Satellite API

A lightning app (Lapp) based on c-lightning. Presents an API to submit messages for global broadcast over Blockstream Satellite and pay for them with Bitcoin Lightning payments.

Contents

• Setup
• Run
• Example Applications
• REST API
  • POST /order
  • POST /order/:uuid/bump
  • GET /order/:uuid
  • GET /order/:uuid/sent_message
  • DELETE /order/:uuid
  • GET /orders/pending
  • GET /orders/queued
  • GET /orders/sent
  • GET /info
  • GET /subscribe/:channels
• Debugging
  • Queue Page
• Future Work

Setup

The Blockstream Satellite API is dependent on lightning-charge, which itself is dependent on c-lightning and bitcoin. To bring up charged, lightningd, and bitcoind, a handy docker-compose script is available.

The satellite API itself is comprised of a RESTful API server and a transmitter daemon. The API server speaks JSON and is used for creating and managing message transmission orders and for processing lightning-charge payment callbacks. The transmitter daemon dequeues paid orders and writes the uploaded message a named pipe, where they are subsequently processed by the Blockstream Satellite GNU Radio transmitter.

Run

The included Dockerfile builds a Docker file with the necessary gem dependencies, directory structure, and permissions. The included docker_entrypoint.sh runs the API server and transmitter daemon.

After building a Docker image (satellite_api in the example below), decide where you are going to keep your persisted data (~/docker/data in the example below) and run it like this:

docker run -e CHARGE_ROOT=http://api-token:mySecretToken@localhost:9112 -e CALLBACK_URI_ROOT=http://my.public.ip:9292 -u `id -u` -v ~/docker/data:/data -p 9292:9292 -it satellite_api

To run in developer mode, set the RACK_ENV environment variable like this:

docker run -e CHARGE_ROOT=http://api-token:mySecretToken@localhost:9112 -e CALLBACK_URI_ROOT=http://my.public.ip:9292 -e RACK_ENV=development -u `id -u` -v ~/docker/data:/data -p 9292:9292 -it satellite_api

Example Applications

Example Python applications are available at the Blockstream Satellite examples directory as a reference regarding how to implement the interaction with the API. There is one application specifically for sending data to the API, called "API data sender", and another application for reading the API data acquired by the Blockstream Satellite receiver, called "API data reader". Additionally, there is one application that allows testing API data reception directly through the internet, without the actual satellite receiver hardware, called "demo receiver". Refer to the documentation in the given link.

REST API

Each call to an API endpoint responds with a JSON object, whether the call is successful or results in an error.

The code samples below assume that you've set SATELLITE_API in your shell to the public base URL of your server.

POST /order

Place an order for a message transmission. The body of the POST must provide a bid in millisatoshis and a message, provided either as a message parameter string or as an HTTP form-based file upload. If the bid is below an allowed minimum millisatoshis per byte, a BID_TOO_SMALL (102) error is returned.

For example, to place an order to transmit the message "Hello world" with an initial bid of 10,000 millisatoshi, issue an HTTP POST request like this:

curl -F "bid=10000" -F "message=Hello World" $SATELLITE_API/order

Or, to place an order to transmit the file hello_world.png with an initial bid of 10,000 millisatoshi, issue an HTTP POST request like this:

curl -F "bid=10000" -F "file=@/path/to/upload/file/hello_world.png" $SATELLITE_API/order

If successful, the response includes the JSON Lightning invoice as returned by Lightning Charge's POST /invoice and an authentication token that can be used to modify the order. Within the metadata of the Lightning invoice, metadata is included providing: the bid (in millisatoshis), the SHA256 digest of the uploaded message file, and a UUID for the order.

{"auth_token":"d784e322dad7ec2671086ce3ad94e05108f2501180d8228577fbec4115774750","uuid":"409348bc-6af0-4999-b715-4136753979df","lightning_invoice":{"id":"N0LOTYc9j0gWtQVjVW7pK","msatoshi":"514200","description":"BSS Test","rhash":"5e5c9d111bc76ce4bf9b211f12ca2d9b66b81ae9839b4e530b16cedbef653a3a","payreq":"lntb5142n1pd78922pp5tewf6ygmcakwf0umyy039j3dndntsxhfswd5u5ctzm8dhmm98gaqdqdgff4xgz5v4ehgxqzjccqp286gfgrcpvzl04sdg2f9sany7ptc5aracnd6kvr2nr0e0x5ajpmfhsjkqzw679ytqgnt6w4490jjrgcvuemz790salqyz9far68cpqtgq3q23el","expires_at":1541642146,"created_at":1541641546,"metadata":{"sha256_message_digest":"0e2bddf3bba1893b5eef660295ef12d6fc72870da539c328cf24e9e6dbb00f00","uuid":"409348bc-6af0-4999-b715-4136753979df"},"status":"unpaid"}}

Error codes that can be returned by this endpoint include: BID_TOO_SMALL (102), FILE_MISSING (103), MESSAGE_FILENAME_MISSING (116), MESSAGE_FILE_TOO_SMALL (117), MESSAGE_FILE_TOO_LARGE (118), BID_TOO_SMALL (102), MESSAGE_TOO_LONG (125), MESSAGE_MISSING (126).

