# RencFs

An encrypted file system that mounts with FUSE on Linux. It can be used to create encrypted directories.

You can then safely backup the encrypted folder on an untrusted server without worrying about the data being exposed.\
You can also store it in any cloud storage like Google Drive, Dropbox, etc. and have it synced across multiple devices.

[![rencfs-bin](https://img.shields.io/aur/version/rencfs-bin?color=1793d1&label=rencfs-bin&logo=arch-linux)](https://aur.archlinux.org/packages/rencfs-bin/)
[![crates.io](https://img.shields.io/crates/v/rencfs.svg)](https://crates.io/crates/rencfs)
[![docs.rs](https://img.shields.io/docsrs/rencfs?label=docs.rs)](https://docs.rs/rencfs/)
[![check](https://github.com/radumarias/rencfs/actions/workflows/test.yml/badge.svg)](https://github.com/radumarias/rencfs/actions/workflows/check.yml)
[![Discord](https://img.shields.io/discord/1236855443486277653)](https://discord.com/channels/1236855443486277653/1236855448515252306)
[![](https://img.shields.io/badge/zulip-join_chat-brightgreen.svg)](https://rencfs.zulipchat.com)

# Functionality

I keeps all encrypted data and master encryption key in a dedicated directory with files structured on inodes (with meta
info), files for binary content and directories with files/directories entries. All data, metadata and also filenames
are encrypted. For new files it generates inode number randomly in `u64` space so it reduces the chance of conflicts
when used offline and synced later.

Password is collected from CLI and it's saved in OS keyring while app is running. This is because of safety reasons we
clear the password from memory on inactivity and we reload it again from keyring just when needed.

Master encryption key is also encrypted with another key derived from the password. This gives the ability to change the
password without re-encrypting all data, we just re-encrypt the master key.

# Stack

- it's fully async built upon [tokio](https://crates.io/crates/tokio) and [fuse3](https://crates.io/crates/fuse3)
- [ring](https://crates.io/crates/ring) for encryption and [argon2](https://crates.io/crates/argon2) for key derivation
  function (creating key used to encrypt master encryption key from password)
- [rand_chacha](https://crates.io/crates/rand_chacha) for random generators
- [secrecy](https://crates.io/crates/secrecy) for keeping pass and encryption keys safe in memory and zeroing them when
  not used. It keeps encryption keys in memory only while being used and when not active it will release and zeroing
  them from memory
- password can be saved in OS keyring using [keyring](https://crates.io/crates/keyring)
- [tracing](https://crates.io/crates/tracing) for logs

# Usage

You can use it as a command line tool to mount an encrypted file system, or directly using the library to build your own
binary (for library, you can follow the [documentation](https://docs.rs/rencfs/latest/rencfs/)).

## Command Line Tool

To use the encrypted file system, you need to have FUSE installed on your system. You can install it by running the
following command (or based on your distribution)

Arch

```bash
sudo pacman -Syu && sudo pacman -S fuse3
```

Ubuntu

```bash
sudo apt-get update && sudo apt-get -y install fuse3
```

### Install from AUR

You can install the encrypted file system binary using the following command

```bash
yay -Syu && yay -S rencfs
```

### Install with cargo

You can install the encrypted file system binary using the following command

```bash
cargo install rencfs
```

A basic example of how to use the encrypted file system is shown below

```
rencfs mount --mount-point MOUNT_POINT --data-dir DATA_DIR --tmp-dir TMP_DIR

```

- `MOUNT_POINT` act as a client, and mount FUSE at given path
- `DATA_DIR` where to store the encrypted data
- `TMP_DIR` where keep temp data. This should be in a different directory than `DATA_DIR` as you don't want to sync this
  with the sync provider. But it needs to be on the same filesystem as the data-dir

It will prompt you to enter a password to encrypt/decrypt the data.

### Change Password

The encryption key is stored in a file and encrypted with a key derived from the password.
This offers the possibility to change the password without needing to decrypt and re-encrypt the whole data.
This is done by decrypting the key with the old password and re-encrypting it with the new password.

To change the password, you can run the following command

```bash
rencfs change-password --data-dir DATA_DIR 
```

`DATA_DIR` where the encrypted data is stored

It will prompt you to enter the old password and then the new password.

### Encryption info

You can specify the encryption algorithm adding this argument to the command line

```bash
--cipher CIPHER
```

Where `CIPHER` is the encryption algorithm.\
You can check the available ciphers with `rencfs --help`.

Default values are `ChaCha20` and `600_000` respectively.

### Log level

You can specify the log level adding the `--log-level` argument to the command line. Possible
values: `TRACE`, `DEBUG`, `INFO` (default), `WARN`, `ERROR`.

```bash
rencfs --log-level LEVEL ...
```

## Start it in docker

Get the image

```bash
docker pull xorio42/rencfs
```

Start a container to set up mount in it

`docker run -it --device /dev/fuse --cap-add SYS_ADMIN --security-opt apparmor:unconfined xorio42/rencfs:latest /bin/sh`

In the container create mount and data directories

`mkdir fsmnt && mkdir fsdata`

Start `rencfs`

`rencfs --mount-point fsmnt --data-dir fsdata`

Enter a password for encryption.

