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# -*- test-case-name: nevow.test.test_guard -*-
# Copyright (c) 2004-2008 Divmod.
# See LICENSE for details.
"""
Resource protection for Nevow. If you wish to use twisted.cred to protect your
Nevow application, you are probably most interested in
L{SessionWrapper}.
"""
__metaclass__ = type
import random
import time
import md5
import StringIO
from zope.interface import implements
# Twisted Imports
from twisted.python import log, components
from twisted.internet import defer
from twisted.cred.error import UnauthorizedLogin
from twisted.cred.credentials import UsernamePassword, Anonymous
try:
from twisted.web import http
except ImportError:
from twisted.protocols import http
# Nevow imports
from nevow import inevow, url, stan
def _sessionCookie():
return md5.new("%s_%s" % (str(random.random()) , str(time.time()))).hexdigest()
class GuardSession(components.Componentized):
"""A user's session with a system.
This utility class contains no functionality, but is used to
represent a session.
"""
implements(inevow.ISession, inevow.IGuardSession)
def __init__(self, guard, uid):
"""Initialize a session with a unique ID for that session.
"""
components.Componentized.__init__(self)
self.guard = guard
self.uid = uid
self.expireCallbacks = []
self.checkExpiredID = None
self.setLifetime(60)
self.portals = {}
self.touch()
# New Guard Interfaces
def getLoggedInRoot(self):
"""Get the most-recently-logged-in avatar.
"""
# XXX TODO: need to actually sort avatars by login order!
if len(self.portals) != 1:
raise RuntimeError("Ambiguous request for current avatar.")
return self.portals.values()[0][0]
def resourceForPortal(self, port):
return self.portals.get(port)
def setDefaultResource(self, rsrc, logout):
"""
Change the root-resource available to the user who has already
authenticated anonymously. This only works in applications that DO NOT
use the multiple-simultaneous-portals feature. If you do not know what
this means, you may safely ignore it.
"""
if len(self.portals) != 1:
raise RuntimeError("Ambiguous request for current avatar.")
self.setResourceForPortal(
rsrc,
self.portals.keys()[0],
logout)
def setResourceForPortal(self, rsrc, port, logout):
"""Change the root-resource available to a user authenticating against a given
portal.
If a user was already logged in to this session from that portal, first
log them out.
@param rsrc: an L{IResource} implementor.
@param port: a cred Portal instance.
@param logout: a 0-arg callable to be invoked upon logout.
"""
self.portalLogout(port)
self.portals[port] = rsrc, logout
return rsrc
def portalLogout(self, port):
"""
If we have previously acccepted a login for this portal, call its
logout method and de-associate that portal from this session, catching
any errors from the logout method.
Otherwise: do nothing.
@param port: a cred Portal.
"""
p = self.portals.get(port)
if p:
log.msg('Logout of portal %r' % port)
r, l = p
try:
l()
except:
log.err()
del self.portals[port]
# timeouts and expiration
def setLifetime(self, lifetime):
"""Set the approximate lifetime of this session, in seconds.
This is highly imprecise, but it allows you to set some general
parameters about when this session will expire. A callback will be
scheduled each 'lifetime' seconds, and if I have not been 'touch()'ed
in half a lifetime, I will be immediately expired.
"""
self.lifetime = lifetime
def notifyOnExpire(self, callback):
"""Call this callback when the session expires or logs out.
"""
self.expireCallbacks.append(callback)
def expire(self):
"""Expire/logout of the session.
