[Python] Transparent filesystem in pyfuse with encryption and compression

I'm trying to make a simple transparent filesystem in fuse. I'm using this guide as a basis. This code works perfectly. I'm trying to modify it so that it compresses and then encrypts as well.

So far I have:

from Crypto.Cipher import AES
from Crypto.Util.Padding import pad, unpad

AES_KEY = b"thisisaverysecretkey1234"
AES_IV = b"thisisaverysecre"

def encrypt_data(self, data):
cipher = AES.new(AES_KEY, AES.MODE_CBC, AES_IV)
return cipher.encrypt(pad(data, AES.block_size))

def decrypt_data(self, data):
cipher = AES.new(AES_KEY, AES.MODE_CBC, AES_IV)
return unpad(cipher.decrypt(data), AES.block_size)


And I modified the read and write methods like so:

def read(self, path, size, offset, fh):
full_path = self._get_file_path(path)
os.lseek(fh, offset, os.SEEK_SET)
encrypted_data = os.read(fh, size)

# Decrypt the data before returning it
return decrypt_data(encrypted_data)

def write(self, path, buf, offset, fh):
full_path = self._get_file_path(path)
os.lseek(fh, offset, os.SEEK_SET)

# Encrypt data before writing it
encrypted_data = self._encrypt_data(buf)

return os.write(encrypted_data)


However, I keep getting the error:

fuse: wrote too many bytes


I can't seem to write encrypted files properly (I haven't even compressed/decompressed before applying encryption).

This is just a side project to test out my own compression/encryption scheme, and I'm using aes and zlib as placeholders.

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