X.509 Reference

Loading Certificates

cryptography.x509.load_pem_x509_certificate(data)

New in version 0.7.

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

Parameters:

data (bytes) – The PEM encoded certificate data.

Returns:

An instance of Certificate.

>>> from cryptography import x509
>>> cert = x509.load_pem_x509_certificate(pem_data)
>>> cert.serial_number
2
cryptography.x509.load_der_x509_certificate(data)

New in version 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).

Parameters:

data (bytes) – The DER encoded certificate data.

Returns:

An instance of Certificate.

Loading Certificate Revocation Lists

cryptography.x509.load_pem_x509_crl(data)

New in version 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-----.

Parameters:

data (bytes) – The PEM encoded request data.

Returns:

An instance of CertificateRevocationList.

>>> from cryptography import x509
>>> from cryptography.hazmat.primitives import hashes
>>> crl = x509.load_pem_x509_crl(pem_crl_data)
>>> isinstance(crl.signature_hash_algorithm, hashes.SHA256)
True
cryptography.x509.load_der_x509_crl(data)

New in version 1.1.

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

Parameters:

data (bytes) – The DER encoded request data.

Returns:

An instance of CertificateRevocationList.

Loading Certificate Signing Requests

cryptography.x509.load_pem_x509_csr(data)

New in version 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.

Parameters:

data (bytes) – The PEM encoded request data.

Returns:

An instance of CertificateSigningRequest.

>>> from cryptography import x509
>>> from cryptography.hazmat.primitives import hashes
>>> csr = x509.load_pem_x509_csr(pem_req_data)
>>> isinstance(csr.signature_hash_algorithm, hashes.SHA256)
True
cryptography.x509.load_der_x509_csr(data)

New in version 0.9.

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

Parameters:

data (bytes) – The DER encoded request data.

Returns:

An instance of CertificateSigningRequest.

X.509 Certificate Object

class cryptography.x509.Certificate

New in version 0.7.

version
Type:

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 X.509 version.

>>> cert.version
<Version.v3: 2>
fingerprint(algorithm)
Parameters:

algorithm – The HashAlgorithm that will be used to generate the fingerprint.

Return bytes:

The fingerprint using the supplied hash algorithm, as bytes.

>>> 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?'
serial_number
Type:

int

The serial as a Python integer.

>>> cert.serial_number
2
public_key()

The public key associated with the certificate.

Returns:

One of RSAPublicKey, DSAPublicKey, EllipticCurvePublicKey, Ed25519PublicKey, Ed448PublicKey, X25519PublicKey or X448PublicKey

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

datetime.datetime

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

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

datetime.datetime

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

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

New in version 0.8.

Type:

Name

The Name of the issuer.

subject

New in version 0.8.

Type:

Name

The Name of the subject.

signature_hash_algorithm
Type:

HashAlgorithm

Returns the HashAlgorithm which was used in signing this certificate. Can be None if signature did not use separate hash (ED25519, ED448).

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

New in version 1.6.

Type:

ObjectIdentifier

Returns the ObjectIdentifier of the signature algorithm used to sign the certificate. This will be one of the OIDs from SignatureAlgorithmOID.

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

Extensions

The extensions encoded in the certificate.

Raises:
>>> 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=False, decipher_only=False)>)>
<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)>)>
signature

New in version 1.2.

Type:

bytes

The bytes of the certificate’s signature.

tbs_certificate_bytes

New in version 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.

>>> 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)
>>> cert_to_check = x509.load_pem_x509_certificate(pem_data_to_check)
>>> 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 InvalidSignature exception will be raised if the signature fails to verify.

tbs_precertificate_bytes

New in version 38.0.

Type:

bytes

Raises:

ValueError – If the certificate doesn’t have the expected Certificate Transparency extensions.

The DER encoded bytes payload (as defined by RFC 6962) that is hashed and then signed by the private key of the pre-certificate’s issuer. This data may be used to validate a Signed Certificate Timestamp’s signature, but use extreme caution as SCT validation is a complex problem that involves much more than just signature checks.

This method is primarily useful in the context of programs that interact with and verify the products of Certificate Transparency logs, as specified in RFC 6962. If you are not directly interacting with a Certificate Transparency log, this method unlikely to be what you want. To make unintentional misuse less likely, it raises a ValueError if the underlying certificate does not contain the expected Certificate Transparency extensions.

public_bytes(encoding)

New in version 1.0.

Parameters:

encoding – The 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

class cryptography.x509.CertificateRevocationList

New in version 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 '...RevokedCertificate'>
>>> for r in crl:
...     print(r.serial_number)
0
fingerprint(algorithm)
Parameters:

algorithm – The HashAlgorithm that will be used to generate the fingerprint.

Return bytes:

The fingerprint using the supplied hash algorithm, as bytes.

>>> from cryptography.hazmat.primitives import hashes
>>> crl.fingerprint(hashes.SHA256())
b'\xe3\x1d\xb5P\x18\x9ed\x9f\x16O\x9dm\xc1>\x8c\xca\xb1\xc6x?T\x9f\xe9t_\x1d\x8dF8V\xf78'
get_revoked_certificate_by_serial_number(serial_number)

New in version 2.3.

Parameters:

serial_number – The serial as a Python integer.

Returns:

RevokedCertificate if the serial_number is present in the CRL or None if it is not.

signature_hash_algorithm
Type:

HashAlgorithm

Returns the HashAlgorithm which was used in signing this CRL. Can be None if signature did not use separate hash (ED25519, ED448).

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

New in version 1.6.

Type:

ObjectIdentifier

Returns the ObjectIdentifier of the signature algorithm used to sign the CRL. This will be one of the OIDs from SignatureAlgorithmOID.

