I was researching password hashing for datasette-auth-passwords. I wanted very secure defaults that would work using the Python standard library without any extra dependencies.
I ended up following Django's example and implementing pbkdf2_sha256 with 260,000 iterations. Here's my version of the way Django does this - I chose to use the same hashed password format (algorithm$iterations$salt$hash) in case I wanted to change the hashing algorithm used in the future.
import base64
import hashlib
import secrets
ALGORITHM = "pbkdf2_sha256"
def hash_password(password, salt=None, iterations=260000):
if salt is None:
salt = secrets.token_hex(16)
assert salt and isinstance(salt, str) and "$" not in salt
assert isinstance(password, str)
pw_hash = hashlib.pbkdf2_hmac(
"sha256", password.encode("utf-8"), salt.encode("utf-8"), iterations
)
b64_hash = base64.b64encode(pw_hash).decode("ascii").strip()
return "{}${}${}${}".format(ALGORITHM, iterations, salt, b64_hash)
def verify_password(password, password_hash):
if (password_hash or "").count("$") != 3:
return False
algorithm, iterations, salt, b64_hash = password_hash.split("$", 3)
iterations = int(iterations)
assert algorithm == ALGORITHM
compare_hash = hash_password(password, salt, iterations)
return secrets.compare_digest(password_hash, compare_hash)Created 2020-07-13T20:53:56-07:00, updated 2020-07-13T20:54:40-07:00 · History · Edit