1# Wrapper module for _ssl, providing some additional facilities
2# implemented in Python.  Written by Bill Janssen.
3
4"""\
5This module provides some more Pythonic support for SSL.
6
7Object types:
8
9  SSLSocket -- subtype of socket.socket which does SSL over the socket
10
11Exceptions:
12
13  SSLError -- exception raised for I/O errors
14
15Functions:
16
17  cert_time_to_seconds -- convert time string used for certificate
18                          notBefore and notAfter functions to integer
19                          seconds past the Epoch (the time values
20                          returned from time.time())
21
22  fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
23                          by the server running on HOST at port PORT.  No
24                          validation of the certificate is performed.
25
26Integer constants:
27
28SSL_ERROR_ZERO_RETURN
29SSL_ERROR_WANT_READ
30SSL_ERROR_WANT_WRITE
31SSL_ERROR_WANT_X509_LOOKUP
32SSL_ERROR_SYSCALL
33SSL_ERROR_SSL
34SSL_ERROR_WANT_CONNECT
35
36SSL_ERROR_EOF
37SSL_ERROR_INVALID_ERROR_CODE
38
39The following group define certificate requirements that one side is
40allowing/requiring from the other side:
41
42CERT_NONE - no certificates from the other side are required (or will
43            be looked at if provided)
44CERT_OPTIONAL - certificates are not required, but if provided will be
45                validated, and if validation fails, the connection will
46                also fail
47CERT_REQUIRED - certificates are required, and will be validated, and
48                if validation fails, the connection will also fail
49
50The following constants identify various SSL protocol variants:
51
52PROTOCOL_SSLv2
53PROTOCOL_SSLv3
54PROTOCOL_SSLv23
55PROTOCOL_TLSv1
56"""
57
58import textwrap
59
60import _ssl             # if we can't import it, let the error propagate
61
62from _ssl import OPENSSL_VERSION_NUMBER, OPENSSL_VERSION_INFO, OPENSSL_VERSION
63from _ssl import SSLError
64from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
65from _ssl import RAND_status, RAND_egd, RAND_add
66from _ssl import \
67     SSL_ERROR_ZERO_RETURN, \
68     SSL_ERROR_WANT_READ, \
69     SSL_ERROR_WANT_WRITE, \
70     SSL_ERROR_WANT_X509_LOOKUP, \
71     SSL_ERROR_SYSCALL, \
72     SSL_ERROR_SSL, \
73     SSL_ERROR_WANT_CONNECT, \
74     SSL_ERROR_EOF, \
75     SSL_ERROR_INVALID_ERROR_CODE
76from _ssl import PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1
77_PROTOCOL_NAMES = {
78    PROTOCOL_TLSv1: "TLSv1",
79    PROTOCOL_SSLv23: "SSLv23",
80    PROTOCOL_SSLv3: "SSLv3",
81}
82try:
83    from _ssl import PROTOCOL_SSLv2
84    _SSLv2_IF_EXISTS = PROTOCOL_SSLv2
85except ImportError:
86    _SSLv2_IF_EXISTS = None
87else:
88    _PROTOCOL_NAMES[PROTOCOL_SSLv2] = "SSLv2"
89
90from socket import socket, _fileobject, _delegate_methods, error as socket_error
91from socket import getnameinfo as _getnameinfo
92import base64        # for DER-to-PEM translation
93import errno
94
95# Disable weak or insecure ciphers by default
96# (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
97_DEFAULT_CIPHERS = 'DEFAULT:!aNULL:!eNULL:!LOW:!EXPORT:!SSLv2'
98
99
100class SSLSocket(socket):
101
102    """This class implements a subtype of socket.socket that wraps
103    the underlying OS socket in an SSL context when necessary, and
104    provides read and write methods over that channel."""
105
106    def __init__(self, sock, keyfile=None, certfile=None,
107                 server_side=False, cert_reqs=CERT_NONE,
108                 ssl_version=PROTOCOL_SSLv23, ca_certs=None,
109                 do_handshake_on_connect=True,
110                 suppress_ragged_eofs=True, ciphers=None):
111        socket.__init__(self, _sock=sock._sock)
112        # The initializer for socket overrides the methods send(), recv(), etc.
