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ssl.py
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686 lines (589 loc) · 23.8 KB
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# Wrapper module for _ssl, providing some additional facilities
# implemented in Python. Written by Bill Janssen.
"""This module provides some more Pythonic support for SSL.
Object types:
SSLSocket -- subtype of socket.socket which does SSL over the socket
Exceptions:
SSLError -- exception raised for I/O errors
Functions:
cert_time_to_seconds -- convert time string used for certificate
notBefore and notAfter functions to integer
seconds past the Epoch (the time values
returned from time.time())
fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
by the server running on HOST at port PORT. No
validation of the certificate is performed.
Integer constants:
SSL_ERROR_ZERO_RETURN
SSL_ERROR_WANT_READ
SSL_ERROR_WANT_WRITE
SSL_ERROR_WANT_X509_LOOKUP
SSL_ERROR_SYSCALL
SSL_ERROR_SSL
SSL_ERROR_WANT_CONNECT
SSL_ERROR_EOF
SSL_ERROR_INVALID_ERROR_CODE
The following group define certificate requirements that one side is
allowing/requiring from the other side:
CERT_NONE - no certificates from the other side are required (or will
be looked at if provided)
CERT_OPTIONAL - certificates are not required, but if provided will be
validated, and if validation fails, the connection will
also fail
CERT_REQUIRED - certificates are required, and will be validated, and
if validation fails, the connection will also fail
The following constants identify various SSL protocol variants:
PROTOCOL_SSLv2
PROTOCOL_SSLv3
PROTOCOL_SSLv23
PROTOCOL_TLSv1
"""
import textwrap
import re
import _ssl # if we can't import it, let the error propagate
from _ssl import OPENSSL_VERSION_NUMBER, OPENSSL_VERSION_INFO, OPENSSL_VERSION
from _ssl import _SSLContext
from _ssl import (
SSLError, SSLZeroReturnError, SSLWantReadError, SSLWantWriteError,
SSLSyscallError, SSLEOFError,
)
from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
from _ssl import (
OP_ALL, OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_TLSv1,
OP_CIPHER_SERVER_PREFERENCE, OP_SINGLE_DH_USE
)
try:
from _ssl import OP_NO_COMPRESSION
except ImportError:
pass
try:
from _ssl import OP_SINGLE_ECDH_USE
except ImportError:
pass
from _ssl import RAND_status, RAND_egd, RAND_add, RAND_bytes, RAND_pseudo_bytes
from _ssl import (
SSL_ERROR_ZERO_RETURN,
SSL_ERROR_WANT_READ,
SSL_ERROR_WANT_WRITE,
SSL_ERROR_WANT_X509_LOOKUP,
SSL_ERROR_SYSCALL,
SSL_ERROR_SSL,
SSL_ERROR_WANT_CONNECT,
SSL_ERROR_EOF,
SSL_ERROR_INVALID_ERROR_CODE,
)
from _ssl import HAS_SNI, HAS_ECDH, HAS_NPN
from _ssl import (PROTOCOL_SSLv3, PROTOCOL_SSLv23,
PROTOCOL_TLSv1)
from _ssl import _OPENSSL_API_VERSION
_PROTOCOL_NAMES = {
PROTOCOL_TLSv1: "TLSv1",
PROTOCOL_SSLv23: "SSLv23",
PROTOCOL_SSLv3: "SSLv3",
}
try:
from _ssl import PROTOCOL_SSLv2
_SSLv2_IF_EXISTS = PROTOCOL_SSLv2
except ImportError:
_SSLv2_IF_EXISTS = None
else:
_PROTOCOL_NAMES[PROTOCOL_SSLv2] = "SSLv2"
from socket import getnameinfo as _getnameinfo
from socket import error as socket_error
from socket import socket, AF_INET, SOCK_STREAM, create_connection
from socket import SOL_SOCKET, SO_TYPE
import base64 # for DER-to-PEM translation
import traceback
import errno
if _ssl.HAS_TLS_UNIQUE:
CHANNEL_BINDING_TYPES = ['tls-unique']
else:
CHANNEL_BINDING_TYPES = []
# Disable weak or insecure ciphers by default
# (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
_DEFAULT_CIPHERS = 'DEFAULT:!aNULL:!eNULL:!LOW:!EXPORT:!SSLv2'
class CertificateError(ValueError):
pass
def _dnsname_match(dn, hostname, max_wildcards=1):
"""Matching according to RFC 6125, section 6.4.3
http://tools.ietf.org/html/rfc6125#section-6.4.3
"""
pats = []
if not dn:
return False
leftmost, *remainder = dn.split(r'.')
