Allow file upload to backends other than S3

We would like to support open assessment file uploads for open-edx
installs without access to S3, e.g: to the local fileystem. To that end,
we propose to abstract away some of the logic behind the file upload
backends so that other backends may be implemented.

In this proposed implementation, the uploaded files are stored in the
following folder structure:

        root/bucket/prefix/
                filename.jpg/
                        content
                        metadata.json

Note that a couple new settings need to be defined in order to use this
feature; a new urls.py file must also be included.

openassessment/fileupload/api.py

@@ -4,180 +4,17 @@ associated with submissions. This can be used to upload new files and provide
 URLs to the new location.
 
 """
-import boto
-import logging
-from django.conf import settings
-
-logger = logging.getLogger("openassessment.fileupload.api")
-
-
-class FileUploadError(Exception):
-    """An error related to uploading files
-
-    This is the generic error raised when a file could not be uploaded.
-
-    """
-    pass
-
-
-class FileUploadInternalError(FileUploadError):
-    """An error internal to the File Upload API.
-
-    This is an error raised when file upload failed due to internal problems in
-    the File Upload API, beyond the intervention of the requester.
-
-    """
-    pass
-
-
-class FileUploadRequestError(FileUploadError):
-    """This error is raised when the request has invalid parameters for upload.
-
-    This error will be raised if the file being uploaded is somehow invalid,
-    based on type restrictions, size restrictions, upload limits, etc.
-
-    """
-    pass
-
-
-# The setting used to find the name of the AWS Bucket used for uploading
-# content.
-BUCKET_SETTING = "FILE_UPLOAD_STORAGE_BUCKET_NAME"
-
-# The setting used to prefix uploaded files using this service.
-FILE_STORAGE_SETTING = "FILE_UPLOAD_STORAGE_PREFIX"
-
-# The default file storage prefix.
-FILE_STORAGE = "submissions_attachments"
 
+from . import backends
 
 def get_upload_url(key, content_type):
-    """Request a one-time upload URL to upload files.
-
-    Requests a URL for a one-time file upload.
-
-    Args:
-        key (str): A unique identifier used to construct the upload location and
-            later, can be used to retrieve the same information. This service
-            must be able to identify data for both upload and download using
-            this key.
-        content_type (str): The content type for the file.
-
-    Returns:
-        A URL (str) to use for a one-time upload.
-
-    Raises:
-        FileUploadInternalError: Raised when an internal error occurs while
-            retrieving a one-time URL.
-        FileUploadRequestError: Raised when the request failed due to
-            request restrictions
-
     """
-    bucket_name, key_name = _retrieve_parameters(key)
-    try:
-        conn = _connect_to_s3()
-        upload_url = conn.generate_url(
-            3600,
-            'PUT',
-            bucket_name,
-            key_name,
-            headers={'Content-Length': '5242880', 'Content-Type': content_type}
-        )
-        return upload_url
-    except Exception as ex:
-        logger.exception(
-            u"An internal exception occurred while generating an upload URL."
-        )
-        raise FileUploadInternalError(ex)
-
-
-def get_download_url(key):
-    """Requests a URL to download the related file from.
-
-    Requests a URL for the given student_item.
-
-    Args:
-        key (str): A unique identifier used to identify the data requested for
-            download. This service must be able to identify data for both
-            upload and download using this key.
-
-    Returns:
-        A URL (str) to use for downloading related files. If no file is found,
-        returns an empty string.
-
+    Returns a url (absolute or relative, depending on the endpoint) which can be used to upload a file to.
     """
-    bucket_name, key_name = _retrieve_parameters(key)
-    try:
-        conn = _connect_to_s3()
-        bucket = conn.get_bucket(bucket_name)
-        s3_key = bucket.get_key(key_name)
-        return s3_key.generate_url(expires_in=1000) if s3_key else ""
-    except Exception as ex:
-        logger.exception(
-            u"An internal exception occurred while generating a download URL."
-        )
-        raise FileUploadInternalError(ex)
-
-
-def _connect_to_s3():
-    """Connect to s3
-
-    Creates a connection to s3 for file URLs.
-
-    """
-    # Try to get the AWS credentials from settings if they are available
-    # If not, these will default to `None`, and boto will try to use
-    # environment vars or configuration files instead.
-    aws_access_key_id = getattr(settings, 'AWS_ACCESS_KEY_ID', None)
-    aws_secret_access_key = getattr(settings, 'AWS_SECRET_ACCESS_KEY', None)
-
-    return boto.connect_s3(
-        aws_access_key_id=aws_access_key_id,
-        aws_secret_access_key=aws_secret_access_key
-    )
-
-
-def _retrieve_parameters(key):
-    """
-    Simple utility function to validate settings and arguments before compiling
-    bucket names and key names.
-
-    Args:
-        key (str): Custom key passed in with the request.
-
-    Returns:
-        A tuple of the bucket name and the complete key.
-
-    Raises:
-        FileUploadRequestError
-        FileUploadInternalError
+    return backends.get_backend().get_upload_url(key, content_type)
 
