zwila-azure-storage

Synopsis

npm package to use a single container of an Azure Storage Account (ASA) as backend for anonymous (but targeted and restricted) file distribution.

Data structure in container

• Top level "folders": blob name prefix, string up to first "/" char, aka slug
  • "Cryptographic" autonaming of folders with nanoid -> hard to guess folder names.
• Each folder may contain a number of blobs.

Access control

• The package helps building a proxy webservice that implements access control on the folder level.
  • The ASA container does not need to allow public anonymous access.
  • The package authenticates to the ASA with an access key.
• On download requests, the proxy generates a short-lived Shared Access Signature (SAS) URL and give it to the anonymous client, which downloads the blob straight from the ASA, without authentication.
• Folders expire after a number of days (default 31), proxy stops giving access.

Typical use case - hidden download page on your website

• Use the package to create a folder in the ASA container. Upload files to the folder. Note the generated slug, eg "V1StGXR8_Z5jdHi6B-myT".
• Have an empty "one-way file transfer" landing page on your website that takes a link ending in a slug, eg https://example.com/transit/V1StGXR8_Z5jdHi6B-myT
• Use the proxy and package to check if the link is valid and the folder is non-expired, and to list the corresponding files on the landing page. Otherwise leave page empty, or show a message.
• Distribute the link to persons that shall have anonymous time-limited access to the files within that folder.
• Persons see the downloads on the landing page, as if stored on your website. On click, they download from Azure.

Usage, API

Todo. For now, study and run the unit tests to see how it works.

Run unit tests

To run the tests in the test/ava directory

1. Have an Azure Storage Account, and create a container.
2. Create an .env file in the package root, with these 3 vars:

var	for
ZWILA_STORAGEACCOUNT	ASA name
ZWILA_ACCESSKEY	ASA access key
ZWILA_CONTAINER	name of container for our tests

3. Run yarn test in the package root.