Lib/ssl.py

# Wrapper module for _ssl, providing some additional facilities
# implemented in Python.  Written by Bill Janssen.

"""\
This module provides some more Pythonic support for SSL.

Object types:

  sslsocket -- subtype of socket.socket which does SSL over the socket

Exceptions:

  sslerror -- exception raised for I/O errors

Functions:

  cert_time_to_seconds -- convert time string used for certificate
                          notBefore and notAfter functions to integer
                          seconds past the Epoch (the time values
                          returned from time.time())

  fetch_server_certificate (HOST, PORT) -- fetch the certificate provided
                          by the server running on HOST at port PORT.  No
                          validation of the certificate is performed.

Integer constants:

SSL_ERROR_ZERO_RETURN
SSL_ERROR_WANT_READ
SSL_ERROR_WANT_WRITE
SSL_ERROR_WANT_X509_LOOKUP
SSL_ERROR_SYSCALL
SSL_ERROR_SSL
SSL_ERROR_WANT_CONNECT

SSL_ERROR_EOF
SSL_ERROR_INVALID_ERROR_CODE

The following group define certificate requirements that one side is
allowing/requiring from the other side:

CERT_NONE - no certificates from the other side are required (or will
            be looked at if provided)
CERT_OPTIONAL - certificates are not required, but if provided will be
                validated, and if validation fails, the connection will
                also fail
CERT_REQUIRED - certificates are required, and will be validated, and
                if validation fails, the connection will also fail

The following constants identify various SSL protocol variants:

PROTOCOL_SSLv2
PROTOCOL_SSLv3
PROTOCOL_SSLv23
PROTOCOL_TLSv1
"""

import os, sys

import _ssl             # if we can't import it, let the error propagate
from _ssl import sslerror
from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
from _ssl import PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1
from _ssl import \
     SSL_ERROR_ZERO_RETURN, \
     SSL_ERROR_WANT_READ, \
     SSL_ERROR_WANT_WRITE, \
     SSL_ERROR_WANT_X509_LOOKUP, \
     SSL_ERROR_SYSCALL, \
     SSL_ERROR_SSL, \
     SSL_ERROR_WANT_CONNECT, \
     SSL_ERROR_EOF, \
     SSL_ERROR_INVALID_ERROR_CODE

from socket import socket
from socket import getnameinfo as _getnameinfo


class sslsocket (socket):

    """This class implements a subtype of socket.socket that wraps
    the underlying OS socket in an SSL context when necessary, and
    provides read and write methods over that channel."""

    def __init__(self, sock, keyfile=None, certfile=None,
                 server_side=False, cert_reqs=CERT_NONE,
                 ssl_version=PROTOCOL_SSLv23, ca_certs=None):
        socket.__init__(self, _sock=sock._sock)
        if certfile and not keyfile:
            keyfile = certfile
        # see if it's connected
        try:
            socket.getpeername(self)
        except:
            # no, no connection yet
            self._sslobj = None
        else:
            # yes, create the SSL object
            self._sslobj = _ssl.sslwrap(self._sock, server_side,
                                        keyfile, certfile,
                                        cert_reqs, ssl_version, ca_certs)
        self.keyfile = keyfile
        self.certfile = certfile
        self.cert_reqs = cert_reqs
        self.ssl_version = ssl_version
        self.ca_certs = ca_certs

    def read(self, len=1024):

        """Read up to LEN bytes and return them.
        Return zero-length string on EOF."""

        return self._sslobj.read(len)

    def write(self, data):

        """Write DATA to the underlying SSL channel.  Returns
        number of bytes of DATA actually transmitted."""

        return self._sslobj.write(data)

    def getpeercert(self):

        """Returns a formatted version of the data in the
        certificate provided by the other end of the SSL channel.
        Return None if no certificate was provided, {} if a
        certificate was provided, but not validated."""

        return self._sslobj.peer_certificate()

    def send (self, data, flags=0):
        if self._sslobj:
            if flags != 0:
                raise ValueError(
                    "non-zero flags not allowed in calls to send() on %s" %
                    self.__class__)
            return self._sslobj.write(data)
        else:
            return socket.send(self, data, flags)

    def send_to (self, data, addr, flags=0):
        if self._sslobj:
            raise ValueError("send_to not allowed on instances of %s" %
                             self.__class__)
        else:
            return socket.send_to(self, data, addr, flags)

    def sendall (self, data, flags=0):
        if self._sslobj:
            if flags != 0:
                raise ValueError(
                    "non-zero flags not allowed in calls to sendall() on %s" %
                    self.__class__)
            return self._sslobj.write(data)
        else:
            return socket.sendall(self, data, flags)

    def recv (self, buflen=1024, flags=0):
        if self._sslobj:
            if flags != 0:
                raise ValueError(
                    "non-zero flags not allowed in calls to sendall() on %s" %
                    self.__class__)
            return self._sslobj.read(data, buflen)
        else:
            return socket.recv(self, buflen, flags)

    def recv_from (self, addr, buflen=1024, flags=0):
        if self._sslobj:
            raise ValueError("recv_from not allowed on instances of %s" %
                             self.__class__)
        else:
            return socket.recv_from(self, addr, buflen, flags)

    def ssl_shutdown(self):

        """Shuts down the SSL channel over this socket (if active),
        without closing the socket connection."""

        if self._sslobj:
            self._sslobj.shutdown()
            self._sslobj = None

    def shutdown(self, how):
        self.ssl_shutdown()
        socket.shutdown(self, how)

    def close(self):
        self.ssl_shutdown()
        socket.close(self)

    def connect(self, addr):

        """Connects to remote ADDR, and then wraps the connection in
        an SSL channel."""

        # Here we assume that the socket is client-side, and not
        # connected at the time of the call.  We connect it, then wrap it.
        if self._sslobj:
            raise ValueError("attempt to connect already-connected sslsocket!")
        socket.connect(self, addr)
        self._sslobj = _ssl.sslwrap(self._sock, False, self.keyfile, self.certfile,
                                    self.cert_reqs, self.ssl_version,
                                    self.ca_certs)

    def accept(self):

        """Accepts a new connection from a remote client, and returns
        a tuple containing that new connection wrapped with a server-side
        SSL channel, and the address of the remote client."""

        newsock, addr = socket.accept(self)
        return (sslsocket(newsock, True, self.keyfile, self.certfile,
                         self.cert_reqs, self.ssl_version,
                         self.ca_certs), addr)


# some utility functions

def cert_time_to_seconds(cert_time):

    """Takes a date-time string in standard ASN1_print form
    ("MON DAY 24HOUR:MINUTE:SEC YEAR TIMEZONE") and return
    a Python time value in seconds past the epoch."""

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

# a replacement for the old socket.ssl function

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

    """A replacement for the old socket.ssl function.  Designed
    for compability with Python 2.5 and earlier.  Will disappear in
    Python 3.0."""

    return _ssl.sslwrap(sock._sock, 0, keyfile, certfile, CERT_NONE,
                        PROTOCOL_SSLv23, None)