+def get_download_url(key):
     """
-    if not key:
-        raise FileUploadRequestError("Key required for URL request")
-
-    bucket_name = getattr(settings, BUCKET_SETTING, None)
-    if not bucket_name:
-        raise FileUploadInternalError("No bucket name configured for FileUpload Service.")
-    return bucket_name, _get_key_name(key)
-
-
-def _get_key_name(key):
-    """Construct a key name with the given string and configured prefix.
-
-    Constructs a unique key with the specified path and the service-specific
-    configured prefix.
-
-    Args:
-        key (str): Key to identify data for both upload and download.
-
-    Returns:
-        A key name (str) to use constructing URLs.
+    Returns the url at which the file that corresponds to the key can be downloaded.
     """
-    # The specified file prefix for the storage must be publicly viewable
-    # or all uploaded images will not be seen.
-    prefix = getattr(settings, FILE_STORAGE_SETTING, FILE_STORAGE)
-    return u"{prefix}/{key}".format(
-        prefix=prefix,
-        key=key
-    )
+    return backends.get_backend().get_download_url(key)
\ No newline at end of file

openassessment/fileupload/backends/__init__.py

+from . import s3
+from . import filesystem
+
+from django.conf import settings
+
+
+def get_backend():
+    # Use S3 backend by default (current behaviour)
+    backend_setting = getattr(settings, "ORA2_FILEUPLOAD_BACKEND", "s3")
+    if backend_setting == "s3":
+        return s3.Backend()
+    elif backend_setting == "filesystem":
+        return filesystem.Backend()
+    else:
+        raise ValueError("Invalid ORA2_FILEUPLOAD_BACKEND setting value: %s" % backend_setting)