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

Name

The Name of the issuer.

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

datetime.datetime

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

>>> crl.next_update
datetime.datetime(2016, 1, 1, 0, 0)
last_update
Type:

datetime.datetime

A naïve datetime representing when this CRL was last updated.

>>> crl.last_update
datetime.datetime(2015, 1, 1, 0, 0)
extensions
Type:

Extensions

The extensions encoded in the CRL.

signature

New in version 1.2.

Type:

bytes

The bytes of the CRL’s signature.

tbs_certlist_bytes

New in version 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.

public_bytes(encoding)

New in version 1.2.

Parameters:

encoding – The 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.

is_signature_valid(public_key)

New in version 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

class cryptography.x509.CertificateBuilder

New in version 1.0.

>>> from cryptography import x509
>>> 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,
... )
>>> 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(),
... )
>>> isinstance(certificate, x509.Certificate)
True
issuer_name(name)

Sets the issuer’s distinguished name.

Parameters:

name – The Name that describes the issuer (CA).

subject_name(name)

Sets the subject’s distinguished name.

Parameters:

name – The Name that describes the subject.

public_key(public_key)

Sets the subject’s public key.

Parameters:

public_key – The subject’s public key. This can be one of RSAPublicKey, DSAPublicKey, EllipticCurvePublicKey, Ed25519PublicKey, Ed448PublicKey, X25519PublicKey or X448PublicKey.

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 Random number generation.

Parameters:

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 random_serial_number() when possible.

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.

Parameters:

time – The 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.

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.

Parameters:

time – The 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.

add_extension(extval, critical)

Adds an X.509 extension to the certificate.

Parameters:

  • extval – An extension conforming to the ExtensionType interface.

  • critical – Set to True if the extension must be understood and handled by whoever reads the certificate.

sign(private_key, algorithm)

Sign the certificate using the CA’s private key.

Parameters:
Returns:

Certificate

X.509 CSR (Certificate Signing Request) Object

class cryptography.x509.CertificateSigningRequest

New in version 0.9.

public_key()

The public key associated with the request.

Returns:

One of RSAPublicKey, DSAPublicKey, EllipticCurvePublicKey, Ed25519PublicKey or Ed448PublicKey.

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

Name

The Name of the subject.

signature_hash_algorithm
Type:

HashAlgorithm

Returns the HashAlgorithm which was used in signing this request. Can be None if signature did not use separate hash (ED25519, ED448).

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

New in version 1.6.

Type:

ObjectIdentifier

Returns the ObjectIdentifier of the signature algorithm used to sign the request. This will be one of the OIDs from SignatureAlgorithmOID.

>>> csr.signature_algorithm_oid
<ObjectIdentifier(oid=1.2.840.113549.1.1.11, name=sha256WithRSAEncryption)>
extensions
Type:

Extensions

The extensions encoded in the certificate signing request.

Raises:
attributes

New in version 36.0.

Type:

Attributes

The attributes encoded in the certificate signing request.

public_bytes(encoding)

New in version 1.0.

Parameters:

encoding – The 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.

signature

New in version 1.2.

Type:

bytes

The bytes of the certificate signing request’s signature.

tbs_certrequest_bytes

New in version 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.

is_signature_valid

New in version 1.3.

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

X.509 Certificate Revocation List Builder

class cryptography.x509.CertificateRevocationListBuilder

New in version 1.2.

>>> from cryptography import x509
>>> 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,
... )
>>> 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()
>>> builder = builder.add_revoked_certificate(revoked_cert)
>>> crl = builder.sign(
...     private_key=private_key, algorithm=hashes.SHA256(),
... )
>>> len(crl)
1
issuer_name(name)

Sets the issuer’s distinguished name.

Parameters:

name – The Name that describes the issuer (CA).

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.

Parameters:

time – The 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.

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.

Parameters:

time – The datetime.datetime object (in UTC) that marks the next update time for this CRL.

add_extension(extval, critical)

Adds an X.509 extension to this CRL.

Parameters:

  • extval – An extension with the ExtensionType interface.

  • critical – Set to True if the extension must be understood and handled by whoever reads the CRL.

add_revoked_certificate(revoked_certificate)

Adds a revoked certificate to this CRL.

Parameters:

revoked_certificate – An instance of RevokedCertificate. These can be obtained from an existing CRL or created with RevokedCertificateBuilder.

sign(private_key, algorithm)

Sign this CRL using the CA’s private key.

Parameters:
Returns:

CertificateRevocationList

X.509 Revoked Certificate Object

class cryptography.x509.RevokedCertificate

New in version 1.0.

serial_number
Type:

int

An integer representing the serial number of the revoked certificate.

>>> revoked_certificate.serial_number
0
revocation_date
Type:

datetime.datetime

A naïve datetime representing the date this certificates was revoked.

>>> revoked_certificate.revocation_date
datetime.datetime(2015, 1, 1, 0, 0)
extensions
Type:

Extensions

The extensions encoded in the revoked certificate.

>>> 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

class cryptography.x509.RevokedCertificateBuilder

This class is used to create RevokedCertificate objects that can be used with the CertificateRevocationListBuilder.

New in version 1.2.

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

Sets the revoked certificate’s serial number.

Parameters:

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

revocation_date(time)

Sets the certificate’s revocation date.

Parameters:

time – The datetime.datetime object (in UTC) that marks the revocation time for the certificate.

add_extension(extval, critical)

Adds an X.509 extension to this revoked certificate.

Parameters:

  • extval – An instance of one of the CRL entry extensions.

  • critical – Set to True if the extension must be understood and handled.

build()

Create a revoked certificate object.