"""
log.msg("expired session %s" % str(self.uid))
del self.guard.sessions[self.uid]
# Logout of all portals
for portal in self.portals.keys():
self.portalLogout(portal)
for c in self.expireCallbacks:
try:
c()
except:
log.err()
self.expireCallbacks = []
if self.checkExpiredID:
self.checkExpiredID.cancel()
self.checkExpiredID = None
def touch(self):
self.lastModified = time.time()
def checkExpired(self):
# Import reactor here to avoid installing default at startup
from twisted.internet import reactor
self.checkExpiredID = None
# If I haven't been touched in 15 minutes:
if time.time() - self.lastModified > self.lifetime / 2:
if self.guard.sessions.has_key(self.uid):
self.expire()
else:
log.msg("no session to expire: %s" % str(self.uid))
else:
log.msg("session given the will to live for %s more seconds" % self.lifetime)
self.checkExpiredID = reactor.callLater(self.lifetime,
self.checkExpired)
def __getstate__(self):
d = self.__dict__.copy()
if d.has_key('checkExpiredID'):
del d['checkExpiredID']
return d
def __setstate__(self, d):
self.__dict__.update(d)
self.touch()
self.checkExpired()
def urlToChild(ctx, *ar, **kw):
u = url.URL.fromContext(ctx)
for segment in ar:
u = u.child(stan.xml(segment))
if inevow.IRequest(ctx).method == 'POST':
u = u.clear()
for k,v in kw.items():
u = u.replace(k, v)
return u
SESSION_KEY = '__session_key__'
LOGIN_AVATAR = '__login__'
LOGOUT_AVATAR = '__logout__'
def nomind(*args): return None
class Forbidden(object):
implements(inevow.IResource)
def locateChild(self, ctx, segments):
return self
def renderHTTP(self, ctx):
request = inevow.IRequest(ctx)
request.setResponseCode(http.FORBIDDEN)
return ("<html><head><title>Forbidden</title></head>"
"<body><h1>Forbidden</h1>Request was forbidden.</body></html>")
class SessionWrapper:
"""
SessionWrapper
The following class attributes can be modified on an instance
of the class.
@ivar secureCookies: Whether to use secure (TLS only) cookies or not. If
C{True} (the default), make cookies secure when session is initiated
in a secure (TLS) connection. If C{False}, cookies will not be given
the secure attribute.
@ivar persistentCookies: Whether to use persistent (saved to disk)
cookies or not. If C{True}, make cookies persistent, so they are
valid for the length of the C{sessionLifetime} even if the browser
window is closed. If C{False} (the default), cookies do not get
saved to disk, and thus last only as long as the session does. If
the browser is closed before the session timeout, both the session
and the cookie go away.
"""
implements(inevow.IResource)
sessionLifetime = 3600
sessionFactory = GuardSession
# The interface to cred for when logging into the portal
credInterface = inevow.IResource
useCookies = True
secureCookies = True
persistentCookies = False
def __init__(self, portal, cookieKey=None, mindFactory=None, credInterface=None, useCookies=None):
self.portal = portal
if cookieKey is None:
cookieKey = "woven_session_" + _sessionCookie()
self.cookieKey = cookieKey
self.sessions = {}
if mindFactory is None:
mindFactory = nomind
self.mindFactory = mindFactory
if credInterface is not None:
self.credInterface = credInterface
if useCookies is not None:
self.useCookies = useCookies
# Backwards compatibility; remove asap
self.resource = self
def renderHTTP(self, ctx):
request = inevow.IRequest(ctx)
d = defer.maybeDeferred(self._delegate, ctx, [])
def _cb((resource, segments), ctx):
assert not segments
res = inevow.IResource(resource)
return res.renderHTTP(ctx)
d.addCallback(_cb, ctx)
return d
def locateChild(self, ctx, segments):
request = inevow.IRequest(ctx)
path = segments[0]
if self.useCookies:
cookie = request.getCookie(self.cookieKey)
else:
cookie = ''
if path.startswith(SESSION_KEY):
key = path[len(SESSION_KEY):]
if key not in self.sessions:
return urlToChild(ctx, *segments[1:], **{'__start_session__':1}), ()
self.sessions[key].setLifetime(self.sessionLifetime)
if cookie == key:
# /sessionized-url/${SESSION_KEY}aef9c34aecc3d9148/foo
# ^
# we are this getChild
# with a matching cookie
self.sessions[key].sessionJustStarted = True
return urlToChild(ctx, *segments[1:]), ()
else:
# We attempted to negotiate the session but failed (the user
# probably has cookies disabled): now we're going to return the
# resource we contain. In general the getChild shouldn't stop
# there.
# /sessionized-url/${SESSION_KEY}aef9c34aecc3d9148/foo
# ^ we are this getChild
# without a cookie (or with a mismatched cookie)
return self.checkLogin(ctx, self.sessions[key],
segments[1:],
sessionURL=segments[0])
else:
# /sessionized-url/foo
# ^ we are this getChild
# with or without a session
return self._delegate(ctx, segments)
def _delegate(self, ctx, segments):
"""Identify the session by looking at cookies and HTTP auth headers, use that
session key to identify the wrapped resource, then return a deferred
which fires a 2-tuple of (resource, segments) to the top-level
redirection code code which will delegate IResource's renderHTTP or
locateChild methods to it
"""
request = inevow.IRequest(ctx)
cookie = request.getCookie(self.cookieKey)
# support HTTP auth, no redirections
userpass = request.getUser(), request.getPassword()
httpAuthSessionKey = 'HTTP AUTH: %s:%s' % userpass
for sessionKey in cookie, httpAuthSessionKey:
if sessionKey in self.sessions:
session = self.sessions[sessionKey]
return self.checkLogin(ctx, session, segments)
# without a session
if userpass != ('',''):
# the user is trying to log in with HTTP auth, but they don't have
# a session. So, make them one.
sz = self.sessions[httpAuthSessionKey] = self.sessionFactory(self, httpAuthSessionKey)
# kick off the expiry timer.
sz.checkExpired()
return self.checkLogin(ctx, sz, segments, None, UsernamePassword(*userpass))
# no, really, without a session
## Redirect to the URL with the session key in it, plus the segments of the url
rd = self.createSession(ctx, segments)
return rd, ()
def createSession(self, ctx, segments):
"""
Create a new session for this request, and redirect back to the path
given by segments.
"""
request = inevow.IRequest(ctx)
newCookie = _sessionCookie()
if self.useCookies:
if self.secureCookies and request.isSecure():
secure = True
else:
secure = False
if self.persistentCookies and self.sessionLifetime:
expires = http.datetimeToString(time.time() + self.sessionLifetime)
else:
expires = None
request.addCookie(self.cookieKey, newCookie,
path="/%s" % '/'.join(request.prepath),
secure=secure, expires=expires,
domain=self.cookieDomainForRequest(request))
sz = self.sessions[newCookie] = self.sessionFactory(self, newCookie)
sz.args = request.args
sz.fields = request.fields
sz.method = request.method
sz.received_headers = request.received_headers
sz.checkExpired()
return urlToChild(ctx, SESSION_KEY+newCookie, *segments)
def checkLogin(self, ctx, session, segments, sessionURL=None, httpAuthCredentials=None):
"""
Associate the given request with the given session and:
- log the user in to our portal, if they are accessing a login URL
- log the user out from our portal (calling their logout callback),
if they are logged in and accessing a logout URL
- Move the request parameters saved on the session, if there are
any, onto the request if a session just started or a login
just succeeded.
@return:
- if the user is already logged in: a 2-tuple of requestObject,
C{segments} (i.e. the segments parameter)
- if the user is not logged in and not logging in, call login() to
initialize an anonymous session, and return a 2-tuple of
(rootResource, segments-parameter) from that anonymous session.
This counts as logging in for the purpose of future calls to
checkLogin.
- if the user is accessing a login URL: a 2-tuple of the logged in
resource object root and the remainder of the segments (i.e. the
URL minus __login__) to be passed to that resource.
"""
request = inevow.IRequest(ctx)
session.touch()
request.session = session
root = url.URL.fromContext(request)
if sessionURL is not None:
root = root.child(sessionURL)
request.rememberRootURL(str(root))
spoof = False
if getattr(session, 'sessionJustStarted', False):
del session.sessionJustStarted
spoof = True
if getattr(session, 'justLoggedIn', False):
del session.justLoggedIn
spoof = True
if spoof and hasattr(session, 'args'):
request.args = session.args
request.fields = session.fields
request.content = StringIO.StringIO()
request.content.close()
request.method = session.method
request.received_headers = session.received_headers
del session.args, session.fields, session.method, session.received_headers
if segments and segments[0] in (LOGIN_AVATAR, LOGOUT_AVATAR):
authCommand = segments[0]
else:
authCommand = None
if httpAuthCredentials:
# This is the FIRST TIME we have hit an HTTP auth session with our
# credentials. We are going to perform login.
assert not authCommand, (
"HTTP auth support isn't that robust. "
"Come up with something to do that makes sense here.")
return self.login(request, session, httpAuthCredentials, segments).addErrback(
self.authRequiredError, session
)
if authCommand == LOGIN_AVATAR:
subSegments = segments[1:]
def unmangleURL((res,segs)):
# Tell the session that we just logged in so that it will
# remember form values for us.
session.justLoggedIn = True
# Then, generate a redirect back to where we're supposed to be
# by looking at the root of the site and calculating the path
# down from there using the segments we were passed.
u = url.URL.fromString(request.getRootURL())
for seg in subSegments:
u = u.child(seg)
return u, ()
return self.login(request, session, self.getCredentials(request), subSegments).addCallback(
unmangleURL).addErrback(
self.incorrectLoginError, ctx, subSegments, "Incorrect login."
)
elif authCommand == LOGOUT_AVATAR:
self.explicitLogout(session)
return urlToChild(ctx, *segments[1:]), ()
else:
r = session.resourceForPortal(self.portal)
if r:
## Delegate our getChild to the resource our portal says is the right one.
return r[0], segments
else:
# XXX I don't think that the errback here will work at all,
# because the redirect loop would be infinite. Perhaps this
# should be closer to the HTTP auth path?
return self.login(request, session, Anonymous(), segments).addErrback(
self.incorrectLoginError, ctx, segments, 'Anonymous access not allowed.')
def explicitLogout(self, session):
"""
Hook to be overridden if you care about user-requested logout.
Note: there is no return value from this method; it is purely a way to
provide customized behavior that distinguishes between session-expiry
logout, which is what 99% of code cares about, and explicit user
logout, which you may need to be notified of if (for example) your
application sets other HTTP cookies which refer to server-side state,
and you want to expire that state in a manual logout but not with an
automated logout. (c.f. Quotient's persistent sessions.)
If you want the user to see a customized logout page, just generate a
logout link that looks like::
http://your-site.example.com/__logout__/my/custom/logout/stuff
and the user will see::
http://your-site.example.com/my/custom/logout/stuff
as their first URL after becoming anonymous again.
"""
session.portalLogout(self.portal)
def getCredentials(self, request):
username = request.args.get('username', [''])[0]
password = request.args.get('password', [''])[0]
return UsernamePassword(username, password)
def login(self, request, session, credentials, segments):
"""
- Calls login() on our portal.
- creates a mind from my mindFactory, with the request and credentials
- Associates the mind with the given session.
- Associates the resource returned from my portal's login() with my
portal in the given session.
@return: a Deferred which fires a 2-tuple of the resource returned from
my portal's login() and the passed list of segments upon successful
login.
"""
mind = self.mindFactory(request, credentials)
session.mind = mind
return self.portal.login(credentials, mind, self.credInterface).addCallback(
self._cbLoginSuccess, session, segments
)
def _cbLoginSuccess(self, (iface, res, logout), session, segments):
session.setResourceForPortal(res, self.portal, logout)
return res, segments
def incorrectLoginError(self, error, ctx, segments, loginFailure):
""" Used as an errback upon failed login, returns a 2-tuple of a failure URL
with the query argument 'login-failure' set to the parameter
loginFailure, and an empty list of segments, to redirect to that URL.
The basis for this error URL, i.e. the part before the query string, is
taken either from the 'referer' header from the given request if one
exists, or a computed URL that points at the same page that the user is
currently looking at to attempt login. Any existing query string will
be stripped.
"""
request = inevow.IRequest(ctx)
error.trap(UnauthorizedLogin)
referer = request.getHeader("referer")
if referer is not None:
u = url.URL.fromString(referer)
else:
u = urlToChild(ctx, *segments)
u = u.clear()
u = u.add('login-failure', loginFailure)
return u, ()
def authRequiredError(self, error, session):
session.expire()
error.trap(UnauthorizedLogin)
return Forbidden(), ()
def cookieDomainForRequest(self, request):
"""
Specify the domain restriction on the session cookie.
@param request: The request object in response to which a cookie is
being set.
@return: C{None} or a C{str} giving the domain restriction to set on
the cookie.
"""
return None
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