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django-remotestorage 12.09.3

Unhosted remoteStorage server app for django

Latest Version: 13.08.0

django-remotestorage

Unhosted remoteStorage server implementation

This app is a server (storage) implementation for "stable" remoteStorage API version, specified here:

http://www.w3.org/community/unhosted/wiki/RemoteStorage-2011.10

Some parts of it (especially webfinger, oauth2, since I've used newer specs that were available at the time) might be compatible with newer ("experimental") API:

https://www.w3.org/community/rww/wiki/read-write-web-00#simple
http://www.w3.org/community/unhosted/wiki/Pds

But since remoteStorage.js 0.7.0 for experimental API is still under heavy development, I haven't tested whether it works with current implementation.

Package (and django app) was called django-unhosted in the past and was eventually renamed. If you're using django-unhosted package, please read the notes on migration under Installation section.

remoteStorage

Idea is that you can have storage account (with whatever policies and authentication) on host1 and some webapp (say, some visual editor, think MS Word) on host2.

To edit document in a webapp, generally host2 would have to implement some sort of user registration, storage (like docs.google.com) for edited docs, etc.

With remoteStorage, this storage don't have to be on host2, so you don't have to implement some complex policies and authenticated storage there to launch a full-featured webapp - it can open and save docs to any remote host which supports the protocol (which is basically GET/PUT from WebDAV with OAuth2 on top).

host1 can be your VPS, client machine itself (especially easy with direct IPv6, or IPv4 provided via some service like pagekite), some reliable cloud provider or whatever.

To fully understand how it all works, I recommend looking at OAuth2, WebDAV, CORS and Webfinger, which are basically all the technologies used to implement the protocol.

This django app fully implements web-facing storage for host1, complete with user registration forms (optional, users can be added by other django apps or via django admin interface otherwise), client access management interfaces and a simple demo client.

Security

Since applicaton is a public-internet-facing interface to your (possibly important) data and I'm in no way security expert or specialist, I recommend to pentest or validate the code before storing any sensitive data in it.

Data loss or corruption is much easier to prevent (and backups go a long way here, btw) than security exploits, so, again, please look at the code yourself and find issues there which I have a blind spot (not to mention lack of skills) for, thus won't be able to find on my own.

Example of obvious (to an outsider analysis) security flaws in another storage-server implementation can be found here, learn the lession there.

Installation

Requirements

oauth2app is not on PyPI at the moment, but pip can install it from github directly.

Various interfaces of the app use some external resources, like Twitter Bootstrap CSS file (served from bootstrapcdn.com) and remoteStorage.js, which can be served - and should be, if you're using https for interfaces - from local URLs, if available in STATIC_ROOT. See "Customization / Interfaces" for details.

Migration from django-unhosted

Package was called django-unhosted in the past, but it was decided to rename it before it was way too late.

Unfortunately, there's no easy way to rename django app and python package, especially if it's undesirable to keep older package names around for eternity, so some manual steps have to be taken in order to migrate to the new (django-remotestorage) app/package.

  • Uninstall django-unhosted python package (either through pip uninstall     django-unhosted, OS tools, or remove module path manually).
  • Rename all database tables with "django_unhosted" in name to be starting with "django_remotestorage" instead. Lots of easy-to-use GUI tools (such as pgadmin, phpPgAdmin, phpMyAdmin, phpSQLiteAdmin, etc) or native CLI interfaces (sqlite3 /path/to/db.sqlite, psql, mysql, etc) can be used for that.
  • Update settings.py and urlconf to import stuff from "django_remotestorage" module instead of "django_unhosted". Replace all "UNHOSTED_" in variable names to "REMOTESTORAGE_", if used in settings.py.
  • If you have a custom urlconf and/or templates, replace references to "unhosted" namespace with "remotestorage".

It should fairly straightforward, but feel free to open Issue or contact developers if the described process doesn't work for you.

Deployment / configuration

Django apps are deployed as a part of "django project", which is - at it's minimum - just a few configuration files, specifying which database to use, and which apps should handle which URLs.

TL;DR

Simple installation/setup from scratch may look like this.