wildcards = leftmost.count('*')
if wildcards > max_wildcards:
# Issue #17980: avoid denials of service by refusing more
# than one wildcard per fragment. A survery of established
# policy among SSL implementations showed it to be a
# reasonable choice.
raise CertificateError(
"too many wildcards in certificate DNS name: " + repr(dn))
# speed up common case w/o wildcards
if not wildcards:
return dn.lower() == hostname.lower()
# RFC 6125, section 6.4.3, subitem 1.
# The client SHOULD NOT attempt to match a presented identifier in which
# the wildcard character comprises a label other than the left-most label.
if leftmost == '*':
# When '*' is a fragment by itself, it matches a non-empty dotless
# fragment.
pats.append('[^.]+')
elif leftmost.startswith('xn--') or hostname.startswith('xn--'):
# RFC 6125, section 6.4.3, subitem 3.
# The client SHOULD NOT attempt to match a presented identifier
# where the wildcard character is embedded within an A-label or
# U-label of an internationalized domain name.
pats.append(re.escape(leftmost))
else:
# Otherwise, '*' matches any dotless string, e.g. www*
pats.append(re.escape(leftmost).replace(r'\*', '[^.]*'))
# add the remaining fragments, ignore any wildcards
for frag in remainder:
pats.append(re.escape(frag))
pat = re.compile(r'\A' + r'\.'.join(pats) + r'\Z', re.IGNORECASE)
return pat.match(hostname)
def match_hostname(cert, hostname):
"""Verify that *cert* (in decoded format as returned by
SSLSocket.getpeercert()) matches the *hostname*. RFC 2818 and RFC 6125
rules are followed, but IP addresses are not accepted for *hostname*.
CertificateError is raised on failure. On success, the function
returns nothing.
"""
if not cert:
raise ValueError("empty or no certificate")
dnsnames = []
san = cert.get('subjectAltName', ())
for key, value in san:
if key == 'DNS':
if _dnsname_match(value, hostname):
return
dnsnames.append(value)
if not dnsnames:
# The subject is only checked when there is no dNSName entry
# in subjectAltName
for sub in cert.get('subject', ()):
for key, value in sub:
# XXX according to RFC 2818, the most specific Common Name
# must be used.
if key == 'commonName':
if _dnsname_match(value, hostname):
return
dnsnames.append(value)
if len(dnsnames) > 1:
raise CertificateError("hostname %r "
"doesn't match either of %s"
% (hostname, ', '.join(map(repr, dnsnames))))
elif len(dnsnames) == 1:
raise CertificateError("hostname %r "
"doesn't match %r"
% (hostname, dnsnames[0]))
else:
raise CertificateError("no appropriate commonName or "
"subjectAltName fields were found")
class SSLContext(_SSLContext):
"""An SSLContext holds various SSL-related configuration options and
data, such as certificates and possibly a private key."""
__slots__ = ('protocol',)
def __new__(cls, protocol, *args, **kwargs):
self = _SSLContext.__new__(cls, protocol)
if protocol != _SSLv2_IF_EXISTS:
self.set_ciphers(_DEFAULT_CIPHERS)
return self
def __init__(self, protocol):
self.protocol = protocol
def wrap_socket(self, sock, server_side=False,
do_handshake_on_connect=True,
suppress_ragged_eofs=True,
server_hostname=None):
return SSLSocket(sock=sock, server_side=server_side,
do_handshake_on_connect=do_handshake_on_connect,
suppress_ragged_eofs=suppress_ragged_eofs,
server_hostname=server_hostname,
_context=self)
def set_npn_protocols(self, npn_protocols):
protos = bytearray()
for protocol in npn_protocols:
b = bytes(protocol, 'ascii')
if len(b) == 0 or len(b) > 255:
raise SSLError('NPN protocols must be 1 to 255 in length')
protos.append(len(b))
protos.extend(b)
self._set_npn_protocols(protos)
class SSLSocket(socket):
"""This class implements a subtype of socket.socket that wraps
the underlying OS socket in an SSL context when necessary, and
provides read and write methods over that channel."""
