# coding: utf-8
"""
ASN.1 type classes for certificate revocation lists (CRL). Exports the
following items:
- CertificateList()
Other type classes are defined that help compose the types listed above.
"""
from __future__ import unicode_literals, division, absolute_import, print_function
import hashlib
from .algos import SignedDigestAlgorithm
from .core import (
Boolean,
Enumerated,
GeneralizedTime,
Integer,
ObjectIdentifier,
OctetBitString,
ParsableOctetString,
Sequence,
SequenceOf,
)
from .x509 import (
AuthorityInfoAccessSyntax,
AuthorityKeyIdentifier,
CRLDistributionPoints,
DistributionPointName,
GeneralNames,
Name,
ReasonFlags,
Time,
)
# The structures in this file are taken from https://tools.ietf.org/html/rfc5280
class Version(Integer):
_map = {
0: 'v1',
1: 'v2',
2: 'v3',
}
class IssuingDistributionPoint(Sequence):
_fields = [
('distribution_point', DistributionPointName, {'explicit': 0, 'optional': True}),
('only_contains_user_certs', Boolean, {'implicit': 1, 'default': False}),
('only_contains_ca_certs', Boolean, {'implicit': 2, 'default': False}),
('only_some_reasons', ReasonFlags, {'implicit': 3, 'optional': True}),
('indirect_crl', Boolean, {'implicit': 4, 'default': False}),
('only_contains_attribute_certs', Boolean, {'implicit': 5, 'default': False}),
]
class TBSCertListExtensionId(ObjectIdentifier):
_map = {
'2.5.29.18': 'issuer_alt_name',
'2.5.29.20': 'crl_number',
'2.5.29.27': 'delta_crl_indicator',
'2.5.29.28': 'issuing_distribution_point',
'2.5.29.35': 'authority_key_identifier',
'2.5.29.46': 'freshest_crl',
'1.3.6.1.5.5.7.1.1': 'authority_information_access',
}
class TBSCertListExtension(Sequence):
_fields = [
('extn_id', TBSCertListExtensionId),
('critical', Boolean, {'default': False}),
('extn_value', ParsableOctetString),
]
_oid_pair = ('extn_id', 'extn_value')
_oid_specs = {
'issuer_alt_name': GeneralNames,
'crl_number': Integer,
'delta_crl_indicator': Integer,
'issuing_distribution_point': IssuingDistributionPoint,
'authority_key_identifier': AuthorityKeyIdentifier,
'freshest_crl': CRLDistributionPoints,
'authority_information_access': AuthorityInfoAccessSyntax,
}
class TBSCertListExtensions(SequenceOf):
_child_spec = TBSCertListExtension
class CRLReason(Enumerated):
_map = {
0: 'unspecified',
1: 'key_compromise',
2: 'ca_compromise',
3: 'affiliation_changed',
4: 'superseded',
5: 'cessation_of_operation',
6: 'certificate_hold',
8: 'remove_from_crl',
9: 'privilege_withdrawn',
10: 'aa_compromise',
}
@property
def human_friendly(self):
"""
:return:
A unicode string with revocation description that is suitable to
show to end-users. Starts with a lower case letter and phrased in
such a way that it makes sense after the phrase "because of" or
"due to".
