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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
84except ImportError:
85    pass
86else:
87    _PROTOCOL_NAMES[PROTOCOL_SSLv2] = "SSLv2"
88
89from socket import socket, _fileobject, _delegate_methods, error as socket_error
90from socket import getnameinfo as _getnameinfo
91import base64        # for DER-to-PEM translation
92import errno
93
94class SSLSocket(socket):
95
96    """This class implements a subtype of socket.socket that wraps
97    the underlying OS socket in an SSL context when necessary, and
98    provides read and write methods over that channel."""
99
100    def __init__(self, sock, keyfile=None, certfile=None,
101                 server_side=False, cert_reqs=CERT_NONE,
102                 ssl_version=PROTOCOL_SSLv23, ca_certs=None,
103                 do_handshake_on_connect=True,
104                 suppress_ragged_eofs=True, ciphers=None):
105        socket.__init__(self, _sock=sock._sock)
106        # The initializer for socket overrides the methods send(), recv(), etc.
107        # in the instancce, which we don't need -- but we want to provide the
108        # methods defined in SSLSocket.
109        for attr in _delegate_methods:
110            try:
111                delattr(self, attr)
112            except AttributeError:
113                pass
114
115        if certfile and not keyfile:
116            keyfile = certfile
117        # see if it's connected
118        try:
119            socket.getpeername(self)
120        except socket_error, e:
121            if e.errno != errno.ENOTCONN:
122                raise
123            # no, no connection yet
124            self._connected = False
125            self._sslobj = None
126        else:
127            # yes, create the SSL object
128            self._connected = True
129            self._sslobj = _ssl.sslwrap(self._sock, server_side,
130                                        keyfile, certfile,
131                                        cert_reqs, ssl_version, ca_certs,
132                                        ciphers)
133            if do_handshake_on_connect:
134                self.do_handshake()
135        self.keyfile = keyfile
136        self.certfile = certfile
137        self.cert_reqs = cert_reqs
138        self.ssl_version = ssl_version
139        self.ca_certs = ca_certs
140        self.ciphers = ciphers
141        self.do_handshake_on_connect = do_handshake_on_connect
142        self.suppress_ragged_eofs = suppress_ragged_eofs
143        self._makefile_refs = 0
144
145    def read(self, len=1024):
146
147        """Read up to LEN bytes and return them.
148        Return zero-length string on EOF."""
149
150        try:
151            return self._sslobj.read(len)
152        except SSLError, x:
153            if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:
154                return ''
155            else:
156                raise
157
158    def write(self, data):
159
160        """Write DATA to the underlying SSL channel.  Returns
161        number of bytes of DATA actually transmitted."""
162
163        return self._sslobj.write(data)
164
165    def getpeercert(self, binary_form=False):
166
167        """Returns a formatted version of the data in the
168        certificate provided by the other end of the SSL channel.
169        Return None if no certificate was provided, {} if a
170        certificate was provided, but not validated."""
171
172        return self._sslobj.peer_certificate(binary_form)
173
174    def cipher(self):
175
176        if not self._sslobj:
177            return None
178        else:
179            return self._sslobj.cipher()
180
181    def send(self, data, flags=0):
182        if self._sslobj:
183            if flags != 0:
184                raise ValueError(
185                    "non-zero flags not allowed in calls to send() on %s" %
186                    self.__class__)
187            while True:
188                try:
189                    v = self._sslobj.write(data)
190                except SSLError, x:
191                    if x.args[0] == SSL_ERROR_WANT_READ:
192                        return 0
193                    elif x.args[0] == SSL_ERROR_WANT_WRITE:
194                        return 0
195                    else:
196                        raise
197                else:
198                    return v
199        else:
200            return self._sock.send(data, flags)
201
202    def sendto(self, data, flags_or_addr, addr=None):
203        if self._sslobj:
204            raise ValueError("sendto not allowed on instances of %s" %
205                             self.__class__)
206        elif addr is None:
207            return self._sock.sendto(data, flags_or_addr)
208        else:
209            return self._sock.sendto(data, flags_or_addr, addr)
210
211    def sendall(self, data, flags=0):
212        if self._sslobj:
213            if flags != 0:
214                raise ValueError(
215                    "non-zero flags not allowed in calls to sendall() on %s" %
216                    self.__class__)