Returns:

RevokedCertificate

X.509 CSR (Certificate Signing Request) Builder Object

class cryptography.x509.CertificateSigningRequestBuilder

New in version 1.0.

>>> from cryptography import x509
>>> from cryptography.hazmat.primitives import hashes
>>> from cryptography.hazmat.primitives.asymmetric import rsa
>>> from cryptography.x509.oid import AttributeOID, NameOID
>>> private_key = rsa.generate_private_key(
...     public_exponent=65537,
...     key_size=2048,
... )
>>> 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,
... )
>>> builder = builder.add_attribute(
...     AttributeOID.CHALLENGE_PASSWORD, b"changeit"
... )
>>> request = builder.sign(
...     private_key, hashes.SHA256()
... )
>>> isinstance(request, x509.CertificateSigningRequest)
True
subject_name(name)
Parameters:

name – The Name of the certificate subject.

Returns:

A new CertificateSigningRequestBuilder.

add_extension(extension, critical)
Parameters:

  • extension – An extension conforming to the ExtensionType interface.

  • critical – Set to True if the extension must be understood and handled by whoever reads the certificate.

Returns:

A new CertificateSigningRequestBuilder.

add_attribute(oid, value)

New in version 3.0.

Parameters:
Returns:

A new CertificateSigningRequestBuilder.

sign(private_key, algorithm)
Parameters:
Returns:

A new CertificateSigningRequest.

class cryptography.x509.Name

New in version 0.8.

An X509 Name is an ordered list of attributes. The object is iterable to get every attribute or you can use 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 RelativeDistinguishedName objects.

A Name can be initialized with an iterable of NameAttribute (the common case where each RDN has a single attribute) or an iterable of 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')>
rdns

New in version 1.6.

Type:

list of RelativeDistinguishedName

classmethod from_rfc4514_string(data, attr_name_overrides=None)
Parameters:

  • data (str) – An RFC 4514 string.

  • attr_name_overrides – Specify custom OID to name mappings, which can be used to match vendor-specific extensions. See NameOID for common attribute OIDs.

Returns:

A Name parsed from data.

>>> x509.Name.from_rfc4514_string("CN=cryptography.io")
<Name(CN=cryptography.io)>
>>> x509.Name.from_rfc4514_string("E=pyca@cryptography.io", {"E": NameOID.EMAIL_ADDRESS})
<Name(1.2.840.113549.1.9.1=pyca@cryptography.io)>
get_attributes_for_oid(oid)
Parameters:

oid – An ObjectIdentifier instance.

Returns:

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

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

New in version 1.6.

Return bytes:

The DER encoded name.

rfc4514_string(attr_name_overrides=None)

New in version 2.5.

Changed in version 36.0: Added attr_name_overrides parameter.

Format the given name as a RFC 4514 Distinguished Name string, for example CN=mydomain.com,O=My Org,C=US.

By default, attributes CN, L, ST, O, OU, C, STREET, DC, UID are represented by their short name. Unrecognized attributes are formatted as dotted OID strings.

Example:

>>> name = x509.Name([
...     x509.NameAttribute(NameOID.EMAIL_ADDRESS, "santa@north.pole"),
...     x509.NameAttribute(NameOID.COMMON_NAME, "Santa Claus"),
... ])
>>> name.rfc4514_string()
'CN=Santa Claus,1.2.840.113549.1.9.1=santa@north.pole'
>>> name.rfc4514_string({NameOID.EMAIL_ADDRESS: "E"})
'CN=Santa Claus,E=santa@north.pole'
Parameters:

attr_name_overrides (Dict-like mapping from ObjectIdentifier to str) – Specify custom OID to name mappings, which can be used to match vendor-specific extensions. See NameOID for common attribute OIDs.

Return type:

str

class cryptography.x509.Version

New in version 0.7.

An enumeration for X.509 versions.

v1

For version 1 X.509 certificates.

v3

For version 3 X.509 certificates.

class cryptography.x509.NameAttribute

New in version 0.8.

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

oid
Type:

ObjectIdentifier

The attribute OID.

value
Type:

str

The value of the attribute.

rfc4514_attribute_name

New in version 35.0.

Type:

str

The RFC 4514 short attribute name (for example “CN”), or the OID dotted string if a short name is unavailable.

rfc4514_string(attr_name_overrides=None)

New in version 2.5.

Changed in version 36.0: Added attr_name_overrides parameter.

Return str:

Format the given attribute as a RFC 4514 Distinguished Name string.

Parameters:

attr_name_overrides (Dict-like mapping from ObjectIdentifier to str) – Specify custom OID to name mappings, which can be used to match vendor-specific extensions.

class cryptography.x509.RelativeDistinguishedName(attributes)

New in version 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.

get_attributes_for_oid(oid)
Parameters:

oid – An ObjectIdentifier instance.

Returns:

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

rfc4514_string(attr_name_overrides=None)

New in version 2.5.

Changed in version 36.0: Added attr_name_overrides parameter.

Return str:

Format the given RDN set as a RFC 4514 Distinguished Name string.

Parameters:

attr_name_overrides (Dict-like mapping from ObjectIdentifier to str) – Specify custom OID to name mappings, which can be used to match vendor-specific extensions.

class cryptography.x509.ObjectIdentifier

New in version 0.8.

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

dotted_string
Type:

str

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

General Name Classes

class cryptography.x509.GeneralName

New in version 0.9.

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

class cryptography.x509.RFC822Name(value)

New in version 0.9.

Changed in version 3.1: U-label support has been removed. Encode them to A-label before use.

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

Parameters:

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

Raises:

ValueError – If the provided string is not an A-label.

value
Type:

str

class cryptography.x509.DNSName(value)

New in version 0.9.

