.x509._RevokedCertificate'>
>>> for r in crl:
...     print(r.serial_number)
0
.. method:: fingerprint(algorithm)

    :param algorithm: The
        :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`
        that will be used to generate the fingerprint.

    :return bytes: The fingerprint using the supplied hash algorithm, as
        bytes.

    .. doctest::

        >>> from cryptography.hazmat.primitives import hashes
        >>> crl.fingerprint(hashes.SHA256())
        b'e\xcf.\xc4:\x83?1\xdc\xf3\xfc\x95\xd7\xb3\x87\xb3\x8e\xf8\xb93!\x87\x07\x9d\x1b\xb4!\xb9\xe4W\xf4\x1f'

.. method:: get_revoked_certificate_by_serial_number(serial_number)

    .. versionadded:: 2.3

    :param serial_number: The serial as a Python integer.
    :returns: :class:`~cryptography.x509.RevokedCertificate` if the
        ``serial_number`` is present in the CRL or ``None`` if it
        is not.

.. attribute:: signature_hash_algorithm

    :type: :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`

    Returns the
    :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm` which
    was used in signing this CRL.

    .. doctest::

        >>> from cryptography.hazmat.primitives import hashes
        >>> isinstance(crl.signature_hash_algorithm, hashes.SHA256)
        True

.. attribute:: signature_algorithm_oid

    .. versionadded:: 1.6

    :type: :class:`ObjectIdentifier`

    Returns the :class:`ObjectIdentifier` of the signature algorithm used
    to sign the CRL. This will be one of the OIDs from
    :class:`~cryptography.x509.oid.SignatureAlgorithmOID`.

    .. doctest::

        >>> crl.signature_algorithm_oid
        <ObjectIdentifier(oid=1.2.840.113549.1.1.11, name=sha256WithRSAEncryption)>

.. attribute:: issuer

    :type: :class:`Name`

    The :class:`Name` of the issuer.

    .. doctest::

        >>> crl.issuer
        <Name(C=US, CN=cryptography.io)>

.. attribute:: next_update

    :type: :class:`datetime.datetime`

    A naïve datetime representing when the next update to this CRL is
    expected.

    .. doctest::

        >>> crl.next_update
        datetime.datetime(2016, 1, 1, 0, 0)

.. attribute:: last_update

    :type: :class:`datetime.datetime`

    A naïve datetime representing when the this CRL was last updated.

    .. doctest::

        >>> crl.last_update
        datetime.datetime(2015, 1, 1, 0, 0)

.. attribute:: extensions

    :type: :class:`Extensions`

    The extensions encoded in the CRL.

.. attribute:: signature

    .. versionadded:: 1.2

    :type: bytes

    The bytes of the CRL's signature.

.. attribute:: tbs_certlist_bytes

    .. versionadded:: 1.2

    :type: bytes

    The DER encoded bytes payload (as defined by :rfc:`5280`) that is hashed
    and then signed by the private key of the CRL's issuer. This data may be
    used to validate a signature, but use extreme caution as CRL validation
    is a complex problem that involves much more than just signature checks.

.. method:: public_bytes(encoding)

    .. versionadded:: 1.2

    :param encoding: The
        :class:`~cryptography.hazmat.primitives.serialization.Encoding`
        that will be used to serialize the certificate revocation list.

    :return bytes: The data that can be written to a file or sent
        over the network and used as part of a certificate verification
        process.

.. method:: is_signature_valid(public_key)

    .. versionadded:: 2.1

    .. warning::

        Checking the validity of the signature on the CRL is insufficient
        to know if the CRL should be trusted. More details are available
        in :rfc:`5280`.

    Returns True if the CRL signature is correct for given public key,
    False otherwise.

X.509 Certificate Builder

.. versionadded:: 1.0

>>> from cryptography import x509
>>> from cryptography.hazmat.backends import default_backend
>>> from cryptography.hazmat.primitives import hashes
>>> from cryptography.hazmat.primitives.asymmetric import rsa
>>> from cryptography.x509.oid import NameOID
>>> import datetime
>>> one_day = datetime.timedelta(1, 0, 0)
>>> private_key = rsa.generate_private_key(
...     public_exponent=65537,
...     key_size=2048,
...     backend=default_backend()
... )
>>> public_key = private_key.public_key()
>>> builder = x509.CertificateBuilder()
>>> builder = builder.subject_name(x509.Name([
...     x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
... ]))
>>> builder = builder.issuer_name(x509.Name([
...     x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
... ]))
>>> builder = builder.not_valid_before(datetime.datetime.today() - one_day)
>>> builder = builder.not_valid_after(datetime.datetime.today() + (one_day * 30))
>>> builder = builder.serial_number(x509.random_serial_number())
>>> builder = builder.public_key(public_key)
>>> builder = builder.add_extension(
...     x509.SubjectAlternativeName(
...         [x509.DNSName(u'cryptography.io')]
...     ),
...     critical=False
... )
>>> builder = builder.add_extension(
...     x509.BasicConstraints(ca=False, path_length=None), critical=True,
... )
>>> certificate = builder.sign(
...     private_key=private_key, algorithm=hashes.SHA256(),
...     backend=default_backend()
... )
>>> isinstance(certificate, x509.Certificate)
True
.. method:: issuer_name(name)

    Sets the issuer's distinguished name.

    :param name: The :class:`~cryptography.x509.Name` that describes the
        issuer (CA).

.. method:: subject_name(name)

    Sets the subject's distinguished name.

    :param name: The :class:`~cryptography.x509.Name` that describes the
        subject.

.. method:: public_key(public_key)

    Sets the subject's public key.

    :param public_key: The subject's public key. This can be one of
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey`,
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`

.. method:: serial_number(serial_number)

    Sets the certificate's serial number (an integer).  The CA's policy
    determines how it attributes serial numbers to certificates. This
    number must uniquely identify the certificate given the issuer.
    `CABForum Guidelines`_ require entropy in the serial number
    to provide protection against hash collision attacks. For more
    information on secure random number generation, see
    :doc:`/random-numbers`.

    :param serial_number: Integer number that will be used by the CA to
        identify this certificate (most notably during certificate
        revocation checking). Users should consider using
        :func:`~cryptography.x509.random_serial_number` when possible.

.. method:: not_valid_before(time)

    Sets the certificate's activation time.  This is the time from which
    clients can start trusting the certificate.  It may be different from
    the time at which the certificate was created.

    :param time: The :class:`datetime.datetime` object (in UTC) that marks the
        activation time for the certificate.  The certificate may not be
        trusted clients if it is used before this time.

.. method:: not_valid_after(time)

    Sets the certificate's expiration time.  This is the time from which
    clients should no longer trust the certificate.  The CA's policy will
    determine how long the certificate should remain in use.

    :param time: The :class:`datetime.datetime` object (in UTC) that marks the
        expiration time for the certificate.  The certificate may not be
        trusted clients if it is used after this time.

.. method:: add_extension(extension, critical)

    Adds an X.509 extension to the certificate.

    :param extension: An extension conforming to the
        :class:`~cryptography.x509.ExtensionType` interface.

    :param critical: Set to ``True`` if the extension must be understood and
         handled by whoever reads the certificate.

.. method:: sign(private_key, algorithm, backend)

    Sign the certificate using the CA's private key.

    :param private_key: The
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey`,
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey`
        that will be used to sign the certificate.

    :param algorithm: The
        :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm` that
        will be used to generate the signature.

    :param backend: Backend that will be used to build the certificate.
        Must support the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: :class:`~cryptography.x509.Certificate`

X.509 CSR (Certificate Signing Request) Object

.. versionadded:: 0.9

.. method:: public_key()

    The public key associated with the request.

    :returns:
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`

    .. doctest::

        >>> from cryptography.hazmat.primitives.asymmetric import rsa
        >>> public_key = csr.public_key()
        >>> isinstance(public_key, rsa.RSAPublicKey)
        True

.. attribute:: subject

    :type: :class:`Name`

    The :class:`Name` of the subject.

.. attribute:: signature_hash_algorithm

    :type: :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`

    Returns the
    :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm` which
    was used in signing this request.