Get the container ID

`docker ps`

In another terminal attach to running container with the above ID

`docker exec -it <ID> /bin/sh`

From here you can play with it by creating files in `fsmnt` directory

```
cd fsmnt
mkdir 1
ls
echo "test" > 1/test
cat 1/test
```

# Building from source

## Getting the sources

```bash
git@github.com:radumarias/rencfs.git
````

## Dependencies

### Rust

To build from source, you need to have Rust installed, you can see more details on how to install
it [here](https://www.rust-lang.org/tools/install).

```bash
curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
````

Accordingly, it is customary for Rust developers to include this directory in their `PATH` environment variable.
During installation `rustup` will attempt to configure the `PATH`. Because of differences between platforms, command
shells,
and bugs in `rustup`, the modifications to `PATH` may not take effect until the console is restarted, or the user is
logged out, or it may not succeed at all.

If, after installation, running `rustc --version` in the console fails, this is the most likely reason.
In that case please add it to the `PATH` manually.

### Other dependencies

Also these deps are required (or based on your distribution):

Arch

```bash
sudo pacman -Syu && sudo pacman -S fuse3 base-devel
```

Ubuntu

```bash
sudo apt-get update && sudo apt-get install fuse3 build-essential
```

## Build for debug

```bash
cargo build
```

## Build release

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

## Run

```bash
cargo run -- --mount-point MOUNT_POINT --data-dir DATA_DIR
```

## Developing inside a Container

See here how to configure for [VsCode](https://code.visualstudio.com/docs/devcontainers/containers)\
And here for [RustRover](https://www.jetbrains.com/help/rust/connect-to-devcontainer.html)

You can use the `.devcontainer` directory from the project to start a container with all the necessary tools to build
and run the app.

# Future

- Plan is to implement it also on macOS and Windows
- A systemd service is being worked on [rencfs-daemon](https://github.com/radumarias/rencfs-daemon)
- A GUI is on the way [rencfs_desktop](https://github.com/radumarias/rencfs_desktop)
- Mobile apps for Android and iOS are on the way

# Contribution

Feel free to fork it, change and use it in any way that you want. If you build something interesting and feel like
sharing pull requests are always apporeciated.

# Security

- Safety on process kill (or crash): all writes to encrypted content is done in a tmp file and then using `mv` to move
  to destination. the `mv` operation is atomic as it's using `rename()` which is atomic as per specs,
  see [here](https://pubs.opengroup.org/onlinepubs/009695399/functions/rename.html) `That specification requires that the action of the function be atomic.`
- Phantom reads: reading older content from a file, this is not possible. While writing, data is kept in a buffer and
  tmp file and on releasing the file handle we write the new content to the file (as per above the tmp file is moved
  into place with `mv`). After that we reset all opened readers so any reads after that will pick up the new content\
  One problem that may occur is if we do a truncate we change the content of the file but the process is killed before
  we write the metadata with the new filesize. In this case next time we mount the system we are still seeing the old
  filesize but the content of the file could be bigger, and we read until the old size offset, se we would not pick up
  the new zeros bytes written on truncating by increasing the size. If content is smaller the read would stop and
  end-of-file of the actual content so this would not be such a big issue
- What kind of metadata does it leak: close to none. The filename, actual file size and other file attrs (times,
  permissions, other flags) are kept encrypted. What it could possible leak is the following
    - If a directory has children we keep those children in a directory with name as inode number with encrypted names
      of children as files in it. So we could see how many children a directory has, but we can't identify that actual
      directory name, we can just see it's inode number (internal representation like an id for each file) and we cannot
      see the actual filenames of directory or children. Also we cannot identify which file content correspond to a
      directory child
    - Each file content is saved in a separate file so we could see the size of the encrypted content, but not the
      actual filesize
    - We can also see the last time the file was accessed
- It's always recommended to use encrypted disks for at least your sensitive data, this project is not a replacement for
  that
- In order to reduce the risk of encryption key to be exposed from memory it's recommended to disable mem dumps on the
  OS level. Please see [here](https://www.cyberciti.biz/faq/disable-core-dumps-in-linux-with-systemd-sysctl/) how to do
  it on Linux
- Cold boot attacks: in order to reduce the risk of this we keep the encryption key in memory just as long as we really
  need it to encrypt/decrypt data and we are zeroing it after that. We also remove it from memory after a period of
  inactivity
- Please note that this project is not audited by any security expert. It's built with security in mind and tries to
  follow all the best practices, but it's not guaranteed to be secure
- **Also please backup your data, the project is still in development and there might be bugs that can lead to data loss
  **

# Considerations

- Please note, this project doesn't try to reinvent the wheel or be better than already proven implementations
- This project doesn't want to be a replacement in any way of already proven file encryption solutions. If you really
  want close to bullet proof solutions than maybe this is not the ideal one for you. But is trying to offer a simple use
  of an ecryption solution that should be used taking into consideration all the security concerns from above
- It started as a learning project of Rust programming language and I feel like keep building more on it
- It's a fairly simple and standard implementation that tries to respect all security standards, use safe libs and
  ciphers in the implementation so that it can be extended from this. Indeed it doesn't have the maturity yet to "fight"
  other well known implementations but it can be a project from which others can learn or build upon or why not for some
  to actually use it keeping in mind all the above