Install the app itself (or not, it can be just checked-out into a project dir):

pip install django-remotestorage

...or, to install directly from git master branch:

pip install 'git+https://github.com/RemoteStorage/django-remotestorage.git#egg=django-remotestorage'

...or you can do it manually:

git clone https://github.com/RemoteStorage/django-remotestorage.git
cd django-remotestorage
python setup.py install
pip install -r requirements.txt # or download/install each by hand as well

"pip" tool, mentioned above, should usually come with OS of choice, otherwise see pip installation docs. Don't use "easy_install" for anything except installing the pip itself.

Install oauth2app in a similar fashion:

pip install 'git+https://github.com/hiidef/oauth2app.git#egg=oauth2app'

Then create and configure a django project:

cd
django-admin.py startproject myproject
cd myproject

# Update settings.py (sqlite3 is used as db here) and urls.py
sed -i \
    -e 's/'\''ENGINE'\''.*/"ENGINE": "django.db.backends.sqlite3",/' \
    -e 's/'\''NAME'\''.*/"NAME": "db.sqlite",/' \
    -e 's/STATIC_ROOT *=/STATIC_ROOT="./static"/' \
    myproject/settings.py
echo -e >>myproject/settings.py \
    'from django_remotestorage.settings_base import update_settings' \
    '\nupdate_settings(__name__)'
sed -i \
    -e '1afrom django_remotestorage.urls import remotestorage_patterns' \
    -e 's/# Examples:.*/("", include(remotestorage_patterns)),\n\n\0/' \
    myproject/urls.py

# Create database schema and link app static files to STATIC_ROOT
./manage.py syncdb --noinput
./manage.py migrate django_remotestorage
./manage.py collectstatic --noinput --link

# Run simple dev server
./manage.py runserver

(since webfinger protocol requires some sort of XRD authentication, like https, it won't work properly on such a simple setup)

More detailed explaination of configuration process follows.

Django project configuration

Main idea is that two config files (in django project) need to be updated - settings.py and urls.py.

There are several ways to update django settings.py to use the app:

  • If it's the only app in a django project and there's no custom settings.py already, options from django_remotestorage.settings_base module can be imported into it directly.

    To do that, add the following lines to the end of "{your_app_name}/settings.py" (or wherever DJANGO_SETTINGS_MODULE is used) file:

    from django_remotestorage.settings_base import *
    

    That will import all the options there (bare minimum that has to be changed) over those defined above in the original file.

    Note that list of overidden options include INSTALLED_APPS, MIDDLEWARE_CLASSES and such, which are not only often customized, but are usually specific to the django version installed, so you may alternatively insert that import line at the beginning of the settings.py, so everything defined after it will override the imported options.

  • If there's already some custom settings.py file available, there's django_remotestorage.settings_base.update_settings helper function available to update configuration without blindly overriding any options.

    It can be used at the end of settings.py file like this:

    from django_remotestorage.settings_base import update_settings
    update_settings(__name__)
    

    Full list of changes it'll make can be found in "updates" dict at the beginning of django_remotestorage.settings_base module.

    "update_settings" function also takes an optional "only" and "ignore" keywords (expecting an iterable of option names), which can be used to control which parameters should be updated or explicitly left untouched.

    This should be more safe, flexible and future-proof way of merging necessary option updates with existing (site-specific) configuration.

  • Update the file by hand.

    Default values for the most settings can be found in django documentation.

    For the class-listing type options, duplicate values may be omitted. Note that order of MIDDLEWARE_CLASSES is significant.

    OAUTH2_CLIENT_KEY_LENGTH = 1024
    OAUTH2_SCOPE_LENGTH = 2048
    
    TEMPLATE_CONTEXT_PROCESSORS = (
        ...whatever is already there...
        'django.core.context_processors.csrf',
        'django.core.context_processors.request',
        'django.contrib.messages.context_processors.messages',
        'django_remotestorage.utils.external_resources_context',
    )
    
    TEMPLATE_LOADERS = (
        ...whatever is already there...
        'django_remotestorage.apps.webfinger.xrd_gen.Loader',
    )
    
    MIDDLEWARE_CLASSES = (
        ...whatever is already there...
        <remove 'django.middleware.csrf.CsrfViewMiddleware', if it's there>
        ...whatever is already there, except for ConditionalGet / FetchFromCache...
        'django.contrib.messages.middleware.MessageMiddleware',
        ...ConditionalGetMiddleware and FetchFromCacheMiddleware (and such), if used...
    )
    
    INSTALLED_APPS = (
        ...whatever is already there...
        'django.contrib.messages',
        'django_remotestorage',
        'oauth2app',
        'south',
    )
    

    "south" should be omitted from INSTALLED_APPS, if not used.

