def write(self, path, buf, offset, fh):
fullpath = self._full_path(path)
#compute the entire plaintext to be written to the file
#currently does not support writing less than the entire file
plaintext = buf
try:
f = open(fullpath, 'r')
data = f.read()
#prevent useless metadata files. should clean them on deletes / truncates
if len(data) > 0:
data = self.decrypt_with_metadata(path, data)
plaintext = data[:offset] + buf + data[(offset + len(buf)):]
f.close()
except IOError:
plaintext = buf
#encrypt and write the metadata file
filedata = encrypt(plaintext, self.encryption_key, self.signing_key)
padlength = padding_length(len(plaintext))
self.write_metadata_file(path, filedata, padlength)
#write the actual file. The first 80 bytes of filedata are the
#hex digest + the iv. The last "padlength" bytes are block padding
os.lseek(fh, 0, os.SEEK_SET)
bytes_written = os.write(fh, filedata[self.metadata_header_length:(-1*padlength)])
return min(len(buf), bytes_written)
def get_metadata(self, plain_data, enc_data):
padlength = padding_length(len(plain_data))
digest = enc_data[0:self.digest_size]
iv = enc_data[self.digest_size:self.digest_size+self.iv_size]
m_data = {
'digest': digest,
'iv': iv,
'padding': enc_data[(-1 * padlength):],
'pad_len': padlength
}
return m_data
def get_metadata(self, plain_data, enc_data):
padlength = padding_length(len(plain_data))
digest = enc_data[0:self.digest_size]
iv = enc_data[self.digest_size:self.digest_size + self.iv_size]
m_data = {
'digest': digest,
'iv': iv,
'padding': enc_data[(-1 * padlength):],
'pad_len': padlength
}
return m_data
