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# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.
from __future__ import annotations
import email.base64mime
import email.generator
import email.message
import email.policy
import io
import typing
from cryptography import utils, x509
from cryptography.hazmat.bindings._rust import pkcs7 as rust_pkcs7
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.hazmat.primitives.asymmetric import ec, rsa
from cryptography.utils import _check_byteslike
def load_pem_pkcs7_certificates(data: bytes) -> typing.List[x509.Certificate]:
from cryptography.hazmat.backends.openssl.backend import backend
return backend.load_pem_pkcs7_certificates(data)
def load_der_pkcs7_certificates(data: bytes) -> typing.List[x509.Certificate]:
from cryptography.hazmat.backends.openssl.backend import backend
return backend.load_der_pkcs7_certificates(data)
def serialize_certificates(
certs: typing.List[x509.Certificate],
encoding: serialization.Encoding,
) -> bytes:
return rust_pkcs7.serialize_certificates(certs, encoding)
PKCS7HashTypes = typing.Union[
hashes.SHA224,
hashes.SHA256,
hashes.SHA384,
hashes.SHA512,
]
PKCS7PrivateKeyTypes = typing.Union[
rsa.RSAPrivateKey, ec.EllipticCurvePrivateKey
]
class PKCS7Options(utils.Enum):
Text = "Add text/plain MIME type"
Binary = "Don't translate input data into canonical MIME format"
DetachedSignature = "Don't embed data in the PKCS7 structure"
NoCapabilities = "Don't embed SMIME capabilities"
NoAttributes = "Don't embed authenticatedAttributes"
NoCerts = "Don't embed signer certificate"
class PKCS7SignatureBuilder:
def __init__(
self,
data: typing.Optional[bytes] = None,
signers: typing.List[
typing.Tuple[
x509.Certificate,
PKCS7PrivateKeyTypes,
PKCS7HashTypes,
]
] = [],
additional_certs: typing.List[x509.Certificate] = [],
):
self._data = data
self._signers = signers
self._additional_certs = additional_certs
def set_data(self, data: bytes) -> PKCS7SignatureBuilder:
_check_byteslike("data", data)
if self._data is not None:
raise ValueError("data may only be set once")
return PKCS7SignatureBuilder(data, self._signers)
def add_signer(
self,
certificate: x509.Certificate,
private_key: PKCS7PrivateKeyTypes,
hash_algorithm: PKCS7HashTypes,
) -> PKCS7SignatureBuilder:
if not isinstance(
hash_algorithm,
(
hashes.SHA224,
hashes.SHA256,
hashes.SHA384,
hashes.SHA512,
),
):
raise TypeError(
"hash_algorithm must be one of hashes.SHA224, "
"SHA256, SHA384, or SHA512"
)
if not isinstance(certificate, x509.Certificate):
raise TypeError("certificate must be a x509.Certificate")
if not isinstance(
private_key, (rsa.RSAPrivateKey, ec.EllipticCurvePrivateKey)
):
raise TypeError("Only RSA & EC keys are supported at this time.")
return PKCS7SignatureBuilder(
self._data,
self._signers + [(certificate, private_key, hash_algorithm)],
)
def add_certificate(
self, certificate: x509.Certificate
) -> PKCS7SignatureBuilder:
if not isinstance(certificate, x509.Certificate):
raise TypeError("certificate must be a x509.Certificate")
return PKCS7SignatureBuilder(
self._data, self._signers, self._additional_certs + [certificate]
)
def sign(
self,
encoding: serialization.Encoding,
options: typing.Iterable[PKCS7Options],
backend: typing.Any = None,
) -> bytes:
if len(self._signers) == 0:
raise ValueError("Must have at least one signer")
if self._data is None:
raise ValueError("You must add data to sign")
options = list(options)
if not all(isinstance(x, PKCS7Options) for x in options):
raise ValueError("options must be from the PKCS7Options enum")
if encoding not in (
serialization.Encoding.PEM,
serialization.Encoding.DER,
serialization.Encoding.SMIME,
):
raise ValueError(
"Must be PEM, DER, or SMIME from the Encoding enum"
)
# Text is a meaningless option unless it is accompanied by
# DetachedSignature
if (
PKCS7Options.Text in options
and PKCS7Options.DetachedSignature not in options
):
raise ValueError(
"When passing the Text option you must also pass "
"DetachedSignature"
)
if PKCS7Options.Text in options and encoding in (
serialization.Encoding.DER,
serialization.Encoding.PEM,
):
raise ValueError(
"The Text option is only available for SMIME serialization"
)
# No attributes implies no capabilities so we'll error if you try to
# pass both.
if (
PKCS7Options.NoAttributes in options
and PKCS7Options.NoCapabilities in options
):
raise ValueError(
"NoAttributes is a superset of NoCapabilities. Do not pass "
"both values."
)
return rust_pkcs7.sign_and_serialize(self, encoding, options)
def _smime_encode(
data: bytes, signature: bytes, micalg: str, text_mode: bool
) -> bytes:
# This function works pretty hard to replicate what OpenSSL does
# precisely. For good and for ill.
m = email.message.Message()
m.add_header("MIME-Version", "1.0")
m.add_header(
"Content-Type",
"multipart/signed",
protocol="application/x-pkcs7-signature",
micalg=micalg,
)
m.preamble = "This is an S/MIME signed message\n"
msg_part = OpenSSLMimePart()
msg_part.set_payload(data)
if text_mode:
msg_part.add_header("Content-Type", "text/plain")
m.attach(msg_part)
sig_part = email.message.MIMEPart()
sig_part.add_header(
"Content-Type", "application/x-pkcs7-signature", name="smime.p7s"
)
sig_part.add_header("Content-Transfer-Encoding", "base64")
sig_part.add_header(
"Content-Disposition", "attachment", filename="smime.p7s"
)
sig_part.set_payload(
email.base64mime.body_encode(signature, maxlinelen=65)
)
del sig_part["MIME-Version"]
m.attach(sig_part)
fp = io.BytesIO()
g = email.generator.BytesGenerator(
fp,
maxheaderlen=0,
mangle_from_=False,
policy=m.policy.clone(linesep="\r\n"),
)
g.flatten(m)
return fp.getvalue()
class OpenSSLMimePart(email.message.MIMEPart):
# A MIMEPart subclass that replicates OpenSSL's behavior of not including
# a newline if there are no headers.
def _write_headers(self, generator) -> None:
if list(self.raw_items()):
generator._write_headers(self)
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