Source code for thorn.utils.hmac

"""

    thorn.utils.hmac
    ================

    HMAC Message signing utilities.

"""
from __future__ import absolute_import, unicode_literals

import base64
import hashlib
import hmac
import random
import string

from .compat import bytes_if_py3, to_bytes

try:
    import itsdangerous
except ImportError:  # pragma: no cover
    itsdangerous = None  # noqa

# Some version of PyPy does not have hashlib.algorithms_available
allowed_algorithms = {
    'sha1', 'sha224', 'sha256', 'sha384', 'sha512',
}

punctuation = string.punctuation.replace('"', '').replace("'", '')


[docs]def get_digest(d): assert d.lower() in allowed_algorithms return getattr(hashlib, d.lower())
[docs]def sign(digest_method, key, message): return base64.b64encode(bytes_if_py3(hmac.new( to_bytes(key), to_bytes(message), digestmod=get_digest(digest_method)).digest()))
[docs]def verify(digest, digest_method, key, message): return hmac.compare_digest(sign(digest_method, key, message), digest)
[docs]def random_secret( length, chars=string.ascii_letters + string.digits + punctuation): return ''.join(random.choice(chars) for _ in range(length))
[docs]def compat_sign(digest_method, key, message): return itsdangerous.Signer( key, digest_method=get_digest(digest_method), ).get_signature(message)