Changed in version 3.1: U-label support has been removed. Encode them to A-label before use.

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

Parameters:

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

Raises:

ValueError –

If the provided string is not an A-label.

type:

str

value
Type:

str

class cryptography.x509.DirectoryName(value)

New in version 0.9.

This corresponds to a directory name.

value
Type:

Name

class cryptography.x509.UniformResourceIdentifier(value)

New in version 0.9.

Changed in version 3.1: U-label support has been removed. Encode them to A-label before use.

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

Parameters:

value – The URI. If it contains an internationalized domain name then it must be encoded to an A-label string before being passed.

Raises:

ValueError – If the provided string is not an A-label.

value
Type:

str

class cryptography.x509.IPAddress(value)

New in version 0.9.

This corresponds to an IP address.

value
Type:

IPv4Address, IPv6Address, IPv4Network, or IPv6Network.

class cryptography.x509.RegisteredID(value)

New in version 0.9.

This corresponds to a registered ID.

value
Type:

ObjectIdentifier

class cryptography.x509.OtherName(type_id, value)

New in version 1.0.

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

type_id
Type:

ObjectIdentifier

value
Type:

bytes

X.509 Extensions

class cryptography.x509.Extensions

New in version 0.9.

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

get_extension_for_oid(oid)
Parameters:

oid – An ObjectIdentifier instance.

Returns:

An instance of Extension.

Raises:

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

>>> 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)>)>
get_extension_for_class(extclass)

New in version 1.1.

Parameters:

extclass – An extension class.

Returns:

An instance of Extension.

Raises:

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

>>> 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)>)>
class cryptography.x509.Extension

New in version 0.9.

oid
Type:

ObjectIdentifier

One of the ExtensionOID OIDs.

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”.

value

Returns an instance of the extension type corresponding to the OID.

class cryptography.x509.ExtensionType

New in version 1.0.

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

oid
Type:

ObjectIdentifier

Returns the OID associated with the given extension type.

public_bytes()

New in version 36.0.

Return bytes:

A bytes string representing the extension’s DER encoded value.

class cryptography.x509.KeyUsage(digital_signature, content_commitment, key_encipherment, data_encipherment, key_agreement, key_cert_sign, crl_sign, encipher_only, decipher_only)

New in version 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.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns KEY_USAGE.

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).

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.

key_encipherment
Type:

bool

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

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.

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.

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 BasicConstraints extension.

crl_sign
Type:

bool

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

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.

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.

class cryptography.x509.BasicConstraints(ca, path_length)

New in version 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.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns BASIC_CONSTRAINTS.

ca
Type:

bool

Whether the certificate can sign certificates.

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.

class cryptography.x509.ExtendedKeyUsage(usages)

New in version 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 ExtendedKeyUsageOID OIDs present.

Parameters:

usages (list) – A list of ExtendedKeyUsageOID OIDs.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns EXTENDED_KEY_USAGE.

class cryptography.x509.OCSPNoCheck

New in version 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.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns OCSP_NO_CHECK.

class cryptography.x509.TLSFeature(features)

New in version 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.

Parameters:

features (list) – A list of features to enable from the TLSFeatureType enum. At this time only status_request or status_request_v2 are allowed.

oid
Type:

ObjectIdentifier

Returns TLS_FEATURE.

class cryptography.x509.TLSFeatureType

New in version 2.1.

An enumeration of TLS Feature types.

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.

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.

class cryptography.x509.NameConstraints(permitted_subtrees, excluded_subtrees)

New in version 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.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns NAME_CONSTRAINTS.

permitted_subtrees
Type:

list of 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.

excluded_subtrees
Type:

list of 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.

class cryptography.x509.AuthorityKeyIdentifier(key_identifier, authority_cert_issuer, authority_cert_serial_number)

New in version 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.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns AUTHORITY_KEY_IDENTIFIER.

key_identifier
Type:

bytes

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

authority_cert_issuer
Type:

A list of GeneralName instances or None

The GeneralName (one or multiple) of the issuer’s issuer.

authority_cert_serial_number
Type:

int or None

The serial number of the issuer’s issuer.

classmethod from_issuer_public_key(public_key)

New in version 1.0.

Note

This method should be used if the issuer certificate does not contain a SubjectKeyIdentifier. Otherwise, use 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 key_identifier, but authority_cert_issuer and 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.

Parameters:

public_key – One of RSAPublicKey, DSAPublicKey, EllipticCurvePublicKey, Ed25519PublicKey or Ed448PublicKey.

>>> from cryptography import x509
>>> issuer_cert = x509.load_pem_x509_certificate(pem_data)
>>> 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)

New in version 1.3.

Note

This method should be used if the issuer certificate contains a SubjectKeyIdentifier. Otherwise, use from_issuer_public_key().

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

Parameters:

ski – The SubjectKeyIdentifier from the issuer certificate.

>>> from cryptography import x509
>>> issuer_cert = x509.load_pem_x509_certificate(pem_data)
>>> ski_ext = issuer_cert.extensions.get_extension_for_class(x509.SubjectKeyIdentifier)
>>> x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier(ski_ext.value)
<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)>
class cryptography.x509.SubjectKeyIdentifier(digest)

New in version 0.9.

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

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns SUBJECT_KEY_IDENTIFIER.

key_identifier

New in version 35.0.0.

Type:

bytes

The binary value of the identifier.

digest
Type:

bytes

The binary value of the identifier. An alias of key_identifier.

classmethod from_public_key(public_key)

New in version 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.

Parameters:

public_key – One of RSAPublicKey, DSAPublicKey, EllipticCurvePublicKey, Ed25519PublicKey or Ed448PublicKey.

