Lib/ssl.py

   1 # Wrapper module for _ssl, providing some additional facilities
   2 # implemented in Python.  Written by Bill Janssen.
   3
   4 """This module provides some more Pythonic support for SSL.
   5
   6 Object types:
   7
   8   SSLSocket -- subtype of socket.socket which does SSL over the socket
   9
  10 Exceptions:
  11
  12   SSLError -- exception raised for I/O errors
  13
  14 Functions:
  15
  16   cert_time_to_seconds -- convert time string used for certificate
  17                           notBefore and notAfter functions to integer
  18                           seconds past the Epoch (the time values
  19                           returned from time.time())
  20
  21   fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
  22                           by the server running on HOST at port PORT.  No
  23                           validation of the certificate is performed.
  24
  25 Integer constants:
  26
  27 SSL_ERROR_ZERO_RETURN
  28 SSL_ERROR_WANT_READ
  29 SSL_ERROR_WANT_WRITE
  30 SSL_ERROR_WANT_X509_LOOKUP
  31 SSL_ERROR_SYSCALL
  32 SSL_ERROR_SSL
  33 SSL_ERROR_WANT_CONNECT
  34
  35 SSL_ERROR_EOF
  36 SSL_ERROR_INVALID_ERROR_CODE
  37
  38 The following group define certificate requirements that one side is
  39 allowing/requiring from the other side:
  40
  41 CERT_NONE - no certificates from the other side are required (or will
  42             be looked at if provided)
  43 CERT_OPTIONAL - certificates are not required, but if provided will be
  44                 validated, and if validation fails, the connection will
  45                 also fail
  46 CERT_REQUIRED - certificates are required, and will be validated, and
  47                 if validation fails, the connection will also fail
  48
  49 The following constants identify various SSL protocol variants:
  50
  51 PROTOCOL_SSLv2
  52 PROTOCOL_SSLv3
  53 PROTOCOL_SSLv23
  54 PROTOCOL_TLSv1
  55 """
  56
  57 import textwrap
  58
  59 import _ssl             # if we can't import it, let the error propagate
  60
  61 from _ssl import SSLError
  62 from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
  63 from _ssl import (PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23,
  64                   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
  78 from socket import getnameinfo as _getnameinfo
  79 from socket import error as socket_error
  80 from socket import dup as _dup
  81 from socket import socket, AF_INET, SOCK_STREAM
  82 import base64        # for DER-to-PEM translation
  83 import traceback
  84 import errno
  85
  86 class SSLSocket(socket):
  87
  88     """This class implements a subtype of socket.socket that wraps
  89     the underlying OS socket in an SSL context when necessary, and
  90     provides read and write methods over that channel."""
  91
  92     def __init__(self, sock=None, keyfile=None, certfile=None,
  93                  server_side=False, cert_reqs=CERT_NONE,
  94                  ssl_version=PROTOCOL_SSLv23, ca_certs=None,
  95                  do_handshake_on_connect=True,
  96                  family=AF_INET, type=SOCK_STREAM, proto=0, fileno=None,
  97                  suppress_ragged_eofs=True):
  98
  99         connected = False
 100         if sock is not None:
 101             socket.__init__(self,
 102                             family=sock.family,
 103                             type=sock.type,
 104                             proto=sock.proto,
 105                             fileno=_dup(sock.fileno()))
 106             self.settimeout(sock.gettimeout())
 107             # see if it's connected
 108             try:
 109                 sock.getpeername()
 110             except socket_error as e:
 111                 if e.errno != errno.ENOTCONN:
 112                     raise
 113             else:
 114                 connected = True
 115             sock.close()
 116         elif fileno is not None:
 117             socket.__init__(self, fileno=fileno)
 118         else:
 119             socket.__init__(self, family=family, type=type, proto=proto)
 120
 121         if certfile and not keyfile:
 122             keyfile = certfile
 123
 124         self._closed = False
 125         self._sslobj = None
 126         if connected:
 127             # create the SSL object
 128             try:
 129                 self._sslobj = _ssl.sslwrap(self, server_side,
 130                                             keyfile, certfile,
 131                                             cert_reqs, ssl_version, ca_certs)
 132                 if do_handshake_on_connect:
 133                     timeout = self.gettimeout()
 134                     if timeout == 0.0:
 135                         # non-blocking
 136                         raise ValueError("do_handshake_on_connect should not be specified for non-blocking sockets")
 137                     self.do_handshake()
 138
 139             except socket_error as x:
 140                 self.close()
 141                 raise x
 142
 143         self.keyfile = keyfile
 144         self.certfile = certfile
 145         self.cert_reqs = cert_reqs
 146         self.ssl_version = ssl_version
 147         self.ca_certs = ca_certs
 148         self.do_handshake_on_connect = do_handshake_on_connect
 149         self.suppress_ragged_eofs = suppress_ragged_eofs
 150
 151     def dup(self):
 152         raise NotImplemented("Can't dup() %s instances" %
 153                              self.__class__.__name__)
 154
 155     def _checkClosed(self, msg=None):
 156         # raise an exception here if you wish to check for spurious closes
 157         pass
 158
 159     def read(self, len=0, buffer=None):
 160         """Read up to LEN bytes and return them.