    .. doctest::

        >>> from cryptography.hazmat.primitives import hashes
        >>> isinstance(csr.signature_hash_algorithm, hashes.SHA1)
        True

.. attribute:: signature_algorithm_oid

    .. versionadded:: 1.6

    :type: :class:`ObjectIdentifier`

    Returns the :class:`ObjectIdentifier` of the signature algorithm used
    to sign the request. This will be one of the OIDs from
    :class:`~cryptography.x509.oid.SignatureAlgorithmOID`.

    .. doctest::

        >>> csr.signature_algorithm_oid
        <ObjectIdentifier(oid=1.2.840.113549.1.1.5, name=sha1WithRSAEncryption)>

.. attribute:: extensions

    :type: :class:`Extensions`

    The extensions encoded in the certificate signing request.

    :raises cryptography.x509.DuplicateExtension: If more than one
        extension of the same type is found within the certificate signing request.

    :raises cryptography.x509.UnsupportedGeneralNameType: If an extension
        contains a general name that is not supported.

    :raises UnicodeError: If an extension contains IDNA encoding that is
        invalid or not compliant with IDNA 2008.


.. method:: public_bytes(encoding)

    .. versionadded:: 1.0

    :param encoding: The
        :class:`~cryptography.hazmat.primitives.serialization.Encoding`
        that will be used to serialize the certificate request.

    :return bytes: The data that can be written to a file or sent
        over the network to be signed by the certificate
        authority.

.. attribute:: signature

    .. versionadded:: 1.2

    :type: bytes

    The bytes of the certificate signing request's signature.

.. attribute:: tbs_certrequest_bytes

    .. versionadded:: 1.2

    :type: bytes

    The DER encoded bytes payload (as defined by :rfc:`2986`) that is
    hashed and then signed by the private key (corresponding to the public
    key embedded in the CSR). This data may be used to validate the CSR
    signature.

.. attribute:: is_signature_valid

    .. versionadded:: 1.3

    Returns True if the CSR signature is correct, False otherwise.

X.509 Certificate Revocation List Builder

.. versionadded:: 1.2

>>> from cryptography import x509
>>> from cryptography.hazmat.backends import default_backend
>>> from cryptography.hazmat.primitives import hashes
>>> from cryptography.hazmat.primitives.asymmetric import rsa
>>> from cryptography.x509.oid import NameOID
>>> import datetime
>>> one_day = datetime.timedelta(1, 0, 0)
>>> private_key = rsa.generate_private_key(
...     public_exponent=65537,
...     key_size=2048,
...     backend=default_backend()
... )
>>> builder = x509.CertificateRevocationListBuilder()
>>> builder = builder.issuer_name(x509.Name([
...     x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io CA'),
... ]))
>>> builder = builder.last_update(datetime.datetime.today())
>>> builder = builder.next_update(datetime.datetime.today() + one_day)
>>> revoked_cert = x509.RevokedCertificateBuilder().serial_number(
...     333
... ).revocation_date(
...     datetime.datetime.today()
... ).build(default_backend())
>>> builder = builder.add_revoked_certificate(revoked_cert)
>>> crl = builder.sign(
...     private_key=private_key, algorithm=hashes.SHA256(),
...     backend=default_backend()
... )
>>> len(crl)
1
.. method:: issuer_name(name)

    Sets the issuer's distinguished name.

    :param name: The :class:`~cryptography.x509.Name` that describes the
        issuer (CA).

.. method:: last_update(time)

    Sets this CRL's activation time.  This is the time from which
    clients can start trusting this CRL.  It may be different from
    the time at which this CRL was created. This is also known as the
    ``thisUpdate`` time.

    :param time: The :class:`datetime.datetime` object (in UTC) that marks
        the activation time for this CRL.  The CRL may not be trusted if it
        is used before this time.

.. method:: next_update(time)

    Sets this CRL's next update time. This is the time by which
    a new CRL will be issued. The CA is allowed to issue a new CRL before
    this date, however clients are not required to check for it.

    :param time: The :class:`datetime.datetime` object (in UTC) that marks
        the next update time for this CRL.

.. method:: add_extension(extension, critical)

    Adds an X.509 extension to this CRL.

    :param extension: An extension with the
        :class:`~cryptography.x509.ExtensionType` interface.

    :param critical: Set to ``True`` if the extension must be understood and
         handled by whoever reads the CRL.

.. method:: add_revoked_certificate(revoked_certificate)

    Adds a revoked certificate to this CRL.

    :param revoked_certificate: An instance of
        :class:`~cryptography.x509.RevokedCertificate`. These can be
        obtained from an existing CRL or created with
        :class:`~cryptography.x509.RevokedCertificateBuilder`.

.. method:: sign(private_key, algorithm, backend)

    Sign this CRL using the CA's private key.

    :param private_key: The
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey`,
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey`
        that will be used to sign the certificate.

    :param algorithm: The
        :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm` that
        will be used to generate the signature.

    :param backend: Backend that will be used to build the CRL.
        Must support the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: :class:`~cryptography.x509.CertificateRevocationList`

X.509 Revoked Certificate Object

.. versionadded:: 1.0

.. attribute:: serial_number

    :type: :class:`int`

    An integer representing the serial number of the revoked certificate.

    .. doctest::

        >>> revoked_certificate.serial_number
        0

.. attribute:: revocation_date

    :type: :class:`datetime.datetime`

    A naïve datetime representing the date this certificates was revoked.

    .. doctest::

        >>> revoked_certificate.revocation_date
        datetime.datetime(2015, 1, 1, 0, 0)

.. attribute:: extensions

    :type: :class:`Extensions`

    The extensions encoded in the revoked certificate.

    .. doctest::

        >>> for ext in revoked_certificate.extensions:
        ...     print(ext)
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.24, name=invalidityDate)>, critical=False, value=<InvalidityDate(invalidity_date=2015-01-01 00:00:00)>)>
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.21, name=cRLReason)>, critical=False, value=<CRLReason(reason=ReasonFlags.key_compromise)>)>

X.509 Revoked Certificate Builder

This class is used to create :class:`~cryptography.x509.RevokedCertificate` objects that can be used with the :class:`~cryptography.x509.CertificateRevocationListBuilder`.

.. versionadded:: 1.2

>>> from cryptography import x509
>>> from cryptography.hazmat.backends import default_backend
>>> import datetime
>>> builder = x509.RevokedCertificateBuilder()
>>> builder = builder.revocation_date(datetime.datetime.today())
>>> builder = builder.serial_number(3333)
>>> revoked_certificate = builder.build(default_backend())
>>> isinstance(revoked_certificate, x509.RevokedCertificate)
True
.. method:: serial_number(serial_number)

    Sets the revoked certificate's serial number.

    :param serial_number: Integer number that is used to identify the
        revoked certificate.

.. method:: revocation_date(time)

    Sets the certificate's revocation date.

    :param time: The :class:`datetime.datetime` object (in UTC) that marks the
        revocation time for the certificate.

.. method:: add_extension(extension, critical)

    Adds an X.509 extension to this revoked certificate.

    :param extension: An instance of one of the
        :ref:`CRL entry extensions <crl_entry_extensions>`.

    :param critical: Set to ``True`` if the extension must be understood and
         handled.

.. method:: build(backend)

    Create a revoked certificate object using the provided backend.

    :param backend: Backend that will be used to build the revoked
        certificate.  Must support the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :returns: :class:`~cryptography.x509.RevokedCertificate`

X.509 CSR (Certificate Signing Request) Builder Object

.. versionadded:: 1.0

>>> from cryptography import x509
>>> from cryptography.hazmat.backends import default_backend
>>> from cryptography.hazmat.primitives import hashes
>>> from cryptography.hazmat.primitives.asymmetric import rsa
>>> from cryptography.x509.oid import NameOID
>>> private_key = rsa.generate_private_key(
...     public_exponent=65537,
...     key_size=2048,
...     backend=default_backend()
... )
>>> builder = x509.CertificateSigningRequestBuilder()
>>> builder = builder.subject_name(x509.Name([
...     x509.NameAttribute(NameOID.COMMON_NAME, u'cryptography.io'),
... ]))
>>> builder = builder.add_extension(
...     x509.BasicConstraints(ca=False, path_length=None), critical=True,
... )
>>> request = builder.sign(
...     private_key, hashes.SHA256(), default_backend()
... )
>>> isinstance(request, x509.CertificateSigningRequest)
True
.. method:: subject_name(name)

    :param name: The :class:`~cryptography.x509.Name` of the certificate
        subject.
    :returns: A new
        :class:`~cryptography.x509.CertificateSigningRequestBuilder`.

