# Authors:
#   Jason Gerard DeRose <jderose@redhat.com>
#   Rob Crittenden <rcritten@redhat.com>
#
# Copyright (C) 2008  Red Hat
# see file 'COPYING' for use and warranty information
#
# 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 3 of the License, 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.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

"""
RPC client and shared RPC client/server functionality.

This module adds some additional functionality on top of the ``xmlrpclib``
module in the Python standard library.  For documentation on the
``xmlrpclib`` module, see:

    http://docs.python.org/library/xmlrpclib.html

Also see the `ipaserver.rpcserver` module.
"""

from types import NoneType
from decimal import Decimal
import threading
import sys
import os
import errno
import locale
import datetime
from xmlrpclib import (Binary, Fault, dumps, loads, ServerProxy, Transport,
        ProtocolError, MININT, MAXINT)
import kerberos
from dns import resolver, rdatatype
from dns.exception import DNSException

from ipalib.backend import Connectible
from ipalib.errors import public_errors, PublicError, UnknownError, NetworkError, KerberosError, XMLRPCMarshallError
from ipalib import errors
from ipalib.request import context, Connection
from ipalib.util import get_current_principal
from ipapython.ipa_log_manager import root_logger
from ipapython import ipautil
from ipapython import kernel_keyring
from ipapython.cookie import Cookie
from ipalib.text import _

import httplib
import socket
from ipapython.nsslib import NSSHTTPS, NSSConnection
from nss.error import NSPRError
from urllib2 import urlparse
from ipalib.krb_utils import KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN, KRB5KRB_AP_ERR_TKT_EXPIRED, \
                             KRB5_FCC_PERM, KRB5_FCC_NOFILE, KRB5_CC_FORMAT, KRB5_REALM_CANT_RESOLVE
from ipapython.dn import DN

COOKIE_NAME = 'ipa_session'
KEYRING_COOKIE_NAME = '%s_cookie:%%s' % COOKIE_NAME


def client_session_keyring_keyname(principal):
    '''
    Return the key name used for storing the client session data for
    the given principal.
    '''

    return KEYRING_COOKIE_NAME % principal

def update_persistent_client_session_data(principal, data):
    '''
    Given a principal create or update the session data for that
    principal in the persistent secure storage.

    Raises ValueError if unable to perform the action for any reason.
    '''

    try:
        keyname = client_session_keyring_keyname(principal)
    except Exception, e:
        raise ValueError(str(e))

    # kernel_keyring only raises ValueError (why??)
    kernel_keyring.update_key(keyname, data)

def read_persistent_client_session_data(principal):
    '''
    Given a principal return the stored session data for that
    principal from the persistent secure storage.

    Raises ValueError if unable to perform the action for any reason.
    '''

    try:
        keyname = client_session_keyring_keyname(principal)
    except Exception, e:
        raise ValueError(str(e))

    # kernel_keyring only raises ValueError (why??)
    return kernel_keyring.read_key(keyname)

def delete_persistent_client_session_data(principal):
    '''
    Given a principal remove the session data for that
    principal from the persistent secure storage.

    Raises ValueError if unable to perform the action for any reason.
    '''

    try:
        keyname = client_session_keyring_keyname(principal)
    except Exception, e:
        raise ValueError(str(e))

    # kernel_keyring only raises ValueError (why??)
    kernel_keyring.del_key(keyname)

def xml_wrap(value):
    """
    Wrap all ``str`` in ``xmlrpclib.Binary``.

    Because ``xmlrpclib.dumps()`` will itself convert all ``unicode`` instances
    into UTF-8 encoded ``str`` instances, we don't do it here.

    So in total, when encoding data for an XML-RPC packet, the following
    transformations occur:

        * All ``str`` instances are treated as binary data and are wrapped in
          an ``xmlrpclib.Binary()`` instance.

        * Only ``unicode`` instances are treated as character data. They get
          converted to UTF-8 encoded ``str`` instances (although as mentioned,
          not by this function).

    Also see `xml_unwrap()`.

