inv_sig_helper/README.md

# inv_sig_helper

`inv_sig_helper` is a Rust service that decrypts YouTube signatures and manages player information. It offers a TCP/Unix socket interface for signature decryption and related operations.

## Features

- Decrypt YouTube `n` and `s` signatures
- Fetch and update YouTube player data
- Provide signature timestamps and player status
- Efficient signature decryption with multi-threaded JavaScript execution

## Run with Docker (recommended method)

A Dockerfile is included for containerized deployment.

And an official Docker image is available at `quay.io/invidious/inv-sig-helper`: https://quay.io/repository/invidious/inv-sig-helper

### Production

TODO: Follow the official documentation.

### Development

Run the project using docker compose:

```
docker compose up -d
```

Or you can run it manually but not recommended since you won't lock down the container from potential code execution from Google:

1. Build the image:

   ```
   docker build -t inv_sig_helper .
   ```

2. Run the container:

   ```
   docker run -p 127.0.0.1:12999:12999 inv_sig_helper
   ```

## Building and Running without Docker

### Prerequisites

- Rust 1.77 or later
- Cargo
- Patch
- openssl-devel

### Building

1. Clone the repository and navigate to the project directory:

   ```
   git clone https://github.com/iv-org/inv_sig_helper.git
   cd inv_sig_helper
   ```

2. Build the project:

   ```
   cargo build --release
   ```

### Running

#### Warning

We recommend running sig_helper inside a locked down environment like an LXC container or a systemd service where only the strict necessary is allowed.

No guide outside of Docker have been written for this but feel free to send your contribution.

This services runs untrusted code directly from Google.

#### Instructions

The service can run in Unix socket mode (default) or TCP mode:

1. Unix socket mode:

   ```
   ./target/release/inv_sig_helper_rust
   ```

   This creates a Unix socket at `/tmp/inv_sig_helper.sock`.

2. TCP mode:

   ```
   ./target/release/inv_sig_helper_rust --tcp [IP:PORT]
   ```

   If no IP:PORT is given, it defaults to `127.0.0.1:12999`.


## Protocol Format

All data-types bigger than 1 byte are stored in network endian (big-endian) unless stated otherwise.

### Request Base
| Name      | Size (bytes) | Description                          |
|-----------|--------------|--------------------------------------|
|opcode     | 1            | The operation code to perform, A list of operations currently supported (and their data) can be found in the **Operations** chapter |
|request_id | 4            | The ID for the current request, Used to distinguish responses in the current connection |

The data afterwards depends on the supplied opcode, Please consult the **Operations** chapter for more information.

### Response Base
| Name       | Size (bytes) | Description                           |
|------------|--------------|---------------------------------------|
|request_id  | 4            | The ID for the request that this response is meant for |
|size        | 4            | Size of the response (excluding size of request id)|

The data afterwards depends on the supplied opcode, Please consult the **Operations** chapter for more information.

### Operations
#### `FORCE_UPDATE` (0x00)
Forces the server to re-fetch the YouTube player, and extract the necessary components from it (`nsig` function code, `sig` function code, signature timestamp).

##### Request
*No additional data required*

##### Response
| Name | Size (bytes) | Description |
|------|--------------|-------------|
|status| 2            | The status code of the request: `0xF44F` if successful, `0xFFFF` if no updating is required (YouTube's player ID is equal to the server's current player ID), `0x0000` if an error occurred |

#### `DECRYPT_N_SIGNATURE` (0x01)
Decrypt a provided `n` signature using the server's current `nsig` function code, and return the result (or an error).

##### Request
| Name | Size (bytes) | Description                         |
|------|--------------|-------------------------------------|
|size  | 2            | The size of the encrypted signature |
|string| *`size`*     | The encrypted signature             |

##### Response
| Name | Size (bytes) | Description                                                      |
|------|--------------|------------------------------------------------------------------|
|size  | 2            | The size of the decrypted signature, `0x0000` if an error occurred |
|string| *`size`*     | The decrypted signature                                          |

#### `DECRYPT_SIGNATURE` (0x02)
Decrypt a provided `s` signature using the server's current `sig` function code, and return the result (or an error).

##### Request
| Name | Size (bytes) | Description                         |
|------|--------------|-------------------------------------|
|size  | 2            | The size of the encrypted signature |
|string| *`size`*     | The encrypted signature             |

##### Response
| Name | Size (bytes) | Description                                                      |
|------|--------------|------------------------------------------------------------------|
|size  | 2            | The size of the decrypted signature, `0x0000` if an error occurred |
|string| *`size`*     | The decrypted signature                                          |

#### `GET_SIGNATURE_TIMESTAMP` (0x03)
Get the signature timestamp from the server's current player, and return it in the form of a 64-bit integer. If there's no player, it will return 0 in the `timestamp` (Please check with `PLAYER_STATUS` if the server has a player)

##### Request
No additional data required

##### Response
| Name    | Size (bytes) | Description                                              |
|---------|--------------|----------------------------------------------------------|
|timestamp| 8            | The signature timestamp from the server's current player |

#### `PLAYER_STATUS` (0x04)
Get the server's information about the current player.

##### Request
No additional data required

##### Response

| Name     | Size (bytes) | Description |
|----------|--------------|-------------|
|has_player| 1            | If the server has a player, this variable will be `0xFF`. or else, it will be `0x00`|
|player_id | 4            | The server's current player ID. If the server has no player, this will always be `0x00000000`|

#### `PLAYER_UPDATE_TIMESTAMP` (0x05)
Get the time of the last player update, The time is represented as seconds since the last update

##### Request
No additional data required

##### Response

| Name     | Size (bytes) | Description |
|----------|--------------|-------------|
|timestamp | 8            | Seconds since the last player update |

## License

This project is open source under the AGPL-3.0 license.