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"""
A library for integrating Python's builtin :py:mod:`ssl` library with Cheroot.
The :py:mod:`ssl` module must be importable for SSL functionality.
To use this module, set ``HTTPServer.ssl_adapter`` to an instance of
``BuiltinSSLAdapter``.
"""
import socket
import sys
import threading
from contextlib import suppress
try:
import ssl
except ImportError:
ssl = None
try:
from _pyio import DEFAULT_BUFFER_SIZE
except ImportError:
try:
from io import DEFAULT_BUFFER_SIZE
except ImportError:
DEFAULT_BUFFER_SIZE = -1
from . import Adapter
from .. import errors
from ..makefile import StreamReader, StreamWriter
from ..server import HTTPServer
def _assert_ssl_exc_contains(exc, *msgs):
"""Check whether SSL exception contains either of messages provided."""
if len(msgs) < 1:
raise TypeError(
'_assert_ssl_exc_contains() requires '
'at least one message to be passed.',
)
err_msg_lower = str(exc).lower()
return any(m.lower() in err_msg_lower for m in msgs)
def _loopback_for_cert_thread(context, server):
"""Wrap a socket in ssl and perform the server-side handshake."""
# As we only care about parsing the certificate, the failure of
# which will cause an exception in ``_loopback_for_cert``,
# we can safely ignore connection and ssl related exceptions. Ref:
# https://github.com/cherrypy/cheroot/issues/302#issuecomment-662592030
with suppress(ssl.SSLError, OSError):
with context.wrap_socket(
server, do_handshake_on_connect=True, server_side=True,
) as ssl_sock:
# in TLS 1.3 (Python 3.7+, OpenSSL 1.1.1+), the server
# sends the client session tickets that can be used to
# resume the TLS session on a new connection without
# performing the full handshake again. session tickets are
# sent as a post-handshake message at some _unspecified_
# time and thus a successful connection may be closed
# without the client having received the tickets.
# Unfortunately, on Windows (Python 3.8+), this is treated
# as an incomplete handshake on the server side and a
# ``ConnectionAbortedError`` is raised.
# TLS 1.3 support is still incomplete in Python 3.8;
# there is no way for the client to wait for tickets.
# While not necessary for retrieving the parsed certificate,
# we send a tiny bit of data over the connection in an
# attempt to give the server a chance to send the session
# tickets and close the connection cleanly.
# Note that, as this is essentially a race condition,
# the error may still occur ocasionally.
ssl_sock.send(b'0000')
def _loopback_for_cert(certificate, private_key, certificate_chain):
"""Create a loopback connection to parse a cert with a private key."""
context = ssl.create_default_context(cafile=certificate_chain)
context.load_cert_chain(certificate, private_key)
context.check_hostname = False
context.verify_mode = ssl.CERT_NONE
# Python 3+ Unix, Python 3.5+ Windows
client, server = socket.socketpair()
try:
# `wrap_socket` will block until the ssl handshake is complete.
# it must be called on both ends at the same time -> thread
# openssl will cache the peer's cert during a successful handshake
# and return it via `getpeercert` even after the socket is closed.
# when `close` is called, the SSL shutdown notice will be sent
# and then python will wait to receive the corollary shutdown.
thread = threading.Thread(
target=_loopback_for_cert_thread, args=(context, server),
)
try:
thread.start()
with context.wrap_socket(
client, do_handshake_on_connect=True,
server_side=False,
) as ssl_sock:
ssl_sock.recv(4)
return ssl_sock.getpeercert()
finally:
thread.join()
finally:
client.close()
server.close()
def _parse_cert(certificate, private_key, certificate_chain):
"""Parse a certificate."""
# loopback_for_cert uses socket.socketpair which was only
# introduced in Python 3.0 for *nix and 3.5 for Windows
# and requires OS support (AttributeError, OSError)
# it also requires a private key either in its own file
# or combined with the cert (SSLError)
with suppress(AttributeError, ssl.SSLError, OSError):
return _loopback_for_cert(certificate, private_key, certificate_chain)
# KLUDGE: using an undocumented, private, test method to parse a cert
# unfortunately, it is the only built-in way without a connection
# as a private, undocumented method, it may change at any time
# so be tolerant of *any* possible errors it may raise
with suppress(Exception):
return ssl._ssl._test_decode_cert(certificate)
return {}
def _sni_callback(sock, sni, context):
"""Handle the SNI callback to tag the socket with the SNI."""
sock.sni = sni
# return None to allow the TLS negotiation to continue
class BuiltinSSLAdapter(Adapter):
"""Wrapper for integrating Python's builtin :py:mod:`ssl` with Cheroot."""
certificate = None
"""The file name of the server SSL certificate."""
private_key = None
"""The file name of the server's private key file."""
certificate_chain = None
"""The file name of the certificate chain file."""
ciphers = None
"""The ciphers list of SSL."""
