server kinda works

6 files changed, 765 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..fabfb87
--- /dev/null
+++ b/.gitignore
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+/target
+/config.toml
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..350b44e
--- /dev/null
+++ b/Cargo.lock
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diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..ad34b07
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "offsite-vault"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+toml = "0.8.14"
+serde = { version = "1.0.203", features = ["derive"] }
+log = "0.4.21"
+env_logger = "0.11.3"
+anyhow = "1.0.86"
+clap = { version = "4.5.7", features = ["derive"] }
diff --git a/readme.md b/readme.md
new file mode 100644
index 0000000..b3c1929
--- /dev/null
+++ b/readme.md
@@ -0,0 +1,33 @@
+# online-offsite-backup (name to change)
+
+This tool provides a way to offer others a service for backing up important
+files automatically.
+
+Problem: Offsite backups could be as easy as a network filesystem - the problem
+is however that these usually implement deleting files aswell. In the case where
+a user's machine is comprimised by an attacker, these files could just be
+deleted in the same way they were created, defeating the advantages of an
+**offsite** backup.
+
+Solution: Implement a network "filesystem" that only supports non-destructive
+operations. Only implementing upload means that backups will accumulate on the
+server. This tool deletes backups after N newer backups (like a ring buffer). To
+prevent quick successive uploads as a means of deleting backups a cooldown for
+backup uploads is implemented.
+
+Intended Usage: This program is developed to be deployed on a number of servers
+that are not under your control like backing up data of your friends. In such a
+scenario, everyone in your friend group would run this software on their server
+and negotiate keys with every other one.
+
+Possible attacks: This software primarily protects against the exact case
+mentioned above especially when been attacked by automated malware on your
+machine. Your remote backups servers may still be vulnerable to social
+engineering and supply-chain attacks.
+
+Security: This software assumes security (and reliability) of the TCP
+connections it makes: You **must** implement protection on this level yourself.
+Backups are stored as-is on the remote server: If your backup requires it,
+encrypt it!
+
+## Usage
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..243c621
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,69 @@
+#![feature(iterator_try_collect)]
+#![feature(never_type)]
+pub mod server;
+
+use clap::{Parser, Subcommand};
+use serde::Deserialize;
+use server::server;
+use std::{fs::read_to_string, net::SocketAddr, path::PathBuf};
+
+pub type Serial = u64;
+
+#[derive(Parser)]
+struct Args {
+    config: PathBuf,
+    #[clap(subcommand)]
+    action: Action,
+}
+
+#[derive(Subcommand)]
+enum Action {
+    Daemon,
+    Restore { id: String, destination: PathBuf },
+    Backup { path: PathBuf },
+}
+
+#[derive(Deserialize)]
+pub struct Config {
+    storage: StorageConfig,
+    server: ServerConfig,
+    peer: Vec<PeerConfig>,
+}
+
+#[derive(Deserialize)]
+pub struct PeerConfig {
+    name: String,
+    address: SocketAddr,
+    shared_secret: String,
+}
+
+#[derive(Deserialize)]
+pub struct ServerConfig {
+    address: String,
+}
+
+#[derive(Deserialize)]
+pub struct StorageConfig {
+    root: PathBuf,
+    size: u64,
+    versions: usize,
+    upload_cooldown: u64,
+    download_cooldown: u64,
+    upload_speed: usize,
+    download_speed: usize,
+}
+
+fn main() -> anyhow::Result<()> {
+    env_logger::init_from_env("LOG");
+    let args = Args::parse();
+
+    let config = read_to_string(&args.config)?;
+    let config = toml::from_str::<Config>(&config)?;
+
+    match args.action {
+        Action::Daemon => server(config.into())?,
+        Action::Restore { id, destination } => todo!(),
+        Action::Backup { path } => todo!(),
+    }
+    Ok(())
+}
diff --git a/src/server.rs b/src/server.rs
new file mode 100644
index 0000000..30ed0c8
--- /dev/null
+++ b/src/server.rs
@@ -0,0 +1,228 @@
+use crate::{Config, PeerConfig, Serial};
+use anyhow::{anyhow, bail};
+use log::{error, info, warn};
+use serde::{Deserialize, Serialize};
+use std::{
+    fs::{create_dir_all, read_to_string, remove_file, File},
+    io::{copy, BufRead, BufReader, BufWriter, Read, Write},
+    net::{SocketAddr, TcpListener, TcpStream},
+    os::unix::fs::MetadataExt,
+    sync::{Arc, Mutex},
+    thread::spawn,
+    time::SystemTime,
+};
+
+pub fn server(config: Arc<Config>) -> anyhow::Result<!> {
+    let listener = TcpListener::bind(&config.server.address)?;
+    info!("listening on {}", listener.local_addr()?);
+    loop {
+        let Ok((sock, addr)) = listener.accept() else {
+            error!("could not accept connection");
+            continue;
+        };
+        info!("connection from {addr}");
+        let config = config.clone();
+        spawn(
+            move || match handle_connection_wrapper(config, sock, addr) {
+                Ok(()) => (),
+                Err(err) => {
+                    warn!("client error {addr}: {err:?}")
+                }
+            },
+        );
+    }
+}
+
+fn handle_connection_wrapper(
+    config: Arc<Config>,
+    sock: TcpStream,
+    addr: SocketAddr,
+) -> anyhow::Result<()> {
+    let mut rsock = BufReader::new(sock.try_clone()?);
+    let mut wsock = BufWriter::new(sock);
+    match handle_connection(config, &mut rsock, &mut wsock, addr) {
+        Ok(()) => Ok(()),
+        Err(e) => {
+            writeln!(wsock, "error,{e}")?;
+            wsock.flush()?;
+            Err(e)
+        }
+    }
+}
+fn handle_connection(
+    config: Arc<Config>,
+    rsock: &mut BufReader<TcpStream>,
+    wsock: &mut BufWriter<TcpStream>,
+    addr: SocketAddr,
+) -> anyhow::Result<()> {
+    let mut line = String::new();
+
+    rsock.by_ref().take(4096).read_line(&mut line)?;
+
+    let provided_secret = line.trim();
+    eprintln!("{:?}", provided_secret);
+    let Some(peer) = config
+        .peer
+        .iter()
+        .find(|p| p.shared_secret == provided_secret)
+    else {
+        bail!("invalid secret");
+    };
+
+    let peerdir = config.storage.root.join(&peer.name);
+    create_dir_all(&peerdir)?;
+
+    loop {
+        line.clear();
+        rsock.by_ref().take(4096).read_line(&mut line)?;
+        let mut toks = line.trim().split(",");
+        let command = toks.next().ok_or(anyhow!("command missing"))?;
+        eprintln!("{command:?}");
+        match command {
+            "quit" => break Ok(()),
+            "list" => {
+                let mut dir = peerdir
+                    .read_dir()?