.. method:: add_extension(extension, critical)

    :param extension: An extension conforming to the
        :class:`~cryptography.x509.ExtensionType` interface.
    :param critical: Set to `True` if the extension must be understood and
         handled by whoever reads the certificate.
    :returns: A new
        :class:`~cryptography.x509.CertificateSigningRequestBuilder`.

.. method:: sign(private_key, algorithm, backend)

    :param backend: Backend that will be used to sign the request.
        Must support the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :param private_key: The
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey`,
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPrivateKey` or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePrivateKey`
        that will be used to sign the request.  When the request is
        signed by a certificate authority, the private key's associated
        public key will be stored in the resulting certificate.

    :param algorithm: The
        :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`
        that will be used to generate the request signature.

    :returns: A new
        :class:`~cryptography.x509.CertificateSigningRequest`.
.. versionadded:: 0.8

An X509 Name is an ordered list of attributes. The object is iterable to get every attribute or you can use :meth:`Name.get_attributes_for_oid` to obtain the specific type you want. Names are sometimes represented as a slash or comma delimited string (e.g. /CN=mydomain.com/O=My Org/C=US or CN=mydomain.com, O=My Org, C=US).

Technically, a Name is a list of sets of attributes, called Relative Distinguished Names or RDNs, although multi-valued RDNs are rarely encountered. The iteration order of values within a multi-valued RDN is preserved. If you need to handle multi-valued RDNs, the rdns property gives access to an ordered list of :class:`RelativeDistinguishedName` objects.

A Name can be initialized with an iterable of :class:`NameAttribute` (the common case where each RDN has a single attribute) or an iterable of :class:`RelativeDistinguishedName` objects (in the rare case of multi-valued RDNs).

>>> len(cert.subject)
3
>>> for attribute in cert.subject:
...     print(attribute)
<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.6, name=countryName)>, value='US')>
<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.10, name=organizationName)>, value='Test Certificates 2011')>
<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.3, name=commonName)>, value='Good CA')>
.. attribute:: rdns

    .. versionadded:: 1.6

    :type: list of :class:`RelativeDistinguishedName`

.. method:: get_attributes_for_oid(oid)

    :param oid: An :class:`ObjectIdentifier` instance.

    :returns: A list of :class:`NameAttribute` instances that match the
        OID provided. If nothing matches an empty list will be returned.

    .. doctest::

        >>> cert.subject.get_attributes_for_oid(NameOID.COMMON_NAME)
        [<NameAttribute(oid=<ObjectIdentifier(oid=2.5.4.3, name=commonName)>, value='Good CA')>]

.. method:: public_bytes(backend)

    .. versionadded:: 1.6

    :param backend: A backend supporting the
        :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
        interface.

    :return bytes: The DER encoded name.

.. method:: rfc4514_string()

    .. versionadded:: 2.5

    :return str: Format the given name as a `RFC 4514`_ Distinguished Name
        string, for example ``CN=mydomain.com, O=My Org, C=US``.
.. versionadded:: 0.7

An enumeration for X.509 versions.

.. attribute:: v1

    For version 1 X.509 certificates.

.. attribute:: v3

    For version 3 X.509 certificates.
.. versionadded:: 0.8

An X.509 name consists of a list of :class:`RelativeDistinguishedName` instances, which consist of a set of :class:`NameAttribute` instances.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    The attribute OID.

.. attribute:: value

    :type: :term:`text`

    The value of the attribute.

.. method:: rfc4514_string()

    .. versionadded:: 2.5

    :return str: Format the given attribute as a `RFC 4514`_ Distinguished
        Name string.
.. versionadded:: 1.6

A relative distinguished name is a non-empty set of name attributes. The object is iterable to get every attribute, preserving the original order. Passing duplicate attributes to the constructor raises ValueError.

.. method:: get_attributes_for_oid(oid)

    :param oid: An :class:`ObjectIdentifier` instance.

    :returns: A list of :class:`NameAttribute` instances that match the OID
        provided.  The list should contain zero or one values.

.. method:: rfc4514_string()

    .. versionadded:: 2.5

    :return str: Format the given RDN set as a `RFC 4514`_ Distinguished
        Name string.
.. versionadded:: 0.8

Object identifiers (frequently seen abbreviated as OID) identify the type of a value (see: :class:`NameAttribute`).

.. attribute:: dotted_string

    :type: :class:`str`

    The dotted string value of the OID (e.g. ``"2.5.4.3"``)

General Name Classes

.. versionadded:: 0.9

This is the generic interface that all the following classes are registered against.

.. versionadded:: 0.9

.. versionchanged:: 2.1

Warning

Starting with version 2.1 :term:`U-label` input is deprecated. If passing an internationalized domain name (IDN) you should first IDNA encode the value and then pass the result as a string. Accessing value will return the :term:`A-label` encoded form even if you pass a U-label. This breaks backwards compatibility, but only for internationalized domain names.

This corresponds to an email address. For example, user@example.com.

param value:The email address. If the address contains an internationalized domain name then it must be encoded to an :term:`A-label` string before being passed.
.. attribute:: value

    :type: :term:`text`
.. versionadded:: 0.9

.. versionchanged:: 2.1

Warning

Starting with version 2.1 :term:`U-label` input is deprecated. If passing an internationalized domain name (IDN) you should first IDNA encode the value and then pass the result as a string. Accessing value will return the :term:`A-label` encoded form even if you pass a U-label. This breaks backwards compatibility, but only for internationalized domain names.

This corresponds to a domain name. For example, cryptography.io.

param value:

The domain name. If it is an internationalized domain name then it must be encoded to an :term:`A-label` string before being passed.

type::term:`text`
.. attribute:: value

    :type: :term:`text`
.. versionadded:: 0.9

This corresponds to a directory name.

.. attribute:: value

    :type: :class:`Name`
.. versionadded:: 0.9

.. versionchanged:: 2.1

Warning

Starting with version 2.1 :term:`U-label` input is deprecated. If passing an internationalized domain name (IDN) you should first IDNA encode the value and then pass the result as a string. Accessing value will return the :term:`A-label` encoded form even if you pass a U-label. This breaks backwards compatibility, but only for internationalized domain names.

This corresponds to a uniform resource identifier. For example, https://cryptography.io.

param value:The URI. If it contains an internationalized domain name then it must be encoded to an :term:`A-label` string before being passed.
.. attribute:: value

    :type: :term:`text`
.. versionadded:: 0.9

This corresponds to an IP address.

.. attribute:: value

    :type: :class:`~ipaddress.IPv4Address`,
        :class:`~ipaddress.IPv6Address`,  :class:`~ipaddress.IPv4Network`,
        or :class:`~ipaddress.IPv6Network`.
.. versionadded:: 0.9

This corresponds to a registered ID.

.. attribute:: value

    :type: :class:`ObjectIdentifier`
.. versionadded:: 1.0

This corresponds to an otherName. An otherName has a type identifier and a value represented in binary DER format.

.. attribute:: type_id

    :type: :class:`ObjectIdentifier`

.. attribute:: value

    :type: bytes

X.509 Extensions

.. versionadded:: 0.9

An X.509 Extensions instance is an ordered list of extensions. The object is iterable to get every extension.

.. method:: get_extension_for_oid(oid)

    :param oid: An :class:`ObjectIdentifier` instance.

    :returns: An instance of the extension class.

    :raises cryptography.x509.ExtensionNotFound: If the certificate does
        not have the extension requested.

    .. doctest::

        >>> from cryptography.x509.oid import ExtensionOID
        >>> cert.extensions.get_extension_for_oid(ExtensionOID.BASIC_CONSTRAINTS)
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.19, name=basicConstraints)>, critical=True, value=<BasicConstraints(ca=True, path_length=None)>)>

.. method:: get_extension_for_class(extclass)

    .. versionadded:: 1.1

    :param extclass: An extension class.