    :param value: The simple scalar or simple compound value to wrap.
    """
    if type(value) in (list, tuple):
        return tuple(xml_wrap(v) for v in value)
    if isinstance(value, dict):
        return dict(
            (k, xml_wrap(v)) for (k, v) in value.iteritems()
        )
    if type(value) is str:
        return Binary(value)
    if type(value) is Decimal:
        # transfer Decimal as a string
        return unicode(value)
    if isinstance(value, (int, long)) and (value < MININT or value > MAXINT):
        return unicode(value)
    if isinstance(value, DN):
        return str(value)
    assert type(value) in (unicode, int, long, float, bool, NoneType)
    return value


def xml_unwrap(value, encoding='UTF-8'):
    """
    Unwrap all ``xmlrpc.Binary``, decode all ``str`` into ``unicode``.

    When decoding data from an XML-RPC packet, the following transformations
    occur:

        * The binary payloads of all ``xmlrpclib.Binary`` instances are
          returned as ``str`` instances.

        * All ``str`` instances are treated as UTF-8 encoded Unicode strings.
          They are decoded and the resulting ``unicode`` instance is returned.

    Also see `xml_wrap()`.

    :param value: The value to unwrap.
    :param encoding: The Unicode encoding to use (defaults to ``'UTF-8'``).
    """
    if type(value) in (list, tuple):
        return tuple(xml_unwrap(v, encoding) for v in value)
    if type(value) is dict:
        return dict(
            (k, xml_unwrap(v, encoding)) for (k, v) in value.iteritems()
        )
    if type(value) is str:
        return value.decode(encoding)
    if isinstance(value, Binary):
        assert type(value.data) is str
        return value.data
    assert type(value) in (unicode, int, float, bool, NoneType)
    return value


def xml_dumps(params, methodname=None, methodresponse=False, encoding='UTF-8'):
    """
    Encode an XML-RPC data packet, transparently wraping ``params``.

    This function will wrap ``params`` using `xml_wrap()` and will
    then encode the XML-RPC data packet using ``xmlrpclib.dumps()`` (from the
    Python standard library).

    For documentation on the ``xmlrpclib.dumps()`` function, see:

        http://docs.python.org/library/xmlrpclib.html#convenience-functions

    Also see `xml_loads()`.

    :param params: A ``tuple`` or an ``xmlrpclib.Fault`` instance.
    :param methodname: The name of the method to call if this is a request.
    :param methodresponse: Set this to ``True`` if this is a response.
    :param encoding: The Unicode encoding to use (defaults to ``'UTF-8'``).
    """
    if type(params) is tuple:
        params = xml_wrap(params)
    else:
        assert isinstance(params, Fault)
    return dumps(params,
        methodname=methodname,
        methodresponse=methodresponse,
        encoding=encoding,
        allow_none=True,
    )


def decode_fault(e, encoding='UTF-8'):
    assert isinstance(e, Fault)
    if type(e.faultString) is str:
        return Fault(e.faultCode, e.faultString.decode(encoding))
    return e


def xml_loads(data, encoding='UTF-8'):
    """
    Decode the XML-RPC packet in ``data``, transparently unwrapping its params.

    This function will decode the XML-RPC packet in ``data`` using
    ``xmlrpclib.loads()`` (from the Python standard library).  If ``data``
    contains a fault, ``xmlrpclib.loads()`` will itself raise an
    ``xmlrpclib.Fault`` exception.

    Assuming an exception is not raised, this function will then unwrap the
    params in ``data`` using `xml_unwrap()`.  Finally, a
    ``(params, methodname)`` tuple is returned containing the unwrapped params
    and the name of the method being called.  If the packet contains no method
    name, ``methodname`` will be ``None``.

    For documentation on the ``xmlrpclib.loads()`` function, see:

        http://docs.python.org/library/xmlrpclib.html#convenience-functions

    Also see `xml_dumps()`.