openassessment/fileupload/backends/base.py

+import abc
+
+from django.conf import settings
+
+from ..exceptions import FileUploadInternalError
+from ..exceptions import FileUploadRequestError
+
+
+class Settings(object):
+    """Store settings related to file upload
+
+    The following settings are used:
+
+        FILE_UPLOAD_STORAGE_BUCKET_NAME (str, required): name of the bucket
+        (AWS or local file directory) to which content will be uploaded.
+
+        FILE_STORAGE_STORAGE_PREFIX (str, defaults to
+        DEFAULT_FILE_UPLOAD_STORAGE_PREFIX): this will be used to prefix all
+        stored file names. The specified file prefix for the storage must be
+        publicly viewable or all uploaded files will not be seen.
+    """
+    DEFAULT_FILE_UPLOAD_STORAGE_PREFIX = "submissions_attachments"
+
+    @classmethod
+    def get_bucket_name(cls):
+        bucket_name = getattr(settings, "FILE_UPLOAD_STORAGE_BUCKET_NAME", None)
+        if not bucket_name:
+            raise FileUploadInternalError("No bucket name configured for FileUpload Service.")
+        return bucket_name
+
+    @classmethod
+    def get_prefix(cls):
+        """Return the prefix for stored files.
+
+        Defaults to the DEFAULT_FILE_UPLOAD_STORAGE_PREFIX class attribute.
+        """
+        return getattr(settings, "FILE_UPLOAD_STORAGE_PREFIX", cls.DEFAULT_FILE_UPLOAD_STORAGE_PREFIX)
+
+
+class BaseBackend(object):
+
+    __metaclass__ = abc.ABCMeta
+
+    # Time (in seconds) before an upload url expires
+    UPLOAD_URL_TIMEOUT = 3600
+
+    # Time (in seconds) before a download url expires
+    DOWNLOAD_URL_TIMEOUT = 1000
+
+    @abc.abstractmethod
+    def get_upload_url(self, key, content_type):
+        """Request a one-time upload URL to upload files.
+
+        Requests a URL for a one-time file upload.
+
+        Args:
+            key (str): A unique identifier used to construct the upload location and
+                later, can be used to retrieve the same information. This service
+                must be able to identify data for both upload and download using
+                this key.
+            content_type (str): The content type for the file.
+
+        Returns:
+            A URL (str) to use for a one-time upload.
+
+        Raises:
+            FileUploadInternalError: Raised when an internal error occurs while
+                retrieving a one-time URL.
+            FileUploadRequestError: Raised when the request failed due to
+                request restrictions
+
+        """
+        raise NotImplementedError
+
+    @abc.abstractmethod
+    def get_download_url(self, key):
+        """Requests a URL to download the related file from.
+
+        Requests a URL for the given student_item.
+
+        Args:
+            key (str): A unique identifier used to identify the data requested for
+                download. This service must be able to identify data for both
+                upload and download using this key.
+
+        Returns:
+            A URL (str) to use for downloading related files. If no file is found,
+            returns an empty string.
+
+        """
+        raise NotImplementedError
+
+    def _retrieve_parameters(self, key):
+        """
+        Simple utility function to validate settings and arguments before compiling
+        bucket names and key names.
+
+        Args:
+            key (str): Custom key passed in with the request.
+
+        Returns:
+            A tuple of the bucket name and the complete key.
+
+        Raises:
+            FileUploadRequestError
+            FileUploadInternalError
+
+        """
+        if not key:
+            raise FileUploadRequestError("Key required for URL request")
+        return Settings.get_bucket_name(), self._get_key_name(key)
+
+
+    def _get_key_name(self, key):
+        """Construct a key name with the given string and configured prefix.
+
+        Constructs a unique key with the specified path and the service-specific
+        configured prefix.
+
+        Args:
+            key (str): Key to identify data for both upload and download.
+
+        Returns:
+            A key name (str) to use constructing URLs.
+        """
+        return "{prefix}/{key}".format(
+            prefix=Settings.get_prefix(),
+            key=key
+        )
+

openassessment/fileupload/backends/filesystem.py

+
+from .base import BaseBackend
+from .. import exceptions
+
+from django.conf import settings
+import django.core.cache
+from django.core.urlresolvers import reverse
+
+
+class Backend(BaseBackend):
+    """
+    Upload openassessment student files (images) to a local filesystem. Note
+    that in order to use this file storage backend, you need to include the
+    urls from openassessment.fileupload in your urls.py file:
+
+    E.g:
+        url(r'^openassessment/storage', include(openassessment.fileupload.urls)),
+
+    The ORA2_FILEUPLOAD_CACHE_NAME setting will also have to be defined for the
+    name of the django.core.cache instance which will maintain the list of
+    active storage URLs.
+
+    E.g:
+
+        ORA2_FILEUPLOAD_CACHE_NAME = "ora2-storage"
+        CACHES = {
+            ...
+            'ora2-storage': {
+                'BACKEND': 'django.core.cache.backends.memcached.MemcachedCache',
+                ...
+            },
+            ...
+        }
+    """
+
+    def get_upload_url(self, key, content_type):
+        make_upload_url_available(self._get_key_name(key), self.UPLOAD_URL_TIMEOUT)
+        return self._get_url(key)
+
+    def get_download_url(self, key):
+        make_download_url_available(self._get_key_name(key), self.DOWNLOAD_URL_TIMEOUT)
+        return self._get_url(key)
+
+    def _get_url(self, key):
+        key_name = self._get_key_name(key)
+        url = reverse("openassessment-filesystem-storage", kwargs={'key': key_name})
+        return url
+
+
+def get_cache():
+    """
+    Returns a django.core.cache instance in charge of maintaining the
+    authorized upload and download URL.
+
+    Raises:
+        FileUploadInternalError if the cache name setting is not defined.
+        InvalidCacheBackendError if the corresponding cache backend has not
+        been configured.
+    """
+    cache_name = getattr(settings, "ORA2_FILEUPLOAD_CACHE_NAME", None)
+    if cache_name is None:
+        raise exceptions.FileUploadInternalError("Undefined cache backend for file upload")
+    return django.core.cache.get_cache(cache_name)
+
+
+def make_upload_url_available(url_key_name, timeout):
+    """
+    Authorize an upload URL.
+
+    Arguments:
+        url_key_name (str): key that uniquely identifies the upload url
+        timeout (int): time in seconds before the url expires
+    """
+    return get_cache().set(
+        get_upload_cache_key(url_key_name),
+        1, timeout
+    )
+
+def make_download_url_available(url_key_name, timeout):
+    """
+    Authorize a download URL.
+
+    Arguments:
+        url_key_name (str): key that uniquely identifies the url
+        timeout (int): time in seconds before the url expires
+    """
+    return get_cache().set(
+        get_download_cache_key(url_key_name),
+        1, timeout
+    )
+
+def is_upload_url_available(url_key_name):
+    """
+    Return True if the corresponding upload URL is available.
+    """
+    return get_cache().get(get_upload_cache_key(url_key_name)) is not None
+
+def is_download_url_available(url_key_name):
+    """
+    Return True if the corresponding download URL is available.
+    """
+    return get_cache().get(get_download_cache_key(url_key_name)) is not None
+
+def get_upload_cache_key(url_key_name):
+    return "upload/" + url_key_name
+
+def get_download_cache_key(url_key_name):
+    return "download/" + url_key_name