def __init__(self, sock=None, keyfile=None, certfile=None,
server_side=False, cert_reqs=CERT_NONE,
ssl_version=PROTOCOL_SSLv23, ca_certs=None,
do_handshake_on_connect=True,
family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None,
suppress_ragged_eofs=True, npn_protocols=None, ciphers=None,
server_hostname=None,
_context=None):
if _context:
self.context = _context
else:
if server_side and not certfile:
raise ValueError("certfile must be specified for server-side "
"operations")
if keyfile and not certfile:
raise ValueError("certfile must be specified")
if certfile and not keyfile:
keyfile = certfile
self.context = SSLContext(ssl_version)
self.context.verify_mode = cert_reqs
if ca_certs:
self.context.load_verify_locations(ca_certs)
if certfile:
self.context.load_cert_chain(certfile, keyfile)
if npn_protocols:
self.context.set_npn_protocols(npn_protocols)
if ciphers:
self.context.set_ciphers(ciphers)
self.keyfile = keyfile
self.certfile = certfile
self.cert_reqs = cert_reqs
self.ssl_version = ssl_version
self.ca_certs = ca_certs
self.ciphers = ciphers
# Can't use sock.type as other flags (such as SOCK_NONBLOCK) get
# mixed in.
if sock.getsockopt(SOL_SOCKET, SO_TYPE) != SOCK_STREAM:
raise NotImplementedError("only stream sockets are supported")
if server_side and server_hostname:
raise ValueError("server_hostname can only be specified "
"in client mode")
self.server_side = server_side
self.server_hostname = server_hostname
self.do_handshake_on_connect = do_handshake_on_connect
self.suppress_ragged_eofs = suppress_ragged_eofs
connected = False
if sock is not None:
socket.__init__(self,
family=sock.family,
type=sock.type,
proto=sock.proto,
fileno=sock.fileno())
self.settimeout(sock.gettimeout())
# see if it's connected
try:
sock.getpeername()
except socket_error as e:
if e.errno != errno.ENOTCONN:
raise
else:
connected = True
sock.detach()
elif fileno is not None:
socket.__init__(self, fileno=fileno)
else:
socket.__init__(self, family=family, type=type, proto=proto)
self._closed = False
self._sslobj = None
self._connected = connected
if connected:
# create the SSL object
try:
self._sslobj = self.context._wrap_socket(self, server_side,
server_hostname)
if do_handshake_on_connect:
timeout = self.gettimeout()
if timeout == 0.0:
# non-blocking
raise ValueError("do_handshake_on_connect should not be specified for non-blocking sockets")
self.do_handshake()
except socket_error as x:
self.close()
raise x
def dup(self):
raise NotImplemented("Can't dup() %s instances" %
self.__class__.__name__)
def _checkClosed(self, msg=None):
# raise an exception here if you wish to check for spurious closes
pass
def read(self, len=0, buffer=None):
"""Read up to LEN bytes and return them.
Return zero-length string on EOF."""
self._checkClosed()
try:
if buffer is not None:
v = self._sslobj.read(len, buffer)
else:
v = self._sslobj.read(len or 1024)
return v
except SSLError as x:
if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:
if buffer is not None:
return 0
else:
return b''
else:
raise
def write(self, data):
"""Write DATA to the underlying SSL channel. Returns
number of bytes of DATA actually transmitted."""
self._checkClosed()
return self._sslobj.write(data)
def getpeercert(self, binary_form=False):
"""Returns a formatted version of the data in the
certificate provided by the other end of the SSL channel.
