Over-The-Air (OTA) Server

OTA Server is a simple server that allows users to install iOS apps (beta) directly on devices running the iOS operating system.

Introduction

The OTA Server has a built-in Notification system, if any build is created, it will send a notification to a channel, a group on Telegram. This is very useful when integrating OTA Sever into CI/CD.

I use GCS (Google Cloud Storage) to store builds, using GCS ensures that builds are always available. Every time there is a download request, the OTA Server will open a connection directly from GCS to the client, instead of downloading from GCS and then sending it to the client. This will reduce the download time on the client side.

OTA Server has a pretty simple architecture, the frontend is written in ReactJS and the backend is written in Go. I have combined frontend and backend in the same container (docker).

Authentication

The OTA Server has a built-in authentication system. It simply uses JWT (Json Web Token) to authenticate the user.

But one point to note is that the OTA installation method for iOS uses the itms-services protocol to download the configuration file (.plist).

Basically, the itms-services protocol cannot understand JWT, so a simpler authentication mechanism is needed. The OTA Server will generate 1 code to exchange with client side (exchange_code).

The Exchange Code will be generated when the user logged-in the system, and it has the same effect as the Access Token.

There are 2 APIs that use Exchange Code authentication: the API to download the configuration file, and the API to download the uploaded files.

Environments

Below are the environment variables that OTA Server uses.

# MySQL config variables
DB_USERNAME=db_username
DB_PASSWORD=db_password
DB_HOST=db_ip_address
DB_PORT=db_port
DB_INSTANCE=db_instance
AUTO_MIGRATE=1 # 1 = auto migrate when startup, on production it should be 0 or remove

# redis config variables
REDIS_ADDR=localhost:6379
REDIS_PASSWORD=password
REDIS_DB=0

# storage config variables
GOOGLE_CREDENTIALS=/path/to/credentials.json # i'm using google cloud storage to storage .ipa or apk
GCS_BUCKET=bucket-name # bucket name

# server config variables 
PORT=8081
HOST=example.com # the application's host
STATIC_PATH=/path/to/spa/build/folder
SECRET=your-secret

# notification config variables
TELEGRAM_BOT_TOKEN=your_telegram_bot_token # use @BotFather to create new bot and get token
TELEGRAM_GROUP_ID=your_group_id # https://stackoverflow.com/questions/33858927/how-to-obtain-the-chat-id-of-a-private-telegram-channel

Usage

There are several ways to start the OTA Server

Binary

As mentioned above, the OTA Server is written by both ReactJS (UI) and Golang, so all you need to do is build the UI first.

cd web && yarn install && yarn build && cd -

Make sure that the environment variables listed above have been exported to the environment.

go mod download && go build -o app . && ./app

Docker

To make the execute command shorter I usually prepare a file containing the environment variables inside.

docker build . -t ota-server && \ 
docker run -p 8080:8080 --env-file .env \ 
  -v /path/to/credentials.json:/credential.json:ro \
  ota-server

Docker-compose

If you use docker-compose then DB_HOST should be the name of the database service (database), the same goes for REDIS_ADDR (redis).

version: "3"
services:
  server:
    build: .
    env_file:
      - .env
    ports:
    - 8080:8080
    volumes:
    - /path/to/credentials.json:/credentials.json
  database:
    image: mysql:5.7
    ports:
      - 3306:3306
    volumes:
    - .data:/var/lib/mysql
    environment:
      MYSQL_ROOT_PASSWORD: root_password 
      MYSQL_DATABASE: ota
      MYSQL_USER: ota
      MYSQL_PASSWORD: user_password
  redis:
    image: redis:6.2-alpine
    ports:
      - 6379:6379

TODO

• Apply auth (Google)
• Download IPA from GCS as a stream
• Build docker
• Integrate GitHub Actions
• Telegram Notification
• Built-in Authentication
• Resume download