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# coding: utf-8
import itertools
from dataclasses import dataclass
from typing import FrozenSet, Iterable, Iterator, Optional, Union
from asn1crypto import cms, x509
from .asn1_types import AAControls
from .authority import (
Authority,
AuthorityWithCert,
CertTrustAnchor,
TrustAnchor,
)
from .util import get_ac_extension_value, get_issuer_dn
@dataclass(frozen=True)
class QualifiedPolicy:
issuer_domain_policy_id: str
"""
Policy OID in the issuer domain (i.e. as listed on the certificate).
"""
user_domain_policy_id: str
"""
Policy OID of the equivalent policy in the user domain.
"""
qualifiers: frozenset
"""
Set of x509.PolicyQualifierInfo objects.
"""
Leaf = Union[x509.Certificate, cms.AttributeCertificateV2]
class ValidationPath:
"""
Represents a path going towards an end-entity certificate or attribute
certificate.
"""
_qualified_policies: Optional[FrozenSet[QualifiedPolicy]] = None
_path_aa_controls = None
def __init__(
self,
trust_anchor: TrustAnchor,
interm: Iterable[x509.Certificate],
leaf: Optional[Leaf],
):
if interm and not leaf:
raise ValueError("Leafless paths cannot have intermediate certs")
self._interm = list(interm)
self._root = trust_anchor
self._leaf = leaf
@property
def trust_anchor(self) -> TrustAnchor:
return self._root
@property
def first(self):
"""
Returns the current beginning of the path - for a path to be complete,
this certificate should be a trust root
.. warning::
This is a compatibility property, and will return the first non-root
certificate if the trust root is not provisioned as a certificate.
If you want the trust root itself (even when it doesn't have a
certificate), use :attr:`trust_anchor`.
:return:
The first asn1crypto.x509.Certificate object in the path
"""
root = self._root.authority
if isinstance(root, AuthorityWithCert):
return root.certificate
elif self._interm:
return self._interm[0]
elif isinstance(self._leaf, x509.Certificate):
return self._leaf
@property
def leaf(self) -> Optional[Leaf]:
"""
Returns the current leaf certificate (AC or public-key).
The trust root's certificate will be returned if there is one and
there are no other certificates in the path.
If the trust root is certificate-less and there are no certificates,
the result will be ``None``.
"""
if self._leaf is not None:
return self._leaf
elif not self._interm and isinstance(self._root, CertTrustAnchor):
return self._root.certificate
# __init__ ensures that leaf None -> there are no intermediate certs
return None
def describe_leaf(self) -> Optional[str]:
leaf = self.leaf
if isinstance(leaf, x509.Certificate):
return leaf.subject.human_friendly
elif isinstance(leaf, cms.AttributeCertificateV2):
return '<Attribute certificate>'
else:
return None
def get_ee_cert_safe(self) -> Optional[x509.Certificate]:
"""
Returns the current leaf certificate if it is an X.509 public-key
certificate, and ``None`` otherwise.
:return:
"""
leaf = self.leaf
if isinstance(leaf, x509.Certificate):
return leaf
else:
return None
@property
def last(self) -> x509.Certificate:
"""
Returns the last certificate in the path if it is an X.509 public-key
certificate, and throws an error otherwise.
:return:
The last asn1crypto.x509.Certificate object in the path
"""
cert = self.get_ee_cert_safe()
if cert:
return cert
else:
raise LookupError
def iter_authorities(self) -> Iterable[Authority]:
"""
Iterate over all authorities in the path, including the trust root.
"""
yield self._root.authority
for cert in self._interm:
yield AuthorityWithCert(cert)
def find_issuing_authority(self, cert: Leaf):
"""
Return the issuer of the cert specified, as defined by this path
:param cert:
A certificate to get the issuer of
:raises:
LookupError - when the issuer of the certificate could not be found
:return:
An asn1crypto.x509.Certificate object of the issuer
"""
issuer_name = get_issuer_dn(cert)
if isinstance(cert, x509.Certificate):
aki = cert.authority_key_identifier
else:
aki_ext = get_ac_extension_value(cert, 'authority_key_identifier')
aki = aki_ext['key_identifier'].native if aki_ext else None
for authority in self.iter_authorities():
if authority.name == issuer_name:
keyid = authority.key_id
if keyid and aki and keyid != aki:
continue
return authority
raise LookupError(
'Unable to find the issuer of the certificate specified'
)
def truncate_to_and_append(self, cert: x509.Certificate, new_leaf: Leaf):
"""
Remove all certificates in the path after the cert specified and return
them in a new path.
Internal API.
:param cert:
An asn1crypto.x509.Certificate object to find
:param new_leaf:
A new leaf certificate to append.
