110 lines
3.6 KiB
Python
110 lines
3.6 KiB
Python
# MIT License
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#
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# Copyright (c) 2022 Mark Qvist / unsigned.io
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to deal
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# in the Software without restriction, including without limitation the rights
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# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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# copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in all
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# copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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# SOFTWARE.
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import os
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import time
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from RNS.Cryptography import HMAC
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from RNS.Cryptography import PKCS7
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from RNS.Cryptography.AES import AES_128_CBC
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class Fernet():
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"""
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This class provides a slightly modified implementation of the Fernet spec
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found at: https://github.com/fernet/spec/blob/master/Spec.md
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According to the spec, a Fernet token includes a one byte VERSION and
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eight byte TIMESTAMP field at the start of each token. These fields are
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not relevant to Reticulum. They are therefore stripped from this
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implementation, since they incur overhead and leak initiator metadata.
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"""
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FERNET_OVERHEAD = 48 # Bytes
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@staticmethod
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def generate_key():
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return os.urandom(32)
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def __init__(self, key = None):
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if key == None:
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raise ValueError("Token key cannot be None")
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if len(key) != 32:
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raise ValueError("Token key must be 32 bytes, not "+str(len(key)))
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self._signing_key = key[:16]
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self._encryption_key = key[16:]
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def verify_hmac(self, token):
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if len(token) <= 32:
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raise ValueError("Cannot verify HMAC on token of only "+str(len(token))+" bytes")
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else:
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received_hmac = token[-32:]
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expected_hmac = HMAC.new(self._signing_key, token[:-32]).digest()
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if received_hmac == expected_hmac:
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return True
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else:
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return False
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def encrypt(self, data = None):
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iv = os.urandom(16)
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current_time = int(time.time())
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if not isinstance(data, bytes):
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raise TypeError("Token plaintext input must be bytes")
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ciphertext = AES_128_CBC.encrypt(
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plaintext = PKCS7.pad(data),
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key = self._encryption_key,
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iv = iv,
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)
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signed_parts = iv+ciphertext
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return signed_parts + HMAC.new(self._signing_key, signed_parts).digest()
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def decrypt(self, token = None):
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if not isinstance(token, bytes):
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raise TypeError("Token must be bytes")
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if not self.verify_hmac(token):
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raise ValueError("Token HMAC was invalid")
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iv = token[:16]
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ciphertext = token[16:-32]
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try:
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plaintext = PKCS7.unpad(
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AES_128_CBC.decrypt(
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ciphertext,
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self._encryption_key,
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iv,
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)
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)
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return plaintext
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except Exception as e:
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raise ValueError("Could not decrypt token") |