    :param data: The XML-RPC packet to decode.
    """
    try:
        (params, method) = loads(data)
        return (xml_unwrap(params), method)
    except Fault, e:
        raise decode_fault(e)


class LanguageAwareTransport(Transport):
    """Transport sending Accept-Language header"""
    def get_host_info(self, host):
        (host, extra_headers, x509) = Transport.get_host_info(self, host)

        try:
            lang = locale.setlocale(locale.LC_ALL, '').split('.')[0].lower()
        except locale.Error:
            # fallback to default locale
            lang = 'en_us'

        if not isinstance(extra_headers, list):
            extra_headers = []

        extra_headers.append(
            ('Accept-Language', lang.replace('_', '-'))
        )
        extra_headers.append(
            ('Referer', 'https://%s/ipa/xml' % str(host))
        )

        return (host, extra_headers, x509)

class SSLTransport(LanguageAwareTransport):
    """Handles an HTTPS transaction to an XML-RPC server."""

    def __nss_initialized(self, dbdir):
        """
        If there is another connections open it may have already
        initialized NSS. This is likely to lead to an NSS shutdown
        failure.  One way to mitigate this is to tell NSS to not
        initialize if it has already been done in another open connection.

        Returns True if another connection is using the same db.
        """
        for value in context.__dict__.values():
            if not isinstance(value, Connection):
                continue
            if not isinstance(value.conn._ServerProxy__transport, SSLTransport):
                continue
            if hasattr(value.conn._ServerProxy__transport, 'dbdir') and \
              value.conn._ServerProxy__transport.dbdir == dbdir:
                return True
        return False

    def make_connection(self, host):
        host, self._extra_headers, x509 = self.get_host_info(host)
        # Python 2.7 changed the internal class used in xmlrpclib from
        # HTTP to HTTPConnection. We need to use the proper subclass

        # If we an existing connection exists using the same NSS database
        # there is no need to re-initialize. Pass thsi into the NSS
        # connection creator.
        if sys.version_info >= (2, 7):
            if self._connection and host == self._connection[0]:
                return self._connection[1]

        dbdir = '/etc/pki/nssdb'
        no_init = self.__nss_initialized(dbdir)
        if sys.version_info < (2, 7):
            conn = NSSHTTPS(host, 443, dbdir=dbdir, no_init=no_init)
        else:
            conn = NSSConnection(host, 443, dbdir=dbdir, no_init=no_init)
        self.dbdir=dbdir

        conn.connect()
        if sys.version_info < (2, 7):
            return conn
        else:
            self._connection = host, conn
            return self._connection[1]


class KerbTransport(SSLTransport):
    """
    Handles Kerberos Negotiation authentication to an XML-RPC server.
    """
    flags = kerberos.GSS_C_MUTUAL_FLAG | kerberos.GSS_C_SEQUENCE_FLAG

    def _handle_exception(self, e, service=None):
        (major, minor) = ipautil.get_gsserror(e)
        if minor[1] == KRB5KDC_ERR_S_PRINCIPAL_UNKNOWN:
            raise errors.ServiceError(service=service)
        elif minor[1] == KRB5_FCC_NOFILE:
            raise errors.NoCCacheError()
        elif minor[1] == KRB5KRB_AP_ERR_TKT_EXPIRED:
            raise errors.TicketExpired()
        elif minor[1] == KRB5_FCC_PERM:
            raise errors.BadCCachePerms()
        elif minor[1] == KRB5_CC_FORMAT:
            raise errors.BadCCacheFormat()
        elif minor[1] == KRB5_REALM_CANT_RESOLVE:
            raise errors.CannotResolveKDC()
        else:
            raise errors.KerberosError(major=major, minor=minor)

    def get_host_info(self, host):
        """
        Two things can happen here. If we have a session we will add
        a cookie for that. If not we will set an Authorization header.
        """
        (host, extra_headers, x509) = SSLTransport.get_host_info(self, host)

        if not isinstance(extra_headers, list):
            extra_headers = []

        session_cookie = getattr(context, 'session_cookie', None)
        if session_cookie:
            extra_headers.append(('Cookie', session_cookie))
            return (host, extra_headers, x509)

