################################################################################
# Copyright 2016 Google Inc.
#
# This software is licensed under the terms defined in the Widevine Master
# License Agreement. For a copy of this agreement, please contact
# widevine-licensing@google.com.
################################################################################

"""Utility functions for cryptography."""

from cryptography.hazmat import backends
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization
from cryptography.hazmat.primitives.asymmetric import padding


def VerifySignature(public_key, signature, data):
  hash_algorithm = hashes.SHA1()
  salt_len = 20

  key = serialization.load_der_public_key(
      public_key, backend=backends.default_backend())
  key.verify(signature, data,
             padding.PSS(padding.MGF1(hash_algorithm), salt_len),
             hash_algorithm)