openassessment/fileupload/backends/s3.py

+import boto
+import logging
+from django.conf import settings
+
+logger = logging.getLogger("openassessment.fileupload.api")
+
+from .base import BaseBackend
+from ..exceptions import FileUploadInternalError
+
+
+class Backend(BaseBackend):
+
+    def get_upload_url(self, key, content_type):
+        bucket_name, key_name = self._retrieve_parameters(key)
+        try:
+            conn = _connect_to_s3()
+            upload_url = conn.generate_url(
+                expires_in=self.UPLOAD_URL_TIMEOUT,
+                method='PUT',
+                bucket=bucket_name,
+                key=key_name,
+                headers={'Content-Length': '5242880', 'Content-Type': content_type}
+            )
+            return upload_url
+        except Exception as ex:
+            logger.exception(
+                u"An internal exception occurred while generating an upload URL."
+            )
+            raise FileUploadInternalError(ex)
+
+
+    def get_download_url(self, key):
+        bucket_name, key_name = self._retrieve_parameters(key)
+        try:
+            conn = _connect_to_s3()
+            bucket = conn.get_bucket(bucket_name)
+            s3_key = bucket.get_key(key_name)
+            return s3_key.generate_url(expires_in=self.DOWNLOAD_URL_TIMEOUT) if s3_key else ""
+        except Exception as ex:
+            logger.exception(
+                u"An internal exception occurred while generating a download URL."
+            )
+            raise FileUploadInternalError(ex)
+
+
+def _connect_to_s3():
+    """Connect to s3
+
+    Creates a connection to s3 for file URLs.
+
+    """
+    # Try to get the AWS credentials from settings if they are available
+    # If not, these will default to `None`, and boto will try to use
+    # environment vars or configuration files instead.
+    aws_access_key_id = getattr(settings, 'AWS_ACCESS_KEY_ID', None)
+    aws_secret_access_key = getattr(settings, 'AWS_SECRET_ACCESS_KEY', None)
+
+    return boto.connect_s3(
+        aws_access_key_id=aws_access_key_id,
+        aws_secret_access_key=aws_secret_access_key
+    )
+
+

openassessment/fileupload/exceptions.py

+class FileUploadError(Exception):
+    """An error related to uploading files
+
+    This is the generic error raised when a file could not be uploaded.
+
+    """
+    pass
+
+
+class FileUploadInternalError(FileUploadError):
+    """An error internal to the File Upload API.
+
+    This is an error raised when file upload failed due to internal problems in
+    the File Upload API, beyond the intervention of the requester.
+
+    """
+    pass
+
+
+class FileUploadRequestError(FileUploadError):
+    """This error is raised when the request has invalid parameters for upload.
+
+    This error will be raised if the file being uploaded is somehow invalid,
+    based on type restrictions, size restrictions, upload limits, etc.
+
+    """
+    pass

openassessment/fileupload/tests/test_api.py

+# -*- coding: utf-8 -*-
+
 import boto
 from boto.s3.key import Key
 import ddt
+
+import json
+import os
+import shutil
+import tempfile
+
+from django.conf import settings
 from django.test import TestCase
 from django.test.utils import override_settings
+from django.core.urlresolvers import reverse
+
 from moto import mock_s3
 from mock import patch
 from nose.tools import raises
+
 from openassessment.fileupload import api
+from openassessment.fileupload import exceptions
+from openassessment.fileupload import views_filesystem as views
+from openassessment.fileupload.backends.base import Settings as FileUploadSettings
+from openassessment.fileupload.backends.filesystem import get_cache as get_filesystem_cache
 