        # Set the remote host principal
        service = "HTTP@" + host.split(':')[0]

        try:
            (rc, vc) = kerberos.authGSSClientInit(service, self.flags)
        except kerberos.GSSError, e:
            self._handle_exception(e)

        try:
            kerberos.authGSSClientStep(vc, "")
        except kerberos.GSSError, e:
            self._handle_exception(e, service=service)

        for (h, v) in extra_headers:
            if h == 'Authorization':
                extra_headers.remove((h, v))
                break

        extra_headers.append(
            ('Authorization', 'negotiate %s' % kerberos.authGSSClientResponse(vc))
        )

        return (host, extra_headers, x509)

    def single_request(self, host, handler, request_body, verbose=0):
        try:
            return SSLTransport.single_request(self, host, handler, request_body, verbose)
        finally:
            self.close()

    def store_session_cookie(self, cookie_header):
        '''
        Given the contents of a Set-Cookie header scan the header and
        extract each cookie contained within until the session cookie
        is located. Examine the session cookie if the domain and path
        are specified, if not update the cookie with those values from
        the request URL. Then write the session cookie into the key
        store for the principal. If the cookie header is None or the
        session cookie is not present in the header no action is
        taken.

        Context Dependencies:

        The per thread context is expected to contain:
            principal
                The current pricipal the HTTP request was issued for.
            request_url
                The URL of the HTTP request.

        '''

        if cookie_header is None:
            return

        principal = getattr(context, 'principal', None)
        request_url = getattr(context, 'request_url', None)
        root_logger.debug("received Set-Cookie '%s'", cookie_header)

        # Search for the session cookie
        try:
            session_cookie = Cookie.get_named_cookie_from_string(cookie_header,
                                                                 COOKIE_NAME, request_url)
        except Exception, e:
            root_logger.error("unable to parse cookie header '%s': %s", cookie_header, e)
            return

        if session_cookie is None:
            return

        cookie_string = str(session_cookie)
        root_logger.debug("storing cookie '%s' for principal %s", cookie_string, principal)
        try:
            update_persistent_client_session_data(principal, cookie_string)
        except Exception, e:
            # Not fatal, we just can't use the session cookie we were sent.
            pass

    def parse_response(self, response):
        self.store_session_cookie(response.getheader('Set-Cookie'))
        return SSLTransport.parse_response(self, response)


class DelegatedKerbTransport(KerbTransport):
    """
    Handles Kerberos Negotiation authentication and TGT delegation to an
    XML-RPC server.
    """
    flags = kerberos.GSS_C_DELEG_FLAG |  kerberos.GSS_C_MUTUAL_FLAG | \
            kerberos.GSS_C_SEQUENCE_FLAG

class xmlclient(Connectible):
    """
    Forwarding backend plugin for XML-RPC client.

    Also see the `ipaserver.rpcserver.xmlserver` plugin.
    """

    def __init__(self):
        super(xmlclient, self).__init__()
        self.__errors = dict((e.errno, e) for e in public_errors)

    def get_url_list(self, xmlrpc_uri):
        """
        Create a list of urls consisting of the available IPA servers.
        """
        # the configured URL defines what we use for the discovered servers
        (scheme, netloc, path, params, query, fragment) = urlparse.urlparse(xmlrpc_uri)
        servers = []
        name = '_ldap._tcp.%s.' % self.env.domain

        try:
            answers = resolver.query(name, rdatatype.SRV)
        except DNSException, e:
            answers = []

        for answer in answers:
            server = str(answer.target).rstrip(".")
            servers.append('https://%s%s' % (ipautil.format_netloc(server), path))

        servers = list(set(servers))
        # the list/set conversion won't preserve order so stick in the
        # local config file version here.
        cfg_server = xmlrpc_uri
        if cfg_server in servers:
            # make sure the configured master server is there just once and
            # it is the first one
            servers.remove(cfg_server)
            servers.insert(0, cfg_server)
        else:
            servers.insert(0, cfg_server)

        return servers

    def get_session_cookie_from_persistent_storage(self, principal):
        '''
        Retrieves the session cookie for the given principal from the
        persistent secure storage. Returns None if not found or unable
        to retrieve the session cookie for any reason, otherwise
        returns a Cookie object containing the session cookie.
        '''

