How can I select a stream as the output of a decrypt_file operation in gnupg?
The docs and the code seem to suggest this is not possible. If I am correct (see below), what workarounds are possible?
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The documentation seems to suggest it is not possible:
decrypt_file(filename, always_trust=False, passphrase=None, output=None)¶
with "output (str) – A filename to write the decrypted output to."
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Opening up the code, I see:
def decrypt_file(self, file, always_trust=False, passphrase=None,
output=None, extra_args=None):
args = ["--decrypt"]
if output: # write the output to a file with the specified name
self.set_output_without_confirmation(args, output)
if always_trust: # pragma: no cover
args.append("--always-trust")
if extra_args:
args.extend(extra_args)
result = self.result_map['crypt'](self)
self._handle_io(args, file, result, passphrase, binary=True)
logger.debug('decrypt result: %r', result.data)
return result
which points to set_output_without_confirmation, confirming the idea is that you pass a string filename:
def set_output_without_confirmation(self, args, output):
"If writing to a file which exists, avoid a confirmation message."
if os.path.exists(output):
# We need to avoid an overwrite confirmation message
args.extend(['--yes'])
args.extend(['--output', no_quote(output)])
To output the decrypted data to a variable use decrypt instead of decrypt_file, as shown here in the "Decrypt a string" paragraph.
So the original code:
status = gpg.decrypt_file(input_file, passphrase='my_passphrase', output='my_output_file')
is substituted by:
decrypted_data = gpg.decrypt(input_file.read(), passphrase='my_passphrase')
# decrypted_data.data contains the data
decrypted_stream = io.BytesIO(decrypted_data.data)
# this is py3, in py2 BytesIO is imported from BytesIO
As an example for the specific use case for csv data, building on this SO post, you could then do:
my_df = pandas.read_csv(decrypted_stream)