 @ddt.ddt
 class TestFileUploadService(TestCase):
@@ -38,11 +54,11 @@ class TestFileUploadService(TestCase):
         downloadUrl = api.get_download_url("foo")
         self.assertIn("https://mybucket.s3.amazonaws.com/submissions_attachments/foo", downloadUrl)
 
-    @raises(api.FileUploadInternalError)
+    @raises(exceptions.FileUploadInternalError)
     def test_get_upload_url_no_bucket(self):
         api.get_upload_url("foo", "bar")
 
-    @raises(api.FileUploadRequestError)
+    @raises(exceptions.FileUploadRequestError)
     def test_get_upload_url_no_key(self):
         api.get_upload_url("", "bar")
 
@@ -53,7 +69,7 @@ class TestFileUploadService(TestCase):
         FILE_UPLOAD_STORAGE_BUCKET_NAME="mybucket"
     )
     @patch.object(boto, 'connect_s3')
-    @raises(api.FileUploadInternalError)
+    @raises(exceptions.FileUploadInternalError)
     def test_get_upload_url_error(self, mock_s3):
         mock_s3.side_effect = Exception("Oh noes")
         api.get_upload_url("foo", "bar")
@@ -65,8 +81,199 @@ class TestFileUploadService(TestCase):
         FILE_UPLOAD_STORAGE_BUCKET_NAME="mybucket"
     )
     @patch.object(boto, 'connect_s3')
-    @raises(api.FileUploadInternalError, mock_s3)
+    @raises(exceptions.FileUploadInternalError, mock_s3)
     def test_get_download_url_error(self, mock_s3):
         mock_s3.side_effect = Exception("Oh noes")
         api.get_download_url("foo")
 
