Attachments in encrypted rooms are not automatically decrypted

[manueldavid123]

Description

When I try to read a file uploaded to a private room, the byte representation appears encrypted. However, when I run it on a public room, I don't have that problem and I can read the file without problems.

Steps to Reproduce

Upload a txt file with any content (in this case, only one line with the text 'hola') to a private room. A skill with match_event(File) decorator will receive the event. When the method "get_file_bytes()" is called, it returns the content encrypted

Expected Functionality

The method get_file_bytes() should return the bytes representation of the file.

This method should return the data b'hola'

Experienced Functionality

The method get_file_bytes() returns the bytes representation of the file encrypted.

This method returns b'\xc6p\xa09'

Versions

• Opsdroid version: 0.28.0
• Python version: 3.9.6
• OS/Docker version: opsdroid/opsdroid:latest

Configuration File

Please include your version of the configuration file below.

connectors:
  matrix:
    # Required
    mxid: "user"
    password: "pass"
    rooms:
      'main': 'room'
    homeserver: "https://matrix.org"
    enable_encryption: True
    device_id: "device"
    store_path: /home/opsdroid/.keys/
    room_specific_nicks: False

databases:
  matrix:

Example Code

    @match_event(File)
    async def file_skill(self, event):
        try:
            data_in_bytes = await event.get_file_bytes()
            filename = event.name
            user = event.raw_event['sender']
            print (str(event.__dict__))

[manueldavid123]

After an intense search in other projects, I have found the solution to my problem.

When a file is uploaded to a private room, the content of that file is encrypted. Once downloaded, it is necessary to decrypt it using external libraries.

Here I show an example code to decrypt files from Matrix:

    @match_event(File)
    async def file_skill(self, event):
        try:
            data_in_bytes = await event.get_file_bytes()
            content = event.raw_event['content']

            if ('file' in content):
                # The file is encoded
                file_data = event.raw_event['content']['file']
                
                data_in_bytes = crypto.attachments.decrypt_attachment(
                                        data_in_bytes,
                                        file_data["key"]["k"],
                                        file_data["hashes"]["sha256"],
                                        file_data["iv"],
                                    )
            	

            return data_in_bytes.decode('utf-8')
        except BaseException as e:
        	logging.error(e)

        return None

In my opinion, this information should be added to the connectors documentation.

If anyone has any comments, fell free to post it. Otherwise, this issue can be closed.

[Cadair]

Thanks for figuring this one out and providing the code to decrypt the attachment. We should definitely add this to the connector so it's transparent to the skills.

[u7498708]

Hi there, was wondering if this has been done and if not if I could be assigned to it? I am a first time contributor so I might ask a few questions about it if I get stuck. Thanks and looking forward to hearing back!

[u7498708]

@Cadair just in case I needed to mention you :)