"""
return {
'unspecified': 'an unspecified reason',
'key_compromise': 'a compromised key',
'ca_compromise': 'the CA being compromised',
'affiliation_changed': 'an affiliation change',
'superseded': 'certificate supersession',
'cessation_of_operation': 'a cessation of operation',
'certificate_hold': 'a certificate hold',
'remove_from_crl': 'removal from the CRL',
'privilege_withdrawn': 'privilege withdrawl',
'aa_compromise': 'the AA being compromised',
}[self.native]
class CRLEntryExtensionId(ObjectIdentifier):
_map = {
'2.5.29.21': 'crl_reason',
'2.5.29.23': 'hold_instruction_code',
'2.5.29.24': 'invalidity_date',
'2.5.29.29': 'certificate_issuer',
}
class CRLEntryExtension(Sequence):
_fields = [
('extn_id', CRLEntryExtensionId),
('critical', Boolean, {'default': False}),
('extn_value', ParsableOctetString),
]
_oid_pair = ('extn_id', 'extn_value')
_oid_specs = {
'crl_reason': CRLReason,
'hold_instruction_code': ObjectIdentifier,
'invalidity_date': GeneralizedTime,
'certificate_issuer': GeneralNames,
}
class CRLEntryExtensions(SequenceOf):
_child_spec = CRLEntryExtension
class RevokedCertificate(Sequence):
_fields = [
('user_certificate', Integer),
('revocation_date', Time),
('crl_entry_extensions', CRLEntryExtensions, {'optional': True}),
]
_processed_extensions = False
_critical_extensions = None
_crl_reason_value = None
_invalidity_date_value = None
_certificate_issuer_value = None
_issuer_name = False
def _set_extensions(self):
"""
Sets common named extensions to private attributes and creates a list
of critical extensions
"""
self._critical_extensions = set()
for extension in self['crl_entry_extensions']:
name = extension['extn_id'].native
attribute_name = '_%s_value' % name
if hasattr(self, attribute_name):
setattr(self, attribute_name, extension['extn_value'].parsed)
if extension['critical'].native:
self._critical_extensions.add(name)
self._processed_extensions = True
@property
def critical_extensions(self):
"""
Returns a set of the names (or OID if not a known extension) of the
extensions marked as critical
:return:
A set of unicode strings
"""
if not self._processed_extensions:
self._set_extensions()
return self._critical_extensions
@property
def crl_reason_value(self):
"""
This extension indicates the reason that a certificate was revoked.
:return:
None or a CRLReason object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._crl_reason_value
@property
def invalidity_date_value(self):
"""
This extension indicates the suspected date/time the private key was
compromised or the certificate became invalid. This would usually be
before the revocation date, which is when the CA processed the
revocation.
:return:
None or a GeneralizedTime object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._invalidity_date_value
@property
def certificate_issuer_value(self):
"""
This extension indicates the issuer of the certificate in question,
and is used in indirect CRLs. CRL entries without this extension are
for certificates issued from the last seen issuer.
:return:
None or an x509.GeneralNames object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._certificate_issuer_value
@property
def issuer_name(self):
"""
:return:
None, or an asn1crypto.x509.Name object for the issuer of the cert
"""
if self._issuer_name is False:
self._issuer_name = None
if self.certificate_issuer_value:
for general_name in self.certificate_issuer_value:
if general_name.name == 'directory_name':
self._issuer_name = general_name.chosen
break
return self._issuer_name
class RevokedCertificates(SequenceOf):
_child_spec = RevokedCertificate
class TbsCertList(Sequence):
_fields = [
('version', Version, {'optional': True}),
('signature', SignedDigestAlgorithm),
('issuer', Name),
('this_update', Time),
('next_update', Time, {'optional': True}),
('revoked_certificates', RevokedCertificates, {'optional': True}),
('crl_extensions', TBSCertListExtensions, {'explicit': 0, 'optional': True}),
]
class CertificateList(Sequence):
_fields = [
('tbs_cert_list', TbsCertList),
('signature_algorithm', SignedDigestAlgorithm),
('signature', OctetBitString),
]
_processed_extensions = False
_critical_extensions = None
_issuer_alt_name_value = None
_crl_number_value = None
_delta_crl_indicator_value = None
_issuing_distribution_point_value = None
_authority_key_identifier_value = None
_freshest_crl_value = None
_authority_information_access_value = None
_issuer_cert_urls = None
_delta_crl_distribution_points = None
_sha1 = None
_sha256 = None
def _set_extensions(self):
"""
Sets common named extensions to private attributes and creates a list
of critical extensions
"""
self._critical_extensions = set()
for extension in self['tbs_cert_list']['crl_extensions']:
name = extension['extn_id'].native
attribute_name = '_%s_value' % name
if hasattr(self, attribute_name):
setattr(self, attribute_name, extension['extn_value'].parsed)
if extension['critical'].native:
self._critical_extensions.add(name)
self._processed_extensions = True
@property
def critical_extensions(self):
"""
Returns a set of the names (or OID if not a known extension) of the
extensions marked as critical
:return:
A set of unicode strings
"""
if not self._processed_extensions:
self._set_extensions()
return self._critical_extensions
@property
def issuer_alt_name_value(self):
"""
This extension allows associating one or more alternative names with
the issuer of the CRL.