        # Get the session data, it should contain a cookie string
        # (possibly with more than one cookie).
        try:
            cookie_string = read_persistent_client_session_data(principal)
        except Exception, e:
            return None

        # Search for the session cookie within the cookie string
        try:
            session_cookie = Cookie.get_named_cookie_from_string(cookie_string, COOKIE_NAME)
        except Exception, e:
            return None

        return session_cookie

    def apply_session_cookie(self, url):
        '''
        Attempt to load a session cookie for the current principal
        from the persistent secure storage. If the cookie is
        successfully loaded adjust the input url's to point to the
        session path and insert the session cookie into the per thread
        context for later insertion into the HTTP request. If the
        cookie is not successfully loaded then the original url is
        returned and the per thread context is not modified.

        Context Dependencies:

        The per thread context is expected to contain:
            principal
                The current pricipal the HTTP request was issued for.

        The per thread context will be updated with:
            session_cookie
                A cookie string to be inserted into the Cookie header
                of the HTPP request.

        '''

        original_url = url
        principal = getattr(context, 'principal', None)

        session_cookie = self.get_session_cookie_from_persistent_storage(principal)
        if session_cookie is None:
            self.log.debug("failed to find session_cookie in persistent storage for principal '%s'",
                           principal)
            return original_url
        else:
            self.debug("found session_cookie in persistent storage for principal '%s', cookie: '%s'",
                       principal, session_cookie)

        # Decide if we should send the cookie to the server
        try:
            session_cookie.http_return_ok(original_url)
        except Cookie.Expired, e:
            self.debug("deleting session data for principal '%s': %s", principal, e)
            try:
                delete_persistent_client_session_data(principal)
            except Exception, e:
                pass
            return original_url
        except Cookie.URLMismatch, e:
            self.debug("not sending session cookie, URL mismatch: %s", e)
            return original_url
        except Exception, e:
            self.error("not sending session cookie, unknown error: %s", e)
            return original_url

        # O.K. session_cookie is valid to be returned, stash it away where it will will
        # get included in a HTTP Cookie headed sent to the server.
        self.log.debug("setting session_cookie into context '%s'", session_cookie.http_cookie())
        setattr(context, 'session_cookie', session_cookie.http_cookie())

        # Form the session URL by substituting the session path into the original URL
        scheme, netloc, path, params, query, fragment = urlparse.urlparse(original_url)
        path = '/ipa/session/xml'
        session_url = urlparse.urlunparse((scheme, netloc, path, params, query, fragment))

        return session_url

    def create_connection(self, ccache=None, verbose=False, fallback=True,
                          delegate=False):
        try:
            xmlrpc_uri = self.env.xmlrpc_uri
            principal = get_current_principal()
            setattr(context, 'principal', principal)
            # We have a session cookie, try using the session URI to see if it
            # is still valid
            if not delegate:
                xmlrpc_uri = self.apply_session_cookie(xmlrpc_uri)
        except ValueError:
            # No session key, do full Kerberos auth
            pass
        urls = self.get_url_list(xmlrpc_uri)
        serverproxy = None
        for url in urls:
            kw = dict(allow_none=True, encoding='UTF-8')
            kw['verbose'] = verbose
            if url.startswith('https://'):
                if delegate:
                    kw['transport'] = DelegatedKerbTransport()
                else:
                    kw['transport'] = KerbTransport()
            else:
                kw['transport'] = LanguageAwareTransport()
            self.log.debug('trying %s' % url)
            setattr(context, 'request_url', url)
            serverproxy = ServerProxy(url, **kw)
            if len(urls) == 1:
                # if we have only 1 server and then let the
                # main requester handle any errors. This also means it
                # must handle a 401 but we save a ping.
                return serverproxy
            try:
                command = getattr(serverproxy, 'ping')
                try:
                    response = command()
                except Fault, e:
                    e = decode_fault(e)
                    if e.faultCode in self.__errors:
                        error = self.__errors[e.faultCode]
                        raise error(message=e.faultString)
                    else:
                        raise UnknownError(
                            code=e.faultCode,
                            error=e.faultString,
                            server=url,
                        )
                # We don't care about the response, just that we got one
                break
            except KerberosError, krberr:
                # kerberos error on one server is likely on all
                raise errors.KerberosError(major=str(krberr), minor='')
            except ProtocolError, e:
                if hasattr(context, 'session_cookie') and e.errcode == 401:
                    # Unauthorized. Remove the session and try again.
                    delattr(context, 'session_cookie')
                    try:
                        delete_persistent_client_session_data(principal)
                    except Exception, e:
                        # This shouldn't happen if we have a session but it isn't fatal.
                        pass
                    return self.create_connection(ccache, verbose, fallback, delegate)
                if not fallback:
                    raise
                serverproxy = None
            except Exception, e:
                if not fallback:
                    raise
                else:
                    self.log.info('Connection to %s failed with %s', url, e)
                serverproxy = None

