1 # Wrapper module for _ssl, providing some additional facilities

     2 # implemented in Python.  Written by Bill Janssen.

     3 

     4 """\

     5 This module provides some more Pythonic support for SSL.

     6 

     7 Object types:

     8 

     9   SSLSocket -- subtype of socket.socket which does SSL over the socket

    10 

    11 Exceptions:

    12 

    13   SSLError -- exception raised for I/O errors

    14 

    15 Functions:

    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 

    26 Integer constants:

    27 

    28 SSL_ERROR_ZERO_RETURN

    29 SSL_ERROR_WANT_READ

    30 SSL_ERROR_WANT_WRITE

    31 SSL_ERROR_WANT_X509_LOOKUP

    32 SSL_ERROR_SYSCALL

    33 SSL_ERROR_SSL

    34 SSL_ERROR_WANT_CONNECT

    35 

    36 SSL_ERROR_EOF

    37 SSL_ERROR_INVALID_ERROR_CODE

    38 

    39 The following group define certificate requirements that one side is

    40 allowing/requiring from the other side:

    41 

    42 CERT_NONE - no certificates from the other side are required (or will

    43             be looked at if provided)

    44 CERT_OPTIONAL - certificates are not required, but if provided will be

    45                 validated, and if validation fails, the connection will

    46                 also fail

    47 CERT_REQUIRED - certificates are required, and will be validated, and

    48                 if validation fails, the connection will also fail

    49 

    50 The following constants identify various SSL protocol variants:

    51 

    52 PROTOCOL_SSLv2

    53 PROTOCOL_SSLv3

    54 PROTOCOL_SSLv23

    55 PROTOCOL_TLSv1

    56 """

    57 

    58 import textwrap

    59 

    60 import _ssl             # if we can't import it, let the error propagate

    61 

    62 from _ssl import SSLError

    63 from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED

    64 from _ssl import PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1

    65 from _ssl import RAND_status, RAND_egd, RAND_add

    66 from _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

    76 

    77 from socket import socket, _fileobject

    78 from socket import getnameinfo as _getnameinfo

    79 import base64        # for DER-to-PEM translation

    80 

    81 class SSLSocket (socket):

    82 

    83     """This class implements a subtype of socket.socket that wraps

    84     the underlying OS socket in an SSL context when necessary, and

    85     provides read and write methods over that channel."""

    86 

    87     def __init__(self, sock, keyfile=None, certfile=None,

    88                  server_side=False, cert_reqs=CERT_NONE,

    89                  ssl_version=PROTOCOL_SSLv23, ca_certs=None,

    90                  do_handshake_on_connect=True,

    91                  suppress_ragged_eofs=True):

    92         socket.__init__(self, _sock=sock._sock)

    93         # the initializer for socket trashes the methods (tsk, tsk), so...

    94         self.send = lambda data, flags=0: SSLSocket.send(self, data, flags)

    95         self.sendto = lambda data, addr, flags=0: SSLSocket.sendto(self, data, addr, flags)

    96         self.recv = lambda buflen=1024, flags=0: SSLSocket.recv(self, buflen, flags)

    97         self.recvfrom = lambda addr, buflen=1024, flags=0: SSLSocket.recvfrom(self, addr, buflen, flags)

    98         self.recv_into = lambda buffer, nbytes=None, flags=0: SSLSocket.recv_into(self, buffer, nbytes, flags)

    99         self.recvfrom_into = lambda buffer, nbytes=None, flags=0: SSLSocket.recvfrom_into(self, buffer, nbytes, flags)

   100 

   101         if certfile and not keyfile:

   102             keyfile = certfile

   103         # see if it's connected

   104         try:

   105             socket.getpeername(self)

   106         except:

   107             # no, no connection yet

   108             self._sslobj = None

   109         else:

   110             # yes, create the SSL object

   111             self._sslobj = _ssl.sslwrap(self._sock, server_side,

   112                                         keyfile, certfile,

   113                                         cert_reqs, ssl_version, ca_certs)

   114             if do_handshake_on_connect:

   115                 timeout = self.gettimeout()