>>> from cryptography import x509
>>> csr = x509.load_pem_x509_csr(pem_req_data)
>>> x509.SubjectKeyIdentifier.from_public_key(csr.public_key())
<SubjectKeyIdentifier(digest=b'\x8c"\x98\xe2\xb5\xbf]\xe8*2\xf8\xd2\'?\x00\xd2\xc7#\xe4c')>
class cryptography.x509.SubjectAlternativeName(general_names)

New in version 0.9.

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

Parameters:

general_names (list) – A list of GeneralName instances.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns SUBJECT_ALTERNATIVE_NAME.

get_values_for_type(type)
Parameters:

type – A GeneralName instance. This is one of the general name classes.

Returns:

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

>>> from cryptography import x509
>>> from cryptography.hazmat.primitives import hashes
>>> cert = x509.load_pem_x509_certificate(cryptography_cert_pem)
>>> # 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']
class cryptography.x509.IssuerAlternativeName(general_names)

New in version 1.0.

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

Parameters:

general_names (list) – A list of GeneralName instances.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns ISSUER_ALTERNATIVE_NAME.

get_values_for_type(type)
Parameters:

type – A GeneralName instance. This is one of the general name classes.

Returns:

A list of values extracted from the matched general names.

class cryptography.x509.PrecertificateSignedCertificateTimestamps(scts)

New in version 2.0.

This extension contains 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 SignedCertificateTimestamp objects.

Parameters:

scts (list) – A list of SignedCertificateTimestamp objects.

oid
Type:

ObjectIdentifier

Returns PRECERT_SIGNED_CERTIFICATE_TIMESTAMPS.

class cryptography.x509.PrecertPoison

New in version 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 PrecertificateSignedCertificateTimestamps extension on the final certificate.

oid
Type:

ObjectIdentifier

Returns PRECERT_POISON.

class cryptography.x509.SignedCertificateTimestamps(scts)

New in version 3.0.

This extension contains SignedCertificateTimestamp instances. These can be used to verify that the certificate is included in a public Certificate Transparency log. This extension is only found in OCSP responses. For SCTs in an X.509 certificate see PrecertificateSignedCertificateTimestamps.

It is an iterable containing one or more SignedCertificateTimestamp objects.

Parameters:

scts (list) – A list of SignedCertificateTimestamp objects.

oid
Type:

ObjectIdentifier

Returns SIGNED_CERTIFICATE_TIMESTAMPS.

class cryptography.x509.DeltaCRLIndicator(crl_number)

New in version 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.

Parameters:

crl_number (int) – The CRL number of the complete CRL that the delta CRL is updating.

oid
Type:

ObjectIdentifier

Returns DELTA_CRL_INDICATOR.

crl_number
Type:

int

class cryptography.x509.AuthorityInformationAccess(descriptions)

New in version 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 AccessDescription instances.

Parameters:

descriptions (list) – A list of AccessDescription objects.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns AUTHORITY_INFORMATION_ACCESS.

class cryptography.x509.SubjectInformationAccess(descriptions)

New in version 3.0.

The subject information access extension indicates how to access information and services for the subject of the certificate in which the extension appears. When the subject is a CA, information and services may include certificate validation services and CA policy data. When the subject is an end entity, the information describes the type of services offered and how to access them. It is an iterable, containing one or more AccessDescription instances.

Parameters:

descriptions (list) – A list of AccessDescription objects.

oid
Type:

ObjectIdentifier

Returns SUBJECT_INFORMATION_ACCESS.

class cryptography.x509.AccessDescription(access_method, access_location)

New in version 0.9.

access_method
Type:

ObjectIdentifier

The access method defines what the access_location means. It must be OCSP or CA_ISSUERS when used with AuthorityInformationAccess or CA_REPOSITORY when used with SubjectInformationAccess.

If it is OCSP the access location will be where to obtain OCSP information for the certificate. If it is CA_ISSUERS the access location will provide additional information about the issuing certificate. Finally, if it is CA_REPOSITORY the access location will be the location of the CA’s repository.

access_location
Type:

GeneralName

Where to access the information defined by the access method.

class cryptography.x509.FreshestCRL(distribution_points)

New in version 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 DistributionPoint instances.

Parameters:

distribution_points (list) – A list of DistributionPoint instances.

oid
Type:

ObjectIdentifier

Returns FRESHEST_CRL.

class cryptography.x509.CRLDistributionPoints(distribution_points)

New in version 0.9.

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

Parameters:

distribution_points (list) – A list of DistributionPoint instances.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns CRL_DISTRIBUTION_POINTS.

class cryptography.x509.DistributionPoint(full_name, relative_name, reasons, crl_issuer)

New in version 0.9.

full_name
Type:

list of 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.

relative_name
Type:

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.

Changed in version 1.6: Changed from Name to RelativeDistinguishedName.

crl_issuer
Type:

list of GeneralName instances or None

Information about the issuer of the CRL.

reasons
Type:

frozenset of ReasonFlags or None

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

class cryptography.x509.ReasonFlags

New in version 0.9.

An enumeration for CRL reasons.

unspecified

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

key_compromise

This reason indicates that the private key was compromised.

ca_compromise

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

affiliation_changed

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

superseded

This reason indicates that a certificate has been superseded.

cessation_of_operation

This reason indicates that the certificate is no longer required.

certificate_hold

This reason indicates that the certificate is on hold.

privilege_withdrawn

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

aa_compromise

When an attribute authority has been compromised.

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 DistributionPoint.

class cryptography.x509.InhibitAnyPolicy(skip_certs)

New in version 1.0.