In any case, if you've just created django project (with "django-admin.py startproject" or whatever), make sure to look through it's settings.py file and edit at least DATABASES, MEDIA_* and STATIC_* options. You might also want to set other (optonal) settings there - TIME_ZONE, ADMINS, LOGGING, etc.

As for urls.py, just add the following line to url patterns (importing remotestorage_patterns from django_remotestorage.urls module beforehand):

('', include(remotestorage_patterns)),

So it'd look like this:

...
from django_remotestorage.urls import remotestorage_patterns
...
urlpatterns = patterns('',
    ('', include(remotestorage_patterns)),
...

That will add all the app urls to the root-path (for the complete list of these paths, see the module code). To selectively disable some of the components, see "Customization" section.

Database schema

Then the usual drill is to create the necessary database schema for the app (if you get "Settings cannot be imported" error, make sure you run that from the same path as "settings.py" file):

django-admin.py syncdb

If South app is installed (and specified in the INSTALLED_APPS), you should also use it's migrations to create tables for which they are available:

django-admin.py migrate django_remotestorage

That command can (and should) also be run after django-remotestorage app updates to apply any possible changes to db schema.

Running

Pretty much anything that supports WSGI protocol can be used with django - there's nothing app-specific here, just plain django, which is (usually) used as a backend with some httpd via wsgi.

See django docs on deployment process for generic instructions.

Customization

Components

The app consists of several independent components (sub-apps, bound to url paths via django_remotestorage.urls):

  • Webfinger (name: webfinger, URL: {include_prefix}/.well-known/host-meta, {include_prefix}/webfinger; see django_remotestorage.apps.webfinger.urls, there are similar urlconf-files for other subapps).
  • OAuth2 (name: oauth2, URL: {include_prefix}/oauth2).
  • Storage API (name: api, URL: {include_prefix}/api).
  • Account/client management (name: "account", URL: {include_prefix}/account). Can also be enabled partially with the following names: "account_auth" (login/logout forms/links), "account_auth_management" (signup form), "account_client_management" (client/app access management interface for logged-in users). "account" is an alias for all of these interfaces.
  • Demo client (name: demo, URL: {include_prefix}/)

Some components provide links to each other (for example, webfinger provides links to OAuth2 and API in served XRD/JSON data), resolved as "remotestorage:{app}:{view_name}", so you can rebind these apps to any URLs, as long as you provide the same namespace/view_name for django "reverse()" function and "url" template tags.

When including "django_remotestorage.urls.remotestorage_patterns" directly (not the urlconfs from individual components), "REMOTESTORAGE_COMPONENTS" settings.py option can be set to an iterable of components which should be enabled, for example:

REMOTESTORAGE_COMPONENTS = 'webfinger', 'oauth2', 'api'

...will enable just Storage API, OAuth2 and Webfinger subapps - bare minimum for functional remoteStorage node. Unless some other means to authenticate django user (like django.contrib.auth.views.login or django.contrib.admin) are enabled, it might also be necessary to enable "account_auth" interface to pass OAuth2 authorization.

If "account" (or it's parts) and "demo" apps are omitted from urlconf entirely (if not needed), there won't be any links to them in OAuth2 access confirmation interface. Their interface pages and functionality won't be accessible.

"api" and "oauth2" sub-apps are not linked to any other components either, so may be used separately from others and from each other as well (e.g. if authorization server and storage are on a different hosts), but they must share a database in order for api to be able to validate auth tokens.

OAuth2

It's highly recommended to raise database field lengths (using oauth2app settings) before running syncdb for the first time:

  • OAUTH2_CLIENT_KEY_LENGTH = 1024 (default: 30)
  • OAUTH2_SCOPE_LENGTH = 2048 (default: 255)

See "Known Issues / OAuth2" section for more detailed explaination on why it should be done.

