JWT token verification in FastAPI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to decode a JWT token using the secret key.

FastAPI

from jose import jwt

def verify_token(token: str, secret_key: str):
    payload = jwt.[1](token, secret_key, algorithms=["HS256"])
    return payload

Drag options to blanks, or click blank then click option'

Averify

Bencode

Cdecode

Dsign

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'encode' instead of 'decode' will cause an error because encoding creates tokens, not verifies them.

Using 'sign' or 'verify' are not valid methods in the jose.jwt module.

The jwt.decode function is used to decode and verify the JWT token using the secret key.

2fill in blank

medium

Complete the code to raise an exception if the token is invalid.

FastAPI

from jose import JWTError

def verify_token(token: str, secret_key: str):
    try:
        payload = jwt.decode(token, secret_key, algorithms=["HS256"])
    except [1]:
        raise ValueError("Invalid token")
    return payload

Drag options to blanks, or click blank then click option'

ATypeError

BValueError

CKeyError

DJWTError

Attempts:

3 left

💡 Hint

Common Mistakes

Catching ValueError will not catch JWT decode errors specifically.

KeyError and TypeError are unrelated to JWT token verification.

The JWTError exception is raised by the jwt.decode function when the token is invalid or expired.

3fill in blank

hard

Fix the error in the code to correctly extract the user ID from the token payload.

FastAPI

def get_user_id(token: str, secret_key: str):
    payload = jwt.decode(token, secret_key, algorithms=["HS256"])
    user_id = payload.get([1])
    if user_id is None:
        raise ValueError("User ID not found in token")
    return user_id

Drag options to blanks, or click blank then click option'

A"sub"

B"user"

C"id"

D"uid"

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'user', 'id', or 'uid' keys may not match the token payload structure.

Not checking if the user ID exists can cause errors later.

The standard JWT claim for the subject (user identifier) is "sub". This key holds the user ID in the token payload.

4fill in blank

hard

Fill both blanks to create a FastAPI dependency that verifies the JWT token from the Authorization header.

FastAPI

from fastapi import Depends, HTTPException, status
from fastapi.security import OAuth2PasswordBearer

oauth2_scheme = OAuth2PasswordBearer(tokenUrl="token")

def get_current_user(token: str = Depends([1])):
    try:
        payload = jwt.decode(token, [2], algorithms=["HS256"])
    except JWTError:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Could not validate credentials",
            headers={"WWW-Authenticate": "Bearer"},
        )
    return payload

Drag options to blanks, or click blank then click option'

Aoauth2_scheme

BDepends

C"secret"

Dsecret_key

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Depends' instead of the OAuth2 scheme instance will cause errors.

Using a string 'secret' instead of the secret_key variable will fail token decoding.

The oauth2_scheme dependency extracts the token from the Authorization header. The secret_key is used to decode the token.

5fill in blank

hard

Fill all three blanks to create a function that verifies the JWT token and returns the user email if valid.

FastAPI

def get_user_email(token: str, secret_key: str):
    try:
        payload = jwt.decode(token, [1], algorithms=["HS256"])
        email = payload.get([2])
        if email is None:
            raise ValueError("Email not found in token")
    except JWTError:
        raise ValueError("Invalid token")
    return [3]

Drag options to blanks, or click blank then click option'

Asecret_key

B"email"

Cemail

D"sub"

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong keys like 'sub' instead of 'email' will cause missing data.

Returning the wrong variable or string instead of the email variable.

The function uses secret_key to decode the token, looks for the "email" key in the payload, and returns the email variable.