113        # in the instancce, which we don't need -- but we want to provide the
114        # methods defined in SSLSocket.
115        for attr in _delegate_methods:
116            try:
117                delattr(self, attr)
118            except AttributeError:
119                pass
120
121        if ciphers is None and ssl_version != _SSLv2_IF_EXISTS:
122            ciphers = _DEFAULT_CIPHERS
123
124        if certfile and not keyfile:
125            keyfile = certfile
126        # see if it's connected
127        try:
128            socket.getpeername(self)
129        except socket_error, e:
130            if e.errno != errno.ENOTCONN:
131                raise
132            # no, no connection yet
133            self._connected = False
134            self._sslobj = None
135        else:
136            # yes, create the SSL object
137            self._connected = True
138            self._sslobj = _ssl.sslwrap(self._sock, server_side,
139                                        keyfile, certfile,
140                                        cert_reqs, ssl_version, ca_certs,
141                                        ciphers)
142            if do_handshake_on_connect:
143                self.do_handshake()
144        self.keyfile = keyfile
145        self.certfile = certfile
146        self.cert_reqs = cert_reqs
147        self.ssl_version = ssl_version
148        self.ca_certs = ca_certs
149        self.ciphers = ciphers
150        self.do_handshake_on_connect = do_handshake_on_connect
151        self.suppress_ragged_eofs = suppress_ragged_eofs
152        self._makefile_refs = 0
153
154    def read(self, len=1024):
155
156        """Read up to LEN bytes and return them.
157        Return zero-length string on EOF."""
158
159        try:
160            return self._sslobj.read(len)
161        except SSLError, x:
162            if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:
163                return ''
164            else:
165                raise
166
167    def write(self, data):
168
169        """Write DATA to the underlying SSL channel.  Returns
170        number of bytes of DATA actually transmitted."""
171
172        return self._sslobj.write(data)
173
174    def getpeercert(self, binary_form=False):
175
176        """Returns a formatted version of the data in the
177        certificate provided by the other end of the SSL channel.
178        Return None if no certificate was provided, {} if a
179        certificate was provided, but not validated."""
180
181        return self._sslobj.peer_certificate(binary_form)
182
183    def cipher(self):
184
185        if not self._sslobj:
186            return None
187        else:
188            return self._sslobj.cipher()
189
190    def send(self, data, flags=0):
191        if self._sslobj:
192            if flags != 0:
193                raise ValueError(
194                    "non-zero flags not allowed in calls to send() on %s" %
195                    self.__class__)
196            while True:
197                try:
198                    v = self._sslobj.write(data)
199                except SSLError, x:
200                    if x.args[0] == SSL_ERROR_WANT_READ:
201                        return 0
202                    elif x.args[0] == SSL_ERROR_WANT_WRITE:
203                        return 0
204                    else:
205                        raise
206                else:
207                    return v
208        else:
209            return self._sock.send(data, flags)
210
211    def sendto(self, data, flags_or_addr, addr=None):
212        if self._sslobj:
213            raise ValueError("sendto not allowed on instances of %s" %
214                             self.__class__)
215        elif addr is None:
216            return self._sock.sendto(data, flags_or_addr)
217        else:
218            return self._sock.sendto(data, flags_or_addr, addr)
219
220    def sendall(self, data, flags=0):
221        if self._sslobj:
222            if flags != 0:
223                raise ValueError(
224                    "non-zero flags not allowed in calls to sendall() on %s" %
225                    self.__class__)
226            amount = len(data)
227            count = 0
228            while (count < amount):
229                v = self.send(data[count:])
230                count += v
231            return amount
232        else:
233            return socket.sendall(self, data, flags)
234
235    def recv(self, buflen=1024, flags=0):
236        if self._sslobj:
237            if flags != 0:
238                raise ValueError(
239                    "non-zero flags not allowed in calls to recv() on %s" %
240                    self.__class__)
241            return self.read(buflen)
242        else:
243            return self._sock.recv(buflen, flags)
244
