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"""Crypto utilities."""
import binascii
import contextlib
import logging
import os
import re
import socket
from typing import Callable
from typing import Tuple
from typing import Union
import josepy as jose
from OpenSSL import crypto
from OpenSSL import SSL # type: ignore # https://github.com/python/typeshed/issues/2052
from acme import errors
logger = logging.getLogger(__name__)
# Default SSL method selected here is the most compatible, while secure
# SSL method: TLSv1_METHOD is only compatible with
# TLSv1_METHOD, while SSLv23_METHOD is compatible with all other
# methods, including TLSv2_METHOD (read more at
# https://www.openssl.org/docs/ssl/SSLv23_method.html). _serve_sni
# should be changed to use "set_options" to disable SSLv2 and SSLv3,
# in case it's used for things other than probing/serving!
_DEFAULT_SSL_METHOD = SSL.SSLv23_METHOD # type: ignore
class _DefaultCertSelection:
def __init__(self, certs):
self.certs = certs
def __call__(self, connection):
server_name = connection.get_servername()
return self.certs.get(server_name, None)
class SSLSocket: # pylint: disable=too-few-public-methods
"""SSL wrapper for sockets.
:ivar socket sock: Original wrapped socket.
:ivar dict certs: Mapping from domain names (`bytes`) to
`OpenSSL.crypto.X509`.
:ivar method: See `OpenSSL.SSL.Context` for allowed values.
:ivar alpn_selection: Hook to select negotiated ALPN protocol for
connection.
:ivar cert_selection: Hook to select certificate for connection. If given,
`certs` parameter would be ignored, and therefore must be empty.
"""
def __init__(self, sock, certs=None,
method=_DEFAULT_SSL_METHOD, alpn_selection=None,
cert_selection=None):
self.sock = sock
self.alpn_selection = alpn_selection
self.method = method
if not cert_selection and not certs:
raise ValueError("Neither cert_selection or certs specified.")
if cert_selection and certs:
raise ValueError("Both cert_selection and certs specified.")
if cert_selection is None:
cert_selection = _DefaultCertSelection(certs)
self.cert_selection = cert_selection
def __getattr__(self, name):
return getattr(self.sock, name)
def _pick_certificate_cb(self, connection):
"""SNI certificate callback.
This method will set a new OpenSSL context object for this
connection when an incoming connection provides an SNI name
(in order to serve the appropriate certificate, if any).
:param connection: The TLS connection object on which the SNI
extension was received.
:type connection: :class:`OpenSSL.Connection`
"""
pair = self.cert_selection(connection)
if pair is None:
logger.debug("Certificate selection for server name %s failed, dropping SSL",
connection.get_servername())
return
key, cert = pair
new_context = SSL.Context(self.method)
new_context.set_options(SSL.OP_NO_SSLv2)
new_context.set_options(SSL.OP_NO_SSLv3)
new_context.use_privatekey(key)
new_context.use_certificate(cert)
if self.alpn_selection is not None:
new_context.set_alpn_select_callback(self.alpn_selection)
connection.set_context(new_context)
class FakeConnection:
"""Fake OpenSSL.SSL.Connection."""
# pylint: disable=missing-function-docstring
def __init__(self, connection):
self._wrapped = connection
def __getattr__(self, name):
return getattr(self._wrapped, name)
def shutdown(self, *unused_args):
# OpenSSL.SSL.Connection.shutdown doesn't accept any args
return self._wrapped.shutdown()
def accept(self): # pylint: disable=missing-function-docstring
sock, addr = self.sock.accept()
context = SSL.Context(self.method)
context.set_options(SSL.OP_NO_SSLv2)
context.set_options(SSL.OP_NO_SSLv3)
context.set_tlsext_servername_callback(self._pick_certificate_cb)
if self.alpn_selection is not None:
context.set_alpn_select_callback(self.alpn_selection)
ssl_sock = self.FakeConnection(SSL.Connection(context, sock))
ssl_sock.set_accept_state()
logger.debug("Performing handshake with %s", addr)
try:
ssl_sock.do_handshake()
except SSL.Error as error:
# _pick_certificate_cb might have returned without
# creating SSL context (wrong server name)
raise socket.error(error)
return ssl_sock, addr
def probe_sni(name, host, port=443, timeout=300, # pylint: disable=too-many-arguments
method=_DEFAULT_SSL_METHOD, source_address=('', 0),
alpn_protocols=None):
"""Probe SNI server for SSL certificate.
