# Dockerized Signal Messenger REST API

This project creates a small dockerized REST API around [signal-cli](https://github.com/AsamK/signal-cli).

At the moment, the following functionality is exposed via REST:

- Register a number
- Verify the number using the code received via SMS
- Send message (+ attachments) to multiple recipients (or a group)
- Receive messages
- Link devices
- Create/List/Remove groups
- List/Serve/Delete attachments
- Update profile

and [many more](https://bbernhard.github.io/signal-cli-rest-api/)


## Getting started

1. Create a directory for the configuration
This allows you to update `signal-cli-rest-api` by just deleting and recreating the container without the need to re-register your signal number

```bash
$ mkdir $HOME/.local/share/signal-cli
```


2. Start a container

```bash
$ sudo docker run -d --name signal-api --restart=always -p 8080:8080 \
      -v $HOME/.local/share/signal-cli:/home/.local/share/signal-cli \
      -e 'MODE=native' bbernhard/signal-cli-rest-api
```

3. Register or Link you Signal Number

In this case we'll register our container as secondary device, assuming that you already have your primary number running / assigned to your mobile. 

Therefore open http://localhost:8080/v1/qrcodelink?device_name=signal-api in your browser, open Signal on your mobile phone, Go to _Settings > Linked devices_ and scan the QR code using the _+_ button.

4. Test your new REST API

Call the REST api endpoint and send a test message: Replace `+4412345` with your signal number in international number format, and `+44987654` with the recipients number

```bash
$ curl -X POST -H "Content-Type: application/json" 'http://localhost:8080/v2/send' \
     -d '{"message": "Test via Signal API!", "number": "+4412345", "recipients": [ "+44987654" ]}' 
```

You should now have send a message to `+44987654`.

## Execution Modes 

The `signal-cli-rest-api` supports three different modes of execution, which can be controlled by setting the `MODE` environment variable.

* **`normal` Mode: (Default)** The `signal-cli` executable is invoked for every REST API request. Being a Java application, each REST call requires a new startup of the JVM (Java Virtual Machine), increasing the latency and hence leading to the slowest mode of operation. 
* **`native` Mode:** A precompiled binary `signal-cli-native` (using GraalVM) is used for every REST API request. This results in a much lower latency & memory usage on each call. On the `armv7` platform this mode is not available and falls back to `normal`. The native mode may also be less stable, due to the experimental state of GraalVM compiler. 
* `json-rpc` Mode: A single, JVM-based `signal-cli` instance is spawned as daemon process. This mode is usually the fastest, but requires more memory as the JVM keeps running. 


|     mode     |    speed    |    resident memory usage |
|-------------:|:------------|:------------|
|   `normal`    |    :heavy_check_mark:       | normal
|   `native`    |    :heavy_check_mark: :heavy_check_mark:    | normal
|   `json-rpc`  |    :heavy_check_mark: :heavy_check_mark: :heavy_check_mark: | increased


**Example of running `signal-cli-rest` in `native` mode**

```bash
$ sudo docker run -d --name signal-api --restart=always -p 9922:8080 \
              -v /home/user/signal-api:/home/.local/share/signal-cli \
              -e 'MODE=native' bbernhard/signal-cli-rest-api
```

This launches a instance of the REST service accessible under http://localhost:9922/v2/send. To preserve the Signal number registration, i.e. for updates, the storage location for the `signal-cli` configuration is mapped as Docker Volume into a local `/home/user/signal-api` directory.


## Auto Receive Schedule

> :warning: This setting is only needed in normal/native mode!

[signal-cli](https://github.com/AsamK/signal-cli), which this REST API wrapper is based on, recommends to call `receive` on a regular basis. So, if you are not already calling the `receive` endpoint regularily, it is recommended to set the `AUTO_RECEIVE_SCHEDULE` parameter in the docker-compose.yml file. The `AUTO_RECEIVE_SCHEDULE` accepts cron schedule expressions and automatically calls the `receive` endpoint at the given time. e.g: `0 22 * * *` calls `receive` daily at 10pm. If you are not familiar with cron schedule expressions, you can use this [website](https://crontab.guru).

**WARNING** Calling `receive` will fetch all the messages for the registered Signal number from the Signal Server! So, if you are using the REST API for receiving messages, it's _not_ a good idea to use the `AUTO_RECEIVE_SCHEDULE` parameter, as you might lose some messages that way.

## Example

Sample `docker-compose.yml`file:

```yaml
version: "3"
services:
  signal-cli-rest-api:
    image: bbernhard/signal-cli-rest-api:latest
    environment:
      - MODE=normal #supported modes: json-rpc, native, normal
      #- AUTO_RECEIVE_SCHEDULE=0 22 * * * #enable this parameter on demand (see description below)
    ports:
      - "8080:8080" #map docker port 8080 to host port 8080.
    volumes:
      - "./signal-cli-config:/home/.local/share/signal-cli" #map "signal-cli-config" folder on host system into docker container. the folder contains the password and cryptographic keys when a new number is registered
```

## Documentation

### API Reference

The Swagger API documentation can be found [here](https://bbernhard.github.io/signal-cli-rest-api/). If you prefer a simple text file based API documentation have a look [here](https://github.com/bbernhard/signal-cli-rest-api/blob/master/doc/EXAMPLES.md).

### Blog Posts

[Running Signal Messenger REST API in Azure Web App for Containers](https://stefanstranger.github.io/2021/06/01/RunningSignalRESTAPIinAppService/) by [@stefanstranger](https://github.com/stefanstranger)


## Clients & Libraries

|     Name    | Client           | Library  | Language | Maintainer |
| ------------- |:-------------:| :-----:|:-----:|:-----:|
| [Shell Client](https://github.com/florian-h05/shell-script_collection/blob/main/signal-cli-rest-api_client.bash)      | X | | Shell | [@florian-h05](https://github.com/florian-h05)
| [pysignalclirestapi](https://pypi.org/project/pysignalclirestapi/)      | | X | Python | [@bbernhard](https://github.com/bbernhard)
| [signalbot](https://pypi.org/project/signalbot/) | | X | Python | [@filipre](https://github.com/filipre)

In case you need more functionality, please **file a ticket** or **create a PR**.