Another important tunable is OAUTH2_ACCESS_TOKEN_EXPIRATION (default: 3600 = 1 hour), which - at least with remoteStorage.js 0.6.9 ("stable" at the moment of writing) - essentially sets a maximal interval between the need to visit OAuth2 interface and get new access token, because remoteStorage.js doesn't seem to be able to refresh these.

Webfinger

If webfinger and host-meta requests for the domain should carry more data than just for remoteStorage, they can be extended either by replacing webfinger app entirely or adding custom templates for it.

Webfinger app is using "webfinger/host_meta.{xml,json}" and "webfinger/webfinger.{xml,json}" templates, provided by django_remotestorage.apps.webfinger.xrd_gen.Loader or generated dynamically (in case of json, if template provide can't be found).

See example xml templates in django_remotestorage/templates/webfinger/{host_meta,webfinger}.xml.example.

Storage / WebDAV

Provided remoteStorage is backed by (configurable) Django Storage API.

By default, DEFAULT_FILE_STORAGE storage class is used. Different storage class can be specified by "REMOTESTORAGE_DAV_STORAGE" parameter (passed to get_storage_class).

Examples of Storage API implementation might include:

But basically there's a client for pretty much any data storage technology - just google it, install and set REMOTESTORAGE_DAV_STORAGE (or DEFAULT_FILE_STORAGE) to it.

Default Storage (FileStorage) parameters can be configured with MEDIA_URL and MEDIA_ROOT settings, see "Managing files" django docs section for details.

There are also some optimization parameters:

  • REMOTESTORAGE_DAV_SENDFILE (bool, default: False)

    Pass Storage.path (if supported by backend) to httpd frontend via "X-Sendfile" header instead of the actual contents upon request, so that response can be served by frontend daemon directly without backend app involved.

  • REMOTESTORAGE_DAV_ACCEL (string, default: None)

    Return empty HttpResponse with "X-Accel-Redirect" header set to specified prefix (can be an empty string) plus the requested path, so the actual response can be served by apache mod_accel.

  • REMOTESTORAGE_DAV_REDIRECT (bool, default: False)

    Return redirect to MEDIA_URL (produced by Storage.url method). Used only if MEDIA_URL is set to non-empty string.

    Serve these urls only after checking oauth2app-generated bearer tokens in http "Authorization" header either with django (or custom python code) or some smart httpd.

    Do not configure httpd to serve paths from MEDIA_URL without authorization, because everyone will be able to bypass OAuth2 and gain access to anything in remoteStorage just by guessing file paths or getting/reusing them from js, which is really easy to exploit.

Interfaces

Mostly usual drill - put your own templates to loaders, specified in settings.py.

External resources that are served on these pages can be put to STATIC_ROOT to be served by local httpd instead. See django_remotestorage.utils.external_resources_context context processor for details.

Take special care to make resources local if you serve these interfaces over https - there's just no security gain if MitM can place any javascript (loaded over plain http) to a page.

Note that any/all of the UIs can be disabled, if they're not needed, just use REMOTESTORAGE_COMPONENTS option (described in "Components" section) or don't include them in the urlconf, cherry-picking whichever ones are actually needed.

One common case of customization is the need to put whole app into some subpath ("/remotestorage" in the example) can be addressed by putting this into the project's root urls.py:

from django.conf.urls import patterns, include, url

from django_remotestorage.apps.webfinger.urls import host_meta_patterns
from django_remotestorage.urls import remotestorage_patterns

urlpatterns = patterns('',
    url(r'', include(host_meta_patterns)),
    url(r'^remotestorage/', include(remotestorage_patterns)),
)

That way, demo client will be available at "/remotestorage" url and all the links will include that prefix (for example authorization link from webfinger will point to "/remotestorage/oauth2/authorize").

Make sure, however, that host_meta view of webfinger app is available at a well-known url "/.well-known/host-meta", hence the "host_meta_patterns" special-case link from root.

Commands

access_token_cleanup [options] [ username ... ]

Remove expired OAuth access tokens (just for username(s), if specified) from the database.

Can be occasionally run from cron (use --verbosity=0 to supress activity reports) to keep token number from growing indefinitely, removing non-refreshed or about-to-expire (with negative --grace-period) ones.

