##   tls_nb.py
##       based on transports_nb.py
##
##   Copyright (C) 2003-2004 Alexey "Snake" Nezhdanov
##       modified by Dimitur Kirov <dkirov@gmail.com>
##       modified by Tomas Karasek <tom.to.the.k@gmail.com>
##
##   This program is free software; you can redistribute it and/or modify
##   it under the terms of the GNU General Public License as published by
##   the Free Software Foundation; either version 2, or (at your option)
##   any later version.
##
##   This program is distributed in the hope that it will be useful,
##   but WITHOUT ANY WARRANTY; without even the implied warranty of
##   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
##   GNU General Public License for more details.

import socket
from plugin import PlugIn

import sys
import os
import time

import traceback

import logging
log = logging.getLogger('gajim.c.x.tls_nb')

USE_PYOPENSSL = False

PYOPENSSL = 'PYOPENSSL'
PYSTDLIB  = 'PYSTDLIB'

try:
	#raise ImportError("Manually disabled PyOpenSSL")
	import OpenSSL.SSL
	import OpenSSL.crypto
	USE_PYOPENSSL = True
	log.info("PyOpenSSL loaded")
except ImportError:
	log.debug("Import of PyOpenSSL failed:", exc_info=True)

	# FIXME: Remove these prints before release, replace with a warning dialog.
	print >> sys.stderr, "=" * 79
	print >> sys.stderr, "PyOpenSSL not found, falling back to Python builtin SSL objects (insecure)."
	print >> sys.stderr, "=" * 79

def gattr(obj, attr, default=None):
	try:
		return getattr(obj, attr)
	except AttributeError:
		return default


class SSLWrapper:
	"""
	Abstract SSLWrapper base class
	"""

	class Error(IOError):
		"""
		Generic SSL Error Wrapper
		"""

		def __init__(self, sock=None, exc=None, errno=None, strerror=None,
				peer=None):
			self.parent = IOError

			errno = errno or gattr(exc, 'errno') or exc[0]
			strerror = strerror or gattr(exc, 'strerror') or gattr(exc, 'args')
			if not isinstance(strerror, basestring):
				strerror = repr(strerror)

			self.sock = sock
			self.exc = exc
			self.peer = peer
			self.exc_name = None
			self.exc_args = None
			self.exc_str = None
			self.exc_repr = None

			if self.exc is not None:
				self.exc_name = str(self.exc.__class__)
				self.exc_args = gattr(self.exc, 'args')
				self.exc_str = str(self.exc)
				self.exc_repr = repr(self.exc)
				if not errno:
					try:
						if isinstance(exc, OpenSSL.SSL.SysCallError):
							if self.exc_args[0] > 0:
								errno = self.exc_args[0]
							strerror = self.exc_args[1]
					except: pass

			self.parent.__init__(self, errno, strerror)

			if self.peer is None and sock is not None:
				try:
					ppeer = self.sock.getpeername()
					if len(ppeer) == 2 and isinstance(ppeer[0], basestring) \
					and isinstance(ppeer[1], int):
						self.peer = ppeer
				except:
					pass

		def __str__(self):
			s = str(self.__class__)
			if self.peer:
				s += " for %s:%d" % self.peer
			if self.errno is not None:
				s += ": [Errno: %d]" % self.errno
			if self.strerror:
				s += " (%s)" % self.strerror
			if self.exc_name:
				s += ", Caused by %s" % self.exc_name
				if self.exc_str:
					if self.strerror:
						s += "(%s)" % self.exc_str
					else: s += "(%s)" % str(self.exc_args)
			return s

	def __init__(self, sslobj, sock=None):
		self.sslobj = sslobj
		self.sock = sock
		log.debug("%s.__init__ called with %s", self.__class__, sslobj)

