Trusted host middleware in FastAPI - Mini Project: Build & Apply

Trusted Host Middleware in FastAPI

📖 Scenario: You are building a simple web API using FastAPI. To keep your API safe, you want to allow requests only from certain trusted hosts, like your own domain and localhost.

🎯 Goal: Build a FastAPI app that uses the TrustedHostMiddleware to accept requests only from example.com and localhost.

📋 What You'll Learn

Create a FastAPI app instance

Add TrustedHostMiddleware with allowed hosts example.com and localhost

Create a simple root endpoint that returns a welcome message

Run the app so it enforces trusted hosts

💡 Why This Matters

🌍 Real World

TrustedHostMiddleware helps protect your API by allowing requests only from known, safe domains. This prevents some types of attacks and misuse.

💼 Career

Understanding middleware and security features like trusted hosts is important for backend developers building secure web APIs.

1

Create a FastAPI app instance

Import FastAPI from fastapi and create an app instance called app.

FastAPI

# Import FastAPI and create app instance
# Your code here

Need a hint?

Use from fastapi import FastAPI and then app = FastAPI().

2

Add TrustedHostMiddleware with allowed hosts

Import TrustedHostMiddleware from fastapi.middleware.trustedhost and add it to app with allowed_hosts set to ["example.com", "localhost"].

FastAPI

from fastapi import FastAPI

app = FastAPI()
# Add TrustedHostMiddleware with allowed_hosts ["example.com", "localhost"]
# Your code here

Need a hint?

Use app.add_middleware(TrustedHostMiddleware, allowed_hosts=["example.com", "localhost"]).

3

Create a root endpoint

Define a GET endpoint at "/" on app that returns a JSON message {"message": "Welcome to the trusted host API!"}.

FastAPI

from fastapi import FastAPI
from fastapi.middleware.trustedhost import TrustedHostMiddleware

app = FastAPI()

app.add_middleware(TrustedHostMiddleware, allowed_hosts=["example.com", "localhost"])

# Create a GET endpoint at "/" returning JSON message
# Your code here

Need a hint?

Use @app.get("/") decorator and define an async function root that returns the message.

4

Run the FastAPI app

Add the code to run the app with uvicorn when the script is executed directly. Use uvicorn.run(app, host="0.0.0.0", port=8000) inside if __name__ == "__main__".

FastAPI

from fastapi import FastAPI
from fastapi.middleware.trustedhost import TrustedHostMiddleware
import uvicorn

app = FastAPI()

app.add_middleware(TrustedHostMiddleware, allowed_hosts=["example.com", "localhost"])

@app.get("/")
async def root():
    return {"message": "Welcome to the trusted host API!"}

# Add code to run app with uvicorn when executed directly
# Your code here

Need a hint?

Import uvicorn and use if __name__ == "__main__" to run the app.