Return None if no certificate was provided, {} if a
certificate was provided, but not validated."""
self._checkClosed()
return self._sslobj.peer_certificate(binary_form)
def selected_npn_protocol(self):
self._checkClosed()
if not self._sslobj or not _ssl.HAS_NPN:
return None
else:
return self._sslobj.selected_npn_protocol()
def cipher(self):
self._checkClosed()
if not self._sslobj:
return None
else:
return self._sslobj.cipher()
def compression(self):
self._checkClosed()
if not self._sslobj:
return None
else:
return self._sslobj.compression()
def send(self, data, flags=0):
self._checkClosed()
if self._sslobj:
if flags != 0:
raise ValueError(
"non-zero flags not allowed in calls to send() on %s" %
self.__class__)
while True:
try:
v = self._sslobj.write(data)
except SSLError as x:
if x.args[0] == SSL_ERROR_WANT_READ:
return 0
elif x.args[0] == SSL_ERROR_WANT_WRITE:
return 0
else:
raise
else:
return v
else:
return socket.send(self, data, flags)
def sendto(self, data, flags_or_addr, addr=None):
self._checkClosed()
if self._sslobj:
raise ValueError("sendto not allowed on instances of %s" %
self.__class__)
elif addr is None:
return socket.sendto(self, data, flags_or_addr)
else:
return socket.sendto(self, data, flags_or_addr, addr)
def sendmsg(self, *args, **kwargs):
# Ensure programs don't send data unencrypted if they try to
# use this method.
raise NotImplementedError("sendmsg not allowed on instances of %s" %
self.__class__)
def sendall(self, data, flags=0):
self._checkClosed()
if self._sslobj:
if flags != 0:
raise ValueError(
"non-zero flags not allowed in calls to sendall() on %s" %
self.__class__)
amount = len(data)
count = 0
while (count < amount):
v = self.send(data[count:])
count += v
return amount
else:
return socket.sendall(self, data, flags)
def recv(self, buflen=1024, flags=0):
self._checkClosed()
if self._sslobj:
if flags != 0:
raise ValueError(
"non-zero flags not allowed in calls to recv() on %s" %
self.__class__)
return self.read(buflen)
else:
return socket.recv(self, buflen, flags)
def recv_into(self, buffer, nbytes=None, flags=0):
self._checkClosed()
if buffer and (nbytes is None):
nbytes = len(buffer)
elif nbytes is None:
nbytes = 1024
if self._sslobj:
if flags != 0:
raise ValueError(
"non-zero flags not allowed in calls to recv_into() on %s" %
self.__class__)
return self.read(nbytes, buffer)
else:
return socket.recv_into(self, buffer, nbytes, flags)
def recvfrom(self, buflen=1024, flags=0):
self._checkClosed()
if self._sslobj:
raise ValueError("recvfrom not allowed on instances of %s" %
self.__class__)
else:
return socket.recvfrom(self, buflen, flags)
def recvfrom_into(self, buffer, nbytes=None, flags=0):
self._checkClosed()
if self._sslobj:
raise ValueError("recvfrom_into not allowed on instances of %s" %
self.__class__)
else:
return socket.recvfrom_into(self, buffer, nbytes, flags)
def recvmsg(self, *args, **kwargs):
raise NotImplementedError("recvmsg not allowed on instances of %s" %
self.__class__)
def recvmsg_into(self, *args, **kwargs):
raise NotImplementedError("recvmsg_into not allowed on instances of "
"%s" % self.__class__)
def pending(self):
self._checkClosed()
if self._sslobj:
return self._sslobj.pending()
else:
return 0
def shutdown(self, how):
self._checkClosed()
self._sslobj = None
socket.shutdown(self, how)
def unwrap(self):
if self._sslobj:
s = self._sslobj.shutdown()
self._sslobj = None
return s
else:
raise ValueError("No SSL wrapper around " + str(self))
def _real_close(self):
self._sslobj = None
# self._closed = True
socket._real_close(self)
def do_handshake(self, block=False):
"""Perform a TLS/SSL handshake."""
timeout = self.gettimeout()
try:
if timeout == 0.0 and block:
self.settimeout(None)
self._sslobj.do_handshake()
finally:
self.settimeout(timeout)
def _real_connect(self, addr, connect_ex):
if self.server_side:
raise ValueError("can't connect in server-side mode")
# Here we assume that the socket is client-side, and not
# connected at the time of the call. We connect it, then wrap it.
if self._connected:
raise ValueError("attempt to connect already-connected SSLSocket!")
