Implement REFUSE_SECOND_PENDING setting to prevent multiple pending subscribes.

6 files changed, 43 insertions, 0 deletions

diff --git a/Mailman/Cgi/subscribe.py b/Mailman/Cgi/subscribe.py
index ce7940f9..795fc81b 100644
--- a/Mailman/Cgi/subscribe.py
+++ b/Mailman/Cgi/subscribe.py
@@ -291,6 +291,9 @@ your subscription.""")
 Your subscription request was deferred because %(x)s.  Your request has been
 forwarded to the list moderator.  You will receive email informing you of the
 moderator's decision when they get to your request.""")
+    except Errors.MMAlreadyPending:
+        # User already has a subscription pending
+        results = _('You already have a subscription pending confirmation')
     except Errors.MMAlreadyAMember:
         # Results string depends on whether we have private rosters or not
         if not privacy_results:
diff --git a/Mailman/Commands/cmd_subscribe.py b/Mailman/Commands/cmd_subscribe.py
index abe8b762..098740c8 100644
--- a/Mailman/Commands/cmd_subscribe.py
+++ b/Mailman/Commands/cmd_subscribe.py
@@ -128,6 +128,10 @@ the email address you gave is insecure."""))
     except Errors.MMAlreadyAMember:
         res.results.append(_('You are already subscribed!'))
         return STOP
+    except Errors.MMAlreadyPending:
+        res.results.append(
+            _('You already have a subscription pending confirmation'))
+        return STOP
     except Errors.MMCantDigestError:
         res.results.append(
             _('No one can subscribe to the digest of this list!'))
diff --git a/Mailman/Defaults.py.in b/Mailman/Defaults.py.in
index b45abf7b..277e3ab0 100755
--- a/Mailman/Defaults.py.in
+++ b/Mailman/Defaults.py.in
@@ -1122,6 +1122,14 @@ ANONYMOUS_LIST_KEEP_HEADERS = ['^(?!x-)', '^x-mailman-',
                                '^x-ack:', '^x-beenthere:',
                                '^x-list-administrivia:', '^x-spam-',
                               ]
+#
+# It is possible to mailbomb a third party by repeatrdly posting the subscribe
+# form.  You can prevent this by setting the following to Yes which will refuse
+# pending a subscription confirmation when one is already pending.  The down
+# side to this is if a subscriber loses or doesn't receive the confirmation
+# request email, she has to wait PENDING_REQUEST_LIFE (default 3 days) before
+# she can request another.
+REFUSE_SECOND_PENDING = No
 
 
 
diff --git a/Mailman/Errors.py b/Mailman/Errors.py
index f4895248..b502ffbf 100644
--- a/Mailman/Errors.py
+++ b/Mailman/Errors.py
@@ -31,6 +31,7 @@ class BadListNameError(MMListError): pass
 class MMMemberError(Exception): pass
 class MMBadUserError(MMMemberError): pass
 class MMAlreadyAMember(MMMemberError): pass
+class MMAlreadyPending(MMMemberError): pass
 
 # "New" style membership exceptions (new w/ MM2.1)
 class MemberError(Exception): pass
diff --git a/Mailman/MailList.py b/Mailman/MailList.py
index 12d75aff..9e6bbcb6 100644
--- a/Mailman/MailList.py
+++ b/Mailman/MailList.py
@@ -833,6 +833,25 @@ class MailList(HTMLFormatter, Deliverer, ListAdmin,
     #
     # Membership management front-ends and assertion checks
     #
+    def CheckPending(self, email):
+        """Check if there is already an unexpired pending subscription for
+        this email.
+        """
+        if not mm_cfg.REFUSE_SECOND_PENDING:
+            return False
+        pends = self._Pending__load()
+        # Save and reload the db to evict expired pendings.
+        self._Pending__save(pends)
+        pends = self._Pending__load()
+        for k, v in pends.items():
+            if k in ('evictions', 'version'):
+                continue
+            op, data = v
+            if (op == Pending.SUBSCRIPTION and
+                    data.address.lower() == email.lower()):
+                return True
+        return False
+
     def InviteNewMember(self, userdesc, text=''):
         """Invite a new member to the list.
 
@@ -919,6 +938,8 @@ class MailList(HTMLFormatter, Deliverer, ListAdmin,
         Utils.ValidateEmail(email)
         if self.isMember(email):
             raise Errors.MMAlreadyAMember, email
+        if self.CheckPending(email):
+            raise Errors.MMAlreadyPending, email
         if email.lower() == self.GetListEmail().lower():
             # Trying to subscribe the list to itself!
             raise Errors.MMBadEmailError
diff --git a/NEWS b/NEWS
index 5da676cb..39d11bca 100644
--- a/NEWS
+++ b/NEWS
@@ -38,6 +38,12 @@ Here is a history of user visible changes to Mailman.
       controls the dropping of addresses from the Cc: header in delivered
       messages by the duplicate avoidance process.  (LP: #1845751)
 
+    - There is a new REFUSE_SECOND_PENDING mm_cfg.py setting that will cause
+      a second request to subscribe to a list when there is already a pending
+      confirmation for that user.  This can be set to Yes to prevent
+      mailbombing of a third party by repeatedly posting the subscribe form.
+      (LP: #1859104)
+
   i18n
 
     - The Japanese translation has been updated by Yasuhito FUTATSUKI.