	def recv(self, data, flags=None):
		"""
		Receive wrapper for SSL object

		We can return None out of this function to signal that no data is
		available right now. Better than an exception, which differs
		depending on which SSL lib we're using. Unfortunately returning ''
		can indicate that the socket has been closed, so to be sure, we avoid
		this by returning None.
		"""
		raise NotImplementedError

	def send(self, data, flags=None, now=False):
		"""
		Send wrapper for SSL object
		"""
		raise NotImplementedError


class PyOpenSSLWrapper(SSLWrapper):
	"""
	Wrapper class for PyOpenSSL's recv() and send() methods
	"""

	def __init__(self, *args):
		self.parent = SSLWrapper
		self.parent.__init__(self, *args)

	def is_numtoolarge(self, e):
		''' Magic methods don't need documentation '''
		t = ('asn1 encoding routines', 'a2d_ASN1_OBJECT', 'first num too large')
		return (isinstance(e.args, (list, tuple)) and len(e.args) == 1 and
			isinstance(e.args[0], (list, tuple)) and len(e.args[0]) == 2 and
			e.args[0][0] == e.args[0][1] == t)

	def recv(self, bufsize, flags=None):
		retval = None
		try:
			if flags is None:
				retval = self.sslobj.recv(bufsize)
			else:
				retval = self.sslobj.recv(bufsize, flags)
		except (OpenSSL.SSL.WantReadError, OpenSSL.SSL.WantWriteError), e:
			log.debug("Recv: Want-error: " + repr(e))
		except OpenSSL.SSL.SysCallError, e:
			log.debug("Recv: Got OpenSSL.SSL.SysCallError: " + repr(e),
				exc_info=True)
			raise SSLWrapper.Error(self.sock or self.sslobj, e)
		except OpenSSL.SSL.ZeroReturnError, e:
			# end-of-connection raises ZeroReturnError instead of having the
			# connection's .recv() method return a zero-sized result.
			raise SSLWrapper.Error(self.sock or self.sslobj, e, -1)
		except OpenSSL.SSL.Error, e:
			if self.is_numtoolarge(e):
				# warn, but ignore this exception
				log.warning("Recv: OpenSSL: asn1enc: first num too large (ignored)")
			else:
				log.debug("Recv: Caught OpenSSL.SSL.Error:", exc_info=True)
				raise SSLWrapper.Error(self.sock or self.sslobj, e)
		return retval

	def send(self, data, flags=None, now=False):
		try:
			if flags is None:
				return self.sslobj.send(data)
			else:
				return self.sslobj.send(data, flags)
		except (OpenSSL.SSL.WantReadError, OpenSSL.SSL.WantWriteError), e:
			#log.debug("Send: " + repr(e))
			time.sleep(0.1) # prevent 100% CPU usage
		except OpenSSL.SSL.SysCallError, e:
			log.error("Send: Got OpenSSL.SSL.SysCallError: " + repr(e),
				exc_info=True)
			raise SSLWrapper.Error(self.sock or self.sslobj, e)
		except OpenSSL.SSL.Error, e:
			if self.is_numtoolarge(e):
				# warn, but ignore this exception
				log.warning("Send: OpenSSL: asn1enc: first num too large (ignored)")
			else:
				log.error("Send: Caught OpenSSL.SSL.Error:", exc_info=True)
				raise SSLWrapper.Error(self.sock or self.sslobj, e)
		return 0


class StdlibSSLWrapper(SSLWrapper):
	"""
	Wrapper class for Python socket.ssl read() and write() methods
	"""

	def __init__(self, *args):
		self.parent = SSLWrapper
		self.parent.__init__(self, *args)

	def recv(self, bufsize, flags=None):
		# we simply ignore flags since ssl object doesn't support it
		try:
			return self.sslobj.read(bufsize)
		except socket.sslerror, e:
			log.debug("Recv: Caught socket.sslerror: " + repr(e), exc_info=True)
			if e.args[0] not in (socket.SSL_ERROR_WANT_READ, socket.SSL_ERROR_WANT_WRITE):
				raise SSLWrapper.Error(self.sock or self.sslobj, e)
		return None

