# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
"""
Starting point for routing EC2 requests.

"""

import webob
import webob.dec
import webob.exc

from nova import context
from nova import exception
from nova import flags
from nova import log as logging
from nova import utils
from nova import wsgi
from nova.api.ec2 import apirequest
from nova.api.ec2 import ec2utils
from nova.auth import manager


FLAGS = flags.FLAGS
LOG = logging.getLogger("nova.api")
flags.DEFINE_boolean('use_forwarded_for', False,
                     'Treat X-Forwarded-For as the canonical remote address. '
                     'Only enable this if you have a sanitizing proxy.')
flags.DEFINE_integer('lockout_attempts', 5,
                     'Number of failed auths before lockout.')
flags.DEFINE_integer('lockout_minutes', 15,
                     'Number of minutes to lockout if triggered.')
flags.DEFINE_integer('lockout_window', 15,
                     'Number of minutes for lockout window.')


class RequestLogging(wsgi.Middleware):
    """Access-Log akin logging for all EC2 API requests."""

    @webob.dec.wsgify(RequestClass=wsgi.Request)
    def __call__(self, req):
        start = utils.utcnow()
        rv = req.get_response(self.application)
        self.log_request_completion(rv, req, start)
        return rv

    def log_request_completion(self, response, request, start):
        apireq = request.environ.get('ec2.request', None)
        if apireq:
            controller = apireq.controller
            action = apireq.action
        else:
            controller = None
            action = None
        ctxt = request.environ.get('ec2.context', None)
        delta = utils.utcnow() - start
        seconds = delta.seconds
        microseconds = delta.microseconds
        LOG.info(
            "%s.%ss %s %s %s %s:%s %s [%s] %s %s",
            seconds,
            microseconds,
            request.remote_addr,
            request.method,
            "%s%s" % (request.script_name, request.path_info),
            controller,
            action,
            response.status_int,
            request.user_agent,
            request.content_type,
            response.content_type,
            context=ctxt)


class Lockout(wsgi.Middleware):
    """Lockout for x minutes on y failed auths in a z minute period.

    x = lockout_timeout flag
    y = lockout_window flag
    z = lockout_attempts flag

    Uses memcached if lockout_memcached_servers flag is set, otherwise it
    uses a very simple in-proccess cache. Due to the simplicity of
    the implementation, the timeout window is started with the first
    failed request, so it will block if there are x failed logins within
    that period.

    There is a possible race condition where simultaneous requests could
    sneak in before the lockout hits, but this is extremely rare and would
    only result in a couple of extra failed attempts."""

    def __init__(self, application):
        """middleware can use fake for testing."""
        if FLAGS.memcached_servers:
            import memcache
        else:
            from nova import fakememcache as memcache
        self.mc = memcache.Client(FLAGS.memcached_servers,
                                  debug=0)
        super(Lockout, self).__init__(application)

    @webob.dec.wsgify(RequestClass=wsgi.Request)
    def __call__(self, req):
        access_key = str(req.params['AWSAccessKeyId'])
        failures_key = "authfailures-%s" % access_key
        failures = int(self.mc.get(failures_key) or 0)
        if failures >= FLAGS.lockout_attempts:
            detail = _("Too many failed authentications.")
            raise webob.exc.HTTPForbidden(detail=detail)
        res = req.get_response(self.application)
        if res.status_int == 403:
            failures = self.mc.incr(failures_key)
            if failures is None:
                # NOTE(vish): To use incr, failures has to be a string.
                self.mc.set(failures_key, '1', time=FLAGS.lockout_window * 60)
            elif failures >= FLAGS.lockout_attempts:
                lock_mins = FLAGS.lockout_minutes
                msg = _('Access key %(access_key)s has had %(failures)d'
                        ' failed authentications and will be locked out'
                        ' for %(lock_mins)d minutes.') % locals()
                LOG.warn(msg)
                self.mc.set(failures_key, str(failures),
                            time=FLAGS.lockout_minutes * 60)
        return res


class Authenticate(wsgi.Middleware):

    """Authenticate an EC2 request and add 'ec2.context' to WSGI environ."""

    @webob.dec.wsgify(RequestClass=wsgi.Request)
    def __call__(self, req):
        # Read request signature and access id.
        try:
            signature = req.params['Signature']
            access = req.params['AWSAccessKeyId']
        except:
            raise webob.exc.HTTPBadRequest()

        # Make a copy of args for authentication and signature verification.
        auth_params = dict(req.params)
        # Not part of authentication args
        auth_params.pop('Signature')

        # Authenticate the request.
        try:
            (user, project) = manager.AuthManager().authenticate(
                    access,
                    signature,
                    auth_params,
                    req.method,
                    req.host,
                    req.path)
        # Be explicit for what exceptions are 403, the rest bubble as 500
        except (exception.NotFound, exception.NotAuthorized) as ex:
            LOG.audit(_("Authentication Failure: %s"), unicode(ex))
            raise webob.exc.HTTPForbidden()