# fsdecrypt

Decryptor and extractor for SEGA arcade filesystem containers (fscrypt format). Works on Windows and Linux, no admin privileges required.

## Installation

Requires [Rust](https://www.rust-lang.org/tools/install).

```bash
cargo build --release
```

The binary will be at `target/release/fsdecrypt` (or `fsdecrypt.exe` on Windows).

## Usage

```bash
fsdecrypt <FILES>...
```

### Examples

```bash
# Extract a game APP container
fsdecrypt ABCD_1.00.00_20240101120000_0.app

# Extract an OPTION/DLC container
fsdecrypt ABCD_A001_20240101120000_0.opt

# Extract multiple files at once
fsdecrypt game_v1.app game_v2.app extras.opt

# Decrypt only (outputs raw .ntfs/.exfat image, no extraction)
fsdecrypt --no-extract ABCD_1.00.00_20240101120000_0.app
```

### Delta Updates

Games often ship incremental updates as a separate `.app` file. Just pass the update file — fsdecrypt will automatically find the base in the same folder and merge them:

```bash
fsdecrypt ABCD_1.01.00_20240215143000_1_1.00.00.app
```

You can also pass both explicitly:

```bash
fsdecrypt ABCD_1.00.00_20240101120000_0.app ABCD_1.01.00_20240215143000_1_1.00.00.app
```

The output folder is named after the input file (e.g. `ABCD_1.01.00_20240215143000_1_1.00.00/`).

## Windows Right-Click Menu

Two batch files add an **"Unpack with fsdecrypt"** entry (with an unpack icon)
to the right-click menu of `.app` and `.opt` files:

- **`install-context-menu.bat`** — install the menu entry
- **`uninstall-context-menu.bat`** — remove it

Just double-click `install-context-menu.bat`. No administrator rights are
needed — it installs under the current user only (`HKCU`) and leaves the normal
double-click association untouched. Right-clicking a file then runs the full
extraction and keeps the console window open until you press a key.

`install-context-menu.bat` finds `fsdecrypt.exe` automatically when run from the
repo root (it looks in `target\release` then `target\debug`) or when placed next
to the binary. The icon is taken from `assets\fsdecrypt.ico` (or `fsdecrypt.ico`
beside the script). The menu stores the absolute path it found, so re-run it if
you move the exe.

> On Windows 11 the entry appears under **Show more options** (the classic menu).

## External Key Files

For games not in the built-in key database, place a file named `{GAME_ID}.bin` in the working directory:

- **16 bytes** for key only (IV derived automatically)
- **32 bytes** for key + IV

## Testing

Tests run locally (there is no hosted CI). The unit tests are plain `cargo test`;
the Linux `x86_64-musl` release target is exercised via Docker when you need it.

```bash
cargo test            # unit tests (IV derivation, timestamp decoding, key lookup)
scripts/test.sh       # native tests + smoke test, then the same in a musl container
scripts/test.sh --no-docker   # skip the Docker/Linux step
```

`scripts/test.sh` uses the [`clux/muslrust`](https://hub.docker.com/r/clux/muslrust)
image to build and test the static Linux binary — the same way release artifacts
are produced — so both targets can be validated from any host.

### End-to-end fixtures

The `tests/e2e.rs` test decrypts real containers placed in a `fixtures/`
directory at the repo root and checks that each extracts successfully. That
folder is git-ignored — the proprietary sample containers are never committed —
and the test is a no-op when it is empty, so just drop a few `.app`/`.opt` files
in `fixtures/` and run `cargo test` (or `scripts/test.sh`) to exercise the full
decrypt-and-extract path.

## License

[BSD Zero Clause License](LICENSE) (0BSD)