Secrets Live Outside the Code

Until now, the shop's secrets were written in its code, like the admin's password. But code travels: to the whole team, into old copies, onto GitHub. A secret that everyone who reads the code knows is no secret.

Secrets belong in environment variables: values the server gives the program when it starts, outside the code. In Java, System.getenv() is a map of them. Read one with getOrDefault and a default for when it isn't set:

String dbFile = System.getenv().getOrDefault("DB_FILE", "shop.db");

For a secret, the default must be safe: a random value from randomHex(16) that nobody can know. If a server forgets to set the admin's password, nobody can log in as admin, which is much safer than everyone who has seen the code being able to. Settings that aren't secret but change from place to place, like the address of the shop's website, come from the environment too.

The grader starts the shop with ADMIN_PASSWORD set to env-admin-pass-456 and SHOP_SITE set to https://shop.example.com. Your code must answer:

POST /login  {"email": "admin@example.com", "password": "admin-pass-123"}      →  401  {"error": "Wrong email or password"}
POST /login  {"email": "admin@example.com", "password": "env-admin-pass-456"}  →  200  {"token": "<admin>"}
GET /me  (the session cookie from that login)  →  200  {"email": "admin@example.com", "id": 1, "role": "admin"}
POST /products  {"name": "Desk", "price": 120}  (admin's token)  →  201  {"id": 9, "name": "Desk", "price": 120}
GET /products/1  Origin: https://shop.example.com  →  200, Access-Control-Allow-Origin: https://shop.example.com
GET /products/1  Origin: http://localhost:3000     →  200, no Access-Control-Allow-Origin

Your task: read ADMIN_PASSWORD from the environment variable ADMIN_PASSWORD, with randomHex(16) as its default, and SHOP_SITE from SHOP_SITE, with "http://localhost:3000" as its default. ADMIN_PASSWORD drops static, because its default calls the controller's own randomHex; SHOP_SITE stays static, because CorsFilter reads it as ShopController.SHOP_SITE.

Assignment
Follow the Coding Tutorial to read the admin's password and the shop's website from the environment.

Hint
Each value is one System.getenv().getOrDefault(name, default). The default is what the program uses on your computer and in tests, where nothing is set, so for a secret it must be something nobody can guess.