The inhibit anyPolicy extension indicates that the special OID ANY_POLICY, is not considered an explicit match for other 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 ANY_POLICY is no longer permitted. For example, a value of one indicates that ANY_POLICY may be processed in certificates issued by the subject of this certificate, but not in additional certificates in the path.

oid

New in version 1.0.

Type:

ObjectIdentifier

Returns INHIBIT_ANY_POLICY.

skip_certs
Type:

int

class cryptography.x509.PolicyConstraints

New in version 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.

oid
Type:

ObjectIdentifier

Returns POLICY_CONSTRAINTS.

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.

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.

class cryptography.x509.CRLNumber(crl_number)

New in version 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.

oid
Type:

ObjectIdentifier

Returns CRL_NUMBER.

crl_number
Type:

int

class cryptography.x509.IssuingDistributionPoint(full_name, relative_name, only_contains_user_certs, only_contains_ca_certs, only_some_reasons, indirect_crl, only_contains_attribute_certs)

New in version 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.

oid
Type:

ObjectIdentifier

Returns ISSUING_DISTRIBUTION_POINT.

only_contains_user_certs
Type:

bool

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

only_contains_ca_certs
Type:

bool

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

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.

only_contains_attribute_certs
Type:

bool

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

only_some_reasons
Type:

frozenset of ReasonFlags or None

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

full_name
Type:

list of 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.

relative_name
Type:

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.

class cryptography.x509.UnrecognizedExtension

New in version 1.2.

A generic extension class used to hold the raw value of extensions that cryptography does not know how to parse. This can also be used when creating new certificates, CRLs, or OCSP requests and responses to encode extensions that cryptography does not know how to generate.

oid
Type:

ObjectIdentifier

Returns the OID associated with this extension.

value
Type:

bytes

Returns the DER encoded bytes payload of the extension.

class cryptography.x509.CertificatePolicies(policies)

New in version 0.9.

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

Parameters:

policies (list) – A list of PolicyInformation instances.

As an example of how CertificatePolicies might be used, if you wanted to check if a certificated contained the CAB Forum’s “domain-validated” policy, you might write code like:

def contains_domain_validated(policies):
    return any(
        policy.oid.dotted_string == "2.23.140.1.2.1"
        for policy in policies
    )
oid

New in version 1.0.

Type:

ObjectIdentifier

Returns CERTIFICATE_POLICIES.

Certificate Policies Classes

These classes may be present within a CertificatePolicies instance.

class cryptography.x509.PolicyInformation(policy_identifier, policy_qualifiers)

New in version 0.9.

Contains a policy identifier and an optional list of qualifiers.

policy_identifier
Type:

ObjectIdentifier

policy_qualifiers
Type:

list

A list consisting of str and/or UserNotice objects. If the value is str 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.

class cryptography.x509.UserNotice(notice_reference, explicit_text)

New in version 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.

notice_reference
Type:

NoticeReference or None

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

explicit_text

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

Type:

str

class cryptography.x509.NoticeReference(organization, notice_numbers)

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.

New in version 0.9.

organization
Type:

str

notice_numbers
Type:

list

A list of integers.

CRL Entry Extensions

These extensions are only valid within a RevokedCertificate object.

class cryptography.x509.CertificateIssuer(general_names)

New in version 1.2.

The certificate issuer is an extension that is only valid inside 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.

Parameters:

general_names (list) – A list of GeneralName instances.

oid
Type:

ObjectIdentifier

Returns CERTIFICATE_ISSUER.

get_values_for_type(type)
Parameters:

type – A GeneralName instance. This is one of the general name classes.

Returns:

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

class cryptography.x509.CRLReason(reason)

New in version 1.2.

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

Parameters:

reason – An element from ReasonFlags.

oid
Type:

ObjectIdentifier

Returns CRL_REASON.

reason
Type:

An element from ReasonFlags

class cryptography.x509.InvalidityDate(invalidity_date)

New in version 1.2.

Invalidity date is an extension that is only valid inside 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.

Parameters:

invalidity_date – The datetime.datetime when it is known or suspected that the private key was compromised.

oid
Type:

ObjectIdentifier

Returns INVALIDITY_DATE.

invalidity_date
Type:

datetime.datetime

OCSP Extensions

class cryptography.x509.OCSPNonce(nonce)

New in version 2.4.

OCSP nonce is an extension that is only valid inside OCSPRequest and 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.

oid
Type:

ObjectIdentifier

Returns NONCE.

nonce
Type:

bytes

X.509 Request Attributes

class cryptography.x509.Attributes

New in version 36.0.

An Attributes instance is an ordered list of attributes. The object is iterable to get every attribute. Each returned element is an Attribute.

get_attribute_for_oid(oid)

New in version 36.0.

Parameters:

oid – An ObjectIdentifier instance.

Returns:

The Attribute or an exception if not found.

Raises:

cryptography.x509.AttributeNotFound – If the request does not have the attribute requested.

class cryptography.x509.Attribute

New in version 36.0.

An attribute associated with an X.509 request.

oid
Type:

ObjectIdentifier

Returns the object identifier for the attribute.

value
Type:

bytes

Returns the value of the attribute.

Object Identifiers

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

class cryptography.x509.oid.NameOID

These OIDs are typically seen in X.509 names.

New in version 1.0.

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 SubjectAlternativeName extension.

COUNTRY_NAME

Corresponds to the dotted string "2.5.4.6".

LOCALITY_NAME

Corresponds to the dotted string "2.5.4.7".

STATE_OR_PROVINCE_NAME

Corresponds to the dotted string "2.5.4.8".

STREET_ADDRESS

New in version 1.6.

Corresponds to the dotted string "2.5.4.9".