245    def recv_into(self, buffer, nbytes=None, flags=0):
246        if buffer and (nbytes is None):
247            nbytes = len(buffer)
248        elif nbytes is None:
249            nbytes = 1024
250        if self._sslobj:
251            if flags != 0:
252                raise ValueError(
253                  "non-zero flags not allowed in calls to recv_into() on %s" %
254                  self.__class__)
255            tmp_buffer = self.read(nbytes)
256            v = len(tmp_buffer)
257            buffer[:v] = tmp_buffer
258            return v
259        else:
260            return self._sock.recv_into(buffer, nbytes, flags)
261
262    def recvfrom(self, buflen=1024, flags=0):
263        if self._sslobj:
264            raise ValueError("recvfrom not allowed on instances of %s" %
265                             self.__class__)
266        else:
267            return self._sock.recvfrom(buflen, flags)
268
269    def recvfrom_into(self, buffer, nbytes=None, flags=0):
270        if self._sslobj:
271            raise ValueError("recvfrom_into not allowed on instances of %s" %
272                             self.__class__)
273        else:
274            return self._sock.recvfrom_into(buffer, nbytes, flags)
275
276    def pending(self):
277        if self._sslobj:
278            return self._sslobj.pending()
279        else:
280            return 0
281
282    def unwrap(self):
283        if self._sslobj:
284            s = self._sslobj.shutdown()
285            self._sslobj = None
286            return s
287        else:
288            raise ValueError("No SSL wrapper around " + str(self))
289
290    def shutdown(self, how):
291        self._sslobj = None
292        socket.shutdown(self, how)
293
294    def close(self):
295        if self._makefile_refs < 1:
296            self._sslobj = None
297            socket.close(self)
298        else:
299            self._makefile_refs -= 1
300
301    def do_handshake(self):
302
303        """Perform a TLS/SSL handshake."""
304
305        self._sslobj.do_handshake()
306
307    def _real_connect(self, addr, return_errno):
308        # Here we assume that the socket is client-side, and not
309        # connected at the time of the call.  We connect it, then wrap it.
310        if self._connected:
311            raise ValueError("attempt to connect already-connected SSLSocket!")
312        self._sslobj = _ssl.sslwrap(self._sock, False, self.keyfile, self.certfile,
313                                    self.cert_reqs, self.ssl_version,
314                                    self.ca_certs, self.ciphers)
315        try:
316            if return_errno:
317                rc = socket.connect_ex(self, addr)
318            else:
319                rc = None
320                socket.connect(self, addr)
321            if not rc:
322                if self.do_handshake_on_connect:
323                    self.do_handshake()
324                self._connected = True
325            return rc
326        except socket_error:
327            self._sslobj = None
328            raise
329
330    def connect(self, addr):
331        """Connects to remote ADDR, and then wraps the connection in
332        an SSL channel."""
333        self._real_connect(addr, False)
334
335    def connect_ex(self, addr):
336        """Connects to remote ADDR, and then wraps the connection in
337        an SSL channel."""
338        return self._real_connect(addr, True)
339
340    def accept(self):
341
342        """Accepts a new connection from a remote client, and returns
343        a tuple containing that new connection wrapped with a server-side
344        SSL channel, and the address of the remote client."""
345
346        newsock, addr = socket.accept(self)
347        try:
348            return (SSLSocket(newsock,
349                              keyfile=self.keyfile,
350                              certfile=self.certfile,
351                              server_side=True,
352                              cert_reqs=self.cert_reqs,
353                              ssl_version=self.ssl_version,
354                              ca_certs=self.ca_certs,
355                              ciphers=self.ciphers,
356                              do_handshake_on_connect=self.do_handshake_on_connect,
357                              suppress_ragged_eofs=self.suppress_ragged_eofs),
358                    addr)
359        except socket_error as e:
360            newsock.close()
361            raise e
362
363    def makefile(self, mode='r', bufsize=-1):
364
365        """Make and return a file-like object that
366        works with the SSL connection.  Just use the code
367        from the socket module."""
368
369        self._makefile_refs += 1
370        # close=True so as to decrement the reference count when done with
371        # the file-like object.