# from mod_ssl/pkg.sslmod/ssl_engine_vars.c ssl_var_lookup_ssl_cert
CERT_KEY_TO_ENV = {
'version': 'M_VERSION',
'serialNumber': 'M_SERIAL',
'notBefore': 'V_START',
'notAfter': 'V_END',
'subject': 'S_DN',
'issuer': 'I_DN',
'subjectAltName': 'SAN',
# not parsed by the Python standard library
# - A_SIG
# - A_KEY
# not provided by mod_ssl
# - OCSP
# - caIssuers
# - crlDistributionPoints
}
# from mod_ssl/pkg.sslmod/ssl_engine_vars.c ssl_var_lookup_ssl_cert_dn_rec
CERT_KEY_TO_LDAP_CODE = {
'countryName': 'C',
'stateOrProvinceName': 'ST',
# NOTE: mod_ssl also provides 'stateOrProvinceName' as 'SP'
# for compatibility with SSLeay
'localityName': 'L',
'organizationName': 'O',
'organizationalUnitName': 'OU',
'commonName': 'CN',
'title': 'T',
'initials': 'I',
'givenName': 'G',
'surname': 'S',
'description': 'D',
'userid': 'UID',
'emailAddress': 'Email',
# not provided by mod_ssl
# - dnQualifier: DNQ
# - domainComponent: DC
# - postalCode: PC
# - streetAddress: STREET
# - serialNumber
# - generationQualifier
# - pseudonym
# - jurisdictionCountryName
# - jurisdictionLocalityName
# - jurisdictionStateOrProvince
# - businessCategory
}
def __init__(
self, certificate, private_key, certificate_chain=None,
ciphers=None,
):
"""Set up context in addition to base class properties if available."""
if ssl is None:
raise ImportError('You must install the ssl module to use HTTPS.')
super(BuiltinSSLAdapter, self).__init__(
certificate, private_key, certificate_chain, ciphers,
)
self.context = ssl.create_default_context(
purpose=ssl.Purpose.CLIENT_AUTH,
cafile=certificate_chain,
)
self.context.load_cert_chain(certificate, private_key)
if self.ciphers is not None:
self.context.set_ciphers(ciphers)
self._server_env = self._make_env_cert_dict(
'SSL_SERVER',
_parse_cert(certificate, private_key, self.certificate_chain),
)
if not self._server_env:
return
cert = None
with open(certificate, mode='rt') as f:
cert = f.read()
# strip off any keys by only taking the first certificate
cert_start = cert.find(ssl.PEM_HEADER)
if cert_start == -1:
return
cert_end = cert.find(ssl.PEM_FOOTER, cert_start)
if cert_end == -1:
return
cert_end += len(ssl.PEM_FOOTER)
self._server_env['SSL_SERVER_CERT'] = cert[cert_start:cert_end]
@property
def context(self):
""":py:class:`~ssl.SSLContext` that will be used to wrap sockets."""
return self._context
@context.setter
def context(self, context):
"""Set the ssl ``context`` to use."""
self._context = context
# Python 3.7+
# if a context is provided via `cherrypy.config.update` then
# `self.context` will be set after `__init__`
# use a property to intercept it to add an SNI callback
# but don't override the user's callback
# TODO: chain callbacks
with suppress(AttributeError):
if ssl.HAS_SNI and context.sni_callback is None:
context.sni_callback = _sni_callback
def bind(self, sock):
"""Wrap and return the given socket."""
return super(BuiltinSSLAdapter, self).bind(sock)
def wrap(self, sock):
"""Wrap and return the given socket, plus WSGI environ entries."""
try:
s = self.context.wrap_socket(
sock, do_handshake_on_connect=True, server_side=True,
)
except (
ssl.SSLEOFError,
ssl.SSLZeroReturnError,
) as tls_connection_drop_error:
raise errors.FatalSSLAlert(
*tls_connection_drop_error.args,
) from tls_connection_drop_error
except ssl.SSLError as generic_tls_error:
peer_speaks_plain_http_over_https = (
generic_tls_error.errno == ssl.SSL_ERROR_SSL and
_assert_ssl_exc_contains(generic_tls_error, 'http request')
)
if peer_speaks_plain_http_over_https:
reraised_connection_drop_exc_cls = errors.NoSSLError
else:
reraised_connection_drop_exc_cls = errors.FatalSSLAlert
raise reraised_connection_drop_exc_cls(
*generic_tls_error.args,
) from generic_tls_error
except OSError as tcp_connection_drop_error:
raise errors.FatalSSLAlert(
*tcp_connection_drop_error.args,
) from tcp_connection_drop_error
return s, self.get_environ(s)
def get_environ(self, sock):
"""Create WSGI environ entries to be merged into each request."""