self._sslobj = self.context._wrap_socket(self, False, self.server_hostname)
try:
if connect_ex:
rc = socket.connect_ex(self, addr)
else:
rc = None
socket.connect(self, addr)
if not rc:
if self.do_handshake_on_connect:
self.do_handshake()
self._connected = True
return rc
except socket_error:
self._sslobj = None
raise
def connect(self, addr):
"""Connects to remote ADDR, and then wraps the connection in
an SSL channel."""
self._real_connect(addr, False)
def connect_ex(self, addr):
"""Connects to remote ADDR, and then wraps the connection in
an SSL channel."""
return self._real_connect(addr, True)
def accept(self):
"""Accepts a new connection from a remote client, and returns
a tuple containing that new connection wrapped with a server-side
SSL channel, and the address of the remote client."""
newsock, addr = socket.accept(self)
newsock = self.context.wrap_socket(newsock,
do_handshake_on_connect=self.do_handshake_on_connect,
suppress_ragged_eofs=self.suppress_ragged_eofs,
server_side=True)
return newsock, addr
def get_channel_binding(self, cb_type="tls-unique"):
"""Get channel binding data for current connection. Raise ValueError
if the requested `cb_type` is not supported. Return bytes of the data
or None if the data is not available (e.g. before the handshake).
"""
if cb_type not in CHANNEL_BINDING_TYPES:
raise ValueError("Unsupported channel binding type")
if cb_type != "tls-unique":
raise NotImplementedError(
"{0} channel binding type not implemented"
.format(cb_type))
if self._sslobj is None:
return None
return self._sslobj.tls_unique_cb()
def wrap_socket(sock, keyfile=None, certfile=None,
server_side=False, cert_reqs=CERT_NONE,
ssl_version=PROTOCOL_SSLv23, ca_certs=None,
do_handshake_on_connect=True,
suppress_ragged_eofs=True,
ciphers=None):
return SSLSocket(sock=sock, keyfile=keyfile, certfile=certfile,
server_side=server_side, cert_reqs=cert_reqs,
ssl_version=ssl_version, ca_certs=ca_certs,
do_handshake_on_connect=do_handshake_on_connect,
suppress_ragged_eofs=suppress_ragged_eofs,
ciphers=ciphers)
# some utility functions
def cert_time_to_seconds(cert_time):
"""Takes a date-time string in standard ASN1_print form
("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return
a Python time value in seconds past the epoch."""
import time
return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
PEM_HEADER = "-----BEGIN CERTIFICATE-----"
PEM_FOOTER = "-----END CERTIFICATE-----"
def DER_cert_to_PEM_cert(der_cert_bytes):
"""Takes a certificate in binary DER format and returns the
PEM version of it as a string."""
f = str(base64.standard_b64encode(der_cert_bytes), 'ASCII', 'strict')
return (PEM_HEADER + '\n' +
textwrap.fill(f, 64) + '\n' +
PEM_FOOTER + '\n')
def PEM_cert_to_DER_cert(pem_cert_string):
"""Takes a certificate in ASCII PEM format and returns the
DER-encoded version of it as a byte sequence"""
if not pem_cert_string.startswith(PEM_HEADER):
raise ValueError("Invalid PEM encoding; must start with %s"
% PEM_HEADER)
if not pem_cert_string.strip().endswith(PEM_FOOTER):
raise ValueError("Invalid PEM encoding; must end with %s"
% PEM_FOOTER)
d = pem_cert_string.strip()[len(PEM_HEADER):-len(PEM_FOOTER)]
return base64.decodebytes(d.encode('ASCII', 'strict'))
def get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):
"""Retrieve the certificate from the server at the specified address,
and return it as a PEM-encoded string.
If 'ca_certs' is specified, validate the server cert against it.
If 'ssl_version' is specified, use it in the connection attempt."""
host, port = addr
if (ca_certs is not None):
cert_reqs = CERT_REQUIRED
else:
cert_reqs = CERT_NONE
s = create_connection(addr)
s = wrap_socket(s, ssl_version=ssl_version,
cert_reqs=cert_reqs, ca_certs=ca_certs)
dercert = s.getpeercert(True)
s.close()
return DER_cert_to_PEM_cert(dercert)
def get_protocol_name(protocol_code):
return _PROTOCOL_NAMES.get(protocol_code, '<unknown>')