Usage example:

% ./manage.py access_token_cleanup -v2 -n -t 3600 test
Removing token: id=1, user=test, client_name=localhost, expired=2012-07-31 03:24:30+06:00.
1 access token(s) removed.

Known issues

These are implementation-related issues, not the issues with the protocols themselves (which doesn't imply there's none of the latter, just that it's not a place for them).

Webfinger

  • No easy support for signed XRD at the moment. Signed static xml "templates" (or just files, served from httpd) can be used as a workaround if TLS is not an option.

OAuth2

  • Stored object path (think "public/myphoto.jpg") is used as OAuth2 "scope" by remoteStorage. oauth2app basically keeps a single table of these (treating them as a finite up-front set of capabilities).

    Problems here:

    • oauth2app stores "scope" as a 255-char key, while paths / collection_names can potentially be longer. Upstream pull request to specify field length was merged (as of 19.07.2012), so use any newer version with the large-enough OAUTH2_SCOPE_LENGTH parameter in settings.py (it doesn't really affect performance of modern databases, just making your life a bit harder).
    • Currently, oauth2app checks existance of AccessRange (scope) models as they are specified in the request, even though access to some of them might not be authorized by user, requiring temporary creation of this clutter. Upstream pull request: https://github.com/hiidef/oauth2app/pull/32
    • There's some extra code/db overhead involved in maintaining the (pointless in this case) table.
  • remoteStorage.js 0.6.9 ("stable" version at the moment) has a known issue of passing legacy "path1,path2" as a "scope", further complicating things for oauth2app (which would think that it's a single capability, as per spec) if several paths are passed.

    Workaround used is to detect the old format by lack of ":rw" suffixes and update "scope" in the address by issuing a redirect.

    Note that since paths may contain commas, "path1,path2" can be ambiguous (because of this issue) and can be treated either as "path1:rw" and "path2:rw" or "path1,path2:rw". Current implementation chooses the former interpretation if there's no colon-delimeted suffix.

  • remoteStorage.js 0.6.9 ("stable" version at the moment) uses hostname of the app site as OAuth2 client_id, which, in oauth2app corresponds to the "key" field, which is just 32-chars long by default, which might not be enough for some hostnames, but can (and should!) be configured by OAUTH2_CLIENT_KEY_LENGTH parameter in django project's settings.py. Remember to do that before syncdb, or update the table column later.

    Possible workaround might be to use hashes as the client_id's internally and redirect remoteStorage requests with "client_id=hostname.com" to something like "client_id=sha1:bbc21f0ccb5dfbf81f5043d78aa".

    I can't see why client_id should be random or non-meaningful at the moment, if there's a reason for that, please report an issue, some automatic migration to hashes can probably be deployed at any time.

  • oauth2app is not on PyPI at the moment, but pip can install it from github directly.

WebDAV

  • CSRF middleware (django.middleware.csrf.CsrfViewMiddleware) must be disabled, because remoteStorage.js doesn't pass django csrf tokens along with PUT (and similar) requests. It's selectively enabled via decorator for app forms though.

  • Data is currently stored in the Django Storage, while path metadata is stored through the Django Database API, which introduces two points of failure (and the possibility of sync loss between the two), because one data is useless without the other.

    There don't seem to be any easy way around it - storing path data in Storage keys won't work with any driver, pushing that to the content won't work when this content will be served by anything but python (say, httpd) and storing files in a db only works well for relatively small files.

    So make sure to backup db as well as the actual storage, or write some storage-specific kludge to store metadata there as well. Example would be to add a hook to post-save django signal, which would get storage path from StorageObject.data.name and store some "{name}.meta" file alongside with serialized model data.

TODO

  • Client (app, requesting access) deception - returning fake "authorized scopes" to it, but storing them somewhere to deny the actual access or provide random garbage instead.

    Idea is to prevent situation, common on twitter and android platforms, when apps always ask for everything and user is presented with "all or nothing" choice.

  • Add ability to inspect stored/accessed resources to the client management interface.

Contacts / Support

Feel free to drop by to #unhosted or #remotestorage channels on freenode IRC, you can always find authors and people (developers included) willing to help understand, setup and resolve any issues there.

Mailing lists, twitter and other channels of indirect communication can also be found on Unhosted movement site.

And of course, open Issues for github repository.

 
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