   116                 try:

   117                     self.settimeout(None)

   118                     self.do_handshake()

   119                 finally:

   120                     self.settimeout(timeout)

   121         self.keyfile = keyfile

   122         self.certfile = certfile

   123         self.cert_reqs = cert_reqs

   124         self.ssl_version = ssl_version

   125         self.ca_certs = ca_certs

   126         self.do_handshake_on_connect = do_handshake_on_connect

   127         self.suppress_ragged_eofs = suppress_ragged_eofs

   128         self._makefile_refs = 0

   129 

   130     def read(self, len=1024):

   131 

   132         """Read up to LEN bytes and return them.

   133         Return zero-length string on EOF."""

   134 

   135         try:

   136             return self._sslobj.read(len)

   137         except SSLError, x:

   138             if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:

   139                 return ''

   140             else:

   141                 raise

   142 

   143     def write(self, data):

   144 

   145         """Write DATA to the underlying SSL channel.  Returns

   146         number of bytes of DATA actually transmitted."""

   147 

   148         return self._sslobj.write(data)

   149 

   150     def getpeercert(self, binary_form=False):

   151 

   152         """Returns a formatted version of the data in the

   153         certificate provided by the other end of the SSL channel.

   154         Return None if no certificate was provided, {} if a

   155         certificate was provided, but not validated."""

   156 

   157         return self._sslobj.peer_certificate(binary_form)

   158 

   159     def cipher (self):

   160 

   161         if not self._sslobj:

   162             return None

   163         else:

   164             return self._sslobj.cipher()

   165 

   166     def send (self, data, flags=0):

   167         if self._sslobj:

   168             if flags != 0:

   169                 raise ValueError(

   170                     "non-zero flags not allowed in calls to send() on %s" %

   171                     self.__class__)

   172             while True:

   173                 try:

   174                     v = self._sslobj.write(data)

   175                 except SSLError, x:

   176                     if x.args[0] == SSL_ERROR_WANT_READ:

   177                         return 0

   178                     elif x.args[0] == SSL_ERROR_WANT_WRITE:

   179                         return 0

   180                     else:

   181                         raise

   182                 else:

   183                     return v

   184         else:

   185             return socket.send(self, data, flags)

   186 

   187     def sendto (self, data, addr, flags=0):

   188         if self._sslobj:

   189             raise ValueError("sendto not allowed on instances of %s" %

   190                              self.__class__)

   191         else:

   192             return socket.sendto(self, data, addr, flags)

   193 

   194     def sendall (self, data, flags=0):

   195         if self._sslobj:

   196             if flags != 0:

   197                 raise ValueError(

   198                     "non-zero flags not allowed in calls to sendall() on %s" %

   199                     self.__class__)

   200             amount = len(data)

   201             count = 0

   202             while (count < amount):

   203                 v = self.send(data[count:])

   204                 count += v

   205             return amount

   206         else:

   207             return socket.sendall(self, data, flags)

   208 

   209     def recv (self, buflen=1024, flags=0):

   210         if self._sslobj:

   211             if flags != 0:

   212                 raise ValueError(

   213                     "non-zero flags not allowed in calls to sendall() on %s" %

   214                     self.__class__)

   215             while True:

   216                 try:

   217                     return self.read(buflen)

   218                 except SSLError, x:

   219                     if x.args[0] == SSL_ERROR_WANT_READ:

   220                         continue

   221                     else:

   222                         raise x

   223         else:

   224             return socket.recv(self, buflen, flags)

   225 

   226     def recv_into (self, buffer, nbytes=None, flags=0):

   227         if buffer and (nbytes is None):

   228             nbytes = len(buffer)

   229         elif nbytes is None:

   230             nbytes = 1024

   231         if self._sslobj:

   232             if flags != 0:

   233                 raise ValueError(

   234                   "non-zero flags not allowed in calls to recv_into() on %s" %

   235                   self.__class__)

   236             while True:

   237                 try:

   238                     tmp_buffer = self.read(nbytes)

   239                     v = len(tmp_buffer)

