_pkce.py 文件源码

def code_verifier(n_bytes=64):
    """
    Generates a 'code_verifier' as described in section 4.1 of RFC 7636.

    This is a 'high-entropy cryptographic random string' that will be
    impractical for an attacker to guess.

    Args:
        n_bytes: integer between 31 and 96, inclusive. default: 64
            number of bytes of entropy to include in verifier.

    Returns:
        Bytestring, representing urlsafe base64-encoded random data.
    """
    verifier = base64.urlsafe_b64encode(os.urandom(n_bytes)).rstrip(b'=')
    # https://tools.ietf.org/html/rfc7636#section-4.1
    # minimum length of 43 characters and a maximum length of 128 characters.
    if len(verifier) < 43:
        raise ValueError("Verifier too short. n_bytes must be > 30.")
    elif len(verifier) > 128:
        raise ValueError("Verifier too long. n_bytes must be < 97.")
    else:
        return verifier