    :returns: An instance of the extension class.

    :raises cryptography.x509.ExtensionNotFound: If the certificate does
        not have the extension requested.

    .. doctest::

        >>> from cryptography import x509
        >>> cert.extensions.get_extension_for_class(x509.BasicConstraints)
        <Extension(oid=<ObjectIdentifier(oid=2.5.29.19, name=basicConstraints)>, critical=True, value=<BasicConstraints(ca=True, path_length=None)>)>
.. versionadded:: 0.9

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    One of the :class:`~cryptography.x509.oid.ExtensionOID` OIDs.

.. attribute:: critical

    :type: bool

    Determines whether a given extension is critical or not. :rfc:`5280`
    requires that "A certificate-using system MUST reject the certificate
    if it encounters a critical extension it does not recognize or a
    critical extension that contains information that it cannot process".

.. attribute:: value

    Returns an instance of the extension type corresponding to the OID.
.. versionadded:: 1.0

This is the interface against which all the following extension types are registered.

.. versionadded:: 0.9

The key usage extension defines the purpose of the key contained in the certificate. The usage restriction might be employed when a key that could be used for more than one operation is to be restricted.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.KEY_USAGE`.

.. attribute:: digital_signature

    :type: bool

    This purpose is set to true when the subject public key is used for verifying
    digital signatures, other than signatures on certificates
    (``key_cert_sign``) and CRLs (``crl_sign``).

.. attribute:: content_commitment

    :type: bool

    This purpose is set to true when the subject public key is used for verifying
    digital signatures, other than signatures on certificates
    (``key_cert_sign``) and CRLs (``crl_sign``). It is used to provide a
    non-repudiation service that protects against the signing entity
    falsely denying some action. In the case of later conflict, a
    reliable third party may determine the authenticity of the signed
    data. This was called ``non_repudiation`` in older revisions of the
    X.509 specification.

.. attribute:: key_encipherment

    :type: bool

    This purpose is set to true when the subject public key is used for
    enciphering private or secret keys.

.. attribute:: data_encipherment

    :type: bool

    This purpose is set to true when the subject public key is used for
    directly enciphering raw user data without the use of an intermediate
    symmetric cipher.

.. attribute:: key_agreement

    :type: bool

    This purpose is set to true when the subject public key is used for key
    agreement.  For example, when a Diffie-Hellman key is to be used for
    key management, then this purpose is set to true.

.. attribute:: key_cert_sign

    :type: bool

    This purpose is set to true when the subject public key is used for
    verifying signatures on public key certificates. If this purpose is set
    to true then ``ca`` must be true in the :class:`BasicConstraints`
    extension.

.. attribute:: crl_sign

    :type: bool

    This purpose is set to true when the subject public key is used for
    verifying signatures on certificate revocation lists.

.. attribute:: encipher_only

    :type: bool

    When this purposes is set to true and the ``key_agreement`` purpose is
    also set, the subject public key may be used only for enciphering data
    while performing key agreement.

    :raises ValueError: This is raised if accessed when ``key_agreement``
        is false.

.. attribute:: decipher_only

    :type: bool

    When this purposes is set to true and the ``key_agreement`` purpose is
    also set, the subject public key may be used only for deciphering data
    while performing key agreement.

    :raises ValueError: This is raised if accessed when ``key_agreement``
        is false.
.. versionadded:: 0.9

Basic constraints is an X.509 extension type that defines whether a given certificate is allowed to sign additional certificates and what path length restrictions may exist.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.BASIC_CONSTRAINTS`.

.. attribute:: ca

    :type: bool

    Whether the certificate can sign certificates.

.. attribute:: path_length

    :type: int or None

    The maximum path length for certificates subordinate to this
    certificate. This attribute only has meaning if ``ca`` is true.
    If ``ca`` is true then a path length of None means there's no
    restriction on the number of subordinate CAs in the certificate chain.
    If it is zero or greater then it defines the maximum length for a
    subordinate CA's certificate chain. For example, a ``path_length`` of 1
    means the certificate can sign a subordinate CA, but the subordinate CA
    is not allowed to create subordinates with ``ca`` set to true.
.. versionadded:: 0.9

This extension indicates one or more purposes for which the certified public key may be used, in addition to or in place of the basic purposes indicated in the key usage extension. The object is iterable to obtain the list of :class:`~cryptography.x509.oid.ExtendedKeyUsageOID` OIDs present.

param list usages:A list of :class:`~cryptography.x509.oid.ExtendedKeyUsageOID` OIDs.
.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.EXTENDED_KEY_USAGE`.
.. versionadded:: 1.0

This presence of this extension indicates that an OCSP client can trust a responder for the lifetime of the responder's certificate. CAs issuing such a certificate should realize that a compromise of the responder's key is as serious as the compromise of a CA key used to sign CRLs, at least for the validity period of this certificate. CA's may choose to issue this type of certificate with a very short lifetime and renew it frequently. This extension is only relevant when the certificate is an authorized OCSP responder.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.OCSP_NO_CHECK`.
.. versionadded:: 2.1

The TLS Feature extension is defined in RFC 7633 and is used in certificates for OCSP Must-Staple. The object is iterable to get every element.

param list features:A list of features to enable from the :class:`~cryptography.x509.TLSFeatureType` enum. At this time only status_request or status_request_v2 are allowed.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.TLS_FEATURE`.
.. versionadded:: 2.1

An enumeration of TLS Feature types.

.. attribute:: status_request

    This feature type is defined in :rfc:`6066` and, when embedded in
    an X.509 certificate, signals to the client that it should require
    a stapled OCSP response in the TLS handshake. Commonly known as OCSP
    Must-Staple in certificates.

.. attribute:: status_request_v2

    This feature type is defined in :rfc:`6961`. This value is not
    commonly used and if you want to enable OCSP Must-Staple you should
    use ``status_request``.
.. versionadded:: 1.0

The name constraints extension, which only has meaning in a CA certificate, defines a name space within which all subject names in certificates issued beneath the CA certificate must (or must not) be in. For specific details on the way this extension should be processed see RFC 5280.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.NAME_CONSTRAINTS`.

.. attribute:: permitted_subtrees

    :type: list of :class:`GeneralName` objects or None

    The set of permitted name patterns. If a name matches this and an
    element in ``excluded_subtrees`` it is invalid. At least one of
    ``permitted_subtrees`` and ``excluded_subtrees`` will be non-None.

.. attribute:: excluded_subtrees

    :type: list of :class:`GeneralName` objects or None

    Any name matching a restriction in the ``excluded_subtrees`` field is
    invalid regardless of information appearing in the
    ``permitted_subtrees``. At least one of ``permitted_subtrees`` and
    ``excluded_subtrees`` will be non-None.
.. versionadded:: 0.9

The authority key identifier extension provides a means of identifying the public key corresponding to the private key used to sign a certificate. This extension is typically used to assist in determining the appropriate certificate chain. For more information about generation and use of this extension see RFC 5280 section 4.2.1.1.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.AUTHORITY_KEY_IDENTIFIER`.

.. attribute:: key_identifier

    :type: bytes

    A value derived from the public key used to verify the certificate's
    signature.

.. attribute:: authority_cert_issuer

    :type: A list of :class:`GeneralName` instances or None

    The :class:`Name` of the issuer's issuer.

.. attribute:: authority_cert_serial_number

    :type: int or None

    The serial number of the issuer's issuer.

.. classmethod:: from_issuer_public_key(public_key)

    .. versionadded:: 1.0

    .. note::

        This method should be used if the issuer certificate does not
        contain a :class:`~cryptography.x509.SubjectKeyIdentifier`.
        Otherwise, use
        :meth:`~cryptography.x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier`.