ORGANIZATION_NAME

Corresponds to the dotted string "2.5.4.10".

ORGANIZATIONAL_UNIT_NAME

Corresponds to the dotted string "2.5.4.11".

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 serial_number()).

SURNAME

Corresponds to the dotted string "2.5.4.4".

GIVEN_NAME

Corresponds to the dotted string "2.5.4.42".

TITLE

Corresponds to the dotted string "2.5.4.12".

GENERATION_QUALIFIER

Corresponds to the dotted string "2.5.4.44".

X500_UNIQUE_IDENTIFIER

New in version 1.6.

Corresponds to the dotted string "2.5.4.45".

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.

PSEUDONYM

Corresponds to the dotted string "2.5.4.65".

USER_ID

New in version 1.6.

Corresponds to the dotted string "0.9.2342.19200300.100.1.1".

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.

EMAIL_ADDRESS

Corresponds to the dotted string "1.2.840.113549.1.9.1".

JURISDICTION_COUNTRY_NAME

Corresponds to the dotted string "1.3.6.1.4.1.311.60.2.1.3".

JURISDICTION_LOCALITY_NAME

Corresponds to the dotted string "1.3.6.1.4.1.311.60.2.1.1".

JURISDICTION_STATE_OR_PROVINCE_NAME

Corresponds to the dotted string "1.3.6.1.4.1.311.60.2.1.2".

BUSINESS_CATEGORY

Corresponds to the dotted string "2.5.4.15".

POSTAL_ADDRESS

New in version 1.6.

Corresponds to the dotted string "2.5.4.16".

POSTAL_CODE

New in version 1.6.

Corresponds to the dotted string "2.5.4.17".

UNSTRUCTURED_NAME

New in version 3.0.

Corresponds to the dotted string "1.2.840.113549.1.9.2".

class cryptography.x509.oid.SignatureAlgorithmOID

New in version 1.0.

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.

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.

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.

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.

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.

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.

RSA_WITH_SHA3_224

Corresponds to the dotted string "2.16.840.1.101.3.4.3.13". This is a SHA3-224 digest signed by an RSA key.

RSA_WITH_SHA3_256

Corresponds to the dotted string "2.16.840.1.101.3.4.3.14". This is a SHA3-256 digest signed by an RSA key.

RSA_WITH_SHA3_384

Corresponds to the dotted string "2.16.840.1.101.3.4.3.15". This is a SHA3-384 digest signed by an RSA key.

RSA_WITH_SHA3_512

Corresponds to the dotted string "2.16.840.1.101.3.4.3.16". This is a SHA3-512 digest signed by an RSA key.

RSASSA_PSS

New in version 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.

ECDSA_WITH_SHA1

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

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.

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.

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.

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.

ECDSA_WITH_SHA3_224

Corresponds to the dotted string "2.16.840.1.101.3.4.3.9". This is a SHA3-224 digest signed by an ECDSA key.

ECDSA_WITH_SHA3_256

Corresponds to the dotted string "2.16.840.1.101.3.4.3.10". This is a SHA3-256 digest signed by an ECDSA key.

ECDSA_WITH_SHA3_384

Corresponds to the dotted string "2.16.840.1.101.3.4.3.11". This is a SHA3-384 digest signed by an ECDSA key.

ECDSA_WITH_SHA3_512

Corresponds to the dotted string "2.16.840.1.101.3.4.3.12". This is a SHA3-512 digest signed by an ECDSA key.

DSA_WITH_SHA1

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

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.

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.

DSA_WITH_SHA384

New in version 36.0.

Corresponds to the dotted string "2.16.840.1.101.3.4.3.3". This is a SHA384 digest signed by a DSA key.

DSA_WITH_SHA512

New in version 36.0.

Corresponds to the dotted string "2.16.840.1.101.3.4.3.4". This is a SHA512 digest signed by a DSA key.

ED25519

New in version 2.8.

Corresponds to the dotted string "1.3.101.112". This is a signature using an ed25519 key.

ED448

New in version 2.8.

Corresponds to the dotted string "1.3.101.113". This is a signature using an ed448 key.

class cryptography.x509.oid.ExtendedKeyUsageOID

New in version 1.0.

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.

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.

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.

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.

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.

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.

ANY_EXTENDED_KEY_USAGE

New in version 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. However, RFC 5280 additionally notes that applications that require the presence of a particular purpose _MAY_ reject certificates that include the anyExtendedKeyUsage OID but not the particular OID expected for the application. Therefore, the presence of this OID does not mean a given application will accept the certificate for all purposes.

SMARTCARD_LOGON

New in version 35.0.

Corresponds to the dotted string "1.3.6.1.4.1.311.20.2.2". This is used to denote that a certificate may be used for PKINIT access on Windows.

KERBEROS_PKINIT_KDC

New in version 35.0.

Corresponds to the dotted string "1.3.6.1.5.2.3.5". This is used to denote that a certificate may be used as a Kerberos domain controller certificate authorizing PKINIT access. For more information see RFC 4556.

IPSEC_IKE

New in version 37.0.

Corresponds to the dotted string "1.3.6.1.5.5.7.3.17". This is used to denote that a certificate may be assigned to an IPSEC SA, and can be used by the assignee to initiate an IPSec Internet Key Exchange. For more information see RFC 4945.

CERTIFICATE_TRANSPARENCY

New in version 38.0.

Corresponds to the dotted string "1.3.6.1.4.1.11129.2.4.4". This is used to denote that a certificate may be used as a pre-certificate signing certificate for Certificate Transparency log operation purposes. For more information see RFC 6962.

class cryptography.x509.oid.AuthorityInformationAccessOID

New in version 1.0.

