64 lines
2.7 KiB
Python
64 lines
2.7 KiB
Python
|
"""The cryptography backend for the1024.club. Here lie dragons.
|
||
|
|
|
||
|
|
Everything will be explained to the best of my ability, but please understand
|
||
|
|
that even I am lost about how most of these functions work.
|
||
|
|
|
||
|
|
At the moment, we only support RSA public keys in the backend. This is because
|
||
|
|
finding the right parameters for signature verification is like shoving bamboo
|
||
|
|
under my fingernails (that is to say, extremely painful), and I don't want to
|
||
|
|
do it any more than necessary. If you want another public key format to be
|
||
|
|
implemented, figure it out your own damn self and submit a pull request.
|
||
|
|
|
||
|
|
Sincerely yours,
|
||
|
|
Robert Miles
|
||
|
|
~khuxkm
|
||
|
|
|
||
|
|
P.S. This code (at least, the parts written by me) is licensed under MIT, in
|
||
|
|
addition to whatever license the rest of the1024.club's code is licensed under."""
|
||
|
|
from cryptography.hazmat.backends import default_backend
|
||
|
|
from cryptography.hazmat.primitives.serialization import load_pem_public_key
|
||
|
|
from cryptography.hazmat.primitives.asymmetric import padding, rsa
|
||
|
|
from cryptography.hazmat.primitives.hashes import SHA256
|
||
|
|
from cryptography.exceptions import InvalidSignature
|
||
|
|
"""Key formats we support. For a class to be in here, it must have a corresponding isinstance() check in verify_signature."""
|
||
|
|
SUPPORTED_PUBLIC_KEY_FORMATS = [rsa.RSAPublicKey]
|
||
|
|
|
||
|
|
|
||
|
|
class UnknownKeyFormat(Exception):
|
||
|
|
pass
|
||
|
|
|
||
|
|
|
||
|
|
def verify_signature(block_data, signature, pubkey):
|
||
|
|
"""Verifies a signature `signature`, given data `block_data` and a public key `pubkey`.
|
||
|
|
|
||
|
|
To generate a signature that can be verified by this function, use:
|
||
|
|
$ openssl dgst -sha256 -sign private.key -sigopt rsa_padding_mode:pss -sigopt rsa_pss_saltlen=32 -out <signature> <file>"""
|
||
|
|
# load the public key
|
||
|
|
public_key = load_pem_public_key(pubkey, backend=default_backend())
|
||
|
|
# is it an RSA public key?
|
||
|
|
if isinstance(public_key, rsa.RSAPublicKey):
|
||
|
|
try:
|
||
|
|
# public_key.verify raises InvalidSignature on verification failure, so call it
|
||
|
|
public_key.verify(
|
||
|
|
signature,
|
||
|
|
block_data,
|
||
|
|
# PSS padding, with SHA256-digest MGF-1 and a salt length of 32
|
||
|
|
padding.PSS(padding.MGF1(SHA256()), 32),
|
||
|
|
# SHA256 digest
|
||
|
|
SHA256())
|
||
|
|
return True
|
||
|
|
except InvalidSignature:
|
||
|
|
return False
|
||
|
|
raise UnknownKeyFormat(type(public_key).__name__)
|
||
|
|
|
||
|
|
|
||
|
|
def supports(pubkey):
|
||
|
|
"""Returns whether public key `pubkey` is of a supported type."""
|
||
|
|
# load the public key
|
||
|
|
public_key = load_pem_public_key(pubkey, backend=default_backend())
|
||
|
|
# if public_key is an instance of any of SUPPORTED_PUBLIC_KEY_FORMATS, we support it
|
||
|
|
return any([
|
||
|
|
isinstance(public_key, format)
|
||
|
|
for format in SUPPORTED_PUBLIC_KEY_FORMATS
|
||
|
|
])
|