217            amount = len(data)
218            count = 0
219            while (count < amount):
220                v = self.send(data[count:])
221                count += v
222            return amount
223        else:
224            return socket.sendall(self, data, flags)
225
226    def recv(self, buflen=1024, flags=0):
227        if self._sslobj:
228            if flags != 0:
229                raise ValueError(
230                    "non-zero flags not allowed in calls to recv() on %s" %
231                    self.__class__)
232            return self.read(buflen)
233        else:
234            return self._sock.recv(buflen, flags)
235
236    def recv_into(self, buffer, nbytes=None, flags=0):
237        if buffer and (nbytes is None):
238            nbytes = len(buffer)
239        elif nbytes is None:
240            nbytes = 1024
241        if self._sslobj:
242            if flags != 0:
243                raise ValueError(
244                  "non-zero flags not allowed in calls to recv_into() on %s" %
245                  self.__class__)
246            tmp_buffer = self.read(nbytes)
247            v = len(tmp_buffer)
248            buffer[:v] = tmp_buffer
249            return v
250        else:
251            return self._sock.recv_into(buffer, nbytes, flags)
252
253    def recvfrom(self, buflen=1024, flags=0):
254        if self._sslobj:
255            raise ValueError("recvfrom not allowed on instances of %s" %
256                             self.__class__)
257        else:
258            return self._sock.recvfrom(buflen, flags)
259
260    def recvfrom_into(self, buffer, nbytes=None, flags=0):
261        if self._sslobj:
262            raise ValueError("recvfrom_into not allowed on instances of %s" %
263                             self.__class__)
264        else:
265            return self._sock.recvfrom_into(buffer, nbytes, flags)
266
267    def pending(self):
268        if self._sslobj:
269            return self._sslobj.pending()
270        else:
271            return 0
272
273    def unwrap(self):
274        if self._sslobj:
275            s = self._sslobj.shutdown()
276            self._sslobj = None
277            return s
278        else:
279            raise ValueError("No SSL wrapper around " + str(self))
280
281    def shutdown(self, how):
282        self._sslobj = None
283        socket.shutdown(self, how)
284
285    def close(self):
286        if self._makefile_refs < 1:
287            self._sslobj = None
288            socket.close(self)
289        else:
290            self._makefile_refs -= 1
291
292    def do_handshake(self):
293
294        """Perform a TLS/SSL handshake."""
295
296        self._sslobj.do_handshake()
297
298    def _real_connect(self, addr, return_errno):
299        # Here we assume that the socket is client-side, and not
300        # connected at the time of the call.  We connect it, then wrap it.
301        if self._connected:
302            raise ValueError("attempt to connect already-connected SSLSocket!")
303        self._sslobj = _ssl.sslwrap(self._sock, False, self.keyfile, self.certfile,
304                                    self.cert_reqs, self.ssl_version,
305                                    self.ca_certs, self.ciphers)
306        try:
307            socket.connect(self, addr)
308            if self.do_handshake_on_connect:
309                self.do_handshake()
310        except socket_error as e:
311            if return_errno:
312                return e.errno
313            else:
314                self._sslobj = None
315                raise e
316        self._connected = True
317        return 0
318
319    def connect(self, addr):
320        """Connects to remote ADDR, and then wraps the connection in
321        an SSL channel."""
322        self._real_connect(addr, False)
323
324    def connect_ex(self, addr):
325        """Connects to remote ADDR, and then wraps the connection in
326        an SSL channel."""
327        return self._real_connect(addr, True)
328
329    def accept(self):
330
331        """Accepts a new connection from a remote client, and returns
332        a tuple containing that new connection wrapped with a server-side
333        SSL channel, and the address of the remote client."""
334
335        newsock, addr = socket.accept(self)
336        return (SSLSocket(newsock,
337                          keyfile=self.keyfile,
338                          certfile=self.certfile,
339                          server_side=True,
340                          cert_reqs=self.cert_reqs,
341                          ssl_version=self.ssl_version,
342                          ca_certs=self.ca_certs,
343                          ciphers=self.ciphers,
344                          do_handshake_on_connect=self.do_handshake_on_connect,
345                          suppress_ragged_eofs=self.suppress_ragged_eofs),
346                addr)
347
348    def makefile(self, mode='r', bufsize=-1):
349
350        """Make and return a file-like object that
351        works with the SSL connection.  Just use the code
352        from the socket module."""