   240                     buffer[:v] = tmp_buffer

   241                     return v

   242                 except SSLError as x:

   243                     if x.args[0] == SSL_ERROR_WANT_READ:

   244                         continue

   245                     else:

   246                         raise x

   247         else:

   248             return socket.recv_into(self, buffer, nbytes, flags)

   249 

   250     def recvfrom (self, addr, buflen=1024, flags=0):

   251         if self._sslobj:

   252             raise ValueError("recvfrom not allowed on instances of %s" %

   253                              self.__class__)

   254         else:

   255             return socket.recvfrom(self, addr, buflen, flags)

   256 

   257     def recvfrom_into (self, buffer, nbytes=None, flags=0):

   258         if self._sslobj:

   259             raise ValueError("recvfrom_into not allowed on instances of %s" %

   260                              self.__class__)

   261         else:

   262             return socket.recvfrom_into(self, buffer, nbytes, flags)

   263 

   264     def pending (self):

   265         if self._sslobj:

   266             return self._sslobj.pending()

   267         else:

   268             return 0

   269 

   270     def unwrap (self):

   271         if self._sslobj:

   272             s = self._sslobj.shutdown()

   273             self._sslobj = None

   274             return s

   275         else:

   276             raise ValueError("No SSL wrapper around " + str(self))

   277 

   278     def shutdown (self, how):

   279         self._sslobj = None

   280         socket.shutdown(self, how)

   281 

   282     def close (self):

   283         if self._makefile_refs < 1:

   284             self._sslobj = None

   285             socket.close(self)

   286         else:

   287             self._makefile_refs -= 1

   288 

   289     def do_handshake (self):

   290 

   291         """Perform a TLS/SSL handshake."""

   292 

   293         self._sslobj.do_handshake()

   294 

   295     def connect(self, addr):

   296 

   297         """Connects to remote ADDR, and then wraps the connection in

   298         an SSL channel."""

   299 

   300         # Here we assume that the socket is client-side, and not

   301         # connected at the time of the call.  We connect it, then wrap it.

   302         if self._sslobj:

   303             raise ValueError("attempt to connect already-connected SSLSocket!")

   304         socket.connect(self, addr)

   305         self._sslobj = _ssl.sslwrap(self._sock, False, self.keyfile, self.certfile,

   306                                     self.cert_reqs, self.ssl_version,

   307                                     self.ca_certs)

   308         if self.do_handshake_on_connect:

   309             self.do_handshake()

   310 

   311     def accept(self):

   312 

   313         """Accepts a new connection from a remote client, and returns

   314         a tuple containing that new connection wrapped with a server-side

   315         SSL channel, and the address of the remote client."""

   316 

   317         newsock, addr = socket.accept(self)

   318         return (SSLSocket(newsock,

   319                           keyfile=self.keyfile,

   320                           certfile=self.certfile,

   321                           server_side=True,

   322                           cert_reqs=self.cert_reqs,

   323                           ssl_version=self.ssl_version,

   324                           ca_certs=self.ca_certs,

   325                           do_handshake_on_connect=self.do_handshake_on_connect,

   326                           suppress_ragged_eofs=self.suppress_ragged_eofs),

   327                 addr)

   328 

   329     def makefile(self, mode='r', bufsize=-1):

   330 

   331         """Make and return a file-like object that

   332         works with the SSL connection.  Just use the code

   333         from the socket module."""

   334 

   335         self._makefile_refs += 1

   336         return _fileobject(self, mode, bufsize)

   337 

   338 

   339 

   340 def wrap_socket(sock, keyfile=None, certfile=None,

   341                 server_side=False, cert_reqs=CERT_NONE,

   342                 ssl_version=PROTOCOL_SSLv23, ca_certs=None,

   343                 do_handshake_on_connect=True,

   344                 suppress_ragged_eofs=True):

   345 

   346     return SSLSocket(sock, keyfile=keyfile, certfile=certfile,

   347                      server_side=server_side, cert_reqs=cert_reqs,

   348                      ssl_version=ssl_version, ca_certs=ca_certs,

   349                      do_handshake_on_connect=do_handshake_on_connect,

   350                      suppress_ragged_eofs=suppress_ragged_eofs)

   351 

   352 

   353 # some utility functions

   354 

   355 def cert_time_to_seconds(cert_time):

   356 

   357     """Takes a date-time string in standard ASN1_print form

   358     ("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return

   359     a Python time value in seconds past the epoch."""