POST /order/:uuid/bump

Increase the bid for an order sitting in the transmission queue. The bid_increase must be provided in the body of the POST. A Lightning invoice is returned for it and, when it is paid, the increase is added to the current bid. An auth_token must also be provided. For example, to increase the bid on the order placed above by 100,000 millisatoshis, issue a POST like this:

curl -v -F "bid_increase=100000" -F "auth_token=d784e322dad7ec2671086ce3ad94e05108f2501180d8228577fbec4115774750" $SATELLITE_API/order/409348bc-6af0-4999-b715-4136753979df/bump

Response object is in the same format as for POST /order.

As shown below for DELETE, the auth_token may alternatively be provided using the X-Auth-Token HTTP header.

Error codes that can be returned by this endpoint include: INVALID_AUTH_TOKEN (109), ORDER_NOT_FOUND (104), BID_INCREASE_MISSING (105), ORDER_BUMP_ERROR (119).

GET /order/:uuid

Retrieve an order by UUID. Must provide the corresponding auth token to prove that it is yours.

curl -v -H "X-Auth-Token: 5248b13a722cd9b2e17ed3a2da8f7ac6bd9a8fe7130357615e074596e3d5872f" $SATELLITE_API/order/409348bc-6af0-4999-b715-4136753979df

Error codes that can be returned by this endpoint include: INVALID_AUTH_TOKEN (109), ORDER_NOT_FOUND (104).

DELETE /order/:uuid

To cancel an order, issue an HTTP DELETE request to the API endpoint /order/:uuid/ providing the UUID of the order. An auth_token must also be provided. For example, to cancel the order above, issue a request like this:

curl -v -X DELETE -F "auth_token=5248b13a722cd9b2e17ed3a2da8f7ac6bd9a8fe7130357615e074596e3d5872f" $SATELLITE_API/order/409348bc-6af0-4999-b715-4136753979df

The auth_token may be provided as a parameter in the DELETE body as above or may be provided using the X-Auth-Token HTTP header, like this:

curl -v -X DELETE -H "X-Auth-Token: 5248b13a722cd9b2e17ed3a2da8f7ac6bd9a8fe7130357615e074596e3d5872f" $SATELLITE_API/order/409348bc-6af0-4999-b715-4136753979df

Error codes that can be returned by this endpoint include: INVALID_AUTH_TOKEN (109), ORDER_NOT_FOUND (104), ORDER_CANCELLATION_ERROR (120).

GET /orders/pending

Retrieve a list of 20 orders awaiting payment ordered by creation time. For pagination, optionally specify a before parameter (in ISO 8601 format) that specifies that the 20 orders immediately prior to the given time be returned.

curl $SATELLITE_API/orders/pending

curl $SATELLITE_API/orders/pending?before=2019-01-16T18:13:46-08:00

The response is a JSON array of records (one for each queued message). The revealed fields for each record include: uuid, bid, bid_per_byte, message_size, message_digest, status, created_at, started_transmission_at, and ended_transmission_at.

Error codes that can be returned by this endpoint include: INVALID_DATE (113).

GET /orders/queued

Retrieve a list of paid, but unsent orders in descending order of bid-per-byte. Both pending orders and the order currently being transmitted are returned. Optionally, accepts a parameter specifying how many queued order to return.

curl $SATELLITE_API/orders/queued

curl $SATELLITE_API/orders/queued?limit=18

The response is a JSON array of records (one for each queued message). The revealed fields for each record include: uuid, bid, bid_per_byte, message_size, message_digest, status, created_at, started_transmission_at, and ended_transmission_at.

Error codes that can be returned by this endpoint include: LIMIT_TOO_LARGE (101).

GET /orders/sent

Retrieves a list of up to 20 sent orders in reverse chronological order. For pagination, optionally specify a before parameter (in ISO 8601 format) that specifies that the 20 orders immediately prior to the given time be returned.

curl $SATELLITE_API/orders/sent

curl $SATELLITE_API/orders/sent?before=2019-01-16T18:13:46-08:00

The response is a JSON array of records (one for each queued message). The revealed fields for each record include: uuid, bid, bid_per_byte, message_size, message_digest, status, created_at, started_transmission_at, and ended_transmission_at.

Error codes that can be returned by this endpoint include: INVALID_DATE (113).

GET /info

Returns information about the c-lightning node where satellite API payments are terminated. The response is a JSON object consisting of the node ID, port, IP addresses, and other information useful for opening payment channels. For example:

{"id":"032c6ba19a2141c5fee6ac8b6ff6cf24456fd4e8e206716a39af3300876c3a4835","port":42259,"address":[],"version":"v0.5.2-2016-11-21-1937-ge97ee3d","blockheight":434,"network":"regtest"}

GET /subscribe/:channels

Subscribe to one or more server-side events channels. The channels parameter is a comma-separated list of event channels. Currently, only one channel is available: transmissions, to which an event is pushed each time a message transmission begins and ends. Event data includes a JSON representation of the order, including its current status.

curl $SATELLITE_API/subscribe/:channels

Error codes that can be returned by this endpoint include: CHANNELS_EQUALITY (124).

Debugging

Queue Page

For debugging and as an example of how to build a web front-end to the satellite API, there is a simple table view of queued, pending, and sent messages at $SATELLITE_API/queue.html

Future Work

• Configure Rack::Attack or similar to block and throttle abusive requests.
• Support bids priced in fiat currencies.
• Report the top bid_per_byte, queue depth, and estimated time to transmit in the response to POST /order.