353
354        self._makefile_refs += 1
355        # close=True so as to decrement the reference count when done with
356        # the file-like object.
357        return _fileobject(self, mode, bufsize, close=True)
358
359
360
361def wrap_socket(sock, keyfile=None, certfile=None,
362                server_side=False, cert_reqs=CERT_NONE,
363                ssl_version=PROTOCOL_SSLv23, ca_certs=None,
364                do_handshake_on_connect=True,
365                suppress_ragged_eofs=True, ciphers=None):
366
367    return SSLSocket(sock, keyfile=keyfile, certfile=certfile,
368                     server_side=server_side, cert_reqs=cert_reqs,
369                     ssl_version=ssl_version, ca_certs=ca_certs,
370                     do_handshake_on_connect=do_handshake_on_connect,
371                     suppress_ragged_eofs=suppress_ragged_eofs,
372                     ciphers=ciphers)
373
374
375# some utility functions
376
377def cert_time_to_seconds(cert_time):
378
379    """Takes a date-time string in standard ASN1_print form
380    ("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return
381    a Python time value in seconds past the epoch."""
382
383    import time
384    return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
385
386PEM_HEADER = "-----BEGIN CERTIFICATE-----"
387PEM_FOOTER = "-----END CERTIFICATE-----"
388
389def DER_cert_to_PEM_cert(der_cert_bytes):
390
391    """Takes a certificate in binary DER format and returns the
392    PEM version of it as a string."""
393
394    if hasattr(base64, 'standard_b64encode'):
395        # preferred because older API gets line-length wrong
396        f = base64.standard_b64encode(der_cert_bytes)
397        return (PEM_HEADER + '\n' +
398                textwrap.fill(f, 64) + '\n' +
399                PEM_FOOTER + '\n')
400    else:
401        return (PEM_HEADER + '\n' +
402                base64.encodestring(der_cert_bytes) +
403                PEM_FOOTER + '\n')
404
405def PEM_cert_to_DER_cert(pem_cert_string):
406
407    """Takes a certificate in ASCII PEM format and returns the
408    DER-encoded version of it as a byte sequence"""
409
410    if not pem_cert_string.startswith(PEM_HEADER):
411        raise ValueError("Invalid PEM encoding; must start with %s"
412                         % PEM_HEADER)
413    if not pem_cert_string.strip().endswith(PEM_FOOTER):
414        raise ValueError("Invalid PEM encoding; must end with %s"
415                         % PEM_FOOTER)
416    d = pem_cert_string.strip()[len(PEM_HEADER):-len(PEM_FOOTER)]
417    return base64.decodestring(d)
418
419def get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):
420
421    """Retrieve the certificate from the server at the specified address,
422    and return it as a PEM-encoded string.
423    If 'ca_certs' is specified, validate the server cert against it.
424    If 'ssl_version' is specified, use it in the connection attempt."""
425
426    host, port = addr
427    if (ca_certs is not None):
428        cert_reqs = CERT_REQUIRED
429    else:
430        cert_reqs = CERT_NONE
431    s = wrap_socket(socket(), ssl_version=ssl_version,
432                    cert_reqs=cert_reqs, ca_certs=ca_certs)
433    s.connect(addr)
434    dercert = s.getpeercert(True)
435    s.close()
436    return DER_cert_to_PEM_cert(dercert)
437
438def get_protocol_name(protocol_code):
439    return _PROTOCOL_NAMES.get(protocol_code, '<unknown>')
440
441
442# a replacement for the old socket.ssl function
443
444def sslwrap_simple(sock, keyfile=None, certfile=None):
445
446    """A replacement for the old socket.ssl function.  Designed
447    for compability with Python 2.5 and earlier.  Will disappear in
448    Python 3.0."""
449
450    if hasattr(sock, "_sock"):
451        sock = sock._sock
452
453    ssl_sock = _ssl.sslwrap(sock, 0, keyfile, certfile, CERT_NONE,
454                            PROTOCOL_SSLv23, None)
455    try:
456        sock.getpeername()
457    except socket_error:
458        # no, no connection yet
459        pass
460    else:
461        # yes, do the handshake
462        ssl_sock.do_handshake()
463
464    return ssl_sock
465