karldreher / b2-cloudflare-worker

A cloudflare worker which is used to cache content from a private Backblaze B2 bucket.

b2-cloudflare-worker

The purpose of this project is to provide a Cloudflare worker which reads from a private Backblaze B2 bucket, to provide an easy way to utilize Cloudflare as a CDN for any kind of static content.

The service is deployed as a Cloudflare Worker and uses environment variables for parameters.

Running the development server

Requires Wrangler.

wrangler dev

See note about Environment Variables in Development Environment below.

Environment Variables

The application expects to receive environment variables from Cloudflare to set the environment. The variables are described below.

Name	Description	Example Value
AUTH_HEADER	This is a user:password pair, base64 encoded. The word "Basic" and a space must prepend the entry. See below for instructions on getting this value.	Basic dXNlcm5hbWU6cGFzc3dvcmQK
BUCKET_NAME	The name of the bucket in Backblaze B2.	my-cool-bucket
CACHE_CONTROL	The time that cache should be valid for the files in the bucket. This affects both the B2 cache as well as Cloudflare. It is reccomended to set this within wrangler.toml.	"public,max-age=172800"

See more details about setting these values in a production deployment in Deployment.

Environment Variables in Development Environment

When using variables in conjunction with wrangler dev, they must be set according to the following.

[vars]
BUCKET_NAME = "my-cool-bucket"
CACHE_CONTROL = "public,max-age=172800" #This should be here anyway, it is included for completeness.

While developing locally, it is appropriate to set AUTH_HEADER as an environment variable, which will be passed to wrangler appropriately using predev script in package.json. Example:

export AUTH_HEADER="BASIC dXNlcm5hbWU6cGFzc3dvcmQK"
npm run dev

Deployment

Cloudflare - Prereqs

You will need a CLOUDFLARE_API_TOKEN set as an environment variable. It is recommended to use the "Edit Workers" template for this token, when setting it up.

B2 - Generating the authorization value

1. Within Backblaze, add an application key for your bucket.
2. Select the appropriate bucket (not "All" unless you know what you're doing)
3. Select "Read Only"
4. Provide a duration less than 1000 days in the future, specified in seconds. Since this will need to rotate, it is reccomended (for this application's purpose) a maximum value of 86400000. (As of this writing it is possible to create a application key without expiration)

Upon creating the app key, use the values for keyID and applicationKey by Backblaze to generate the base-64 encoded Basic authorization header:

$ AUTH=$(echo keyID:applicationKey | base64)
$ VALUE="Basic $AUTH"
$ echo $VALUE
Basic dXNlcm5hbWU6cGFzc3dvcmQK

Use the contents of $VALUE (including "Basic ") as generated following the steps above, within the environment variable AUTH_HEADER. This can be done through the Cloudflare console or using wrangler:

wrangler secret put AUTH_HEADER

Both the username:password pair and authorization value should be treated as a secret. Within Backblaze it is not possible to change or view the keys after creation, they must be regenerated as new keys!

Setting the bucket name

The bucket name of the B2 bucket needs to be expressed with the environment variable BUCKET_NAME. This can be done through the Cloudflare console or using wrangler:

wrangler secret put BUCKET_NAME

If the bucket name is not considered secret (or if your deployment is appropriately protected) you can put this in your wrangler.toml:

[vars]
BUCKET_NAME = "my-cool-bucket"

Cache-control

The environment variable CACHE_CONTROL must be in your wrangler.toml:

[vars]
CACHE_CONTROL = "public,max-age=172800"

max-age can be a fairly high value if your content does not change often. The value is in seconds.

Deploying the worker

wrangler publish

Usage

Utilize the worker's endpoint to access your files in your private bucket! This can be done in the browser, through a shell program, or anything that uses HTTPS. The worker handles the middleware between your browser, the Cloudflare cache, and the B2 bucket.

curl my-secret-bucket.example.workers.dev/pictures-of-cats/fatkitty.jpg

Testing

See TESTING.MD.