+
+@override_settings(
+    ORA2_FILEUPLOAD_BACKEND="filesystem",
+    ORA2_FILEUPLOAD_ROOT='/tmp',
+    ORA2_FILEUPLOAD_CACHE_NAME='default',
+    FILE_UPLOAD_STORAGE_BUCKET_NAME="testbucket",
+)
+class TestFileUploadServiceWithFilesystemBackend(TestCase):
+    """
+    Test open assessment file upload to local file storage.
+    """
+
+    def setUp(self):
+        self.backend = api.backends.get_backend()
+
+        self.content = tempfile.TemporaryFile()
+        self.content.write("foobar content")
+        self.content.seek(0)
+
+        self.key = None
+        self.key_name = None
+        self.set_key("myfile.jpg")
+        self.content_type = "image/jpeg"
+
+        get_filesystem_cache().clear()
+        self.delete_data(self.key_name)
+
+
+    def tearDown(self):
+        self.delete_data(self.key_name)
+
+    def set_key(self, key):
+        self.key = key
+        self.key_name = os.path.join(FileUploadSettings.get_prefix(), self.key)
+
+    def delete_data(self, key_name):
+        try:
+            path = views.get_data_path(key_name)
+            if os.path.exists(path):
+                shutil.rmtree(path)
+        except exceptions.FileUploadInternalError:
+            pass
+
+    def test_get_backend(self):
+        self.assertTrue(isinstance(self.backend, api.backends.filesystem.Backend))
+
+    def test_get_file_path(self):
+        path1 = views.get_file_path("mykey1")
+        path2 = views.get_file_path("mykey2")
+        self.assertEqual(
+            os.path.join(
+                settings.ORA2_FILEUPLOAD_ROOT,
+                settings.FILE_UPLOAD_STORAGE_BUCKET_NAME,
+                "mykey1"
+            ),
+            os.path.dirname(path1)
+        )
+        self.assertNotEqual(path1, path2)
+
+    def test_hack_get_file_path(self):
+        expected_path = os.path.join(
+            settings.ORA2_FILEUPLOAD_ROOT,
+            settings.FILE_UPLOAD_STORAGE_BUCKET_NAME,
+            "key",
+            "content"
+        )
+        self.assertEqual(
+            expected_path,
+            os.path.abspath(views.get_file_path("../key"))
+        )
+        self.assertEqual(
+            expected_path,
+            os.path.abspath(views.get_file_path("../key/"))
+        )
+        self.assertEqual(
+            expected_path,
+            os.path.abspath(views.get_file_path(" ../key/ "))
+        )
+
+    def test_safe_save(self):
+        self.assertRaises(
+            exceptions.FileUploadRequestError,
+            views.safe_save,
+            "/tmp/nonauthorisedbucket/file.txt",
+            "content"
+        )
+
+    def test_delete_file_data_on_metadata_saving_error(self):
+        key = "key"
+        file_path = views.get_file_path(key)
+        non_existing_path = "/non/existing/path"
+
+        with patch('openassessment.fileupload.views_filesystem.get_metadata_path') as mock_get_metadata_path:
+            mock_get_metadata_path.return_value = non_existing_path
+            self.assertRaises(
+                exceptions.FileUploadRequestError,
+                views.save_to_file,
+                "key", "content", "metadata"
+            )
+
+        self.assertFalse(os.path.exists(file_path))
+        self.assertFalse(os.path.exists(non_existing_path))
+
+    @override_settings(ORA2_FILEUPLOAD_ROOT='')
+    def test_undefined_file_upload_root(self):
+        self.assertRaises(exceptions.FileUploadInternalError, views.get_file_path, self.key)
+
+    @override_settings(ORA2_FILEUPLOAD_ROOT='/tmp/nonexistingdirectory')
+    def test_file_upload_root_does_not_exist(self):
+        if os.path.exists(settings.ORA2_FILEUPLOAD_ROOT):
+            shutil.rmtree(settings.ORA2_FILEUPLOAD_ROOT)
+        self.assertRaises(exceptions.FileUploadInternalError, views.save_to_file, self.key, "content")
+
+    def test_post_is_405(self):
+        upload_url = self.backend.get_upload_url(self.key, "bar")
+        response = self.client.post(upload_url, data={"attachment": self.content})
+        self.assertEqual(405, response.status_code)
+
+    def test_metadata(self):
+        self.content_type = "image/bmp"
+        upload_url = self.backend.get_upload_url(self.key, self.content_type)
+
+        self.client.put(upload_url, data=self.content.read(), content_type=self.content_type)
+        metadata_path = views.get_metadata_path(self.key_name)
+        metadata = json.load(open(metadata_path))
+
+        self.assertIsNotNone(metadata_path)
+        self.assertTrue(os.path.exists(metadata_path), "No metadata found at %s" % metadata_path)
+        self.assertIn("Content-Type", metadata)
+        self.assertIn("Date", metadata)
+        self.assertIn("Content-MD5", metadata)
+        self.assertIn("Content-Length", metadata)
+
+    def test_upload_download(self):
+        upload_url = self.backend.get_upload_url(self.key, self.content_type)
+        download_url = self.backend.get_download_url(self.key)
+        file_path = views.get_file_path(self.key_name)
+
+        upload_response = self.client.put(upload_url, data=self.content.read(), content_type=self.content_type)
+        download_response = self.client.get(download_url)
+        self.content.seek(0)
+
+        self.assertIn("/" + self.key, upload_url)
+        self.assertEqual(200, upload_response.status_code)
+        self.assertEqual("", upload_response.content)
+        self.assertEqual(200, download_response.status_code)
+        self.assertEqual(
+            "attachment; filename=" + self.key,
+            download_response.get('Content-Disposition')
+        )
+        self.assertEqual(self.content_type, download_response.get('Content-Type'))
+        self.assertIn("foobar content", download_response.content)
+        self.assertTrue(os.path.exists(file_path), "File %s does not exist" % file_path)
+        with open(file_path) as f:
+            self.assertEqual(self.content.read(), f.read())
+
+    def test_download_content_with_no_content_type(self):
+        views.save_to_file(self.key_name, "uploaded content", metadata=None)
+        download_url = self.backend.get_download_url(self.key)
+
+        download_response = self.client.get(download_url)
+        self.assertEqual(200, download_response.status_code)
+        self.assertEqual('application/octet-stream', download_response["Content-Type"])
+
+    def test_upload_with_unauthorized_key(self):
+        upload_url = reverse("openassessment-filesystem-storage", kwargs={'key': self.key_name})
+
+        cache_before_request = get_filesystem_cache().get(self.key_name)
+        upload_response = self.client.put(upload_url, data=self.content.read(), content_type=self.content_type)
+        cache_after_request = get_filesystem_cache().get(self.key_name)
+        self.assertIsNone(cache_before_request)
+        self.assertEqual(404, upload_response.status_code)
+        self.assertIsNone(cache_after_request)
+
+    def test_download_url_with_unauthorized_key(self):
+        download_url = reverse("openassessment-filesystem-storage", kwargs={'key': self.key_name})
+        views.save_to_file(self.key_name, "uploaded content")
+        download_response = self.client.get(download_url)
+
+        self.assertEqual(404, download_response.status_code)
+
+    def test_upload_download_with_accented_key(self):
+        self.set_key("noël.jpg")
+        upload_url = self.backend.get_upload_url(self.key, self.content_type)
+        download_url = self.backend.get_download_url(self.key)
+
+        upload_response = self.client.put(upload_url, data=self.content.read(), content_type=self.content_type)
+        download_response = self.client.get(download_url)
+
+        self.assertEqual(200, upload_response.status_code)
+        self.assertEqual(200, download_response.status_code)

