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"""Simple module to generate PKCE code verifier and code challenge.
Examples
--------
>>> import pkce
>>> code_verifier, code_challenge = pkce.generate_pkce_pair()
>>> import pkce
>>> code_verifier = pkce.generate_code_verifier(length=128)
>>> code_challenge = pkce.get_code_challenge(code_verifier)
"""
import secrets
import hashlib
import base64
from typing import Tuple
def generate_code_verifier(length: int = 128) -> str:
"""Return a random PKCE-compliant code verifier.
Parameters
----------
length : int
Code verifier length. Must verify `43 <= length <= 128`.
Returns
-------
code_verifier : str
Code verifier.
Raises
------
ValueError
When `43 <= length <= 128` is not verified.
"""
if not 43 <= length <= 128:
msg = 'Parameter `length` must verify `43 <= length <= 128`.'
raise ValueError(msg)
code_verifier = secrets.token_urlsafe(96)[:length]
return code_verifier
def generate_pkce_pair(code_verifier_length: int = 128) -> Tuple[str, str]:
"""Return random PKCE-compliant code verifier and code challenge.
Parameters
----------
code_verifier_length : int
Code verifier length. Must verify
`43 <= code_verifier_length <= 128`.
Returns
-------
code_verifier : str
code_challenge : str
Raises
------
ValueError
When `43 <= code_verifier_length <= 128` is not verified.
"""
if not 43 <= code_verifier_length <= 128:
msg = 'Parameter `code_verifier_length` must verify '
msg += '`43 <= code_verifier_length <= 128`.'
raise ValueError(msg)
code_verifier = generate_code_verifier(code_verifier_length)
code_challenge = get_code_challenge(code_verifier)
return code_verifier, code_challenge
def get_code_challenge(code_verifier: str) -> str:
"""Return the PKCE-compliant code challenge for a given verifier.
Parameters
----------
code_verifier : str
Code verifier. Must verify `43 <= len(code_verifier) <= 128`.
Returns
-------
code_challenge : str
Code challenge that corresponds to the input code verifier.
Raises
------
ValueError
When `43 <= len(code_verifier) <= 128` is not verified.
"""
if not 43 <= len(code_verifier) <= 128:
msg = 'Parameter `code_verifier` must verify '
msg += '`43 <= len(code_verifier) <= 128`.'
raise ValueError(msg)
hashed = hashlib.sha256(code_verifier.encode('ascii')).digest()
encoded = base64.urlsafe_b64encode(hashed)
code_challenge = encoded.decode('ascii')[:-1]
return code_challenge
|
