RelaySMS Publisher

Publishes to online platforms, such as Gmail, from content people send by SMS, so they can post without an internet connection.

How it works

---
config:
  flowchart:
    curve: linear
---
flowchart TB
    app["RelaySMS app"]
    gateway["Gateway client"]
    mailbox["Mailbox"]
    platform["Online platforms"]

    subgraph publisher["Publisher"]
        grpc["gRPC API"]
        rest["REST API"]
        smtp["Email listener"]
        db[("Database")]
        worker["Celery worker"]
        adapter["Platform adapter"]
        %% Keeps the title clear of the arrows entering the box.
        spacer[" "]:::hidden
        spacer ~~~ worker
    end

    app -- "link an account, online" --> grpc
    app -- "encrypted SMS" --> gateway
    gateway -- "HTTPS" --> rest
    gateway -- "email" --> mailbox
    mailbox -- "IMAP" --> smtp
    grpc -- "token, keys" --> db
    db --> worker
    rest --> worker
    smtp --> worker
    grpc --> adapter
    worker --> adapter
    adapter --> platform

    classDef hidden fill:none,stroke:none

1. While online, a user links an account through the gRPC API. The Publisher stores its token encrypted.
2. Offline, the app encrypts the content and sends it by SMS to a gateway client, a phone number that relays SMS.
3. The gateway client posts the payload to the REST API, or emails it to a mailbox the Publisher reads.
4. A Celery worker decrypts the payload and publishes it through the platform’s adapter.

Key terms

• Gateway client: a phone number that relays SMS to the Publisher, such as an Android phone running Deku SMS. See Connecting a relay.
• Adapter (platform adapter): the plugin that publishes to one platform, such as Gmail, installed from its own repository. See Managing adapters.
• Linked account: a user’s account on a platform, authorized once while online. The Publisher stores its token encrypted.
• OAuth2 and PNBA: how accounts link. OAuth2 goes through the platform’s consent page, as for Gmail. Phone number-based authentication (PNBA) uses a code sent to the user’s phone, as for Telegram. The provider guides give each platform’s protocol.
• Offline payload: content sent without a linked account, published through RelaySMS Mail. See Offline publishing.

The glossary defines the rest, and Architecture shows every component.

Where to start

Getting help

• Ask questions and report bugs in the issue tracker; CONTRIBUTING.md says what a useful report has.
• Report vulnerabilities privately, as SECURITY.md describes.