openassessment/fileupload/urls.py

+from django.conf.urls import patterns, url
+
+
+urlpatterns = patterns('openassessment.fileupload.views_filesystem',
+    url(r'^(?P<key>.+)/$', 'filesystem_storage', name='openassessment-filesystem-storage'),
+)

openassessment/fileupload/views_filesystem.py

+import hashlib
+import json
+import os
+
+from django.conf import settings
+from django.shortcuts import HttpResponse, Http404
+from django.utils import timezone
+from django.views.decorators.http import require_http_methods
+
+from . import exceptions
+from .backends.filesystem import is_upload_url_available, is_download_url_available
+from .backends.base import Settings
+
+
+@require_http_methods(["PUT", "GET"])
+def filesystem_storage(request, key):
+    """
+    Uploading and download files to the local filesystem backend.
+    """
+    if isinstance(key, unicode):
+        key = key.encode("utf-8")
+    if request.method == "PUT":
+        if not is_upload_url_available(key):
+            raise Http404()
+        content, metadata = get_content_metadata(request)
+        save_to_file(key, content, metadata)
+        return HttpResponse()
+    elif request.method == "GET":
+        if not is_download_url_available(key):
+            raise Http404()
+        return download_file(key)
+
+
+def download_file(key):
+    """Returns an HttpResponse to download the corresponding file"""
+
+    file_path = get_file_path(key)
+    metadata_path = get_metadata_path(key)
+    if not os.path.exists(file_path):
+        raise Http404()
+    with open(metadata_path) as f:
+        metadata = json.load(f)
+        content_type = metadata.get("Content-Type", 'application/octet-stream')
+    with open(file_path, 'r') as f:
+        response = HttpResponse(f.read(), content_type=content_type)
+        file_name = os.path.basename(os.path.dirname(file_path))
+        response['Content-Disposition'] = 'attachment; filename=' + file_name
+    return response
+
+
+def get_content_metadata(request):
+    """
+    Read the content and metadata associated to an HttpRequest.
+
+    Returns:
+        request body (str)
+        request metadata (dict)
+    """
+
+    metadata = {
+        "Content-Type": request.META["CONTENT_TYPE"],
+        "Date": str(timezone.now()),
+        "Content-MD5": hashlib.md5(request.body).hexdigest(),
+        "Content-Length": request.META["CONTENT_LENGTH"],
+    }
+    return request.body, metadata
+
+
+def save_to_file(key, content, metadata=None):
+    """
+    Save the content and metadata to a local file determined by the given key.
+
+    Arguments:
+        key (str): unique file identifier
+        content (str): uploaded file content
+        metadata (dict): json-dumpable data
+    """
+    file_path = get_file_path(key)
+    metadata_path = get_metadata_path(key)
+    if metadata is None:
+        metadata = {}
+
+    safe_save(file_path, content)
+    try:
+        safe_save(metadata_path, json.dumps(metadata))
+    except:
+        safe_remove(file_path)
+        safe_remove(metadata_path)
+        raise
+
+def safe_save(path, content):
+    """
+    Save content to path. Creates the appropriate directories, if required.
+
+    Raises:
+        FileUploadInternalError if the root directory does not exist or if we
+        try to save in an unauthorized directory.
+    """
+    dir_path = os.path.abspath(os.path.dirname(path))
+    if not dir_path.startswith(get_bucket_path()):
+        raise exceptions.FileUploadRequestError("Uploaded file name not allowed: '%s'" % path)
+    root_directory = get_root_directory_path()
+    if not os.path.exists(root_directory):
+        raise exceptions.FileUploadInternalError("File upload root directory does not exist: %s" % root_directory)
+    if not os.path.exists(dir_path):
+        os.makedirs(dir_path)
+    with open(path, 'w') as f:
+        f.write(content)
+
+def safe_remove(path):
+    """Remove a file if it exists.
+
+    Note that an exception will be raised if the file is not writable.
+    """
+    if os.path.exists(path):
+        os.remove(path)
+
+
+def get_file_path(key):
+    """
+    Returns the path to the content file.
+    """
+    return os.path.join(get_data_path(key), "content")
+
+
+def get_metadata_path(key):
+    """
+    Returns the path to the metadata file.
+    """
+    return os.path.join(get_data_path(key), "metadata.json")
+
+
+def get_data_path(key):
+    """
+    Returns the path to the directory which will store the content and metadata
+    files.
+    """
+    subdirectory = key.replace("..", "").strip("/ ")
+    return os.path.join(get_bucket_path(), subdirectory)
+
+
+def get_bucket_path():
+    """
+    Returns the path to the bucket directory.
+    """
+    dir_path = os.path.join(
+        get_root_directory_path(),
+        Settings.get_bucket_name(),
+    )
+    return os.path.abspath(dir_path)
+
+
+def get_root_directory_path():
+    """
+    Returns the path to the root directory in which bucket directories are stored.
+
+    Raises:
+        FileUploadInternalError if the root directory setting does not exist.
+    """
+    root_dir = getattr(settings, "ORA2_FILEUPLOAD_ROOT", None)
+    if not root_dir:
+        raise exceptions.FileUploadInternalError("Undefined file upload root directory setting")
+    return root_dir