	def send(self, data, flags=None, now=False):
		# we simply ignore flags since ssl object doesn't support it
		try:
			return self.sslobj.write(data)
		except socket.sslerror, e:
			log.debug("Send: Caught socket.sslerror:", exc_info=True)
			if e.args[0] not in (socket.SSL_ERROR_WANT_READ, socket.SSL_ERROR_WANT_WRITE):
				raise SSLWrapper.Error(self.sock or self.sslobj, e)
		return 0


class NonBlockingTLS(PlugIn):
	"""
	TLS connection used to encrypts already estabilished tcp connection

	Can be plugged into NonBlockingTCP and will make use of StdlibSSLWrapper or
	PyOpenSSLWrapper.
	"""

	def __init__(self, cacerts, mycerts):
		"""
		:param cacerts: path to pem file with certificates of known XMPP servers
		:param mycerts: path to pem file with certificates of user trusted servers
		"""
		PlugIn.__init__(self)
		self.cacerts = cacerts
		self.mycerts = mycerts

	# from ssl.h (partial extract)
	ssl_h_bits = {	"SSL_ST_CONNECT": 0x1000, "SSL_ST_ACCEPT": 0x2000,
			"SSL_CB_LOOP": 0x01, "SSL_CB_EXIT": 0x02,
			"SSL_CB_READ": 0x04, "SSL_CB_WRITE": 0x08,
			"SSL_CB_ALERT": 0x4000,
			"SSL_CB_HANDSHAKE_START": 0x10, "SSL_CB_HANDSHAKE_DONE": 0x20}

	def plugin(self, owner):
		"""
		Use to PlugIn TLS into transport and start establishing immediately.
		Returns True if TLS/SSL was established correctly, otherwise False
		"""
		log.info('Starting TLS estabilishing')
		try:
			res = self._startSSL()
		except Exception, e:
			log.error("PlugIn: while trying _startSSL():", exc_info=True)
			return False
		return res

	def _dumpX509(self, cert, stream=sys.stderr):
		print >> stream, "Digest (SHA-1):", cert.digest("sha1")
		print >> stream, "Digest (MD5):", cert.digest("md5")
		print >> stream, "Serial #:", cert.get_serial_number()
		print >> stream, "Version:", cert.get_version()
		print >> stream, "Expired:", ("Yes" if cert.has_expired() else "No")
		print >> stream, "Subject:"
		self._dumpX509Name(cert.get_subject(), stream)
		print >> stream, "Issuer:"
		self._dumpX509Name(cert.get_issuer(), stream)
		self._dumpPKey(cert.get_pubkey(), stream)

	def _dumpX509Name(self, name, stream=sys.stderr):
		print >> stream, "X509Name:", str(name)

	def _dumpPKey(self, pkey, stream=sys.stderr):
		typedict = {OpenSSL.crypto.TYPE_RSA: "RSA",
						OpenSSL.crypto.TYPE_DSA: "DSA"}
		print >> stream, "PKey bits:", pkey.bits()
		print >> stream, "PKey type: %s (%d)" % (typedict.get(pkey.type(),
			"Unknown"), pkey.type())

	def _startSSL(self):
		"""
		Immediatedly switch socket to TLS mode. Used internally
		"""
		log.debug("_startSSL called")

		if USE_PYOPENSSL:
			result = self._startSSL_pyOpenSSL()
		else:
			result = self._startSSL_stdlib()

		if result:
			log.debug('Synchronous handshake completed')
			return True
		else:
			return False