        if serverproxy is None:
            raise NetworkError(uri=_('any of the configured servers'),
                error=', '.join(urls))
        return serverproxy

    def destroy_connection(self):
        if sys.version_info >= (2, 7):
            conn = getattr(context, self.id, None)
            if conn is not None:
                conn = conn.conn._ServerProxy__transport
                conn.close()

    def forward(self, name, *args, **kw):
        """
        Forward call to command named ``name`` over XML-RPC.

        This method will encode and forward an XML-RPC request, and will then
        decode and return the corresponding XML-RPC response.

        :param command: The name of the command being forwarded.
        :param args: Positional arguments to pass to remote command.
        :param kw: Keyword arguments to pass to remote command.
        """
        if name not in self.Command:
            raise ValueError(
                '%s.forward(): %r not in api.Command' % (self.name, name)
            )
        server = getattr(context, 'request_url', None)
        self.debug("Forwarding '%s' to server '%s'", name, server)
        command = getattr(self.conn, name)
        params = [args, kw]
        try:
            response = command(*xml_wrap(params))
            return xml_unwrap(response)
        except Fault, e:
            e = decode_fault(e)
            self.debug('Caught fault %d from server %s: %s', e.faultCode,
                server, e.faultString)
            if e.faultCode in self.__errors:
                error = self.__errors[e.faultCode]
                raise error(message=e.faultString)
            raise UnknownError(
                code=e.faultCode,
                error=e.faultString,
                server=server,
            )
        except NSPRError, e:
            raise NetworkError(uri=server, error=str(e))
        except ProtocolError, e:
            # By catching a 401 here we can detect the case where we have
            # a single IPA server and the session is invalid. Otherwise
            # we always have to do a ping().
            session_cookie = getattr(context, 'session_cookie', None)
            if session_cookie and e.errcode == 401:
                # Unauthorized. Remove the session and try again.
                delattr(context, 'session_cookie')
                try:
                    principal = getattr(context, 'principal', None)
                    delete_persistent_client_session_data(principal)
                except Exception, e:
                    # This shouldn't happen if we have a session but it isn't fatal.
                    pass

                # Create a new serverproxy with the non-session URI. If there
                # is an existing connection we need to save the NSS dbdir so
                # we can skip an unnecessary NSS_Initialize() and avoid
                # NSS_Shutdown issues.
                serverproxy = self.create_connection(os.environ.get('KRB5CCNAME'), self.env.verbose, self.env.fallback, self.env.delegate)

                dbdir = None
                current_conn = getattr(context, self.id, None)
                if current_conn is not None:
                    dbdir = getattr(current_conn.conn._ServerProxy__transport, 'dbdir', None)
                    if dbdir is not None:
                        self.debug('Using dbdir %s' % dbdir)
                setattr(context, self.id, Connection(serverproxy, self.disconnect))
                if dbdir is not None:
                    current_conn = getattr(context, self.id, None)
                    current_conn.conn._ServerProxy__transport.dbdir = dbdir
                return self.forward(name, *args, **kw)
            raise NetworkError(uri=server, error=e.errmsg)
        except socket.error, e:
            raise NetworkError(uri=server, error=str(e))
        except (OverflowError, TypeError), e:
            raise XMLRPCMarshallError(error=str(e))