openassessment/xblock/staff_info_mixin.py

@@ -24,6 +24,7 @@ from openassessment.assessment.api import self as self_api
 from openassessment.assessment.api import ai as ai_api
 from openassessment.fileupload import api as file_api
 from openassessment.workflow import api as workflow_api
+from openassessment.fileupload import exceptions as file_exceptions
 
 
 logger = logging.getLogger(__name__)
@@ -256,7 +257,7 @@ class StaffInfoMixin(object):
 
                 try:
                     submission['image_url'] = file_api.get_download_url(file_key)
-                except file_api.FileUploadError:
+                except file_exceptions.FileUploadError:
                     # Log the error, but do not prevent the rest of the student info
                     # from being displayed.
                     msg = (

openassessment/xblock/submission_mixin.py

@@ -4,7 +4,7 @@ from xblock.core import XBlock
 
 from submissions import api
 from openassessment.fileupload import api as file_upload_api
-from openassessment.fileupload.api import FileUploadError
+from openassessment.fileupload.exceptions import FileUploadError
 from openassessment.workflow import api as workflow_api
 from openassessment.workflow.errors import AssessmentWorkflowError
 from .resolve_dates import DISTANT_FUTURE

openassessment/xblock/test/test_staff_info.py

@@ -12,7 +12,7 @@ from openassessment.assessment.api import self as self_api
 from openassessment.assessment.api import ai as ai_api
 from openassessment.workflow import api as workflow_api
 from openassessment.assessment.errors.ai import AIError, AIGradingInternalError
-from openassessment.fileupload.api import FileUploadInternalError
+from openassessment.fileupload.exceptions import FileUploadInternalError
 from submissions import api as sub_api
 from openassessment.xblock.test.base import scenario, XBlockHandlerTestCase
 from xblock.core import XBlock

urls.py

@@ -4,6 +4,7 @@ from django.views.i18n import javascript_catalog
 from django.contrib import admin
 
 import openassessment.assessment.urls
+import openassessment.fileupload.urls
 import workbench.urls
 
 admin.autodiscover()
@@ -26,6 +27,9 @@ urlpatterns = patterns(
 
     # JavaScript i18n
     (r'^jsi18n/$', 'django.views.i18n.javascript_catalog', JS_INFO_DICT),
+
+    # File upload to local filesystem
+    url(r'^openassessment/storage', include(openassessment.fileupload.urls)),
 )
 
 # We need to do explicit setup of the Django debug toolbar because autodiscovery