Added support for a shared secret in email

docs/consumption.rst

@@ -90,13 +90,16 @@ So, with all that in mind, here's what you do to get it running:
    folder in an existing email box and note the path to that folder.
 2. In ``settings.py`` set all of the appropriate values in ``MAIL_CONSUMPTION``.
    If you decided to use a subfolder of an existing account, then make sure you
-   set ``INBOX`` accordingly here.
+   set ``INBOX`` accordingly here.  You also have to set the
+   ``UPLOAD_SHARED_SECRET`` to something you can remember 'cause you'll have to
+   include that in every email you send.
 3. Restart the :ref:`consumer <utilities-consumer>`.  The consumer will check
    the configured email account every 10 minutes for something new and pull down
    whatever it finds.
 4. Send yourself an email!  Note that the subject is treated as the file name,
    so if you set the subject to ``Sender - Title - tag,tag,tag``, you'll get
-   what you expect.
+   what you expect.  Also, you must include the aforementioned secret string in
+   every email so the fetcher knows that it's safe to import.
 5. After a few minutes, the consumer will poll your mailbox, pull down the
    message, and place the attachment in the consumption directory with the
    appropriate name.  A few minutes later, the consumer will import it like any

src/documents/mail.py

@@ -1,11 +1,12 @@
 import datetime
-import email
 import imaplib
 import os
 import re
 import time
 
 from base64 import b64decode
+from email import policy
+from email.parser import BytesParser
 from dateutil import parser
 
 from django.conf import settings
@@ -29,14 +30,7 @@ class Message(Renderable):
     and n attachments, and that we don't care about the message body.
     """
 
-    def _set_time(self, message):
-        self.time = datetime.datetime.now()
-        message_time = message.get("Date")
-        if message_time:
-            try:
-                self.time = parser.parse(message_time)
-            except (ValueError, AttributeError):
-                pass  # We assume that "now" is ok
+    SECRET = settings.UPLOAD_SHARED_SECRET
 
     def __init__(self, data, verbosity=1):
         """
@@ -50,17 +44,15 @@ class Message(Renderable):
         self.time = None
         self.attachment = None
 
-        message = email.message_from_bytes(data)
-        self.subject = message.get("Subject").replace("\r\n", "")
+        message = BytesParser(policy=policy.default).parsebytes(data)
+        self.subject = str(message["Subject"]).replace("\r\n", "")
+        self.body = str(message.get_body())
+
+        self.check_subject()
+        self.check_body()
 
         self._set_time(message)
 
-        if self.subject is None:
-            raise InvalidMessageError("Message does not have a subject")
-        if not Sender.SAFE_REGEX.match(self.subject):
-            raise InvalidMessageError("Message subject is unsafe: {}".format(
-                self.subject))
-
         self._render('Fetching email: "{}"'.format(self.subject), 1)
 
         attachments = []
@@ -94,6 +86,26 @@ class Message(Renderable):
     def __bool__(self):
         return bool(self.attachment)
 
+    def check_subject(self):
+        if self.subject is None:
+            raise InvalidMessageError("Message does not have a subject")
+        if not Sender.SAFE_REGEX.match(self.subject):
+            raise InvalidMessageError("Message subject is unsafe: {}".format(
+                self.subject))
+
+    def check_body(self):
+        if self.SECRET not in self.body:
+            raise InvalidMessageError("The secret wasn't in the body")
+
+    def _set_time(self, message):
+        self.time = datetime.datetime.now()
+        message_time = message.get("Date")
+        if message_time:
+            try:
+                self.time = parser.parse(message_time)
+            except (ValueError, AttributeError):
+                pass  # We assume that "now" is ok
+
     @property
     def file_name(self):
         return "{}.{}".format(self.subject, self.attachment.suffix)

src/documents/tests/samples/mail.txt

@@ -38,7 +38,7 @@ This is a multi-part message in MIME format.
 Content-Type: text/plain; charset=utf-8
 Content-Transfer-Encoding: 7bit
 
-This is the test body.
+The secret word is "paperless" :-)
 
 --------------090701020702030809070008
 Content-Type: application/pdf;