:param bytes name: Byte string to send as the server name in the
client hello message.
:param bytes host: Host to connect to.
:param int port: Port to connect to.
:param int timeout: Timeout in seconds.
:param method: See `OpenSSL.SSL.Context` for allowed values.
:param tuple source_address: Enables multi-path probing (selection
of source interface). See `socket.creation_connection` for more
info. Available only in Python 2.7+.
:param alpn_protocols: Protocols to request using ALPN.
:type alpn_protocols: `list` of `bytes`
:raises acme.errors.Error: In case of any problems.
:returns: SSL certificate presented by the server.
:rtype: OpenSSL.crypto.X509
"""
context = SSL.Context(method)
context.set_timeout(timeout)
socket_kwargs = {'source_address': source_address}
try:
logger.debug(
"Attempting to connect to %s:%d%s.", host, port,
" from {0}:{1}".format(
source_address[0],
source_address[1]
) if any(source_address) else ""
)
socket_tuple: Tuple[str, int] = (host, port)
sock = socket.create_connection(socket_tuple, **socket_kwargs) # type: ignore
except socket.error as error:
raise errors.Error(error)
with contextlib.closing(sock) as client:
client_ssl = SSL.Connection(context, client)
client_ssl.set_connect_state()
client_ssl.set_tlsext_host_name(name) # pyOpenSSL>=0.13
if alpn_protocols is not None:
client_ssl.set_alpn_protos(alpn_protocols)
try:
client_ssl.do_handshake()
client_ssl.shutdown()
except SSL.Error as error:
raise errors.Error(error)
return client_ssl.get_peer_certificate()
def make_csr(private_key_pem, domains, must_staple=False):
"""Generate a CSR containing a list of domains as subjectAltNames.
:param buffer private_key_pem: Private key, in PEM PKCS#8 format.
:param list domains: List of DNS names to include in subjectAltNames of CSR.
:param bool must_staple: Whether to include the TLS Feature extension (aka
OCSP Must Staple: https://tools.ietf.org/html/rfc7633).
:returns: buffer PEM-encoded Certificate Signing Request.
"""
private_key = crypto.load_privatekey(
crypto.FILETYPE_PEM, private_key_pem)
csr = crypto.X509Req()
extensions = [
crypto.X509Extension(
b'subjectAltName',
critical=False,
value=', '.join('DNS:' + d for d in domains).encode('ascii')
),
]
if must_staple:
extensions.append(crypto.X509Extension(
b"1.3.6.1.5.5.7.1.24",
critical=False,
value=b"DER:30:03:02:01:05"))
csr.add_extensions(extensions)
csr.set_pubkey(private_key)
csr.set_version(2)
csr.sign(private_key, 'sha256')
return crypto.dump_certificate_request(
crypto.FILETYPE_PEM, csr)
def _pyopenssl_cert_or_req_all_names(loaded_cert_or_req):
common_name = loaded_cert_or_req.get_subject().CN
sans = _pyopenssl_cert_or_req_san(loaded_cert_or_req)
if common_name is None:
return sans
return [common_name] + [d for d in sans if d != common_name]
def _pyopenssl_cert_or_req_san(cert_or_req):
"""Get Subject Alternative Names from certificate or CSR using pyOpenSSL.
.. todo:: Implement directly in PyOpenSSL!