 161         Return zero-length string on EOF."""
 162
 163         self._checkClosed()
 164         try:
 165             if buffer:
 166                 v = self._sslobj.read(buffer, len)
 167             else:
 168                 v = self._sslobj.read(len or 1024)
 169             return v
 170         except SSLError as x:
 171             if x.args[0] == SSL_ERROR_EOF and self.suppress_ragged_eofs:
 172                 if buffer:
 173                     return 0
 174                 else:
 175                     return b''
 176             else:
 177                 raise
 178
 179     def write(self, data):
 180         """Write DATA to the underlying SSL channel.  Returns
 181         number of bytes of DATA actually transmitted."""
 182
 183         self._checkClosed()
 184         return self._sslobj.write(data)
 185
 186     def getpeercert(self, binary_form=False):
 187         """Returns a formatted version of the data in the
 188         certificate provided by the other end of the SSL channel.
 189         Return None if no certificate was provided, {} if a
 190         certificate was provided, but not validated."""
 191
 192         self._checkClosed()
 193         return self._sslobj.peer_certificate(binary_form)
 194
 195     def cipher(self):
 196         self._checkClosed()
 197         if not self._sslobj:
 198             return None
 199         else:
 200             return self._sslobj.cipher()
 201
 202     def send(self, data, flags=0):
 203         self._checkClosed()
 204         if self._sslobj:
 205             if flags != 0:
 206                 raise ValueError(
 207                     "non-zero flags not allowed in calls to send() on %s" %
 208                     self.__class__)
 209             while True:
 210                 try:
 211                     v = self._sslobj.write(data)
 212                 except SSLError as x:
 213                     if x.args[0] == SSL_ERROR_WANT_READ:
 214                         return 0
 215                     elif x.args[0] == SSL_ERROR_WANT_WRITE:
 216                         return 0
 217                     else:
 218                         raise
 219                 else:
 220                     return v
 221         else:
 222             return socket.send(self, data, flags)
 223
 224     def sendto(self, data, addr, flags=0):
 225         self._checkClosed()
 226         if self._sslobj:
 227             raise ValueError("sendto not allowed on instances of %s" %
 228                              self.__class__)
 229         else:
 230             return socket.sendto(self, data, addr, flags)
 231
 232     def sendall(self, data, flags=0):
 233         self._checkClosed()
 234         if self._sslobj:
 235             amount = len(data)
 236             count = 0
 237             while (count < amount):
 238                 v = self.send(data[count:])
 239                 count += v
 240             return amount
 241         else:
 242             return socket.sendall(self, data, flags)
 243
 244     def recv(self, buflen=1024, flags=0):
 245         self._checkClosed()
 246         if self._sslobj:
 247             if flags != 0:
 248                 raise ValueError(
 249                     "non-zero flags not allowed in calls to recv() on %s" %
 250                     self.__class__)
 251             return self.read(buflen)
 252         else:
 253             return socket.recv(self, buflen, flags)
 254
 255     def recv_into(self, buffer, nbytes=None, flags=0):
 256         self._checkClosed()
 257         if buffer and (nbytes is None):
 258             nbytes = len(buffer)
 259         elif nbytes is None:
 260             nbytes = 1024
 261         if self._sslobj:
 262             if flags != 0:
 263                 raise ValueError(
 264                   "non-zero flags not allowed in calls to recv_into() on %s" %
 265                   self.__class__)
 266             return self.read(nbytes, buffer)
 267         else:
 268             return socket.recv_into(self, buffer, nbytes, flags)
 269
 270     def recvfrom(self, addr, buflen=1024, flags=0):
 271         self._checkClosed()
 272         if self._sslobj:
 273             raise ValueError("recvfrom not allowed on instances of %s" %
 274                              self.__class__)
 275         else:
 276             return socket.recvfrom(self, addr, buflen, flags)
 277
 278     def recvfrom_into(self, buffer, nbytes=None, flags=0):
 279         self._checkClosed()
 280         if self._sslobj:
 281             raise ValueError("recvfrom_into not allowed on instances of %s" %
 282                              self.__class__)
 283         else:
 284             return socket.recvfrom_into(self, buffer, nbytes, flags)
 285
 286     def pending(self):
 287         self._checkClosed()
 288         if self._sslobj:
 289             return self._sslobj.pending()
 290         else:
 291             return 0
 292
 293     def shutdown(self, how):
 294         self._checkClosed()
 295         self._sslobj = None
 296         socket.shutdown(self, how)
 297
 298     def unwrap(self):
 299         if self._sslobj:
 300             s = self._sslobj.shutdown()
 301             self._sslobj = None
 302             return s
 303         else:
 304             raise ValueError("No SSL wrapper around " + str(self))
 305
 306     def _real_close(self):
 307         self._sslobj = None
 308         # self._closed = True
 309         socket._real_close(self)
 310
 311     def do_handshake(self, block=False):
 312         """Perform a TLS/SSL handshake."""