:raises:
LookupError - when the certificate could not be found
:return:
The current ValidationPath object, for chaining
"""
if isinstance(self._root, CertTrustAnchor):
if self._root.certificate.issuer_serial == cert.issuer_serial:
return ValidationPath(self._root, interm=[], leaf=new_leaf)
certs = self._interm
cert_index = None
for index, entry in enumerate(certs):
if entry.issuer_serial == cert.issuer_serial:
cert_index = index
break
if cert_index is None:
raise LookupError('Unable to find the certificate specified')
return ValidationPath(
self._root, interm=certs[: cert_index + 1], leaf=new_leaf
)
# TODO generalise this to ACs as well?
def truncate_to_issuer_and_append(self, cert: x509.Certificate):
"""
Remove all certificates in the path after the issuer of the cert
specified, as defined by this path, and append a new one.
Internal API.
:param cert:
A new leaf certificate to append.
:raises:
LookupError - when the issuer of the certificate could not be found
:return:
The current ValidationPath object, for chaining
"""
issuer_index = None
# check the trust root separately
if self.trust_anchor.authority.is_potential_issuer_of(cert):
# in case of a match, truncate everything
if cert.self_signed == 'maybe':
# if the candidate leaf is self-signed (according to metadata),
# then it's actually the authority itself -> no need to append.
return ValidationPath(self._root, interm=[], leaf=None)
else:
return ValidationPath(self._root, interm=[], leaf=cert)
# now run through the rest of the path
certs = self._interm
for index, entry in enumerate(certs):
if entry.subject == cert.issuer:
if entry.key_identifier and cert.authority_key_identifier:
if entry.key_identifier == cert.authority_key_identifier:
issuer_index = index
break
else:
issuer_index = index
break
if issuer_index is None:
raise LookupError(
'Unable to find the issuer of the certificate specified'
)
return ValidationPath(self._root, certs[: issuer_index + 1], leaf=cert)
def copy_and_append(self, cert: Leaf):
new_certs = self._interm[:]
if self._leaf:
new_certs.append(self._leaf)
return ValidationPath(
trust_anchor=self._root, interm=new_certs, leaf=cert
)
def copy_and_drop_leaf(self) -> 'ValidationPath':
"""
Drop the leaf cert from this path and return a new path with the
last intermediate certificate set as the leaf.
"""
if len(self._interm) == 0:
raise IndexError
new_interm, new_leaf = self._interm[:-1], self._interm[-1]
return ValidationPath(
trust_anchor=self._root, interm=new_interm, leaf=new_leaf
)
def _set_qualified_policies(self, policies):
self._qualified_policies = policies
def qualified_policies(self) -> Optional[FrozenSet[QualifiedPolicy]]:
return self._qualified_policies
def aa_attr_in_scope(self, attr_id: cms.AttCertAttributeType) -> bool:
aa_controls_extensions = [
AAControls.read_extension_value(cert) for cert in self
]
aa_controls_used = any(x is not None for x in aa_controls_extensions)
if not aa_controls_used:
return True
else:
# the path validation code ensures that all non-anchor certs
# have an AAControls extension, but we still enforce the root's
# AAControls if there is one (since we might as well treat it
# as a configuration setting/failsafe at that point)
# This is appropriate in PKIX-land (see RFC 5280, § 6.2 as
# updated in RFC 6818, § 4)
return all(
ctrl.accept(attr_id)
for ctrl in aa_controls_extensions
# None check for defensiveness (already enforced by validation
# algorithm), and to (potentially) skip the root
if ctrl is not None
)
@property
def pkix_len(self):
return len(self._interm) + (1 if self._leaf else 0)
def __len__(self):
# backwards compat
return 1 + self.pkix_len
def __getitem__(self, key):
# convoluted because of compatibility issues...
if key > 0:
leaf_ix = len(self._interm) + 1
if key == leaf_ix and self._leaf is not None:
return self._leaf
return self._interm[key - 1]
elif isinstance(self._root, CertTrustAnchor):
# backwards compat
return self._root.certificate
else:
# Throw an error instead of returning None, because we want this
# to fail loudly.
raise LookupError("Root has no certificate")
def iter_certs(self, include_root: bool) -> Iterator[x509.Certificate]:
"""
Iterate over the certificates in the path.
:param include_root:
Include the root (if it is supplied as a certificate)
:return:
An iterator.
"""
root = self._root.authority
from_root = (
(root.certificate,)
if include_root and isinstance(root, AuthorityWithCert)
else ()
)
leaf = self._leaf
from_leaf = (leaf,) if isinstance(leaf, x509.Certificate) else ()
return itertools.chain(from_root, self._interm, from_leaf)
def __iter__(self):
# backwards compat, we iterate over all certs _including_ the root
# if it is supplied as a cert
return self.iter_certs(include_root=True)
def __eq__(self, other):
if not isinstance(other, ValidationPath):
return False
return (
self.trust_anchor == other.trust_anchor
and self._interm == other._interm
and self._leaf == other._leaf
)
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