.. note:: Although this is `acme` internal API, it is used by
`letsencrypt`.
:param cert_or_req: Certificate or CSR.
:type cert_or_req: `OpenSSL.crypto.X509` or `OpenSSL.crypto.X509Req`.
:returns: A list of Subject Alternative Names.
:rtype: `list` of `unicode`
"""
# This function finds SANs by dumping the certificate/CSR to text and
# searching for "X509v3 Subject Alternative Name" in the text. This method
# is used to support PyOpenSSL version 0.13 where the
# `_subjectAltNameString` and `get_extensions` methods are not available
# for CSRs.
# constants based on PyOpenSSL certificate/CSR text dump
part_separator = ":"
parts_separator = ", "
prefix = "DNS" + part_separator
if isinstance(cert_or_req, crypto.X509):
# pylint: disable=line-too-long
func: Union[Callable[[int, crypto.X509Req], bytes], Callable[[int, crypto.X509], bytes]] = crypto.dump_certificate
else:
func = crypto.dump_certificate_request
text = func(crypto.FILETYPE_TEXT, cert_or_req).decode("utf-8")
# WARNING: this function does not support multiple SANs extensions.
# Multiple X509v3 extensions of the same type is disallowed by RFC 5280.
match = re.search(r"X509v3 Subject Alternative Name:(?: critical)?\s*(.*)", text)
# WARNING: this function assumes that no SAN can include
# parts_separator, hence the split!
sans_parts = [] if match is None else match.group(1).split(parts_separator)
return [part.split(part_separator)[1]
for part in sans_parts if part.startswith(prefix)]
def gen_ss_cert(key, domains, not_before=None,
validity=(7 * 24 * 60 * 60), force_san=True, extensions=None):
"""Generate new self-signed certificate.
:type domains: `list` of `unicode`
:param OpenSSL.crypto.PKey key:
:param bool force_san:
:param extensions: List of additional extensions to include in the cert.
:type extensions: `list` of `OpenSSL.crypto.X509Extension`
If more than one domain is provided, all of the domains are put into
``subjectAltName`` X.509 extension and first domain is set as the
subject CN. If only one domain is provided no ``subjectAltName``
extension is used, unless `force_san` is ``True``.
"""
assert domains, "Must provide one or more hostnames for the cert."
cert = crypto.X509()
cert.set_serial_number(int(binascii.hexlify(os.urandom(16)), 16))
cert.set_version(2)
if extensions is None:
extensions = []
extensions.append(
crypto.X509Extension(
b"basicConstraints", True, b"CA:TRUE, pathlen:0"),
)
cert.get_subject().CN = domains[0]
# TODO: what to put into cert.get_subject()?
cert.set_issuer(cert.get_subject())
if force_san or len(domains) > 1:
extensions.append(crypto.X509Extension(
b"subjectAltName",
critical=False,
value=b", ".join(b"DNS:" + d.encode() for d in domains)
))
cert.add_extensions(extensions)
cert.gmtime_adj_notBefore(0 if not_before is None else not_before)
cert.gmtime_adj_notAfter(validity)
cert.set_pubkey(key)
cert.sign(key, "sha256")
return cert
def dump_pyopenssl_chain(chain, filetype=crypto.FILETYPE_PEM):
"""Dump certificate chain into a bundle.
:param list chain: List of `OpenSSL.crypto.X509` (or wrapped in
:class:`josepy.util.ComparableX509`).
:returns: certificate chain bundle
:rtype: bytes
"""
# XXX: returns empty string when no chain is available, which
# shuts up RenewableCert, but might not be the best solution...
def _dump_cert(cert):
if isinstance(cert, jose.ComparableX509):
cert = cert.wrapped
return crypto.dump_certificate(filetype, cert)
# assumes that OpenSSL.crypto.dump_certificate includes ending
# newline character
return b"".join(_dump_cert(cert) for cert in chain)