Password hashing with bcrypt in FastAPI - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this FastAPI bcrypt password hashing snippet?

Consider this FastAPI endpoint that hashes a password using bcrypt. What will be the type of the returned hashed password?

FastAPI

from fastapi import FastAPI
from passlib.context import CryptContext

app = FastAPI()
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

@app.post("/hash")
async def hash_password(password: str):
    hashed = pwd_context.hash(password)
    return {"hashed_password": hashed}

A A string containing the hashed password

B A bytes object representing the hashed password

C A dictionary with salt and hash keys

D An integer representing the hash value

💡 Hint

Think about what type the passlib CryptContext.hash method returns.

The pwd_context.hash method returns a string that contains the hashed password including the salt and algorithm info. It is not bytes or a dictionary.

📝 Syntax

intermediate

Which option correctly verifies a password against a bcrypt hash in FastAPI?

Given a stored bcrypt hash and a plain password, which code snippet correctly verifies if the password matches the hash?

FastAPI

from passlib.context import CryptContext
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

stored_hash = "$2b$12$KIXQJ7Q1Y6b6xQ9v1zQO6u5v1Q0xQ0xQ0xQ0xQ0xQ0xQ0xQ0xQ0xQ"
password = "mysecret"

A pwd_context.verify(password, stored_hash)

B pwd_context.hash(password) == stored_hash

C bcrypt.checkpw(password, stored_hash)

D pwd_context.check(password, stored_hash)

💡 Hint

Look for the method designed to verify passwords in passlib CryptContext.

The verify method of CryptContext checks if the plain password matches the stored hash securely. Option A compares strings incorrectly. Option A is invalid because bcrypt.checkpw expects bytes, not strings. Option A is not a valid method.

🔧 Debug

advanced

Why does this FastAPI bcrypt password verification raise a TypeError?

This code snippet raises a TypeError when verifying a password. What is the cause?

FastAPI

from passlib.context import CryptContext
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

stored_hash = b"$2b$12$KIXQJ7Q1Y6b6xQ9v1zQO6u5v1Q0xQ0xQ0xQ0xQ0xQ0xQ0xQ0xQ0xQ"
password = "mysecret"

result = pwd_context.verify(password, stored_hash)

A password must be bytes, not string

B stored_hash is bytes but should be a string

C CryptContext does not support bcrypt scheme

D verify method requires async keyword

💡 Hint

Check the data types of the arguments passed to verify.

The verify method expects both password and hash as strings. Passing bytes as stored_hash causes a TypeError.

❓ state_output

advanced

What is the value of 'is_valid' after running this FastAPI bcrypt verification code?

Given the following code, what will be the value of the variable 'is_valid'?

FastAPI

from passlib.context import CryptContext
pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")

password = "secret123"
hash1 = pwd_context.hash(password)
hash2 = pwd_context.hash(password)
is_valid = pwd_context.verify(password, hash1) and (hash1 != hash2)

A Raises a runtime error

B False

C None

D True

💡 Hint

Consider if hashing the same password twice produces the same hash and if verify checks correctly.

Hashing the same password twice produces different hashes due to random salt. verify returns True for the correct password. So is_valid is True.

🧠 Conceptual

expert

Which statement best explains why bcrypt hashes differ each time even for the same password?

Why does hashing the same password multiple times with bcrypt produce different hash strings each time?

A Because bcrypt uses a different hashing algorithm each time

B Because bcrypt hashes the password with a timestamp included

C Because bcrypt uses a random salt each time to protect against rainbow table attacks

D Because bcrypt truncates the password differently each time

💡 Hint

Think about what makes password hashes unique and secure.

Bcrypt generates a new random salt for each hash to ensure that identical passwords have different hashes, improving security.