    Creates a new AuthorityKeyIdentifier instance using the public key
    provided to generate the appropriate digest. This should be the
    **issuer's public key**. The resulting object will contain
    :attr:`~cryptography.x509.AuthorityKeyIdentifier.key_identifier`, but
    :attr:`~cryptography.x509.AuthorityKeyIdentifier.authority_cert_issuer`
    and
    :attr:`~cryptography.x509.AuthorityKeyIdentifier.authority_cert_serial_number`
    will be None.
    The generated ``key_identifier`` is the SHA1 hash of the ``subjectPublicKey``
    ASN.1 bit string. This is the first recommendation in :rfc:`5280`
    section 4.2.1.2.

    :param public_key: One of
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey`
        ,
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey`
        , or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> issuer_cert = x509.load_pem_x509_certificate(pem_data, default_backend())
        >>> x509.AuthorityKeyIdentifier.from_issuer_public_key(issuer_cert.public_key())
        <AuthorityKeyIdentifier(key_identifier=b'X\x01\x84$\x1b\xbc+R\x94J=\xa5\x10r\x14Q\xf5\xaf:\xc9', authority_cert_issuer=None, authority_cert_serial_number=None)>

.. classmethod:: from_issuer_subject_key_identifier(ski)

    .. versionadded:: 1.3

    .. note::
        This method should be used if the issuer certificate contains a
        :class:`~cryptography.x509.SubjectKeyIdentifier`.  Otherwise, use
        :meth:`~cryptography.x509.AuthorityKeyIdentifier.from_issuer_public_key`.

    Creates a new AuthorityKeyIdentifier instance using the
    SubjectKeyIdentifier from the issuer certificate. The resulting object
    will contain
    :attr:`~cryptography.x509.AuthorityKeyIdentifier.key_identifier`, but
    :attr:`~cryptography.x509.AuthorityKeyIdentifier.authority_cert_issuer`
    and
    :attr:`~cryptography.x509.AuthorityKeyIdentifier.authority_cert_serial_number`
    will be None.

    :param ski: The
        :class:`~cryptography.x509.SubjectKeyIdentifier` from the issuer
        certificate.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> issuer_cert = x509.load_pem_x509_certificate(pem_data, default_backend())
        >>> ski = issuer_cert.extensions.get_extension_for_class(x509.SubjectKeyIdentifier)
        >>> x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier(ski)
        <AuthorityKeyIdentifier(key_identifier=b'X\x01\x84$\x1b\xbc+R\x94J=\xa5\x10r\x14Q\xf5\xaf:\xc9', authority_cert_issuer=None, authority_cert_serial_number=None)>
.. versionadded:: 0.9

The subject key identifier extension provides a means of identifying certificates that contain a particular public key.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.SUBJECT_KEY_IDENTIFIER`.

.. attribute:: digest

    :type: bytes

    The binary value of the identifier.

.. classmethod:: from_public_key(public_key)

    .. versionadded:: 1.0

    Creates a new SubjectKeyIdentifier instance using the public key
    provided to generate the appropriate digest. This should be the public
    key that is in the certificate. The generated digest is the SHA1 hash
    of the ``subjectPublicKey`` ASN.1 bit string. This is the first
    recommendation in :rfc:`5280` section 4.2.1.2.

    :param public_key: One of
        :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPublicKey`
        ,
        :class:`~cryptography.hazmat.primitives.asymmetric.dsa.DSAPublicKey`
        , or
        :class:`~cryptography.hazmat.primitives.asymmetric.ec.EllipticCurvePublicKey`.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> csr = x509.load_pem_x509_csr(pem_req_data, default_backend())
        >>> x509.SubjectKeyIdentifier.from_public_key(csr.public_key())
        <SubjectKeyIdentifier(digest=b'\xdb\xaa\xf0\x06\x11\xdbD\xfe\xbf\x93\x03\x8av\x88WP7\xa6\x91\xf7')>
.. versionadded:: 0.9

Subject alternative name is an X.509 extension that provides a list of :ref:`general name <general_name_classes>` instances that provide a set of identities for which the certificate is valid. The object is iterable to get every element.

param list general_names:A list of :class:`GeneralName` instances.
.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.SUBJECT_ALTERNATIVE_NAME`.

.. method:: get_values_for_type(type)

    :param type: A :class:`GeneralName` instance. This is one of the
        :ref:`general name classes <general_name_classes>`.

    :returns: A list of values extracted from the matched general names.
        The type of the returned values depends on the :class:`GeneralName`.

    .. doctest::

        >>> from cryptography import x509
        >>> from cryptography.hazmat.backends import default_backend
        >>> from cryptography.hazmat.primitives import hashes
        >>> cert = x509.load_pem_x509_certificate(cryptography_cert_pem, default_backend())
        >>> # Get the subjectAltName extension from the certificate
        >>> ext = cert.extensions.get_extension_for_oid(ExtensionOID.SUBJECT_ALTERNATIVE_NAME)
        >>> # Get the dNSName entries from the SAN extension
        >>> ext.value.get_values_for_type(x509.DNSName)
        ['www.cryptography.io', 'cryptography.io']
.. versionadded:: 1.0

Issuer alternative name is an X.509 extension that provides a list of :ref:`general name <general_name_classes>` instances that provide a set of identities for the certificate issuer. The object is iterable to get every element.

param list general_names:A list of :class:`GeneralName` instances.
.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.ISSUER_ALTERNATIVE_NAME`.

.. method:: get_values_for_type(type)

    :param type: A :class:`GeneralName` instance. This is one of the
        :ref:`general name classes <general_name_classes>`.

    :returns: A list of values extracted from the matched general names.
.. versionadded:: 2.0

This extension contains :class:`~cryptography.x509.certificate_transparency.SignedCertificateTimestamp` instances which were issued for the pre-certificate corresponding to this certificate. These can be used to verify that the certificate is included in a public Certificate Transparency log.

It is an iterable containing one or more :class:`~cryptography.x509.certificate_transparency.SignedCertificateTimestamp` objects.

param list scts:A list of :class:`~cryptography.x509.certificate_transparency.SignedCertificateTimestamp` objects.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.PRECERT_SIGNED_CERTIFICATE_TIMESTAMPS`.
.. versionadded:: 2.4

This extension indicates that the certificate should not be treated as a certificate for the purposes of validation, but is instead for submission to a certificate transparency log in order to obtain SCTs which will be embedded in a :class:`PrecertificateSignedCertificateTimestamps` extension on the final certificate.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.PRECERT_POISON`.
.. versionadded:: 2.1

The delta CRL indicator is a CRL extension that identifies a CRL as being a delta CRL. Delta CRLs contain updates to revocation information previously distributed, rather than all the information that would appear in a complete CRL.

param int crl_number:The CRL number of the complete CRL that the delta CRL is updating.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.DELTA_CRL_INDICATOR`.

.. attribute:: crl_number

    :type: int
.. versionadded:: 0.9

The authority information access extension indicates how to access information and services for the issuer of the certificate in which the extension appears. Information and services may include online validation services (such as OCSP) and issuer data. It is an iterable, containing one or more :class:`~cryptography.x509.AccessDescription` instances.

param list descriptions:A list of :class:`AccessDescription` objects.
.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.AUTHORITY_INFORMATION_ACCESS`.
.. versionadded:: 0.9

.. attribute:: access_method

    :type: :class:`ObjectIdentifier`

    The access method defines what the ``access_location`` means. It must
    be either
    :attr:`~cryptography.x509.oid.AuthorityInformationAccessOID.OCSP` or
    :attr:`~cryptography.x509.oid.AuthorityInformationAccessOID.CA_ISSUERS`.
    If it is
    :attr:`~cryptography.x509.oid.AuthorityInformationAccessOID.OCSP`
    the access location will be where to obtain OCSP
    information for the certificate. If it is
    :attr:`~cryptography.x509.oid.AuthorityInformationAccessOID.CA_ISSUERS`
    the access location will provide additional information about the
    issuing certificate.

.. attribute:: access_location

    :type: :class:`GeneralName`

    Where to access the information defined by the access method.
.. versionadded:: 2.1

The freshest CRL extension (also known as Delta CRL Distribution Point) identifies how delta CRL information is obtained. It is an iterable, containing one or more :class:`DistributionPoint` instances.

param list distribution_points:A list of :class:`DistributionPoint` instances.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.FRESHEST_CRL`.
.. versionadded:: 0.9

The CRL distribution points extension identifies how CRL information is obtained. It is an iterable, containing one or more :class:`DistributionPoint` instances.

param list distribution_points:A list of :class:`DistributionPoint` instances.
.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.CRL_DISTRIBUTION_POINTS`.
.. versionadded:: 0.9

.. attribute:: full_name

    :type: list of :class:`GeneralName` instances or None

    This field describes methods to retrieve the CRL. At most one of
    ``full_name`` or ``relative_name`` will be non-None.