OCSP

Corresponds to the dotted string "1.3.6.1.5.5.7.48.1". Used as the identifier for OCSP data in AccessDescription objects.

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 AccessDescription objects.

class cryptography.x509.oid.SubjectInformationAccessOID

New in version 3.0.

CA_REPOSITORY

Corresponds to the dotted string "1.3.6.1.5.5.7.48.5". Used as the identifier for CA repository data in AccessDescription objects.

class cryptography.x509.oid.CertificatePoliciesOID

New in version 1.0.

CPS_QUALIFIER

Corresponds to the dotted string "1.3.6.1.5.5.7.2.1".

CPS_USER_NOTICE

Corresponds to the dotted string "1.3.6.1.5.5.7.2.2".

ANY_POLICY

Corresponds to the dotted string "2.5.29.32.0".

class cryptography.x509.oid.ExtensionOID

New in version 1.0.

BASIC_CONSTRAINTS

Corresponds to the dotted string "2.5.29.19". The identifier for the BasicConstraints extension type.

KEY_USAGE

Corresponds to the dotted string "2.5.29.15". The identifier for the KeyUsage extension type.

SUBJECT_ALTERNATIVE_NAME

Corresponds to the dotted string "2.5.29.17". The identifier for the SubjectAlternativeName extension type.

ISSUER_ALTERNATIVE_NAME

Corresponds to the dotted string "2.5.29.18". The identifier for the IssuerAlternativeName extension type.

SUBJECT_KEY_IDENTIFIER

Corresponds to the dotted string "2.5.29.14". The identifier for the SubjectKeyIdentifier extension type.

NAME_CONSTRAINTS

Corresponds to the dotted string "2.5.29.30". The identifier for the NameConstraints extension type.

CRL_DISTRIBUTION_POINTS

Corresponds to the dotted string "2.5.29.31". The identifier for the CRLDistributionPoints extension type.

CERTIFICATE_POLICIES

Corresponds to the dotted string "2.5.29.32". The identifier for the CertificatePolicies extension type.

AUTHORITY_KEY_IDENTIFIER

Corresponds to the dotted string "2.5.29.35". The identifier for the AuthorityKeyIdentifier extension type.

EXTENDED_KEY_USAGE

Corresponds to the dotted string "2.5.29.37". The identifier for the ExtendedKeyUsage extension type.

AUTHORITY_INFORMATION_ACCESS

Corresponds to the dotted string "1.3.6.1.5.5.7.1.1". The identifier for the AuthorityInformationAccess extension type.

SUBJECT_INFORMATION_ACCESS

New in version 3.0.

Corresponds to the dotted string "1.3.6.1.5.5.7.1.11". The identifier for the SubjectInformationAccess extension type.

INHIBIT_ANY_POLICY

Corresponds to the dotted string "2.5.29.54". The identifier for the InhibitAnyPolicy extension type.

OCSP_NO_CHECK

Corresponds to the dotted string "1.3.6.1.5.5.7.48.1.5". The identifier for the OCSPNoCheck extension type.

TLS_FEATURE

Corresponds to the dotted string "1.3.6.1.5.5.7.1.24". The identifier for the TLSFeature extension type.

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.

DELTA_CRL_INDICATOR

New in version 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.

PRECERT_SIGNED_CERTIFICATE_TIMESTAMPS

New in version 1.9.

Corresponds to the dotted string "1.3.6.1.4.1.11129.2.4.2".

PRECERT_POISON

New in version 2.4.

Corresponds to the dotted string "1.3.6.1.4.1.11129.2.4.3".

SIGNED_CERTIFICATE_TIMESTAMPS

New in version 3.0.

Corresponds to the dotted string "1.3.6.1.4.1.11129.2.4.5".

POLICY_CONSTRAINTS

Corresponds to the dotted string "2.5.29.36". The identifier for the PolicyConstraints extension type.

FRESHEST_CRL

Corresponds to the dotted string "2.5.29.46". The identifier for the FreshestCRL extension type.

ISSUING_DISTRIBUTION_POINT

New in version 2.4.

Corresponds to the dotted string "2.5.29.28".

class cryptography.x509.oid.CRLEntryExtensionOID

New in version 1.2.

CERTIFICATE_ISSUER

Corresponds to the dotted string "2.5.29.29".

CRL_REASON

Corresponds to the dotted string "2.5.29.21".

INVALIDITY_DATE

Corresponds to the dotted string "2.5.29.24".

class cryptography.x509.oid.OCSPExtensionOID

New in version 2.4.

NONCE

Corresponds to the dotted string "1.3.6.1.5.5.7.48.1.2".

class cryptography.x509.oid.AttributeOID

New in version 3.0.

CHALLENGE_PASSWORD

Corresponds to the dotted string "1.2.840.113549.1.9.7".

UNSTRUCTURED_NAME

Corresponds to the dotted string "1.2.840.113549.1.9.2".

Helper Functions

cryptography.x509.random_serial_number()

New in version 1.6.

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

Exceptions

class cryptography.x509.InvalidVersion

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

parsed_version
Type:

int

Returns the raw version that was parsed from the certificate.

class cryptography.x509.DuplicateExtension

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

oid
Type:

ObjectIdentifier

Returns the OID.

class cryptography.x509.ExtensionNotFound

This is raised when calling Extensions.get_extension_for_oid() with an extension OID that is not present in the certificate.

oid
Type:

ObjectIdentifier

Returns the OID.

class cryptography.x509.AttributeNotFound

This is raised when calling Attributes.get_attribute_for_oid() with an attribute OID that is not present in the request.

oid
Type:

ObjectIdentifier

Returns the OID.

class cryptography.x509.UnsupportedGeneralNameType

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

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.