From 048ba4b5cdb55873a2a0296eeb805e3e6e37aea0 Mon Sep 17 00:00:00 2001
From: Roberto Rosario <roberto.rosario.gonzalez@gmail.com>
Date: Wed, 23 Mar 2016 19:47:41 -0400
Subject: [PATCH] Add file decryption support.

---
 mayan/apps/django_gpg/exceptions.py        |  4 ++--
 mayan/apps/django_gpg/managers.py          | 22 +++++++++++++++++++-
 mayan/apps/django_gpg/tests/literals.py    |  1 +
 mayan/apps/django_gpg/tests/test_models.py | 24 ++++++++++++++++++++--
 4 files changed, 46 insertions(+), 5 deletions(-)

diff --git a/mayan/apps/django_gpg/exceptions.py b/mayan/apps/django_gpg/exceptions.py
index 14dbe5ffa8..0afb08945a 100644
--- a/mayan/apps/django_gpg/exceptions.py
+++ b/mayan/apps/django_gpg/exceptions.py
@@ -9,7 +9,7 @@ class GPGException(Exception):
     pass
 
 
-class GPGVerificationError(GPGException):
+class VerificationError(GPGException):
     pass
 
 
@@ -17,7 +17,7 @@ class GPGSigningError(GPGException):
     pass
 
 
-class GPGDecryptionError(GPGException):
+class DecryptionError(GPGException):
     pass
 
 
diff --git a/mayan/apps/django_gpg/managers.py b/mayan/apps/django_gpg/managers.py
index f99e703d01..e1435ca0dc 100644
--- a/mayan/apps/django_gpg/managers.py
+++ b/mayan/apps/django_gpg/managers.py
@@ -10,7 +10,7 @@ import gnupg
 from django.db import models
 
 from .classes import KeyStub, SignatureVerification
-from .exceptions import KeyDoesNotExist, KeyFetchingError
+from .exceptions import DecryptionError, KeyDoesNotExist, KeyFetchingError
 from .literals import KEY_TYPE_PUBLIC, KEY_TYPE_SECRET
 from .settings import setting_gpg_path, setting_keyserver
 
@@ -18,6 +18,26 @@ logger = logging.getLogger(__name__)
 
 
 class KeyManager(models.Manager):
+    def decrypt_file(self, file_object):
+        temporary_directory = tempfile.mkdtemp()
+
+        os.chmod(temporary_directory, 0x1C0)
+
+        gpg = gnupg.GPG(
+            gnupghome=temporary_directory, gpgbinary=setting_gpg_path.value
+        )
+
+        decrypt_result = gpg.decrypt_file(file=file_object)
+
+        shutil.rmtree(temporary_directory)
+
+        logger.debug('decrypt_result.__dict__: %s', decrypt_result.__dict__)
+
+        if not decrypt_result.status or decrypt_result.status == 'no data was provided':
+            raise DecryptionError('Unable to decrypt file')
+
+        return str(decrypt_result)
+
     def receive_key(self, key_id):
         temporary_directory = tempfile.mkdtemp()
 
diff --git a/mayan/apps/django_gpg/tests/literals.py b/mayan/apps/django_gpg/tests/literals.py
index d37e28ba1f..908181254a 100644
--- a/mayan/apps/django_gpg/tests/literals.py
+++ b/mayan/apps/django_gpg/tests/literals.py
@@ -77,3 +77,4 @@ TEST_SIGNED_FILE = os.path.join(
     settings.BASE_DIR, 'mayan', 'apps', 'django_gpg', 'tests', 'contrib',
     'test_files', 'test_file.txt.gpg'
 )
+TEST_SIGNED_FILE_CONTENT = 'test_file.txt\n'
diff --git a/mayan/apps/django_gpg/tests/test_models.py b/mayan/apps/django_gpg/tests/test_models.py
index 484e8b64d9..fc098846bf 100644
--- a/mayan/apps/django_gpg/tests/test_models.py
+++ b/mayan/apps/django_gpg/tests/test_models.py
@@ -1,13 +1,15 @@
 from __future__ import unicode_literals
 
+import tempfile
+
 from django.test import TestCase
 
-from ..exceptions import KeyDoesNotExist
+from ..exceptions import DecryptionError, KeyDoesNotExist
 from ..models import Key
 
 from .literals import (
     TEST_KEY_DATA, TEST_KEY_FINGERPRINT, TEST_SEARCH_FINGERPRINT,
-    TEST_SEARCH_UID, TEST_SIGNED_FILE
+    TEST_SEARCH_UID, TEST_SIGNED_FILE, TEST_SIGNED_FILE_CONTENT
 )
 
 
@@ -62,3 +64,21 @@ class KeyTestCase(TestCase):
         with open(TEST_SIGNED_FILE) as signed_file:
             with self.assertRaises(KeyDoesNotExist):
                 Key.objects.verify_file(signed_file, key_fingerprint='999')
+
+    def test_signed_file_decryption(self):
+        Key.objects.create(key_data=TEST_KEY_DATA)
+
+        with open(TEST_SIGNED_FILE) as signed_file:
+            result = Key.objects.decrypt_file(file_object=signed_file)
+
+        self.assertEqual(result, TEST_SIGNED_FILE_CONTENT)
+
+    def test_cleartext_file_decryption(self):
+        cleartext_file = tempfile.TemporaryFile()
+        cleartext_file.write('test')
+        cleartext_file.seek(0)
+
+        with self.assertRaises(DecryptionError):
+            Key.objects.decrypt_file(file_object=cleartext_file)
+
+        cleartext_file.close()