.. attribute:: relative_name

    :type: :class:`RelativeDistinguishedName` or None

    This field describes methods to retrieve the CRL relative to the CRL
    issuer. At most one of ``full_name`` or ``relative_name`` will be
    non-None.

    .. versionchanged:: 1.6
        Changed from :class:`Name` to :class:`RelativeDistinguishedName`.

.. attribute:: crl_issuer

    :type: list of :class:`GeneralName` instances or None

    Information about the issuer of the CRL.

.. attribute:: reasons

    :type: frozenset of :class:`ReasonFlags` or None

    The reasons a given distribution point may be used for when performing
    revocation checks.
.. versionadded:: 0.9

An enumeration for CRL reasons.

.. attribute:: unspecified

    It is unspecified why the certificate was revoked. This reason cannot
    be used as a reason flag in a :class:`DistributionPoint`.

.. attribute:: key_compromise

    This reason indicates that the private key was compromised.

.. attribute:: ca_compromise

    This reason indicates that the CA issuing the certificate was
    compromised.

.. attribute:: affiliation_changed

    This reason indicates that the subject's name or other information has
    changed.

.. attribute:: superseded

    This reason indicates that a certificate has been superseded.

.. attribute:: cessation_of_operation

    This reason indicates that the certificate is no longer required.

.. attribute:: certificate_hold

    This reason indicates that the certificate is on hold.

.. attribute:: privilege_withdrawn

    This reason indicates that the privilege granted by this certificate
    have been withdrawn.

.. attribute:: aa_compromise

    When an attribute authority has been compromised.

.. attribute:: remove_from_crl

    This reason indicates that the certificate was on hold and should be
    removed from the CRL. This reason cannot be used as a reason flag
    in a :class:`DistributionPoint`.
.. versionadded:: 1.0

The inhibit anyPolicy extension indicates that the special OID :attr:`~cryptography.x509.oid.CertificatePoliciesOID.ANY_POLICY`, is not considered an explicit match for other :class:`CertificatePolicies` except when it appears in an intermediate self-issued CA certificate. The value indicates the number of additional non-self-issued certificates that may appear in the path before :attr:`~cryptography.x509.oid.CertificatePoliciesOID.ANY_POLICY` is no longer permitted. For example, a value of one indicates that :attr:`~cryptography.x509.oid.CertificatePoliciesOID.ANY_POLICY` may be processed in certificates issued by the subject of this certificate, but not in additional certificates in the path.

.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.INHIBIT_ANY_POLICY`.

.. attribute:: skip_certs

    :type: int
.. versionadded:: 1.3

The policy constraints extension is used to inhibit policy mapping or require that each certificate in a chain contain an acceptable policy identifier. For more information about the use of this extension see RFC 5280.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns :attr:`~cryptography.x509.oid.ExtensionOID.POLICY_CONSTRAINTS`.

.. attribute:: require_explicit_policy

    :type: int or None

    If this field is not None, the value indicates the number of additional
    certificates that may appear in the chain before an explicit policy is
    required for the entire path. When an explicit policy is required, it
    is necessary for all certificates in the chain to contain an acceptable
    policy identifier in the certificate policies extension.  An
    acceptable policy identifier is the identifier of a policy required
    by the user of the certification path or the identifier of a policy
    that has been declared equivalent through policy mapping.

.. attribute:: inhibit_policy_mapping

    :type: int or None

    If this field is not None, the value indicates the number of additional
    certificates that may appear in the chain before policy mapping is no
    longer permitted.  For example, a value of one indicates that policy
    mapping may be processed in certificates issued by the subject of this
    certificate, but not in additional certificates in the chain.
.. versionadded:: 1.2

The CRL number is a CRL extension that conveys a monotonically increasing sequence number for a given CRL scope and CRL issuer. This extension allows users to easily determine when a particular CRL supersedes another CRL. RFC 5280 requires that this extension be present in conforming CRLs.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.CRL_NUMBER`.

.. attribute:: crl_number

    :type: int
.. versionadded:: 2.5

Issuing distribution point is a CRL extension that identifies the CRL distribution point and scope for a particular CRL. It indicates whether the CRL covers revocation for end entity certificates only, CA certificates only, attribute certificates only, or a limited set of reason codes. For specific details on the way this extension should be processed see RFC 5280.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.ISSUING_DISTRIBUTION_POINT`.

.. attribute:: only_contains_user_certs

    :type: bool

    Set to ``True`` if the CRL this extension is embedded within only
    contains information about user certificates.

.. attribute:: only_contains_ca_certs

    :type: bool

    Set to ``True`` if the CRL this extension is embedded within only
    contains information about CA certificates.

.. attribute:: indirect_crl

    :type: bool

    Set to ``True`` if the CRL this extension is embedded within includes
    certificates issued by one or more authorities other than the CRL
    issuer.

.. attribute:: only_contains_attribute_certs

    :type: bool

    Set to ``True`` if the CRL this extension is embedded within only
    contains information about attribute certificates.

.. attribute:: only_some_reasons

    :type: frozenset of :class:`ReasonFlags` or None

    The reasons for which the issuing distribution point is valid. None
    indicates that it is valid for all reasons.

.. attribute:: full_name

    :type: list of :class:`GeneralName` instances or None

    This field describes methods to retrieve the CRL. At most one of
    ``full_name`` or ``relative_name`` will be non-None.

.. attribute:: relative_name

    :type: :class:`RelativeDistinguishedName` or None

    This field describes methods to retrieve the CRL relative to the CRL
    issuer. At most one of ``full_name`` or ``relative_name`` will be
    non-None.
.. versionadded:: 1.2

A generic extension class used to hold the raw value of extensions that cryptography does not know how to parse.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns the OID associated with this extension.

.. attribute:: value

    :type: bytes

    Returns the DER encoded bytes payload of the extension.
.. versionadded:: 0.9

The certificate policies extension is an iterable, containing one or more :class:`PolicyInformation` instances.

param list policies:A list of :class:`PolicyInformation` instances.
.. attribute:: oid

    .. versionadded:: 1.0

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.ExtensionOID.CERTIFICATE_POLICIES`.

Certificate Policies Classes

These classes may be present within a :class:`CertificatePolicies` instance.

.. versionadded:: 0.9

Contains a policy identifier and an optional list of qualifiers.

.. attribute:: policy_identifier

    :type: :class:`ObjectIdentifier`

.. attribute:: policy_qualifiers

    :type: list

    A list consisting of :term:`text` and/or :class:`UserNotice` objects.
    If the value is text it is a pointer to the practice statement
    published by the certificate authority. If it is a user notice it is
    meant for display to the relying party when the certificate is
    used.
.. versionadded:: 0.9

User notices are intended for display to a relying party when a certificate is used. In practice, few if any UIs expose this data and it is a rarely encoded component.

.. attribute:: notice_reference

    :type: :class:`NoticeReference` or None

    The notice reference field names an organization and identifies,
    by number, a particular statement prepared by that organization.

.. attribute:: explicit_text

    This field includes an arbitrary textual statement directly in the
    certificate.

    :type: :term:`text`

Notice reference can name an organization and provide information about notices related to the certificate. For example, it might identify the organization name and notice number 1. Application software could have a notice file containing the current set of notices for the named organization; the application would then extract the notice text from the file and display it. In practice this is rarely seen.

.. versionadded:: 0.9

.. attribute:: organization

    :type: :term:`text`

.. attribute:: notice_numbers

    :type: list

    A list of integers.

CRL Entry Extensions

These extensions are only valid within a :class:`RevokedCertificate` object.