	def _load_cert_file(self, cert_path, cert_store, logg=True):
		if not os.path.isfile(cert_path):
			return
		try:
			f = open(cert_path)
		except IOError, e:
			log.warning('Unable to open certificate file %s: %s' % \
				(cert_path, str(e)))
			return
		lines = f.readlines()
		i = 0
		begin = -1
		for line in lines:
			if 'BEGIN CERTIFICATE' in line:
				begin = i
			elif 'END CERTIFICATE' in line and begin > -1:
				cert = ''.join(lines[begin:i+2])
				try:
					x509cert = OpenSSL.crypto.load_certificate(
						OpenSSL.crypto.FILETYPE_PEM, cert)
					cert_store.add_cert(x509cert)
				except OpenSSL.crypto.Error, exception_obj:
					if logg:
						log.warning('Unable to load a certificate from file %s: %s' %\
							(cert_path, exception_obj.args[0][0][2]))
				except:
					log.warning('Unknown error while loading certificate from file '
						'%s' % cert_path)
				begin = -1
			i += 1

	def _startSSL_pyOpenSSL(self):
		log.debug("_startSSL_pyOpenSSL called")
		tcpsock = self._owner
		# See http://docs.python.org/dev/library/ssl.html
		tcpsock._sslContext = OpenSSL.SSL.Context(OpenSSL.SSL.SSLv23_METHOD)
		tcpsock.ssl_errnum = 0
		tcpsock._sslContext.set_verify(OpenSSL.SSL.VERIFY_PEER,
			self._ssl_verify_callback)
		try:
			tcpsock._sslContext.load_verify_locations(self.cacerts)
		except:
			log.warning('Unable to load SSL certificates from file %s' % \
				os.path.abspath(self.cacerts))
		store = tcpsock._sslContext.get_cert_store()
		self._load_cert_file(self.mycerts, store)
		if os.path.isdir('/etc/ssl/certs'):
			for f in os.listdir('/etc/ssl/certs'):
				# We don't logg because there is a lot a duplicated certs in this
				# folder
				self._load_cert_file(os.path.join('/etc/ssl/certs', f), store,
					logg=False)

		tcpsock._sslObj = OpenSSL.SSL.Connection(tcpsock._sslContext,
			tcpsock._sock)
		tcpsock._sslObj.set_connect_state() # set to client mode
		wrapper = PyOpenSSLWrapper(tcpsock._sslObj)
		tcpsock._recv = wrapper.recv
		tcpsock._send = wrapper.send

		log.debug("Initiating handshake...")
		tcpsock._sslObj.setblocking(True)
		try:
			tcpsock._sslObj.do_handshake()
		except:
			log.error('Error while TLS handshake: ', exc_info=True)
			return False
		tcpsock._sslObj.setblocking(False)
		self._owner.ssl_lib = PYOPENSSL
		return True

	def _startSSL_stdlib(self):
		log.debug("_startSSL_stdlib called")
		tcpsock=self._owner
		try:
			tcpsock._sock.setblocking(True)
			tcpsock._sslObj = socket.ssl(tcpsock._sock, None, None)
			tcpsock._sock.setblocking(False)
			tcpsock._sslIssuer = tcpsock._sslObj.issuer()
			tcpsock._sslServer = tcpsock._sslObj.server()
			wrapper = StdlibSSLWrapper(tcpsock._sslObj, tcpsock._sock)
			tcpsock._recv = wrapper.recv
			tcpsock._send = wrapper.send
		except:
			log.error("Exception caught in _startSSL_stdlib:", exc_info=True)
			return False
		self._owner.ssl_lib = PYSTDLIB
		return True

	def _ssl_verify_callback(self, sslconn, cert, errnum, depth, ok):
		# Exceptions can't propagate up through this callback, so print them here.
		try:
			self._owner.ssl_fingerprint_sha1 = cert.digest('sha1')
			if errnum == 0:
				return True
			self._owner.ssl_errnum = errnum
			self._owner.ssl_cert_pem = OpenSSL.crypto.dump_certificate(
				OpenSSL.crypto.FILETYPE_PEM, cert)
			return True
		except:
			log.error("Exception caught in _ssl_info_callback:", exc_info=True)
			# Make sure something is printed, even if log is disabled.
			traceback.print_exc()

# vim: se ts=3: