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diff --git a/src/mailman/workflows/builtin.py b/src/mailman/workflows/builtin.py
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+# Copyright (C) 2015-2017 by the Free Software Foundation, Inc.
+#
+# This file is part of GNU Mailman.
+#
+# GNU Mailman 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.
+#
+# GNU Mailman 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
+# GNU Mailman.  If not, see <http://www.gnu.org/licenses/>.
+
+"""The built in subscription and unsubscription workflows."""
+
+import logging
+
+from email.utils import formataddr
+from mailman.app.membership import delete_member
+from mailman.core.i18n import _
+from mailman.email.message import UserNotification
+from mailman.interfaces.address import IAddress
+from mailman.interfaces.bans import IBanManager
+from mailman.interfaces.mailinglist import SubscriptionPolicy
+from mailman.interfaces.member import (AlreadySubscribedError, MemberRole,
+                                       MembershipIsBannedError,
+                                       NotAMemberError)
+from mailman.interfaces.pending import IPendable, IPendings
+from mailman.interfaces.subscriptions import (
+    SubscriptionConfirmationNeededEvent, SubscriptionPendingError,
+    TokenOwner, UnsubscriptionConfirmationNeededEvent)
+from mailman.interfaces.template import ITemplateLoader
+from mailman.interfaces.user import IUser
+from mailman.interfaces.usermanager import IUserManager
+from mailman.utilities.datetime import now
+from mailman.utilities.string import expand, wrap
+from mailman.workflows.common import (SubscriptionWorkflowCommon,
+                                      WhichSubscriber)
+from public import public
+from zope.component import getUtility
+from zope.event import notify
+from zope.interface import implementer
+
+
+log = logging.getLogger('mailman.subscribe')
+
+
+@implementer(IPendable)
+class PendableSubscription(dict):
+    PEND_TYPE = 'subscription'
+
+
+@implementer(IPendable)
+class PendableUnsubscription(dict):
+    PEND_TYPE = 'unsubscription'
+
+
+@public
+class SubscriptionWorkflow(SubscriptionWorkflowCommon):
+    """Workflow of a subscription request."""
+
+    name = 'subscription-default'
+    description = ''
+
+    initial_state = 'sanity_checks'
+    save_attributes = (
+        'pre_approved',
+        'pre_confirmed',
+        'pre_verified',
+        'address_key',
+        'subscriber_key',
+        'user_key',
+        'token_owner_key',
+        )
+
+    def __init__(self, mlist, subscriber=None, *,
+                 pre_verified=False, pre_confirmed=False, pre_approved=False):
+        super().__init__(mlist, subscriber)
+        self.pre_verified = pre_verified
+        self.pre_confirmed = pre_confirmed
+        self.pre_approved = pre_approved
+
+    def _step_sanity_checks(self):
+        # Ensure that we have both an address and a user, even if the address
+        # is not verified.  We can't set the preferred address until it is
+        # verified.
+        if self.user is None:
+            # The address has no linked user so create one, link it, and set
+            # the user's preferred address.
+            assert self.address is not None, 'No address or user'
+            self.user = getUtility(IUserManager).make_user(self.address.email)
+        if self.address is None:
+            assert self.user.preferred_address is None, (
+                "Preferred address exists, but wasn't used in constructor")
+            addresses = list(self.user.addresses)
+            if len(addresses) == 0:
+                raise AssertionError('User has no addresses: {}'.format(
+                    self.user))
+            # This is rather arbitrary, but we have no choice.
+            self.address = addresses[0]
+        assert self.user is not None and self.address is not None, (
+            'Insane sanity check results')
+        # Is this subscriber already a member?
+        if (self.which is WhichSubscriber.user and
+                self.user.preferred_address is not None):
+            subscriber = self.user
+        else:
+            subscriber = self.address
+        if self.mlist.is_subscribed(subscriber):
+            # 2017-04-22 BAW: This branch actually *does* get covered, as I've
+            # verified by a full coverage run, but diffcov for some reason
+            # claims that the test added in the branch that added this code
+            # does not cover the change.  That seems like a bug in diffcov.
+            raise AlreadySubscribedError(           # pragma: no cover
+                self.mlist.fqdn_listname,
+                self.address.email,
+                MemberRole.member)
+        # Is this email address banned?
+        if IBanManager(self.mlist).is_banned(self.address.email):
+            raise MembershipIsBannedError(self.mlist, self.address.email)
+        # Check if there is already a subscription request for this email.
+        pendings = getUtility(IPendings).find(
+            mlist=self.mlist,
+            pend_type='subscription')
+        for token, pendable in pendings:
+            if pendable['email'] == self.address.email:
+                raise SubscriptionPendingError(self.mlist, self.address.email)
+        # Start out with the subscriber being the token owner.
+        self.push('verification_checks')
+
+    def _step_verification_checks(self):
+        # Is the address already verified, or is the pre-verified flag set?
+        if self.address.verified_on is None:
+            if self.pre_verified:
+                self.address.verified_on = now()
+            else:
+                # The address being subscribed is not yet verified, so we need
+                # to send a validation email that will also confirm that the
+                # user wants to be subscribed to this mailing list.
+                self.push('send_confirmation')
+                return
+        self.push('confirmation_checks')
+
+    def _step_confirmation_checks(self):
+        # If the list's subscription policy is open, then the user can be
+        # subscribed right here and now.
+        if self.mlist.subscription_policy is SubscriptionPolicy.open:
+            self.push('do_subscription')
+            return
+        # If we do not need the user's confirmation, then skip to the
+        # moderation checks.
+        if self.mlist.subscription_policy is SubscriptionPolicy.moderate:
+            self.push('moderation_checks')
+            return
+        # If the subscription has been pre-confirmed, then we can skip the
+        # confirmation check can be skipped.  If moderator approval is
+        # required we need to check that, otherwise we can go straight to
+        # subscription.
+        if self.pre_confirmed:
+            next_step = (
+                'moderation_checks'
+                if self.mlist.subscription_policy is
+                    SubscriptionPolicy.confirm_then_moderate   # noqa: E131
+                else 'do_subscription')
+            self.push(next_step)
+            return
+        # The user must confirm their subscription.
+        self.push('send_confirmation')
+
+    def _step_moderation_checks(self):
+        # Does the moderator need to approve the subscription request?
+        assert self.mlist.subscription_policy in (
+            SubscriptionPolicy.moderate,
+            SubscriptionPolicy.confirm_then_moderate,
+            ), self.mlist.subscription_policy
+        if self.pre_approved:
+            self.push('do_subscription')
+        else:
+            self.push('get_moderator_approval')
+
+    def _step_get_moderator_approval(self):
+        # Here's the next step in the workflow, assuming the moderator
+        # approves of the subscription.  If they don't, the workflow and
+        # subscription request will just be thrown away.
+        self._set_token(TokenOwner.moderator)
+        self.push('subscribe_from_restored')
+        self.save()
+        log.info('{}: held subscription request from {}'.format(
+            self.mlist.fqdn_listname, self.address.email))
+        # Possibly send a notification to the list moderators.
+        if self.mlist.admin_immed_notify:
+            subject = _(
+                'New subscription request to $self.mlist.display_name '
+                'from $self.address.email')
+            username = formataddr(
+                (self.subscriber.display_name, self.address.email))
+            template = getUtility(ITemplateLoader).get(
+                'list:admin:action:subscribe', self.mlist)
+            text = wrap(expand(template, self.mlist, dict(
+                member=username,
+                )))
+            # This message should appear to come from the <list>-owner so as
+            # to avoid any useless bounce processing.
+            msg = UserNotification(
+                self.mlist.owner_address, self.mlist.owner_address,
+                subject, text, self.mlist.preferred_language)
+            msg.send(self.mlist)
+        # The workflow must stop running here.
+        raise StopIteration
+
+    def _step_subscribe_from_restored(self):
+        # Prevent replay attacks.
+        self._set_token(TokenOwner.no_one)
+        # Restore a little extra state that can't be stored in the database
+        # (because the order of setattr() on restore is indeterminate), then
+        # subscribe the user.
+        if self.which is WhichSubscriber.address:
+            self.subscriber = self.address
+        else:
+            assert self.which is WhichSubscriber.user
+            self.subscriber = self.user
+        self.push('do_subscription')
+
+    def _step_do_subscription(self):
+        # We can immediately subscribe the user to the mailing list.
+        self.member = self.mlist.subscribe(self.subscriber)
+        assert self.token is None and self.token_owner is TokenOwner.no_one, (
+            'Unexpected active token at end of subscription workflow')
+
+    def _step_send_confirmation(self):
+        self._set_token(TokenOwner.subscriber)
+        self.push('do_confirm_verify')
+        self.save()
+        # Triggering this event causes the confirmation message to be sent.
+        notify(SubscriptionConfirmationNeededEvent(
+            self.mlist, self.token, self.address.email))
+        # Now we wait for the confirmation.
+        raise StopIteration
+
+    def _step_do_confirm_verify(self):
+        # Restore a little extra state that can't be stored in the database
+        # (because the order of setattr() on restore is indeterminate), then
+        # continue with the confirmation/verification step.
+        if self.which is WhichSubscriber.address:
+            self.subscriber = self.address
+        else:
+            assert self.which is WhichSubscriber.user
+            self.subscriber = self.user
+        # Reset the token so it can't be used in a replay attack.
+        self._set_token(TokenOwner.no_one)
+        # The user has confirmed their subscription request, and also verified
+        # their email address if necessary.  This latter needs to be set on the
+        # IAddress, but there's nothing more to do about the confirmation step.
+        # We just continue along with the workflow.
+        if self.address.verified_on is None:
+            self.address.verified_on = now()
+        # The next step depends on the mailing list's subscription policy.
+        next_step = ('moderation_checks'
+                     if self.mlist.subscription_policy in (
+                         SubscriptionPolicy.moderate,
+                         SubscriptionPolicy.confirm_then_moderate,
+                         )
+                     else 'do_subscription')
+        self.push(next_step)
+
+
+@public
+class UnSubscriptionWorkflow(SubscriptionWorkflowCommon):
+    """Workflow of a unsubscription request."""
+
+    name = 'unsubscription-default'
+    description = ''
+
+    initial_state = 'subscription_checks'
+    save_attributes = (
+        'pre_approved',
+        'pre_confirmed',
+        'address_key',
+        'user_key',
+        'subscriber_key',
+        'token_owner_key',
+        )
+
+    def __init__(self, mlist, subscriber=None, *,
+                 pre_approved=False, pre_confirmed=False):
+        super().__init__(mlist, subscriber)
+        if IAddress.providedBy(subscriber) or IUser.providedBy(subscriber):
+            self.member = self.mlist.regular_members.get_member(
+                self.address.email)
+        self.pre_confirmed = pre_confirmed
+        self.pre_approved = pre_approved
+
+    def _step_subscription_checks(self):
+        assert self.mlist.is_subscribed(self.subscriber)
+        self.push('confirmation_checks')
+
+    def _step_confirmation_checks(self):
+        # If list's unsubscription policy is open, the user can unsubscribe
+        # right now.
+        if self.mlist.unsubscription_policy is SubscriptionPolicy.open:
+            self.push('do_unsubscription')
+            return
+        # If we don't need the user's confirmation, then skip to the moderation
+        # checks.
+        if self.mlist.unsubscription_policy is SubscriptionPolicy.moderate:
+            self.push('moderation_checks')
+            return
+        # If the request is pre-confirmed, then the user can unsubscribe right
+        # now.
+        if self.pre_confirmed:
+            self.push('do_unsubscription')
+            return
+        # The user must confirm their un-subsbcription.
+        self.push('send_confirmation')
+
+    def _step_send_confirmation(self):
+        self._set_token(TokenOwner.subscriber)
+        self.push('do_confirm_verify')
+        self.save()
+        notify(UnsubscriptionConfirmationNeededEvent(
+            self.mlist, self.token, self.address.email))
+        raise StopIteration
+
+    def _step_moderation_checks(self):
+        # Does the moderator need to approve the unsubscription request?
+        assert self.mlist.unsubscription_policy in (
+            SubscriptionPolicy.moderate,
+            SubscriptionPolicy.confirm_then_moderate,
+            ), self.mlist.unsubscription_policy
+        if self.pre_approved:
+            self.push('do_unsubscription')
+        else:
+            self.push('get_moderator_approval')
+
+    def _step_get_moderator_approval(self):
+        self._set_token(TokenOwner.moderator)
+        self.push('unsubscribe_from_restored')
+        self.save()
+        log.info('{}: held unsubscription request from {}'.format(
+            self.mlist.fqdn_listname, self.address.email))
+        if self.mlist.admin_immed_notify:
+            subject = _(
+                'New unsubscription request to $self.mlist.display_name '
+                'from $self.address.email')
+            username = formataddr(
+                (self.subscriber.display_name, self.address.email))
+            template = getUtility(ITemplateLoader).get(
+                'list:admin:action:unsubscribe', self.mlist)
+            text = wrap(expand(template, self.mlist, dict(
+                member=username,
+                )))
+            # This message should appear to come from the <list>-owner so as
+            # to avoid any useless bounce processing.
+            msg = UserNotification(
+                self.mlist.owner_address, self.mlist.owner_address,
+                subject, text, self.mlist.preferred_language)
+            msg.send(self.mlist)
+        # The workflow must stop running here
+        raise StopIteration
+
+    def _step_do_confirm_verify(self):
+        # Restore a little extra state that can't be stored in the database
+        # (because the order of setattr() on restore is indeterminate), then
+        # continue with the confirmation/verification step.
+        if self.which is WhichSubscriber.address:
+            self.subscriber = self.address
+        else:
+            assert self.which is WhichSubscriber.user
+            self.subscriber = self.user
+        # Reset the token so it can't be used in a replay attack.
+        self._set_token(TokenOwner.no_one)
+        # Restore the member object.
+        self.member = self.mlist.regular_members.get_member(self.address.email)
+        # It's possible the member was already unsubscribed while we were
+        # waiting for the confirmation.
+        if self.member is None:
+            return
+        # The user has confirmed their unsubscription request
+        next_step = ('moderation_checks'
+                     if self.mlist.unsubscription_policy in (
+                          SubscriptionPolicy.moderate,
+                          SubscriptionPolicy.confirm_then_moderate,
+                          )
+                     else 'do_unsubscription')
+        self.push(next_step)
+
+    def _step_do_unsubscription(self):
+        try:
+            delete_member(self.mlist, self.address.email)
+        except NotAMemberError:
+            # The member has already been unsubscribed.
+            pass
+        self.member = None
+        assert self.token is None and self.token_owner is TokenOwner.no_one, (
+            'Unexpected active token at end of subscription workflow')
+
+    def _step_unsubscribe_from_restored(self):
+        # Prevent replay attacks.
+        self._set_token(TokenOwner.no_one)
+        if self.which is WhichSubscriber.address:
+            self.subscriber = self.address
+        else:
+            assert self.which is WhichSubscriber.user
+            self.subscriber = self.user
+        self.push('do_unsubscription')