372        return _fileobject(self, mode, bufsize, close=True)
373
374
375
376def wrap_socket(sock, keyfile=None, certfile=None,
377                server_side=False, cert_reqs=CERT_NONE,
378                ssl_version=PROTOCOL_SSLv23, ca_certs=None,
379                do_handshake_on_connect=True,
380                suppress_ragged_eofs=True, ciphers=None):
381
382    return SSLSocket(sock, keyfile=keyfile, certfile=certfile,
383                     server_side=server_side, cert_reqs=cert_reqs,
384                     ssl_version=ssl_version, ca_certs=ca_certs,
385                     do_handshake_on_connect=do_handshake_on_connect,
386                     suppress_ragged_eofs=suppress_ragged_eofs,
387                     ciphers=ciphers)
388
389
390# some utility functions
391
392def cert_time_to_seconds(cert_time):
393
394    """Takes a date-time string in standard ASN1_print form
395    ("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return
396    a Python time value in seconds past the epoch."""
397
398    import time
399    return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
400
401PEM_HEADER = "-----BEGIN CERTIFICATE-----"
402PEM_FOOTER = "-----END CERTIFICATE-----"
403
404def DER_cert_to_PEM_cert(der_cert_bytes):
405
406    """Takes a certificate in binary DER format and returns the
407    PEM version of it as a string."""
408
409    if hasattr(base64, 'standard_b64encode'):
410        # preferred because older API gets line-length wrong
411        f = base64.standard_b64encode(der_cert_bytes)
412        return (PEM_HEADER + '\n' +
413                textwrap.fill(f, 64) + '\n' +
414                PEM_FOOTER + '\n')
415    else:
416        return (PEM_HEADER + '\n' +
417                base64.encodestring(der_cert_bytes) +
418                PEM_FOOTER + '\n')
419
420def PEM_cert_to_DER_cert(pem_cert_string):
421
422    """Takes a certificate in ASCII PEM format and returns the
423    DER-encoded version of it as a byte sequence"""
424
425    if not pem_cert_string.startswith(PEM_HEADER):
426        raise ValueError("Invalid PEM encoding; must start with %s"
427                         % PEM_HEADER)
428    if not pem_cert_string.strip().endswith(PEM_FOOTER):
429        raise ValueError("Invalid PEM encoding; must end with %s"
430                         % PEM_FOOTER)
431    d = pem_cert_string.strip()[len(PEM_HEADER):-len(PEM_FOOTER)]
432    return base64.decodestring(d)
433
434def get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):
435
436    """Retrieve the certificate from the server at the specified address,
437    and return it as a PEM-encoded string.
438    If 'ca_certs' is specified, validate the server cert against it.
439    If 'ssl_version' is specified, use it in the connection attempt."""
440
441    host, port = addr
442    if (ca_certs is not None):
443        cert_reqs = CERT_REQUIRED
444    else:
445        cert_reqs = CERT_NONE
446    s = wrap_socket(socket(), ssl_version=ssl_version,
447                    cert_reqs=cert_reqs, ca_certs=ca_certs)
448    s.connect(addr)
449    dercert = s.getpeercert(True)
450    s.close()
451    return DER_cert_to_PEM_cert(dercert)
452
453def get_protocol_name(protocol_code):
454    return _PROTOCOL_NAMES.get(protocol_code, '<unknown>')
455
456
457# a replacement for the old socket.ssl function
458
459def sslwrap_simple(sock, keyfile=None, certfile=None):
460
461    """A replacement for the old socket.ssl function.  Designed
462    for compability with Python 2.5 and earlier.  Will disappear in
463    Python 3.0."""
464
465    if hasattr(sock, "_sock"):
466        sock = sock._sock
467
468    ssl_sock = _ssl.sslwrap(sock, 0, keyfile, certfile, CERT_NONE,
469                            PROTOCOL_SSLv23, None)
470    try:
471        sock.getpeername()
472    except socket_error:
473        # no, no connection yet
474        pass
475    else:
476        # yes, do the handshake
477        ssl_sock.do_handshake()
478
479    return ssl_sock
480