.. versionadded:: 1.2

The certificate issuer is an extension that is only valid inside :class:`~cryptography.x509.RevokedCertificate` objects. If the indirectCRL property of the parent CRL's IssuingDistributionPoint extension is set, then this extension identifies the certificate issuer associated with the revoked certificate. The object is iterable to get every element.

param list general_names:A list of :class:`GeneralName` instances.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.CRLEntryExtensionOID.CERTIFICATE_ISSUER`.

.. method:: get_values_for_type(type)

    :param type: A :class:`GeneralName` instance. This is one of the
        :ref:`general name classes <general_name_classes>`.

    :returns: A list of values extracted from the matched general names.
        The type of the returned values depends on the :class:`GeneralName`.
.. versionadded:: 1.2

CRL reason (also known as reasonCode) is an extension that is only valid inside :class:`~cryptography.x509.RevokedCertificate` objects. It identifies a reason for the certificate revocation.

param reason:An element from :class:`~cryptography.x509.ReasonFlags`.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.CRLEntryExtensionOID.CRL_REASON`.

.. attribute:: reason

    :type: An element from :class:`~cryptography.x509.ReasonFlags`
.. versionadded:: 1.2

Invalidity date is an extension that is only valid inside :class:`~cryptography.x509.RevokedCertificate` objects. It provides the date on which it is known or suspected that the private key was compromised or that the certificate otherwise became invalid. This date may be earlier than the revocation date in the CRL entry, which is the date at which the CA processed the revocation.

param invalidity_date:The :class:`datetime.datetime` when it is known or suspected that the private key was compromised.
.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.CRLEntryExtensionOID.INVALIDITY_DATE`.

.. attribute:: invalidity_date

    :type: :class:`datetime.datetime`

OCSP Extensions

.. versionadded:: 2.4

OCSP nonce is an extension that is only valid inside :class:`~cryptography.x509.ocsp.OCSPRequest` and :class:`~cryptography.x509.ocsp.OCSPResponse` objects. The nonce cryptographically binds a request and a response to prevent replay attacks. In practice nonces are rarely used in OCSP due to the desire to precompute OCSP responses at large scale.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns
    :attr:`~cryptography.x509.oid.OCSPExtensionOID.NONCE`.

.. attribute:: nonce

    :type: bytes

Object Identifiers

X.509 elements are frequently identified by :class:`ObjectIdentifier` instances. The following common OIDs are available as constants.

.. currentmodule:: cryptography.x509.oid

These OIDs are typically seen in X.509 names.

.. versionadded:: 1.0

.. attribute:: COMMON_NAME

    Corresponds to the dotted string ``"2.5.4.3"``. Historically the domain
    name would be encoded here for server certificates. :rfc:`2818`
    deprecates this practice and names of that type should now be located
    in a :class:`~cryptography.x509.SubjectAlternativeName` extension.

.. attribute:: COUNTRY_NAME

    Corresponds to the dotted string ``"2.5.4.6"``.

.. attribute:: LOCALITY_NAME

    Corresponds to the dotted string ``"2.5.4.7"``.

.. attribute:: STATE_OR_PROVINCE_NAME

    Corresponds to the dotted string ``"2.5.4.8"``.

.. attribute:: STREET_ADDRESS

    .. versionadded:: 1.6

    Corresponds to the dotted string ``"2.5.4.9"``.

.. attribute:: ORGANIZATION_NAME

    Corresponds to the dotted string ``"2.5.4.10"``.

.. attribute:: ORGANIZATIONAL_UNIT_NAME

    Corresponds to the dotted string ``"2.5.4.11"``.

.. attribute:: SERIAL_NUMBER

    Corresponds to the dotted string ``"2.5.4.5"``. This is distinct from
    the serial number of the certificate itself (which can be obtained with
    :func:`~cryptography.x509.Certificate.serial_number`).

.. attribute:: SURNAME

    Corresponds to the dotted string ``"2.5.4.4"``.

.. attribute:: GIVEN_NAME

    Corresponds to the dotted string ``"2.5.4.42"``.

.. attribute:: TITLE

    Corresponds to the dotted string ``"2.5.4.12"``.

.. attribute:: GENERATION_QUALIFIER

    Corresponds to the dotted string ``"2.5.4.44"``.

.. attribute:: X500_UNIQUE_IDENTIFIER

    .. versionadded:: 1.6

    Corresponds to the dotted string ``"2.5.4.45"``.

.. attribute:: DN_QUALIFIER

    Corresponds to the dotted string ``"2.5.4.46"``. This specifies
    disambiguating information to add to the relative distinguished name of an
    entry. See :rfc:`2256`.

.. attribute:: PSEUDONYM

    Corresponds to the dotted string ``"2.5.4.65"``.

.. attribute:: USER_ID

    .. versionadded:: 1.6

    Corresponds to the dotted string ``"0.9.2342.19200300.100.1.1"``.

.. attribute:: DOMAIN_COMPONENT

    Corresponds to the dotted string ``"0.9.2342.19200300.100.1.25"``. A string
    holding one component of a domain name. See :rfc:`4519`.

.. attribute:: EMAIL_ADDRESS

    Corresponds to the dotted string ``"1.2.840.113549.1.9.1"``.

.. attribute:: JURISDICTION_COUNTRY_NAME

    Corresponds to the dotted string ``"1.3.6.1.4.1.311.60.2.1.3"``.

.. attribute:: JURISDICTION_LOCALITY_NAME

    Corresponds to the dotted string ``"1.3.6.1.4.1.311.60.2.1.1"``.

.. attribute:: JURISDICTION_STATE_OR_PROVINCE_NAME

    Corresponds to the dotted string ``"1.3.6.1.4.1.311.60.2.1.2"``.

.. attribute:: BUSINESS_CATEGORY

    Corresponds to the dotted string ``"2.5.4.15"``.

.. attribute:: POSTAL_ADDRESS

    .. versionadded:: 1.6

    Corresponds to the dotted string ``"2.5.4.16"``.

.. attribute:: POSTAL_CODE

    .. versionadded:: 1.6

    Corresponds to the dotted string ``"2.5.4.17"``.
.. versionadded:: 1.0

.. attribute:: RSA_WITH_MD5

    Corresponds to the dotted string ``"1.2.840.113549.1.1.4"``. This is
    an MD5 digest signed by an RSA key.

.. attribute:: RSA_WITH_SHA1

    Corresponds to the dotted string ``"1.2.840.113549.1.1.5"``. This is
    a SHA1 digest signed by an RSA key.

.. attribute:: RSA_WITH_SHA224

    Corresponds to the dotted string ``"1.2.840.113549.1.1.14"``. This is
    a SHA224 digest signed by an RSA key.

.. attribute:: RSA_WITH_SHA256

    Corresponds to the dotted string ``"1.2.840.113549.1.1.11"``. This is
    a SHA256 digest signed by an RSA key.

.. attribute:: RSA_WITH_SHA384

    Corresponds to the dotted string ``"1.2.840.113549.1.1.12"``. This is
    a SHA384 digest signed by an RSA key.

.. attribute:: RSA_WITH_SHA512

    Corresponds to the dotted string ``"1.2.840.113549.1.1.13"``. This is
    a SHA512 digest signed by an RSA key.

.. attribute:: RSASSA_PSS

    .. versionadded:: 2.3

    Corresponds to the dotted string ``"1.2.840.113549.1.1.10"``. This is
    signed by an RSA key using the Probabilistic Signature Scheme (PSS)
    padding from RFC 4055. The hash function and padding are defined by
    signature algorithm parameters.

.. attribute:: ECDSA_WITH_SHA1

    Corresponds to the dotted string ``"1.2.840.10045.4.1"``. This is a SHA1
    digest signed by an ECDSA key.

.. attribute:: ECDSA_WITH_SHA224

    Corresponds to the dotted string ``"1.2.840.10045.4.3.1"``. This is
    a SHA224 digest signed by an ECDSA key.

.. attribute:: ECDSA_WITH_SHA256

    Corresponds to the dotted string ``"1.2.840.10045.4.3.2"``. This is
    a SHA256 digest signed by an ECDSA key.

.. attribute:: ECDSA_WITH_SHA384

    Corresponds to the dotted string ``"1.2.840.10045.4.3.3"``. This is
    a SHA384 digest signed by an ECDSA key.

