Lib/ssl.py

   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, error as socket_error
  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 socket_error:
 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 socket_error:
 445         # no, no connection yet
 446         pass
 447     else:
 448         # yes, do the handshake
 449         ssl_sock.do_handshake()
 450
 451     return ssl_sock