 313
 314         timeout = self.gettimeout()
 315         try:
 316             if timeout == 0.0 and block:
 317                 self.settimeout(None)
 318             self._sslobj.do_handshake()
 319         finally:
 320             self.settimeout(timeout)
 321
 322     def connect(self, addr):
 323         """Connects to remote ADDR, and then wraps the connection in
 324         an SSL channel."""
 325
 326         # Here we assume that the socket is client-side, and not
 327         # connected at the time of the call.  We connect it, then wrap it.
 328         if self._sslobj:
 329             raise ValueError("attempt to connect already-connected SSLSocket!")
 330         socket.connect(self, addr)
 331         self._sslobj = _ssl.sslwrap(self, False, self.keyfile, self.certfile,
 332                                     self.cert_reqs, self.ssl_version,
 333                                     self.ca_certs)
 334         try:
 335             if self.do_handshake_on_connect:
 336                 self.do_handshake()
 337         except:
 338             self._sslobj = None
 339             raise
 340
 341     def accept(self):
 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         return (SSLSocket(sock=newsock,
 348                           keyfile=self.keyfile, certfile=self.certfile,
 349                           server_side=True,
 350                           cert_reqs=self.cert_reqs,
 351                           ssl_version=self.ssl_version,
 352                           ca_certs=self.ca_certs,
 353                           do_handshake_on_connect=
 354                               self.do_handshake_on_connect),
 355                 addr)
 356
 357     def __del__(self):
 358         # sys.stderr.write("__del__ on %s\n" % repr(self))
 359         self._real_close()
 360
 361
 362 def wrap_socket(sock, keyfile=None, certfile=None,
 363                 server_side=False, cert_reqs=CERT_NONE,
 364                 ssl_version=PROTOCOL_SSLv23, ca_certs=None,
 365                 do_handshake_on_connect=True,
 366                 suppress_ragged_eofs=True):
 367
 368     return SSLSocket(sock=sock, keyfile=keyfile, certfile=certfile,
 369                      server_side=server_side, cert_reqs=cert_reqs,
 370                      ssl_version=ssl_version, ca_certs=ca_certs,
 371                      do_handshake_on_connect=do_handshake_on_connect,
 372                      suppress_ragged_eofs=suppress_ragged_eofs)
 373
 374 # some utility functions
 375
 376 def cert_time_to_seconds(cert_time):
 377     """Takes a date-time string in standard ASN1_print form
 378     ("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return
 379     a Python time value in seconds past the epoch."""
 380
 381     import time
 382     return time.mktime(time.strptime(cert_time, "%b %d %H:%M:%S %Y GMT"))
 383
 384 PEM_HEADER = "-----BEGIN CERTIFICATE-----"
 385 PEM_FOOTER = "-----END CERTIFICATE-----"
 386
 387 def DER_cert_to_PEM_cert(der_cert_bytes):
 388     """Takes a certificate in binary DER format and returns the
 389     PEM version of it as a string."""
 390
 391     f = str(base64.standard_b64encode(der_cert_bytes), 'ASCII', 'strict')
 392     return (PEM_HEADER + '\n' +
 393             textwrap.fill(f, 64) + '\n' +
 394             PEM_FOOTER + '\n')
 395
 396 def PEM_cert_to_DER_cert(pem_cert_string):
 397     """Takes a certificate in ASCII PEM format and returns the
 398     DER-encoded version of it as a byte sequence"""
 399
 400     if not pem_cert_string.startswith(PEM_HEADER):
 401         raise ValueError("Invalid PEM encoding; must start with %s"
 402                          % PEM_HEADER)
 403     if not pem_cert_string.strip().endswith(PEM_FOOTER):
 404         raise ValueError("Invalid PEM encoding; must end with %s"
 405                          % PEM_FOOTER)
 406     d = pem_cert_string.strip()[len(PEM_HEADER):-len(PEM_FOOTER)]
 407     return base64.decodebytes(d.encode('ASCII', 'strict'))
 408
 409 def get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):
 410     """Retrieve the certificate from the server at the specified address,
 411     and return it as a PEM-encoded string.
 412     If 'ca_certs' is specified, validate the server cert against it.
 413     If 'ssl_version' is specified, use it in the connection attempt."""
 414
 415     host, port = addr
 416     if (ca_certs is not None):
 417         cert_reqs = CERT_REQUIRED
 418     else:
 419         cert_reqs = CERT_NONE
 420     s = wrap_socket(socket(), ssl_version=ssl_version,
 421                     cert_reqs=cert_reqs, ca_certs=ca_certs)
 422     s.connect(addr)
 423     dercert = s.getpeercert(True)
 424     s.close()
 425     return DER_cert_to_PEM_cert(dercert)
 426
 427 def get_protocol_name(protocol_code):
 428     if protocol_code == PROTOCOL_TLSv1:
 429         return "TLSv1"
 430     elif protocol_code == PROTOCOL_SSLv23:
 431         return "SSLv23"
 432     elif protocol_code == PROTOCOL_SSLv2:
 433         return "SSLv2"
 434     elif protocol_code == PROTOCOL_SSLv3:
 435         return "SSLv3"
 436     else:
 437         return "<unknown>"