.. attribute:: ECDSA_WITH_SHA512

    Corresponds to the dotted string ``"1.2.840.10045.4.3.4"``. This is
    a SHA512 digest signed by an ECDSA key.

.. attribute:: DSA_WITH_SHA1

    Corresponds to the dotted string ``"1.2.840.10040.4.3"``. This is
    a SHA1 digest signed by a DSA key.

.. attribute:: DSA_WITH_SHA224

    Corresponds to the dotted string ``"2.16.840.1.101.3.4.3.1"``. This is
    a SHA224 digest signed by a DSA key.

.. attribute:: DSA_WITH_SHA256

    Corresponds to the dotted string ``"2.16.840.1.101.3.4.3.2"``. This is
    a SHA256 digest signed by a DSA key.
.. versionadded:: 1.0

.. attribute:: SERVER_AUTH

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.3.1"``. This is used
    to denote that a certificate may be used for TLS web server
    authentication.

.. attribute:: CLIENT_AUTH

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.3.2"``. This is used
    to denote that a certificate may be used for TLS web client
    authentication.

.. attribute:: CODE_SIGNING

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.3.3"``. This is used
    to denote that a certificate may be used for code signing.

.. attribute:: EMAIL_PROTECTION

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.3.4"``. This is used
    to denote that a certificate may be used for email protection.

.. attribute:: TIME_STAMPING

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.3.8"``. This is used
    to denote that a certificate may be used for time stamping.

.. attribute:: OCSP_SIGNING

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.3.9"``. This is used
    to denote that a certificate may be used for signing OCSP responses.

.. attribute:: ANY_EXTENDED_KEY_USAGE

    .. versionadded:: 2.0

    Corresponds to the dotted string ``"2.5.29.37.0"``. This is used to
    denote that a certificate may be used for _any_ purposes.
.. versionadded:: 1.0

.. attribute:: OCSP

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.48.1"``. Used as the
    identifier for OCSP data in
    :class:`~cryptography.x509.AccessDescription` objects.

.. attribute:: CA_ISSUERS

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.48.2"``. Used as the
    identifier for CA issuer data in
    :class:`~cryptography.x509.AccessDescription` objects.
.. versionadded:: 1.0

.. attribute:: CPS_QUALIFIER

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.2.1"``.

.. attribute:: CPS_USER_NOTICE

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.2.2"``.

.. attribute:: ANY_POLICY

    Corresponds to the dotted string ``"2.5.29.32.0"``.
.. versionadded:: 1.0

.. attribute:: BASIC_CONSTRAINTS

    Corresponds to the dotted string ``"2.5.29.19"``. The identifier for the
    :class:`~cryptography.x509.BasicConstraints` extension type.

.. attribute:: KEY_USAGE

    Corresponds to the dotted string ``"2.5.29.15"``. The identifier for the
    :class:`~cryptography.x509.KeyUsage` extension type.

.. attribute:: SUBJECT_ALTERNATIVE_NAME

    Corresponds to the dotted string ``"2.5.29.17"``. The identifier for the
    :class:`~cryptography.x509.SubjectAlternativeName` extension type.

.. attribute:: ISSUER_ALTERNATIVE_NAME

    Corresponds to the dotted string ``"2.5.29.18"``. The identifier for the
    :class:`~cryptography.x509.IssuerAlternativeName` extension type.

.. attribute:: SUBJECT_KEY_IDENTIFIER

    Corresponds to the dotted string ``"2.5.29.14"``. The identifier for the
    :class:`~cryptography.x509.SubjectKeyIdentifier` extension type.

.. attribute:: NAME_CONSTRAINTS

    Corresponds to the dotted string ``"2.5.29.30"``. The identifier for the
    :class:`~cryptography.x509.NameConstraints` extension type.

.. attribute:: CRL_DISTRIBUTION_POINTS

    Corresponds to the dotted string ``"2.5.29.31"``. The identifier for the
    :class:`~cryptography.x509.CRLDistributionPoints` extension type.

.. attribute:: CERTIFICATE_POLICIES

    Corresponds to the dotted string ``"2.5.29.32"``. The identifier for the
    :class:`~cryptography.x509.CertificatePolicies` extension type.

.. attribute:: AUTHORITY_KEY_IDENTIFIER

    Corresponds to the dotted string ``"2.5.29.35"``. The identifier for the
    :class:`~cryptography.x509.AuthorityKeyIdentifier` extension type.

.. attribute:: EXTENDED_KEY_USAGE

    Corresponds to the dotted string ``"2.5.29.37"``. The identifier for the
    :class:`~cryptography.x509.ExtendedKeyUsage` extension type.

.. attribute:: AUTHORITY_INFORMATION_ACCESS

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.1.1"``. The identifier
    for the :class:`~cryptography.x509.AuthorityInformationAccess` extension
    type.

.. attribute:: INHIBIT_ANY_POLICY

    Corresponds to the dotted string ``"2.5.29.54"``. The identifier
    for the :class:`~cryptography.x509.InhibitAnyPolicy` extension type.

.. attribute:: OCSP_NO_CHECK

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.48.1.5"``. The
    identifier for the :class:`~cryptography.x509.OCSPNoCheck` extension
    type.

.. attribute:: TLS_FEATURE

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.1.24"``. The
    identifier for the :class:`~cryptography.x509.TLSFeature` extension
    type.

.. attribute:: CRL_NUMBER

    Corresponds to the dotted string ``"2.5.29.20"``. The identifier for
    the ``CRLNumber`` extension type. This extension only has meaning
    for certificate revocation lists.

.. attribute:: DELTA_CRL_INDICATOR

    .. versionadded:: 2.1

    Corresponds to the dotted string ``"2.5.29.27"``. The identifier for
    the ``DeltaCRLIndicator`` extension type. This extension only has
    meaning for certificate revocation lists.

.. attribute:: PRECERT_SIGNED_CERTIFICATE_TIMESTAMPS

    .. versionadded:: 1.9

    Corresponds to the dotted string ``"1.3.6.1.4.1.11129.2.4.2"``.

.. attribute:: PRECERT_POISON

    .. versionadded:: 2.4

    Corresponds to the dotted string ``"1.3.6.1.4.1.11129.2.4.3"``.

.. attribute:: POLICY_CONSTRAINTS

    Corresponds to the dotted string ``"2.5.29.36"``. The identifier for the
    :class:`~cryptography.x509.PolicyConstraints` extension type.

.. attribute:: FRESHEST_CRL

    Corresponds to the dotted string ``"2.5.29.46"``. The identifier for the
    :class:`~cryptography.x509.FreshestCRL` extension type.

.. attribute:: ISSUING_DISTRIBUTION_POINT

    .. versionadded:: 2.4

    Corresponds to the dotted string ``"2.5.29.28"``.
.. versionadded:: 1.2

.. attribute:: CERTIFICATE_ISSUER

    Corresponds to the dotted string ``"2.5.29.29"``.

.. attribute:: CRL_REASON

    Corresponds to the dotted string ``"2.5.29.21"``.

.. attribute:: INVALIDITY_DATE

    Corresponds to the dotted string ``"2.5.29.24"``.
.. versionadded:: 2.4

.. attribute:: NONCE

    Corresponds to the dotted string ``"1.3.6.1.5.5.7.48.1.2"``.

Helper Functions

.. currentmodule:: cryptography.x509

.. function:: random_serial_number()

    .. versionadded:: 1.6

    Generates a random serial number suitable for use when constructing
    certificates.

Exceptions

.. currentmodule:: cryptography.x509

This is raised when an X.509 certificate has an invalid version number.

.. attribute:: parsed_version

    :type: int

    Returns the raw version that was parsed from the certificate.

This is raised when more than one X.509 extension of the same type is found within a certificate.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns the OID.

This is raised when calling :meth:`Extensions.get_extension_for_oid` with an extension OID that is not present in the certificate.

.. attribute:: oid

    :type: :class:`ObjectIdentifier`

    Returns the OID.

This is raised when a certificate contains an unsupported general name type in an extension.

.. attribute:: type

    :type: int

    The integer value of the unsupported type. The complete list of
    types can be found in `RFC 5280 section 4.2.1.6`_.