   360 

   361     import time

   362     return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))

   363 

   364 PEM_HEADER = "-----BEGIN CERTIFICATE-----"

   365 PEM_FOOTER = "-----END CERTIFICATE-----"

   366 

   367 def DER_cert_to_PEM_cert(der_cert_bytes):

   368 

   369     """Takes a certificate in binary DER format and returns the

   370     PEM version of it as a string."""

   371 

   372     if hasattr(base64, 'standard_b64encode'):

   373         # preferred because older API gets line-length wrong

   374         f = base64.standard_b64encode(der_cert_bytes)

   375         return (PEM_HEADER + '\n' +

   376                 textwrap.fill(f, 64) +

   377                 PEM_FOOTER + '\n')

   378     else:

   379         return (PEM_HEADER + '\n' +

   380                 base64.encodestring(der_cert_bytes) +

   381                 PEM_FOOTER + '\n')

   382 

   383 def PEM_cert_to_DER_cert(pem_cert_string):

   384 

   385     """Takes a certificate in ASCII PEM format and returns the

   386     DER-encoded version of it as a byte sequence"""

   387 

   388     if not pem_cert_string.startswith(PEM_HEADER):

   389         raise ValueError("Invalid PEM encoding; must start with %s"

   390                          % PEM_HEADER)

   391     if not pem_cert_string.strip().endswith(PEM_FOOTER):

   392         raise ValueError("Invalid PEM encoding; must end with %s"

   393                          % PEM_FOOTER)

   394     d = pem_cert_string.strip()[len(PEM_HEADER):-len(PEM_FOOTER)]

   395     return base64.decodestring(d)

   396 

   397 def get_server_certificate (addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):

   398 

   399     """Retrieve the certificate from the server at the specified address,

   400     and return it as a PEM-encoded string.

   401     If 'ca_certs' is specified, validate the server cert against it.

   402     If 'ssl_version' is specified, use it in the connection attempt."""

   403 

   404     host, port = addr

   405     if (ca_certs is not None):

   406         cert_reqs = CERT_REQUIRED

   407     else:

   408         cert_reqs = CERT_NONE

   409     s = wrap_socket(socket(), ssl_version=ssl_version,

   410                     cert_reqs=cert_reqs, ca_certs=ca_certs)

   411     s.connect(addr)

   412     dercert = s.getpeercert(True)

   413     s.close()

   414     return DER_cert_to_PEM_cert(dercert)

   415 

   416 def get_protocol_name (protocol_code):

   417     if protocol_code == PROTOCOL_TLSv1:

   418         return "TLSv1"

   419     elif protocol_code == PROTOCOL_SSLv23:

   420         return "SSLv23"

   421     elif protocol_code == PROTOCOL_SSLv2:

   422         return "SSLv2"

   423     elif protocol_code == PROTOCOL_SSLv3:

   424         return "SSLv3"

   425     else:

   426         return "<unknown>"

   427 

   428 

   429 # a replacement for the old socket.ssl function

   430 

   431 def sslwrap_simple (sock, keyfile=None, certfile=None):

   432 

   433     """A replacement for the old socket.ssl function.  Designed

   434     for compability with Python 2.5 and earlier.  Will disappear in

   435     Python 3.0."""

   436 

   437     if hasattr(sock, "_sock"):

   438         sock = sock._sock

   439 

   440     ssl_sock = _ssl.sslwrap(sock, 0, keyfile, certfile, CERT_NONE,

   441                             PROTOCOL_SSLv23, None)

   442     try:

   443         sock.getpeername()

   444     except:

   445         # no, no connection yet

   446         pass

   447     else:

   448         # yes, do the handshake

   449         ssl_sock.do_handshake()

   450 

   451     return ssl_sock