cipher = sock.cipher()
ssl_environ = {
'wsgi.url_scheme': 'https',
'HTTPS': 'on',
'SSL_PROTOCOL': cipher[1],
'SSL_CIPHER': cipher[0],
'SSL_CIPHER_EXPORT': '',
'SSL_CIPHER_USEKEYSIZE': cipher[2],
'SSL_VERSION_INTERFACE': '%s Python/%s' % (
HTTPServer.version, sys.version,
),
'SSL_VERSION_LIBRARY': ssl.OPENSSL_VERSION,
'SSL_CLIENT_VERIFY': 'NONE',
# 'NONE' - client did not provide a cert (overriden below)
}
# Python 3.3+
with suppress(AttributeError):
compression = sock.compression()
if compression is not None:
ssl_environ['SSL_COMPRESS_METHOD'] = compression
# Python 3.6+
with suppress(AttributeError):
ssl_environ['SSL_SESSION_ID'] = sock.session.id.hex()
with suppress(AttributeError):
target_cipher = cipher[:2]
for cip in sock.context.get_ciphers():
if target_cipher == (cip['name'], cip['protocol']):
ssl_environ['SSL_CIPHER_ALGKEYSIZE'] = cip['alg_bits']
break
# Python 3.7+ sni_callback
with suppress(AttributeError):
ssl_environ['SSL_TLS_SNI'] = sock.sni
if self.context and self.context.verify_mode != ssl.CERT_NONE:
client_cert = sock.getpeercert()
if client_cert:
# builtin ssl **ALWAYS** validates client certificates
# and terminates the connection on failure
ssl_environ['SSL_CLIENT_VERIFY'] = 'SUCCESS'
ssl_environ.update(
self._make_env_cert_dict('SSL_CLIENT', client_cert),
)
ssl_environ['SSL_CLIENT_CERT'] = ssl.DER_cert_to_PEM_cert(
sock.getpeercert(binary_form=True),
).strip()
ssl_environ.update(self._server_env)
# not supplied by the Python standard library (as of 3.8)
# - SSL_SESSION_RESUMED
# - SSL_SECURE_RENEG
# - SSL_CLIENT_CERT_CHAIN_n
# - SRP_USER
# - SRP_USERINFO
return ssl_environ
def _make_env_cert_dict(self, env_prefix, parsed_cert):
"""Return a dict of WSGI environment variables for a certificate.
E.g. SSL_CLIENT_M_VERSION, SSL_CLIENT_M_SERIAL, etc.
See https://httpd.apache.org/docs/2.4/mod/mod_ssl.html#envvars.
"""
if not parsed_cert:
return {}
env = {}
for cert_key, env_var in self.CERT_KEY_TO_ENV.items():
key = '%s_%s' % (env_prefix, env_var)
value = parsed_cert.get(cert_key)
if env_var == 'SAN':
env.update(self._make_env_san_dict(key, value))
elif env_var.endswith('_DN'):
env.update(self._make_env_dn_dict(key, value))
else:
env[key] = str(value)
# mod_ssl 2.1+; Python 3.2+
# number of days until the certificate expires
if 'notBefore' in parsed_cert:
remain = ssl.cert_time_to_seconds(parsed_cert['notAfter'])
remain -= ssl.cert_time_to_seconds(parsed_cert['notBefore'])
remain /= 60 * 60 * 24
env['%s_V_REMAIN' % (env_prefix,)] = str(int(remain))
return env
def _make_env_san_dict(self, env_prefix, cert_value):
"""Return a dict of WSGI environment variables for a certificate DN.
E.g. SSL_CLIENT_SAN_Email_0, SSL_CLIENT_SAN_DNS_0, etc.
See SSL_CLIENT_SAN_* at
https://httpd.apache.org/docs/2.4/mod/mod_ssl.html#envvars.
"""
if not cert_value:
return {}
env = {}
dns_count = 0
email_count = 0
for attr_name, val in cert_value:
if attr_name == 'DNS':
env['%s_DNS_%i' % (env_prefix, dns_count)] = val
dns_count += 1
elif attr_name == 'Email':
env['%s_Email_%i' % (env_prefix, email_count)] = val
email_count += 1
# other mod_ssl SAN vars:
# - SAN_OTHER_msUPN_n
return env
def _make_env_dn_dict(self, env_prefix, cert_value):
"""Return a dict of WSGI environment variables for a certificate DN.
E.g. SSL_CLIENT_S_DN_CN, SSL_CLIENT_S_DN_C, etc.
See SSL_CLIENT_S_DN_x509 at
https://httpd.apache.org/docs/2.4/mod/mod_ssl.html#envvars.
"""
if not cert_value:
return {}
dn = []
dn_attrs = {}
for rdn in cert_value:
for attr_name, val in rdn:
attr_code = self.CERT_KEY_TO_LDAP_CODE.get(attr_name)
dn.append('%s=%s' % (attr_code or attr_name, val))
if not attr_code:
continue
dn_attrs.setdefault(attr_code, [])
dn_attrs[attr_code].append(val)
env = {
env_prefix: ','.join(dn),
}
for attr_code, values in dn_attrs.items():
env['%s_%s' % (env_prefix, attr_code)] = ','.join(values)
if len(values) == 1:
continue
for i, val in enumerate(values):
env['%s_%s_%i' % (env_prefix, attr_code, i)] = val
return env
def makefile(self, sock, mode='r', bufsize=DEFAULT_BUFFER_SIZE):
"""Return socket file object."""
cls = StreamReader if 'r' in mode else StreamWriter
return cls(sock, mode, bufsize)
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