:return:
None or an x509.GeneralNames object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._issuer_alt_name_value
@property
def crl_number_value(self):
"""
This extension adds a monotonically increasing number to the CRL and is
used to distinguish different versions of the CRL.
:return:
None or an Integer object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._crl_number_value
@property
def delta_crl_indicator_value(self):
"""
This extension indicates a CRL is a delta CRL, and contains the CRL
number of the base CRL that it is a delta from.
:return:
None or an Integer object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._delta_crl_indicator_value
@property
def issuing_distribution_point_value(self):
"""
This extension includes information about what types of revocations
and certificates are part of the CRL.
:return:
None or an IssuingDistributionPoint object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._issuing_distribution_point_value
@property
def authority_key_identifier_value(self):
"""
This extension helps in identifying the public key with which to
validate the authenticity of the CRL.
:return:
None or an AuthorityKeyIdentifier object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._authority_key_identifier_value
@property
def freshest_crl_value(self):
"""
This extension is used in complete CRLs to indicate where a delta CRL
may be located.
:return:
None or a CRLDistributionPoints object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._freshest_crl_value
@property
def authority_information_access_value(self):
"""
This extension is used to provide a URL with which to download the
certificate used to sign this CRL.
:return:
None or an AuthorityInfoAccessSyntax object
"""
if self._processed_extensions is False:
self._set_extensions()
return self._authority_information_access_value
@property
def issuer(self):
"""
:return:
An asn1crypto.x509.Name object for the issuer of the CRL
"""
return self['tbs_cert_list']['issuer']
@property
def authority_key_identifier(self):
"""
:return:
None or a byte string of the key_identifier from the authority key
identifier extension
"""
if not self.authority_key_identifier_value:
return None
return self.authority_key_identifier_value['key_identifier'].native
@property
def issuer_cert_urls(self):
"""
:return:
A list of unicode strings that are URLs that should contain either
an individual DER-encoded X.509 certificate, or a DER-encoded CMS
message containing multiple certificates
"""
if self._issuer_cert_urls is None:
self._issuer_cert_urls = []
if self.authority_information_access_value:
for entry in self.authority_information_access_value:
if entry['access_method'].native == 'ca_issuers':
location = entry['access_location']
if location.name != 'uniform_resource_identifier':
continue
url = location.native
if url.lower()[0:7] == 'http://':
self._issuer_cert_urls.append(url)
return self._issuer_cert_urls
@property
def delta_crl_distribution_points(self):
"""
Returns delta CRL URLs - only applies to complete CRLs
:return:
A list of zero or more DistributionPoint objects
"""
if self._delta_crl_distribution_points is None:
self._delta_crl_distribution_points = []
if self.freshest_crl_value is not None:
for distribution_point in self.freshest_crl_value:
distribution_point_name = distribution_point['distribution_point']
# RFC 5280 indicates conforming CA should not use the relative form
if distribution_point_name.name == 'name_relative_to_crl_issuer':
continue
# This library is currently only concerned with HTTP-based CRLs
for general_name in distribution_point_name.chosen:
if general_name.name == 'uniform_resource_identifier':
self._delta_crl_distribution_points.append(distribution_point)
return self._delta_crl_distribution_points
@property
def signature(self):
"""
:return:
A byte string of the signature
"""
return self['signature'].native
@property
def sha1(self):
"""
:return:
The SHA1 hash of the DER-encoded bytes of this certificate list
"""
if self._sha1 is None:
self._sha1 = hashlib.sha1(self.dump()).digest()
return self._sha1
@property
def sha256(self):
"""
:return:
The SHA-256 hash of the DER-encoded bytes of this certificate list
"""
if self._sha256 is None:
self._sha256 = hashlib.sha256(self.dump()).digest()
return self._sha256