Reject emails attachments of size 0

Thanks to Robert Schoeftner (@robert.schoeftner)for the report
and solution. GitLab issue #574.

Signed-off-by: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>

HISTORY.rst

@@ -24,6 +24,8 @@
 * Add support for server side link badges.
 * Add API to list all templates.
 * Remove newlines from the rendered templates.
+* Reject emails attachments of size 0. Thanks to Robert Schoeftner
+  (@robert.schoeftner)for the report and solution. GitLab issue #574.
 
 3.1.9 (2018-11-01)
 ==================

mayan/apps/sources/models.py

@@ -602,6 +602,11 @@ class EmailBaseModel(IntervalBaseModel):
             # Treat inlines as attachments, both are extracted and saved as
             # documents
             if message.is_attachment() or message.is_inline():
+
+                # Reject zero length attachments
+                if len(message.body) == 0:
+                    return
+
                 label = message.detected_file_name or 'attachment-{}'.format(counter)
                 with ContentFile(content=message.body, name=label) as file_object:
                     if label == source.metadata_attachment_name:

mayan/apps/sources/tests/literals.py

@@ -109,6 +109,31 @@ AAALewAAC3sBSRnwgAAAABl0RVh0U29mdHdhcmUAd3d3Lmlua3NjYXBlLm9yZ5vuPBoAAALnSURB
 QCDLAIEsAwSyDBDIMkAgywCBLAMEsgwQyDJAIMsAgSwDBLIMEMgyQCDLAIEsAwSyDBDIMkAg6wK+
 4gU280YtuwAAAABJRU5ErkJggg==
 --089e0149bb0ea4e55c051712afb5--'''
+TEST_EMAIL_ZERO_LENGTH_ATTACHMENT = '''From rosarior@localhost Tue Apr  2 23:40:26 2019
+Received: from rosarior (uid 1000)
+    (envelope-from rosarior@localhost)
+    id 2011e6
+    by localhost (DragonFly Mail Agent v0.11);
+    Tue, 02 Apr 2019 23:40:26 -0400
+Message-ID: <22514.1554262827@localhost>
+Mime-Version: 1.0
+To: rosarior@localhost
+Subject: mpack
+Content-Type: multipart/mixed; boundary="-"
+Date: Tue, 02 Apr 2019 23:40:26 -0400
+From: <rosarior@localhost>
+
+This is a MIME encoded message.  Decode it with "munpack"
+or any other MIME reading software.  Mpack/munpack is available
+via anonymous FTP in ftp.andrew.cmu.edu:pub/mpack/
+---
+Content-Type: application/octet-stream; name="zero"
+Content-Transfer-Encoding: base64
+Content-Disposition: inline; filename="zero"
+Content-MD5: 1B2M2Y8AsgTpgAmY7PhCfg==
+
+
+-----'''
 TEST_SOURCE_LABEL = 'test source'
 TEST_SOURCE_UNCOMPRESS_N = 'n'
 TEST_STAGING_PREVIEW_WIDTH = 640

mayan/apps/sources/tests/test_models.py

@@ -25,7 +25,7 @@ from .literals import (
     TEST_EMAIL_ATTACHMENT_AND_INLINE, TEST_EMAIL_BASE64_FILENAME,
     TEST_EMAIL_BASE64_FILENAME_FROM, TEST_EMAIL_BASE64_FILENAME_SUBJECT,
     TEST_EMAIL_INLINE_IMAGE, TEST_EMAIL_NO_CONTENT_TYPE,
-    TEST_EMAIL_NO_CONTENT_TYPE_STRING
+    TEST_EMAIL_NO_CONTENT_TYPE_STRING, TEST_EMAIL_ZERO_LENGTH_ATTACHMENT
 )
 
 
@@ -106,6 +106,17 @@ class EmailFilenameDecodingTestCase(BaseTestCase):
             TEST_EMAIL_NO_CONTENT_TYPE_STRING in Document.objects.first().open().read()
         )
 
+    def test_decode_email_zero_length_attachment(self):
+        self._create_email_source()
+        self.source.store_body=False
+        self.source.save()
+
+        EmailBaseModel.process_message(
+            source=self.source, message_text=TEST_EMAIL_ZERO_LENGTH_ATTACHMENT
+        )
+
+        self.assertEqual(Document.objects.count(), 0)
+
     def test_decode_email_with_inline_image(self):
         self._create_email_source()
         EmailBaseModel.process_message(
@@ -127,7 +138,6 @@ class EmailFilenameDecodingTestCase(BaseTestCase):
         self.assertQuerysetEqual(
             ordered=False, qs=Document.objects.all(), values=(
                 '<Document: test-01.png>', '<Document: email_body.html>',
-                '<Document: test-02.png>'
             ),
         )
 
@@ -170,7 +180,7 @@ class EmailFilenameDecodingTestCase(BaseTestCase):
         )
 
         # Only two attachments, no body document
-        self.assertEqual(2, Document.objects.count())
+        self.assertEqual(1, Document.objects.count())
 
     def test_document_upload_with_body(self):
         self._create_email_source()
@@ -180,7 +190,7 @@ class EmailFilenameDecodingTestCase(BaseTestCase):
         )
 
         # Only two attachments and a body document
-        self.assertEqual(3, Document.objects.count())
+        self.assertEqual(2, Document.objects.count())
 
 
 @override_settings(OCR_AUTO_OCR=False)