+                    .map(|e| {
+                        let e = e?;
+                        Ok::<_, anyhow::Error>((
+                            e.metadata()?.mtime(),
+                            e.metadata()?.size(),
+                            e.file_name()
+                                .to_str()
+                                .unwrap()
+                                .to_string()
+                                .parse::<Serial>()?,
+                        ))
+                    })
+                    .try_collect::<Vec<_>>()?;
+                dir.sort_by_key(|(_, _, a)| *a);
+
+                for (m, s, p) in dir {
+                    writeln!(wsock, "{m}:{s}:{p}")?;
+                }
+                writeln!(wsock)?;
+                wsock.flush()?;
+            }
+            "upload" => {
+                let size = toks.next().ok_or(anyhow!("size missing"))?.parse::<u64>()?;
+                if size > config.storage.size {
+                    bail!("maximum size exceeded")
+                }
+
+                let serial = transact_user_state(&config, peer, |s| {
+                    if s.last_upload.elapsed().unwrap().as_secs() > config.storage.upload_cooldown {
+                        s.last_upload = SystemTime::now();
+                        s.serial += 1;
+                        Some(s.serial)
+                    } else {
+                        None
+                    }
+                })?
+                .ok_or(anyhow!("upload cooldown"))?;
+                writeln!(wsock, "ready")?;
+                wsock.flush()?;
+
+                while peerdir.read_dir()?.fold(0, |a, _| a + 1) > config.storage.versions {
+                    let mut dir = peerdir
+                        .read_dir()?
+                        .map(|e| {
+                            let e = e?;
+                            Ok::<_, anyhow::Error>(
+                                e.file_name()
+                                    .to_str()
+                                    .unwrap()
+                                    .to_string()
+                                    .parse::<Serial>()?,
+                            )
+                        })
+                        .try_collect::<Vec<_>>()?;
+                    dir.sort();
+                    let rem = dir[0];
+                    info!("removing serial={rem}");
+                    remove_file(peerdir.join(rem.to_string()))?;
+                }
+
+                info!("upload from {addr} size={size}");
+                let mut upload = rsock.get_ref().take(size);
+                let mut target =
+                    BufWriter::new(File::create_new(peerdir.join(serial.to_string()))?);
+
+                copy(&mut upload, &mut target)?; // TODO speed limit
+
+                info!("done {addr}");
+                writeln!(wsock, "done")?;
+                wsock.flush()?;
+            }
+            "download" => {
+                let serial = toks
+                    .next()
+                    .ok_or(anyhow!("serial missing"))?
+                    .parse::<Serial>()?;
+                let ok = transact_user_state(&config, peer, |s| {
+                    if s.last_download.elapsed().unwrap().as_secs()
+                        > config.storage.download_cooldown
+                    {
+                        s.last_download = SystemTime::now();
+                        true
+                    } else {
+                        false
+                    }
+                })?;
+                if !ok {
+                    bail!("download cooldown")
+                }
+
+                let source = File::open(peerdir.join(serial.to_string()))?;
+                let size = source.metadata()?.size();
+                let mut source = BufReader::new(source);
+
+                writeln!(wsock, "ready,{size}")?;
+                wsock.flush()?;
+                copy(&mut source, wsock)?; // TODO speed limit
+
+                writeln!(wsock, "done")?;
+                wsock.flush()?;
+            }
+            _ => bail!("unknown command"),
+        }
+    }
+}
+
+#[derive(Serialize, Deserialize)]
+struct PeerState {
+    last_upload: SystemTime,
+    last_download: SystemTime,
+    serial: Serial,
+}
+
+static USER_DB: Mutex<()> = Mutex::new(());
+fn transact_user_state<T>(
+    config: &Config,
+    peer: &PeerConfig,
+    update: impl FnOnce(&mut PeerState) -> T,
+) -> anyhow::Result<T> {
+    let _g = USER_DB
+        .lock()
+        .map_err(|_| anyhow!("user database locked"))?;
+
+    let conf_path = config.storage.root.join(&peer.name).with_extension("db");
+
+    let mut state = read_to_string(&conf_path)
+        .map(|s| toml::from_str(&s))
+        .unwrap_or_else(|_| {
+            Ok(PeerState {
+                last_download: SystemTime::UNIX_EPOCH,
+                last_upload: SystemTime::UNIX_EPOCH,
+                serial: 0,
+            })
+        })?;
+
+    let res = update(&mut state);
+    let ser_state = toml::to_string_pretty(&state)?;
+
+    File::create(conf_path)?.write_all(ser_state.as_bytes())?;
+
+    drop(_g);
+    Ok(res)
+}